RECORD OF DECISION - United States Environmental ... · RECORD OF DECISION ... 12.6.3 Soil...
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION 6
RECORD OF DECISION
GRANTS CHLORINATED SOLVENTS PLUME SITE
Grants, New Mexico
CERCLIS ID # NM007271768
June 30, 2006
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
CONTENTS III
Contents
Part Page 1 THE DECLARATION.................................................................................................. 1-1 1.0 Site Name and Location.................................................................................. 1-1 2.0 Statement of Basis and Purpose..................................................................... 1-1 3.0 Assessment of the Site..................................................................................... 1-2 4.0 Description of the Selected Remedy ............................................................. 1-2 4.1 Institutional Controls .......................................................................... 1-4 4.2 Contingency Remedy.......................................................................... 1-5 5.0 Statutory Determinations ............................................................................... 1-5 6.0 ROD Data Certification Checklist ................................................................. 1-6 7.0 Authorizing Signature .................................................................................... 1-7 Concurrence Page, Record of Decision......................................................... 1-9 2 THE DECISION SUMMARY..................................................................................... 2-1 8.0 Site Name, Location, and Description .......................................................... 2-1 9.0 Site History of Enforcement Activities ......................................................... 2-2 9.1 History of Site Activities..................................................................... 2-2 9.2 History of Federal and State Investigations..................................... 2-4 9.2.1 Site Investigation Report ...................................................... 2-4 9.2.2 Rio San Jose Hyporheic Zone Sampling............................. 2-4 9.2.3 Allsup’s 200 Secondary Investigation Report.................... 2-5 9.2.4 EPA’s Remedial Investigation ............................................. 2-7 9.2.5 National Remedy Review Board Review........................... 2-7 9.3 History of CERCLA Enforcement Activities ................................... 2-8 10.0 Community Participation............................................................................... 2-8 10.1 Community Meetings ......................................................................... 2-8 10.2 Public Meeting for the Proposed Plan .............................................. 2-9 10.3 Technical Assistance Grant .............................................................. 2-10 10.4 Fact Sheets........................................................................................... 2-10 10.5 Local Site Repository......................................................................... 2-10 11.0 Scope and Role of Response Action............................................................ 2-10 12.0 Site Characteristics......................................................................................... 2-11 12.1 Overview of the Site .......................................................................... 2-11 12.2 Site Geology........................................................................................ 2-12 12.3 Site Hydrogeology............................................................................. 2-13 12.4 Sampling Strategy.............................................................................. 2-13 12.5 Conceptual Site Model...................................................................... 2-14
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
CONTENTS IV
Contents (continued)
Part Page 12.6 Nature and Extent of Soil Contamination...................................... 2-15 12.6.1 Soil Contamination at Holiday Cleaners.......................... 2-15 12.6.2 Soil Contamination at Abandoned Dry Cleaners............ 2-16 12.6.3 Soil Contamination at R&L Laundry ................................ 2-16 12.6.4 Soil Contamination at Former Holiday Cleaners............ 2-17 12.6.5 Soil Contamination at Former MST&T Company Maintenance Yard................................................................ 2-17 12.6.6 Soil Contamination at Work Shed..................................... 2-17 12.7 Nature and Extent of Ground Water Contamination................... 2-17 12.8 Nature and Extent of Soil Vapor Contamination.......................... 2-20 12.9 Nature and Extent of Indoor Air Contamination.......................... 2-20 12.10 Potential Routes of Contaminant Migration.................................. 2-21 12.10.1 Infiltration............................................................................. 2-21 12.10.2 DNAPL Migration ............................................................... 2-21 12.10.3 Soil Vapor and Vapor Intrusion ........................................ 2-22 12.10.4 Aqueous-Phase Transport .................................................. 2-23 12.10.5 Potential Routes of Human Exposure............................... 2-23 12.11 Ground Water Flow and Transport Modeling .............................. 2-25 13.0 Current and Potential Future Land and Resource Uses .......................... 2-26 13.1 Current and Potential Future Land Uses ....................................... 2-26 13.2 Current and Potential Future Ground Water Uses....................... 2-26 14.0 Summary of Site Risks .................................................................................. 2-27 14.1 Summary of Human Health Risk Assessment .............................. 2-27 14.1.1 Identification of Chemicals of Concern ............................ 2-28 14.1.2 Exposure Assessment.......................................................... 2-31 14.1.3 Toxicity Assessment ............................................................ 2-32 14.1.4 Risk Characterization.......................................................... 2-33 14.1.5 Uncertainties......................................................................... 2-35 14.2 Ecological Risk Assessment.............................................................. 2-38 14.3 Basis for Remedial Action ................................................................ 2-38 15.0 Remedial Action Objectives ......................................................................... 2-39 15.1 Remedial Action Objectives for Ground Water ............................ 2-39 15.2 Remedial Action Objectives for Soil................................................ 2-40 15.3 Remedial Action Objectives for Vapor Intrusion.......................... 2-40 15.4 Basis and Rationale for Remedial Action Objectives.................... 2-40 15.5 Risks Addressed by the Remedial Action Objectives................... 2-41
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CONTENTS V
Contents (continued)
Part Page 16.0 Description of Alternatives .......................................................................... 2-42 16.1 Common Elements of Each Remedial Component....................... 2-43 16.1.1 Preliminary Design Field Investigation............................ 2-44 16.1.2 Ground Water Monitoring Program................................. 2-45 16.1.3 Five-Year Reviews ............................................................... 2-45 16.1.4 Institutional Controls .......................................................... 2-45 16.2 Distinguishing Features of Each Alternative................................. 2-46 16.2.1 Indoor Air Alternatives....................................................... 2-46 16.2.2 Source Area Alternatives.................................................... 2-48 16.2.3 Shallow Plume Core and Hot Spot Alternatives............. 2-54 16.2.4 Shallow Plume Periphery Alternatives ............................ 2-59 16.2.5 Deeper Ground Water Alternatives.................................. 2-65 16.3 Other Common Elements and Distinguishing Features Of Each Alternative ........................................................................... 2-70
16.3.1 Key Applicable or Relevant and Appropriate Requirements ....................................................................... 2-70
16.3.2 Long-Term Reliability of the Remedy .............................. 2-71 16.3.3 Quantities of Untreated Wastes......................................... 2-71 16.3.4 Uses of Presumptive Remedies.......................................... 2-72 16.4 Expected Outcomes of Each Alternative........................................ 2-73 17.0 Comparative Analysis of Alternatives ....................................................... 2-73 17.1 Overall Protection of Human Health and the Environment ....... 2-74 17.1.1 Indoor Air (Vapor Intrusion Mitigation).......................... 2-75 17.1.2 Source Area Treatment ....................................................... 2-75 17.1.3 Shallow Ground Water Plume Core and Hot Spot Treatment.............................................................................. 2-76 17.1.4 Shallow Ground Water Periphery..................................... 2-77 17.1.5 Deeper Ground Water......................................................... 2-79 17.2 Compliance with ARARs ................................................................. 2-80 17.3 Long-Term Effectiveness and Permanence.................................... 2-80 17.3.1 Magnitude of Residual Risk............................................... 2-81 17.3.2 Adequacy and Reliability of Controls............................... 2-86 17.4 Reduction of Toxicity, Mobility, and Volume ............................... 2-90 17.4.1 Treatment Process Used and Materials Treated.............. 2-90 17.4.2 Amount of Hazardous Materials Destroyed or Treated.............................................................................. 2-92 17.4.3 Degree of Expected Reductions in Toxicity, Mobility, and Volume ......................................................... 2-93 17.4.4 Type of Residuals Remaining After Treatment............... 2-95
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CONTENTS VI
Contents (continued)
Part Page 17.5 Short-Term Effectiveness.................................................................. 2-97 17.5.1 Protection of Community During Remedial Actions ..... 2-97 17.5.2 Protection of Workers During Remedial Actions ......... 2-101 17.5.3 Environmental Impacts..................................................... 2-102 17.5.4 Time Until Remedial Action Objectives Are Achieved...................................................................... 2-103 17.6 Implementability ............................................................................. 2-104 17.7 Cost .............................................................................................. 2-104 17.8 State Acceptance .............................................................................. 2-106 17.9 Community Acceptance ................................................................. 2-106 17.10 Summary of Comparative Analysis of Alternatives................... 2-106 18.0 Principal Threat Wastes.............................................................................. 2-107 19.0 Selected Remedy.......................................................................................... 2-108 19.1 Summary of the Rationale for the Selected Remedy .................. 2-108 19.1.1 Indoor Air: Vapor Mitigation System............................ 2-108 19.1.2 Source Area: Thermal Treatment ................................... 2-108 19.1.3 Shallow Plume Core and Hot Spot: ISCO With Follow-On Bio-Barrier (Flexible) ..................................... 2-109
19.1.4 Shallow Plume Periphery, Deeper Plume: ERD Bio-Barrier.................................................................. 2-110
19.2 Description of the Selected Remedy ............................................. 2-110 19.2.1 Indoor Air ........................................................................... 2-111 19.2.2 Source Areas....................................................................... 2-111 19.2.3 Shallow Plume Core and Hot Spot.................................. 2-114 19.2.4 Shallow Ground Water Plume Periphery ...................... 2-116 19.2.5 Deeper Ground Water Plume .......................................... 2-118 19.3 Contingency Remedy...................................................................... 2-119 19.4 Cost Estimate for the Selected Remedy........................................ 2-120 19.5 Expected Outcomes of the Selected Remedy............................... 2-121 19.5.1 Available Land Uses.......................................................... 2-121 19.5.2 Available Ground Water Uses ......................................... 2-121 19.5.3 Final Cleanup Levels......................................................... 2-121 20.0 Statutory Determinations ........................................................................... 2-122 20.1 Protection of Human Health and the Environment ................... 2-122 20.2 Compliance with Applicable or Relevant and Appropriate Requirements ............................................................ 2-122 20.3 Cost Effectiveness ........................................................................... 2-124 20.4 Utilization of Permanent Solutions to the Maximum Extent Practicable ............................................................................ 2-124
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CONTENTS VII
Contents (continued)
Part Page 20.5 Preference for Treatment as a Principal Element........................ 2-125 20.6 Five-Year Review Requirements ................................................... 2-125 21.0 Documentation of Significant Changes from Preferred Alternative of Proposed Plan..................................................................... 2-126 22.0 State Role .............................................................................................. 2-126 3 RESPONSIVENESS SUMMARY.............................................................................. 3-1 23.0 Responsiveness Summary.............................................................................. 3-1 24.0 References .................................................................................................. 3-6
Appendices A Administrative Record Index B Cost Estimate for Selected Remedy C NMED Concurrence With the Selected Remedy D Responsiveness Summary E NRRB Summary and Responses
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CONTENTS VIII
Figures Figure 1: Area Map Figure 2: Site Map Figure 3: Ground Water Elevation Contour Map Figure 4: Site Conceptual Model – Flow Chart Form Figure 5: Site Conceptual Model – Pictorial Form Figure 6: Soil Sampling Locations Figure 7: Ground Water Sampling Locations Figure 8: Indoor Air and Soil Vapor Sampling Locations Figure 9: Horizontal Extent of Chlorinated Solvents Contamination Figure 10: Vertical Extent of Chlorinated Solvents Contamination Figure 11: Structures with Vapor Intrusion Mitigation systems Figure 12: Extent of Source Area Treatment Figure 13: Conceptual Layout of ISCO w/Follow-On ERD (Shallow Plume Core) Figure 14: Conceptual Layout of ERD Bio-Barrier (Shallow Plume Core) Figure 15: Conceptual Layout of ERD Bio-Barrier (Shallow Plume Periphery) Figure 16: Conceptual Layout of ERD Bio-Barrier (Deeper Plume)
Tables Table 1: Criteria used for evaluation of indoor air Table 2: Summary of COCs and Medium-Specific Exposure Point Concentration
(Ground Water) Table 3: Summary of COCs and Medium-Specific Exposure Point Concentration
(Indoor Air) Table 4: Selection of Exposure Pathway Table 5: Values Used For Daily Intake Calculations (Ground Water) Table 6: Values Used For Daily Intake Calculations (Indoor Air) Table 7: Non-Cancer Toxicity Data Summary Table 8: Cancer Toxicity Data Summary Table 9: Risk Characterization Summary, Non-Carcinogens Table 10: Risk Characterization Summary, Carcinogens Table 11: Summary ARARs Table 12: Description of ARARs for Selected Remedy Table 13: Evaluation Criteria for Superfund Remedial Alternatives Table 14: Comparison of Remedial Alternatives, Vapor Intrusion Mitigation Table 15: Comparison of Remedial Alternatives, Source Area Treatment Table 16: Comparison of Remedial Alternatives, Shallow Ground Water Plume Core
and Hot Spot Table 17: Comparison of Remedial Alternatives, Shallow Ground Water Periphery Table 18: Comparison of Remedial Alternatives, Deeper Ground Water Table 19: Cost Summary for Remedial Alternatives Table 20: Final Cleanup Levels for Chemicals of Concern
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
CONTENTS IX
Abbreviations and Acronyms
1,1-DCA 1,1-dichloroethane 1,1-DCE 1,1-dichloroethene ARAR Applicable or Relevant and Appropriate Requirements ATSDR Agency for Toxic Substances and Disease Registry BHHRA Baseline Human Health Risk Assessment bgs below ground surface BTEX benzene, toluene, ethylbenzene, and xylenes °C Celsius CERCLA Comprehensive Environmental Response, Compensation, and Liability Act
(Superfund) CFR Code of Federal Regulations cis-1,2-DCE cis-1,2-dichloroethene COC contaminant/chemical of concern COPC chemical of potential concern CSM conceptual site model DNAPL dense non-aqueous phase liquid DOT U.S. Department of Transportation ELCR Excess Lifetime Cancer Risk EPA U.S. Environmental Protection Agency EPC exposure point concentration ERD enhanced reductive dechlorination; Enhanced Reduction Bio-barrier ERH electrical resistive heating ESD Explanation of Significant Differences
°F degrees Fahrenheit FI Facility Investigation FS Feasibility Study ft feet GAC granular activated carbon GCSP Grants Chlorinated Solvents Plume gpm gallons per minute HHMSSL Human Health Medium-Specific Screening Level (EPA Region 6) HI hazard index HQ hazard quotient
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
CONTENTS X
IRIS Integrated Risk Information System (EPA) ISCO in-situ chemical oxidation (ISCO MCL maximum contaminant level MG million gallons
µg/L micrograms per liter
µg/kg micrograms per kilogram
µg/m3 micrograms per cubic meters mg/kg milligrams per kilogram mg/kg-day milligrams per kilogram per day MNA monitored natural attenuation msl mean sea level MST&T Mountain States Telephone and Telegraph Company MTBE methyl tert-butyl ether NCEA National Center for Environmental Assessment NCP National Contingency Plan NMAC New Mexico Administrative Code NMED New Mexico Environment Department NMED-PSTB New Mexico Environment Department-Petroleum Storage Tank Bureau NMED-SOS New Mexico Environment Department-Superfund Oversight Section NPL National Priorities List NRRB National Remedy Review Board O&M operations and maintenance OSE New Mexico Office of the State Engineer PA Preliminary Assessment PCE tetrachloroethene ppb parts per billion PRB permeable reactive barrier PRG Preliminary Remediation Goal PRP Potential Responsible Party PSH phase-separated hydrocarbon RAO Remedial Action Objective RCRA Resource Conservation and Recovery Act RD Remedial Design RfC reference concentration RfD reference dose RI Remedial Investigation RI/FS Remedial Investigation/Feasibility Study RME Reasonable Maximum Exposure ROD Record of Decision ROI radius of influence SARA Superfund Amendments and Reauthorization Act
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
CONTENTS XI
SF slope factor (cancer) SI Sampling Inspection or Site Investigation SOD soil oxidant demand SSL soil screening level SVE soil vapor extraction TAG Technical Assistance Grant TCE trichloroethene TMV toxicity, mobility, and volume trans-1,2-DCE trans-1,2-dichloroethene UCL upper confidence level USGS U.S. Geological Survey UST underground storage tank VC vinyl chloride VOC volatile organic compound WQCC Water Quality Control Commission (New Mexico) yd3 cubic yard ZVI zero-valent iron
Part 1. The Declaration
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-1
Part 1: The Declaration
1.0 Site Name and Location
The Grants Chlorinated Solvents Plume (GCSP) Site is located in Grants, New Mexico
(Cibola County). The National Superfund Database Identification Number is NM007271768.
2.0 Statement of Basis and Purpose
This decision document presents the “Selected Remedy” for the Grants Chlorinated Solvents
Plume Site (hereinafter “the Site or GCSP Site”). The Selected Remedy was chosen in
accordance with the Comprehensive Environmental Response, Compensation and Liability
Act of 1980 (CERCLA), 42 United States Code §9601 et seq., as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA), and, to the extent practicable, the
National Oil and Hazardous Substances Pollution Contingency Plan (NCP), 40 Code of
Federal Regulations (CFR) Part 300, as amended.
This decision is based on the Administrative Record for the Site, which has been developed
in accordance with Section 113(k) of CERCLA, 42 United States Code §9613(k). This
Administrative Record file is available for review at the University of New Mexico, Grants
Campus, Grants, New Mexico, the New Mexico Environment Department (NMED) offices
in Santa Fe, New Mexico, and at the U.S. Environmental Protection Agency (EPA Region 6)
Records Center in Dallas, Texas. The Administrative Record Index (Appendix A) identifies
each of the items comprising the Administrative Record upon which the selection of the
Remedial Action is based. The State of New Mexico (NMED) concurs with the Selected
Remedy.
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-2
3.0 Assessment of the Site
The response action selected in this Record of Decision (ROD) is necessary to protect the
public health or welfare or the environment from actual or threatened releases of hazardous
substances into the environment.
4.0 Description of the Selected Remedy
The EPA will address the site contamination as one operable unit. The site-specific media
have been divided in to five categories to address the chlorinated solvents contamination in
indoor air, soil, and ground water.
The five categories are:
• Indoor Air – Ambient air within residential structures.
• Source Areas – two source areas exist at the GCSP site and are targeted for cleanup. The
larger Holiday Cleaners source area includes roughly the entire property, an area
approximately 150 ft by 100 ft in size. The depth interval requiring treatment extends
from the land surface to approximately 80 ft below ground surface (bgs). The
abandoned dry cleaner facility source area is approximately 30 ft by 80 ft. The depth
interval requiring treatment extends from the land surface to approximately 35 ft bgs.
• Shallow Plume Core and Hot Spot – The shallow ground water plume core is defined as
the portion of the plume with PCE and/or TCE concentrations exceeding 5,000 µg/L
(micrograms per litre), which is a value 1,000 times the ground water final cleanup goal
for PCE and TCE. Similarly, the shallow ground water hot spot is defined as the portion
of the plume on Jefferson Avenue between First Street and Geis Street, which is offset
from the primary plume core axis, where PCE and/ or TCE concentrations also exceed
5,000 µg/L.
• Shallow Ground Water Plume Periphery – The shallow ground water plume periphery
is defined as the portion of the shallow PCE ground water plume (as identified during
the Remedial Investigation [RI]) beyond the plume core where PCE concentrations still
exceed the Maximum Contaminant Level (MCL) within the upper 20 ft of the subsurface
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-3
but are less than 5,000 µg/L. This includes an area extending approximately 1,500 ft
downgradient of the Holiday Cleaners source area, over a width of approximately 500 to
600 ft.
• Deeper Ground Water Plume – Deeper ground water is defined as all ground water
below 20 ft bgs with contamination above the MCL, based on sampling conducted
during the RI.
The components of the Selected Remedy are described in detail in Section 19 of this ROD.
Briefly, the major components of the Selected Remedy are:
1. Indoor Air: Vapor Mitigation
The EPA will install vapor intrusion mitigation systems at 14 residences that are located
directly above the ground water plume where concentrations of trichloroethene (TCE) or
tetrachloroethene (PCE) in ground water exceed 1,000 µg/L and other locations where
indoor air concentrations exceed a one in 100,000 (1x10-5) risk level.
Indoor air monitoring will be conducted prior to and following construction and at least
once every 5 years until ARARs are met to ensure remedy protectiveness.
2. Source Area: Thermal Treatment
Thermal treatment will be implemented at the source areas through heater
probes/electrode vapor extraction wells with the central onsite treatment facility located
at the Holiday Cleaners source area property.
Site-specific bench- and/or pilot–scale testing will be performed prior to Remedial
Design (RD).
Performance monitoring will be conducted during the implementation of this remedy.
3. Shallow Plume Core and Hot Spot: In-Situ Chemical Oxidation (ISCO) with Follow-On
Enhanced Reductive Dechlorination (ERD)
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-4
The EPA will be flexible in applying this technology based on data gathered during the
Predesign Field Investigation. Based on the data collected, the EPA may choose to
implement ISCO with Follow-On ERD or only the ERD component.
Site-specific bench- and/or pilot–scale testing will be performed prior to RD.
ISCO applications (potassium or sodium permanganate) are followed by ERD (vegetable
oil) applications in permanent wells installed within the ground water plume.
Performance monitoring will be conducted throughout the active treatment period.
4. Shallow Ground Water Plume Periphery: ERD Bio-Barrier
ERD involves injecting carbon amendments (vegetable oil) into the aquifer periodically
to support the growth of in-situ bacteria capable of treating the chlorinated solvents.
Site-specific bench- and/or pilot–scale testing will be performed prior to RD.
The amendments will be delivered through approximately 100 permanent injection
wells once every 15 months over a 20-year period.
A total of approximately 2,400 feet (ft) of bio-barrier wall will be installed with multiple
transects spaced approximately 200 ft apart.
Performance monitoring will be conducted throughout the active treatment period.
5. Deeper Ground Water Plume: ERD Bio-Barrier
ERD involves injecting carbon amendments (vegetable oil) into the aquifer periodically
to support the growth of in-situ bacteria capable of treating the chlorinated solvents.
Site-specific bench- and/or pilot–scale testing will be performed prior to RD.
ERD amendments will be delivered through approximately 50 permanent injection wells
once every 15 months over a 20-year period.
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-5
A total of approximately 1,000 ft of bio-barrier wall will be installed to a depth of
approximately 60 ft bgs and approximately 250 ft of bio-barrier will be installed to a
depth of approximately 80 ft bgs.
Performance monitoring will be conducted throughout the active treatment period.
The complete vertical extent of contamination is not fully defined at this time. Further
characterization will be conducted during the Preliminary Field Investigation and the
remedy will be implemented such that the entire vertical extent is addressed. The remedy
will be re-evaluated during the design phase if new information regarding the vertical and
horizontal extent of the plume is determined.
The Selected Remedy will address the principal threat wastes, Dense Nonaqueous Phase
Liquids (DNAPL) and chlorinated solvents in ground water and soil such that the Site is
made safe for residential use. The EPA will implement the Selected Remedy in a phased
manner in the order listed above.
4.1 Institutional Controls
To protect human health from exposure to the existing ground water contamination while
cleanup is ongoing, the EPA and NMED will request the New Mexico Office of the State
Engineer (OSE) to issue an order restricting future well drilling within a portion of the
aquifer contaminated by the plume until remediation goals (RGs) for the ground water are
met. The order will only apply to new requests for water well permits and cannot be
enforced against existing water well permit holders. The OSE does not have a vested
enforcement authority but has the ability to enforce with a court order. Based on interviews
the existing wells are not being used for any purpose. The EPA will work with NMED to
issue a health advisory not to consume ground water from the existing wells within the
plume area.
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-6
4.2 Contingency Remedy
EPA will evaluate the site conditions to determine if monitored natural attenuation (MNA)
is a viable remedial alternative after the first Five-Year Review and after source control has
been established in the Source Areas and the Shallow Ground Water Plume. If ground
water data demonstrates evidence that MNA is occurring such that RAOs will be met in a
timely manner, then EPA may consider proposing MNA as the remedial strategy for the
Shallow Ground Water Periphery and the Deeper Ground Water Plume. If this alternative
is determined to be the most efficient and effective remedy, then EPA with NMED’s
concurrence will issue an Explanation of Significant Differences (ESD) to document the
change in the remedy. MNA is not a component of the Selected Remedy.
MNA is a proven ground water remedy at many sites; however, at this time there is
insufficient data to select MNA as a component of the Selected Remedy at the GCSP Site.
The EPA will collect the necessary data for MNA evaluation during the pre-design
investigation phase. The contingency will be invoked not because of a potential failure of
the Selected Remedy but rather as an alternative that would not only achieve final cleanup
goals but also provide significant cost savings to the agency.
5.0 Statutory Determinations
The Selected Remedy attains the mandates of CERCLA §121, and the regulatory
requirements of the NCP. This remedy is protective of human health and the environment,
complies with Federal and State requirements that are applicable or relevant and
appropriate to the Remedial Action, is cost-effective, and utilizes permanent solutions to the
maximum extent practicable.
The Selected Remedy also satisfies the statutory preference for treatment as a principal
element of the remedy (i.e., reduce the toxicity, mobility, or volume of hazardous substances
through treatment). The concentrations of chlorinated solvents in the ground water at the
Site indicate presence of DNAPL, which is considered a principal threat waste. The thermal
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 1 – THE DECLARATION 1-7
treatment at the source areas and active treatment in the downgradient areas are expected to
remove any DNAPL present and eliminate the threat to the deeper drinking water aquifer.
Ground water restrictions area necessary because the Selected Remedy will initially
result in hazardous substances, which are above levels that allow for unlimited use
and unrestricted exposure. A statutory review will be conducted within five years
after initiation of the remedial action to ensure that the remedy continues to provide
adequate protection of human health and the environment. This review will be
conducted not less often than every five years after the date of the initiation of the
remedial action.
6.0 ROD Data Certification Checklist
The following information is included in the Decision Summary (Part 2) of this ROD, while
additional information can be found in the Administrative Record file for this site:
a) Chemicals of concern (COCs) and their respective concentrations (see Section 14.1.1
Identification of Chemicals of Concern);
b) Baseline risk represented by the COCs (see Section 14.1.4 Risk Characterization);
c) Remediation goals (i.e., cleanup goals) established for the COCs and the basis for the
goals (see Section 19.5.3 Final Cleanup Levels);
d) How source materials constituting principal threats are addressed (see Section 5.0
Statutory Determinations and Section 18.0 Principal Threat Wastes);
e) Current and reasonably anticipated future land use assumptions and current and
potential future beneficial uses of ground water used in the Baseline Human Health Risk
Assessment and this ROD (see Section 13.1 Current and Potential Future Land Uses,
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
Section 13.2 Current and Potential Future Ground Water Uses, Section 19.5.1 Available
Land Uses, and Section 19.5.2 Available Ground Water Uses);
f) Potential land and ground water use that will be available at the site as a result of the
Selected Remedy (see Section 13.1 Current and Potential Future Land Uses, Section 13.2
Current and Potential Future Ground Water Uses, Section 19.5.1 Available Land Uses,
and Section 19.5.2 Available Ground Water Uses);
g) Estimated capital, lifetime operation and maintenance (O&M), and total present worth
costs; discount rate; and the number of years over which the remedy cost estimates are
projected (Section 19.4 Cost Estimate for the Selected Remedy; and Appendix B Cost
Estimate for Selected Remedy); and
h) Key factor(s) that led to selecting the remedy (see Section 14.3 Basis for Remedial
Action).
7.0 Authorizing Signature
This ROD documents the Selected Remedy for contaminated soil, ground water, and indoor
air at the GCSP Superfund Site. The EPA selected this remedy with the concurrence of the
NMED (Appendix C - NMED Concurrence with the Selected Remedy). The Director of the
Superfund Division (EPA, Region 6) has been delegated the authority to approve and sign
this ROD.
By:
Samuel Coleman, P.E., DirectorSuperfund Division (6SF)
PART 1 -THE DECLARATION
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS. NM. RECORD OF DECISION
CONCURRENCE PAGERECORD OF DECISION FOR
THE GRANTS CHLORINATED SOLVENTS PLUME SUPERFUND SITE
Sai Appaji,Remedial Project Manager
Date
Don Williams,Team Leader
Wren Stenger,Chief, LA/OK/NM Bra
Date
I-Jung Chiang,Site Attorney
Date
Mark Peycke, v DateChief, Regional Counsel Superfund
1 Coleman) P.E.frector, Superfund Division
Date
PART 1 - THE DECLARATION 1-9
THIS PAGE INTENTIONALLY LEFT BLANK.
Part 2. The Decision Summary
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 2 – THE DECISION SUMMARY 2-1
Part 2: The Decision Summary
This Decision Summary provides a description of the site-specific factors and analyses that
led to the selection of the indoor air, soil, and ground water remedies for the site. It includes
background information about the site, the nature and extent of contamination found at the
site, the assessment of human health and environmental risks posed by the contaminants at
the site, and the identification and evaluation of remedial action alternatives for the site.
8.0 Site Name, Location, and Description
The GCSP Site is located in the City of Grants, Cibola County, New Mexico (Figure 1). The
site is bounded by Second Street to the west; Adams Avenue and Jefferson Avenue to the
North; Anderman Street, Washington Avenue, and Mesa View Elementary School property
to the east; and Stephens Avenue and the Rio San Jose to the south. The GCSP Site is
located in a mixed commercial and residential area.
The approximate area of ground water contamination at the GCSP Site is 20 acres. A site
map is provided in Figure 2. The geographic coordinates of the GCSP Site are
approximately 35°9’20”N latitude and 107°51’15”W longitude and within Township 11
North, Range 10 West, Section 25 of the U.S. Geological Survey (USGS) Grants Quadrangle
7.5 minute map. The approximate elevation of the Site is 6,420 ft above mean sea level (msl).
The National Superfund Database Identification Number for the Site is NM007271768. The
GCSP Site is a fund-lead site, with the EPA being the lead agency for the remedial activities,
and NMED the support agency. The Potential Responsible Party (PRP) for the site did not
participate in the Remedial Investigation/Feasibility Study (RI/FS).
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Dry cleaning operations have been historically performed at multiple facilities within the
GCSP Site, although only a single dry cleaning facility, Holiday Cleaners at 715 First Street,
is currently active. Dry cleaning has historically been performed at the R&L Laundry
(reportedly prior to approximately 1987), at an abandoned facility at 605 First Street just
north of Washington Avenue, and at a former Holiday Cleaners location at 313 First Street
north of Stephens Avenue. The active Holiday Cleaners has operated at its current location
since approximately 1969, and under the current ownership since approximately 1975.
9.0 Site History of Enforcement Activities
This section of the ROD provides the history of the site and a brief discussion of the EPA's
and the State's remedial and enforcement activities. The "Proposed Rule" proposing the site
to the National Priorities List (NPL) was published in the Federal Register on March 8, 2004.
The "Final Rule" adding the site to the NPL was published in the Federal Register on July 22,
2004.
9.1 History of Site Activities
Chlorinated solvents were first identified in ground water at the GCSP Site in 1993, during a
NMED – Petroleum Storage Tank Bureau (NMED-PSTB) investigation of leaking
underground storage tank (UST) sites in the vicinity.
Several possible sources for the release of chlorinated solvents to the ground water were
identified during the subsequent NMED Preliminary Assessment (PA), the NMED Site
Investigation (SI), and the Remedial Investigation (RI). The PA considered all of the UST
sites in the vicinity of the ground water plume as potential sources for chlorinated solvents.
However, there was no record of the use or storage of chlorinated solvents at any of these
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sites. Several other sites were identified that are presently using or may have used
chlorinated solvents in the past. These include the following locations:
• Holiday Cleaners (715 First Street)
• Former Holiday Cleaners (313 First Street) (currently Audio/Video Hill)
• R&L Laundry (604 First Street)
• Abandoned Dry Cleaning Facility (605 First Street)
• Former Wash ‘n Clean World (located in Baties Shopping Center on north side of
Stephens Avenue between First Street and Anderman Street)
• Former Mountain States Telephone and Telegraph Company (MST&T) (621 Geis Street)
maintenance yard, which is now a private residence and automotive hobby shop
• A work shed located behind a private residence at 700 First Street
Based on interviews conducted by the NMED-Superfund Oversight Section (NMED-SOS),
the current and past owners of Holiday Cleaners on 715 First Street have used PCE for a
number of years (NMED, 2001). During interviews, the current owner of Holiday Cleaners
reported that historically PCE leaked from cleaning equipment onto the building floor, as
well as from a storage container maintained in the rear portion of the building. When the
container was full, PCE occasionally overflowed onto the ground surface in response to
thermal expansion of the PCE fluid. This equipment has been removed from service and
upgraded and the PCE storage tank is no longer in use at the Holiday Cleaners.
The RI conducted by EPA identified the Abandoned Dry Cleaners property on First Street as
a secondary source of ground water contamination. The remaining suspected locations
identified above were not determined to be sources for ground water contamination based
on available information.
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9.2 History of Federal and State Investigations
9.2.1 Site Investigation Report
Following the discovery of the chlorinated solvent contamination at the GCSP Site,
NMED-SOS conducted a series of investigations from September 1998 through August 2000
to identify the sources and characterize the distribution of chlorinated solvents in soil and
ground water.
The SI Report (NMED, 2001) is the primary source of background information assembled
for the GCSP Site. The SI gathered information regarding the site description and history;
identification of potential sources; previous NMED-PSTB investigations; collection of initial
soil, soil vapor, and ground water samples; air, soil, and ground water pathway
identification; and ground water receptor identification.
In addition to the NMED SI Report, the following investigations were completed after the
SI Report had been prepared but prior to the initiation of RI field activities:
• Rio San Jose Hyporheic Zone Sampling (EPA, 2002)
• Allsup’s 200 Secondary Investigation Report (Tetra Tech EM, Inc., 2003)
9.2.2 Rio San Jose Hyporheic Zone Sampling
Concurrent with the planning phase of the RI, EPA and NMED collected water samples
from the Rio San Jose. On December 11, 2002, EPA and NMED performed a joint sampling
effort of the shallow ground water/surface water interface (hyporheic zone) of the
Rio San Jose in the vicinity of the GCSP Site. The hyporheic zone was sampled at
seven locations along the Rio San Jose from Second Street on the west to 600 ft east of
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Anderman Street on the east. An eighth location was sampled just west of the intersection
of Second Street and Monroe Avenue, within a drainage ditch along Second Street, west of
the Holiday Cleaners. A ninth location was sampled adjacent to a lint trap at a suspected
Former Dry Cleaning Facility approximately 400 ft east of the intersection of First Street and
Stephens Avenue.
The results of the laboratory analyses indicated that PCE was not detected in these samples.
However, 1,1-Dichloroethane (1,1-DCA) and cis-1,2-dichloroethene (cis-1,2-DCE) were
detected in four of the samples and TCE was detected in one of the samples. All detected
concentrations were less than their respective federal maximum contaminant levels (MCLs).
The chlorinated volatile organic compounds (VOCs) observed in the hyporheic zone first
appear at the intersection of the Rio San Jose with First Street. It does not appear that these
chlorinated VOC compounds in the hyporheic zone are related to the primary release
locations identified during the SI or RI, based on contaminant distribution discussed in
Section 5.2. Although the concentrations of chlorinated solvents were below EPA MCLs for
each of the analytes, the presence of these compounds indicates that chlorinated solvents are
entering the Rio San Jose from another undefined source, potentially near First Street.
9.2.3 Allsup’s 200 Secondary Investigation Report
The NMED-PSTB initially investigated five leaking UST sites near the GCSP Site, which
were discovered as the result of UST removal and/or upgrade activities. These sites are the
Allsup’s 200, Atex #71, Tommy’s 66, Spencer Automotive, and the Grants School
Maintenance Yard.
NMED-PSTB conducted a Secondary Investigation at the Allsup’s 200 site to further
investigate the confirmed release of petroleum hydrocarbons from this site. Investigations
performed at this leaking UST site were independent of the RI activities at the GCSP Site.
The NMED-PSTB provided EPA with the results of this Secondary Investigation. The field
investigation was completed from May 14 through July 6, 2003.
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The Secondary Investigation indicated the following items regarding site hydrogeologic
conditions and petroleum hydrocarbon compounds in ground water:
• Ground water was contaminated with dissolved-phase benzene, toluene, ethylbenzene,
and xylenes (BTEX).
• Phase-separated hydrocarbon (PSH) is present onsite at the Allsup’s 200 site and is
confined to the site boundary.
• The dissolved-phase gasoline plume migrates southeast towards Geis Street.
• Methyl tert-butyl ether (MTBE) exists downgradient of Allsup’s well MW-11 and the
horizontal extent of MTBE has not been defined in the downgradient direction.
• Ground water flow was to the southeast with a gradient of 0.003.
• Anaerobic conditions exist within the plume.
The results of the Secondary Investigation additionally indicated the following regarding
chlorinated solvents at the Allsup’s 200 site:
• Chlorinated solvents were detected in 11 of the 12 site wells.
• PCE was detected at concentrations ranging from less than 1 microgram per liter (µg/L)
to 6,200 µg/L.
• TCE was detected at concentrations ranging from less than 1 µg/L to 5,500 µg/L.
• Cis-1,2-DCE was detected at concentrations ranging from less than 1 µg/L to
3,200 µg/L.
• Trans-1,2-dichloroethene (trans-1,2-DCE) was detected at concentrations ranging from
less than 1 µg/L to 380 µg/L.
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• 1,1-dichloroethene (1,1-DCE) was detected at concentrations ranging from less than
1 µg/L to 6.2 µg/L.
9.2.4 EPA’s Remedial Investigation
Based on the results of the NMED-SOS sampling conducted from 1998 through 2000, the
EPA initiated an RI/FS for the GCSP Site to further characterize the nature and extent of
contamination and to evaluate remedial alternatives for the site. The RI sampling program
was designed based on the data previously obtained at the site and was intended to
augment the historic data.
The EPA conducted the RI in phases beginning in October 2003 and ended in April 2005.
The RI investigation included the collection and analysis of onsite soil, soil gas, ground
water, and vapor intrusion samples from indoor and outdoor locations. Soil, soil vapor, and
ground water samples were collected using the direct-push drilling technique. Indoor and
outdoor air samples were collected in summa canisters. The RI Report (EPA, 2005a),
documents in detail the nature and extent of contamination present at the site.
9.2.5 National Remedy Review Board Review
The EPA’s National Remedy Review Board (NRRB) reviewed the proposed remedy for the
site on March 29, 2006, and provided some recommendations. The NRRB has been set up
by the EPA to help control response costs and promote consistency with the NCP and
Superfund policy guidance. The NRRB comprises of cross-regional and management-level
members who evaluate cleanup actions that exceed cost-based review criteria. A copy of the
NRRB’s comments and EPA Region 6’s response are included in Appendix E.
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9.3 History of CERCLA Enforcement Activities
The EPA has conducted PRP searches and has issued 104(e) Information Requests to past
owners, operators, and current owners of Holiday Cleaners. The principal PRP for this site
is the current owner of Holiday Cleaners.
Information Requests were sent to four PRPs on March 8, 2004 and all four responded. On
August 24, 2004, the EPA followed up with another Information Request regarding their
financial status. All PRPs have complied with the request for information. At this time the
EPA is reviewing the financial viability of the PRPs and has not made a decision on
enforcement.
10.0 Community Participation
This section of the ROD describes the EPA's community involvement activities. The EPA
has actively sought a dialogue and collaboration with the affected community and has
strived to advocate and strengthen early and meaningful community participation during
the EPA's remedial activities at the site. These community participation activities during the
remedy selection process meet the public participation requirements in CERCLA §121 and
the NCP 40 CFR §300.430(f)(3).
10.1 Community Meetings
The EPA and NMED have conducted numerous community meetings during the course of
the RI/FS for the site and provided public notices of these meetings to encourage the
community's participation. Following is a brief summary of the community meetings held
by the EPA.
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On October 7, 2003, the EPA conducted the first public meeting in Grants, New Mexico to
inform the residents about the Superfund Site and the upcoming RI/FS. Residents also
were informed about indoor air sampling activities at some homes located over the plume.
Fact sheets with site information also were mailed to residents prior to the meeting.
On December 15, 2004, a second public meeting was held at Grants to inform the public
about the progress of the RI. Fact sheets with updated information were mailed and
provided during the meeting.
10.2 Public Meeting for the Proposed Plan
A public meeting was held on April 20, 2006, at the Cibola Convention Center, Grants,
New Mexico, to present the Proposed Plan (EPA, 2006a) to community members.
Representatives from the EPA answered questions about the EPA's preferred alternative for
the site. Oral and written comments were accepted at the meeting. A court reporter
transcribed the discussions held during the meeting. This transcript is included in the
Administrative Record file for the site, which is maintained at the Information Repository
located at the University of New Mexico, Grants Campus, NMED’s office located in
Santa Fe, and the EPA's office located in Dallas, Texas.
The RI (EPA, 2005a), FS Report (EPA, 2006b), Baseline Human Health Risk Assessment
(EPA, 2005b), and Proposed Plan (EPA, 2006a) for the site were made available to the public
on April 11, 2006. These documents are currently located in the Administrative Record file
for the site. The notice of the availability of these documents was published in the Cibola
Beacon on April 11, 2006. A public comment period was held from April 12, 2006 to May 11,
2006.
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10.3 Technical Assistance Grant
Information about the availability of Technical Assistance Grant (TAG) was provided
during the public meetings in October 2003 and December 2004. However, no groups came
forward to seek the grants.
10.4 Fact Sheets
Numerous fact sheets, both in English and Spanish, have been prepared during the
planning and implementation of the RI/FS. These fact sheets were placed at the GCSP Site's
repository and distributed to those community members on the mailing list.
10.5 Local Site Repository
The purpose of the local site repository is to provide the public a location near the
community to review and copy background and current information about the site.
The repository is located near the GCSP Site at:
University of New Mexico Grants Campus Library 1500 Third Street Grants, NM 87020
11.0 Scope and Role of Response Action
The entire site is addressed as one operable unit. The two main objectives for response
action at this site are to remove vapor intrusion risk and treat ground water so that COCs
are below MCLs and the site is made safe for residential use. The planned Remedial Action
is a final action for the site and is expected to successfully achieve the Remedial Action
Objectives (RAOs). Through the use of a mix of different treatment technologies, this
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response will permanently reduce the toxicity, mobility, and volume of those source
materials that constitute the principal threat wastes at the Site and restore ground water to
meet ARARs. The site-specific media impacted are the following: Indoor Air, Soil, and
Ground Water. The EPA has selected a combination of technologies to address the
contamination in the various media.
12.0 Site Characteristics
This section of the ROD provides an overview of the site's geology and hydrogeology; the
sampling strategy chosen for the site; the conceptual site model (CSM); and the nature and
extent of contamination at the site. Detailed information about the site's characteristics can
be found in the RI Report (EPA, 2005a).
12.1 Overview of the Site
The City of Grants is located in north-central Cibola County, New Mexico. Cibola County
borders Arizona and is slightly north of the north-south centerline of the state of
New Mexico. The City of Grants can be found on the “Grants” USGS 7.5-Minute
Topographic Quadrangle, primarily in Section 25, Township 11 North, Range 10 West and
Section 30, Township 11 North, Range 9 West. The City of Grants is at an elevation of
approximately 6,420 ft above msl.
The topography surrounding Grants, New Mexico is composed of mesas extending
hundreds to approximately 1,000 ft above broad valleys and dissected by steep canyons.
The highest point in the region is Mount Taylor, approximately 15 miles to the northeast, at
an elevation of 11,301 ft. Black Mesa rises just northwest of the City of Grants to an
elevation of approximately 7,200 ft. West Grants Ridge, Grants Ridge, and East Grants
Ridge rise north and northeast of Grants to elevations between 7,200 ft and 7,500 ft. Horace
Mesa, at an elevation of approximately 7,800 ft, rises east of the City of Grants.
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The Rio San Jose and its tributaries comprise the main drainage system in the area. The
Rio San Jose flows through the City of Grants, and is sourced from Bluewater Creek to the
west. Bluewater Creek is dammed by Bluewater Dam, forming Bluewater Lake,
approximately 20 miles west of the City of Grants. The Rio San Jose discharges to the
Rio Puerco approximately 50 miles to the east of Grants.
The climate in the Grants area is semiarid and characterized by low precipitation, cool and
dry winters, warm summers, and low relative humidity. During the period of record from
1953 to 2004, the mean January and July temperatures were 30.2 and 71.6 degrees
Fahrenheit (°F), respectively (NMED, 2001). The mean annual total precipitation was
10.38 inches for the period of record from 1953 to 2004 (NMED, 2001). The greatest amount
of precipitation occurs during the summer and early fall with approximately 58 percent of
the annual average precipitation occurring during the months of July, August, September,
and October. The mean annual snowfall was 13.59 inches for the period of record from 1953
to 2004 (NMED, 2001). Snowfall occurs between the months of October and April, and is
greatest during December.
12.2 Site Geology
Shallow lithology beneath the GCSP Site was characterized during Phase 1 of the RI by
direct-push sampling. A direct-push drilling rig was used to advance a total of 85 borings
throughout the site, and each boring was lithologically characterized in the field. These
borings were advanced to a maximum depth of approximately 16 ft bgs. At each of these
borings, the shallow subsurface was predominately clay and silt, with thin, laterally-
continuous sand and silty sand layers. A 6-inch to 1-ft thick sand and silty sand layer was
identified continuously from the Holiday Cleaners to at least the intersection of Washington
Avenue and Anderman Street at a depth gradually increasing from approximately 8 ft bgs
to approximately 16 ft bgs.
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Additional lithologic characterization was performed during the Phase 2 direct-push
sampling event. Lithologic information was collected to a maximum depth of
approximately 40 ft bgs at three locations during this investigation. Lithologic data also
were collected during the drilling of six monitoring wells by NMED (GMW-1 through
GMW-6). The drilling log for GMW-1 indicates fine- to medium-grained sand with some
gravel at a depth between 43 and 50 ft bgs, the greatest depth lithologically characterized at
the site.
12.3 Site Hydrogeology
Ground water is present within the shallow clay and silt alluvium at a depth of
approximately 5 to 6 ft bgs at the GCSP Site. The ground water table is somewhat deeper
(6 to 8 ft bgs) within the southeastern portion of the site. Ground water elevations have
been monitored on several occasions at the site. Figure 3 shows the ground water elevation
contour map from February 2004.
Ground water elevations varied by approximately 1 ft over the 5-year period 1999-2004, but
ground water flow directions remained consistent. In the northeast portion of the site, near
the Holiday Cleaners, ground water flows toward the southeast, turning slightly more
southward near Geis Street. In the western portion of the site, near the Atex #71 gasoline
station, ground water flows approximately due east, but quickly turns toward the southeast
to the east of the intersection of First Street and Washington Avenue. The ground water
gradient varies between approximately 0.004 and 0.006 (southeastward) near the
Tommy’s 66 gasoline station to between approximately 0.002 and 0.003 (southeastward)
near the Holiday Cleaners.
12.4 Sampling Strategy
The sampling strategy for the site addressed these key issues to determine the nature and
extent of contamination at the site:
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• Determine the presence of hazardous substances in soil, ground water and indoor air.
• Identify additional source(s) of hazardous substances to soil and ground water, if
present.
• Fully define the horizontal and vertical extent of hazardous substances in soil and
water-bearing strata underlying suspected source areas and the margins of the plume.
• Fully characterize the Site stratigraphy and hydrogeology, and evaluate temporal
variations in ground water flow and contaminant concentrations.
• Evaluate indoor air quality in buildings located over or in close proximity to the ground
water contaminant plume.
12.5 Conceptual Site Model
The CSM is presented in flow chart form in Figure 4 and in pictorial form in Figure 5. These
figures describe the primary contaminant sources, the primary release mechanisms,
secondary sources, secondary release mechanisms, and migration pathways. The primary
sources at the GCSP Site are the Holiday Cleaners at the corner of First Street and Monroe
Avenue and the Abandoned Dry Cleaning Facility on First Street north of Washington
Avenue. Contaminant release mechanisms, secondary sources, and migration pathways are
essentially the same for both sources. A potential source that cannot be ruled out based on
the data collected during the RI is a work shed near the intersection of First Street and
Jefferson Avenue. Additional characterization of the work shed location will be performed
during a preliminary design field investigation.
The primary release mechanisms at the active Holiday Cleaners facility were routine spills,
releases into a system of interior trenches, disposal of water decanted from a solvent/water
separator and discharged to the sanitary sewer, and overflowing of a former PCE storage
tank due to thermal expansion. The primary release mechanisms at the Abandoned Dry
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Cleaning Facility are less certain, since interviews were not conducted with the facility
owner. Similar release mechanisms as at the Holiday Cleaners are likely. Releases of PCE
by these mechanisms caused PCE to accumulate in surface soils, migrate into the subsurface
as DNAPL, and potentially flow through the sanitary sewer line. Soil, residual DNAPL, and
the sanitary sewer line are thus secondary sources of PCE. Secondary release mechanisms
include surface runoff, volatilization of PCE from soil and ground water, leaching of PCE
from soil and/or DNAPL during infiltration, dissolution of DNAPL in ground water, and
leakage of the sanitary sewer line. Once released into the environment at the GCSP Site,
PCE (and its degradation products) migrate within the shallow subsurface soils, soil vapor,
and ground water.
Release mechanisms at the Former Holiday Cleaners were likely similar to those at the
active Holiday Cleaners. PCE or other chlorinated VOCs, or products containing significant
quantities of these compounds, may have been stored at the work shed near the intersection
of First Street and Jefferson Avenue. Soil samples collected near the work shed indicate that
chlorinated VOCs may have been released to soil, potentially from periodic and/or routine
spills.
12.6 Nature and Extent of Soil Contamination
This section of the ROD describes the nature and extent of soil contamination found at
various suspected source locations. PCE and TCE are the primary COCs identified in
subsurface soil at the site. Figure 6 shows the sampling locations used during the RI.
12.6.1 Soil Contamination at Holiday Cleaners
Soil samples were collected from depths of 2 ft, 5 ft, and 10 ft bgs at locations surrounding
the Holiday Cleaners. PCE was detected to the maximum depth of exploration (10 ft bgs) at
several locations surrounding the Holiday Cleaners, and at a maximum concentration of
36 milligrams per kilogram (mg/kg) (nearly 70 times the EPA Region 6 Human Health
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Medium-Specific Screening Level [HHMSSL] of 0.55 mg/kg for residential soil) near the
southeast corner of the building. PCE also was detected at concentrations up to 21 mg/kg
in soil samples collected near the Holiday Cleaners southeastern property boundary. At the
Holiday Cleaners, TCE and other PCE degradation products were detected in soils
primarily near the southeastern property boundary, although TCE was detected just above
the EPA Region 6 HHMSSL (0.043 mg/kg) near the southeastern corner of the building.
12.6.2 Soil Contamination at Abandoned Dry Cleaners
PCE was detected in soil to the maximum depth of exploration (10 ft bgs) at locations
adjacent to and downgradient of the Abandoned Dry Cleaning Facility located on First
Street just north of Washington Avenue. PCE was detected at over 16 times the EPA
Region 6 HHMSSL near the east wall of the building (DP-13 at 2 ft bgs) and at over
three times the HHMSSL near the south wall (DP-12 at 5 ft bgs) of the building. PCE also
was detected at the far southeastern extent of the Abandoned Dry Cleaning Facility
property. TCE and other PCE degradation products were not identified in soil surrounding
the facility.
12.6.3 Soil Contamination at R&L Laundry
PCE was detected in two soil sampling locations in the alley behind the R&L Laundry,
which does not currently conduct dry cleaning, although it has in the past. PCE was
detected in soil below the EPA Region 6 SSL at a concentration of 0.082 mg/kg at the
northeastern building corner. PCE was detected at twice the EPA Region 6 SSL near the
building back door. PCE also was detected below the EPA Region 6 SSL at a location in
front of the building. TCE and other PCE degradation products were not detected in soil
surrounding the R&L Laundry.
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12.6.4 Soil Contamination at Former Holiday Cleaners
PCE was detected in a single soil sample collected from 2 ft bgs in the alley behind the
Former Holiday Cleaners location on First Street north of Stephens Avenue. PCE was
detected in soil below the EPA Region 6 SSL at a concentration of 0.095 mg/kg. Drilling
refusal was encountered at 2 ft bgs at all sampling locations surrounding the former facility
from an underlying basalt flow.
12.6.5 Soil Contamination at Former MST&T Company Maintenance Yard
PCE was detected at soil sampling locations near the edge of the former MST&T Company
maintenance property. PCE was detected above the EPA Region 6 SSL to the maximum
depth of exploration near the northeastern property boundary at the intersection of Geis
Street and Jefferson Avenue. PCE was detected below the Region 6 SSL at depths of 5 ft and
10 ft bgs at the eastern property boundary. TCE and other PCE degradation products were
detected primarily in samples collected near the northeastern property boundary. No VOCs
were detected in soil samples collected from the southeastern property boundary.
12.6.6 Soil Contamination at Work Shed
PCE and TCE were detected in soil samples collected on the north and south sides of a work
shed across Jefferson Avenue from the Allsup’s 200 gasoline station. These samples were
collected by NMED during the SI and identified PCE below the EPA Region 6 SSL, and TCE
above the Region 6 SSL, in samples from 1.5 ft bgs. Samples from 4 ft bgs also had
detectable PCE and TCE, but at concentrations below the EPA Region 6 SSLs.
12.7 Nature and Extent of Ground Water Contamination
This section of the ROD describes the nature and extent of ground water contamination at
the site. Ground water samples were collected using a direct-push drilling rig and existing
monitor wells present over portions of the plume (see Figure 7). Figures 9 and 10 show the
horizontal and the vertical extent of the chlorinated solvents contamination in ground water
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at the site. Horizontally, the plume extends from the two source areas to the south-
southeast approximately 1,500 ft. Vertically, the plume extends to a depth of at least 80 ft
bgs at the Holiday Cleaners source area.
The Holiday Cleaners was identified as the primary source of PCE in ground water during
the RI investigation. PCE emanating from the Holiday Cleaners follows a ground water
flow path to the southeast, gradually trending to the south-southeast beyond Geis Street.
PCE migrating along this flow path is transported within a thin silty-sand layer to a
maximum lateral extent of approximately 1,500 ft downgradient of the Holiday Cleaners,
with non-detect concentrations downgradient of this extent. The vertical extent of PCE
contamination at the site has not been completely established but will be determined during
a Pre-Design Field investigation.
PCE was detected in ground water in the parking lot of the Holiday Cleaners to a depth of
at least 55 ft bgs. PCE was detected across First Street from the Holiday Cleaners to a depth
of at least 80 ft bgs (the maximum depth explored at that location). In this boring, PCE was
detected at a maximum concentration of 3,400 µg/L (680 times the federal MCL [5 µg/L] for
ground water) at a depth of approximately 58 ft bgs.
PCE was detected at a concentration of 40,000 µg/L in well GMW-6 across First Street from
the Holiday Cleaners. PCE was detected at a maximum concentration of 51,000 µg/L (over
10,000 times the federal MCL) at sampling location DP-48, in the alley approximately 300 ft
downgradient of the Holiday Cleaners between First Street and Geis Street.
PCE was detected at high concentrations in ground water near the northeast corner of the
intersection of First Street and Jefferson Avenue. Based on ground water flow directions,
the source of this contamination would be suspected to be located at the northwest corner of
First Street and Jefferson Avenue, but both soil and ground water samples collected from
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this location have not detected chlorinated VOCs. The Holiday Cleaners is located
approximately 200 ft north on First Street, a location that is cross-gradient to the ground
water flow direction. As no other source is apparent, it is postulated that PCE and its
degradation products may be migrating preferentially within the coarse fill materials
surrounding a number of utilities (sewer, water, and gas) installed along First Street. Given
the very shallow depth to ground water, it is suspected that the utility trenches intersect the
ground water. These trenches are potentially providing a contaminant migration conduit
that transports contaminated ground water along the length of the trenches.
The work shed located across Jefferson Avenue from the Allsup’s 200 gasoline station may
be a source of PCE contamination in ground water, but high PCE detections within an
upgradient basement sump in the adjoining residential structure at the northeast corner of
First Street and Jefferson Avenue (2,300 µg/L) (NMED, 2001) suggests that the source of
ground water contamination is upgradient of the work shed, such as the utility trenches
along First Street.
Subsurface petroleum hydrocarbon contamination emanating from the Allsup’s 200
gasoline station at the intersection of First Street and Jefferson Avenue appears to be
enhancing the degradation of PCE at this location, resulting in the highest concentrations of
TCE, cis-1,2-DCE, and vinyl chloride (VC) detected at the GCSP Site.
The Abandoned Dry Cleaning Facility was identified as a second primary source of PCE
and its degradation products in ground water. A separate ground water PCE plume
emanates from this facility, extending laterally approximately 350 ft southeast of the
abandoned facility to just past the R&L Laundry across First Street. PCE was detected at a
maximum concentration of 1,600 µg/L (over 300 times the federal MCL) in a shallow
ground water sample collected from the southeast property boundary of the facility. PCE
was detected to a maximum depth of approximately 30 ft bgs near this same location during
the Phase 2 direct-push sampling event, and was non-detect at greater depths.
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12.8 Nature and Extent of Soil Vapor Contamination
Soil vapor samples were collected from locations surrounding several structures at which
vapor intrusion sampling also was conducted. Figure 8 presents the soil vapor and vapor
intrusion sampling locations and results. PCE and TCE concentrations were highest in
samples collected adjacent to structures 2 and 3, located across First Street from the Holiday
Cleaners. These structures also had the highest PCE and TCE vapor intrusion
concentrations. PCE was detected at a concentration of nearly 95,000 micrograms per cubic
meter (µg/m3) (and TCE was detected at a concentration over 857,000 µg/m3 adjacent to
structure 2 (closer to Holiday Cleaners). In general, significant concentrations of PCE and
its degradation products in soil vapor were only detected at locations within the known
lateral extent of PCE ground water contamination.
12.9 Nature and Extent of Indoor Air Contamination
Table 1 shows the criteria EPA used to evaluate indoor air data. Tier 3 action levels require
an evaluation of the need for mitigation measures to be implemented at the structure. Tier 2
action levels may require additional vapor intrusion monitoring and Tier 1 action levels do
not require any further action. Vapor intrusion (indoor air) samples collected at three
structures exceeded EPA Tier 3 PCE and TCE action levels within the GCSP Site (Figure 8).
Two of these structures are located across First Street from the Holiday Cleaners
(structures 2 and 3) and the third is located approximately 625 ft downgradient of the
Holiday Cleaners (structure 7). PCE and TCE concentrations in vapor intrusion samples
collected from structures 2 and 3 are significantly higher than at any other structure, and
approximately three times higher than detected at structure 7. These two structures are
currently unoccupied. In general, vapor intrusion samples collected from structures outside
the known lateral extent of shallow ground water contamination exhibit concentrations
below Tier 1 action levels (no further action is warranted). Structures overlying shallow
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ground water contamination typically exhibit concentrations above either Tier 2 (evaluate
whether additional sampling is warranted) or Tier 3 action levels.
12.10 Potential Routes of Contaminant Migration
Migration of contaminants at the GCSP Site occurs by means of several mechanisms,
including infiltration of water containing dissolved contaminants to shallow ground water,
DNAPL migration within the subsurface, volatilization of contaminants and migration as
subsurface soil vapor, and migration of dissolved contaminants within the ground water
aquifer.
12.10.1 Infiltration
Infiltration rates through the primarily silt and clay shallow subsurface are expected to be
relatively low. However, the very shallow depth to ground water (generally 5 to 7 ft bgs),
combined with the potential for an interconnected network of thin sand layers, may allow
infiltration of water containing dissolved contaminants to reach ground water within a
relatively short time period. Infiltration and distribution also would be facilitated within
utility trenches backfilled with coarse fill material. If PCE and its degradation products are
migrating through the sanitary sewer (due to potential disposal of water containing these
constituents at source areas), leakage of the sanitary sewer also would contribute to
enhanced infiltration and distribution of dissolved contaminants to ground water.
12.10.2 DNAPL Migration
The behavior of DNAPL in the subsurface is strongly affected by the nature and
heterogeneity of the subsurface media. When DNAPL is released to the unsaturated zone, it
can migrate downward, and capillary forces will immobilize some of the liquid in the pore
spaces as residual product. In lower permeability media (such as clays present in the
shallow subsurface of the GCSP Site), DNAPL may enter through micro-fracture networks
where dissolution and subsequent diffusive losses into the bulk matrix can occur. Pools of
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DNAPL also may form on top of lower-permeability media, be trapped within coarser
layers bounded by low permeability media (such as those observed at the GCSP Site), or
collect near the top of the capillary zone. This DNAPL can then begin to vaporize into the
gaseous phase and migrate by diffusion away from the source. Pressure or density
gradients can result in advective flow of the soil vapor, which can sometimes play a role in
the overall transport process. As they migrate, soil vapors will partition into the aqueous
phase (or dissolved phase) and the solid phase, tending to retard the rate of vapor
migration. Gaseous partitioning into the soil and water phases also will make contaminants
more readily available for aqueous transport.
Generally, the potential presence of DNAPL in or near the saturated zone is indicated if
concentrations in ground water exceed approximately 1 to 5 percent of chemical solubility
limits for the specified dissolved contaminant. The maximum detection of PCE in ground
water near the Holiday Cleaners is approximately 30 to 35 percent of the water solubility of
PCE, indicating that the presence of residual DNAPL is highly likely. These solubility levels
extend 700 ft downgradient of the Holiday Cleaners and 60 ft vertically in the Source Area.
12.10.3 Soil Vapor and Vapor Intrusion
VOCs present in the subsurface as a DNAPL, as dissolved aqueous-phase contamination,
and/or as residual soil contamination can volatilize into the vapor phase. Soil vapor may
migrate under the influence of pressure or density gradients, or by diffusion away from the
source. Advection of soil vapor from the unsaturated zone source areas is not considered
the primary source of vapor intrusion into the structures at the GCSP. Rather, local
volatilization from dissolved contaminants in shallow ground water, or DNAPL near the
source areas, are considered the primary source of soil vapor at any particular location at
the GCSP Site.
High concentrations of PCE and its degradation products present in soil vapor near
structures overlying the aqueous-phase contaminant plume may enter those structures by a
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number of means. Soil vapor may intrude through cracks in basements, into crawlspaces
beneath structures, or through cracks in structure foundations. Contaminants may then
collect within indoor air of the structure. At structure 3 at the GCSP Site, at the intersection
of First Street and Jefferson Avenue, an open sump in the basement allows for VOC
contaminants in the ground water in the sump to volatilize directly into indoor air.
12.10.4 Aqueous-Phase Transport
PCE migrates within the shallow ground water aquifer as dissolved PCE moving with
ground water flow. Shallow ground water at the GCSP Site moves preferentially through
thin, laterally extensive silty sand layers, with varying interconnectivity. A 6-inch to 1-ft
thick, laterally extensive sand layer was identified in numerous borings at the site, and is
shown in the cross sections presented in the RI Report. The lateral extent of sand and silty
sand layers within the deeper aquifer are currently unknown, but assumed to be similarly
extensive. Such sand layers are currently suspected to represent a primary migration
pathway for contaminants within the deeper aquifer.
The alluvial deposits of the shallow aquifer are known to contain thin laterally extensive
sand and silty sand layers and at least one thicker sand layer near GMW-1. These sand
layers act as the primary mechanism for lateral transport of contaminants within the
shallow aquifer. The interconnectivity of various sand layers within the alluvial deposits is
uncertain but would be a pathway for migration of contaminants from shallower to deeper
portions of the aquifer.
12.10.5 Potential Routes of Human Exposure
The exposure pathways identified for the GCSP Site are ground water exposure, soil and
exposure to vapor intrusion. As described in greater detail within the RI Report, ground
water exposure cannot be considered an incomplete pathway since property owners are not
legally prohibited from using the local ground water. Human exposure could occur
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through direct contact with shallow ground water through existing wells or excavation.
Chlorinated solvent contamination is not currently present in the Grants municipal water
supply wells, although the hydrogeologic interaction between the shallow alluvial aquifer
and the deeper regional ground water aquifer that serves as the municipal water supply has
not been investigated. Volatilization of the primary indicator constituents from the shallow
ground water surface provides an exposure pathway through vapor intrusion (indoor air).
A detailed discussion of potential exposure pathways is presented in EPA’s BHHRA,
included in the RI Report.
Potential exposure pathways from VOCs in soil are: (1) direct contact with soil (soil
ingestion, dermal contact, and inhalation of volatile emissions to outdoor air); and (2) vapor
intrusion from soil to indoor air. Vapor intrusion from soil has been addressed in part
through soil gas sampling and indoor air sampling. Further evaluation of potential direct
contact exposure pathways was conducted by comparison of total VOC results in soil with
NMED SSLs based on residential land use assumptions. The major chemicals of potential
concern (COPCs) in this evaluation were PCE and TCE.
The highest PCE concentrations in soil were found around Holiday Cleaners where PCE
concentrations were higher than the HHMSSL in selected samples. The total VOC
concentrations in soil, combined with the soil gas and indoor air data, suggest that VOCs in
soil potentially pose an unacceptable indoor air risk through vapor intrusion. In addition,
the highest PCE concentrations in soil (36 mg/kg and 21 mg/kg) are as much as 42 percent
of the soil saturation limit (calculated to be 85 mg/kg for a sandy soil), suggesting the
potential presence of DNAPL in some locations in soil. Therefore, while direct contact risks
potentially associated with VOCs in soil might not exceed risk reduction objectives (i.e.,
Excess Lifetime Cancer Risk [ELCR] of 1 x 10-5), soil remediation is warranted in the source
areas to address potential vapor intrusion risks and to address the presence of DNAPL in
soil as a continuing source of ground water contamination.
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12.11 Ground Water Flow and Transport Modeling
A simple preliminary ground water flow and transport model was constructed for the GCSP
Site using MODFLOW-SURFACT software, and available data collected during the RI. The
purposes of constructing the model were to gain a better understanding of the physical
characteristics of the aquifer and to provide an approximate timeframe for remediation of
the existing ground water contamination using various technologies (particularly pump and
treat), expected to be evaluated as part of the Feasibility Study. Many simplifying
assumptions were necessary within the ground water model due to the limited dataset
available following the RI. However, sufficient data were available to develop a
preliminary model to allow an evaluation of approximate pump-and-treat cleanup times.
The existing ground water model is anticipated to be substantially improved following
additional field investigation and data collection during a Preliminary Design Field
Investigation conducted during the RD. The expanded ground water model will be used
during the RD to evaluate selected treatment technologies and provide information
regarding expected time of remediation, dosing requirements, and other design components
for the selected remedial alternative(s).
Contaminant transport modeling was limited to a “forward-in-time” analysis due to a lack
of historical chemical time series data at the GCSP Site. The inability to model the historical
generation of the current contaminant distribution meant that a useful component of model
calibration could not be performed. However, the model was calibrated in part by adjusting
parameters until the model accurately represented the current downgradient and lateral
extent of ground water contamination using the current understanding of the time of
original release, and assuming continuous source areas.
Anticipated improvements to the preliminary ground water model include aquifer
pumping test data (rather than currently available slug test data) from several depth
intervals to provide more accurate representation of hydraulic aquifer properties, additional
lithology information to provide more accurate model layering, and additional depth
profiling of contaminants for more accurate representation of contaminant distribution. The
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installation of new permanent ground water monitoring wells also will provide improved
data on ground water flow directions and flow gradients within downgradient areas of the
contaminant plume.
13.0 Current and Potential Future Land and Resource Uses
13.1 Current and Potential Future Land Uses
Land use at the site currently includes mixed residential homes and commercial businesses.
Small businesses are mainly located along First Street and properties to the east are mostly
residential. A daycare facility is located at the corner of Monroe Avenue and Peek Street
and is just outside of the plume area. Other notable nonresidential structures within the
plume boundary are the Knights of Columbus building on Geis and Jefferson Avenue and a
bowling alley at the corner of Jefferson Avenue and Peek Street. To the east of the plume
boundary is an elementary school. Based on the history of the area the future land use is
unlikely to change from the current uses.
13.2 Current and Potential Future Ground Water Uses
The shallow ground water at the GCSP Site is currently not used by residents in the area.
However, owners are not legally prohibited from using the local ground water. The
drinking water source for the City of Grants is from two upgradient wells approximately
2 miles west (upgradient) of the Site. The City of Grants is planning to install an additional
supply well within 0.75 miles west of the Site. The interaction between the shallow aquifer
and the deeper aquifer is not well known at this time and will be the subject of investigation
prior to the design of the remedial alternatives for the GCSP Site. The future ground water
use at the Site is as a potential drinking water source for the City of Grants.
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14.0 Summary of Site Risks
This section of the ROD provides a summary of the Site's human health and environmental
risks. A BHHRA (EPA, 2005b) for the site was completed in July 2005, which estimated the
probability and magnitude of potential adverse human health and environmental effects
from exposure to contaminants associated with the Site assuming no remedial action was
taken. The BHHRA provides the basis for taking action and identifies the contaminants and
exposure pathways that need to be addressed by the remedial action.
14.1 Summary of Human Health Risk Assessment
The BHHRA followed a four-step process:
a. Hazard identification (identification of COCs)
b. Exposure assessment
c. Toxicity assessment
d. Risk characterization
The EPA used an exposure point concentration (EPC) for each COC and the reasonable
maximum exposure (RME) scenario to estimate risk. The EPC was the lesser of the
maximum detected concentration and the 95 percent upper confidence level (UCL) of the
arithmetic mean concentration of the COCs in soil or ground water. A 95 percent UCL is a
statistically derived value based on sample data within an exposure area. The RME scenario
is the maximum exposure that is reasonably expected to occur at the Site and is based on
"upper bound" and "central tendency" estimates. The use of multiple conservative exposure
factors makes the RME scenario protective of potential exposures.
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14.1.1 Identification of Chemicals of Concern
COCs are chemicals that pose a carcinogenic risk to human health greater than 1 in 1,000,000
(1 X 10-6), have a noncarcinogenic hazard index (HI) greater than (>) 1, or are found in site
ground water at concentrations that exceed MCLs. While various BTEX (benzene, toluene,
ethylbenzene, and xylene) compounds have been identified as COCs at the GCSP Site, they
are not targeted for cleanup under the CERCLA Remedial Action as they will be separately
addressed by the NMED-PSTB.
The following presents a summary of the evaluation and the constituents that are
considered to be COCs at the site:
14.1.1.1 Ground Water
The impacted shallow aquifer is not considered a source of drinking water for the city, but
the hydraulic interaction with the deep aquifer is of concern. The site is located within an
area served by a monitored public water supply system. City of Grants Ordinance No. 394
requires the “…mandatory connection of homes or other facilities within the City to the
public sewer and water system, and the City has the power to require such mandatory
connection…”.
An existing private well or a new private well could be used for drinking water in the
future. Also, the potential does exist for contamination to migrate from the shallow to the
deep aquifer and affect city water. The ground water pathway for the shallow aquifer is
therefore, considered complete for future use.
COPCs in ground water were identified by comparing the maximum detected chemical
concentrations in the wells to the following criteria:
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1. Federal MCLs and if no MCLS were available.
2. EPA Region 6 tap water maximum screening levels (MSLs) calculated with a target risk
of 1 x 10-6 for carcinogens and using a hazard index quotient (HQ) of 0.1 for
noncarcinogens.
Chemicals in ground water that were higher than EPA Region 6 tap water MSLs were
included as COPCs in the risk assessment. After the risk-based screen was completed, the
following chemicals were considered COPCs at the site: benzene; bromoform; cis-1,2-DCE;
ethylbenzene; MTBE; PCE; toluene; trans-1,2-DCE; TCE; VC; and total xylenes. Chemicals
in ground water that were detected at concentrations higher than MCLs were treated as
COCs. All the identified COPCs have MCLs with the exception of MTBE. Therefore, MTBE
was further evaluated in the risk assessment and found to pose a carcinogenic risk of 2x10-6
for future adult resident and 1 x 10-6 for future child resident. The risk from MTBE exposure
is within EPA risk range and hence it was excluded from the list of COCs for the site. Based
on this evaluation ground water COCs for the site are benzene bromoform, cis-1,2-DCE,
trans 1,2-DCE, PCE, TCE, vinyl chloride, and total xylenes.
14.1.1.2 Indoor Air COCs
Potential exposure pathways from indoor air could occur through vapor intrusion. The
process of vapor intrusion involves the migration of VOCs from ground water or subsurface
soil into overlying structures. In these structures, chemicals may accumulate to
concentrations that pose a risk of health effects from long-term exposure. Indoor air
sampling results were used to identify COPCs in indoor air, with an emphasis on
chlorinated solvents and BTEX.
Initially, the maximum concentrations detected in indoor air at any of the sampled locations
were compared with screening levels presented in EPA’s Draft Vapor Intrusion Guidance
(EPA 2002). These screening levels correspond to a 1 x 10-6 cancer risk or a noncancer HQ of
1 based on residential land use assumptions. If the maximum concentration of a chemical
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was lower than the screening level, it was excluded as a COPC. For chemicals that were
retained, a further screen was performed, evaluating COPCs on a structure-by-structure
basis. In this further screen, if the maximum concentration in an individual residence was
below the screening level, that chemical was not included as a COPC for that residence.
Uncertainties in the COPC selection process for indoor air include the presence of
background concentrations not associated with vapor intrusion. Direct measurement of
concentrations in indoor air also may detect VOCs from other indoor and outdoor sources,
such as household products (adhesives, paint, cleaners). In certain cases, COPCs identified
for a particular residence may actually be background levels from these other sources.
Including COPCs that may be background based potentially overstates risks associated with
the vapor intrusion pathway. Based on the evaluation the residential indoor air COCs for
the site are benzene, PCE, and TCE.
14.1.1.3 Soil COCs
The process of evaluating soil consisted of comparing detected concentrations of chlorinated
solvents and BTEX against NMED screening levels (SLs) for residential direct contact (RES)
and for the pathway from soil to ground water (SGW). These SLs are taken from NMED’s
Technical Background Document for Development of Soil Screening Levels, Revision 2.0 (February
2004) and are equivalent to either a carcinogenic risk of 1E-05 or a hazard quotient of 1, or to
an available MCL endpoint, in the case of the SGW pathway. In addition, for the SGW
pathway, the selected SLs correspond to a dilution-attenuation factor of 1, due to the
shallow water table.
The 2-ft depth interval was considered in the direct contact screen, and all three depth
intervals were considered in the SGW screen. In both cases, the highest detected
concentration for each chemical in the appropriate soil intervals throughout the site was
compared to its appropriate SL. If the chemical passed the screen, it was not considered
further in the process. Non-detects were included in the screen to highlight those chemicals
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with detection limits above their respective SLs. Based on this evaluation, there are no
COPCs for direct contact with the top 2 ft of soil. COPCs for the SGW pathway are PCE,
TCE, cis-1,2-DCE, and xylene. Soil COCs for direct residential contact at the site are PCE
and TCE.
Tables 2 and 3 (Summary of Chemicals of Concern and Medium-Specific Exposure Point
Concentrations for Ground Water and Soil; and Indoor Air) present the COCs and EPCs for
each of the COCs detected in ground water and/or indoor air.
14.1.2 Exposure Assessment
The objectives of the exposure assessment are to evaluate potential current and future
human exposures to COCs in all media of concern. The current and potential future human
receptors were determined by the site's configuration, land and water use, and activity
patterns. Receptors (adult/child) were identified for both current and potential future site
conditions. The receptors identified for quantitative analysis for the BHHRA are presented
in Table 4 (Selection of Exposure Pathways-Shallow Ground Water and Indoor Air), along
with a rationale for selecting the exposure pathways.
The CSM (Figures 4 and 5) shows the potential exposure pathways and human receptors at
the site. The CSM was developed based on local land and water use associated with the site.
Exposure pathways and routes identified for the site, and driving the remedial activities
specified in this ROD, are presented in Table 4 (Selection of Exposure Pathways) and are
based on the following:
a. Ground Water Exposure Pathway − Exposure to COCs in the shallow aquifer was
evaluated through ingestion, inhalation and dermal exposure routes for the future onsite
resident adult, child, and indoor worker.
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b. Indoor Air Exposure Pathway − Exposure to COCs in indoor air (via vapor intrusion)
through inhalation for the current/future adult and child residents and child attending
day care.
Mathematical models were used to calculate the intakes (i.e., the doses) of the COCs for each
receptor, using applicable exposure routes. The models used to calculate intakes are
presented in Tables 5 and 6. Each table defines the variables used in estimating doses and
includes the assumptions, known as exposure parameters, which are used in the model.
These parameters include variables, such as daily ingestion rate of water, exposure
duration, and body weight. In general, the exposure parameters that were used are
standard values recommended by national and EPA Region 6 guidance. Regardless of the
exposure route, the intake is presented as an estimated daily dose in units of milligrams of
chemical per kilogram of body weight per day (mg/kg-day).
14.1.3 Toxicity Assessment
Toxicity assessment is accomplished in two steps: hazard identification and dose-response
assessment. Hazard identification is the process of determining whether exposure to a
chemical is associated with a particular adverse health effect and involves characterizing the
nature and strength of the evidence of causation. The dose-response assessment is the
process of predicting a relationship between the dose received and the incidence of adverse
health effects in the exposed population. From this quantitative dose-response relationship,
toxicity values are derived that can be used to estimate the potential for adverse effects as a
function of potential human exposure to the chemical.
14.1.3.1 Carcinogenic and Noncarcinogenic Effects
Two general groups, carcinogens and noncarcinogens, categorize chemicals depending on
the types of effects on human health. Exposure to any substance in high enough doses can
result in toxic effects. Therefore, many carcinogens also produce known noncancer health
effects. Noncancer toxicity values (reference dose [RfD] and reference concentration [RfC])
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were used to evaluate the COCs present at the site in environmental media to determine the
noncancer toxic effects. Cancer slope factor (SF) was used to evaluate carcinogenic effects.
Tables 7 and 8 show the noncancer and cancer toxicity data for the COCs through oral,
dermal, and inhalation routes. The toxicity data were evaluated based on information from
Agency for Toxic Substances and Disease Registry (ATSDR), EPA’s Integrated Risk
Information System (IRIS) database, and National Center for Environmental Assessment
(NCEA) issue papers.
14.1.4 Risk Characterization
The risk characterization section of the ROD summarizes and combines outputs of the
exposure and toxicity assessments to characterize baseline risk at the site. Baseline risks are
those risks and hazards that the site poses if no action were taken.
14.1.4.1 Carcinogenic Risk
For carcinogens, risks are generally expressed as the incremental probability of an
individual developing cancer over a lifetime as a result of exposure to the carcinogen.
Excess lifetime cancer risk (ELCR) is calculated from the following equation:
ELCR = CDI x SF
where:
ELCR = a unitless probability (e.g., 2 x 10-5) of an individual developing
cancer
CDI = chronic daily intake averaged over 70 years, expressed as
mg/kg-day
SF = slope factor, expressed as (mg/kg-day)–1
These risks are probabilities that are expressed in scientific notation (e.g., 1 x 10-6). An ELCR
of 1 x 10-6 indicates that an individual experiencing the Reasonable Maximum Exposure
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(RME) estimate has a 1 in 1,000,000 chance of developing cancer as a result of site-related
exposure. This is referred to as an ELCR because it would be in addition to the risks of
cancer individuals face from other nonsite-related causes such as smoking or exposure to
too much sun. The chance of an individual developing cancer from all other causes has
been estimated to be as high as 1 in 3. The EPA's generally acceptable risk range for site-
related exposures is 1.0 x 10-4 to 1.0 x 10-6, or a 1 in 10,000 to 1 in 1,000,000 chance,
respectively, of an individual developing cancer.
Tables 9 and 10 present summaries of cancer risk and noncancer hazards to receptors due to
contact with COCs in shallow ground water, as well as inhalation of indoor air due to vapor
intrusion. The RME scenario is used as the basis for decision at the Site.
14.1.4.2 Noncarcinogenic Risk
For noncarcinogens (systemic toxicants), potential effects are evaluated by comparing an
exposure level over a specified time period (e.g., exposure duration) with a RfD derived for
a similar exposure period. An RfD represents a level that an individual may be exposed to
that is not expected to cause any harmful effect. The ratio of exposure to toxicity is called a
hazard quotient (HQ). An HQ of less than 1 indicates that a receptor's dose of a single
contaminant is less than the RfD, and that toxic noncarcinogenic effects from that chemical
are unlikely. The HI is generated by adding the HQs for all COCs that affect the same target
organ (e.g., liver) or that act through the same mechanism of action within a medium or
across all media to which a given individual may reasonably be exposed. An HI of less than
1 indicates that, based on the sum of all HQs from different contaminants and exposure
routes, toxic noncarcinogenic effects from all contaminants are unlikely. An HI greater than
1 indicates that site-related exposures may present a risk to human health. The HQ is
calculated as follows:
Non-cancer HQ = CDI/RfD
where:
HQ = hazard quotient (unitless)
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CDI = chronic daily intake (mg/kg-day)
RfD = reference dose (mg/kg-day)
14.1.5 Uncertainties
Some level of uncertainty is introduced into the risk characterization process every time an
assumption is made. In regulatory risk assessment, the methodology dictates that
assumptions err on the side of overestimating potential exposure and risk. The effect of
using numerous assumptions that each overestimate potential exposure provides a
conservative estimate of potential risk.
The large number of assumptions made in the risk characterization could potentially
introduce a great deal of uncertainty. Any one individual's potential exposure and
subsequent potential risk are influenced by their individual exposure and toxicity
parameters and will vary on a case-by-case basis. Understanding the uncertainties in the
assessment should result in decisions that are more informed.
At least three sources of uncertainties exist in the BHHRA:
• Uncertainty around environmental data
• Uncertainty around exposure assumptions
• Uncertainty related to toxicity assumptions
14.1.5.1 Uncertainty In Environmental Data
A sampling plan is used to determine and evaluate the full nature and extent of
contamination to support the analysis. The sampling plan in turn relies on known site data
to determine sampling locations. In addition, seasonal variation of concentrations may
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occur because of fluctuations in the water levels, and sampling and analytical procedures
are likely to introduce variability. At the GCSP Site, ground water locations were sampled
for chlorinated solvents from numerous wells and direct-push borings. Therefore,
concentration of organic chemicals are likely to be representative of fluctuations expected in
ground water and unlikely to contribute to any systemic bias of the results.
Indoor air samples were collected at least twice from most homes to account for seasonal
variability, but in a few cases, only one sample was collected. A single detected value is not
likely representative of indoor air concentration. Additionally, measured values in indoor
air were attributed solely to vapor intrusion and not to any other indoor source. This may
overestimate the risk from vapor intrusion in the homes. Finally, benzene, which was
detected in ambient outdoor air, also can produce elevated contaminant concentrations in
indoor air not related to vapor intrusion. Possible outdoor air sources of benzene include
motor vehicle emissions and emissions from a nearby gasoline service station.
14.1.5.2 Uncertainty in Exposure Assumptions
A number of uncertainties are associated with assumptions made in the exposure
assessment. Areas of uncertainty include the calculation of intakes and the selection of
exposure parameters. Uncertainties regarding exposure assumptions result from the
variability of the different parameters, such as ingestion rates and exposure durations both
within and across populations. Best estimates from data sources compiled by regulatory
agencies were used in assessing potential exposures. How well these assumptions fit the
community is unknown. The 95th percentile values from the exposure ranges were
incorporated into the exposure assumptions to make the assessment more reflective of
community demographics. Assumptions of resource use patterns may have included
unlikely scenarios, or conversely, missed likely uses. In any case, because of the use of the
95th percentile values and conservative assumptions for potential exposures reflected in the
RME, the BHHRA should provide a reasonable estimate of risk.
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14.1.5.3 Uncertainty in Toxicity Assumptions
Assumptions of toxicity at expected exposure doses were based on unit exposure values
determined by regulatory agencies. Because of uncertainties in the studies used in
determining toxicity, single to multiple order-of-magnitude adjustments were made in the
process of determining safe exposure levels. Therefore, it is anticipated that the values will
tend to overestimate expected toxicity at a given level of exposure.
Multiple chlorinated solvents may act on similar target organs and systems to produce
similar toxic responses. Additivity of responses is assumed, but it is unknown if straight
additivity is a valid assumption. Synergistic, or more than additive, responses might occur
with exposure to multiple contaminants acting on similar tissues. This potential is
somewhat balanced by the assumption that co-exposures to the highest levels of all
contaminants would occur. In reality, the composition of the plume changes with distance
from the source as PCE degrades into its breakdown products, which increase in relative
concentration. It is, therefore, difficult to predict the net effect of these predicted
interactions on risk values.
In addition, BTEX present within portions of the site might have synergistic or additive
effects if co-exposures occurred. BTEX is co-located with the chlorinated solvents in
portions of the plume, so there is a possibility that co-exposures could occur. Laboratory
data are generally difficult to find on chemical-chemical interactions because of the limitless
combinations of exposure concentrations and difficulties in interpretation for even the best-
designed studies.
Finally, although there may be sensitive subsets of the population at the site, the toxicity
reference values incorporate uncertainty factors that should be protective of these sensitive
subpopulations. Combined with the RME exposure assumptions, the net result of the
evaluation should be protective of those members of the population.
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14.2 Ecological Risk Assessment
An ecological risk assessment was not performed for the GCSP Site, primarily due to the
volatility of the contaminants. VOCs do not normally persist in surface media that would
be considered for ecological risk – namely, surface soil and surface water. Concurrent with
the planning phase of the RI, EPA and NMED collected water samples from eight locations
along the Rio San Jose to investigate the shallow ground-water/surface-water interface
(hyporheic zone) in the vicinity of the GCSP Site. PCE was not detected in these samples;
however, 1,1-Dichloroethane (1,1-DCA) and cis-1,2-DCE were detected in four of the
samples, and TCE was detected in one of the samples. All detected concentrations were less
than their respective MCLs. All detected concentrations also were less than ecological
screening values for fresh water available from various state agencies. It does not appear
that these chlorinated VOC compounds in the hyporheic zone are related to the primary
release locations identified during the SI or RI. The presence of these compounds indicates
that chlorinated solvents are entering the Rio San Jose from another undefined source,
potentially near First Street, and the concentrations are well below levels that would
indicate a concern for ecological receptors.
14.3 Basis for Remedial Action
The response action selected in this ROD is necessary to protect the public health or welfare
or the environment from actual releases of hazardous substances into the environment. The
response action is warranted because:
1. The ground water COCs are present in concentrations above their MCLs; therefore, they
present an unacceptable risk to human health and the environment.
2. The shallow aquifer that is contaminated will continue to pose vapor intrusion risk to
residents.
3. The indoor air COCs present either a carcinogenic risk greater than 1 x 10-5 or a
noncarcinogenic HQ greater than 1.
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15.0 Remedial Action Objectives
The Remedial Action Objectives (RAOs) provide general descriptions of what the
Superfund cleanup is designed to accomplish. The RAOs are established on the basis of the
nature and extent of the contamination, the resources that are currently and potentially
threatened, and the potential for human and environmental exposure. The remedial goals
are media-specific, quantitative goals that define the extent of cleanup required to achieve
the RAOs. These goals serve as the design basis for the Selected Remedy identified in this
ROD.
15.1 Remedial Action Objectives for Ground Water
RAOs, remediation goals, and remediation strategies developed for the GCSP Site assume
that the GCSP Site consists of residential and commercial properties, and will continue to
consist of residential and commercial properties for the foreseeable future. The GCSP Site
remedy will address affected residential exposure pathway. The RAOs for ground water at
the GCSP Site are:
• Protect human health from exposure to chemical constituents in concentrations above
MCLs or Applicable or Relevant and Appropriate Requirements (ARARs).
• Restore the ground water at the GCSP Site such that it contains concentrations of the
COCs less than the applicable MCLs or ARARs in a timely manner.
• Prevent DNAPL, if present, from causing concentrations of COCs in ground water to
exceed MCLs or ARARs.
• Reduce the concentration of COCs in ground water to mitigate vapor intrusion.
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15.2 Remedial Action Objectives for Soil
The RAOs for the soil at the GCSP Site are:
• Prevent the ground water from being impacted above MCLs through transport of COCs
from the unsaturated zone.
• Protect human health from exposure to chemical constituents in soil.
• Reduce the concentration of COCs in soil and soil vapor to mitigate the vapor intrusion
pathway.
15.3 Remedial Action Objectives for Vapor Intrusion
The RAO for vapor intrusion at the GCSP Site is:
• Prevent vapor intrusion into structures that results in human exposure to vapor-phase
COCs in excess of a 10-5 ELCR.
15.4 Basis and Rationale for Remedial Action Objectives
The basis for the RAOs for the ground water and soil is to clean up the site to residential
standards, the current and anticipated future land use for the site. The chlorinated solvents
in ground water are present above ARARs and have migrated beneath residential
properties. There are no prohibitions that prevent the use of the shallow ground water
contaminated by the chlorinated solvent plume. Although currently no one is exposed to
contaminated ground water in the shallow aquifer, the risk is unacceptable as the future use
of ground water in the area is potentially drinking water. It is EPA’s policy to take action at
ground water contaminated sites when contaminants exceed MCLs. Remedial Actions at
the GCSP Site are expected to reduce the chlorinated solvent concentrations to less than
MCLs and the New Mexico Water Quality Control Commission (WQCC) standards. The
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Remedial Action in the source area will address DNAPL, the principal threat waste and
eliminate the source for contamination and restore soil and ground water. The Remedial
Action in the remaining portion of the site will address any DNAPL present and restore
ground water to drinking water standards and remove vapor intrusion risk to residents in
the area.
Within the source areas at the GCSP Site, concentrations of COCs in ground water are
believed to be caused in part by residual PCE in soil. The soil RAOs are intended to address
the residual COCs in soil as part of the Selected Remedy. COCs in soil will be treated or
removed to prevent soil contamination from being a continuing source of unacceptable
dissolved- and vapor-phase COCs.
COCs have been identified in soil within source areas at the GCSP Site. Exposure to local
residents near the source areas and to construction workers working within the source areas
are of concern. The Remedial Action is intended to reduce the concentrations of COCs such
that potential exposure to the COCs at concentrations that exceed target risk levels will be
prevented. Once the COCs are no longer present in the soil at the source areas, the pathway
to the vapor phase will no longer be complete, thus preventing impact to indoor air in
adjacent residential structures.
Vapor-phase COCs from ground water and soil vapor intrusion are present in residential
structures within the GCSP Site at concentrations that exceed the target indoor air risk
levels. The Remedial Action addressing vapor intrusion in homes is intended to provide a
remedy to remove the completed pathway for the COCs to indoor air.
15.5 Risks Addressed by the Remedial Action Objectives
Implementing active remedies in the source area, shallow plume core and hot spot, shallow
plume periphery and deeper plume will address the risks associated with chlorinated
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solvents in ground water at the site. PCE concentrations vary from a high of 51,000 µg/L in
the plume core to 1,000 µg/L in the plume periphery. Implementation of the Selected
Remedy is expected to reduce the concentrations of chlorinated solvents in ground water to
safe drinking water standards. The cancer risk of 2 x 10-3 associated with inhalation of
vapors in three residences will be addressed by installing vapor mitigation system in homes.
The vapor mitigation systems are anticipated to reduce the cancer risk to below the
acceptable level of 1 x 10-5. The EPA’s decision to install an additional eleven homes with
vapor mitigation system will ensure any future risks for these residences do not exceed the
1 x 10-5 risk level.
16.0 Description of Alternatives
The following are the alternatives that EPA reviewed for each site-impacted area:
Indoor Air Alternatives
• Alternative 1 − No Action
• Alternative 2 − Vapor Mitigation (Selected Alternative)
Source Area Treatment Alternatives
• Alternative 1 − No Action
• Alternative 2 − Thermal Treatment (Selected Alternative)
• Alternative 3 – ISCO w/Follow-On ERD
• Alternative 4 – ERD (Gridded)
Shallow Plume Core and Hot Spot
• Alternative 1 – No Action
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• Alternative 2 – Zero-Valent Iron (ZVI) Permeable Reactive Barrier (PRB)-Multiple
Transects
• Alternative 3 – ISCO w/Follow-On ERD (Selected Alternative)
• Alternative 4 − ERD (Bio-Barrier)
• Alternative 5 – Pump and Treat
Shallow Plume Core Periphery
• Alternative 1 – No Action
• Alternative 2 – Monitored Natural Attenuation (MNA)
• Alternative 3 – ZVI PRB-Multiple Transects
• Alternative 4 – ERD (Bio-Barrier) (Selected Alternative)
• Alternative 5 – Pump and Treat
Deeper Ground Water
• Alternative 1 − No Action
• Alternative 2 − Monitored Natural Attenuation (MNA)
• Alternative 3 − ZVI PRB-with Deep ERD
• Alternative 4 − ERD (Bio-Barrier) (Selected Alternative)
• Alternative 5 − Pump and Treat
16.1 Common Elements of Each Remedial Component
This section of the ROD describes those components that are common to each of the
remedial alternatives except the No Action Alternative. Common remedial components to
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all or most of the remedial alternatives include the need for a Preliminary Design Field
Investigation to collect site-specific data for the RD, a ground water monitoring program,
and Five-Year Reviews.
16.1.1 Preliminary Design Field Investigation
Additional field work is required at the GCSP Site prior to the RD to collect essential site
data for final design of the selected treatment alternatives. Monitoring wells were not
installed as part of the RI and the current extent of the PCE ground water plume is based on
direct-push sampling results. Sufficient soil sampling to fully delineate the horizontal and
vertical extent of DNAPL and soil contamination in source areas was not performed during
the RI and the current extent of soil contamination above Preliminary Remedial Goals (RGs)
is unknown.
The Preliminary Design Field Investigation will provide a network of monitoring wells to
enable the complete horizontal and vertical delineation of PCE in ground water, particularly
at depths below 20 ft bgs. The wells will allow for continued monitoring of VOC
concentrations throughout the plume. The Preliminary Design Field Investigation will
perform additional soil and ground water sampling within the two source areas identified
during the RI, the Holiday Cleaners and the Abandoned Cleaners, and will assess the source
areas for the presence of DNAPL.
Additional lithologic characterization will be performed to better define the CSM, and
aquifer testing will be conducted within several of the new ground water monitoring wells.
Other aquifer properties specific to the treatment technologies included within the Selected
Alternative will also be evaluated, including soil oxidant demand, sulfate concentrations in
ground water, and sustainable injection rates. The additional data collected during the
Preliminary Design Field Investigation will be vital to developing the final design(s) for the
selected remedial alternatives.
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16.1.2 Ground Water Monitoring Program
Ground water sampling will be required as part of the Remedial Action for treatment of
various aspects of the GCSP Site. To confirm that treatment goals are being met, a period of
40 years of ground water sampling and monitoring is anticipated to track the progress of the
treatment alternatives. The ground water sampling program will be fully developed during
the RD, and will include an exit strategy for discontinuing the program if the RAOs are met
before the end of the sampling period.
It is assumed that approximately 36 monitoring wells will be installed during the
Preliminary Design Field Investigation and the six existing NMED monitoring wells will
serve as the monitoring well network and will adequately monitor the overall progress of
the Remedial Action, track the reduction of concentrations within the sitewide plume, and
allow monitoring of the potential migration of contaminants. Ground water monitoring at a
minimum will be conducted semi-annually for the first 5 years after remedy construction is
complete and annually thereafter unless otherwise determined in consideration of site
conditions.
16.1.3 Five-Year Reviews
Five-Year Reviews will be required at the GCSP Site since varying amounts of
contamination will remain onsite that would prohibit unlimited and unrestricted use.
Five-Year Reviews will be conducted until restoration goals are met, anticipated to take
about 40 years.
16.1.4 Institutional Controls
To protect human health from the existing ground water contamination while cleanup is
ongoing, the EPA and NMED will request the New Mexico Office of State Engineer (OSE) to
issue an order restricting future well drilling within a portion of the aquifer contaminated
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by the plume until remediation goals for the ground water are met. The order will only
apply to new requests for water well permits and cannot be enforced against existing water
well permit holders. The OSE does not have a vested enforcement authority but has the
ability to enforce with a court order. The EPA will work with NMED to issue a health
advisory not to consume ground water from the existing wells within the plume area.
16.2 Distinguishing Features of Each Alternative
16.2.1 Indoor Air Alternatives
Concentrations of PCE and/or TCE currently exceed the RGs for indoor air at
three residential structures at the GCSP Site. The alternatives selected for evaluation for
treatment of indoor air at the GCSP Site are no action or the installation of radon-type vapor
mitigation systems.
16.2.1.1 Alternative 1: No Action
Estimated Time for Design/Construction: Not applicable
Estimated Time to Reach Remediation Goals: Not applicable
Estimated Capital Cost: $ 0
Estimated Life Time O&M Costs: $ 0
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 0
Numbers of Years Cost Is Projected: Not Applicable
The No Action Alternative is included as a baseline for evaluation of the other remedial
alternatives, as required by the NCP. Under Alternative 1, no remedy will be implemented
and indoor air at these structures would continue to exceed the RGs such that the RAOs for
indoor air would not be met.
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16.2.1.2 Alternative 2: Vapor Mitigation
Estimated Time for Design/Construction: Less than 1 year
Estimated Time to Reach Remediation Goals: Less than 1 year
Estimated Capital Cost: $ 425,000
Estimated Life Time O&M Costs: $ 6,500
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 331,500
Number of Years Cost Is Projected: 20 years
Under Alternative 2, the EPA will install vapor intrusion mitigation systems at residential
structures where concentrations of PCE and/or TCE currently exceed the RGs for indoor air.
In addition, EPA will install vapor mitigation systems in additional residences that are
located directly above the ground water plume where concentrations of TCE or PCE exceed
1,000 µg/L. The EPA is taking this additional step to eliminate future risks to residents that
live directly above the most affected portion of the plume. The systems would be installed
in those residential structures shown in Figure 11. Following is a listing and description of
the remedy components for Alternative 2:
Vapor Intrusion
1. Treatment Components. Vapor mitigation systems do not treat indoor air but rather
prevent vapor intrusion. There is no treatment component for this alternative.
2. Containment Components. Vapor intrusion mitigation systems would be
functionally similar to radon mitigation systems and consist of placing a plastic liner
between the ground surface and the residential living space for residences with
crawlspaces, and ventilating between the liner and the ground surface to remove
vapors before they can enter the living space. Currently, only three residences
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exceed RGs for indoor air. However, EPA is proposing to install vapor intrusion
mitigation systems at 14 residences that are located directly above the ground water
plume where concentrations of TCE or PCE in ground water exceed 1,000 µg/L and
indoor air concentrations exceed a 1 x 10-5 risk level.
3. Operations and Maintenance Components. Once installed, the relatively low
electrical costs to run the system will be the responsibility of the homeowner.
NMED will pay for any replacement parts and installation within the mitigation
system during the life of the system.
4. Monitoring Components. Vapor mitigation systems have proven to be very reliable
and robust across the country. However, EPA will conduct monitoring prior to
construction and after construction to verify effectiveness of the system. EPA may
choose to monitor at least once every 5 years during the Five-Year Review cycle to
establish protectiveness of the remedy.
16.2.2 Source Area Alternatives
The EPA evaluated the following five alternatives for treating the source area soil and
ground water at the GCSP Site. Approximately a total of 47,556 cubic yards (yd3) of aquifer
matrix in the primary and secondary source areas is targeted for treatment in the Source
Area.
16.2.2.1 Alternative 1: No Action
Estimated Time for Design/Construction: Not applicable
Estimated Time to Reach Remediation Goals: Not applicable
Estimated Capital Cost: $ 0
Estimated Life Time O&M Costs: $ 0
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 0
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Number of Years Cost Is Projected: Not Applicable
The No Action Alternative is included as a baseline for evaluation of the other remedial
alternatives, as required by the NCP. Under Alternative 1, no remedy will be implemented
and source areas will not meet RAOs for the site.
16.2.2.2 Alternative 2: Thermal Treatment
Estimated Time for Design/Construction: Less than 1 year
Estimated Time to Reach Remediation Goals: 2 years
Estimated Capital Cost: $ 8,018,000
Estimated Life Time O&M Costs: Not Applicable
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 8,018,000
Number of Years Cost Is Projected: 1 year
Soil Contamination
1. Treatment Components. Approximately a total of 47,556 yd3 of aquifer matrix in the
primary and secondary source areas is targeted for treatment using an in-situ
thermal remediation system. The treatment is targeted to address principal threat
wastes in the soil and ground water in the source areas. Treated soils are left in
place and not excavated in this alternative. Thermal treatment utilizes soil vapor
extraction as a principal component of the technology, which will provide treatment
of unsaturated soils at the source areas. Given the high concentrations in the source
area, thermal treatment would need to achieve 99.9 percent or more removal rate to
meet the final clean up goals. After completion of thermal treatment, a final
polishing step requiring additional treatment via an alternative technology may be
required to treat any remaining low-level wastes.
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2. Operation and Maintenance Components. Active treatment using the thermal
technology is anticipated to require less than 1 year of system operation once
constructed. There are no long-term operations and maintenance costs for this
technology.
3. Monitoring Components. Performance monitoring would be conducted throughout
the active thermal treatment period and during the cool-down period following
treatment, and includes monitoring of ground water concentrations and subsurface
temperatures.
Ground Water Contamination
1. Treatment Components. Approximately a total of 47,556 yd3 of aquifer matrix in the
primary and secondary source areas is targeted for treatment using an in-situ
thermal remediation system. The treatment is targeted to address principal threat
wastes in the soil and ground water in the source areas. Thermal treatment raises
the temperature of the subsurface to approximately 100 degrees Celsius, inducing
volatilization and boiling of chlorinated solvents and steam flushing of the aquifer.
Steam and volatilized vapors are collected within an integral soil vapor extraction
system. Given the high ground water concentrations in the Holiday Cleaners source
area, thermal treatment would need to achieve a 99.9 percent or more removal rate
to meet the RGs. If RGs are not met following completion of thermal treatment, a
final polishing step requiring additional treatment via an alternative technology may
be required to treat any remaining low-level wastes.
2. Operation and Maintenance Components. Active treatment using the thermal
technology is anticipated to require less than 1 year of system operation once
constructed. There are no long-term operations and maintenance costs for this
technology.
3. Monitoring Components. Performance monitoring would be conducted throughout
the active thermal treatment period and during the cool-down period following
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treatment, and includes monitoring of ground water concentrations and subsurface
temperatures.
16.2.2.3 Alternative 3: ISCO with Follow-On ERD
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 7years
Estimated Capital Cost: $ 6,257,000
Estimated Life Time O&M Costs: $ 3,179,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 9,436,000
Number of Years Cost Is Projected: 8 years
Soil Contamination
1. Treatment Components. Approximately a total of 47,556 yd3 of aquifer matrix in the
primary and secondary source areas is targeted for treatment using ISCO with
follow-on ERD. In this alternative a total of approximately 638 yd3 of soil would be
excavated from the primary and secondary source areas. Excavated soil would be
disposed of as either hazardous or nonhazardous waste depending on soil sampling
data.
2. Operation and Maintenance Components. There are no operations and
maintenance components associated with the initial soil excavation.
3. Monitoring Components. Monitoring of ground water generated from the initial
soil excavation would be conducted prior to discharge.
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Ground Water Contamination
1. Treatment Components. Following excavation of soils, ISCO with follow-on ERD
would be applied to treat ground water and saturated soils. In-situ chemical
oxidation is effective for rapid mass reduction within source areas and high-
concentration portions of ground water plumes. ERD is a slower process, but has
the advantage of being a potentially more technically- and cost-effective method of
reliably reaching MCLs when COC concentrations are moderate (i.e., DNAPL is
absent). The strengths of ISCO and ERD can be combined for treatment of source
areas. In addition to ISCO with follow-on ERD, up to 100,000 gallons of PCE-
contaminated ground water may be removed from the initial soil excavations during
this period. Extracted ground water would be treated onsite and disposed either in
the Rio San Jose channel, the sanitary sewer or reinjected back in to the aquifer.
2. Operations and Maintenance Components. Five carbon source amendment
injections would occur once every 15 months following the soil excavation and ISCO
treatment. ERD injections would occur in the same permanent injection wells used
for ISCO.
3. Monitoring Components. Performance monitoring would consist of direct-push
sampling to confirm the distribution of oxidants and carbon amendments within the
subsurface, and ground water sampling during, and upon completion of, the active
treatment period.
16.2.2.4 Alternative 4: ERD (Gridded)
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 15 years
Estimated Capital Cost: $ 2,391,000
Estimated Life Time O&M Costs: $ 6,074,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 8,465,000
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Number of Years Cost Is Projected: 15 years
Soil Contamination
1. Treatment Components. Alternative 4 is similar to Alternative 3. A total of
approximately 470 yd3 of soil would be excavated from the primary and secondary
source areas. Excavated soil would be disposed of as either hazardous or
nonhazardous depending on soil sampling data.
2. Operation and Maintenance Components. There are no operations and
maintenance components associated with the initial soil excavation.
3. Monitoring Components. Monitoring of ground water generated from the initial
soil excavation would be conducted prior to discharge.
Ground Water Contamination
1. Treatment Components. Following excavation, ERD would be applied to treat the
ground water and saturated soils. ERD is a slower process, but has the advantage of
being a potentially more technically- and cost-effective method of reliably reaching
MCLs when COC concentrations are moderate (i.e., DNAPL is absent). In addition,
up to 100,000 gallons of PCE-contaminated ground water may be removed from the
initial soil excavation. Extracted ground water would be treated onsite and disposed
either in the Rio San Jose channel, the sanitary sewer, or reinjected back in to the
aquifer.
2. Operations and Maintenance Components. Twelve carbon source amendment
injections would occur once every 15 months following the soil excavation.
3. Monitoring Components. Performance monitoring would consist of direct-push
sampling to confirm the distribution of carbon amendments within the subsurface,
and ground water sampling during, and upon completion of, the active treatment
period.
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16.2.3 Shallow Plume Core and Hot Spot Alternatives
Alternative 1: No Action
Alternative 2: ZVI PRB-Multiple Transects
Alternative 3: ISCO w/Follow-On ERD
Alternative 4: ERD (Bio-Barrier)
Alternative 5: Ground Water Extraction and Ex-Situ Treatment
16.2.3.1 Alternative 1: No Action
Estimated Time for Design/Construction: Not applicable
Estimated Time to Reach Remediation Goals: Not applicable
Estimated Capital Cost: $ 0
Estimated Life Time O&M Costs: $ 0
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 0
Number of Years Cost Is Projected: Not Applicable
The No Action Alternative is included as a baseline for evaluation of the other remedial
alternatives, as required by the NCP. Under Alternative 1, no remedy would be
implemented and the shallow ground water plume core and hot spot would not meet RAOs
for the site.
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16.2.3.2 Alternative 2: ZVI PRB
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 4,937,000
Estimated Life Time O&M Costs: $ 837,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 5,744,000
Number of Years Cost Is Projected: 40 years
Ground Water Contamination
1. Treatment Components. A total of approximately 140 million gallons (MG) is
estimated to be impacted with chlorinated solvents contamination. A portion of the
impacted aquifer would be treated with this approach. PRB walls incorporating ZVI
provide passive treatment of contaminants as ground water flows through the wall
under natural ground water flow gradients. A total of approximately 600 ft of
ZVI-PRB walls would be installed as multiple transects across the shallow plume
core and at the downgradient extent of the shallow ground water hot spot. Under
this scenario, the ZVI-PRB wall transects would be spaced approximately 150 to
200 ft apart along the length of the shallow plume core. The ZVI-PRB walls would
be installed using slurry trenching techniques, where a biodegradable slurry is
maintained within the trench during excavation to stabilize the trench. The material
excavated during installation of PRB walls would require offsite disposal.
2. Operation and Maintenance Components. The service life of the PRB wall is
expected to be 20 years. At the end of the 20-year life cycle, a new PRB wall would
be installed to replace the existing wall.
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3. Monitoring Components. Performance monitoring would be conducted during the
active treatment period to evaluate the effectiveness of the system.
16.2.3.3 Alternative 3: ISCO with Follow-On ERD Bio-Barrier
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 8 years
Estimated Capital Cost: $ 4,444,000
Estimated Life Time O&M Costs: $ 2,287,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 6,731,000
Number of Years Cost Is Projected: 8 years
1. Treatment Components. In-situ chemical oxidation is effective for rapid mass
reduction within source areas and high concentration portions of ground water
plumes. ERD is a slower process, but has the advantage of being a more technically
and potentially cost-effective method of reliably reaching MCLs when COC
concentrations are moderate (i.e., DNAPL is absent). The strengths of ISCO and
ERD can be combined for treatment of the shallow ground water plume core and hot
spot. ISCO is initially applied to rapidly lower dissolved-phase COC concentrations
to moderate levels. The ISCO phase is then followed by injecting carbon source
amendments (ERD) as a polishing step for final reduction of COCs.
2. Operation and Maintenance Components. After the initial application of ISCO, a
total of five ERD applications would occur once every 15 months to treat the COCs.
3. Monitoring Components. Performance monitoring would consist of direct-push
sampling to confirm the distribution of oxidants and carbon amendments within the
subsurface, and ground water sampling, during, and upon completion of, the active
treatment period.
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16.2.3.4 Alternative 4: ERD Bio-Barrier
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 20 years
Estimated Capital Cost: $ 576,000
Estimated Life Time O&M Costs: $ 1,300,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 1,876,000
Number of Years Cost Is Projected: 20 years
1. Treatment Components. Treatment of the shallow ground water plume core and
hot spot would be performed using ERD in the form of injected carbon source
amendment barriers, called bio-barriers. Bio-barriers are installed as transects across
the ground water plume axis by closely spaced injection of carbon source
amendments. Within these carbon-rich zones, or barriers, biologically mediated
reductive dechlorination of the COCs is enhanced and the process forms a
continuous ERD treatment zone to intercept the plume. Installation of multiple
bio-barriers in series achieves RAOs as ground water passes through each treatment
area. Injection points along each transect will be spaced approximately 25 ft apart
with an assumed injection radius of influence (ROI) of approximately 15 ft.
Permanent injection wells would be installed, as they would be cost effective due to
the need for multiple injections of carbon source amendments over an extended time
period to meet RAOs. Each injection well will be screened from 8 ft bgs to 20 ft bgs
for treatment of shallow plume core and hot spot. Bio-barriers would be installed as
multiple transects across the shallow plume core and hot spot, with an assumed total
bio-barrier length of approximately 600 ft. Under this scenario, the bio-barriers
would be spaced approximately 150 to 200 ft apart along the length of the shallow
plume core, with short bio-barriers installed across the shallow hot spot.
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2. Operation and Maintenance Components. A total of 16 ERD applications would
occur once every 15 months to treat the COCs.
3. Monitoring Components. Performance monitoring would be conducted by
installing and sampling up to 10 ground water monitoring wells on either side of
various bio-barriers to determine the effectiveness of the treatment technology, and
to track overall progress during the active treatment period. Semi-annual sampling
will be conducted during the course of active treatment.
16.2.3.5 Alternative 5: Ground Water Extraction and Ex-Situ Treatment
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 3,539,000
Estimated Life Time O&M Costs: $ 9,970,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 13,509,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. Under this alternative, a network of extraction wells
would be located within the shallow plume core and hot spot. Due to the shallow
depths targeted for treatment, dual-phase extraction is anticipated. Dual-phase
extraction involves the installation of extraction wells screened both below and
slightly above the ground water table and application of vacuum to the wells to
extract both soil vapor and ground water. With dual-phase extraction, relatively
high extraction rates are used to actively dewater the upper portions of the shallow
aquifer. This dewatering provides for rapid removal of highly contaminated ground
water and exposes additional vadose zone for soil vapor extraction (SVE).
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Extracted soil vapor and ground water would be conveyed to a central treatment
plant where ex-situ treatment would include two treatment trains, one for extracted
soil vapor and one for extracted ground water. Soil vapor would be directed
through a granular activated carbon (GAC) filter prior to discharge to the
atmosphere. Ground water would be pre-filtered and pre-treated to appropriate pH
requirements prior to passage through an air-stripper unit. Air-stripper offgas
would then be directed through a GAC filter prior to discharge to the atmosphere.
Treated ground water would be reinjected into the shallow aquifer, at a location
either west or upgradient of the shallow ground water plume. A total of
approximately six dual-phase extraction wells would be installed within the shallow
ground water plume core and hot spot, the central treatment plant would be located
adjacent to the Holiday Cleaners building, and a total of approximately
10 reinjection wells would be required. Due to the low permeability of the shallow
aquifer, an extended infiltration gallery may be considered in place of reinjection.
2. Operation and Maintenance Components. Ongoing O&M will be required
throughout the active remediation period of 40 years.
3. Monitoring Components. Performance monitoring would be conducted utilizing
existing monitoring wells, and sampled as part of the long-term ground water
sampling program.
16.2.4 Shallow Plume Periphery Alternatives
Alternative 1: No Action
Alternative 2: Monitored Natural Attenuation
Alternative 3: ZVI PRB-Multiple Transects
Alternative 4: ERD (Bio-Barrier)
Alternative 5: Ground Water Extraction and Ex-Situ Treatment
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16.2.4.1 Alternative 1: No Action
Estimated Time for Design/Construction: Not applicable
Estimated Time to Reach Remediation Goals: Not applicable
Estimated Capital Cost: $ 0
Estimated Life Time O&M Costs: $ 0
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 0
Number of Years Cost Is Projected: Not Applicable
The No Action Alternative is included as a baseline for evaluation of the other remedial
alternatives, as required by the NCP. Under Alternative 1, no remedy will be implemented
and source areas will not meet RAOs for the site.
16.2.4.2 Alternative 2: Monitored Natural Attenuation (MNA)
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 269,000
Estimated Life Time O&M Costs: $ 1,632,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 1,901,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. MNA is not an active treatment remedy and there are no
treatment components in this alternative. Under the right conditions, natural
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attenuation processes have the potential to address ground water contamination and
achieve RAOs over a relatively long period of time. Approximately four additional
ground water monitoring wells would be constructed using this alternative.
2. Operation and Maintenance Components. Operation and maintenance
components consist exclusively of routine ground water monitoring over the course
of the treatment period.
3. Monitoring Components. The MNA alternative would primarily utilize the
network of ground water monitoring wells installed during the Preliminary Design
Field Investigation as the means to routinely monitor the nature and extent of
contamination at the GCSP Site and track the progress of the alternative toward
meeting the RAOs at the site. Semi-annual sampling of the 36 wells installed during
the Preliminary Design Field Investigation plus the four new shallow monitoring
wells would occur for 5 years. After 5 years, sampling of all wells would reduce to
an annual basis for 35 additional years (40 total years), concurrent with the sitewide
ground water monitoring program. Sampling may be terminated earlier if RAOs are
met sooner. Sampling of all existing wells is assumed necessary to confirm that the
contaminant plume is stable during application of MNA and for comparisons of
aquifer processes at various depths.
16.2.4.3 Alternative 3: ZVI PRB
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 12,999,000
Estimated Life Time O&M Costs: $ 927,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 13,926,000
Number of Years Cost Is Projected: 40 years
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Ground Water Contamination
1. Treatment Components. A total of approximately 140 MG is estimated to be
impacted with chlorinated solvents contamination. A portion of the impacted
aquifer would be treated with this approach. PRB walls incorporating ZVI provide
passive treatment of contaminants as ground water flows through the wall under
natural ground water flow gradients. A total of approximately 1,700 ft of ZVI-PRB
walls would be installed as multiple transects across the shallow plume and at the
downgradient extent of the shallow plume periphery. Under this scenario, the
ZVI-PRB wall transects would be spaced approximately 200 ft to 400 ft apart along
the length of the shallow plume. The ZVI-PRB walls would be installed using slurry
trenching techniques, where biodegradable slurry is maintained within the trench
during excavation to stabilize the trench. The material excavated during installation
of PRB walls would require offsite disposal.
2. Operation and Maintenance Components. The service life of the PRB wall is
expected to be 20 years. At the end of the 20-year life cycle, a new PRB wall would
be installed to replace the existing wall.
3. Monitoring Components. Performance monitoring would be conducted during the
active treatment period to evaluate the effectiveness of the system.
16.2.4.4 Alternative 4: ERD Bio-Barrier
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 20 years
Estimated Capital Cost: $ 921,000
Estimated Life Time O&M Costs: $2,352,000
Discount Factor: 7%
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Estimated Total Present Worth Cost: $ 3,273,000
Number of Years Cost Is Projected: 20 years
1. Treatment Components. Treatment of the shallow ground water plume periphery
would be performed using ERD in the form of injected carbon source amendment
barriers, called bio-barriers. Bio-barriers are installed as transects across the ground
water plume axis by closely spaced injection of carbon source amendments. Within
these carbon-rich zones, or barriers, biologically mediated reductive dechlorination
of the COCs is enhanced and the process forms a continuous ERD treatment zone to
intercept the plume. Installation of multiple bio-barriers in series achieves RAOs as
ground water passes through each treatment area. Injection points along each
transect will be spaced approximately 25 ft apart with an assumed injection radius of
influence of approximately 15 ft. Permanent injection wells would be installed as
they would be cost effective due to the need for multiple injections of carbon source
amendments over an extended time period to meet RAOs. Each injection well will
be screened from 8 ft bgs to 20 ft bgs for treatment of the shallow ground water
plume periphery. Bio-barriers would be installed as multiple transects across the
shallow ground water plume periphery, with an assumed total bio-barrier length of
approximately 2,400 ft. Under this scenario, the bio-barriers would be spaced
approximately 200 ft apart along the length of the shallow plume periphery.
4. Operation and Maintenance Components. A total of sixteen ERD applications
would occur once every 15 months to treat the COCs.
5. Monitoring Components. Performance monitoring would be conducted by
installing and sampling up to 30 ground water monitoring wells on either side of
various bio-barriers to determine the effectiveness of the treatment technology, and
to track overall progress during the active treatment period. Semi-annual sampling
will be conducted during the course of active treatment.
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16.2.4.5 Alternative 5: Ground Water Extraction and Ex-Situ Treatment
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 3,539,000
Estimated Life Time O&M Costs: $ 9,970,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 13,509,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. Under this alternative, a network of extraction wells
would be located within the shallow plume periphery. Due to the shallow depths
targeted for treatment, dual-phase extraction is anticipated. Dual-phase extraction
involves the installation of extraction wells screened both below and slightly above
the ground water table and application of vacuum to the wells to extract both soil
vapor and ground water. With dual-phase extraction, relatively high extraction rates
are used to actively dewater the upper portions of the shallow aquifer. This
dewatering provides for rapid removal of highly contaminated ground water and
exposes additional vadose zone for SVE.
Extracted soil vapor and ground water would be conveyed to a central treatment
plant where ex-situ treatment would include two treatment trains, one for extracted
soil vapor and one for extracted ground water. Soil vapor would be directed
through a GAC filter prior to discharge to the atmosphere. Ground water would be
pre-filtered and pre-treated to appropriate pH requirements prior to passage
through an air-stripper unit. Air-stripper offgas would then be directed through a
GAC filter prior to discharge to the atmosphere. Treated ground water would be
reinjected into the shallow aquifer, at a location either west or upgradient of the
shallow ground water plume. A total of approximately eight dual-phase extraction
wells would be installed within the shallow ground water plume periphery, the
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central treatment plant would be located adjacent to the Holiday Cleaners building,
and a total of approximately 15 reinjection wells would be required. Due to the low
permeability of the shallow aquifer, an extended infiltration gallery may be
considered in place of reinjection.
2. Operation and Maintenance Components. Ongoing O&M will be required
throughout the active remediation period of 40 years.
3. Monitoring Components. Performance monitoring would be conducted utilizing
existing monitoring wells, sampled as part of the long-term ground water sampling
program.
16.2.5 Deeper Ground Water Alternatives
Alternative 1: No Action
Alternative 2: Monitored Natural Attenuation
Alternative 3: ZVI PRB-with Deep ERD
Alternative 4: ERD (Bio-Barrier)
Alternative 5: Ground Water Extraction and Ex-Situ
16.2.5.1 Alternative 1: No Action
Estimated Time for Design/Construction: Not applicable
Estimated Time to Reach Remediation Goals: Not applicable
Estimated Capital Cost: $ 0
Estimated Life Time O&M Costs: $ 0
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 0
Number of Years Cost Is Projected: Not Applicable
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The No Action Alternative is included as a baseline for evaluation of the other remedial
alternatives, as required by the NCP. Under Alternative 1, no remedy will be implemented
and source areas will not meet RAOs for the site.
16.2.5.2 Alternative 2: Monitored Natural Attenuation
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 344,000
Estimated Life Time O&M Costs: $ 1,693,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 2,037,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. MNA is not an active treatment remedy and there are no
treatment components in this alternative. Under the right conditions, natural
attenuation processes have the potential to address ground water contamination and
achieve RAOs over a relatively long period of time. Approximately six additional
ground water monitoring wells would be constructed using this alternative.
2. Operation and Maintenance Components. Operation and maintenance
components consist exclusively of routine ground water monitoring over the course
of the treatment period.
3. Monitoring Components. The MNA alternative would primarily utilize the
network of ground water monitoring wells installed during the Preliminary Design
Field Investigation as the means to routinely monitor the nature and extent of
contamination at the GCSP Site and track the progress of the alternative toward
meeting the RAOs at the site. Semi-annual sampling of the 36 wells installed during
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the Preliminary Design Field Investigation plus the six new shallow monitoring
wells would occur for 5 years. After 5 years, sampling of all wells would reduce to
an annual basis for 35 additional years (40 total years), concurrent with the sitewide
ground water monitoring program. Sampling may be terminated earlier if RAOs are
met sooner. Sampling of all existing wells is assumed necessary to confirm that the
contaminant plume is stable during application of MNA and for comparisons of
aquifer processes at various depths.
16.2.5.3 Alternative 3: ZVI PRB with Deep ERD Bio-Barrier
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $24,640,000
Estimated Life Time O&M Costs: $3,093,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 27,733,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. A total of approximately 140 MG is estimated to be
impacted with chlorinated solvents contamination. A portion of the impacted
aquifer would be treated with this approach. PRB walls incorporating ZVI provide
passive treatment of contaminants as ground water flows through the wall under
natural ground water flow gradients. A total of approximately 1,000 ft of ZVI-PRB
walls up to 60 ft deep would be installed as multiple transects across the deeper
ground water plume. The ZVI-PRB walls would be installed using slurry trenching
techniques, where biodegradable slurry is maintained within the trench during
excavation to stabilize the trench. The material excavated during installation of PRB
walls would require offsite disposal. Treatment below 60-ft depth would be
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accomplished by ERD bio-barriers since the installation of sufficiently-thick ZVI-PRB
walls at depths greater than 60 ft bgs is not considered practical.
2. Operation and Maintenance Components. The service life of the PRB wall is
expected to be 20 years. At the end of the 20-year life cycle, a new PRB wall would
be installed to replace the existing wall. For the deep ERD application, a total of
16 carbon source amendment injections are assumed over a 20-year period (one
injection every 15 months) to meet the RAOs for ground water at this depth.
3. Monitoring Components. Performance monitoring would be conducted during the
active treatment period to evaluate the effectiveness of the system.
16.2.5.4 Alternative 4: ERD Bio-Barrier
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 20 years
Estimated Capital Cost: $ 1,630,000
Estimated Life Time O&M Costs: $5,592,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 7,222,000
Number of Years Cost Is Projected: 20 years
1. Treatment Components. Treatment of the deeper ground water would be
performed using ERD in the form of injected carbon source amendment barriers,
called bio-barriers. Bio-barriers are installed as transects across the ground water
plume axis by closely spaced injection of carbon source amendments. Within these
carbon-rich zones, or barriers, biologically mediated reductive dechlorination of the
COCs is enhanced and the process forms a continuous ERD treatment zone to
intercept the plume. Installation of multiple bio-barriers in series achieves RAOs as
ground water passes through each treatment area. Injection points along each
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transect will be spaced approximately 25 ft apart with an assumed injection ROI of
approximately 15 ft. Permanent injection wells would be installed as they would be
cost effective due to the need for multiple injections of carbon source amendments
over an extended time period to meet RAOs. Each injection well will be screened
from 60 ft bgs to at least 80 ft bgs. Bio-barriers would be installed as multiple
transects across the deeper ground water plume, with an assumed total bio-barrier
length of approximately 1,250 ft.
2. Operation and Maintenance Components. A total of 16 ERD applications would
occur once every 15 months to treat the COCs.
3. Monitoring Components. Performance monitoring would be conducted by
installing and sampling up to 10 ground water monitoring wells on either side of
various bio-barriers to determine the effectiveness of the treatment technology, and
to track overall progress during the active treatment period. Semi-annual sampling
will be conducted during the course of active treatment.
16.2.5.5 Alternative 5: Ground Water Extraction and Ex-Situ Treatment
Estimated Time for Design/Construction: 1 year
Estimated Time to Reach Remediation Goals: 40 years
Estimated Capital Cost: $ 3,829,000
Estimated Life Time O&M Costs: $ 9,970,000
Discount Factor: 7%
Estimated Total Present Worth Cost: $ 13,799,000
Number of Years Cost Is Projected: 40 years
1. Treatment Components. Under this alternative, a network of extraction wells
would be located within the deeper ground water plume. Extracted ground water
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would be conveyed to a central treatment plant where ex-situ treatment would
include air-stripping and offgas control. Ground water would be pre-filtered and
pre-treated to appropriate pH requirements prior to passage through an air-stripper
unit. Air-stripper offgas would then be directed through a GAC filter prior to
discharge to the atmosphere. Treated ground water would be reinjected into the
deeper aquifer, at a location either west or upgradient of the shallow ground water
plume. A total of approximately six extraction wells would be installed within the
deeper ground water, the central treatment plant would be located adjacent to the
Holiday Cleaners building, and a total of approximately 10 reinjection wells would
be required.
2. Operation and Maintenance Components. Ongoing O&M will be required
throughout the active remediation period of 40 years.
3. Monitoring Components. Performance monitoring would be conducted utilizing
existing monitoring wells, sampled as part of the long-term ground water sampling
program.
16.3 Other Common Elements and Distinguishing Features
of Each Alternative
Common elements and distinguishing features unique to each alternative include key
ARARs, long-term reliability of the remedy, quantities of untreated wastes, and uses of
presumptive remedies. Table 11 (Summary ARARs) and Table 12 (Description of ARARs
for Selected Remedy) summarize the ARARs pertaining to the main elements of each of the
remedial alternatives and the Selected Remedy. Several of the remedial alternatives have
elements in common, including excavation and waste disposal requirements.
16.3.1 Key Applicable or Relevant and Appropriate Requirements
With the exception of the No Action Alternative, it is assumed that an appropriate design
for all retained technologies, or technology combinations, can be developed for each media
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of concern to meet applicable ARARs. The primary difference in technology combinations
for the different contaminated media with regard to complying with ARARs is the length of
time required before ARARs would be achieved. Table 11 (Summary of ARARs)
summarizes the ARARs for alternatives and shows how they will be complied with.
16.3.2 Long-Term Reliability of the Remedy
The magnitude of risk will remain indefinitely if no action is taken at the site. All of the
alternative technologies considered for remedial action will provide long-term reliability
once all DNAPL is removed, provided that ICs remain effective until that time. However if
residual DNAPL cannot be completely removed from the ground water at the site, the
remedy may no longer provide long-term reliability. If the remedy cannot be implemented
as planned then EPA will develop an alternate plan. At this time the EPA cannot determine
the cost for replacement of the remedy, as there is insufficient data for analysis of such site
circumstances.
16.3.3 Quantities of Untreated Wastes
16.3.1.1 Indoor Air (Vapor Intrusion Mitigation)
The No Action Alternative does not provide treatment. The vapor mitigation systems do
not provide active treatment, but physically block contaminants from entering a structure.
16.3.1.2 Source Area, Shallow Plume Core and Hot Spot, Shallow Plume Periphery,
and Deeper Ground Water Treatment
Approximately 44.5 MG of ground water and 6,500 yd3 of soil will be treated at the site.
Pilot-scale and bench-scale testing is required to determine the exact quantity of COCs,
which will be treated by the various technologies, including thermal treatment, ISCO, ERD,
ZVI PRBs, MNA, and pump and treat. It is anticipated that each of the proposed
technologies can remove sufficient COCs to meet the site RAOs.
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16.3.4 Uses of Presumptive Remedies
The following presumptive remedies prescribed by EPA guidance (EPA, 1993) were
evaluated in the FS.
16.3.4.1 VOCs in Soil
• Soil Vapor Extraction (SVE)
• Ex-Situ Thermal Desorption
• Ex-Situ Thermal Incineration
The only presumptive technology provided in current EPA guidance for VOCs in soils that
was retained is soil vapor extraction, with enhancements such as pneumatic fracturing,
sealing the ground surface, and the use of horizontal vapor wells. The other presumptive
technologies were each rejected based on site-specific conditions, which severely limit the
effectiveness of the technologies at the GCSP Site. A dual-phase SVE technology was
selected as part of the thermal treatment system for the Source Areas.
16.3.4.2 VOCs in Ground Water
• Ground Water Extraction and Ex-Situ Treatment
Current EPA guidance for treatment of VOCs dissolved in ground water includes only
ground water extraction and ex-situ treatment. Ground water extraction and ex-situ
treatment is a proven technology for treatment of VOCs in ground water, and can be
implemented at the GCSP Site. Ground water extraction and ex-situ treatment was not
selected for the site based on current site conditions.
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16.4 Expected Outcomes of Each Alternative
Implementation of any of the alternatives considered for this site, other than the No Action
Alternative, is expected to reduce the human health risk over time at the GCSP Site.
However, the time required to achieve the RAOs for each site-impacted media varies
anywhere from 1 years for to 40 years depending on the alternative used. The vapor
mitigation systems will be able to achieve RAOs for indoor air as soon as installation is
complete. In the Source Areas implementation of the thermal treatment is expected to be
achieve RAOs relatively sooner than ISCO and ERD. In the shallow ground water and hot
spot area, implementation of the ISCO with follow-on ERD is expected to achieve the RAOs
sooner than with ZVI-PRB, ERD and pump and treat. In the shallow ground water plume
periphery, implementation of the ERD bio-barrier is expected to achieve the RAOs sooner
than with MNA, ZVI and pump and treat. For deeper ground water implementation of the
ERD bio-barrier is expected to achieve the RAOs sooner than with the MNA, ZVI-PRB
followed with ERD, pump and treat.
The outcome of the remedy is not expected to change the land and ground water use at the
site as it will likely continue to be residential and light commercial. Implementation of the
Selected Remedy will reduce risk to human health and restore the ground water to
beneficial use.
17.0 Comparative Analysis of Alternatives
The EPA uses nine NCP criteria to evaluate remedial alternatives for the cleanup of a
release. These nine criteria are categorized into three groups: threshold, balancing, and
modifying. The threshold criteria must be met for an alternative to be eligible for selection.
The threshold criteria are overall protection of human health and the environment and
compliance with ARARs. The balancing criteria are used to weigh major tradeoffs among
alternatives. The five balancing criteria are long-term effectiveness and permanence;
reduction of toxicity, mobility or volume through treatment; short-term effectiveness;
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implementability; and cost. The modifying criteria are State acceptance and community
acceptance. Table 13 (Evaluation Criteria for Superfund Remedial Alternatives) briefly
describes the evaluation criteria.
Based on the initial screening of technologies and evaluation of alternatives, a number of
remedial alternatives were evaluated for each site-impacted area. Tables 14 through 18
(Comparison of Remedial Alternatives) summarize how these alternatives comply with the
nine evaluation criteria specified in the NCP §300.430(f)(5)(i). The No Action Alternative for
each media is not considered further in the comparative analysis of alternatives as it cannot
meet the threshold criteria or address risks at the site. Following is a comparative analysis
of the remedial alternatives other than the No Action Alternative.
17.1 Overall Protection of Human Health and the Environment
Overall protection of human health and the environment addresses whether each
alternative provides adequate protection of human health and the environment and
describes how risks posed through each exposure pathway are eliminated, reduced, or
controlled through treatment, engineering controls, and/or institutional controls.
All of the alternatives, except the No Action Alternative, are protective of human health and
the environment by eliminating, reducing, or controlling risks posed by the site through
treatment of soil and ground water contaminants, engineering controls, and/or institutional
controls. Basic comparative analyses for the technologies, or technology combinations, for
the different media of concern are presented below.
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17.1.1 Indoor Air (Vapor Intrusion Mitigation)
Only two technical approaches were identified pertaining to indoor air. These technical
approaches included either No Action or Installation of Radon-Type Vapor Mitigation
Systems.
Under the Installation of Radon-Type Vapor Mitigation Systems, the contaminated vapors
are physically isolated from the overlying structure by installing an impermeable vapor
barrier and a ventilation system to remove the vapors from beneath the barrier. Human
health and the environment are protected since the vapor barrier and venting system
remove the pathway for volatile organics present in the subsurface to enter the structure.
17.1.2 Source Area Treatment
Four approaches including the No Action Alternative were identified for source area
treatment at the GCSP Site. The three technical approaches to remediating the source area
(thermal treatment, ISCO with Follow-on ERD, and ERD Applied in a Grid) would be
expected to remove COCs from the source area under the implementation of an
appropriately designed program. If residual DNAPL or sorbed soil source material remains
after the active treatment periods, these approaches may not achieve RAOs.
Thermal treatment may be less subject to non-uniform treatment distribution in the source
area as it is less sensitive to fine-grained or heterogeneous subsurface conditions and would
be accomplished in a single treatment event. However, as a one-time event, thermal
treatment would need to achieve very high removal efficiency (99.9 percent or more) in that
single event to approach RAOs. Since 99.9 percent or more reduction in contaminant
volume would constitute very high removal efficiency for any type of remedial technology,
it is possible that additional final polishing by another remedial technology may need to be
instituted to achieve RAOs.
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Since both ISCO and ERD rely on amendments being able to come in contact with COCs in
the subsurface, the fine-grained heterogeneous soils in the treatment area may impact the
effectiveness and implementability of these technologies. Multiple injection events for both
ISCO and ERD carbon-source amendments would be required for these technologies. With
regard to ERD or bio-barriers, if reductive dechlorination of the COCs is retarded by site-
specific conditions then equally, or more toxic, intermediary by-products of biodegradation
may persist.
While the thermal treatment and ISCO option technologies do have the capability of directly
treating residual DNAPL to some degree, the effectiveness of all technology options in
meeting or approaching RAOs will be limited if residual DNAPL or sorbed soil
contamination persists after active remediation.
All of the three technical approaches considered are protective of human health and the
environment. The length of time required to achieve protectiveness varies for each
approach with thermal treatment being the quickest compared to ISCO and ERD. Thermal
treatment also is cost-competitive and will have the least impact on the community.
17.1.3 Shallow Ground Water Plume Core and Hot Spot Treatment
Five approaches including the No Action Alternative were identified for treatment of the
shallow ground water plume core and hot spot at the GCSP Site to depths of 20 ft bgs. The
four technical approaches to remediating the shallow ground water plume core and hot spot
(ZVI-PRB, ISCO with Follow-on ERD, ERD Bio-barriers, and Pump and Treat) would be
expected to remediate COCs within the shallow plume core under the implementation of an
appropriately designed program. If any residual DNAPL or sorbed soil source material
remains after the active treatment periods, these approaches may not achieve RAOs. ISCO
is the only identified technology that would have the capability of directly treating residual
DNAPL.
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Since both ISCO and ERD rely on amendments being able to come in contact with COCs, the
fine-grained heterogeneous soils in the treatment area may impact the effectiveness and
implementability of these technologies. The low permeability soils at the GCSP Site also
may pose difficulties in achieving full ground water capture under the Pump and Treat
option. Also, multiple injection events for both ISCO and ERD carbon-source amendments
would be specified for these technologies. And with regard to ERD or bio-barriers, if
reductive dechlorination of the COCs is retarded by site-specific conditions then equally, or
more toxic, intermediary by-products of biodegradation may persist.
PRB application would have the most substantial short-term installation impacts and would
require replacement once every 20 years. The natural ground water velocity would limit the
treatment time for the shallow ground water plume core and hot spot by PRBs.
The Pump and Treat option is expected to take the longest time period and would require
ongoing O&M throughout that period.
Among the four technical approaches considered for the Shallow Plume Core and Hot Spot,
ISCO with follow-on ERD would achieve protection of human health and environment
relatively quicker than ERD and PRB. ISCO with follow-on ERD is the only technology that
can reliably treat any principal threat waste if found in the Shallow Plume Core and Hot
Spot.
17.1.4 Shallow Ground Water Periphery
Five approaches including the No Action Alternative were identified for treatment of the
shallow ground water periphery at the GPSC Site to depths of 20 ft bgs.
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The four technical approaches to remediating the shallow ground water periphery (MNA,
ZVI-PRB, ERD Bio-barriers, and Pump and Treat) would be expected to remediate COCs
within the shallow plume periphery under the implementation of an appropriately
designed program. If any residual DNAPL or sorbed soil source material remains after the
active treatment periods, these approaches may not achieve RAOs. None of the identified
technologies have the capability of directly treating residual DNAPL during
implementation of the Remedial Action.
Since ERD relies on amendments being able to come in contact with COCs, the fine-grained
heterogeneous soils in the treatment area may impact the effectiveness and
implementability of this technology. The low permeability site soils also may pose
difficulties in achieving full ground water capture under the Pump and Treat option.
Multiple injection events of ERD carbon-source amendments would be specified for this
technology and if reductive dechlorination of the COCs by the bio-barriers is limited by site-
specific conditions then equally, or more toxic, intermediary by-products of biodegradation
may persist.
PRB application would have the most substantial short-term installation impacts. The
natural ground water velocity would limit the treatment time for the shallow ground water
periphery by PRBs. The Pump and Treat option and MNA are expected to take the longest
time periods to achieve RAOs. While the Pump and Treat option would require ongoing
O&M throughout that period, actions to support MNA would be limited to ongoing ground
water monitoring.
Among the four technical approaches considered for the Shallow Plume Periphery, ERD
Bio-barriers is the least expensive and would achieve protection of human health and
environment relatively quicker than MNA, ZVI-PRB and Pump and Treat.
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17.1.5 Deeper Ground Water
Five approaches including the No Action Alternative were identified for treatment of the
deeper ground water at the GCSP Site below 20 ft bgs. The ground water would remain a
continuing source to the downgradient plume and could potentially migrate even deeper in
the aquifer, potentially impacting the drinking water aquifer.
The four technical approaches to remediating the deeper ground water (MNA, Bio-barriers,
ZVI-PRB in Conjunction with ERD Bio-barriers, and Pump and Treat) would be expected to
remediate COCs within the deeper plume under the implementation of an appropriately
designed program. If any residual DNAPL or sorbed soil source material remains after the
active treatment periods, these approaches may not achieve RAOs. None of the identified
technologies have the capability of directly treating residual DNAPL during
implementation of the Remedial Action.
Since ERD relies on amendments being able to come in contact with COCs, the fine-grained
heterogeneous soils in the treatment area may impact the effectiveness and
implementability of this technology. The low permeability site soils also may pose
difficulties in achieving full ground water capture under the Pump and Treat option.
Multiple injection events of ERD carbon-source amendments would be specified for this
technology and if reductive dechlorination of the COCs by the bio-barriers is limited by site-
specific conditions then equally, or more toxic, intermediary by-products of biodegradation
may persist.
PRB application would have the most substantial short-term installation impacts. The
natural ground water velocity would limit the treatment time for the deeper ground water
periphery by PRBs. The Pump and Treat option and MNA are expected to take the longest
time periods to achieve RAOs. While the Pump and Treat option would require ongoing
O&M throughout that period, actions to support MNA would be limited to ongoing ground
water monitoring.
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Among the four technical approaches considered for the Deeper Ground Water, ERD
Bio-barriers is the least expensive and would achieve protection of human health and
environment relatively quicker than MNA, ZVI-PRB in conjunction with ERD and Pump
and Treat.
17.2 Compliance with ARARs
Section 121(d) of CERCLA and NCP §300.430(f)(1)(ii)(B) require that remedial actions at
CERCLA sites at least attain legally applicable or relevant and appropriate Federal and State
requirements, standards, criteria, and limitations, which are collectively referred to as
“ARARs,” unless such ARARs are waived under CERCLA §121(d)(4). Compliance with
ARARs addresses whether a remedy will meet all of the ARARs or provides a basis for
invoking a waiver.
With the exception of the No Action Alternative, an appropriate design for all retained
technologies, or technology combinations, can be developed for each media of concern to
meet applicable RAOs. The primary difference in technology combinations for the different
contaminated media with regard to complying with ARARs is the length of time required
before RAOs would be achieved.
A key assumption in evaluating technology combinations’ ability to comply with ARARs is
that an appropriately designed program can be developed to meet ARARs with each
technology type. This assumption is based solely on the existing site data.
17.3 Long-Term Effectiveness and Permanence
Long-term effectiveness and permanence refers to expected residual risk and the ability of a
remedy to maintain reliable protection of human health and the environment over time,
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once cleanup levels have been met. This criterion includes the consideration of residual risk
that will remain onsite following remediation and the adequacy and reliability of controls.
17.3.1 Magnitude of Residual Risk
With the exception of the No Action Alternative, all of the alternatives are expected to meet
RAOs given an appropriate design. This assumption is based on only evaluation of the
technologies relative to available site data. Achieving RAOs would provide a substantial
reduction in long-term residual risk for all impacted media using any of the technology
approaches and will be protective of human health in the long-term.
17.3.1.1 Indoor Air (Vapor Intrusion Mitigation)
Installation of radon-type vapor mitigation systems will prevent vapor intrusion of COCs
above acceptable risk levels, as long as the barrier and ventilation system are kept in good
working order. Human health and the environment are protected since the vapor barrier
and venting system remove the pathway for volatile organics present in the subsurface to
enter the structure.
17.3.1.2 Source Area Treatment
Each of the active treatment alternatives is anticipated to ultimately lower the risk from
vapor intrusion and ground water exposure. An appropriately designed, thermal source-
area treatment is expected to approach RGs and RAOs and reduce residual risk in the
source areas. Final polishing following thermal treatment may be necessary to meet RGs
and RAOs, and may include targeted ERD or ISCO treatments.
ISCO with follow-on ERD treatment can be appropriately designed to meet long-term RGs
and RAOs and will reduce residual risk. If DNAPL or sorbed-soil contamination persists
following completion of ISCO and ERD treatments, a dissolved-phase plume is likely to
persist or rebound within the aquifer and the treatment will no longer limit residual risk.
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ERD treatment can be appropriately designed to meet long-term RGs and RAOs and will
reduce residual risk. As with ISCO, if DNAPL or sorbed-soil contamination persists
following completion of ISCO and ERD treatments, a dissolved-phase plume is likely to
persist or rebound within the aquifer and the treatment will no longer limit residual risk.
Among the alternatives considered for the Source Area, thermal treatment is relatively
better in not leaving any residual risk in the long-term and be protective of human health
and the environment.
17.3.1.3 Shallow Ground Water Plume Core and Hot Spot Treatment
PRBs designed for the site-specific dissolved-phase ground water plume will achieve long-
term RGs and RAOs. If DNAPL or sorbed soil contamination persists in the areas between
the PRBs and continues to propagate a dissolved-phase plume beyond the designed service
life of the PRBs, then this technology will no longer achieve RAOs or limit residual risk.
Given the passive nature of this technology, high concentrations of COCs will persist in
shallow ground water and continue to support a vapor intrusion risk for many years.
ISCO with follow-on ERD treatment can be appropriately designed to meet long-term RGs
and RAOs and will reduce residual risk. If DNAPL or sorbed-soil contamination persists
following completion of ISCO and ERD treatments, a dissolved-phase plume is likely to
persist or rebound within the aquifer and the treatment will no longer limit residual risk.
Until shallow ground water COC concentrations meet RGs, they may continue to support a
significant vapor intrusion risk.
ERD treatment can be appropriately designed to meet long-term RGs and RAOs and will
reduce residual risk. Once the cleanup goals are achieved this alternative will be protective
in the long-term. As with ISCO, if DNAPL or sorbed soil contamination persists following
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completion of ERD treatments, a dissolved-phase plume is likely to persist or rebound
within the aquifer and the treatment will no longer limit residual risk. Until shallow ground
water COC concentrations meet RGs, they may continue to support a significant vapor
intrusion risk.
Pump and treat methods can be designed to treat the shallow ground water plume and hot
spot and meet long-term RGs and RAOs, and eventually limit residual risk. If DNAPL or
sorbed soil contamination is present, pump and treat technology in low permeability
sediments typical of the GCSP Site may take longer than 40 years to achieve RAOs.
Additionally, portions of the aquifer that have been partially remediated may be subject to
recontamination or rebound from remaining sorbed or DNAPL contaminant sources. Until
shallow ground water COC concentrations meet RGs, they may continue to support a
significant vapor intrusion risk.
All of the technologies considered for the Shallow Plume Core and Hot Spot would
probably be effective in the long-term and leave no residual risk at the site. However, if
principal threat waste is encountered in the Shallow Plume Core and Hot Spot Area, using
ISCO with follow-on ERD has the best chance of ensuring long-term effectiveness and
permanence.
17.3.1.4 Shallow Ground Water Periphery
MNA of the shallow ground water periphery may achieve long-term RGs and RAOs and
eventually limit residual risk. However, given the passive nature of the alternative, high
concentrations of COCs will persist in the shallow ground water periphery for an extended
period of time, presenting continuing residual risk. If DNAPL or sorbed soil contamination
persists in the area, a dissolved-phase plume will persist in the aquifer and MNA may not
achieve RAOs or limit residual risk. The ongoing monitoring of the remedial alternative
will limit some residual risk by allowing regular evaluation of the effectiveness of the
alternative.
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PRBs designed for the site-specific, dissolved-phase ground water plume will achieve long-
term RGs and RAOs. If DNAPL or sorbed-soil contamination persists in the areas between
the PRBs and continues to propagate a dissolved-phase plume beyond the designed service
life of the PRBs, then this technology will no longer achieve RAOs or limit residual risk.
ERD treatment can be appropriately designed to meet long-term RGs and RAOs and will
reduce residual risk. If DNAPL or sorbed-soil contamination persists following completion
of ERD treatments, a dissolved-phase plume is likely to persist or rebound within the
aquifer and the treatment will no longer limit residual risk.
Pump and treat methods can be designed to treat the shallow ground water plume
periphery and meet long-term RGs and RAOs, and eventually limit residual risk. If DNAPL
or sorbed soil contamination is present, pump and treat technology in low permeability
sediments typical of the GCSP Site may take longer than 40 years to achieve RAOs.
Additionally, portions of the aquifer that have been partially remediated may be subject to
recontamination or rebound from remaining sorbed-soil or DNAPL contaminant sources.
All of the technologies considered for the Shallow Plume Periphery would probably be
effective in the long-term and leave no residual risk at the site. PRB and Pump and Treat are
more expensive and will relatively take longer to achieve cleanup goals compared to ERD.
MNA is not proven at the site and may take a long time to achieve cleanup goals.
17.3.1.5 Deeper Ground Water
MNA of the deeper ground water below 20 ft bgs may achieve long-term RGs and RAOs
and eventually limit residual risk. However, given the passive nature of the alternative,
high concentrations of COCs will persist in the deeper ground water periphery for an
extended period of time, presenting continuing residual risk. If DNAPL or sorbed soil
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contamination persists in the area, a dissolved-phase plume will persist in the aquifer and
MNA may not achieve RAOs or limit residual risk. The ongoing monitoring of the remedial
alternative will limit some residual risk by allowing regular evaluation of the effectiveness
of the alternative.
PRBs, along with supplemental bio-barriers, designed for the site-specific dissolved-phase
ground water plume will achieve long-term RGs and RAOs. If DNAPL or sorbed soil
contamination persists in the areas between the PRBs and continues to propagate a
dissolved-phase plume beyond the designed service life of the PRBs, then this technology
will no longer achieve RAOs or limit residual risk.
ERD treatment can be appropriately designed to meet long-term RGs and RAOs and will
reduce residual risk. If DNAPL or sorbed soil contamination persists following completion
of ERD treatments, a dissolved-phase plume is likely to persist or rebound within the
aquifer and will no longer limit residual risk.
Pump and treat methods can be designed to treat the deeper ground water plume and meet
long-term RGs and RAOs, and eventually limit residual risk. If DNAPL or sorbed soil
contamination is present, pump and treat technology in low permeability sediments typical
of the GCSP Site may take longer than 40 years to achieve RAOs. Additionally, portions of
the aquifer that have been partially remediated may be subject to recontamination or
rebound from remaining sorbed or DNAPL contaminant sources.
All of the technologies considered for the Deeper Ground Water would probably be
effective in the long-term and leave no residual risk at the site. PRB and Pump and Treat are
more expensive remedies and will relatively take longer to achieve cleanup goals compared
to ERD. MNA is not proven at the site and may take a long time to achieve cleanup goals.
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17.3.2 Adequacy and Reliability of Controls
With the exception of the No Action alternatives, each of the proposed remedial
technologies can provide adequate and reliable treatment of COCs. Long-term adequacy
and reliability of any controls for the downgradient portions of the site also will ultimately
depend on the corresponding remediation of the source area media.
17.3.2.1 Indoor Air (Vapor Intrusion Mitigation)
For the indoor air media, the Radon-type Vapor Mitigation System is expected to provide
more adequate and reliable controls in meeting RAOs than the No Action Alternative.
However, long-term adequacy and reliability of this control will ultimately depend on
elimination of the vapor intrusion pathway by remediation of the shallow ground water
sources.
17.3.2.2 Source Area Treatment
Thermal treatment involves volatilization of COCs from the subsurface and collection of
vapors using soil vapor extraction. Thermal heating is a highly reliable method of causing
volatilization and soil vapor extraction is a reliable method of vapor collection when
appropriately designed and implemented. Thermal resistive treatment of the source area
would be accomplished in a single application event at the site and would not require
repeat treatments. However, meeting RAOs at the source area with a single application will
require an extremely high removal efficiency and thermal treatment alone may not fully
meet RAOs following the single application. Additional polishing treatment may be
required and can include natural active biological treatment during the cool-down period,
or active application of ISCO or ERD. A loss of process control (incomplete vapor recovery
using SVE) could lead to escape of COC vapors to the atmosphere or into structures
overlying the treatment zone or the recondensing of COC vapors outside the treatment area.
Both ISCO and ERD would, by design, require multiple treatments over an extended time
period to meet RAOs due to the limited residence times of the injected materials in the
aquifer (although ERD amendments far outlast oxidant amendments). Individual treatment
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events over time would be discrete efforts and substantial O&M of these technologies would
not be required between events. Both ISCO and ERD have been proven reliable methods of
treating the COCs, but both require injection of amendments into the subsurface that can be
difficult to control. ISCO is more sensitive to injection uniformity and initial contact with
contaminants than is ERD since ERD amendments have a much longer residence time and
can migrate with ground water to interact with contaminants. Ineffective distribution of
ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase
contaminants.
17.3.2.3 Shallow Ground Water Plume Core and Hot Spot Treatment
For the shallow ground water plume core and hot spot media, appropriately designed and
implemented measures should adequately and reliably meet RAOs. If sorbed-phase
contaminants remain following any of treatments, it would substantially impact the
adequacy of the control. The ZVI-PRBs have been designed for a service life of 20 years, and
will require replacement at this time since RAOs are not expected to be met for 40 years.
Once installed, the ZVI-PRB walls would not require subsequent O&M other than the single
replacement of the wall at 20 years.
The adequacy and effectiveness of PRBs will decrease over time as the reactive material in
the PRBs degrades, but they have been designed to provide effective treatment through
20 years. The effectiveness of the ZVI-PRB walls also is dependent upon a thorough
understanding of the hydraulic flow conditions within the aquifer and, if not properly
designed or installed, bypass of ground water around, below, or above the barrier can
occur.
Both ISCO and ERD would, by design, require multiple treatments over an extended time
period to meet RAOs due to the limited residence times of the injected materials in the
aquifer. Individual treatment events over time would be discrete efforts and substantial
O&M of these technologies would not be required between events. Both ISCO and ERD
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have been proven reliable methods of treating the COCs, but both require injection of
amendments into the subsurface, which can be difficult to control. ISCO is more sensitive to
injection uniformity and initial contact with contaminants than is ERD since ERD
amendment have a much longer residence time and can migrate with ground water to
interact with contaminants. Ineffective distribution of ISCO or ERD amendments can lead
to untreated residual sorbed-phase contaminants.
The infrastructure associated with the pump and treat option for the shallow ground water
core and hot spot would be subject to regular O&M needs and components may exceed
their service life and require replacement over the course of the extended implementation of
this technology. Damage, fouling, or loss of specific capacity of the pump and treat system
extraction and/or injection wells may require replacement of these components as well.
Significant failures of equipment during treatment may require the cessation of treatment
while repairs are conducted.
Although all technologies considered are reliable and adequate, the ISCO with follow-on
ERD and ERD Bio-barriers remedy are less expensive; reliable and adequate; and would
take the shortest time to achieve cleanup goals compared to PRB, and Pump and Treat.
17.3.2.4 Shallow Ground Water Periphery and Deeper Ground Water
Long-term adequacy and reliability of any controls for the either the shallow or deep
ground water periphery will ultimately be dependent on corresponding remediation of
upgradient or overlying contamination in the source area, the shallow ground water plume
core and hot spot, or the shallow ground water periphery. With MNA, no specific controls
or infrastructure are installed. Given appropriate site conditions, MNA can be a reliable
method (reductive dechlorinated of site COCs) of reaching RAOs over long time periods.
The ZVI-PRBs have been designed for a service life of 20 years, and will require replacement
at this time since RAOs are not expected to be met for 40 years. Once installed, the ZVI-PRB
walls would not require subsequent O&M other than the single replacement of the wall at
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20 years. The adequacy and effectiveness of PRBs will decrease over time as the reactive
material in the PRBs degrades, but they have been designed to provide effective treatment
through 20 years. The effectiveness of the ZVI-PRB walls also is dependent upon a
thorough understanding of the hydraulic flow conditions within the aquifer and, if not
properly designed or installed, bypass of ground water around, below, or above the barrier
can occur.
ERD would, by design, require multiple treatments over an extended time period to meet
RAOs due to the limited residence times of the injected materials in the aquifer. Individual
treatment events over time would be discrete efforts and substantial O&M of these
technologies would not be required between events. ERD has been proven to be a reliable
method of treating the COCs, but requires injection of amendments into the subsurface,
which can be difficult to control. Ineffective distribution of ERD amendments can lead to
untreated residual sorbed-phase contaminants.
The infrastructure associated with the pump and treat option for the shallow ground water
core and hot spot would be subject to regular O&M needs and components may exceed
their service life and require replacement over the course of the extended implementation of
this technology. Damage, fouling, or loss of specific capacity of the pump and treat system
extraction and/or injection wells may require replacement of these components as well.
Significant failures of equipment during treatment may require the cessation of treatment
while repairs are conducted.
Although all technologies considered are reliable and adequate, the ERD Bio-barrier remedy
is the least expensive technology; reliable and adequate; and would take the shortest time to
achieve cleanup goals compared to MNA, PRB and Pump and Treat.
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17.4 Reduction of Toxicity, Mobility, and Volume
Reduction of toxicity, mobility, or volume through treatment refers to the anticipated
performance of the treatment technologies that may be included as part of a remedy.
With the exception of the No Action Alternative, it is assumed that an appropriate design
for all retained technologies, or technology combinations, would be able to be developed to
permanently reduce toxicity, mobility, and volume of COCs. One exception is in the case of
the Vapor Mitigation option for the indoor air media. In that case, COCs are simply blocked
from entering structures to eliminate a completed exposure pathway and the toxicity,
mobility, and volume (TMV) of COCs is not affected. Therefore, this technology relies on
other methods of treatment within source areas and the shallow ground water plume core
to reduce COCs in the subsurface to concentrations that no longer support vapor intrusion
above human health risk-based action levels.
17.4.1 Treatment Process Used and Materials Treated
17.4.1.1 Indoor Air (Vapor Mitigation System)
Radon-type vapor mitigation systems do not technically treat any of the COCs but rather
prevents them from entering the structure via vapor intrusion. The vapor mitigation system
incorporates a plastic barrier between the ground surface and the overlying structure, with
the operation of a vapor extraction blower beneath the barrier, which allows vapors to
bypass the interior of the structure and be exhausted above the roof.
17.4.1.2 Source Area Treatment
Thermal technologies provide treatment via the volatilization and steam flushing of VOCs
(including the COCs) induced by heating of the subsurface, with soil vapor extraction used
to recover the vapors and steam. The steam and vapors are collected, condensed, and
treated prior to discharge of clean effluent water. ISCO treatment occurs via destructive
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oxidation of organic contaminants (including the COCs) and mineralization to carbon
dioxide, water, and chloride. ISCO is generally capable of treating all organic compounds if
adequate contact with oxidant can be achieved. ISCO treatment would be followed by
enhanced biologically-mediated reductive dechlorination (ERD) in which carbon-source
amendments are injected to enhance natural biological treatment. ERD also can be used as a
stand-alone treatment.
All of the technologies considered are effective in permanently reducing toxicity, mobility
and volume of COCs. However, thermal treatment would be quicker, cost-competitive and
have the least impact on the community.
17.4.1.3 Shallow Ground Water Plume and Hot Spot Treatment
ZVI-PRBs provide treatment via reductive dechlorination as ground water passes through
the PRB under natural ground water flow gradients. ZVI-PRBs are effective for treatment of
chlorinated ethenes and ethanes (including the COCs), select chlorinated pesticides, and
some metals. ISCO treatment occurs via destructive oxidation of organic contaminants
(including the COCs) and mineralization to carbon dioxide, water, and chloride.
ISCO is generally capable of treating all organic compounds if adequate contact with
oxidant can be achieved. ISCO treatment would be followed by enhanced biologically-
mediated reductive dechlorination (ERD) in which carbon-source amendments are injected
to enhance natural biological treatment. ERD also can be used as a stand-alone treatment.
Ground water extraction and treatment provides treatment by extracting ground water,
stripping (volatilizing) VOCs (including the COCs), and treating the vapor stream using
granular activated carbon prior to discharge to the atmosphere. The treated water effluent
is then re-injected into the subsurface.
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All of the technologies considered are effective in permanently reducing toxicity, mobility
and volume of COCs. However, even though ISCO with follow-on ERD is more expensive
than ERD Bio-barrier cleanup goals would be reached quicker.
17.4.1.4 Shallow Ground Water Periphery and Deeper Ground Water
MNA provides treatment via naturally-occurring bacteria, which provide biologically-
mediated reductive dechlorination given appropriate site conditions. MNA can be effective
for many organic compounds, including the COCs. ZVI-PRBs provide treatment via
reductive dechlorination as ground water passes through the PRB under natural ground
water flow gradients. ZVI-PRBs are effective for treatment of chlorinated ethenes and
ethanes (including the COCs), select chlorinated pesticides, and some metals.
ERD provides treatment via enhanced biologically-mediated reductive dechlorination in
which carbon-source amendments are injected to enhance natural biological treatment.
ERD is effective for a variety of organic compounds, including chlorinated ethenes and
ethanes (COCs). Ground water extraction and treatment provides treatment by extracting
ground water, stripping (volatilizing) VOCs (including the COCs), and treating the vapor
stream using granular activated carbon prior to discharge to the atmosphere. The treated
water effluent is then re-injected into the subsurface.
All of the technologies considered are effective in permanently reducing toxicity, mobility
and volume of COCs. However, ERD is less expensive than the other alternatives.
17.4.2 Amount of Hazardous Materials Destroyed or Treated
17.4.2.1 Indoor Air (Vapor Intrusion Mitigation)
The vapor mitigation systems do not provide active treatment, but physically block
contaminants from entering a structure.
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17.4.2.2 Source Area, Shallow Plume Core and Hot Spot, Shallow Plume Periphery,
and Deeper Ground Water Treatment
Approximately 44.5 MG of ground water and 6,500 yd3 of soil will be treated at the site. It is
anticipated that each of the proposed technologies can remove the quantity of COCs to meet
the site RAOs.
17.4.3 Degree of Expected Reductions in Toxicity, Mobility, and Volume
17.4.3.1 Indoor Air (Vapor Intrusion Mitigation)
The vapor mitigation systems do not provide active treatment of COCs, but physically block
contaminants from entering a structure.
17.4.3.2 Source Area Treatment
The thermal treatment is anticipated to provide substantial reductions in toxicity, mobility,
and contaminant volume (TMV) and is likely to provide the greatest percent reduction in
source-area concentrations following a single treatment. ISCO is anticipated to provide
substantial reductions in TMV if the oxidants can be adequately distributed to provide
contact with COCs. Follow-on ERD also is anticipated to provide substantial reductions in
TMV if the carbon-source amendments can adequately sustain biologically-mediated
subsurface reactions. Depending on site-specific conditions to be further characterized
during the Remedial Design, ISCO and ERD can lead to the generation of equally or more
toxic intermediary products during treatment. These intermediary products are generally
only temporarily present during treatment and can include cis-1,2-DCE or VC with ERD, or
acetone and leached metals (such as hexavalent chromium) with ISCO. As with follow-on
ERD, stand-alone ERD is anticipated to provide substantial reductions in TMV.
17.4.3.3 Shallow Ground Water Plume Core and Hot Spot Treatment
ZVI-PRBs have been designed to provide complete treatment of ground water to the RAOs
upon a single pass through the wall and therefore provide substantial reduction of TMV,
although technically the ZVI-PRB results in an increase in anthropogenic materials in the
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subsurface due to the placement of iron. The presence of sorbed-phase COCs between PRB
walls will provide for continued dissolution and recontamination of ground water between
the walls, and will require an extended treatment time.
ISCO is anticipated to provide substantial reductions in TMV if the oxidants can be
adequately distributed to provide contact with COCs. Follow-on ERD also is anticipated to
provide substantial reductions in TMV if the carbon-source amendments can adequately
sustain biologically-mediated subsurface reactions. Depending on site-specific conditions to
be further characterized during the Remedial Design, ISCO and ERD can lead to the
generation of equally or more toxic intermediary products during treatment. These
intermediary products are generally only temporarily present during treatment and can
include cis-1,2-DCE or VC with ERD, or acetone and leached metals (such as hexavalent
chromium) with ISCO. As with follow-on ERD, stand-alone ERD is anticipated to provide
substantial reductions in TMV.
The pump and treat technology is anticipated to quickly reduce toxicity by removing
ground water with high-concentrations of COCs, and will limit mobility by providing
hydraulic plume containment. The volume of the plume is expected to gradually be
reduced as treatment proceeds. As with ZVI-PRBs, sorbed-phase contaminants are expected
to provide a long-term source of COCs in ground water, requiring an extended treatment
time.
17.4.3.4 Shallow Ground Water Periphery and Deeper Ground Water
MNA may provide sustained moderate reductions in TMV over long time periods if
appropriate site conditions are confirmed at the Site. ZVI-PRBs have been designed to
provide complete treatment of ground water to the RAOs upon a single pass through the
wall and therefore provide substantial reduction of TMV, although technically the ZVI-PRB
results in an increase in anthropogenic materials in the subsurface due to the placement of
iron. The presence of sorbed-phase COCs between PRB walls will provide for continued
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dissolution and recontamination of ground water between the walls, and will require an
extended treatment time.
ERD is anticipated to provide substantial reductions in TMV if the carbon-source
amendments can adequately sustain biologically-mediated subsurface reactions.
Depending on site-specific conditions to be further characterized during the Remedial
Design, ERD can lead to the generation of equally or more toxic intermediary products
during treatment. These intermediary products are generally only temporarily present
during treatment and can include cis-1,2-DCE or VC.
The Pump and Treat technology is anticipated to quickly reduce toxicity by removing
ground water with high-concentrations of COCs, and will limit mobility by providing
hydraulic plume containment. The volume of the plume is expected to gradually be
reduced as treatment proceeds. As with ZVI-PRBs, sorbed-phase contaminants are expected
to provide a long-term source of COCs in ground water, requiring an extended treatment
time.
17.4.4 Type of Residuals Remaining After Treatment
17.4.4.1 Indoor Air (Vapor Intrusion Mitigation)
With the vapor mitigation systems, the vapor intrusion pathway is removed by installing a
physical barrier and residual COCs inside the structure will quickly dissipate. If no other
active treatment is conducted at the site, the original COCs will remain in the subsurface as
residuals since the barriers do not provide treatment. Given active treatment of the site,
virtually no residuals are ultimately anticipated in the subsurface.
17.4.4.2 Source Area Treatment
Completely successful thermal treatment leaves virtually no residual volatile COCs behind,
as they are all volatilized. Residuals following direct oxidation by ISCO will include carbon
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dioxide, water, and chloride. Depending on the oxidant used, other residuals may include
metal oxides (such as manganese oxide) or dissolved metals (such as dissolved manganese).
After follow-on ERD (or stand-alone ERD), residuals will proceed through the series of
degradation products TCE, DCE, VC, ethene, and ultimately to carbon dioxide, water, and
chloride. If an oversupply of carbon-source amendment is applied, then residual
amendment could remain in the subsurface for a period of time following treatment, but
will ultimately be consumed.
17.4.4.3 Shallow Ground Water Plume Core and Hot Spot Treatment
As ground water passes through each ZVI-PRB wall, reductive dechlorination will progress
from PCE through TCE, DCE, VC, and ethene, then ultimately to carbon dioxide, water, and
chloride as water passes out of the barrier. Following treatment, the ZVI material will
remain in the subsurface. Residuals following direct oxidation by ISCO will include carbon
dioxide, water, and chloride. Depending on the oxidant used, other residuals may include
metal oxides (such as manganese oxide) or dissolved metals (such as dissolved manganese).
After follow-on ERD (or stand-alone ERD), residuals will proceed through the series of
degradation products TCE, DCE, and VC, ethene, and ultimately to carbon dioxide, water,
and chloride. If an oversupply of carbon-source amendment is applied, then residual
amendment could remain in the subsurface for a period of time following treatment, but
will ultimately be consumed. Residuals following pump and treat include GAC, which will
require offsite disposal or recycling and remediated ground water that will require
reinjection.
17.4.4.4 Shallow Ground Water Periphery and Deeper Ground Water
With MNA, residuals following reductive dechlorination of PCE will proceed through TCE,
DCE, VC, ethene, and ultimately to carbon dioxide, water, and chloride. As ground water
passes through each ZVI-PRB wall, reductive dechlorination will progress from PCE
through TCE, DCE, VC, and ethene, then ultimately to carbon dioxide, water, and chloride
as water passes out of the barrier. Following treatment, the ZVI material will remain in the
subsurface. As ERD is applied, residuals will proceed through the series of degradation
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products TCE, DCE, VC, ethene, and ultimately to carbon dioxide, water, and chloride. If
an oversupply of carbon-source amendment is applied, then residual amendment could
remain in the subsurface for a period of time following treatment, but will ultimately be
consumed. Residuals following pump and treat include granular activated carbon, which
will require offsite disposal or recycling and remediated ground water that will require
reinjection.
17.5 Short-Term Effectiveness
Short-term effectiveness addresses the period of time needed to implement the remedy and
any adverse impacts that may be posed to workers, the community and the environment
during construction and operation of the remedy until cleanup levels are achieved.
The technology combinations for all impacted media have variable impacts with respect to
requiring protection of workers during remedial construction, protection of community
during Remedial Action, and environmental impacts of Remedial Action. The No Action
Alternatives have no impact because there is no remedial construction. For essentially all
active remedial technologies for any impacted media, intrusive work and installation of
required infrastructure, ranging from monitoring wells to PRBs, will present some exposure
to site workers. Risks to site workers can be managed through appropriate health and
safety practices.
17.5.1 Protection of Community During Remedial Actions
All active treatments may require appropriate traffic or access control and notification to
prevent community members from entering a hazardous condition or to prevent
community members from posing a risk to workers conducting remedial activities.
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17.5.1.1 Indoor Air
The vapor mitigation systems involve short-term inconvenience impacts to the specific
property owners where vapor mitigation systems will be installed. The installation of the
systems will require access to the crawlspace or basement beneath the structure for
placement of the plastic barrier, the installation of ventilation piping through the floor and
to the roof within a wall or other inconspicuous location, and installation of a roof vent.
RAOs in indoor air will be achieved by eliminating the vapor intrusion pathway into the
homes.
17.5.1.2 Source Area
The implementation of thermal treatment will require several actions for the protection of
the surrounding community. Air monitoring will be required during drilling, excavation,
and other intrusive infrastructure installation activities. Recovery of vapors with an SVE
system would be necessary to prevent discharge of vapors to the atmosphere or into
overlying structures. Large electricity-handling devices and aboveground treatment
equipment also will be present onsite (electricity distribution system would be
underground) during treatment and will require adequate fencing, setbacks, and warning
notifications. The implementation of ISCO also will require several actions for the
protection of the surrounding community. Air monitoring will be required during drilling
and other intrusive activities. Appropriate safety measures must be implemented when
handling oxidants to prevent contact by community members. Injection of oxidants also
must be controlled to prevent surfacing of oxidants. The implementation of ERD will
require air monitoring during drilling or other invasive activities. RAOs will be achieved in
the Source Area by treating principal threat waste.
17.5.1.3 Shallow Ground Water Plume Core and Hot Spot
The installation of ZVI-PRBs will require several actions for the protection of the
community. Air monitoring will be required during excavation and other invasive
installation activities. Depending on the installation method selected, large open trenches
that may or may not be filled with supportive liquid slurries will be excavated within
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residential areas. Substantial notification, fencing, and other access control will be required
to prevent community members from entering the trenches (especially children). The
excavation of soil during installation is likely to generate hazardous waste, which will
require offsite disposal and must be transported through the community.
Due to the shallow nature of ground water, highly contaminated ground water also may be
generated and will require onsite storage and treatment or offsite disposal. In addition, the
installation activities are likely to produce significant disruptions to local traffic and could
impact the ability of property owners to access their driveways or to utilize their property.
To be effective, PRBs must be installed in precise orientations, and it is unlikely that such an
installation could be performed in a residential area without requiring trenching across
private property.
The implementation of ISCO also will require several actions for the protection of the
surrounding community. Air monitoring will be required during drilling and other
intrusive activities. Appropriate safety measures must be implemented when handling
oxidants to prevent contact by community members. Injection of oxidants also must be
controlled to prevent surfacing of oxidants. The implementation of ERD will require air
monitoring during drilling or other invasive activities.
The implementation of pump and treat will require air monitoring during drilling or other
invasive activities. Air monitoring or modeling also will be necessary to demonstrate
protection of the community from unacceptable air emissions from the treatment plant.
Community-protection measures also will be necessary during trenching activities for the
installation of conveyance piping.
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17.5.1.4 Shallow Ground Water Periphery and Deeper Ground Water
During implementation of MNA, there would be limited impacts to the community;
however, air monitoring would be necessary during drilling and well installation activities.
The installation of ZVI-PRBs will require several actions for the protection of the
community. Air monitoring will be required during excavation and other invasive
installation activities. Depending on the installation method selected, large open trenches
that may or may not be filled with supportive liquid slurries will be excavated within
residential areas. Substantial notification, fencing, and other access control will be required
to prevent community members from entering the trenches (especially children). The
excavation of soil during installation is likely to generate hazardous waste, which will
require offsite disposal and must be transported through the community. Due to the
shallow nature of ground water, highly contaminated ground water also may be generated
and will require onsite storage and treatment or offsite disposal. In addition, the installation
activities are likely to produce significant disruptions to local traffic and could impact the
ability of property owners to access their driveways.
The implementation of ERD will require air monitoring during drilling or other invasive
activities. The implementation of pump and treat will require air monitoring during drilling
or other invasive activities. Air monitoring or modeling also will be necessary to
demonstrate protection of the community from unacceptable air emissions from the
treatment plant.
Community-protection measures also will be necessary during trenching activities for the
installation of conveyance piping.
The MNA Alternative presents the least potential for exposure or risk to site workers, the
community, or the environment as no, or minimal, intrusive work would be conducted.
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17.5.2 Protection of Workers During Remedial Actions
All active treatments may require appropriate traffic or access control to provide protection
to workers conducting remedial activities. Risks posed to workers can be effectively
managed through appropriate health and safety practices and use of appropriate personal
protective equipment (PPE).
17.5.2.1 Indoor Air (Vapor Intrusion Mitigation)
During installation of vapor mitigation systems, air monitoring will be conducted and
workers will wear appropriate PPE including respirators, if conditions warrant.
17.5.2.2 Source Area Treatment
Air monitoring will be required during installation of thermal treatment infrastructure and
appropriate measures must be taken to protect those working with electrical-handling
equipment, both during installation and during active treatment. Air monitoring will be
required during drilling and other invasive activities associated with ISCO and ERD.
Appropriate safety precautions must be taken to prevent exposure to workers from oxidants
when applying ISCO.
17.5.2.3 Shallow Ground Water Plume Core and Hot Spot Treatment
Air monitoring will be required during installation of ZVI-PRBs. Excavation and intrusive
onsite work may pose a threat to workers during installation of ZVI-PRBs. The potential
presence and offsite transport of hazardous waste or highly-contaminated ground water
poses additional threats to workers. Risks can be managed through appropriate waste-
handling practices. Air monitoring will be required during drilling and other invasive
activities associated with ISCO and ERD, and appropriate safety precautions must be taken
to prevent worker exposure to oxidants when applying ISCO. Protection of workers during
installation of a pump and treat system will primarily involve air monitoring during drilling
and invasive activities, trenching safety for conveyance piping, and general construction
safety.
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17.5.2.4 Shallow Ground Water Periphery and Deeper Ground Water
Air monitoring will be required during drilling and well-installation activities associated
with MNA. Air monitoring also will be required during installation of ZVI-PRBs.
Excavation and intrusive onsite work may pose a threat to workers during installation of
ZVI-PRBs. The potential presence and offsite transport of hazardous waste or highly-
contaminated ground water poses additional threats to workers. Risks can be managed
through appropriate waste-handling practices. Air monitoring will be required during
drilling and other invasive activities associated with ERD. Protection of workers during
installation of a pump and treat system will primarily involve air monitoring during drilling
and invasive activities, trenching safety for conveyance piping, and general construction
safety.
17.5.3 Environmental Impacts
17.5.3.1 Indoor Air (Vapor Intrusion Mitigation)
The vapor mitigation systems will exhaust extracted soil vapors into the atmosphere. The
extracted vapors are treated onsite prior to discharge into the atmosphere.
17.5.3.2 Source Area Treatment
Thermal treatment will require the control of offgas emissions during the active treatment
period. No adverse environmental conditions are anticipated for the ISCO or ERD
treatments other than the potential generation of intermediary products during treatment
(such as, acetone or leached metals for ISCO or VC for ERD).
17.5.3.3 Shallow Ground Water Plume Core and Hot Spot Treatment
The installation of ZVI-PRBs can pose a threat to the environment since hazardous waste is
likely to be generated and transported offsite for disposal. Environmental risk can be
managed using appropriate hazardous waste handling practices. There may be limited
environmental risk due to the residual iron in the subsurface following treatment, but little
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study has been conducted regarding any such risk. No adverse environmental conditions
are anticipated for the ISCO or ERD treatments other than the potential generation of
intermediary products during treatment (such as, acetone or leached metals for ISCO or VC
for ERD). For the pump and treat system, no environmental impacts are anticipated if
appropriate air emissions treatment is incorporated and ground water reinjection is
successful.
17.5.3.4 Shallow Ground Water Periphery and Deeper Ground Water
Treatment using MNA is passive in nature and high concentrations of COCs may persist in
ground water for an extended period of time, and may present unacceptable risk to the
environment. The installation of ZVI-PRBs can pose a threat to the environment since
hazardous waste is likely to be generated and transported offsite for disposal.
Environmental risk can be managed using appropriate hazardous waste handling practices.
There may be limited environmental risk due to the residual iron in the subsurface
following treatment, but little study has been conducted regarding any such risk. No
adverse environmental conditions are anticipated for the ERD treatment other than the
potential generation of intermediary products during treatment (such as, VC). For the
pump and treat system no environmental impacts are anticipated if appropriate air
emissions treatment is incorporated and ground water reinjection is successful.
17.5.4 Time Until Remedial Action Objectives Are Achieved
The time over which RAOs would be met varies by technology combination and media.
Generally speaking, based on the available information, the following extended Remedial
Action time periods are assumed for the following technologies to meet RAOs: PRB wall
remediation applications will require over 40 years; ISCO with follow-on ERD would
roughly require 8 years; ERD or bio-barrier applications will require roughly 20 years;
Pump and Treat options will require 40 years of operation or more; and MNA options are
assumed to require at least 40 years of active monitoring. The indoor air vapor mitigation
option would essentially immediately achieve RAOs although long-term compliance with
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RAOs would likely require additional source area and shallow ground water treatment
options to be implemented.
Key assumptions in evaluating the potential time it will take for technology combinations to
meet RAOs are the currently understood site conceptual models for each medium.
17.6 Implementability
Implementability addresses the technical and administrative feasibility of a remedy from
design through construction and operation. Factors such as availability of services and
materials, administrative feasibility, and coordination with other governmental entities are
also considered.
Technical or administrative implementability issues are not expected to be substantially
different for the different technology combinations for the different media. Generally
speaking, the technologies as described in this ROD are considered constructible and
appropriate vendors and equipment are available for hire. However, certain options such as
thermal treatment and PRB installation are somewhat specialized technologies so there are
fewer vendors from which to choose. Administrative exemptions or approvals will
probably be required prior to injection of oxidants, carbon amendments, or reinjection of
treated ground water into the subsurface. Additionally, administrative notifications may be
necessary for the discharge of treated offgas streams.
17.7 Cost
Cost includes estimated capital and O&M costs as well as present worth costs. Present
worth cost is the total cost of an alternative over time in terms of today’s dollar value. Cost
estimates are expected to be accurate within a range of +50 to -30 percent. Estimated costs
associated with each of the remedial alternatives are summarized in Table 18 (Cost
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Summary for Remedial Alternatives). The estimated costs associated with the Selected
Remedy are detailed in Appendix B (Cost Estimate Details for Selected Remedy). The total
cost for the Preferred Remedy for the Site is approximately $29.5 million.
Source Area
The cost is competitive among all alternatives with the exception of the No Action
Alternative and is within 1 percent difference. The cost for thermal treatment, the
Preferred Alternative, is approximately $8.02 million.
Shallow Ground Water Plume Core and Hot Spot
The cost for the Pump and Treat remedy is the most expensive and the ERD Bio-
barriers is the least expensive. ZVI-PRB and ISCO with ERD are of intermediate
cost. ISCO with Follow-On ERD, the Preferred Alternative is approximately
$6.73 million.
Shallow Ground Water Plume Periphery
ZVI-PRB and Pump and Treat are the most expensive remedies. MNA is the least
expensive and ERD Bio-barriers, the Preferred Alternative, is approximately
$3.27 million.
Deeper Ground Water Plume
ZVI-PRB in combination with ERD Bio-barriers and Pump and Treat are the most
expensive remedies. MNA is the least expensive and ERD Bio-barriers alone, the
Preferred Alternative, is approximately $7.22 million.
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17.8 State Acceptance
The NMED agrees with EPA’s recommendations of the Selected Remedy.
17.9 Community Acceptance
The EPA conducted a public meeting on April 20, 2006, to present the Proposed Plan (EPA
2006) to the public and presented the following preferred alternative for the various
impacted media at the site:
1. Indoor Air – Vapor Mitigation
2. Source Area – Thermal Treatment
3. Shallow Plume Core and Hot Spot – ISCO with Follow-on ERD (Flexible)
4. Shallow Ground Water Plume Periphery – ERD Bio-barrier
5. Deeper Ground Water – ERD Bio-barrier
The community did not present any opposition to any of the alternatives presented
including the Selected Remedy either during the meeting or during the 30-day comment
period. Based on the comments received the community accepts all of the alternatives
including the Selected Remedy presented in this ROD.
17.10 Summary of Comparative Analysis of Alternatives
A summary of the comparative analysis is shown in Tables 14 through 18.
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18.0 Principal Threat Wastes
The NCP establishes an expectation that EPA will use treatment to address the principal
threats posed by a Site wherever practicable (NCP §300.430(a)(1)(iii)(A)). Identifying
principal threat wastes combines concepts of both hazard and risk. In general, principal
threat wastes are those source materials considered to be highly toxic or highly mobile,
which generally cannot be contained in a reliable manner or would present a significant risk
to human health or the environment should exposure occur. Conversely, nonprincipal
threat wastes are those source materials that generally can be reliably contained and that
would present only a low risk in the event of exposure. The manner in which principal
threats are addressed generally will determine whether the statutory preference for
treatment as a principal element is satisfied.
The source areas and portions of the downgradient ground water at the site are
contaminated with chlorinated solvents possibly containing DNAPL. DNAPL’s are
considered to be "principal threat wastes" because COCs concentrations are present that
pose a significant risk under a residential exposure scenario. Through the use of treatment
as a principal element, the response action will satisfy the preference for treatment and
reduce the mobility of the hazardous source material that constitutes the principal threat
wastes at the site. The EPA has determined that the potential future use of ground water at
the site is drinking water. The principal threat wastes, if left in the source areas and
downgradient ground water, would pose a significant risk to residents living in the area.
In the Source Area, thermal Treatment and ISCO with follow-on ERD will treat the principal
threat waste to achieve RGs. ERD alone may not be sufficient to treat principal threat waste
in the Source Area. The shallow plume core and hot spot is not anticipated to contain
principal threat waste. However, should principal threat waste be present within the
Shallow Plume Core and Hot Spot, ISCO with follow-on ERD is expected to provide
effective treatment. Other considered technologies may not be sufficient to treat principal
threat waste, if present within the shallow plume core and hot spot.
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19.0 Selected Remedy
The EPA will implement the Selected Remedy in phases to optimize the treatment in the
various site-impacted media. The Selected Remedy for the various impacted media and the
order in which they will be implemented is as follows:
• Indoor Air – Installation of Vapor Mitigation Systems
• Source Area – Thermal Treatment
• Shallow Ground Water Plume Core and Hot Spot – ISCO with Follow-On ERD
• Shallow Ground Water Plume Periphery – ERD Bio-Barrier
• Deeper Ground Water – ERD Bio-Barrier
19.1 Summary of the Rationale for the Selected Remedy
19.1.1 Indoor Air: Vapor Mitigation System
The EPA chose to install vapor mitigation systems as they were the only active remedy that
would protect human health. Vapor mitigation systems are proven and used extensively
across the country to mitigate radon. Chlorinated solvents would be mitigated similar to
radon gas through use of this alternative.
19.1.2 Source Area: Thermal Treatment
The EPA chose the thermal treatment alternative over the other alternatives because this
alternative best meets the cleanup objectives by treating contaminated soils and ground
water with concentrations exceeding RGs at the site. This alternative reduces mobility and
toxicity at the Site by removing the source materials. This alternative is expected to be
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completed in approximately 1 year following construction. Implementation of this
alternative will have less impact on the community than the other alternatives. The cost for
implementation of this remedy is slightly less than other active alternatives.
19.1.3 Shallow Plume Core and Hot Spot – ISCO with Follow-On ERD (Flexible)
The EPA chose ISCO with Follow-on ERD for the shallow plume core because ISCO is more
effective in rapidly removing source materials in the core area. The ISCO technology
combined with follow-on ERD, though more expensive than some of the other alternatives,
will be more effective in removing the COCs in the shortest amount of time. EPA and the
NMED believe this alternative would be protective of human health and the environment,
would comply with ARARs, would be cost-effective, and would utilize permanent solutions
to the maximum extent practicable.
The EPA will be flexible in applying this component of the Selected Remedy in the Shallow
Plume Core and Hot Spot Area. Based on additional information gathered during the Pre-
Design Field Investigation and after implementation of the Thermal Treatment at the Source
Area, EPA will determine the suitability of using the ISCO component and the degree of
ERD bio-barrier treatment required. If the Predesign Field Investigation indicates the
presence of DNAPL in the Shallow Plume Core and Hot Spot Area, EPA will fully
implement the ISCO with Follow-On ERD. If on the other hand ground water investigation
does not indicate DNAPL and ERD is demonstrated to be an effective alternative, then EPA
may choose to implement only the ERD bio-barrier component.
The EPA believes the flexible approach is more prudent for the Shallow Plume Core and
Hot Spot Area because of existing data gaps. While this approach will ensure that the
remedy is protective of human health and the environment, it could save unnecessary costs.
If the ISCO component is not required and only ERD bio-barrier is implemented, the cost for
the Selected Remedy will be reduced by approximately $5 million dollars.
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19.1.4 Shallow Plume Periphery, Deeper Plume: ERD Bio-barrier
The EPA chose this alternative over others for the above two impacted areas because this
alternative best meets the cleanup objectives by treating ground water contaminants
exceeding RGs from the site. Using ERD bio-barriers for both of these impacted ground
water areas would optimize the infrastructure necessary for the remedy and in turn save
costs. Although it is slower than chemical oxidation, ERD provides longer residence time
for the amendments to act. ERD is less dependent on uniform distribution during injection
than ISCO, and the longer residence time allows penetration into low-permeability
sediments. It is less intrusive on private properties since public access can be used for
injecting the amendments. It is the least expensive alternative. Based on information
available at this time, the EPA and the NMED believe the Preferred Alternative would be
protective of human health and the environment, would comply with ARARs, would be
cost-effective, and would utilize permanent solutions to the maximum extent practicable.
Because it would treat the source materials constituting principal threats, the remedy also
would meet the statutory preference for the selection of a remedy that involves treatment as
a principal element for these areas.
19.2 Description of the Selected Remedy
Following is a description of each component of the Selected Remedy. Although the EPA
does not expect significant changes to this remedy, it may change "somewhat" as a result of
the RD and construction processes. Any changes to the remedy described in this ROD
would be documented using a technical memorandum in the Administrative Record, an
Explanation of Significant Differences, or a ROD Amendment, as appropriate and consistent
with the applicable regulations.
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19.2.1 Indoor Air
Vapor intrusion mitigation systems will be installed in those residential structures shown in
Figure 11. The vapor intrusion mitigation systems would be designed and installed
consistent with the EPA Office of Air and Radiation guidance Building Radon Out, A Step-by-
Step Guide on How to Build Radon-Resistant Homes (EPA, 2001).
Specific design elements would depend on the type of foundation at the home. Currently,
only three residences have been evaluated for installation of the vapor mitigation systems.
Of these, two of the residences are built over crawlspaces and one residence has a basement.
The remaining 11 structures in the area are assumed to be similar in construction to the
three evaluated, although one of the structures may be of slab-on-grade construction. Vapor
intrusion mitigation systems would be functionally similar to radon mitigation systems and
consist of placing a plastic liner between the ground surface and the residential living space
for residences with crawlspaces, and ventilating between the liner and the ground surface to
remove vapors before they can enter the living space. Structures with basements and slab-
on-grade construction will require additional components in the design of the vapor
mitigation systems. Specific design elements will be developed during the RD. The
structure located behind the Holiday Cleaners requires further evaluation because of close
proximity to the Holiday Cleaners building. The structure will be monitored further to
ensure that the indoor air is not influenced by the operations of the dry cleaner. Once the
background sources are evaluated further, the EPA will determine if installation of a vapor
mitigation system is warranted for this structure.
19.2.2 Source Areas
Figure 12 shows the extent of source areas at the Holiday Cleaners and the Abandoned Dry
Cleaners buildings. Thermal treatment technology can involve either conductive or
electrical resistance heating of the subsurface. Conductive heating utilizes high
temperatures at subsurface heater probes, installed within steel-cased, steel-screened vapor
extraction wells, to induce heating of the adjacent aquifer matrix by heat conduction. Water
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adjacent to the heater probe/ extraction well is fully vaporized, and steam is extracted using
the vapor extraction well. Electrical resistive heating (ERH) utilizes the subsurface
resistance to electrical current applied between subsurface electrodes/extraction wells to
heat the subsurface less vigorously, vaporizing only a portion of the water within the
subsurface. Steam generated by volatilizing water flushes volatile contaminants to the
vadose zone for extraction by the vapor extraction wells. The two methods are
competitively priced and either can be an effective thermal source area treatment at the
GCSP Site.
The selection of the specific thermal treatment version (conductive versus electrical
resistive) would be made during the RD, based on more detailed Site characterization data
collected during the Preliminary Design Field Investigation.
Regardless of the specific version, thermal treatment would be applied to raise the
subsurface temperature within the treatment volume of the source area to approximately
100 degrees Celsius (°C). The period of time required to reach this temperature is
dependent upon the number and spacing of heater probes/electrodes installed at the site,
but typically requires between 2 to 4 months. During this period of increasing subsurface
temperatures, volatilization of volatile contaminants is encouraged and vapors are collected
within the vapor extraction wells. Once the subsurface temperature reaches the boiling
point of the solvent (typically in the range of 88 to 92°C for PCE depending on its depth
below ground water), the PCE begins to boil, and PCE vapors rise to the vadose zone where
they are collected by the SVE system. When the subsurface temperature has been brought
to 100°C, water begins to vaporize and steam begins flushing volatile contaminants from the
subsurface for collection in the vapor extraction wells. The heating is continued until
concentrations approach the treatment goals. The SVE system provides process control
during thermal treatment, and prevents the migration of vapor or steam outside the
treatment area.
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Final polishing to treatment goals can sometimes be achieved through additional
volatilization over subsequent months as the subsurface slowly cools. Bioactivity is also
likely to increase during the cool-down period and can act as a polishing treatment.
However, due to the one-time nature of this technology, if DNAPL or sorbed-phase soil
contamination remains in the subsurface after the thermal treatment is complete, additional
final polishing by another remedial technology may need to be instituted to achieve RAOs.
For the GCSP Site, it is likely that thermal treatment would need to continue for an extended
period of time once the target subsurface temperature has been reached to even approach
the treatment goals. Additionally, given the very elevated COC levels in the source area,
thermal treatment would need to achieve a very high percentage removal rate (e.g.
99.9 percent or more) to meet the strict RAOs and RGs for the site. It is possible that final
polishing via another treatment technology within the source area or in downgradient
locations, or MNA over time might be necessary.
For either thermal treatment method, a network of heater probes or subsurface electrodes
would be installed within steel-cased, steel-screened vapor extraction wells. The heater
probe/electrode vapor extraction wells would be spaced approximately 15 to 25 ft apart,
with approximately 60 heater probe/electrode vapor extraction wells located across the
larger Holiday Cleaners source area and approximately 10 to 20 heater probe/electrode
wells located across the Abandoned Dry Cleaner source area. Each heater probe/electrode
vapor extraction well would be plumbed to a vapor extraction system to collect steam and
volatilized contaminants and process them at an onsite treatment facility. In addition to the
vapor extraction plumbing, electrical power cables also would be extended to each well to
provide the electricity for the thermal treatment. Temperature monitoring probes also
would be installed to track the increase in subsurface temperatures during treatment. If a
site were undeveloped, the piping and electrical cables would generally be left
aboveground; however, this is not viable in the developed GCSP source areas. Therefore, all
plumbing and electrical components would need to be installed in the subsurface. As a
potential enhancement to the SVE system, horizontal vapor extraction wells could be
installed at the same time as other subgrade plumbing and electrical infrastructure, using a
coarse backfill to enhance vapor recovery.
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19.2.3 Shallow Plume Core and Hot Spot
ISCO is initially applied to rapidly lower dissolved-phase COC concentrations to moderate
levels. The ISCO phase is then followed by injecting carbon-source amendments as a
polishing step for final reduction of COCs.
For treatment of the shallow ground water plume core and hot spot, ISCO would be applied
using a network of closely spaced permanent injection points, screened within the targeted
treatment zone. In this case, the injection points are anticipated to be placed using on-center
spacing of approximately 24 ft. Approximately 221 injection points will be required for
treatment of the area encompassing the shallow plume core and hot spot using ISCO. The
ISCO treatments would be applied from a depth of approximately 8 ft bgs (the top of the
silty sand layer that has been identified as a preferential pathway) to a depth of
approximately 20 ft bgs using the permanent injection points. A conceptual layout of the
ISCO treatment area under this alternative is presented in Figure 13.
The injected oxidant is assumed to be potassium and/or sodium permanganate. Other
oxidants are similarly priced and a final product selection will be made during the RD,
based on more detailed Site characterization data collected during the Preliminary Design
Field Investigation.
ISCO would be applied at the GCSP Site with the intent to replace one full pore volume
with oxidant during an initial injection event, followed by a similar injection at only one-half
the injection wells on a second event. The second injection event would be conducted
within approximately 6 months following the conclusion of the initial event, and would
specifically target plume core or hot spot locations with remaining contamination.
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Site-specific soil oxidant demand (SOD) significantly impacts the dosing frequency required
to reach RAOs in a cost-effective manner. Oxidant dosing assumptions utilized in the FS
(EPA, 2006b) are based on a conservative assumed SOD of 5 mg/kg. SOD values in the
range of 1 mg/kg may reduce the cost of ISCO by 15 to 20 percent, while SOD values in the
range of 10 mg/kg could make ISCO both technically infeasible and cost prohibitive. SOD
will be characterized during the Preliminary Design Field Investigation and those data will
be used to establish appropriate oxidant dosing during the RD.
ISCO injections are anticipated to be performed using high-pressure injection pumps and a
mobile injection trailer. It is assumed that oxidant can be injected into the subsurface at a
rate of 6 gallons per minute (gpm) based on assumptions utilized in the FS (EPA, 2006b). If
this injection rate, at a minimum, cannot be supported at the site, the costs associated with
this alternative may increase significantly due to the large volume of oxidant that must be
injected. Significant additional labor and perhaps infrastructure would be required to
deliver the needed volume of oxidant into the subsurface. If only very low injection rates
can be achieved, it may not be technically feasible to implement this alternative. The
supportable injection rate will be characterized during the Preliminary Design Field
Investigation and those data will be utilized during the RD.
As a polishing treatment for the shallow plume core and hot spot areas, ERD will be applied
within the same permanent injection wells. Each injection well is assumed to be screened
from approximately 8 ft bgs (the top of the silty sand layer that has been identified as a
preferential pathway) to approximately 20 ft bgs for treatment of the shallow plume core
and hot spot.
The carbon-source injections will be performed following conclusion of the ISCO injection
events. For cost estimation purposes, the carbon-source amendment was assumed to be
emulsified vegetable oil (EPA, 2006b). Other carbon-source amendments are similarly
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priced and a final product selection will be made during the RD, based on more thorough
Site characteristics data collected during the Preliminary Design Field Investigation.
The ERD polishing injections will be applied within the shallow plume core and hot spot
areas with the intent to replace one-half of a full pore volume, within the ROI of each
injection well, with the carbon-source amendment during each injection event. Carbon-
source amendment dosing is based on an assumed dissolved-sulfate concentration of
2,000 mg/L, based on available data from the RI. Dissolved-sulfate concentrations and
other geochemical conditions will be further characterized during the Preliminary Design
Field Investigation for use in the RD. A total of five carbon-source injections, performed
once every 15 months, are assumed to complete the ground water polishing and meet the
RAOs.
If the Preliminary Design does not indicate the presence of DNAPL, the EPA in concurrence
with NMED may choose to implement only the ERD bio-barrier component of the remedy.
A conceptual layout of the ERD bio-barrier is shown in Figure 14.
19.2.4 Shallow Ground Water Plume Periphery
Bio-barriers are installed as transects across the ground water plume axis by closely-spaced
injection of carbon-source amendments. Within these carbon-rich zones, or barriers,
biologically mediated reductive dechlorination of the COCs is enhanced and the process
forms a continuous ERD treatment zone to intercept the plume. Installation of multiple bio-
barriers in series achieves RAOs as ground water passes through the treatment areas. At the
GCSP Site, the bio-barriers will be placed utilizing linear transects of permanent injection
points. Injection points along each transect are anticipated to be spaced approximately 25 ft,
on center, with an assumed injection ROI of approximately 15 ft. The use of permanent
wells versus remobilization of a direct-push drilling rig over multiple events will provide
significant cost savings.
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Each injection well is assumed to be screened from approximately 8 ft bgs (the top of the
silty sand) to approximately 20 ft bgs for treatment of the shallow plume periphery.
Bio-barriers will be installed as multiple transects across the shallow plume periphery, with
an assumed total bio-barrier length of approximately 2,400 ft. Under this scenario, the bio-
barriers will be spaced approximately 200 ft apart along the length of the shallow ground
water plume. If combined with the bio-barrier treatment portion of the shallow ground
water plume core and hot spot, bio-barriers would be located so as to provide multiple
transects across the full width of the plume. A conceptual layout of the bio-barrier plume
periphery treatment is presented in Figure 15, and illustrates how the plume periphery bio-
barriers could be used in conjunction with plume core bio-barriers.
The injected ERD carbon-source amendment is assumed to be emulsified vegetable oil.
Emulsified vegetable oil has advantages of being one of the longer lasting available carbon
sources as well as being one of the less viscous amendments, which aids distribution within
low-permeability materials. Other carbon-source amendments are similarly priced and a
final product selection will be made during the RD, based on more detailed site
characterization data collected during the Preliminary Design Field Investigation.
The bio-barriers will be applied within the shallow ground water plume periphery with the
intent to replace approximately one-half the full pore volume, within the ROI of each
injection well, with the carbon-source amendment during each injection event. Site-specific
geochemical conditions, particularly sulfate concentrations, will impact the carbon-source
amendment dosing selected in the RD. Sulfate generally dominates the carbon demand,
interrupting the reductive dechlorination of the COC, and thereby having a significant
impact on carbon-source amendment dosing needs to reach RAOs in a reasonable
timeframe. Dissolved-sulfate concentrations and other geochemical conditions will be
further characterized during the Preliminary Design Field Investigation for use in the RD.
Carbon-source amendment dosing is based on an assumed dissolved-sulfate concentration
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of 2,000 mg/L, based on available data from the RI. A total of 16 carbon-source amendment
injections are assumed over a 20-year period (one injection every 15 months) to meet the
RAOs within the shallow ground water plume periphery.
19.2.5 Deeper Ground Water Plume
The complete vertical extent of contamination is not fully defined at this time. Further
characterization will be conducted during the Preliminary Field Investigation and the
remedy will be implemented such that the entire vertical extent is addressed. The remedy
will be re-evaluated during the design phase if new information regarding the vertical and
horizontal extent of the plume is determined.
Bio-barriers are installed as transects across the ground water plume axis along which
closely-spaced injection of carbon-source amendments will occur to form a continuous ERD
treatment zone across the plume. The bio-barriers will be placed using permanent injection
wells, due to the extended time period and numerous injections required to meet RAOs
with ERD. The use of permanent wells versus remobilization of a direct-push drilling rig
over multiple events will provide significant cost savings.
Bio-barriers will be installed as multiple transects across the deeper ground water plume,
with an assumed bio-barrier length of approximately 1,000 ft for treatment of contamination
at a depth up to 60 ft bgs, and an additional bio-barrier length of approximately 250 ft for
treatment of contamination at a depth up to 80 ft bgs. Two 80-ft deep bio-barriers, each
approximately 125-ft long, are anticipated to be installed to address the deepest known
contamination at the Site, with one transect anticipated to be located on First Street and
another anticipated to be located in the alleyway between First Street and Geis Street.
Injection wells along these deeper transects will be screened between approximately 60 ft
and 80 ft bgs. Multiple approximately 60-ft-deep bio-barriers will be installed with short
lengths anticipated to be located along First Street, in the alleyway between First Street and
Geis Street, near the midpoint of the plume on Geis Street, near the downgradient extent of
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the deeper plume, and limited injections at accessible points at the far downgradient extent
of the deeper plume. A conceptual layout of this arrangement is presented in Figure 16.
The injected ERD carbon-source amendment is assumed to be emulsified vegetable oil.
Other carbon-source amendments are similarly priced and a final product selection will be
made during the RD, based on more detailed Site characterization data collected during the
Preliminary Design Field Investigation. The bio-barriers will be applied within the deeper
ground water plume with the intent to replace approximately one-half the full pore volume,
within the ROI of each injection well, with the carbon-source amendment during each
injection event. Carbon-source amendment dosing is based on an assumed dissolved-
sulfate concentration of 2,000 mg/L, based on available data from the RI. Dissolved-sulfate
concentrations will be further characterized during the Preliminary Design Field
Investigation, since sulfate generally dominates the carbon demand and has a significant
impact on carbon-source amendment dosing. A total of 16 carbon-source amendment
injections are assumed over a 20-year period (one injection every 15 months) to meet the
RAOs within the deeper ground water plume.
19.3 Contingency Remedy
EPA will evaluate the site conditions to determine if monitored natural attenuation
(MNA) is a viable remedial alternative after the first Five-Year Review and after
source control has been established in the Source Areas and the Shallow Ground
Water Plume. If ground water data demonstrates evidence that MNA is occurring
such that RAOs will be met in a timely manner, then EPA may consider proposing
MNA as the remedial strategy for the Shallow Ground Water Periphery and the
Deeper Ground Water Plume. If this alternative is determined to be the most
efficient and effective remedy, then EPA with NMED’s concurrence will issue an
Explanation of Significant Differences (ESD) to document the change in the remedy.
MNA is not a component of the Selected Remedy.
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MNA is a proven ground water remedy at many sites; however, at this time there is
insufficient data to select MNA as a component of the Selected Remedy at the GCSP
Site. The EPA will collect the necessary data for MNA evaluation during the pre-
design investigation phase. The contingency will be invoked not because of a
potential failure of the Selected Remedy but rather as an alternative that would not
only achieve final cleanup goals but also provide significant cost savings to the
agency.
MNA is a proven ground water remedy at many sites; however, at this time there is
insufficient data to select MNA as a component of the Selected Remedy at the GCSP Site.
The EPA will collect the necessary data for MNA evaluation during the predesign
investigation phase. The contingency will be invoked not because of a potential failure of
the Selected Remedy but rather as an alternative that would not only achieve final cleanup
goals but also provide significant cost savings to the agency.
If the Selected Remedy does not appear to be making progress toward achieving the
remedial objectives, the EPA may propose a new remedy in the form of a ROD amendment
or other appropriate regulatory mechanism. “Triggers” that will signal unacceptable
performance of the Selected Remedy include, but are not limited to, the following:
a. Contaminant concentrations in the groundwater at specified locations exhibit an
increasing trend not originally predicted during remedy selection,
b. Near-source wells exhibit large concentration increases indicative of a new or renewed
release,
c. Contaminants are identified in MWs located outside of the original plume boundary,
d. Contaminant concentrations are not decreasing at a sufficiently rapid rate to meet the
remediation objectives, and
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e. Changes in land and/or groundwater use
19.4 Cost Estimate for the Selected Remedy
Appendix B includes details of the estimated costs to implement and construct the Selected
Remedy. The estimated total cost to implement and construct the Selected Remedy
presented in this ROD is $29,500,000. The information in this cost estimate for the Selected
Remedy is based on the best available information regarding the anticipated scope of the
Remedial Alternative.
Changes in the cost elements are likely to occur as a result of new information and data
collected during the engineering design of the Remedial Alternative. Major changes may be
documented in the form of a technical memorandum in the Administrative Record file, an
ESD, or a ROD amendment. This is an order-of-magnitude engineering cost estimate that is
expected to be within +50 to -30 percent of the actual project cost.
19.5 Expected Outcomes of the Selected Remedy
Following are the expected outcomes of the Selected Remedy in terms of resulting land and
ground water uses, the cleanup levels and the risk reduction achieved as a result of the
response action, and the anticipated community impacts.
19.5.1 Available Land Uses
The homes that have indoor vapor mitigation systems will no longer present long-term risk
to residents. The cancer risk from inhalation in the three homes that exceeded the Tier 3
level will be reduced to below the EPA risk of 1 x 10-5. An additional eleven homes will
receive vapor mitigation system to prevent future risk from vapor intrusion.
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19.5.2 Available Ground Water Uses
The remedy will be protective of ground water because all of the source areas will be
removed and active treatment of the plume will reduce the ground water concentrations of
chlorinated solvents below the federal MCL. Remediation at the site will prevent any
potential for vertical migration of contaminants into the deeper aquifer that is the source of
drinking water for the City of Grants. The planned implementation of the Institutional
Controls will help prevent use of ground water before cleanup goals are met.
19.5.3 Final Cleanup Levels
Table 20 shows the final cleanup level for the COCs. The results of the BHHRA indicate that
existing conditions at the site pose an ELCR of greater than 1 x 10-5 for indoor air. In
addition ground water COCs exceed MCLs and state ARARs. Soil COCs exceed NMED
safe levels for residential use. The Selected Remedy will address indoor air through the
installation of vapor mitigation systems and will address ground water and soil through
active treatment. The final cleanup levels are protective of human health and are expected
to restore the ground water and soil. The site is expected to be available for continued
unrestricted residential and commercial land use as a result of the remedy.
20.0 Statutory Determinations
Under CERCLA §121 and the NCP §300.430(f)(5)(ii), the EPA must select remedies that are
protective of human health and the environment, comply with ARARs (unless a statutory
waiver is justified), are cost effective, and utilize permanent solutions and alternative
treatment technologies or resource recovery technologies to the maximum extent
practicable. In addition, CERCLA includes a preference for remedies that employ treatment
that permanently and significantly reduces the volume, toxicity, or mobility of hazardous
wastes as a principal element and a bias against offsite disposal of untreated wastes. The
following sections discuss how the Selected Remedy meets these statutory requirements.
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20.1 Protection of Human Health and the Environment
The Selected Remedy for the indoor air, soil, and ground water at this site will be protective
of human health and the environment. Installation of vapor mitigation systems will address
vapor intrusion and reduce cancer risk to below safe levels.
Removal of the principal threat wastes in the soil and ground water in the source areas and
active treatment of ground water in the shallow plume core and hot spot, shallow plume
periphery, and deeper plume is expected to restore the ground water to below drinking
water standards.
20.2 Compliance with Applicable or Relevant and Appropriate Requirements
The NCP §300.430(f)(5)(ii)(B) and (C) require that a ROD describe the Federal and State
ARARs that the Selected Remedy will attain or provide justification for any waivers.
ARARs include substantive provisions of any promulgated Federal or more stringent State
environmental standards, requirements, criteria, or limitations that are determined to be
legally ARARs for a CERCLA site or action. Applicable requirements are those cleanup
standards, standards of control, and other substantive environmental protection
requirements, criteria, or limitations promulgated under Federal or State law that
specifically address a hazardous substance, pollutant, contaminant, remedial action,
location, or other circumstance found at a CERCLA site. Relevant and appropriate
requirements are requirements that, while not legally "applicable" to circumstances at a
particular CERCLA site, address problems or situations sufficiently similar to those
encountered at the site that their use is relevant and appropriate. The ARARs are presented
below and in more detail in Table 12.
Chemical, location, and action-specific ARARs include the following:
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• Safe Drinking Water Act MCLs (40 CFR Part 141), which specify acceptable
concentration levels in ground water that serves as a potential drinking water aquifer
• Clean Air Act applicable to emissions from stationary sources
• Clean Water Act for any discharges from the site
• Hazardous Waste Regulations (40 CFR 261) for waste disposal
• U.S. Department of Transportation (DOT) Regulations for transportation of hazardous
waste (49 CFR 171 and 180)
• New Mexico Hazardous Waste Regulations (20.4 New Mexico Administrative Code
[NMAC])
• New Mexico Air Regulations (20.2 NMAC)
• New Mexico Water Quality Control Commission Regulations (20.6.2 NMAC)
20.3 Cost Effectiveness
The Selected Remedy is cost effective because the remedy's costs are proportional to its
overall effectiveness (see 40 CFR §300.430(f)(l)(ii)(D)). This determination was made by
evaluating the overall effectiveness of those alternatives that satisfied the threshold criteria
(i.e., that are protective of human health and the environment and comply with all Federal
and any more stringent State ARARs, or as appropriate, waive ARARs). Overall
effectiveness was evaluated by assessing three of the five balancing criteria in combination
(long-term effectiveness and permanence; reduction in toxicity, mobility, and volume
through treatment; and short-term effectiveness). The overall effectiveness of each
alternative was then compared to each alternative's costs to determine cost effectiveness.
The relationship of the overall effectiveness of this remedial alternative was determined to
be proportional to its costs and hence represents a reasonable value for the money to be
spent.
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The estimated present worth cost of one component (ISCO with Follow-On ERD for Shallow
Plume Core and Hot Spot) is pushing the total cost of the Selected Remedy slightly higher
compared to other alternative combinations providing active treatment. However, the
Selected Remedy offers a much higher degree of protectiveness and overall effectiveness
than any of the other alternatives because it offers mitigation, treatment, and removal of all
wastes versus no action.
20.4 Utilization of Permanent Solutions to the Maximum Extent Practicable
EPA has determined that the Selected Remedy represents the maximum extent to which
permanent solutions and treatment technologies can be utilized in a practicable manner at
the site. Of those alternatives that are protective of human health and the environment and
comply with ARARs, the EPA has determined that the Selected Remedy provides the best
balance of tradeoffs in terms of the five balancing criteria, while also considering the
statutory preference for treatment as a principal element, bias against offsite treatment and
disposal, and considering State and community acceptance.
The Selected Remedy treats the source area soil and ground water potentially containing
DNAPL constituting principal threats at the Site. The Selected Remedy satisfies the criteria
for long-term effectiveness by removing all chlorinated solvents contamination from the soil
and ground water. The Selected Remedy does not present short-term risks different from
the other treatment alternatives. There are no special implementability issues that set the
Selected Remedy apart from any of the other alternatives evaluated.
20.5 Preference for Treatment as a Principal Element
The EPA has determined that the treatment of the source area wastes satisfies the statutory
preference for the selection of a remedy that involves treatment as a principal element. By
treating the contaminated soils and ground water by active remediation technologies, the
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Selected Remedy addresses principal threats posed at the site utilizing treatment as a
significant portion of the remedy.
20.6 Five-Year Review Requirements
CERCLA §121(c) and the NCP §300.430(f)(5)(iii)(C) provide the statutory and legal bases for
conducting Five-Year Reviews. Because this remedy is expected to take at least 20 years to
achieve the RAOs within portions of the GCSP Site, it will result in hazardous substances
remaining onsite in the ground water and possibly in the soils (below 1.5 ft bgs) above levels
that allow for unlimited use and unrestricted exposure. A statutory review will be
conducted within 5 years after initiation of the RA to ensure that the remedy is, or will be,
protective of human health and the environment.
21.0 Documentation of Significant Changes
From Preferred Alternative of Proposed Plan
The EPA has not made any significant changes to the remedy, as originally identified in the
Proposed Plan. The Proposed Plan was released for public comment on April 12, 2006. The
public comment period for the Proposed Plan was held from April 12, 2006 to May 11, 2006.
The EPA held a public meeting on April 20, 2006 to present the preferred alternative in the
Proposed Plan. The EPA reviewed and responded to written and verbal comments
submitted during the public comment period in the Responsiveness Summary (Part 3 of this
ROD).
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 2 – THE DECISION SUMMARY 2-127
22.0 State Role
The NMED, on behalf of the State of New Mexico, has reviewed the various alternatives and
has indicated its support for the Selected Remedy. NMED’s position on the other
alternatives are indicated in Tables 14-18.
The State has also reviewed the RI/FS (EPA, 2005a), BHHRA (EPA, 2005b), to determine if
the Selected Remedy is in compliance with applicable or relevant and appropriate State
environmental laws and regulations. The State of New Mexico concurs with the Selected
Remedy for the Site (Appendix C − NMED Concurrence with the Selected Remedy).
Part 3. Responsiveness Summary
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-1
Part 3: Responsiveness Summary
23.0 Responsiveness Summary
The Responsiveness Summary (Appendix D) summarizes information about the views of
the public and the support agency regarding both the remedial alternatives and general
concerns about the site submitted during the public comment period. This summary also
documents, in the record, how public comments were integrated into the decision making
process.
The Administrative Record file for the site, located at the University of New Mexico
Campus, Grants and the EPA's Region 6 office, contains all of the information and
documents supporting this ROD. The comment period for the Proposed Plan for the Site
opened on April 12, 2006 and ended on May 11, 2006. This Administrative Record file
includes a transcript of the public meeting held by the EPA on April 20, 2006 to describe the
preferred alternative.
23.1 Stakeholder Issues and Lead Agency Responses
23.1.1 NMED Comments
Comment 1
In reference to the Land and Ground Water Use Assumptions - NMED emphasizes that the
New Mexico Water Quality Control Commission (NMWQCC) Regulations, NMAC
20.6.2.4101.A(1) requires that all ground water of the State of New Mexico with a TDS of
<10,000 mg/l be remediated or protected for use as domestic and agricultural water supply.
Although the contaminated ground water (from 5 to 80 ft bgs) at the site is not currently
used as a drinking water supply, there are no enforceable institutional controls that would
prohibit the use of this aquifer, now or in the future, as a drinking water supply. The fact
that three shallow private wells exist within the site boundaries is evidence that the aquifer
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-2
can be used for beneficial use. As proposed, ground water must be remediated to the more
stringent requirements of the Federal Safe Drinking Water standards (MCLs) and/or
NMWQCC standards.
EPA Response:
Comment noted. EPA’s final clean up levels for the COCs at this Site is federal MCL and
NMWQCC standards.
Comment 2
Preliminary Remediation Goals and use of 1x10-4 excess lifetime cancer risk (ELCR) as the
targeted cleanup level - The National Contingency Plan established a targeted risk level 1 x
10-6 as a “point of departure” for determining remediation goals. There has been no
justification presented by EPA to modify this targeted risk level and justify the use of a less
stringent risk-based clean up level. At a minimum, an ELCR of 1 x 10-5 and an HI of 1
which is consistent with the NMWQCC Regulations and NMED’s Technical Background
Document for Development of Soil Screening Levels, Revision 3.0, August 2005, should be used
for establishing targeted cleanup levels for indoor air and soil. NMED requests that the
PRGs for COCs in soil and from vapor impacts be established using at least a 1 x 10-5 ELCR
and an HI of 1 and a residential land use scenario.
EPA Response:
1E-06 is the point of departure, and EPA has the flexibility to modify cleanup levels for
carcinogens within the range of 1E-06 to 1E-04, especially when considering site-specific
conditions. This is indicated in the NCP (40 CFR 300.430(e)(2)(i)(A)(2 ):
“For known or suspected carcinogens, acceptable exposure levels are generally concentration levels
that represent an excess upper bound lifetime cancer risk to an individual of between 10-4 and 10-6
using information on the relationship between dose and response.”
The EPA agrees with NMED’s concerns regarding uncertainties at the Site and will take
Remedial Action at the lower risk level (1x10-5).
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-3
Comment 3
In reference to risk and the preliminary remediation goals. NMED does not support the use
risk based clean up levels that are less stringent than residential clean up levels for this site.
The site is located in a mixed commercial and residential use area and there are no
enforceable institutional controls that can be implemented to restrict future land use.
Therefore, the more restrictive clean up levels, i.e. residential, should be used.
EPA Response:
EPA will use NMED’s Guidance document (Technical Background Document for
Development of Soil Screening Levels, Revision 3.0, August 2005) on Soil Screening Levels
to establish clean up levels based on residential use.
Comment 4
In reference to the flexible approach in selection of the final remedy for the Shallow Plume
Core and Hot Spot Area - NMED is concerned with how the final selection between ISCO
and ERD will be determined due to the difficulties associated with detecting the DNAPL in
the field. NMED is concerned that a significant amount of time and expense could be
expended without conclusively determining whether or not DNAPL is absent from this
area. In addition, the pre-design investigations proposed in the Feasibility Study did not
include investigation activities associated with determining the nature and extent of
DNAPL but instead concentrated on definition of the dissolved phase plume and soil
contamination in the two source areas. As stated in the RI report and in literature on the
subject, it is generally assumed that DNAPL is present if ground water exceeds 1 to 5
percent of the chemicals solubility limit in water and the dissolved PCE concentrations
observed within the Plume Core Area are as high as 35%. At this concentration it should be
assumed that DNAPL is present in close proximity to the sample locations and ISCO is
better suited for this condition. Finally, because ISCO with follow-on ERD alternative
addresses the entire plume through the installation of a grid pattern of wells the ISCO
alternative is more amenable to treating the Core Plume/Hotspot area verses the passive
nature of diffusion associated with the ERD alternative. If residual DNAPL is present
between the ERD bio-barriers, the likelihood of effective and timely clean-up using the ERD
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-4
bio-barrier alternative is greatly reduced. Therefore, NMED may not support the use of
ERD as the stand alone remedial technology for the Shallow Plume Core and Hot Spot area.
EPA Response:
EPA’s policy is to treat principal threats posed by the Site through use of treatment
technologies. By utilizing treatment as a significant portion of the Selected Remedy, the
statutory preference for remedies that employ treatment as a principal element is satisfied.
The EPA agrees and will select ISCO with Follow-On ERD (Flexible) treatment approach for
the Shallow Plume Core and Hot Spot for the following reason:
Thermal treatment at the Source Area is expected to achieve complete removal of principal
threat waste. After Source Area treatment is complete and if it can be demonstrated that the
principal threat waste no longer exists in the Shallow Plume Core and Hot Spot area then
the EPA will re-evaluate the two treatment technologies (ISCO/with Follow-On ERD or
ERD alone) to determine which one of these better meets the Statutory Preference for
Treatment. Based on this determination the EPA will implement either of the two
technologies to address the Shallow Plume Core and Hot Spot Area.
23.1.2 Community Comments
The following comments were received from members of the public that were in attendance
at the Proposed Plan public meeting held on April 20, 2006.
Comment 1
How was the contamination originally verified at the GCSP Site?
EPA Response:
The NMED-PSTB discovered chlorinated solvents in ground water at the GCSP Site during
a UST investigation at the Allsup’s 200 gas station in 1993. Following the discovery, NMED
conducted two years of ground water monitoring at the Allsup’s monitoring wells to verify
contamination.
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-5
Comment 2
Are the depths of the City Drinking Water wells known?
EPA Response:
Yes. City well Grants B-40 is screened at a depth from 246 feet (ft) below ground surface
(bgs) to 346 ft bgs and the total depth of the well is 367 ft bgs. The second City well, Grants
B-38, is screened between 149 ft bgs and 300 ft bgs and the total depth of this well is 300 ft
bgs. Both of these wells are upgradient and are located approximately 1.5 miles northwest
of the GCSP Site.
Comment 3
Are the City wells located in the same aquifer that is impacted at the GCSP Site?
EPA Response:
No. The contamination at the GCSP Site is in a shallow aquifer and the vertical extent is not
fully known at this time. The City drinking water wells pump water from much greater
depths, and are upgradient of the GCSP Site. The maximum depth at which contamination
was detected during the RI is 85 ft bgs. The EPA will fully characterize the maximum depth
of contamination during the Pre-Design Field Investigation.
Comment 4
Is the project funded for the Remedial Design?
EPA Response:
Yes. Funding for Remedial Design has been planned for fiscal Year 2006.
Comment 5
Are there many other sites in the country similar to Grants?
EPA Response:
Yes. There are a number of other Superfund sites in the country that are similar to Grants.
In New Mexico alone there are five sites, including the GCSP Site, where EPA is cleaning up
ground water contaminated with chlorinated solvents. These five sites include Fruit
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-6
Avenue Plume, Albuquerque; North Railroad Avenue Plume, Espanola; McGaffey and
Main, Roswell; Griggs and Walnut, Las Cruces; and the GCSP Site, Grants.
Comment 6
Is the bio-barrier wall a physical wall installed underground?
EPA Response:
Bio-barrier walls are not actual physical walls but function as a wall when nutrients are
injected across sections of the plume. Injection points are closely spaced along a line across
the plume, such that the aquifer between each injection point is filled with the injected
oxidant or carbon source amendment. When the oxidant or carbon source amendments are
injected into the ground they permeate into the aquifer and begin treating the ground water.
Zero-valent iron permeable reactive barriers are actual physical walls constructed of iron
filings installed within trenches dug across the plume. The walls required for the GCSP Site
would be as thick as 36 inches and up to 60 ft deep. A zero-valent iron permeable reactive
barrier was considered as one of the alternatives for the Site but was not chosen as the
Selected Remedy.
Comment 7
Will the public be notified when a final decision is made regarding the Preferred Remedy?
EPA Response:
Yes. The EPA will notify the community of the final selection of the remedy after it reviews
and responds to all the comments received during the comment period. Newspaper
notification will be made in the local newspaper when the Record of Decision is signed.
24.0 References
EPA, 2006a. Proposed Plan (referenced on pg 2-9) EPA, 2006b. FS (referenced on pg 2-10) EPA, 2005a. Remedial Investigation Report, Grants Chlorinated Solvents Plume Site, Grants, Cibola County, New Mexico. U.S. Environmental Protection Agency. July.
GRANTS CHLORINATED SOLVENTS PLUME SITE, GRANTS, NM, RECORD OF DECISION
PART 3 – RESPONSIVENESS SUMMARY 3-7
EPA, 2005b. Baseline Human Health Risk Assessment, Grants Chlorinated Solvents Plume, Superfund Site, Grants, New Mexico. July. EPA, 2002. Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils. U.S. Environmental Protection Agency. EPA, 2001. Building Radon Out, A Step-by-Step Guide on How to Build Radon-Resistant Homes. EPA, 1999. Use of Monitored Natural Attenuation at Superfund, RCRA Corrective Action, and Underground Storage Tank Sites. OSWER Directive Number 9200.4-17P. April. EPA, 1993. Presumptive Remedies: Site Characterization and Technology Selection for CERCLA Site With Volatile Organic Compounds in Soils. NMED, Ground Water Quality Bureau, Superfund Oversight Section, 2001. Site Inspection Report, Grants Chlorinated Solvents Plume Site, CERCLIS ID: NM0007271768, Cibola County, New Mexico. April. Tetra Tech EM, Inc., 2003. Secondary Investigation Report, Allsup’s 200.
Tables and Figures
Table 1Criteria Used for Evaluation of Indoor Air
Tier Action
References for the non-Cal-EPA Action
Levels Notes
PCE TCETCE
Cal-EPAcis-1,2-
DCEVinyl
ChlorideCPL Evaluate the need for temporary relocation of
occupants from a structure during implementation of mitigation measures.
1,360 11,000 11,000 790 1,290 ATSDR, 2003 Action level is based on Agency for Toxic Substances and Disease Registry (ATSDR) minimal risk level (MRL) for 14 day exposure. They are set below levels that, based on current information, might cause adverse health effects in the peoplemost sensitive to such substance-induced effects.
Tier 1 No further action is warranted to evaluate potential concentrations in indoor air.
<3.2or outdoor
background
<0.17or outdoor
background
<12.2 <35or outdoor
background
<1.1or outdoor
background
EPA, 2002a; EPA, 2002b Action level is based on target cancer risk level of 10-5 or a noncancer HQ of 1. Values presented here are based on EPA Region 6 media-specific screening levels in air.
Tier 2 Evaluate the need for additional sampling (outdoor soil gas sampling) in these locations. Offer to perform indoor air monitoring annual at residences where these concentrations were detected.
3.2 - 32or outdoor
background
0.17 - 1.7or outdoor
background
12.2 - 122 35 -105or outdoor
background
1.1 - 11or outdoor
background
EPA, 2002a; EPA, 2002b Action levels correspond to a target cancer risk range between 10-5 and 10-4. For noncarcinogens, action levels correspond to a noncancer hazard quotient between 1 and 3. A HQ of 1 corresponds to a concentration in air that is intended to protect the public including sensitive populations over a lifetime of exposure, and is based on the most sensitive noncancer health effect associated with that chemical. Some EPA Regions use a hazard quotient of 3 for evaluating selection of remedial alternatives.
Tier 3 Evaluate the need for mitigation measures (including additional investigation) at the structure. Mitigation measures that may be considered could include soil vapor extraction (outdoors), sealing cracks and crevices indoors, installation of subsurface depressurization systems or other measures as appropriate.
Review site conditions, evaluate the need to conduct sampling at additional structures located nearby.
>32 >1.7 >122 >105 >11 EPA, 2002a; EPA, 2002b Action levels correspond to a target cancer risk of 10-4. For noncarcinogens, action levels correspond to a noncancer hazard quotient between 1 and 3. A HQ of 1 corresponds to a concentration in air that is intended to protect the public including sensitive populations over a lifetime of exposure, and is based on the most sensitive noncancer health effect associated with that chemical. Some EPA Regions use a hazard quotient of 3 for evaluating selection of remedial alternatives.
Key
CPL - Contingency Planning LevelATSDR, 2003. Minimal Risk Levels for Hazardous Substances, January 2003 http://www.atsdr.cdc.gov/mrls.htmlEPA. 2002a. EPA Region 6 media-specific screening levels, October 2002.EPA. 2002b. Draft Guidance for Evaluating the Vapor Intrusion to Indoor Air Pathway from Groundwater and Soils. November 2002Benzene, toluene, ethylbenzene, xylenes (BTEX) and methyl-tert-butyl ether (MTBE) were evaluated by comparison with ambient background concentrations in air.
Action Levels (µg/m3)
Updated TCE action level has been calculated based on toxicity values developed by the California Environmental Protection Agency. Reportedly, the U.S. Office of Research and Development has encouraged Regions to use alternate toxicity values for TCE than the those values presented in USEPA's Draft Risk Characterization for TCE, prepared August 2001. USEPA Regions 4 and 8 have stated that they will be using an alternative toxicity value for addressing TCE risks. This alternative value, provided by Cal-EPA has been recommended for use by USEPA Region 4, and is provided here for evaluation of indoor air analytical data.
Page 1 of 1 December 2005
Table 2Summary of Chemicals of Concern and
Medium-Specific Exposure Point Concentrations (Ground Water)
Scenario Timeframe: FutureMedium: Ground WaterExposure Medium: Ground Water
UnitsMin Max
Tap Water Benzene 0.32 LJv 930 Jv µg/L 5/18 930 µg/L MAX
Bromoform 0.59 LJ 89 = µg/L 8/18 89 µg/L MAX
cis-1,2-Dichloroethene 1.9 LJ 1500 = µg/L 17/18 1500 µg/L MAX
Tetrachloroethene 2.7 = 31000 = µg/L 15/18 31000 µg/L MAX
trans-1,2-Dichloroethene 0.12 LJ 140 = µg/L 16/18 140 µg/L MAX
Trichloroethene 13 = 4800 = µg/L 16/18 4800 µg/L MAX
Vinyl Chloride 0.081 LJ 14 LJ µg/L 11/18 14 µg/L MAX
Xylenes (total) 1.1 LJv 1500 Jv µg/L 3/18 1500 µg/L MAXKey
µg/L: microgram per literMAX: Maximum ConcentrationLJv: Reported concentration is below the contract-required quantitation limit (CRQL) and should be considered estimated and biased lowJv: Reported concentration should be considered estimated and biased lowLJ: Reported concentration was below the CRQL and should be considered estimated=: Analytical result is valid with no QC qualifier
This table presents the chemicals of concern (COCs) and exposure point concentration for each of the COCs detected in ground water (i.e., the concentration that will be used to estimate the exposure and risk from each COC in ground water). The table includes the range of concentrations detected for each COC, as well as the frequency of detection (i.e., the number of times the chemical was detected in the samples collected at the site), the exposure point concentration (EPC), and how the EPC was derived. The table indicates that chlorinated solvents (PCE, TCE, cis-1,2-DCE, trans-1,2-DCE, and vinyl chloride) were the most frequently detected COCs in ground water at the site. The maximum concentration detected was used as the default exposure point concentration for all ground water COCs.
1. No cleanup levels have been established for benzene or xylenes at the Grants Chlorinated Solvents Plume Site since these compounds are being addressed by the New Mexico Environment Department - Petroleum Storage Tank Bureau
Exposure Point Concentration Units
Statistical Measure
Concentration DetectedExposure Point Chemical of Concern1 Frequency of Detection
Exposure Point Concentration
Table 3Summary of Chemicals of Concern and
Medium-Specific Exposure Point Concentrations (Indoor Air)
Scenario Timeframe: Current/FutureMedium: Ground WaterExposure Medium: Air (Vapor Intrusion)
UnitsMin Max
Residence A Tetrachloroethene 0.13 = 0.46 = µg/m3 2/2 0.460 µg/m3 MAX
Trichloroethene 0.042 = 0.069 = µg/m3 2/2 0.069 µg/m3 MAX
Benzene 0.92 J 0.97 J µg/m3 2/2 0.970 µg/m3 MAXResidence B Tetrachloroethene 0.33 = 0.33 = µg/m3 1/1 0.330 µg/m3 MAX
Trichloroethene 0.12 = 0.12 = µg/m3 1/1 0.120 µg/m3 MAX
Benzene 1.9 J 1.9 J µg/m3 1/1 1.900 µg/m3 MAX
Residence C Tetrachloroethene 0.057 = 0.48 = µg/m3 2/2 0.480 µg/m3 MAX
Trichloroethene 0.015 = 0.039 = µg/m3 2/2 0.039 µg/m3 MAX
Benzene 1.4 J 1.5 J µg/m3 2/2 1.500 µg/m3 MAX
Residence D Tetrachloroethene 0.099 = 1.1 = µg/m3 2/2 1.100 µg/m3 MAX
Trichloroethene 0.07 = 1.5 = µg/m3 2/2 1.500 µg/m3 MAX
Benzene 1.4 J 2.0 J µg/m3 2/2 2.000 µg/m3 MAX
Residence E Tetrachloroethene 0.25 = 0.25 = µg/m3 1/1 0.250 µg/m3 MAX
Trichloroethene 0.29 = 0.29 = µg/m3 1/1 0.290 µg/m3 MAX
Benzene 1.5 J 1.5 J µg/m3 1/1 1.500 µg/m3 MAX
Residence F Tetrachloroethene 1.4 = 1.4 = µg/m3 1/1 1.400 µg/m3 MAX
Trichloroethene 0.17 = 0.17 = µg/m3 1/1 0.170 µg/m3 MAX
Benzene 6.3 = 6.3 = µg/m3 1/1 6.300 µg/m3 MAX
Residence G Tetrachloroethene 4.3 = 4.3 = µg/m3 1/1 4.300 µg/m3 MAX
Trichloroethene 2.4 = 2.4 = µg/m3 1/1 2.400 µg/m3 MAX
Benzene 4.1 = 4.1 = µg/m3 1/1 4.100 µg/m3 MAX
Residence H Tetrachloroethene 1.5 = 1.5 = µg/m3 1/1 1.500 µg/m3 MAX
Trichloroethene 1.5 = 1.5 = µg/m3 1/1 1.500 µg/m3 MAX
Benzene 2.1 J 2.1 J µg/m3 1/1 2.100 µg/m3 MAX
Residence I Tetrachloroethene 7.2 = 8.1 = µg/m3 2/2 8.100 µg/m3 MAX
Trichloroethene 0.2 = 0.24 = µg/m3 2/2 0.240 µg/m3 MAX
Benzene 1.7 J 1.8 J µg/m3 2/2 1.800 µg/m3 MAX
Residence J Tetrachloroethene 0.49 = 0.88 = µg/m3 2/2 0.880 µg/m3 MAX
Trichloroethene 0.12 = 0.37 = µg/m3 2/2 0.370 µg/m3 MAX
Benzene 4.3 = 5 = µg/m3 2/2 5.000 µg/m3 MAX
Residence K Tetrachloroethene 21.9 = 21.9 = µg/m3 1/1 21.900 µg/m3 MAX
Trichloroethene 0.066 J 0.066 J µg/m3 1/1 0.066 µg/m3 MAX
Benzene 1.2 J 1.2 J µg/m3 1/1 1.200 µg/m3 MAX
Residence L Tetrachloroethene 131 = 161 = µg/m3 2/2 161.000 µg/m3 MAX
Trichloroethene 90.4 = 92.1 = µg/m3 2/2 92.100 µg/m3 MAX
Benzene 1.9 J 2.2 J µg/m3 2/2 2.200 µg/m3 MAX
Residence M Tetrachloroethene 16.7 = 16.7 = µg/m3 1/1 16.700 µg/m3 MAX
Trichloroethene 23.2 = 23.2 = µg/m3 1/1 23.200 µg/m3 MAX
Benzene 1.7 J 1.7 J µg/m3 1/1 1.700 µg/m3 MAX
Day Care Tetrachloroethene 0.094 = 0.13 = µg/m3 2/2 0.130 µg/m3 MAX
(6/15/04) Trichloroethene 0.029 = 0.055 = µg/m3 2/2 0.055 µg/m3 MAX
Benzene 0.85 J 1.2 J µg/m3 2/2 1.200 µg/m3 MAXKey
µg/m3: microgram per cubic meterMAX: Maximum Concentration=: Analytical result is valid with no QC qualifierJ: Estimated concentration below the reporting limit but above the detection limit
This table presents the chemicals of concern (COCs) and exposure point concentration for each of the COCs detected in indoor air (i.e., the concentration that will be used to estimate the exposure and risk from each COC in indoor air). The table includes the range of concentrations detected for each COC, as well as the frequency of detection (i.e., the number of times the chemical was detected in the samples collected at the site), the exposure point concentration (EPC), and how the EPC was derived. The table indicates that PCE, TCE, andbenzene were detected in all indoor air samples at the site. The maximum concentration detected was used as the default exposure point concentration for all indoor air COCs.
Exposure Point Concentration Units
Statistical Measure
Concentration DetectedExposure Point Chemical of Concern Frequency of Detection
Exposure Point Concentration
Table 4Selection of Exposure Pathways
Scenario Medium Exposure Exposure Receptor Receptor Exposure Type of Rationale for Selection or ExclusionTimeframe Medium Point Population Age Route Analysis of Exposure Pathway
Current Ground Water Tap Water Resident Adult Ingestion None
Inhalation None
Dermal None
Child Ingestion None
Inhalation None
Dermal None
Indoor Worker Adult Ingestion None
Inhalation None
Dermal None
Future Ground Water Tap Water Resident Adult Ingestion Quantitative
Inhalation Quantitative
Dermal Quantitative
Child Ingestion Quantitative
Inhalation Quantitative
Dermal Quantitative
Indoor Worker Adult Ingestion Qualitative
Inhalation None
Dermal None
Current/Future Indoor Air Resident Adult Inhalation Quantitative
Child Inhalation Quantitative
Indoor Worker Adult Inhalation Quantitative
Shallow aquifer is present at 5 feet bgs, so indoor air measurements were collected. Shallow aquifer is present at 5 feet bgs, so indoor air measurements were collected.
All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.
Ground Water - Shallow Aquifer
All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.All area businesses are currently on city water, and any affected city well would be out of service until remediated. As the resident is the receptor with the greater degree of exposure, the resident The indoor worker is not expected to engage in activities utilizing ground water that would result in large concentrations of volatiles in indoor air (showering, etc.).The indoor worker is not expected to engage in activity that would result in substantial dermal contact (showering, etc.).
Air (via vapor intrusion)
Shallow aquifer is present at 5 feet bgs, so indoor air measurements were collected.
All area businesses are currently on city water, and any affected city well would be out of service until remediated. All area businesses are currently on city water, and any affected city well would be out of service until remediated.
All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.
All area homes are currently on city water, and any affected city well would be out of service until remediated.
Ground Water - Shallow Aquifer
Ground Water - Shallow Aquifer
All area homes are currently on city water, and any affected city well would be out of service until remediated. Analysis will address only those COPCs without MCLs.
All area homes are currently on city water, and any affected city well would be out of service until remediated. All area homes are currently on city water, and any affected city well would be out of service until remediated. All area homes are currently on city water, and any affected city well would be out of service until remediated. All area homes are currently on city water, and any affected city well would be out of service until remediated. All area homes are currently on city water, and any affected city well would be out of service until remediated.All area businesses are currently on city water, and any affected city well would be out of service until remediated.
Table 5Values Used for Daily Intake Calculations (Ground Water)
Scenario Timeframe: FutureMedium: Ground WaterExposure Medium: Ground Water
Exposure Route Receptor
PopulationReceptor
Age Exposure Point Parameter Code Parameter Definition Value Units Rationale/Reference Intake Equation/Model NameIngestion Resident Adult Tap Water IRw Ingestion Rate of Water 2 L/day US EPA, 1997
MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 350 days/year US EPA, 1991ED Exposure Duration 30 years US EPA, 1988 Intake = IRw x MF x EF x EDBW Body Weight 70 kg US EPA, 1988 BW x ATc (or ATnc)ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 10950 days US EPA, 1988
Child Tap Water Irw Ingestion Rate of Water 1.1 L/day US EPA, 2002MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 350 days/year US EPA, 1991ED Exposure Duration 6 years US EPA, 1991BW Body Weight 15 kg US EPA, 1991ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 2190 days US EPA, 1988
Table 6Values Used for Daily Intake Calculations (Indoor Air)
Scenario Timeframe: Current/FutureMedium: Ground WaterExposure Medium: Indoor Air (via Vapor Intrusion)
Exposure Route Receptor
PopulationReceptor
Age Exposure Point Parameter Code Parameter Definition Value Units Rationale/Reference Intake Equation/Model NameInhalation Resident Adult Indoor Air InhR Inhalation Rate 20 m3/day US EPA, 1991
InhRadj Age-adjusted Inhalation Rate 11 m3-yr/kg-d US EPA, 2004MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 350 days/year US EPA, 1991ED Exposure Duration 30 years US EPA, 1988BW Body Weight 70 kg US EPA, 1988ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 10950 days US EPA, 1988
Child Indoor Air InhR Inhalation Rate 10 m3/day US EPA, 2002MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 350 days/year US EPA, 1991 Intake =ED Exposure Duration 6 years US EPA, 1991 InhR x MF x EF x EDBW Body Weight 15 kg US EPA, 1991 BW x ATc (or ATnc)ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 2190 days US EPA, 1988
Day Care Worker Adult Indoor Air InhR Inhalation Rate 13 m3/day US EPA, 1997MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 250 days/year US EPA, 1991ED Exposure Duration 25 years US EPA, 1991BW Body Weight 70 kg US EPA, 1988ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 9125 days US EPA, 1988
Dare Care Child Child Indoor Air InhR Inhalation Rate (0.68 X 8) 5.5 m3/day US EPA, 2004MF Modifiying Factor 0.001 mg/µg US EPA, 1988EF Exposure Frequency 250 days/year US EPA, 1991ED Exposure Duration 6 years US EPA, 1991BW Body Weight 15 kg US EPA, 1991ATc Averaging Time - carcinogen 25550 days US EPA, 1988ATnc Averaging Time - non-carcinogen 2190 days US EPA, 1988
Table 7Non Cancer Toxicity Data Summary
Pathway Inhalation
Chemical of Concern
Tetrachloroethene (PCE)
Tnchloroethene (TCE)
Benzene
Chronic/Subchromc
chronic
chronic
chronic
InhalationRfC
4 OOE 01
4 OOE 02
3 OOE-02
InhalationRfC Units
mg/m3
mg/m3
mg/m3
InhalationRfD
1 10E 01
1 10E 02
8 60E 03
Inhalation RfDUnits
mg/kg-day
mg/kg-day
mg/kg-day
Primary TargetOrgan
CNS liver
CNS liver
immune system
CombinedUncertainty/Modifying
Factors
1000
1000
300
Sources of RfDTarget Organ
R6 MSSLs/NCEA
R6 MSSLs/NCEA
IRIS
Dates of RfD TargetOrgan (MM/DD/YYYY)
12/21/2004
12/21/2004
12/21/2004Key
mg/m3 milligram per cubic meterR6 MSSLs/NCEA The Region 6 Medium Specific Screening Levels (R6 MSSLs) utilize some toxicity data from the National Center for Environmental Assessment (NCEA)IRIS Integrated Risk Information System U S EPACNS Central nervous system
This table provides non carcinogenic nsk information which is relevant to the contaminants of concern in indoor air PCE TCE and benzene have toxicity data indicating their potential for adversenon carcinogenic health effects in humans
Table 8Cancer Toxicity Data Summary
Pathway: Inhalation
Chemical of Concern Unit Risk Units
Inhalation Cancer
Slope Factor Units
Weight of Evidence/Cancer
Guideline Description Source Date (MM/DD/YYYY)
Tetrachloroethene 5.90E-03 (mg/m3)-1 2.00E-02 (mg/kg-day)-1 N/A Cal-EPA 12/21/2004
Trichloroethene (low) 2.00E-03 (mg/m3)-1 7.00E-03 (mg/kg-day)-1 N/A Cal-EPA 12/21/2004
Trichloroethene (high) 1.10E-04 (mg/m3)-1 4.00E-01 (mg/kg-day)-1 N/A NCEA 12/21/2004
Benzene (low) 2.20E-03 (mg/m3)-1 7.70E-03 (mg/kg-day)-1 A IRIS 12/21/2004
Benzene (high) 7.80E-03 (mg/m3)-1 2.70E-02 (mg/kg-day)-1 A IRIS 12/21/2004Key
mg/m3: milligram per cubic meter A - Human carcinogenmg/kg: milligram per kilogramCal-EPA: California Environmental Protection AgencyNCEA: National Center for Environmental AssessmentIRIS: Integrated Risk Information System, U.S. EPAN/A: not applicable - this chemical is not currently classified as to weight-of-evidence
This table provides carcinogenic risk information which is relevant to the contaminants of concern in indoor air. Benzene is considered carcinogenic via the inhalation route.
Table 9Risk Characterization Summary
Non-Carcinogens
FutureResidentAdult
Ingestion Inhalation Dermal
Exposure Routes Total
Indoor Air Indoor Air Residence 15 Benzene Immune system N/A 3.0E-02 N/A 3.0E-02Tetrachloroethene CNS, liver N/A 7.5E-04 N/A 7.5E-04Trichloroethene CNS, liver N/A 1.4E-03 N/A 1.4E-03
Residence 11 Benzene Immune system N/A 6.0E-02 N/A 6.0E-02Tetrachloroethene CNS, liver N/A 8.2E-04 N/A 8.2E-04Trichloroethene CNS, liver N/A 3.0E-03 N/A 3.0E-03
Residence 16 Benzene Immune system N/A 4.8E-02 N/A 4.8E-02Tetrachloroethene CNS, liver N/A 6.7E-04 N/A 6.7E-04Trichloroethene CNS, liver N/A 6.7E-04 N/A 6.7E-04
Residence 13 Benzene Immune system N/A 6.4E-02 N/A 6.4E-02Tetrachloroethene CNS, liver N/A 1.5E-03 N/A 1.5E-03Trichloroethene CNS, liver N/A 2.0E-02 N/A 2.0E-02
Residence 14 Benzene Immune system N/A 4.8E-02 N/A 4.8E-02Tetrachloroethene CNS, liver N/A 6.2E-04 N/A 6.2E-04Trichloroethene CNS, liver N/A 7.2E-03 N/A 7.2E-03
Residence 6 Benzene Immune system N/A 2.0E-02 N/A 2.0E-02Tetrachloroethene CNS, liver N/A 3.5E-03 N/A 3.5E-03Trichloroethene CNS, liver N/A 4.3E-03 N/A 4.3E-03
Residence 7 Benzene Immune system N/A 1.3E-01 N/A 1.3E-01Tetrachloroethene CNS, liver N/A 1.1E-02 N/A 1.1E-02Trichloroethene CNS, liver N/A 6.0E-02 N/A 6.0E-02
Residence 4 Benzene Immune system N/A 6.7E-02 N/A 6.7E-02Tetrachloroethene CNS, liver N/A 3.7E-03 N/A 3.7E-03Trichloroethene CNS, liver N/A 3.7E-02 N/A 3.7E-02
Residence 1 Benzene Immune system N/A 5.7E-02 N/A 5.7E-02Tetrachloroethene CNS, liver N/A 1.9E-02 N/A 1.9E-02Trichloroethene CNS, liver N/A 5.5E-03 N/A 5.5E-03
Residence 9 Benzene Immune system N/A 1.5E-01 N/A 1.5E-01Tetrachloroethene CNS, liver N/A 1.7E-03 N/A 1.7E-03Trichloroethene CNS, liver N/A 6.2E-03 N/A 6.2E-03
Residence 12 Benzene Immune system N/A 3.8E-02 N/A 3.8E-02Tetrachloroethene CNS, liver N/A 5.5E-02 N/A 5.5E-02Trichloroethene CNS, liver N/A 1.6E-03 N/A 1.6E-03
Residence 3 Benzene Immune system N/A 6.7E-02 N/A 6.7E-02Tetrachloroethene CNS, liver N/A 3.7E-01 N/A 3.7E-01Trichloroethene CNS, liver N/A 2.3E+00 N/A 2.3E+00
Residence 2 Benzene Immune system N/A 5.5E-02 N/A 5.5E-02Tetrachloroethene CNS, liver N/A 4.3E-02 N/A 4.3E-02Trichloroethene CNS, liver N/A 5.7E-01 N/A 5.7E-01
FutureResidentChild
Ingestion Inhalation Dermal
Exposure Routes Total
Indoor Air Indoor Air Residence 15 Benzene Immune system N/A 7.1E-02 N/A 7.1E-02Tetrachloroethene CNS, liver N/A 1.7E-03 N/A 1.7E-03Trichloroethene CNS, liver N/A 3.3E-03 N/A 3.3E-03
Residence 11 Benzene Immune system N/A 1.4E-01 N/A 1.4E-01Tetrachloroethene CNS, liver N/A 1.9E-03 N/A 1.9E-03Trichloroethene CNS, liver N/A 7.0E-03 N/A 7.0E-03
Residence 16 Benzene Immune system N/A 1.1E-01 N/A 1.1E-01Tetrachloroethene CNS, liver N/A 1.5E-03 N/A 1.5E-03Trichloroethene CNS, liver N/A 1.5E-03 N/A 1.5E-03
Residence 13 Benzene Immune system N/A 1.5E-01 N/A 1.5E-01Tetrachloroethene CNS, liver N/A 3.5E-03 N/A 3.5E-03Trichloroethene CNS, liver N/A 4.6E-02 N/A 4.6E-02
7.6E-02
1.5E-01
1.1E-01
2.0E-01
6.7E-01
Non-Carcinogenic Total Hazard
Index
Non-Carcinogenic Total Hazard
Index
8.2E-02
1.6E-01
9.5E-02
2.7E+00
2.8E-02
2.0E-01
5.6E-02
1.1E-01
3.2E-02
6.4E-02
4.9E-02
8.6E-02
Non-Carcinogenic Hazard QuotientExposure Medium
Exposure Point
Primary Target Organ
Scenario Timeframe:Receptor Population:Receptor Age:
Scenario Timeframe:
Medium Exposure Medium
Non-Carcinogenic Hazard QuotientPrimary Target Organ
Receptor Population:Receptor Age:
Chemical of Concern
Chemical of Concern
Exposure Point
Medium
Table 9Risk Characterization Summary
Non-Carcinogens
Residence 14 Benzene Immune system N/A 1.1E-01 N/A 1.1E-01Tetrachloroethene CNS, liver N/A 1.5E-03 N/A 1.5E-03Trichloroethene CNS, liver N/A 1.7E-02 N/A 1.7E-02
Residence 6 Benzene Immune system N/A 4.7E-01 N/A 4.7E-01Tetrachloroethene CNS, liver N/A 8.1E-03 N/A 8.1E-03Trichloroethene CNS, liver N/A 1.0E-02 N/A 1.0E-02
Residence 7 Benzene Immune system N/A 3.0E-01 N/A 3.0E-01Tetrachloroethene CNS, liver N/A 2.5E-02 N/A 2.5E-02Trichloroethene CNS, liver N/A 1.4E-01 N/A 1.4E-01
Residence 4 Benzene Immune system N/A 1.5E-01 N/A 1.5E-01Tetrachloroethene CNS, liver N/A 8.7E-03 N/A 8.7E-03Trichloroethene CNS, liver N/A 8.7E-02 N/A 8.7E-02
Residence 1 Benzene Immune system N/A 1.4E-01 N/A 1.4E-01Tetrachloroethene CNS, liver N/A 4.5E-02 N/A 4.5E-02Trichloroethene CNS, liver N/A 1.3E-02 N/A 1.3E-02
Residence 9 Benzene Immune system N/A 3.5E-01 N/A 3.5E-01Tetrachloroethene CNS, liver N/A 4.0E-03 N/A 4.0E-03Trichloroethene CNS, liver N/A 1.5E-02 N/A 1.5E-02
Residence 12 Benzene Immune system N/A 9.0E-02 N/A 9.0E-02Tetrachloroethene CNS, liver N/A 1.3E-01 N/A 1.3E-01Trichloroethene CNS, liver N/A 3.8E-03 N/A 3.8E-03
Residence 3 Benzene Immune system N/A 1.5E-01 N/A 1.5E-01Tetrachloroethene CNS, liver N/A 8.7E-01 N/A 8.7E-01Trichloroethene CNS, liver N/A 5.3E+00 N/A 5.3E+00
Residence 2 Benzene Immune system N/A 1.3E-01 N/A 1.3E-01Tetrachloroethene CNS, liver N/A 1.0E-01 N/A 1.0E-01Trichloroethene CNS, liver N/A 1.4E+00 N/A 1.4E+00
CurrentDay Care WorkerAdult
Ingestion Inhalation Dermal
Exposure Routes Total
Indoor Air Indoor Air Day Care Benzene Immune system N/A 1.7E-02 N/A 1.7E-02(Structure 5) Tetrachloroethene CNS, liver N/A -- N/A --
Trichloroethene CNS, liver N/A 6.8E-02 N/A 6.8E-02CurrentDay Care ChildChild
Ingestion Inhalation Dermal
Exposure Routes Total
Indoor Air Indoor Air Day Care Benzene Immune system N/A 5.5E-02 N/A 5.5E-02(Structure 5) Tetrachloroethene CNS, liver N/A -- N/A --
Trichloroethene CNS, liver N/A 5.7E-01 N/A 5.7E-01Key
µg/L: micrograms per literN/A: Route of exposure is not applicable to this medium.CNS: Central nervous system
Risk Characterization Summary - Non-Carcinogens
6.3E-01
1.6E+00
8.5E-02
Non-Carcinogenic Total Hazard
Index
Non-Carcinogenic Total Hazard
Index
2.0E-01
3.7E-01
2.2E-01
6.3E+00
1.3E-01
4.9E-01
4.7E-01
2.5E-01
Non-Carcinogenic Hazard Quotient
Exposure Medium
Exposure Point
Chemical of Concern
Exposure Medium
Exposure Point
Chemical of Concern
Primary Target Organ
Table 9 provides hazard quotients (HQs) for each route of exposure and the hazard index (sum of hazard quotients) for all routes of exposure. The Risk Assessment Guidance (RAGS) for Superfund states that, generally, a hazard index (HI) greater than 1 indicates the potential for adverse noncancer effects. The estimated residential indoor air H Is of 2.7 (adult) and 6.3 (child) indicate that the potential for adverse noncancer effects could occur within Structure 3 from exposure to contaminated residential indoor air containing benzene, tetrachloroethene, and trichloroethene. The estimated HI within Residence 2 (1.6 for a child) also indicates the potential for adverse noncancer effects for children. The estimated indoor air HIs for the day care (both workers and children) are less than 1, and do not indicate a potential for adverse noncancer effects. The HQs shown are from the Baseline Human Health Risk Assessment which did not include samples collected from Residences 8, and 10 described in the RI/FS reports.
Scenario Timeframe:Receptor Population:Receptor Age:
Scenario Timeframe:Receptor Population:Receptor Age:
Non-Carcinogenic Hazard Quotient
Medium
Primary Target Organ
--: Tetrachloroethene was detected below the risk-based screening level in day care indoor air, and an HQ was not calculated inthe Baseline Human Health Risk Assessment.
Medium
Table 10Risk Characterization Summary
Carcinogens
FutureResidentAdult
Ingestion Inhalation DermalExposure
Routes TotalIndoor Air Indoor Air Residence 15 Benzene (low) * N/A 8.5E-07 N/A Low*
Benzene (high) * N/A 3.0E-06 N/A 1.6E-06Tetrachloroethene N/A 7.0E-07 N/ATrichloroethene (low) * N/A 4.6E-08 N/A High*Trichloroethene (high) * N/A 2.6E-06 N/A 6.3E-06
Residence 11 Benzene (low) * N/A 1.7E-06 N/A Low*Benzene (high) * N/A 5.9E-06 N/A 2.6E-06Tetrachloroethene N/A 7.8E-07 N/ATrichloroethene (low) * N/A 9.8E-08 N/A High*Trichloroethene (high) * N/A 5.6E-06 N/A 1.2E-05
Residence 16 Benzene (low) * N/A 1.4E-06 N/A Low*Benzene (high) * N/A 4.9E-06 N/A 2.0E-06Tetrachloroethene N/A 6.4E-07 N/ATrichloroethene (low) * N/A 2.2E-08 N/A High*Trichloroethene (high) * N/A 1.3E-06 N/A 6.8E-06
Residence 13 Benzene (low) * N/A 1.8E-06 N/A Low*Benzene (high) * N/A 6.2E-06 N/A 3.8E-06Tetrachloroethene N/A 1.4E-06 N/ATrichloroethene (low) * N/A 6.5E-07 N/A High*Trichloroethene (high) * N/A 3.7E-05 N/A 4.5E-05
Residence 14 Benzene (low) * N/A 1.4E-06 N/A Low*Benzene (high) * N/A 4.9E-06 N/A 2.2E-06Tetrachloroethene N/A 5.9E-07 N/ATrichloroethene (low) * N/A 2.4E-07 N/A High*Trichloroethene (high) * N/A 1.4E-05 N/A 1.9E-05
Residence 6 Benzene (low) * N/A 5.7E-06 N/A Low*Benzene (high) * N/A 2.0E-05 N/A 9.0E-06Tetrachloroethene N/A 3.2E-06 N/ATrichloroethene (low) * N/A 1.4E-07 N/A High*Trichloroethene (high) * N/A 8.0E-06 N/A 3.1E-05
Residence 7 Benzene (low) * N/A 3.7E-06 N/A Low*Benzene (high) * N/A 1.3E-05 N/A 1.6E-05Tetrachloroethene N/A 1.0E-05 N/ATrichloroethene (low) * N/A 2.0E-06 N/A High*Trichloroethene (high) * N/A 1.1E-04 N/A 1.3E-04
Residence 4 Benzene (low) * N/A 1.9E-06 N/A Low*Benzene (high) * N/A 6.8E-06 N/A 6.8E-06Tetrachloroethene N/A 3.6E-06 N/ATrichloroethene (low) * N/A 1.3E-06 N/A High*Trichloroethene (high) * N/A 7.2E-05 N/A 8.2E-05
Residence 1 Benzene (low) * N/A 1.6E-06 N/A Low*Benzene (high) * N/A 5.7E-06 N/A 2.0E-05Tetrachloroethene N/A 1.8E-05 N/ATrichloroethene (low) * N/A 1.8E-07 N/A High*Trichloroethene (high) * N/A 1.0E-05 N/A 3.4E-05
Residence 9 Benzene (low) * N/A 4.2E-06 N/A Low*Benzene (high) * N/A 1.5E-05 N/A 6.1E-06Tetrachloroethene N/A 1.6E-06 N/ATrichloroethene (low) * N/A 2.0E-07 N/A High*Trichloroethene (high) * N/A 1.2E-05 N/A 2.8E-05
Residence 12 Benzene (low) * N/A 1.1E-06 N/A Low*Benzene (high) * N/A 3.8E-06 N/A 5.3E-05Tetrachloroethene N/A 5.2E-05 N/ATrichloroethene (low) * N/A 5.4E-08 N/A High*Trichloroethene (high) * N/A 3.1E-06 N/A 5.9E-05
Residence 3 Benzene (low) * N/A 1.9E-06 N/A Low*Benzene (high) * N/A 6.8E-06 N/A 4.4E-04Tetrachloroethene N/A 3.6E-04 N/ATrichloroethene (low) * N/A 7.7E-05 N/A High*Trichloroethene (high) * N/A 4.4E-03 N/A 4.8E-03
Residence 2 Benzene (low) * N/A 1.5E-06 N/A Low*Benzene (high) * N/A 5.4E-06 N/A 6.0E-05Tetrachloroethene N/A 4.0E-05 N/ATrichloroethene (low) * N/A 1.9E-05 N/A High*Trichloroethene (high) * N/A 1.1E-03 N/A 1.1E-03
Exposure Point
Carcinogenic Risk *Chemical of Concern
Scenario Timeframe:Receptor Population:Receptor Age:
Medium Exposure Medium
Table 10Risk Characterization Summary
Carcinogens
FutureResidentChild
Ingestion Inhalation DermalExposure
Routes TotalIndoor Air Indoor Air Residence 15 Benzene (low) * N/A 4.0E-07 N/A Low*
Benzene (high) * N/A 1.4E-06 N/A 7.4E-07Tetrachloroethene N/A 3.2E-07 N/ATrichloroethene (low) * N/A 2.2E-08 N/A High*Trichloroethene (high) * N/A 1.2E-06 N/A 3.0E-06
Residence 11 Benzene (low) * N/A 7.7E-07 N/A Low*Benzene (high) * N/A 2.7E-06 N/A 1.2E-06Tetrachloroethene N/A 3.6E-07 N/ATrichloroethene (low) * N/A 4.6E-08 N/A High*Trichloroethene (high) * N/A 2.6E-06 N/A 5.7E-06
Residence 16 Benzene (low) * N/A 6.3E-07 N/A Low*Benzene (high) * N/A 2.2E-06 N/A 9.4E-07Tetrachloroethene N/A 3.0E-07 N/ATrichloroethene (low) * N/A 1.1E-08 N/A High*Trichloroethene (high) * N/A 6.0E-07 N/A 3.1E-06
Residence 13 Benzene (low) * N/A 8.5E-07 N/A Low*Benzene (high) * N/A 3.0E-06 N/A 1.8E-06Tetrachloroethene N/A 6.6E-07 N/ATrichloroethene (low) * N/A 3.0E-07 N/A High*Trichloroethene (high) * N/A 1.7E-05 N/A 2.1E-05
Residence 14 Benzene (low) * N/A 6.3E-07 N/A Low*Benzene (high) * N/A 2.2E-06 N/A 1.0E-06Tetrachloroethene N/A 2.8E-07 N/ATrichloroethene (low) * N/A 1.1E-07 N/A High*Trichloroethene (high) * N/A 6.4E-06 N/A 8.9E-06
Residence 6 Benzene (low) * N/A 2.7E-06 N/A Low*Benzene (high) * N/A 9.5E-06 N/A 4.3E-06Tetrachloroethene N/A 1.5E-06 N/ATrichloroethene (low) * N/A 6.5E-08 N/A High*Trichloroethene (high) * N/A 3.7E-06 N/A 1.5E-05
Residence 7 Benzene (low) * N/A 1.7E-06 N/A Low*Benzene (high) * N/A 5.9E-06 N/A 7.4E-06Tetrachloroethene N/A 4.8E-06 N/ATrichloroethene (low) * N/A 9.1E-07 N/A High*Trichloroethene (high) * N/A 5.2E-05 N/A 6.3E-05
Residence 4 Benzene (low) * N/A 9.2E-07 N/A Low*Benzene (high) * N/A 3.2E-06 N/A 3.1E-06Tetrachloroethene N/A 1.6E-06 N/ATrichloroethene (low) * N/A 5.7E-07 N/A High*Trichloroethene (high) * N/A 3.3E-05 N/A 3.8E-05
Residence 1 Benzene (low) * N/A 7.6E-07 N/A Low*Benzene (high) * N/A 2.7E-06 N/A 9.2E-06Tetrachloroethene N/A 8.4E-06 N/ATrichloroethene (low) * N/A 8.4E-08 N/A High*Trichloroethene (high) * N/A 4.8E-06 N/A 1.6E-05
Residence 9 Benzene (low) * N/A 2.0E-06 N/A Low*Benzene (high) * N/A 7.0E-06 N/A 2.9E-06Tetrachloroethene N/A 7.6E-07 N/ATrichloroethene (low) * N/A 9.8E-08 N/A High*Trichloroethene (high) * N/A 5.6E-06 N/A 1.3E-05
Residence 12 Benzene (low) * N/A 5.1E-07 N/A Low*Benzene (high) * N/A 1.8E-06 N/A 2.5E-05Tetrachloroethene N/A 2.4E-05 N/ATrichloroethene (low) * N/A 2.5E-08 N/A High*Trichloroethene (high) * N/A 1.4E-06 N/A 2.7E-05
Residence 3 Benzene (low) * N/A 9.2E-07 N/A Low*Benzene (high) * N/A 3.2E-06 N/A 2.0E-04Tetrachloroethene N/A 1.6E-04 N/ATrichloroethene (low) * N/A 3.5E-05 N/A High*Trichloroethene (high) * N/A 2.0E-03 N/A 2.2E-03
Residence 2 Benzene (low) * N/A 7.2E-07 N/A Low*Benzene (high) * N/A 2.5E-06 N/A 2.8E-05Tetrachloroethene N/A 1.9E-05 N/ATrichloroethene (low) * N/A 9.1E-06 N/A High*Trichloroethene (high) * N/A 5.2E-04 N/A 5.4E-04
Receptor Population:Receptor Age:
Exposure Medium
Exposure Point
Chemical of Concern
Scenario Timeframe:
Carcinogenic Risk *Medium
Table 10Risk Characterization Summary
Carcinogens
CurrentDay Care WorkerAdult
Ingestion Inhalation DermalExposure
Routes TotalIndoor Air Indoor Air Day Care Benzene (low) * N/A 4.2E-07 N/A Low*
(Structure 5) Benzene (high) * N/A 1.5E-06 N/A 4.4E-07Tetrachloroethene N/A -- N/ATrichloroethene (low) * N/A 1.8E-08 N/A High*Trichloroethene (high) * N/A 1.0E-06 N/A 2.5E-06
CurrentDay Care ChildChild
Ingestion Inhalation DermalExposure
Routes TotalIndoor Air Indoor Air Day Care Benzene (low) * N/A 2.0E-07 N/A Low*
(Structure 5) Benzene (high) * N/A 7.0E-07 N/A 2.1E-07Tetrachloroethene N/A -- N/ATrichloroethene (low) * N/A 8.4E-09 N/A High*Trichloroethene (high) * N/A 4.8E-07 N/A 1.2E-06
Key
µg/L: micrograms per literN/A: Route of exposure is not applicable to this medium.
Risk Characterization Summary - Non-Carcinogens
--: Tetrachloroethene was detected below the risk-based screening level in day care indoor air, and a cancer risk was not calculated in the Baseline Human Health Risk Assessment.
*: For some chemicals, cancer risks were calculated using two slope factors. In the case of benzene and TCE, slope factor ranges were used, representing a high-end and low-end risk.
Receptor Population:Receptor Age:
Medium
Scenario Timeframe:Receptor Population:Receptor Age:
Carcinogenic Risk *
Table 10 provides risk estimates for the indoor air route of exposure. These risk estimates are based on a reasonable maximum exposure and were developed by taking into account various conservative assumptions about the frequency and duration of exposure to indoor air, as well as the toxicity of the COCs. The total risk from direct exposure to contaminated indoor air at each residence is provided as a low total and a high total, based on two different slope factors used for benzene and TCE. Estimated risk at individual residences is frequently equal to or greater than the 10 -5 range. A 10-5 risk level indicates that if no clean up action is taken, an individual would have an increased probability of 1 in 100,000 of developing cancer as a result of site-related exposure to the COCs.
Carcinogenic Risk *
Exposure Medium
Exposure Point
Chemical of Concern
Scenario Timeframe:
Medium Exposure Medium
Exposure Point
Chemical of Concern
1 2No Action Install Vapor Mitigation System
Activity-Specific ARARsAir40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
- - Vapor venting system only, no vapor treatment.
40 CFR 264.AA–Air Emission Standards for Process Vents - - Vapor venting system only, no vapor treatment.
20.2 NMAC - - Potentially applicable if vapor mitigation activities involve sufficient quantities of solvents to be subject to regulation.
Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
- - No water discharges associated with this alternative.
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
- - No water discharges associated with this alternative.
40 CFR Part 122 Subpart B - - No water discharges associated with this alternative.
40 CFR 122.41(l)–Monitoring Requirements - - No water discharges associated with this alternative.
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
- - No water discharges associated with this alternative.
Solid and Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste - - Vapor venting system only, no vapor treatment.
40 CFR 262-Hazardous Waste Generator Requirements - - Vapor venting system only, no vapor treatment.
40 CFR 264, 265 - - Vapor venting system only, no vapor treatment.
Location-Specific ARARs40 CFR Part 6-Floodplain or Wetland Environments - - NA at GCSP Site; site is not within floodplain or wetlands.
Endangered Species Act - - NA at GCSP Site; no endangered species present.
National Historical Preservation Act, 16 USC 661 et seq., 36 CFR Part 65 - - NA at GCSP Site; no historic structures identified.
Archaeological and Historic Preservation Act - - NA at GCSP Site; no archaeological or historic relics identified.
Chemical-Specific ARARs
20.6.2 NMAC – New Mexico Water Quality Control Regulations - - - -
40 CFR 268-Land Disposal Restrictions - - - -
40 CFR 50–National Primary and Secondary Ambient Air Quality Standards - - - -
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters - - - -
40 CFR 141, Subpart B –National Primary Drinking Water Regulations - - - -
NotesCFR - Code of Federal RegulationsNMAC - New Mexico Administrative CodeMCLs - Maximum Contaminant Levels
GCSP - Grants Chlorinated Solvents Plume
NPDES - National Pollutant Discharge Elimination System
ARARIndoor Air Alternatives
Table 11Summary of ARARs
Activity-Specific ARARsAir40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
40 CFR 264.AA–Air Emission Standards for Process Vents
20.2 NMAC
Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
40 CFR Part 122 Subpart B
40 CFR 122.41(l)–Monitoring Requirements
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
Solid and Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste
40 CFR 262-Hazardous Waste Generator Requirements
40 CFR 264, 265
Location-Specific ARARs40 CFR Part 6-Floodplain or Wetland Environments
Endangered Species Act
National Historical Preservation Act, 16 USC 661 et seq., 36 CFR Part 65
Archaeological and Historic Preservation Act
Chemical-Specific ARARs
20.6.2 NMAC – New Mexico Water Quality Control Regulations
40 CFR 268-Land Disposal Restrictions
40 CFR 50–National Primary and Secondary Ambient Air Quality Standards
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters
40 CFR 141, Subpart B –National Primary Drinking Water Regulations
NotesCFR - Code of Federal RegulationsNMAC - New Mexico Administrative CodeMCLs - Maximum Contaminant Levels
GCSP - Grants Chlorinated Solvents Plume
NPDES - National Pollutant Discharge Elimination System
ARAR 1 2 3 4No Action Thermal Treatment ISCO w/ Follow-on ERD ERD (Gridded)
- - Potentially applicable if remedial alternative includes regulated compounds or equipment.
NA at GCSP Site; no air emissions/treatment
NA at GCSP Site; no air emissions/treatment
- - Potentially applicable if RCRA hazardous waste is treatedin designated equipment.
NA at GCSP Site; no air emissions/treatment
NA at GCSP Site; no air emissions/treatment
- - Potentially applicable if remedial activities involve sources subject to regulation.
NA at GCSP Site; no air emissions/treatment
NA at GCSP Site; no air emissions/treatment
- -
Substantive requirements adopted by the state pursuant to Section 208 of the Clean Water Act would be applicable to direct discharge of treatment system effluenor other discharges to surface water.
NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
- -
Although remedial alternatives are unlikely to include a source category subject to NPDES effluent limitations, some limitations may be relevant and appropriate to discharges to surface water if the remedial alternative includes a technology substantially similar to that employed by a regulated source category.
NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
- -
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre ormore.
NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
- - Administrative requirement applicable only for discharges to offsite surface water (potentially the Rio San Jose).
NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
- -
Applicable to analyses performed under NPDES permit; relevant and appropriate to analyses of onsite direct discharge of treatment system effluent or other process waters.
NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
- -Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
- -Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
- -
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - NA at GCSP Site; site is not within floodplain or wetlands.NA at GCSP Site; site is not within floodplain or wetlands.
NA at GCSP Site; site is not within floodplain or wetlands.
- - NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species present.
NA at GCSP Site; no endangered species present.
- - NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures identified.
NA at GCSP Site; no historic structures identified.
- - NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
- -These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
The substantive provisions of these regulations must be met as part of a reinjection program. These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
- -Applicable to off-site land disposal of listed or characteristic hazardous wastes, and to on-site remedies that include placement of these wastes.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - Discharges of process air will meet the air qualtiy standards.
No discharges associated with this alternative.
No discharges associated with this alternative.
- - Water quality criteria may be relevant and appropriate to ground water or other discharges to surface water.
No discharges associated with this alternative.
No discharges associated with this alternative.
- -MCLs are applicable. MCLs are relevant and appropriatesince there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevantand appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevantand appropriate since there is no mechanism to prevent the ground water from being used for drinking.
Source Area Treatment Alternatives
Table 11Summary of ARARs
Activity-Specific ARARsAir40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
40 CFR 264.AA–Air Emission Standards for Process Vents
20.2 NMAC
Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
40 CFR Part 122 Subpart B
40 CFR 122.41(l)–Monitoring Requirements
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
Solid and Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste
40 CFR 262-Hazardous Waste Generator Requirements
40 CFR 264, 265
Location-Specific ARARs40 CFR Part 6-Floodplain or Wetland Environments
Endangered Species Act
National Historical Preservation Act, 16 USC 661 et seq., 36 CFR Part 65
Archaeological and Historic Preservation Act
Chemical-Specific ARARs
20.6.2 NMAC – New Mexico Water Quality Control Regulations
40 CFR 268-Land Disposal Restrictions
40 CFR 50–National Primary and Secondary Ambient Air Quality Standards
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters
40 CFR 141, Subpart B –National Primary Drinking Water Regulations
NotesCFR - Code of Federal RegulationsNMAC - New Mexico Administrative CodeMCLs - Maximum Contaminant Levels
GCSP - Grants Chlorinated Solvents Plume
NPDES - National Pollutant Discharge Elimination System
ARAR 1 2 3 4 5No Action ZVI PRB - Multiple Transects ISCO w/ Follow-on ERD ERD (Bio-Barrier) Pump and Treat
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA, no discharges associated with this alternative. NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
Substantive requirements adopted by the state pursuant to Section 208 of the Clean Water Act would be applicable to direct discharge of treatment system effluent or other discharges to surface water.
- - NA, no discharges associated with this alternative. NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
Although remedial alternatives are unlikely to include a source category subject to NPDES effluent limitations, some limitations may be relevant and appropriate to discharges to surface water if the remedial alternativeincludes a technology substantially similar to that employed by a regulated source category.
- - NA, no discharges associated with this alternative. NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
- - NA, no discharges associated with this alternative. NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
Administrative requirement applicable only for discharges to offsite surface water (potentially the Rio San Jose).
- - NA, no discharges associated with this alternative. NA, no discharges associated with this alternative.
NA, no discharges associated with this alternative.
Applicable to analyses performed under NPDES permit; relevant and appropriate to analyses of onsite direct discharge of treatment system effluent or other process waters.
- - This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements inParts 262-268.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system.
- - This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system.
- -
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation. Investigation-derived waste generated during investigationand construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system. Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - NA at GCSP Site; site is not within floodplain or wetlands. NA at GCSP Site; site is not within floodplain orwetlands.
NA at GCSP Site; site is not within floodplain orwetlands. NA at GCSP Site; site is not within floodplain or wetlands.
- - NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species present.
NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species present.
- - NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures identified.
NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures identified.
- - NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified. NA at GCSP Site; no archaeological or historic relics identified.
- -These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
The substantive provisions of these regulations must be met as part of areinjection program. These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
- -Applicable to off-site land disposal of listed or characteristic hazardous wastes, and to on-site remedies that include placement of these wastes.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this alternative. Discharges of process air will meet the air qualtiy standards.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this alternative. Water quality criteria may be relevant and appropriate to ground water or other discharges to surface water.
- -MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
Shallow Plume Core and Hot Spot
Table 11Summary of ARARs
Activity-Specific ARARsAir40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
40 CFR 264.AA–Air Emission Standards for Process Vents
20.2 NMAC
Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
40 CFR Part 122 Subpart B
40 CFR 122.41(l)–Monitoring Requirements
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
Solid and Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste
40 CFR 262-Hazardous Waste Generator Requirements
40 CFR 264, 265
Location-Specific ARARs40 CFR Part 6-Floodplain or Wetland Environments
Endangered Species Act
National Historical Preservation Act, 16 USC 661 et seq., 36 CFR Part 65
Archaeological and Historic Preservation Act
Chemical-Specific ARARs
20.6.2 NMAC – New Mexico Water Quality Control Regulations
40 CFR 268-Land Disposal Restrictions
40 CFR 50–National Primary and Secondary Ambient Air Quality Standards
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters
40 CFR 141, Subpart B –National Primary Drinking Water Regulations
NotesCFR - Code of Federal RegulationsNMAC - New Mexico Administrative CodeMCLs - Maximum Contaminant Levels
GCSP - Grants Chlorinated Solvents Plume
NPDES - National Pollutant Discharge Elimination System
ARAR 1 2 3 4 5No Action MNA ZVI PRB - Multiple Transects ERD (Bio-Barrier) Pump and Treat
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment Would apply to air stripper offgas.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Substantive requirements adopted by the state pursuant to Section 208 of the Clean Water Act would be applicable to direct discharge of treatment system effluent or other discharges to surface water.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Although remedial alternatives are unlikely to include a source category subject to NPDES effluent limitations, some limitations may be relevant and appropriate to discharges to surface water if the remedial alternative includes a technology substantially similar to that employed by a regulated source category.
- - NA, no discharges associated with this alternative.
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
NA, no discharges associated with this alternative.
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.Administrative requirement applicable only for discharges to offsite surface water (potentially the Rio San Jose).
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Applicable to analyses performed under NPDES permit; relevant and appropriate to analyses of onsite direct discharge of treatment system effluent or other process waters.
- -
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system.
- -
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system.
- -
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation. Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated duringinvestigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
This alternative may generate hazardous waste during system installation and operation of the ground water extraction and treatment system. Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - NA at GCSP Site; site is not within floodplain orwetlands. NA at GCSP Site; site is not within floodplain or wetlands. NA at GCSP Site; site is not within floodplain
or wetlands. NA at GCSP Site; site is not within floodplain or wetlands.
- - NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species
present. NA at GCSP Site; no endangered species present.
- - NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures
identified. NA at GCSP Site; no historic structures identified.
- - NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified. NA at GCSP Site; no archaeological or historic relics identified.
- -These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowablelimits are more stringent than EPA MCLs.
The substantive provisions of these regulations must be met as part of a reinjection program. These regulations must be compliedwith for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
- - NA for this alternative, no generation of hazardous waste will occur.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated duringinvestigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this alternative. Discharges of process air will meet the air qualtiy standards.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this alternative.
Water quality criteria may be relevant and appropriate to ground water or other discharges to surface water.
- -
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant andappropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
Shallow Plume Core Periphery
Table 11Summary of ARARs
Activity-Specific ARARsAir40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
40 CFR 264.AA–Air Emission Standards for Process Vents
20.2 NMAC
Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
40 CFR Part 122 Subpart B
40 CFR 122.41(l)–Monitoring Requirements
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
Solid and Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste
40 CFR 262-Hazardous Waste Generator Requirements
40 CFR 264, 265
Location-Specific ARARs40 CFR Part 6-Floodplain or Wetland Environments
Endangered Species Act
National Historical Preservation Act, 16 USC 661 et seq., 36 CFR Part 65
Archaeological and Historic Preservation Act
Chemical-Specific ARARs
20.6.2 NMAC – New Mexico Water Quality Control Regulations
40 CFR 268-Land Disposal Restrictions
40 CFR 50–National Primary and Secondary Ambient Air Quality Standards
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters
40 CFR 141, Subpart B –National Primary Drinking Water Regulations
NotesCFR - Code of Federal RegulationsNMAC - New Mexico Administrative CodeMCLs - Maximum Contaminant Levels
GCSP - Grants Chlorinated Solvents Plume
NPDES - National Pollutant Discharge Elimination System
ARAR 1 2 3 4 5No Action MNA ZVI PRB - with Deep ERD ERD (Bio-Barrier) Pump and Treat
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air
emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air
emissions/treatment Would apply to air stripper offgas.
- - NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air emissions/treatment NA at GCSP Site; no air
emissions/treatment Would apply to air stripper offgas.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Substantive requirements adopted by the state pursuant to Section 208 of the Clean Water Act would be applicable to direct discharge of treatment system effluent or other discharges to surface water.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Although remedial alternatives are unlikely to include a sourcecategory subject to NPDES effluent limitations, some limitations may be relevant and appropriate to discharges to surface water if the remedial alternative includes a technology substantially similar to that employed by a regulated source category.
- - NA, no discharges associated with this alternative.
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirementsincluding implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
NA, no discharges associated with this alternative.
Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.Administrative requirement applicable only for discharges to offsite surface water (potentially the Rio San Jose).
- - NA, no discharges associated with this alternative. NA, no direct discharges associated with this alternative. NA, no discharges associated with this
alternative.
Applicable to analyses performed under NPDES permit; relevant and appropriate to analyses of onsite direct dischargeof treatment system effluent or other process waters.
- -
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
This alternative may generate hazardous waste during systeminstallation and operation of the ground water extraction and treatment system.
- -
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation.
Substantive management standards are applicable to hazardous waste generated during remedial activities, including investigation.
This alternative may generate hazardous waste during systeminstallation and operation of the ground water extraction and treatment system.
- -
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
This alternative may generate hazardous waste during excavation and dewatering for the ZVI wall installation. Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
This alternative may generate hazardous waste during systeminstallation and operation of the ground water extraction and treatment system. Investigation-derived waste generated during investigation and construction activities will be sampledand analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - NA at GCSP Site; site is not within floodplain or wetlands.
NA at GCSP Site; site is not within floodplain or wetlands.
NA at GCSP Site; site is not within floodplain or wetlands. NA at GCSP Site; site is not within floodplain or wetlands.
- - NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered species present. NA at GCSP Site; no endangered
species present. NA at GCSP Site; no endangered species present.
- - NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures identified. NA at GCSP Site; no historic structures
identified. NA at GCSP Site; no historic structures identified.
- - NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
NA at GCSP Site; no archaeological or historic relics identified.
- -
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compoundswhere the State of NM allowable limits are more stringent than EPA MCLs.
These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
The substantive provisions of these regulations must be met as part of a reinjection program. These regulations must be complied with for compounds where the State of NM allowable limits are more stringent than EPA MCLs.
- - NA for this alternative, no generation of hazardous waste will occur.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed todetermine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste and appropriate waste storage and disposal practices will be followed.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this
alternative. Discharges of process air will meet the air qualtiy standards.
- - No discharges associated with this alternative. No discharges associated with this alternative. No discharges associated with this
alternative.Water quality criteria may be relevant and appropriate to ground water or other discharges to surface water.
- -
MCLs are applicable. MCLs are relevantand appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevantand appropriate since there is no mechanism to prevent the ground water from being used for drinking.
MCLs are applicable. MCLs are relevant and appropriate since there is no mechanism to prevent the ground water from being used for drinking.
Deeper Ground Water
Table 11Summary of ARARs
Table 12Description of ARARs for Selected Remedy
Authority Medium Regulation / Requirement Status Synopsis of Requirement Action to be Taken to Attain Requirement
Federal Regulatory Requirement
Air 40 CFR 50–National Primary and Secondary Ambient Air Quality Standards
Applicable Establishes Ambient Air Quality Standards. Compliance is achieved through compliance with state and local rules established pursuant to a State Implementation Plan (SIP).
The selected remedy, including thermal source-area treatment and residential indoor air vapor mitigation systems, will comply with these regulations. The vapor mitigation systems are not anticipated to emit vapor at concentrations exceeding any regulated levels.
Federal Regulatory Requirement
Air 40 CFR 61 Subpart V–National Emission Standards for Hazardous Air Pollutants: Equipment Leaks
Potentially applicable if remedial alternative includes regulated compounds or equipment.
Establishes requirements for controlling fugitive emissions of volatile hazardous air pollutants from designated equipment.
The selected remedy, including thermal source-area treatment and residential indoor air vapor mitigation systems, will be designed to control fugitive emissions.
Federal Regulatory Requirement
Air 40 CFR 264.AA–Air Emission Standards for Process Vents
Potentially applicable if RCRA hazardous waste is treated in designated equipment.
Requires total organic emissions from air strippers or steam strippers to be reduced below 1.4 kg/hr and 2.8 Mg/yr or that total organic emissions be reduced by 95 percent by weight.
Off-gas controls for treatment systems (such as thermal treatment at source areas) will be designed to meet the emissions reduction requirements.
State Regulatory Requirement
Air 20.2 New Mexico Administrative Code (NMAC)
Potentially applicable if remedial activities involve sources subject to regulation.
Establishes ambient air quality standards, performance standards for specific sources of air pollutants, and specifies monitoring methods.
The selected remedy, including thermal source-area treatment and residential indoor air vapor mitigation systems, will be designed to comply with these regulations.
Federal Regulatory Requirement
Surface Discharges of
Treated Ground Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 208(b)
Relevant and appropriate The proposed action must be consistent with regional water quality management plans as developed under Section 208 of Clean Water Act. Substantive requirements adopted by the state pursuant to Section 208 of the Clean Water Act would be applicable to direct discharge of treatment system effluent or other discharges to surface water.
Treated ground water effluent from treatment systems will comply with these regulations, if discharged to surface water.
Federal Regulatory Requirement
Surface Discharges of
Treated Ground Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 304
Water quality criteria may be relevant and appropriate to groundwater or other discharges to surface water.
Establishes water quality criteria for specific pollutants for the protection of human health and for the protection of aquatic life. These federal water quality criteria are non-enforceable guidelines used by the state to set water quality standards for surface water
Treated ground water effluent from treatment systems will comply with enforceable regulations, if discharged to surface water.
Federal Regulatory Requirement
Surface Discharges of
Treated Ground Water
Federal Water Pollution Control Act as amended by the Clean Water Act of 1977, Section 402
Although remedial alternatives are unlikely to include a source category subject to NPDES effluent limitations, some limitations may be relevant and appropriate to discharges to surface water if the remedial alternative includes a technology substantially similar to that employed by a regulated source category.
Establishes effluent limitations for the discharge of specific pollutants. Section 402 establishes the National Pollutant Discharge Elimination System (NPDES). which enforces effluent limitations on point source discharges through site-specific and general permits.
Treated ground water effluent from treatment systems will comply with these regulations, if discharged to surface water.
Federal Regulatory Requirement
Surface Discharges of
Treated Ground Water
40 CFR Part 122 Subpart B Although NPDES permit coverage is not required for on-site discharges of storm water, substantive requirements, including implementing best management practices to prevent discharge of pollutants to storm water, are applicable to construction activities disturbing one acre or more.
Requires obtaining an NPDES permit for discharge of storm water from specified industrial and construction activities, developing a storm water pollution prevention plan, implementing best management practices to prevent discharge of pollutants to storm water, and monitoring storm water discharges.
The substantive requirements for discharge would be completed, if applicable.
Table 12Description of ARARs for Selected Remedy
Authority Medium Regulation / Requirement Status Synopsis of Requirement Action to be Taken to Attain Requirement
State Regulatory Requirement
Surface Discharges of
Treated Ground Water
20.6.4 NMAC–Water Quality Standards for Interstate and Intrastate Surface Waters
Applicable to direct discharge of treatment system effluent or other process waters.
States are granted enforcement jurisdiction over direct discharges and may adopt reasonable standards to protect or enhance the uses and qualities of surface water bodies in the state.
The direct surface water discharge standards imposed by the State would be met, if applicable.
Federal Regulatory Requirement
Ground Water 40 CFR 141–National Primary Drinking Water Regulations
MCLs are applicable if the water will be supplied directly to a drinking water distribution system with a specified number of consumers or connections. MCLs are relevant and appropriate if the water could be used for drinking. MCLGs set above
l l l d
Establishes maximum contaminant levels (MCLs) and maximum contaminant level goals (MCLGs) for specific chemicals to protect drinking water quality.
The preliminary remediation goals (PRGs) for treatment of ground water have been established as the Federal MCLs.
The substantive provisions of these regulations must be met as part of a reinjection program.
Establishes the New Mexico Water Quality Control Commission Regulations regarding the re-injection of water into the subsurface.
The substantive provisions of the NMWQCC regulations would be complied with for any re-injection of water.
These regulations must be complied with should the NM standards be more stringent than EPA MCLs.
Establishes the New Mexico Water Quality Control Commission Regulations regarding discharges to ground water.
The NMWQCC regulations will apply for chemicals where the NMWQCC regulated concentration is lower than the Federal MCL.
Federal Regulatory Requirement
State Regulatory Requirement
Federal Regulatory Requirement
40 CFR 136–Guidelines Establishing Test Procedures for the Analysis of [Water] Pollutants (40 CFR 136.1-136.4)
Surface Discharges of
Treated Ground Water
Surface Discharges of
Treated Ground Water
40 CFR 122.41(l)–Monitoring Requirements
Administrative requirement applicable only for discharges to offsite surface water (potentially the Rio San Jose).
Applicable to analyses performed under NPDES permit; relevant and appropriate to analyses of onsite direct discharge of treatment system effluent or other process waters.
Substantive requirements for appropriate testing procedures would be followed within the compliance monitoring program.
A compliance monitoring program would be conducted, if applicable.
These sections require adherence to specified test methods and sample preservation procedures including container materials and sample holding times for analyses performed to comply with NPDES permit requirements.
Requires monitoring of discharges to ensure compliance. Monitoring programs shall include data on the mass, volume, and frequency of all discharge events.
20.6.2 NMAC – New Mexico Water Quality Control Regulations
Ground Water
Table 12Description of ARARs for Selected Remedy
Authority Medium Regulation / Requirement Status Synopsis of Requirement Action to be Taken to Attain Requirement
Federal Regulatory Requirement
Hazardous Waste
40 CFR 261–Identification and Listing of Hazardous Waste
Applicable for determining which wastes are hazardous and potentially subject to the hazardous waste management requirements in Parts 262-268.
Identifies those wastes subject to regulation as hazardous wastes
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste, and appropriate waste storage and disposal practices will be followed.
Federal Regulatory Requirement
Hazardous Waste
40 CFR 262-Hazardous Waste Generator Requirements
Substantive management standards are applicable to hazardous waste generated during remedial activities.
Specifies standards for management of hazardous waste by hazardous waste generators, including management in tanks and containers.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste, and appropriate waste storage and disposal practices will be followed.
Federal Regulatory Requirement
Hazardous Waste
40 CFR 264, 265 Substantive management standards are applicable to remedial activities involving on-site treatment, storage or disposal of hazardous waste.
Specifies standards for hazardous waste treatment, storage and disposal facilities, including requirements for construction, design, monitoring, operation, and closure.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste, and appropriate waste storage and disposal practices will be followed.
Federal Regulatory Requirement
Hazardous Waste
40 CFR 268-Land Disposal Restrictions
Applicable to off-site land disposal of listed or characteristic hazardous wastes, and to on-site remedies that include placement of these wastes.
The land disposal restrictions prohibit land-based disposal of listed and characteristic hazardous wastes that do not meet specified treatment standards.
Investigation-derived waste generated during investigation and construction activities will be sampled and analyzed to determine whether it is a hazardous waste, and appropriate waste storage and disposal practices will be followed.
Building Structures or
Archaeological Artifacts
Federal Regulatory Requirement
If scientific, historical, or archaeological artifacts are discovered at the site, work in the area of the site affected by such discovery will be halted pending the completion of any data recovery and preservation activities required pursuant to the act and its implementing regulations.
National Historical Preservation Act 16 USC 661 et seq. 36 CFR Part 65
Establishes procedures to provide for preservation of scientific, historical, and archaeological data that might be destroyed through alteration of terrain as a result of a federal construction project or a federally licensed activity or program.
Will be relevant and appropriate at the GCSP site during the remedial activities if scientific, historic, or archaeological artifacts are identified during implementation of the remedy.
Table 13Evaluation Criteria for Superfund Remedial Alternatives
Threshold Criteria
Primary Balancing Criteria
Modifying Criteria 1
General NCP CriteriaOverall Protection of Human Health and the Environment
Specific NCP CriteriaHow Alternative Provides Human Health and Environmental Protection
Compliance with ARARsCompliance with Chemical-Specific ARARsCompliance with Action-Specific ARARsCompliance with Location Specific ARARs
Ability to Construct and Operate the TechnologyReliability of the Technology
Magnitude of Residual RiskAdequacy and Reliability of ControlsTreatment Process Used and Materials TreatedAmount of Hazardous Materials Destroyed or TreatedDegree of Expected Reductions in Toxicity, Mobility, and VolumeDegree to Which Treatment is IrreversibleType of Residuals Remaining After TreatmentProtection of Community During Remedial ActionsProtection of Workers During Remedial ActionsEnvironmental ImpactsTime Until Remedial Action Objectives are Achieved
Capital Costs
Present Worth Cost
Ease of Undertaking Additional Remedial Actions, if NecessaryAbility to Monitor Effectiveness of Remedy
1: These criteria are fully assessed following comment on the RI/FS Report and the Proposed Plan, and are fully addressed in the ROD.
Features of the Alternative About Which the State has ReservationsElements of the Alternative the State Strongly OpposesFeatures of the Alternative the Community SupportsFeatures of the Alternative About Which the Community has Reservations
State Acceptance
Community Acceptance
Features of the Alternative the State Supports
Specific NCP CriteriaLong Term Effectiveness and Permanence
Reduction of Toxicity, Mobility, and Volume Through Treatment
Elements of the Alternative the Community Strongly Opposes
Ability to Obtain Approvals from Other AgenciesAvailability of Offsite Treatment, Storage, and Disposal Services and CapacityAvailability of Necessary Equipment and SpecialistsAvailability of Prospective Technologies
Specific NCP Criteria
Operating and Maintenance Costs
Implementability
Cost
General NCP Criteria
General NCP Criteria
Short Term Effectiveness
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative1. Overall Protection of Human Health and the
Environment2. Compliance with ARARs
How Alternative Provides Human Health and Environmental Protection
a. Compliance with Chemical-Specific ARARs
b. Compliance with Action-Specific ARARs
c. Compliance with Location Specific ARARs
Alternative 1 - No Action
Human health and the environment are not protected because COCs in indoor air exceeding PRGs remain in place. Exposure to residents occurs under this alternative.
Does not comply with chemical-specific ARARs for indoor air.
No action, so no action-specific ARARs apply.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 2 - Install Radon-Type Vapor Mitigation System
The contaminated vapors are physically isolated from the overlying structure by installing an impermeable vapor barrier and a ventilation system to remove the vapors from beneath the barrier. Human health and the environment are protected since the vapor barrier and venting system remove the pathway for volatile organics present in the subsurface to enter the structure. Once installed, contaminated soil vapors entering the structure will be reduced to an acceptable level. The measure is permanent with infrequent checks of the physical condition of the barrier and continuing operation of the ventilation system.
The reduction of COC-containing vapors from entering the interiors of the residences will result in indoor air meeting chemical-specific ARARs.
This alternative meets the action-specific ARARs for the reduction of COCs in indoor air to acceptable risk levels.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 3. Long Term Effectiveness and Permanence 4. Reduction of Toxicity, Mobility, and Volume Through Treatment
a. Magnitude of Residual Risk
b. Adequacy and Reliability of Controls
a. Treatment Process Used and Materials Treated
b. Amount of Hazardous Materials Destroyed or Treated
Alternative 1 - No Action
Vapor intrusion of COCs above acceptable risk levels is allowed to continue.
No controls implemented. Not applicable. Not applicable.
Alternative 2 - Install Radon-Type Vapor Mitigation System
As long as the barrier and ventilation system are kept in good working order (i.e. no tears or abrasions in the barrier and operation of the ventilation fan), the system will not allow vapor intrusion of COCs above acceptable risk levels.
The installation of barrier and ventilation materials is adequate to prevent vapor intrusion. The control is reliable as it is commonly used to prevent radon intrusion into residential structures. Long-term adequacy and reliability of this control ultimately depends on elimination of the vapor intrusion pathway by remediation of shallow ground water. Failure of any of the vapor mitigation system components or significant downtime due to maintenance can result in loss of vapor intrusion control.
Treatment is via the installation of a synthetic liner and ventilation system. Chlorinated VOCs are prevented from entering the residential structure via vapor intrusion.
COCs are not treated or destroyed. They are physically blocked from entering the residential structures.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 4. Reduction of Toxicity, Mobility, and Volume Through Treatment
c. Degree of Expected Reductions in Toxicity, Mobility, and Volume
c. Degree of Expected Reductions in Toxicity, Mobility, and Volume
c. Degree of Expected Reductions in Toxicity, Mobility, and Volume
Alternative 1 - No Action
Not applicable. Not applicable. Original COCs would remain as residuals since no treatment occurs.
Alternative 2 - Install Radon-Type Vapor Mitigation System
The volume of COCs will be reduced to meet RAOs. COCs are not treated or destroyed, they are prevented from entering the residential structure using a synthetic vapor barrier and ventilation system.
Treatment is reversible should the vapor barrier and ventilation system be removed. However, other remedies forthe GCSP site are expected to mitigate the source of vapor intrusion, which is contaminated soil and ground water.
Vapor intrusion pathway is removed by installing a physical barrier. Residual COCs inside the residence would quickly dissipate. If no other active treatment is conducted at the site, the original COCs will remain in the subsurface as residuals since the vapor barriers do not provide treatment. Given active treatment of the site, no residuals are ultimately anticipated in the subsurface.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 5. Short Term Effectiveness
a. Protection of Community During Remedial Actions
b. Protection of Workers During Remedial Actions
c. Environmental Impacts d. Time Until Remedial Action Objectives are
Achieved
Alternative 1 - No Action
The No Action Alternative does not involve construction and does not impact the community. However, the original community risks due to presence of COCs will remain.
Not applicable. Not applicable. RAOs would not be achieved.
Alternative 2 - Install Radon-Type Vapor Mitigation System
The installation of this alternative will not disturb COCs or increase their concentration in indoor air. The vapor mitigation systemsinvolve short-term inconvenience to the specific property owners where systems are installed. Installation will require access to the crawl space or basement beneath the structure for placement of thevapor barrier, and installation of vapor piping within walls tothe roof.
Workers will wear appropriate PPE (i.e. respirators) if site conditions warrant. However, the vapor intrusion risk is for long term exposure to COCs, not exposure above permissible exposure limits.
Subsurface soil vapors will be exhausted into the atmosphere above the roof of structures where systems are installed.
RAOs will be achieved upon completion of the installation of the vapor barrier and ventilation system.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 6. Implementability
a. Ability to Construct and Operate the Technology
b. Reliability of the Technology
c. Ease of Undertaking Additional Remedial Actions, if
Necessary
d. Ability to Monitor Effectiveness of Remedy
Alternative 1 - No Action
Not applicable. Not applicable. Since this alternative involves no action it would provide no obstructions to other future action.
No actions and no continued monitoring would be undertaken.
Alternative 2 - Install Radon-Type Vapor Mitigation System
This alternative is easily implemented using readily available materials and labor.
Vapor barriers and ventilation systems are reliable methods of preventing vapor intrusion. The technology has been commonly used to mitigate radon intrusion into residential structures.
Easy to take on other actions such as more aggressive ventilation measures.
Indoor air sampling and analysis is easily performed on a routine basis to monitor COC concentrations in indoor air.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 6. Implementability
e. Ability to Obtain Approvals from Other Agencies
f. Availability of Offsite Treatment, Storage, and Disposal Services and
Capacity
g. Availability of Necessary Equipment and Specialists
h. Availability of Prospective Technologies
Alternative 1 - No Action
Since no actions would be taken there would be no approvals or coordination with other agencies for implementation of this alternative. However, it may be difficult to gain approval from other stakeholder agencies for no action to meet RAOs.
Not applicable. Not applicable. Not applicable.
Alternative 2 - Install Radon-Type Vapor Mitigation System
Access to private residential property will be required. However, approval is likely because the alternative results in an immediate cessation in vapor intrusion into the residential structures.
Not required for performance of this alternative.
Would be able to hire the equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
Vapor barriers and ventilation systems are readily available methods of preventing vapor intrusion. The technology hasbeen commonly used to mitigate radon intrusion into residential structures.
Table 14Comparison of Remedial Alternatives
Vapor-Intrusion Mitigation
Evaluation CriteriaRemedial
Alternative 7. Cost
a. Capital Costs
b. Operating and
Maintenance Costs
c. Present Worth Cost
Lower Range Cost (-30%)
Upper Range Cost (+50%)
Alternative 1 - No Action
$0.00 $0.00 $0.00 No Not Acceptable
Alternative 2 - Install Radon-Type Vapor Mitigation System
$381,661.00 $0.00 $381,661.00 $267,162.70 $572,491.50 Yes Acceptable
8. State Acceptance
9. Community Acceptance
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 1. Overall Protection of Human Health and the Environment
How Alternative Provides Human Health and Environmental Protection
Alternative 1 - No Action Existing ground water COCs in the shallow ground water plume core and hot spot exist at concentrations three orders of magnitude greater than the MCLs. Ground water in the source area are a continuing source to the downgradient plume and ground water contamination is a source of vapor intrusion into residential structures. This approach cannot meet the RAOs in a timely fashion.
Human health and the environment are not protected because ground water exceeding PRGs remains in place. Exposure to residents and construction / utility workers could occur under this alternative.
The vapor intrusion pathway remains and indoor air exceeding PRGs remains in place. Exposure to residents and workers could occur under this alternative.
Alternative 2 - Thermal Resistive Heating
Removal of COCs within source area soils and groundwater will reduce the source of the ongoing ground water contamination. With reduction in ground water contamination, the source of the vapor intrusion COCs will also be reduced.
Once the COCs are remediated at the source, downgradient ground water concentrations are expected to decrease and vapor intrusion risk to decrease.
Alternative 3 - ISCO with Follow-On ERD
An appropriately designed ISCO and ERD injection program will result in the removal of COCs within the source area to achieve PRGs. Source area contaminated ground water will be treated to PRGs if adequate oxidant contact and/or complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved for all COCs, in all areas of the source area, equally or possibly more toxic intermediary products could persist. If DNAPL or sorbed soil contamination persists following completion of ISCO and ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated in the source area downgradient ground water concentrations and resulting risk are expected to decrease over time.
As concentrations of COCs in the source area ground water are reduced the risk of vapor intrusion will decrease.
Alternative 4 - ERD (Gridded)
An appropriately designed ERD injection program will result in the removal of COCs within the source area to achieve PRGs. Source area contaminated ground water will be treated to PRGs if complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved for all COCs, in all areas of the source area, equally or or possibly more toxic intermediary products could persist. If DNAPL or sorbed soil contamination persists following completion of ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated in the source area downgradient ground water concentrations and resulting risk are expected to decrease over time.
As concentrations of COCs in the source area ground water are reduced the risk of vapor intrusion will decrease.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 2. Compliance with ARARs
a. Compliance with Chemical-Specific ARARs b. Compliance with Action-Specific ARARs
c. Compliance with Location Specific ARARs
Alternative 1 - No Action Does not comply with chemical-specific ARARs for ground water or indoor air.
The proposed alternative will have no action so action-specific ARARs will not apply.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 2 - Thermal Resistive Heating
Source area ground water may approach chemical-specific ARARs upon completion of the alternative although it is unlikely that this technology will fully achieve RAOs. Polishing via an additional technology either in the source area or in the downgradient plume core may be necessary. The depth of treatment is to 80 ft bgs at Holiday Cleaners source area and 35 ft bgs at the abandoned dry cleaners source area.
The proposed alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 3 - ISCO with Follow-On ERD
The source area ground water is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 80 ft bgs at the Holiday Cleaners source area and 35 ft bgs at the abandoned dry cleaners source area.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The proposed alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 4 - ERD (Gridded)
The source area ground water is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 80 ft bgs at the Holiday Cleaners source area and 35 ft bgs at the abandoned dry cleaners source area.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The proposed alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 3. Long Term Effectiveness and Permanence
a. Magnitude of Residual Risk
Alternative 1 - No Action Source of both ground water and vapor intrusion impacts is not removed under this alternative. Significant residual risk remains.
Alternative 2 - Thermal Resistive Heating
An appropriately-designed thermal source area treatment is expected to approach PRGs and RAOs and reduce residual risk at the source areas. Final polishing following thermal treatment may be necessary to meet PRGs and RAOs, and may include targeted ERD or ISCO treatments. Residual risk may remain at depths greater than 80 ft bgs at the Holiday Cleaners and 35 ft bgs at the abandoned dry cleaners, since these zones are not actively treated.
When RAOs are achieved at the source area the residual risk in the downgradient aquifer will also be slowly achieved.
This alternative is anticipated to ultimately lower the risk from vapor intrusion and ground water exposure.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 3 - ISCO with Follow-On ERD
Source area treatment via ISCO with follow-on ERD can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ISCO and ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 80-ft bgs at Holiday Cleaners and greater than 35-ft bgs at the Abandoned Cleaners since these zones are not actively treated by this alternative.
Until source area ground water COC concentrations meet PRGs they may continue to support a significant vapor intrusion risk.
This alternative is anticipated to ultimately lower the risk from vapor intrusion and ground water exposure.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 4 - ERD (Gridded)
Source area treatment via ERD can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 80-ft bgs at Holiday Cleaners and greater than 35-ft bgs at the Abandoned Cleaners since these zones are not actively treated by this alternative.
Until source area ground water COC concentrations meet PRGs they may continue to support a significant vapor intrusion risk.
This alternative is anticipated to ultimately lower the risk from vapor intrusion and ground water exposure.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 3. Long Term Effectiveness and Permanence
b. Adequacy and Reliability of Controls
Alternative 1 - No Action No controls implemented.
Alternative 2 - Thermal Resistive Heating
Thermal resistive heating removes the COCs from the aquifer and vadose zone soils. Control is permanent as the COCs are removed to PRGs at the source.
If appropriately designed the thermal resistance heating remediation would occur over the course of one implementation event. Subsequent thermal treatments over time would not be required. However, meeting RAOs at the source area with a single application will require an extremely high removal efficiency and thermal treatment alone may not fully meet all ARARs and RAOs. Implementation of some additional polishing technology in the source area or in the downgradient plume core may be necessary.
If any residual DNAPL is present, the treated source area may become recontaminated and this alternative may not meet RAOs..
A loss of process control (incomplete vapor recovery using SVE) could lead to escape of COC vapors to the atmosphere or the recondensing of COC vapors outside the treatment area.
Alternative 3 - ISCO with Follow-On ERD
ISCO and ERD consume the COCs to RAOs. Control is permanent as the COCs are removed to PRGs at the source.
Both injected oxidants and carbon-source amendments have limited residence times in the aquifer. Materials are consumed and will require multiple injection events. Both ISCO and ERD have been proven reliable methods of treating the COCs, but both require injection of amendments into the subsurface which can be difficult to control. ISCO is more sensitive to injection uniformity and initial contact with contaminants than is ERD since ERD amendments have a longer residence time and can migrate with ground water to interact with contaminants. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the conclusion of the ISCO and/or carbon-source amendment injections, additional injection of materials may be required.
If any residual DNAPL is present, this alternative may not meet RAOs.
Alternative 4 - ERD (Gridded)
ERD consumes the COCs to RAOs. Control is permanent as the COCs are removed to PRGs at the source.
Injected carbon-source amendments have limited residence times in the aquifer. Materials are consumed and will require multiple injection events. ERD has been proven a reliable method of treating the COCs, but requires injection of amendments into the subsurface which can be difficult to control. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the carbon-source amendment injections, additional injection of materials may be required.
If any residual DNAPL is present, this alternative may not meet RAOs.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 4. Reduction of Toxicity, Mobility, and Volume Through Treatment
a. Treatment Process Used and Materials
Treated
b. Amount of Hazardous Materials Destroyed or
Treated
c. Degree of Expected Reductions in Toxicity, Mobility,
and Volume
d. Degree to Which Treatment is Irreversible
e. Type of Residuals Remaining After
Treatment
Alternative 1 - No Action Not applicable. Not applicable. Not applicable. Not applicable. Original COCs would remain as residuals since no treatment occurs.
Alternative 2 - Thermal Resistive Heating
Treatment via volatilization of COCs induced by heating of the subsurface and recovery of the COCs using soil vapor extraction. The offgas is collected and treated prior to discharge. Treats volatile organic compounds including the site-specific COCs.
Pilot-scale testing would provide information on quantity of PCE (and other chlorinated VOCs) treated by the thermal resistive heating alternative. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
A substantial degree of reductions in toxicity, mobility, and contaminant volume are anticipated since the alternative will be designed to reduce COC concentrations.
This alternative is irreversible but the treatment zone could be recontaminated if DNAPL remains present in the treatment zone after the completion of the remedial action.
Completely successful thermal treatment leaves no residual volatile COCs behind, as they are all volatilized.
Alternative 3 - ISCO with Follow-On ERD
ISCO treatment occurs via destructive oxidation of organic contaminants and mineralization to carbon dioxide, water, and chloride ISCO is capable of treating all organic compounds if adequate contact can be achieved. Remaining COC concentrations will be treated via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by ISCO and follow-on ERD. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
If adequate oxidant contact and sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist.
If able to fully proceed, the components of this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via direct oxidation or reductive dechlorination over time. However the treatment zone could be recontaminated if DNAPL remains present in the treatment zone after the completion of the remedial action.
Residuals following oxidation by ISCO will include carbon dioxide, water, and chloride, and possibly acetone, dissolved metals, or Mn-oxides. Residuals following reductive dechlorination of PCE via ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride.
Alternative 4 - ERD (Gridded)
Treatment of chlorinated halocarbons via reductive dechlorination as carbon-source amendments are injected into the aquifer matrix.
Pilot-scale testing would also provide information on quantity of PCE (and other chlorinated VOCs) treated by ERD, following each ERD injection. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist.
If able to fully proceed, the components of this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via reductive dechlorination over time. However the treatment zone could be recontaminated if DNAPL remains present in the treatment zone after the completion of the remedial action.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 5. Short Term Effectiveness
a. Protection of Community During Remedial Actions
Alternative 1 - No Action Not applicable.
Alternative 2 - Thermal Resistive Heating
Recovery of vapors would need to be performed during thermal heating.
Air monitoring would need to performed during intrusive activities such as drilling and excavation for installation of supporting infrastructure.
Large electricity-handling devices would be present during alternative implementation and would require appropriate fencing and setback from public.
Alternative 3 - ISCO with Follow-On ERD
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Appropriate safety measures would need to be implemented when handling oxidants to protect community members from contact with oxidants prior to injection.
Alternative 4 - ERD (Gridded)
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 5. Short Term Effectiveness
b. Protection of Workers During Remedial Actions
c. Environmental Impacts d. Time Until Remedial Action Objectives are Achieved
Alternative 1 - No Action Not applicable. Not applicable. RAOs would not be achieved.
Alternative 2 - Thermal Resistive Heating
Would require measures to protect workers from COCs during installation of thermal treatment equipment and during operation of electrical devices.
Will need to control offgas emissions when technology is implemented.
Thermal treatment requires a period between nine months and one year to heat the subsurface to the point where COCs are mobilized (volatilized) and operate until the RAOs are met. A several-month long cool down period then follows and polishing treatments can be conducted. Total time to meet RAOs is assumed to be 18 months to 2 years.
Alternative 3 - ISCO with Follow-On ERD
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
Given available ground water flow velocities, this alternative is anticipated to require 1 year of ISCO injections followed by 6 years of ERD treatments to achieve RAOs based on a gridded application.
Alternative 4 - ERD (Gridded)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
The ERD alternative is anticipated to require 15 years to achieve RAOs at the source areas, based on a gridded application.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 6. Implementability
a. Ability to Construct and Operate the Technology
b. Reliability of the Technology c. Ease of Undertaking Additional Remedial Actions, if Necessary
Alternative 1 - No Action Not applicable. Not applicable. Since this alternative involves no action it would provide no obstructions to other future action.
Alternative 2 - Thermal Resistive Heating
Thermal treatment requires specialized equipment installed in traditionally drilled and constructed wells.
The technology requires access to the entire ground surface overlying the treatment zone.
A relatively limited number of vendors specializing in thermal treatment technology are available.
Since the technology is installed in wells that are relatively easily installed, that portion of the alternative is reliably executed. The operation of the thermal probes requires substantial quantities of electricity. The availability of the electricity may not be reliable as it is subject to periodic outages, which will require restart of the system.
Other additional remedial actions would be relatively easy to implement at the site. Other remedial actions may be limited only by application near the thermal treatment probes which could damage or reduce the effectiveness of the probes.
Alternative 3 - ISCO with Follow-On ERD
ISCO and carbon-source amendment treatments require specialized equipment which is readily available. ISCO and carbon-source amendments (i.e. permanganate, emulsified vegetable oil) are readily available.
ISCO and ERD are reliable technologies as they are relatively easy to implement. The technologies are less reliable as to how rapidly they can inject amendments into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other remedial actions could be implemented at the site. However, additional actions would need to be compatible with injected oxidants and/or maintaining a reductive environment in the aquifer to promote biodegradation.
Alternative 4 - ERD (Gridded)
ERD treatments require specialized equipment which is readily available through numerous vendors. ERD amendments (i.e. emulsified vegetable oil) are readily available.
Same as Alternative 3 for source area treatment. ERD as a stand-alone source area treatment can be successful provided that suitable quantities of the ERD amendment remains in the subsurface over time.
Other remedial actions could be implemented at the site. However, additional actions would need to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation CriteriaRemedial Alternative 6. Implementability
d. Ability to Monitor Effectiveness of
Remedy
e. Ability to Obtain Approvals from Other
Agencies
f. Availability of Offsite Treatment,
Storage, and Disposal Services
and Capacity
g. Availability of Necessary Equipment
and Specialists
h. Availability of Prospective Technologies
Alternative 1 - No Action No actions and no continued monitoring would be undertaken.
Since no actions would be taken there would be no approvals or coordination with other agencies for implementation of this alternative. However, it may be difficult to gain approval from other stakeholder agencies for no action to meet RAOs.
Not applicable. Not applicable. Not applicable.
Alternative 2 - Thermal Resistive Heating
Ground water monitoring wells can be readily installed to track the performance of this alternative. Soil borings can be completed using direct-push technology to monitor the performance in source area soils.
This alternative will require access to public and private property, air quality permitting, and may also require the relocation of buried utilities. Each of these requirements will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
Performance of Thermal Resistive Heating is an available technology, and currently expanding in availability and implementation at various sites. This technology requires pilot-scale testing to determine the ideal spacing for the heater and vapor recovery probes to effectively reach the entire treatment zone in order to reach PRGs.
Alternative 3 - ISCO with Follow-On ERD
Ground water monitoring wells can be readily installed to track the performance of this alternative.
This alternative will require access to public and private property and approval to inject ISCO and/or ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ISCO and ERD are readily available technologies. ISCO requires pilot-scale testing to confirm oxidant dosing, injection spacing, and other final remedy requirements. Enhanced biodegradation is a readily available technology, but also requires pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Alternative 4 - ERD (Gridded)
Ground water monitoring wells can be readily installed to track the performance of this alternative.
This alternative will require access to public and private property and approval to inject ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ERD is a readily available technology but requires pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Table 15Comparison of Remedial Alternatives
Source Area Treatment
Evaluation Criteria7. Cost
Capital Costs Operating and Maintenance
Costs
Present Worth Cost
Lower Range Cost (-30%)
Upper Range Cost (+50%)
Alternative 1 - No Action
$0 $0 $0.00 $0.00 $0.00 No Not Acceptable
Alternative 2 - Thermal Resistive Heating
$8,018,000.00 $0.00 $8,018,210.00 $5,612,747.00 $12,027,315.00 Yes Acceptable
Alternative 3 - ISCO with Follow-On ERD
$6,256,961.00 $3,178,948.00 $9,435,910.00 $6,605,137.00 $14,153,865.00 No Acceptable
Alternative 4 - ERD (Gridded)
$2,391,198.00 $6,074,342.00 $8,465,540.00 $5,925,878.00 $12,698,310.00 No Acceptable
8. State Acceptance
9. Community Acceptance
Remedial Alternative
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 1. Overall Protection of Human Health and the Environment
How Alternative Provides Human Health and Environmental Protection
Alternative 1 - No Action
Existing ground water COCs in the shallow ground water plume core and hot spot exist at concentrations three orders of magnitude greater than the MCLs. Ground water in the shallow plume core and hot spot area continuing source to the downgradient plume and ground water contamination is a source of vapor intrusion into residential structures. Natural attenuation mechanisms cannot meet the RAOs in a timely fashion.
Human health and the environment are not protected because ground water exceeding PRGs remains in place. Exposure to residents and construction / utility workers could occur under this alternative.
The vapor intrusion pathway remains and indoor air exceeding PRGs remains in place. Exposure to residents and workers could occur under this alternative.
Alternative 2 - Zero-Valent Iron PRB
Appropriately designed PRB walls should be able to remediate dissolved phase ground water contamination to meet PRGs in the shallow plume core and hot spot area at the conclusion of the remedial action. However, since ground water remediation rates are limited by the naturalground water velocity potential for human exposure to ground water exceeding PRGs will continue for several years before achieving the RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs, this alternative will no longer effectively achieve RAOs or limit residual risk. Additionally, the extended residence of ground water exceeding PRGs in the shallow plume core provides potential for additional vertical migration of contamination.
Once the COCs are remediated at the plume core and hot spot, downgradient ground water concentrations and resulting risk are expected to decrease over time.
The slow treatment rate of the highly contaminated shallow ground water in the shallow ground water plume core and hot spot as it moves between PRB wall transects will continue to support vapor intrusion for an extended period of time.
Alternative 3 - ISCO with Follow-On ERD
An appropriately designed ISCO and ERD injection program will result in the removal of COCs within the shallow plume core and other shallow hot spots to achieve PRGs. Shallow contaminated ground water will be treated to PRGs if adequate oxidant contact and/or complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist. If DNAPL or sorbed soil contamination persists following completion of ISCO and ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated in the shallow plume core and hot spot downgradient ground water concentrations and resulting risk are expected to decrease over time.
As concentrations of COCs in the shallow ground water plume core and hot spot are reduced the risk of vapor intrusion will decrease.
Alternative 4 - ERD (Bio Barriers)
Appropriately designed ERD bio barriers will result in the removal of COCs within the shallow plume core and other shallow hot spots to achieve PRGs. Shallow contaminated ground water will be treated to PRGs if adequate and complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist. If DNAPL or sorbed soil contamination persists following completion ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated at the shallow plume core and hot spot, downgradient ground water concentrations and resulting risk are expected to decrease over time.
As concentrations of COCs in the shallow ground water plume core and hot spot are reduced the risk of vapor intrusion will decrease.
Alternative 5 - Pump & Treat
An appropriately designed pump and treat system will result in the removal of COCs within the shallow plume core and other shallow hot spots . The shallow plume core and hotspot ground water may achieve PRGs although remediation would likely take a very extended period. If DNAPL or sorbed soil contamination is present a dissolved phase plume will persist or rebound in the aquifer and this alternative may not achieve RAOs or limit residual risk within an acceptable time period.
Once the COCs are remediated at the shallow ground water plume core and hotspot downgradient ground water concentrations and resulting risk are expected to decrease over time.
As concentrations of COCs in the shallow ground water plume core and hot spot are reduced the risk of vapor intrusion will decrease.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 2. Compliance with ARARs
a. Compliance with Chemical-Specific ARARs b. Compliance with Action-Specific ARARs
c. Compliance with Location Specific ARARs
Alternative 1 - No Action
Does not comply with chemical-specific ARARs for ground water or indoor air.
The proposed alternative will have not action so action-specific ARARs will not apply.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 2 - Zero-Valent Iron PRB
Ground water exiting appropriately designed PRB walls will meet chemical-specific ARARs. However, the slow ground water flow velocity will result in extended periods of time for all ground water between individual PRB transects to reach and exit a PRB. Therefore, the primary shallow plume core ground water will not rapidly meet chemical-specific ARARs. The depth of treatment is to 20 ft bgs.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 3 - ISCO with Follow-On ERD
The shallow ground water plume core and hot spot area is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 4 - ERD (Bio Barriers)
The shallow ground water plume core and hot spot area is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 5 - Pump & Treat
The shallow ground water plume core and hot spot area is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
Remediation of dissolved contamination in shallow water will contribute to complying with indoor air PRGs over time.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 3. Long Term Effectiveness and Permanence
a. Magnitude of Residual Risk
Alternative 1 - No Action
Source of both ground water and vapor intrusion impacts is not removed under this alternative. Significant residual risk remains.
Alternative 2 - Zero-Valent Iron PRB
PRBs designed for site-specific dissolved phase ground water plume conditions will achieve long term PRGs and RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs, this alternative will no longer effectively achieve RAOs or limit residual risk.
Given the passive nature of the alternative high concentrations of COCs will persist in shallow ground water and continue to support a significant vapor intrusion risk for many years.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 3 - ISCO with Follow-On ERD
Shallow ground water plume core and hot spot treatment via ISCO with follow-on ERD can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ISCO and ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative.
Until shallow ground water plume core and hot spot COC concentrations meet PRGs they may continue to support a significant vapor intrusion risk.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 4 - ERD (Bio Barriers)
Shallow ground water plume core and hot spot treatment via ERD bio barriers can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternativewill no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative.
Until shallow ground water plume core and hot spot COC concentrations meet PRGs they may continue to support a significant vapor intrusion risk.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 5 - Pump & Treat
Shallow ground water plume core and hot spot treatment via pump and treat methods can be designed to meet long term PRGs and RAOS and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination is present, pump and treat technology in low permeability GCSP site sediments may take greater than 40 years to achieve RAOs. Additionally, portions of the aquifer that have been partially remediated may be subject to recontamination or rebound from remaining sorbed or DNAPL contaminant sources. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative.
Until shallow ground water plume core and hot spot COC concentrations meet PRGs they may continue to support a significant vapor intrusion risk.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 3. Long Term Effectiveness and Permanence
b. Adequacy and Reliability of Controls
Alternative 1 - No Action
No controls implemented.
Alternative 2 - Zero-Valent Iron PRB
The long-term effectiveness of PRBs will decrease over time as the reactive material in the PRBs degrades. The ZVI-PRB walls have been designed for a 20-year service life, and will require replacement at 20 years since RAOs are not expected to be met for 40 years. The effectiveness of the PRB walls is dependant upon a thorough understanding of the hydraulic flow conditions within the aquifer and, if not properly designed or installed, bypass of ground water around, below, or above the barrier can occur. During installation, the smearing of clays on the trench-wall face can limit the permeability of the barrier, as can fouling over time within the ZVI wall.
If untreated dissolved phase contamination persists, or DNAPL source material remains, beyond the service life of the PRBs, re-installation of the PRBs may be required.
Alternative 3 - ISCO with Follow-On ERD
Both injected oxidants and carbon-source amendments have limited residence times in the aquifer. Materials are consumed and will require multiple injection events. Both ISCO and ERD have been proven reliable methods of treating the COCs, but both require injection of amendments into the subsurface which can be difficult to control. ISCO is more sensitive to injection uniformity and initial contact with contaminants than is ERD since ERD amendments have a longer residence time and can migrate with ground water to interact with contaminants. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the conclusion of the ISCO and/or carbon-source amendment injections, additional injection of materials may be required.
Alternative 4 - ERD (Bio Barriers)
Injected carbon-source amendments have limited residence time in the aquifer. Materials are consumed and will require multiple injection events. ERD has been proven a reliable method of treating the COCs, but requires injection of amendments into the subsurface which can be difficult to control. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the conclusion of the carbon-source amendment injections, additional injection of materials may be required.
Alternative 5 - Pump & Treat
Damage, fouling, or loss of specific capacity of pump and treat system extraction and injection wells may require replacement of these components over the extended operational period of this alternative. Based on site-specific geochemical conditions, extracted ground water may require addition of conditioning chemicals to modify pH or other factors which may degrade system components more rapidly and necessitate replacement. Significant failures of equipment during treatment may require the cessation of treatment while repairs are conducted.
If untreated dissolved phase contamination persists, or DNAPL source material remains after the conclusion of the anticipated pump and treat remedial period, continued operation of the system may be required for a very long additional time.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 4. Reduction of Toxicity, Mobility, and Volume Through Treatment
a. Treatment Process Used and Materials Treated
b. Amount of Hazardous Materials Destroyed or Treated
c. Degree of Expected Reductions in Toxicity, Mobility, and Volume
Alternative 1 - No Action
Not applicable. Not applicable. Not applicable.
Alternative 2 - Zero-Valent Iron PRB
ZVI-PRB walls are effective for treatment of chlorinated ethenes and ethanes (including the COCs), select chlorinated pesticides, and some metals.
Bench-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) treated by passing through the PRBs. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
Using site-specific data PRBs will be designed to meet PRGs on the discharge side of the treatment walls.
Alternative 3 - ISCO with Follow-On ERD
ISCO treatment occurs via destructive oxidation of organic contaminants and mineralization to carbon dioxide, water, and chloride ISCO is capable of treating all organic compounds if adequate contact can be achieved. Remaining COC concentrations will be treated via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by ISCO and follow-on ERD. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
If adequate oxidant contact and sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist.
Alternative 4 - ERD (Bio Barriers)
Treatment of VOC COCs occurs via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by ERD bio barriers. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow plume core and hot spot, equally or more toxic intermediary products may persist.
Alternative 5 - Pump & Treat
COCs are stripped (volatilized) from ground water. The vapor stream is recovered and volatile components are further treated by passage through GAC. The final polished offgas stream is discharged to the atmosphere. The final remediated ground water stream is re-injected into the aquifer. The COCs at the site are generally amenable to treatment via air stripping.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by the pump and treat alternative. Since total volume of hazardous materials is not known, total amount of material destroyed or treated can not be estimated.
Using site-specific data a pump and treat system will be designed to reduce ground water concentrations to PRGs prior to re-injection.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 4. Reduction of Toxicity, Mobility, and Volume Through Treatment
d. Degree to Which Treatment is Irreversible e. Type of Residuals Remaining After Treatment
Alternative 1 - No Action
Not applicable. Original COCs would remain as residuals since no treatment occurs.
Alternative 2 - Zero-Valent Iron PRB
Treatment will permanently reductively dechlorinate the COCs.
Residuals following reductive dechlorination of the PCE will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. Additionally, the emplaced ZVI will remain in the subsurface.
Alternative 3 - ISCO with Follow-On ERD
If able to fully proceed, the components of this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via direct oxidation or reductive dechlorination over time.
Residuals following direct oxidation by ISCO will include carbon dioxide, water, and chloride. Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. A limited residual amount of the carbon-amendment substrate may persist in the aquifer materials.
Alternative 4 - ERD (Bio Barriers)
If able to fully proceed, this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via reductive dechlorination over time.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. A limited residual amount of the carbon-amendment substrate may persist in the aquifer materials.
Alternative 5 - Pump & Treat
Removal of COCs from the ground water is generally irreversible with an appropriately designed air stripper treatment system.
Residuals following pump and treat implementation include GAC that will require offsite disposal or recycling and remediated ground water that will require re-injection.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 5. Short Term Effectiveness
a. Protection of Community During Remedial Actions b. Protection of Workers During Remedial Actions
Alternative 1 - No Action
Since no action would take place there would be no impacts to the community from implementation of this alternative. Original risks to the community from COCs would remain.
No remedial action would be implemented.
Alternative 2 - Zero-Valent Iron PRB
Air monitoring would need to performed during intrusive activities such as excavation and PRB installation. Large open trenches will be excavated in residential areas and pose a threat to the community. Significant traffic disruption would also occur.
Installation of the PRBs will likely generate hazardous waste for offsite treatment and disposal during excavation of soil for ZVI placement. Due to the shallow ground water table it is likely that some highly contaminated ground water may also be generated during some of the trenching activities which will require containment and treatment or disposal.
Excavation and intrusive onsite work as well as offsite transport of hazardous materials may pose a threat to site workers. Risk can be managed through appropriate health and safety and hazardous waste handling practices.
Alternative 3 - ISCO with Follow-On ERD
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Appropriate safety measures would need to be implemented when handling oxidants to protect community members from contact with oxidants prior to injection.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 4 - ERD (Bio Barriers)
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 5 - Pump & Treat
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Additionally, air monitoring or modeling will need to be performed to demonstrate protection of the community from unacceptable air emissions from the air stripper.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 5. Short Term Effectiveness
b. Protection of Workers During Remedial Actions
c. Environmental Impacts d. Time Until Remedial Action Objectives are Achieved
Alternative 1 - No Action
No remedial action would be implemented.
Ground water and indoor air at concentrations greater than PRGs would remain. There would be no other alternative specific environmental impacts since no remedial action occurs.
RAOs would not be achieved.
Alternative 2 - Zero-Valent Iron PRB
Generation of highly contaminated ground water may pose a threat to site workers. Risk can be managed through appropriate health and safety monitoring and waste handling practices.
Offsite transport and disposal of hazardous materials may pose a threat to the environment. Risk can be managed through appropriate hazardous waste handling and practices.
Due to the passive nature of this alternative, the treatment rate of the shallow ground water plume will be limited by the ground water flow velocity. Ground water within the shallow plume core and hot spot is anticipated to pass through a PRB wall transect within 2 to 4 years. However, significant sorbed-phase contamination is anticipated in the regions between the PRBs and many aquifer flushings will be required to meet RAOs. This treatment method is anticipated to require 40 years to meet RAOs.
Alternative 3 - ISCO with Follow-On ERD
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
Two rounds of oxidant injection would be performed which will require a period of up to 2 years. Following ISCO, a total of 5 carbon-source amendment injections at a frequency of once every 15 months are anticipated for final ground water polishing although RAOs may still not be achieved following the final injection. RAOs are expected to be achieved within two years following the final carbon-source amendment injection. The total time for the ISCO and ERD components of the remedial action would be roughly 8 years.
Alternative 4 - ERD (Bio Barriers)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
A total of 16 carbon-source amendment injections at a frequency of once every 15 months are anticipated although RAOs will still not be achieved following the final injection. RAOs are expected to be achieved within two years following the final carbon-source amendment injection or at roughly 20 years.
Alternative 5 - Pump & Treat
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
If appropriate air emissions treatment is implemented and successful ground water reinjection can be achieved no environmental impacts are anticipated.
Due to the low hydraulic conductivity of the geologic materials at the site, the very high COC concentrations in the shallow ground water plume core and hot spot, and significant sorbed-phase contamination, the pump and treat alternative is anticipated to take over 40 years to achieve RAOs.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 6. Implementability
a. Ability to Construct and Operate the Technology
b. Reliability of the Technology c. Ease of Undertaking Additional Remedial Actions, if Necessary
d. Ability to Monitor Remedy
Effectiveness
Alternative 1 - No Action
Not applicable. Not applicable. Since this alternative involves no action it would provide no obstructions to other future action.
No actions and no continued monitoring would be undertaken.
Alternative 2 - Zero-Valent Iron PRB
Construction of PRB walls is similar to, but somewhat more complicated than, traditionaltrenching. Slurry trenching uses traditional equipment but requires maintenance of the slurry during construction. Single-pass trenching can also be used, but involves specialized equipment. PRB walls have been routinely installed at similar sites over the last ten years.
PRBs can be reliably designed and installed once site specific data collection and bench testing are complete. The reliability of implementing this technology can be impacted by lack of site-specific geologic, geochemical, and contaminant distribution data.
Other additional remedial actions would be relatively easy to implement at the site. Other remedial actions may be limited in application of certain technologies near the PRB walls which could damage or reduce the effectiveness of the walls.
Ground water monitoring wells can readily track the performance of this alternative as it pertains to remediation of the shallow ground water plume core and hot spot.
Alternative 3 - ISCO with Follow-On ERD
ISCO and carbon-source amendment treatments require specialized equipment which is readily available through numerous direct-push drilling vendors. Direct-push drilling is an easily operated technology. ISCO and carbon-source amendments (i.e. permanganate, emulsified vegetable oil) are readily available.
ISCO and ERD are reliable technologies as they are relatively easy to implement. The technologies are less reliable as to how rapidly they can inject amendments into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other remedial actions could be implemented at the site. However, additional actions would need to be compatible with injected oxidants and/or maintaining a reductive environment in the aquifer to promote biodegradation.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Alternative 4 - ERD (Bio Barriers)
Carbon-source amendment treatments require specialized equipment which is readily available through numerous direct-push drilling vendors. Direct-push drilling is an easily operated technology. Carbon-source amendments (i.e. emulsified vegetable oil) are readily available.
ERD is a reliable technology as it is relatively easy to implement. The technology is less reliable as to how rapidly amendments can be injected into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other remedial actions could be implemented at the site. However, additional actions would need to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Alternative 5 - Pump & Treat
Pump and treat alternatives utilize routine, available well installation techniques and materials and basic air stripping systems. However, site-specific geochemical conditions can present substantial challenges in bringing a successfully operating extraction, treatment, and reinjection system online. Additionally, although ground water re-injection utilizes basic well installation techniques and technology the process is subject to high operational and maintenance requirements.
Pump and treat is reliable technology as it is relatively easy to implement and uses basic ground water extraction well and technologically sound air stripping principles. However, as an operating treatment plan system it is subject to mechanical failures.
Other remedial actions could be implemented at the site. However, additional actions would need to take into account aquifer amendments that might be recovered by the pump and treat system and foul the system or reduce the effectiveness of the air stripping process.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 6. Implementability
d. Ability to Monitor Remedy Effectiveness
e. Ability to Obtain Approvals from Other Agencies
f. Availability of Offsite Treatment, Storage, and Disposal Services and
Capacity
Alternative 1 - No Action
No actions and no continued monitoring would be undertaken.
Since no actions would be taken there would be no approvals or coordination with another agencies for implementation of this alternative. However, it may be difficult to gain approval from other stakeholder agencies for no action to meet RAOs.
Not applicable.
Alternative 2 - Zero-Valent Iron PRB
Due to the extended time period it will take this alternative to address the shallow ground water concentrations that support indoor air vapor intrusion, ongoing air monitoring would continue tobe required and can be readily performed.
The installation and use of PRB walls in themselves are not anticipated to provide particular difficulties in gaining stakeholder agency approval. The extended time period over which it will take PRB walls to address ground water exceeding PRGs may not be acceptable to some stakeholder agencies. The relatively large scale construction aspect of installing PRBs may require extensive coordination with local agencies and utilities.
Material excavated during the installation of the PRB walls may generate hazardous waste which may require the selection of an offsite RCRA landfill disposal location. The volume of hazardous material generated will depend on the final designed size of the PRBs and where they would be installed at the site. The nature of the hazardous material generated and the potential treatment and disposal options will require additional site specific data and design considerations.
Alternative 3 - ISCO with Follow-On ERD
Until shallow ground water concentrations are adequately reduced to the point that they can not support indoor air vapor intrusion, ongoing air monitoring would continue to be required and can be readily performed.
This alternative will require access to public and private property and approval to inject ISCO and/or ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Alternative 4 - ERD (Bio Barriers)
Until shallow ground water concentrations are adequately reduced to the point that they can not support indoor air vapor intrusion, ongoing air monitoring would continue to be required and can be readily performed.
This alternative will require access to public and private property and approval to inject ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Alternative 5 - Pump & Treat
Until shallow ground water concentrations are adequately reduced to the point that they can not support indoor air vapor intrusion, ongoing air monitoring would continue to be required and can be readily performed.
This alternative will require access to public and private property, approval to reinject treated ground water, and approvals to discharge the treated air stream. This will require approval or authorization from owners/agencies.
Offsite recycling of GAC is readily available. Treated ground water will be reinjected back into the aquifer. The availability of reinjection is not limited, however, the technical viability of reinjection can be challenging. If offsite disposal of treated ground water was required an appropriate disposal option would need to be identified.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 6. Implementability
f. Availability of Offsite Treatment, Storage, and Disposal Services and
Capacity
g. Availability of Necessary Equipment and Specialists
h. Availability of Prospective Technologies
Alternative 1 - No Action
Not applicable. Not applicable. Not applicable.
Alternative 2 - Zero-Valent Iron PRB
Some highly contaminated ground water is likely to be generated during trenching activities due to the shallow ground water table. Contaminated water will need to be contained and potentially treated onsite or possibly discharged to the City POTW. The potential volume of ground water generated and the contaminant concentrations of that ground water and potential treatment and disposal options require additional site specific data and design considerations.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
Installation of PRB walls is an available technology, having greatly expanded over the last ten years. This technology requires bench-scale testing to determine the ideal reactive media to use within the wall, the amount of reactive material required to treat site contaminants, and the thickness of material required to meet the PRGs.
Alternative 3 - ISCO with Follow-On ERD
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ISCO and ERD are readily available technologies. ISCO requires pilot-scale testing to confirm oxidant dosing, injection spacing, and other final remedy requirements. Enhanced biodegradation is a readily available technology, but also requires pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Alternative 4 - ERD (Bio Barriers)
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ERD is a readily available technology but requires pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Alternative 5 - Pump & Treat
Offsite recycling of GAC is readily available. Treated ground water will be reinjected back into the aquifer. The availability of reinjection is not limited, however, the technical viability of reinjection can be challenging. If offsite disposal of treated ground water was required an appropriate disposal option would need to be identified.
Drilling contractors for well installation and air stripper treatment vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. These technologies are not specialized, therefore there are various vendors from which to chose.
Pump and treat systems are readily available technologies but require some level of pilot-scale testing to design final remedy requirements.
Table 16Comparison of Remedial Alternatives
Shallow Ground Water Plume Core and Hot Spot
Evaluation CriteriaRemedial Alternative 7. Cost
a. Capital Costs b. Operating and Maintenance
c. Present Worth Cost
Lower Range Cost (-30%)
Upper Range Cost (+50%)
Alternative 1 - No Action
$0 $0 $0.00 $0.00 $0.00 No Not Acceptable
Alternative 2 - Zero-Valent Iron PRB
$4,937,170.00 $837,108.00 $5,774,278.00 $4,041,994.60 $8,661,417.00 No Acceptable
Alternative 3 - ISCO with Follow-On ERD
$4,443,940.00 $2,286,786.00 $6,730,726.00 $4,711,508.20 $10,096,089.00 Yes Acceptable
Alternative 4 - ERD (Bio Barriers)
$576,130.00 $1,300,147.00 $1,876,277.00 $1,313,393.90 $2,814,415.50 No Acceptable
Alternative 5 - Pump & Treat
$3,538,986.00 $9,970,356.00 $13,509,342.00 $9,456,539.40 $20,264,013.00 No Acceptable
8. State Acceptance
9. Community Acceptance
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria1. Overall Protection of Human Health and the Environment
How Alternative Provides Human Health and Environmental Protection
Alternative 1 - No Action
Existing ground water COCs in the shallow ground water periphery exist at concentrations greater than the MCLs. Ground water in the shallow periphery is a continuing source to the downgradient plume and ground water contamination is a source of vapor intrusion into residential structures. Natural attenuation mechanisms cannot meet the RAOs in a timely fashion.
Human health and the environment are not protected because ground water exceeding PRGs remains in place. Exposure to residents and construction / utility workers could occur under this alternative.
The vapor intrusion pathway remains and indoor air exceeding PRGs remains in place. Exposure to residents and workers could occur under this alternative.
Alternative 2 - Monitored Natural Attenuation (MNA)
An appropriately designed MNA program may be able to monitor the reduction of COCs until levels meet PRGs in the shallow ground water periphery at the conclusion of theremedial action. However, the period of time to achieve RAOs may be on the order of 30 years of more and over much of the course of the remedial alternative a substantialamount of the shallow ground water periphery may not meet chemical-specific ARARs. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow ground water periphery, equally or more toxic intermediary products may persist. Additionally, the extended residence of ground water exceeding PRGs in the shallow ground water periphery provides potential for additional vertical migration of contamination.
If DNAPL or sorbed soil contamination persists in the area a dissolved phase plume will persist in the aquifer and this alternative will not effectively achieve RAOs or limit residual risk. The ongoing monitoring of the remedial alternative will limit some residual risk by allowing regular evaluation of the effectiveness of the alternative.
Once the COCs are remediated in the ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time. However, the time periods to achieve COC reduction in the shallow ground water periphery itself and then subsequent COC reduction in the remaining downgradient plume may not be acceptable.
Alternative 3 - Zero-Valent Iron PRB
Appropriately designed PRB walls should be able to remediate dissolved phase ground water contamination to meet PRGs in the shallow ground water periphery at the conclusion of the remedial action. However, since ground water remediation rates are limited by the natural ground water velocity potential for human exposure to ground water exceeding PRGs will continue for several years before achieving the RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs, this alternative will no longer effectively achieve RAOs or limit residual risk. Additionally, the extended residence of ground water exceeding PRGs in the shallow ground water periphery provides potential for additional vertical migration of contamination.
Once the COCs are remediated in the ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time. However, the time periods to achieve COC reduction in the shallow ground water periphery with the use of PRBs and then subsequent COC reduction in the remaining downgradient plume may not be acceptable.
Alternative 4 - ERD (Bio Barriers)
Appropriately designed ERD bio barriers may result in the removal of COCs within the shallow ground water periphery to achieve PRGs. Shallow contaminated ground water will be treated to PRGs if adequate and complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved forall COCs, in all areas of the shallow ground water periphery, equally or more toxic intermediary products may persist. If DNAPL or sorbed soil contamination persists following completion ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated in the shallow ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Alternative 5 - Pump & Treat
An appropriately designed pump and treat system will result in the removal of COCs within the shallow ground water periphery however remediation may take in excess of 40 years to achieve PRGs. If DNAPL or sorbed soil contamination is present a dissolved phase plume will persist or rebound in the aquifer and this alternative may not achieve RAOs or limit residual risk within an acceptable time period.
Once the COCs are remediated at the source, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Once the COCs are remediated in the shallow ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria2. Compliance with ARARs
a. Compliance with Chemical-Specific ARARs
b. Compliance with Action-Specific ARARs
c. Compliance with Location Specific ARARs
Alternative 1 - No Action
Does not comply with chemical-specific ARARs for ground water or indoor air.
The proposed alternative will have not action so action-specific ARARs will not apply.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 2 - Monitored Natural Attenuation (MNA)
Ground water at a designated downgradient point of compliance is expected to meet chemical-specific ARARs over time, although the period of time may be on the order of 30 years of more. Additionally, over much of the course of the remedial alternative a substantial amount of the shallow ground water periphery upgradient of the point of compliance may not meet chemical-specific ARARs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 3 - Zero-Valent Iron PRB
The shallow ground water plume core and hot spot area is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 4 - ERD (Bio Barriers)
The shallow ground water periphery is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 5 - Pump & Treat
The shallow ground water plume periphery is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to 20 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria3. Long Term Effectiveness and Permanence
a. Magnitude of Residual Risk
Alternative 1 - No Action
Source of both ground water and vapor intrusion impacts is not removed under this alternative. Significant residual risk remains.
Alternative 2 - Monitored Natural Attenuation (MNA)
MNA of the shallow ground water periphery can be expected to meet long term PRGs and RAOs and therefore eventually reduce residual risk. However, given the passive nature of the alternative high concentrations of COCs will persist in the shallow ground water periphery for an extended period of time presenting continuing residual risk. If DNAPL or sorbed soil contamination persists in the area a dissolved phase plume will persist in the aquifer and this alternative will not effectively achieve RAOs or limitresidual risk. The ongoing monitoring of the remedial alternative will limit some residual risk by allowing regular evaluation of the effectiveness of the alternative.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 3 - Zero-Valent Iron PRB
PRBs designed for site-specific dissolved phase ground water plume conditions will achieve long term PRGs and RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs, this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 4 - ERD (Bio Barriers)
The shallow ground water periphery treatment via ERD bio barriers can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative.
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 5 - Pump & Treat
Shallow ground water periphery treatment via pump and treat methods can be designed to meet long term PRGs and RAOS and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination is present, pump and treat technology in low permeability GCSP site sediments may take greater than 40 years to achieve RAOs. Additionally, portions of the aquifer that have been partially remediated may be subject to recontamination or rebound from remaining sorbed of DNAPL contaminant sources. Residual risk may remain within the aquifer greater than 20-ft bgs since this zone is not actively treated by this alternative
If upgradient source treatment is not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria3. Long Term Effectiveness and Permanence
b. Adequacy and Reliability of Controls
Alternative 1 - No Action
No controls implemented.
Alternative 2 - Monitored Natural Attenuation (MNA)
No specific controls or components are installed as part of this alternative. Given appropriate site conditions, MNA can be a reliable method (reductive dechlorination of site COCs) of reaching RAOs over long time periods.
Alternative 3 - Zero-Valent Iron PRB
The long-term effectiveness of PRBs will decrease over time as the reactive material in the PRBs degrades. The ZVI-PRB walls have been designed for a 20-year service life, and will require replacement at 20 years since RAOs are not expected to be met for 40 years. The effectiveness of the PRB walls is dependant upon a thorough understanding of the hydraulic flow conditions within the aquifer and, if not properly designed or installed, bypass of ground water around, below, or above the barrier can occur. During installation, the smearing of clays on the trench-wall face can limit the permeability of the barrier, as can fouling over time within the ZVI wall.
If untreated dissolved phase contamination persists, or DNAPL source material remains, beyond the service life of the PRBs, re-installation of the PRBs may be required.
Alternative 4 - ERD (Bio Barriers)
Injected carbon-source amendments have limited residence time in the aquifer. Materials are consumed and will require multiple injection events. ERD has been proven a reliable method of treating the COCs, but requires injection of amendments into the subsurface which can be difficult to control. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the conclusion of the carbon-source amendment injections, additional injection of materials may be required.
Alternative 5 - Pump & Treat
Damage, fouling, or loss of specific capacity of pump and treat system extraction and injection wells may require replacement of these components over the extended operational period of this alternative. Based on site-specific geochemical conditions, extracted ground water may requireaddition of conditioning chemicals to modify pH or other factors which may degrade system components more rapidly and necessitate replacement. Significant failures of equipment during treatment may require the cessation of treatment while repairs are conducted.
If untreated dissolved phase contamination persists, or DNAPL source material remains after the conclusion of the anticipated pump and treat remedial period, continued operation of the system may be required for a very long additional time.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria4. Reduction of Toxicity, Mobility, and Volume Through Treatment
a. Treatment Process Used and Materials Treated
b. Amount of Hazardous Materials Destroyed or Treated
c. Degree of Expected Reductions in Toxicity, Mobility,
Alternative 1 - No Action
Not applicable. Not applicable. Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
Treatment of VOC COCs occurs via biologically-mediated reductive dechlorination.
Site-specific MNA parameter data will need to be collected in order to calculate the projected quantity and rate of PCE (and other chlorinated VOCs) degradation through natural attenuation.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow ground water periphery, equally or more toxic intermediary products may persist.
Alternative 3 - Zero-Valent Iron PRB
Treatment of VOC COCs occurs via reductive dechlorination as ground water passes through the PRBs by natural ground water flow.
Bench-scale testing will provide information on the specific volumeof PCE (and other chlorinated VOCs) treated by passing throughthe PRBs.
Using site-specific data PRBs will be designed to meet PRGs on the discharge side of the treatment walls.
Alternative 4 - ERD (Bio Barriers)
Treatment of VOC COCs occurs via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Pilot-scale testing will provide information on the specific volumeof PCE (and other chlorinated VOCs) that will be expected to be treated by ERD bio barriers.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow ground water periphery, equally or more toxic intermediary products may persist.
Alternative 5 - Pump & Treat
COCs are stripped (volatilized) from ground water. The vapor stream is recovered and volatile components are further treated by passage through GAC. The final polished offgas stream is discharged to the atmosphere. The final remediated ground water stream is re-injected into the aquifer. The COCs at the site are generally amenable to treatment via air stripping.
Pilot-scale testing will provide information on the specific volumeof PCE (and other chlorinated VOCs) that will be expected to be treated by the pump and treat alternative.
Using site-specific data a pump and treat system will be designed to reduce ground water concentrations to PRGs prior to reinjection.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria4. Reduction of Toxicity, Mobility, and Volume Through Treatment
d. Degree to Which Treatment is Irreversible e. Type of Residuals Remaining After Treatment
Alternative 1 - No Action
Not applicable. Original COCs would remain as residuals since no treatment occurs.
Alternative 2 - Monitored Natural Attenuation (MNA)
If able to fully proceed, this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, andchloride via reductive dechlorination over time.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride.
Alternative 3 - Zero-Valent Iron PRB
Treatment will permanently reductively dechlorinate the COCs.
Residuals following reductive dechlorination of the PCE will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. Additionally, the emplaced ZVI will remain in the subsurface.
Alternative 4 - ERD (Bio Barriers)
If able to fully proceed, this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, andchloride via reductive dechlorination over time.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. A limited residual amount of the carbon-amendment substratemay persist in the aquifer materials.
Alternative 5 - Pump & Treat
Removal of COCs from the ground water is generally irreversible with an appropriately designed air stripper treatment system.
Residuals following pump and treat implementation include GAC that will require offsite disposal or recycling and remediated ground water that will require re-injection.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria5. Short Term Effectiveness
a. Protection of Community During Remedial Actions b. Protection of Workers During Remedial Actions
Alternative 1 - No Action
Since no action would take place there would be no impacts to the community from implementation of this alternative. Original risks to the community from COCs would remain.
No remedial action would be implemented.
Alternative 2 - Monitored Natural Attenuation (MNA)
No remedial actions would take place so there would be limited impacts to the community from implementation of this alternative. Installation of ground water monitoring wells and regular sampling would have limited impacts on the community. Air monitoring would need to performed during intrusive activities. Given the passive nature of the alternative high concentrations of COCs may persist in the shallow ground water periphery for an extended period of timeand may present an unacceptable ongoing risk to the community.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 3 - Zero-Valent Iron PRB
Air monitoring would need to performed during intrusive activities such as excavation and PRB installation. Large open trenches will be excavated in residential areas and pose a threat to the community. Significant traffic disruption would also occur.
Installation of the PRBs will likely generate hazardous waste for offsite treatment and disposal during excavation of soil for ZVI placement. Due to the shallow ground water table it is likely that some highly contaminated ground water may also be generated during some of the trenching activities which will require containment and treatment or disposal.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 4 - ERD (Bio Barriers)
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 5 - Pump & Treat
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Additionally, air monitoring or modeling will need to performed to demonstrate protection of the community from unacceptable air emissions from the air stripper.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria5. Short Term Effectiveness
b. Protection of Workers During Remedial Actions
c. Environmental Impacts d. Time Until Remedial Action Objectives are Achieved
Alternative 1 - No Action
No remedial action would be implemented.
Ground water and indoor air at concentrations greater than PRGs would remain. There would be no other alternative specific environmental impacts since no remedial action occurs.
RAOs would not be achieved.
Alternative 2 - Monitored Natural Attenuation (MNA)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Given the passive nature of the alternative high concentrations of COCs may persist in the shallow ground water periphery for an extended period of time and may present an unacceptable risk to the environment.
Ground water at a designated downgradient pointof compliance is not expected to meet chemical-specific ARARs for a period of probably 40 years of more. If full reductive dechlorination is not achieved for all COCs, in all areas of the shallow ground water periphery, RAOs may not be met bythis alternative.
Alternative 3 - Zero-Valent Iron PRB
Generation of highly contaminated ground water may pose a threat to site workers. Risk can be managed through appropriate health and safety monitoring and waste handling practices.
Offsite transport and disposal of hazardous materials may pose a threat to the environment. Risk can be managed through appropriate hazardous waste handling and practices.
Due to the passive nature of this alternative, the treatment rate of the shallow ground water periphery will be limited by the ground water flow velocity. Assuming a continuing dissolved COC plume is not propagated by DNAPL or sorbed soilCOCs that remain between the PRB wall transects the RAOs for the shallow ground water periphery could be met within a period of four to five pore volume flushings. Due to the greater distances over which fewer PRB walls would be placed to address the larger shallow ground water periphery area, RAOs are estimated to be met by this alternative in roughly 20 to 25 years.
Alternative 4 - ERD (Bio Barriers)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
A total of 16 carbon-source amendment injections at a frequency of once every 15 monthsare anticipated although RAOs will still not be achieved following the final injection. RAOs are expected to be achieved within two years following the final carbon-source amendment injection or at roughly 20 years.
Alternative 5 - Pump & Treat
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
If appropriate air emissions treatment is implemented and successful ground water reinjection can be achieved no environmental impacts are anticipated.
Due to the low hydraulic conductivity of the geologic materials at the site, the pump and treat alternative is anticipated to take over 40 years to achieve RAOs
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria6. Implementability
a. Ability to Construct and Operate the Technology b. Reliability of the Technology c. Ease of Undertaking Additional Remedial Actions, if Necessary
Alternative 1 - No Action
Not applicable. Not applicable. Since this alternative involves no action it would provide no obstructions to other future action.
Alternative 2 - Monitored Natural Attenuation (MNA)
No specific construction related to this alternative would be required. Standard monitoring wells are easily constructable and have no operational requirements.
Since this alternative does not include active implementation of a constructed alternative there would be few limitations on reliably implementing this technology.
Other remedial actions could be easily implemented at the site. However, additional actions wouldneed to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation if this component of natural attenuation was expected to continue to operate.
Alternative 3 - Zero-Valent Iron PRB
Construction of PRB walls is similar to, but somewhat more complicated than, traditional trenching. Slurry trenching uses traditional equipment but requires maintenance of the slurry during construction. Single-pass trenching can also be used, but involves specialized equipment. PRB walls have been routinely installed at similar sites over the last ten years.
PRBs can be reliably designed and installed once site specific data collection and bench testing are complete. The reliability of implementing this technology can be impacted by lack of site-specific geologic, geochemical, and contaminant distribution data.
Other additional remedial actions would be relatively easy to implement at the site. Other remedial actions may be limited in application of certain technologies near the PRB walls which could damage or reduce the effectiveness of the walls.
Alternative 4 - ERD (Bio Barriers)
Carbon-source amendment treatments require specialized equipment which is readily available through numerous direct-push drilling vendors. Direct-push drilling is an easily operated technology. Carbon-source amendments (i.e. emulsified vegetable oil) are readily available.
ERD is a reliable technology as it is relatively easy to implement. The technology is less reliable as to how rapidly amendments can be injected into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other remedial actions could be implemented at the site. However, additional actions wouldneed to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation.
Alternative 5 - Pump & Treat
Pump and treat alternatives utilize routine, available well installation techniques and materials and basic air stripping systems. However, site-specific geochemical conditions can present substantial challenges in bringing a successfully operating extraction, treatment, and reinjection system online. Additionally, although ground water re-injection utilizes basic well installation techniques and technology the process is subject to high operational and maintenance requirements.
Pump and treat is reliable technology as it is relatively easy to implement and uses basic ground water extraction well and technologically sound air stripping principals. However, as an operating treatment plan system it is subject to mechanical failures.
Other remedial actions could be implemented at the site. However, additional actions wouldneed to take into account aquifer amendments that might be recovered by the pump and treat system and foul the system or reduce the effectiveness of the air stripping process.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria6. Implementability
d. Ability to Monitor Effectiveness of Remedy
e. Ability to Obtain Approvals from Other Agencies
f. Availability of Offsite Treatment, Storage, and Disposal Services and
Alternative 1 - No Action
No actions and no continued monitoring would be undertaken.
Since no actions would be taken there would be no approvals or coordination with another agencies for implementation of this alternative. However, it may be difficult to gain approval from other stakeholder agencies for no action to meet RAOs.
Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
Ground water monitoring wells can be readily installed to track the performance of this alternative.
This alternative will require access to public and private property to install monitoring wells. This will require approval or authorization from owners/agencies. The extended time period over which it will take MNA to address ground water exceeding PRGs may not be acceptable to some stakeholder agencies.
No substantial offsite treatment, storage, and disposal services are required for this alternative. Limited amounts of ground water monitoring well purge water would be generated that would require coordination for treatment or offsite disposal.
Alternative 3 - Zero-Valent Iron PRB
Ground water monitoring wells can readily track the performance of this alternative as it pertains to remediation of the shallow ground water periphery.
The installation and use of PRB walls in themselves are not anticipated to provide particular difficulties in gaining stakeholder agency approval. The extended time period over which it will take PRB walls to address ground waterexceeding PRGs may not be acceptable to some stakeholder agencies. The relatively large scale construction aspect of installing PRBs may require extensive coordination with local agencies and utilities.
Material excavated during the installation of the PRB walls may generate hazardous waste which may require the selection of an offsite RCRA landfill disposal location. The volume of hazardous material generated will depend on the final designed size of the PRBs and where they would be installed at the site. The nature of the hazardous material generated and the potential treatment and disposal options will require additional site specific data and design considerations.
Alternative 4 - ERD (Bio Barriers)
Ground water monitoring wells can be readily installed to track the performance of this alternative.
This alternative will require access to public and private property and approval to inject ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Alternative 5 - Pump & Treat
Ground water monitoring wells can be readily installed to track the performance of this alternative.
This alternative will require access to public and private property, approval to reinject treated ground water, and approvals to discharge the treated air stream. This will require approval or authorization from owners/agencies.
Offsite recycling of GAC is readily available. Treated ground water will be reinjected back into the aquifer. The availability of reinjection is not limited, however, the technical viability of reinjection can be challenging. If offsite disposal of treated ground water was required an appropriate disposal option would need to be identified.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria6. Implementability
f. Availability of Offsite Treatment, Storage, and Disposal Services and
g. Availability of Necessary Equipment and Specialists
h. Availability of Prospective Technologies
Alternative 1 - No Action
Not applicable. Not applicable. Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
No substantial offsite treatment, storage, and disposal services not required for this alternative. Limited amounts of ground water monitoring well purge water would be generated that would require coordination for treatment or offsite disposal.
Drilling contractors for well installation are available for hire with the appropriate equipment and personnel to accomplish the monitoring well installation tasks for this alternative. These technologies are not specialized, therefore there are various vendors from which to chose.
MNA is an available technology which iseasily implemented.
Alternative 3 - Zero-Valent Iron PRB
Some highly contaminated ground wateris likely to be generated during trenching activities due to the shallow ground water table. Contaminated water will need to be contained and potentially treated onsite or possibly discharged to the City POTW. The potential volume of ground water generated and the contaminant concentrations of that ground water and potential treatment and disposal options require additional site specific data and design considerations.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
Installation of PRB walls is an available technology, having greatly expanded over the last ten years. This technology requires bench-scale testing to determine the ideal reactive media to use within the wall, the amount of reactive material required to treat site contaminants, and the thickness of material required to meet the PRGs.
Alternative 4 - ERD (Bio Barriers)
Offsite treatment, storage, and disposal services not required for this alternative.
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ERD is a readily available technology but requires some level of pilot-scale testing to confirm carbon-source dosing,injection spacing, and other final remedy requirements.
Alternative 5 - Pump & Treat
Offsite recycling of GAC is readily available. Treated ground water will be reinjected back into the aquifer. The availability of reinjection is not limited, however, the technical viability of reinjection can be challenging. If offsite disposal of treated ground water was required an appropriate disposal option would need to be identified.
Drilling contractors for well installation and air stripper treatment vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. These technologies are not specialized, therefore there are various vendors from which to chose.
Pump and treat systems are readily available technologies but require some level of pilot-scale testing to design final remedy requirements.
Remedial Alternative
Table 17Comparison of Remedial Alternatives
Shallow Ground Water Periphery
Evaluation Criteria7. Cost
a. Capital Costs b. Operating and
c. Present Worth Cost
Lower Range Cost (-30%)
Upper Range Cost (+50%)
Alternative 1 - No Action
$0 $0 $0.00 $0.00 $0.00 No Not Acceptable
Alternative 2 - Monitored Natural Attenuation (MNA)
$268,878.00 $1,632,212.00 $1,901,090.00 $1,330,763.00 $2,851,635.00 No Acceptable
Alternative 3 - Zero-Valent Iron PRB
$12,998,556.00 $926,966.00 $13,925,522.00 $9,747,865.40 $20,888,283.00 No Acceptable
Alternative 4 - ERD (Bio Barriers)
$921,191.00 $2,352,052.00 $3,273,243.00 $2,291,270.10 $4,909,864.50 Yes Acceptable
Alternative 5 - Pump & Treat
$3,948,021.00 $9,970,356.00 $13,136,371.00 $9,195,459.70 $19,704,556.50 No Acceptable
8. State Acceptance
9. Community Acceptance
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria1. Overall Protection of Human Health and the Environment
How Alternative Provides Human Health and Environmental Protection
Alternative 1 - No Action
Existing ground water COCs in the deeper ground water periphery up to 80-ft bgs exist at concentrations greater than the MCLs. Ground water contamination in this zone is a continuing source to the downgradient plume and ground water contamination is a source of vapor intrusion into residential structures. Natural attenuation mechanisms cannot meet the RAOs in a timely fashion.
Human health and the environment are not protected because ground water exceeding PRGs remains in place. Exposure to residents and construction / utility workers could occur under this alternative.
The vapor intrusion pathway remains and indoor air exceeding PRGs remains in place. Exposure to residents and workers could occur under this alternative.
Alternative 2 - Monitored Natural Attenuation (MNA)
An appropriately designed MNA program may be able to monitor the reduction of COCs until levels meet PRGs in the deeper ground water periphery up to 80 ft bgs at the conclusion of the remedial action. However, the period of time to achieve RAOs may be on the order of 30 years of more and over much of the course of the remedial alternative a substantial amount of round water may not meet chemical-specific ARARs. If full reductive dechlorination is not achieved for all COCs, in all areas of the deeper ground water periphery, equally or more toxic intermediary products may persist. Additionally, the extended residence of ground water exceeding PRGs provides potential for additional vertical migration of contamination to the drinking water aquifer.
If DNAPL or sorbed soil contamination persists in the area a dissolved phase plume will persist in the aquifer and this alternative will not effectively achieve RAOs or limit residual risk. The ongoing monitoring of the remedial alternative will limit some residual risk by allowing regular evaluation of the effectiveness of the alternative.
Once the COCs are remediated in the ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time. However, the time periods to achieve COC reduction in the shallow ground water periphery itself and then subsequent COC reduction in the remaining downgradient plume may not be acceptable.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
Appropriately designed PRB walls, supplemented with ERD to achieve greater remediation depths, should be able to remediate dissolved phase ground water contamination to meet PRGs in the deeper ground water periphery at the conclusion of the remedial action. However, since ground water remediation rates for PRBs are limited by the natural ground water velocity potential for human exposure to ground water exceeding PRGs will continue for several years before achieving the RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs or ERD zones and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs or the ERD carbon-source amendments, this alternative will no longer effectively achieve RAOs or limit residual risk. Additionally, the extended residence of ground water exceeding PRGs in the deeper ground water periphery provides potential for additional vertical migration of contamination.
Once the COCs are remediated in the deeper ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Alternative 4 - ERD (Bio Barriers)
Appropriately designed ERD bio barriers may result in the removal of COCs within the deeper ground water periphery at depths of up to 80 ft bgs to achieve PRGs. Contaminated ground water will be treated to PRGs if adequate and complete biologically mediated reductive dechlorination can be achieved. If full reductive dechlorination is not achieved for all COCs, in all areas of the deeper ground water periphery up to 80 ft bgs, equally or more toxic intermediary products may persist. If DNAPL or sorbed soil contamination persists following completion ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk.
Once the COCs are remediated in the deeper ground water periphery, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Alternative 5 - Pump & Treat
An appropriately designed pump and treat system will result in the removal of COCs within the deeper ground water periphery, at depths of up to 80 ft bgs, however remediation may take in excess of 40 years to achieve PRGs. If DNAPL or sorbed soil contamination is present a dissolved phase plume will persist or rebound in the aquifer and this alternative may not achieve RAOs or limit residual risk within an acceptable time period.
Once the COCs are remediated in the deeper ground water periphery zone, downgradient ground water concentrations and resulting risk are expected to decrease over time.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria2. Compliance with ARARs
a. Compliance with Chemical-Specific ARARs
b. Compliance with Action-Specific ARARs
c. Compliance with Location Specific ARARs
Alternative 1 - No Action
Does not comply with chemical-specific ARARs for ground water or indoor air.
The proposed alternative will have not action so action-specific ARARs will not apply.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 2 - Monitored Natural Attenuation (MNA)
Ground water at a designated downgradient point of compliance is expected to meet chemical-specific ARARs over time, although the period of time may be on the order of 30 years of more. Additionally, throughout much of the remedial alternative period a portion of the ground water upgradient of the point of compliance and up to depths of 80-ft bgs may not meet chemical-specific ARARs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
The deeper ground water periphery is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to up to 80 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 4 - ERD (Bio Barriers)
The deeper ground water periphery is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to up to 80 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Alternative 5 - Pump & Treat
The deeper ground water periphery is expected to meet chemical-specific ARARs upon completion of the alternative. The depth of treatment is to up to 80 ft bgs.
The alternative will meet action-specific ARARs during the implementation of the alternative.
Not applicable - no location-specific ARARs have been identified for the GCSP site.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria3. Long Term Effectiveness and Permanence
a. Magnitude of Residual Risk
Alternative 1 - No Action
Source of both ground water and vapor intrusion impacts is not removed under this alternative. Significant residual risk remains.
Alternative 2 - Monitored Natural Attenuation (MNA)
MNA of the deeper ground water up to 80 ft bgs can be expected to meet long term PRGs and RAOs and therefore eventually reduce residual risk. However, given the passive nature of the alternative concentrations of COCs that do not meet PRGs will persist up to 80 ft bgs at least for an extended period of time presenting continuing residual risk. If DNAPL or sorbed soil contamination persists in the area a dissolved phase plume will persist in the aquifer and this alternative will not effectively achieve RAOs or limit residual risk. The ongoing monitoring of the remedial alternative will limit some residual risk by allowing regular evaluation of the effectiveness of the alternative.
If upgradient source treatment and shallower zone aquifer treatment are not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
PRBs, along with supplemental ERD bio barriers, designed for site-specific dissolved phase ground water plume conditions will achieve long term PRGs and RAOs. If DNAPL or sorbed soil contamination persists in the areas between the PRBs or bio barriers and continues to propagate a dissolved phase plume beyond the designed service life of the PRBs, this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer at depths greater than 80-ft bgs since this zone is not actively treated by this alternative.
If upgradient source treatment and shallower zone aquifer treatment are not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 4 - ERD (Bio Barriers)
The deeper ground water periphery treatment via ERD bio barriers can be designed to meet long term PRGs and RAOs and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination persists following completion of ERD amendment injections a dissolved phase plume will persist or rebound in the aquifer and this alternative will no longer effectively achieve RAOs or limit residual risk. Residual risk may remain within the aquifer at depths greater than 80-ft bgs since this zone is not actively treated by this alternative.
If upgradient source treatment and shallower zone aquifer treatment are not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Alternative 5 - Pump & Treat
Deeper ground water periphery treatment, up to 80 ft bgs, via pump and treat methods can be designed to meet long term PRGs and RAOS and therefore eventually reduce residual risk. If DNAPL or sorbed soil contamination is present, pump and treat technology in low permeability GCSP site sediments may take greater than 40 years to achieve RAOs. Additionally, portions of the aquifer that have been partially remediated may be subject to recontamination or rebound from remaining sorbed of DNAPL contaminant sources. Residual risk may remain within the aquifer greater than 80-ft bgs since this zone is not actively treated by this alternative.
If upgradient source treatment and shallower zone aquifer treatment are not implemented this alternative may not successfully achieve RAOs for the shallow ground water plume core and hot spot.
A 5-year review will be required to assess performance of this alternative and evaluate whether RAOs are being met.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria3. Long Term Effectiveness and Permanence
b. Adequacy and Reliability of Controls
Alternative 1 - No Action
No controls implemented.
Alternative 2 - Monitored Natural Attenuation (MNA)
No specific controls or components are installed as part of this alternative. Given appropriate site conditions, MNA can be a reliable method (reductive dechlorination of site COCs) of reaching RAOs over long time periods.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
The long-term effectiveness of PRBs will decrease over time as the reactive material in the PRBs degrades. The ZVI-PRB walls have been designed for a 20-year service life, and will require replacement at 20 years since RAOs are not expected to be met for 40 years. The effectiveness of the PRB walls is dependant upon a thorough understanding of the hydraulic flow conditions within the aquifer and, if not properly designed or installed, bypass of ground water around, below, or above the barrier can occur. Injected carbon-source amendments have limited residence time in the aquifer. Materials are consumed and will require multiple injection events. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants. During installation, the smearing of clays on the trench-wall face can limit the permeability of the barrier, as can fouling over time within the ZVI wall.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the end of the service life of the PRBs or following the final carbon-source amendment injections, reinstallation of the PRBs or additional injection of materials may be required.
Alternative 4 - ERD (Bio Barriers)
Injected carbon-source amendments have limited residence time in the aquifer. Materials are consumed and will require multiple injection events. ERD has been proven a reliable method of treating the COCs, but requires injection of amendments into the subsurface which can be difficult to control. Ineffective distribution of ISCO or ERD amendments can lead to untreated DNAPL or residual sorbed-phase contaminants.
If untreated dissolved phase contamination persists, or DNAPL source material remains, after the conclusion of the carbon-source amendment injections, additional injection of materials may be required.
Alternative 5 - Pump & Treat
Damage, fouling, or loss of specific capacity of pump and treat system extraction and injection wells may require replacement of these components over the extended operational period of this alternative. Based on site-specific geochemical conditions, extracted ground water may require addition of conditioning chemicals to modify pH or other factors which may degrade system components more rapidly and necessitate replacement. Significant failures of equipment during treatment may require the cessation of treatment while repairs are conducted.
If untreated dissolved phase contamination persists, or DNAPL source material remains after the conclusion of the anticipated pump and treat remedial period, continued operation of the system may be required for a very long additional time.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria4. Reduction of Toxicity, Mobility, and Volume Through Treatment
a. Treatment Process Used and Materials Treated
b. Amount of Hazardous Materials Destroyed or Treated
c. Degree of Expected Reductions in Toxicity, Mobility, and Volume
Alternative 1 - No Action
Not applicable. Not applicable. Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
Treatment of VOC COCs occurs via biologically-mediated reductive dechlorination.
Site-specific MNA parameter data will need to be collected in order to calculate the projected quantity and rate of PCE (and other chlorinated VOCs) degradation through natural attenuation.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the deeper ground water periphery, equally or more toxic intermediary products may persist.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
PRB treatment of VOC COCs occurs via reductive dechlorination as ground water passes through the PRBs by natural ground water flow. Bio barrier treatment of VOC COCs occurs via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Bench-scale and pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) treated by passing through the PRBs.
Using site-specific data PRBs will be designed to meet PRGs on the discharge side of the PRB treatment walls. If sustained biologically mediated reductive dechlorination can be achieved substantial reductions will also be expected for the bio barriers. If full reductive dechlorination is not achieved within the bio barriers for all COCs, in all areas of the deeper ground water periphery, equally or more toxic intermediary products may persist.
Alternative 4 - ERD (Bio Barriers)
Treatment of VOC COCs occurs via biologically-mediated reductive dechlorination which is enhanced through carbon-source amendments into the aquifer matrix.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by ERD bio barriers.
If sustained biologically mediated reductive dechlorination can be achieved substantial reductions are expected. If full reductive dechlorination is not achieved for all COCs, in all areas of the deeper ground water periphery, equally or more toxic intermediary products may persist.
Alternative 5 - Pump & Treat
COCs are stripped (volatilized) from ground water. The vapor stream is recovered and volatile components are further treated by passage through GAC. The final polished offgas stream is discharged to the atmosphere. The final remediated ground water stream is re-injected into the aquifer. The COCs at the site are generally amenable to treatment via air stripping.
Pilot-scale testing will provide information on the specific volume of PCE (and other chlorinated VOCs) that will be expected to be treated by the pump and treat alternative.
Using site-specific data a pump and treat system will be designed to reduce ground water concentrations to PRGs prior to re-injection.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria4. Reduction of Toxicity, Mobility, and Volume Through Treatment
d. Degree to Which Treatment is Irreversible e. Type of Residuals Remaining After Treatment
Alternative 1 - No Action
Not applicable. Original COCs would remain as residuals since no treatment occurs.
Alternative 2 - Monitored Natural Attenuation (MNA)
If able to fully proceed, this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via reductive dechlorination over time.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
PRB treatment will permanently reductively dechlorinate the COCs. If able to fully proceed, ERD will also ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via reductive dechlorination over time.
Residuals following reductive dechlorination of the PCE will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. Additionally, the emplaced ZVI will remain in the subsurface and limited residual amount of the carbon-amendment substrate may also persist in the aquifer materials..
Alternative 4 - ERD (Bio Barriers)
If able to fully proceed, this alternative will ultimately permanently mineralize COCs to carbon dioxide, water, and chloride via reductive dechlorination over time.
Residuals following reductive dechlorination of PCE following ERD will proceed through TCE, DCE, VC, ethene, and ultimately carbon dioxide, water, and chloride. A limited residual amount of the carbon-amendment substrate may persist in the aquifer materials.
Alternative 5 - Pump & Treat
Removal of COCs from the ground water is generally irreversible with an appropriately designed air stripper treatment system.
Residuals following pump and treat implementation include GAC that will require offsite disposal or recycling and remediated ground water that will require re-injection.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria5. Short Term Effectiveness
a. Protection of Community During Remedial Actions b. Protection of Workers During Remedial Actions
Alternative 1 - No Action
Since no action would take place there would be no impacts to the community from implementation of this alternative. Original risks to the community from COCs would remain.
No remedial action would be implemented.
Alternative 2 - Monitored Natural Attenuation (MNA)
No remedial actions would take place so there would be limited impacts to the community from implementation of this alternative. Installation of ground water monitoring wells and regular sampling would have limited impacts on the community. Air monitoring would need to performed during intrusive activities. Given the passive nature of the alternative high concentrations of COCs may persist in the shallow ground water periphery for an extended period of time and may present an unacceptable ongoing risk to the community.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
Air monitoring would need to performed during intrusive activities such as excavation, PRB installation and drilling and installation of ERD infrastructure. Large open trenches will be excavated in residential areas and pose a threat to the community. Significant traffic disruption would also occur.
Installation of the PRBs will likely generate hazardous waste for offsite treatment and disposal during excavation of soil for ZVI placement. Due to the shallow ground water table it is likely that some highly contaminated ground water may also be generated during some of the trenching activities which will require containment and treatment or disposal.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 4 - ERD (Bio Barriers)
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Alternative 5 - Pump & Treat
Air monitoring would need to performed during intrusive activities such as drilling or installation of supporting infrastructure.
Additionally, air monitoring or modeling will need to performed to demonstrate protection of the community from unacceptable air emissions from the air stripper.
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria5. Short Term Effectiveness
b. Protection of Workers During Remedial Actions
c. Environmental Impacts d. Time Until Remedial Action Objectives are Achieved
Alternative 1 - No Action
No remedial action would be implemented.
Ground water and indoor air at concentrations greater than PRGs would remain. There would be no other alternative specific environmental impacts since no remedial action occurs.
RAOs would not be achieved.
Alternative 2 - Monitored Natural Attenuation (MNA)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
Given the passive nature of the alternative concentrations of COCs greater than PRGs may persist in the deeper ground water periphery for an extended period of time and may present an unacceptable risk to the environment.
Ground water at a designated downgradient point of compliance is not expected to meet chemical-specific ARARs for a period of probably 40 years of more. If full reductive dechlorination is not achieved for all COCs, in all areas of the deeper ground water periphery RAOs may not be met by this alternative.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
Generation of highly contaminated ground water may pose a threat to site workers. Risk can be managed through appropriate health and safety monitoring and waste handling practices.
Offsite transport and disposal of hazardous materials generated during PRB installation may pose a threat to the environment. Risk can be managed through appropriate hazardous waste handling and practices. No environmental impacts from installation of the bio barriers are anticipated.
Due to the passive nature of this alternative, the treatment rate of the shallow ground water periphery will be limited by the ground water flow velocity. Assuming a continuing dissolved COC plume is not propagated by DNAPL or sorbed soil COCs that remain between the PRB or bio barrier wall transects the RAOs for the deeper ground water periphery could be met within a period of four to six pore volume flushings. A total of 16 carbon-source amendment injections at a frequency of once every 15 months are anticipated although RAOs will still not be achieved following the final injection. Due to the greater distances over which fewer PRB/bio barrier walls would be placed to address the deeper ground water periphery area, RAOs are estimated to be met by this alternative in roughly 20 to 25 years.
Alternative 4 - ERD (Bio Barriers)
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
No environmental impacts are anticipated.
A total of 16 carbon-source amendment injections at a frequency of once every 15 months are anticipated although RAOs will still not be achieved following the final injection. RAOs are expected to be achieved within two years following the final carbon-source amendment injection or at roughly 20 years.
Alternative 5 - Pump & Treat
Intrusive onsite work may pose a threat to site workers. Risk can be managed through appropriate health and safety practices.
If appropriate air emissions treatment is implemented and successful ground water reinjection can be achieved no environmental impacts are anticipated.
Due to the low hydraulic conductivity of the geologic materials at the site, the pump and treat alternative is anticipated to take over 40 years to achieve RAOs
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria6. Implementability
a. Ability to Construct and Operate the Technology b. Reliability of the Technology
Alternative 1 - No Action
Not applicable. Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
No specific construction related to this alternative would be required. Standard monitoring wells are easily constructable and have no operational requirements.
Since this alternative does not include active implementation of a constructed alternative there would be few limitations on reliably implementing this technology.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
Construction of PRB walls is similar to, but somewhat more complicated than, traditional trenching. Slurry trenching uses traditional equipment but requires maintenance of the slurry during construction. Single-pass trenching can also be used, but involves specialized equipment. Installation of PRBs to depths of 60 ft bgs will approach the limits of constructability. Based on site specific conditions and PRB design needs installation of PRBs may not be feasible.
Carbon-source amendment treatments require specialized equipment which is readily available through numerous direct-push drilling vendors. Direct-push drilling is an easily operated technology. Carbon-source amendments (i.e. emulsified vegetable oil) are readily available.
PRBs can be reliably designed and installed once site specific data collection and bench testing are complete. The reliability of implementing this technology can be impacted by lack of site-specific geologic, geochemical, and contaminant distribution data. The PRB installation to depths that will be limits of constructability will most likely result in slow-paced field installations with a high likelihood of delays.
Alternative 4 - ERD (Bio Barriers)
Carbon-source amendment treatments require specialized equipment which is readily available through numerous direct-push drilling vendors. Direct-push drilling is an easily operated technology. Carbon-source amendments (i.e. emulsified vegetable oil) are readily available.
ERD is a reliable technology as it is relatively easy to implement. The technology is less reliable as to how rapidly amendments can be injected into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Alternative 5 - Pump & Treat
Pump and treat alternatives utilize routine, available well installation techniques and materials and basic air stripping systems. However, site-specific geochemical conditions can present substantial challenges in bringing a successfully operating extraction, treatment, and reinjection system online. Additionally, although ground water re-injection utilizes basic well installation techniques and technology the process is subject to high operational and maintenance requirements.
Pump and treat is reliable technology as it is relatively easy to implement and uses basic ground water extraction well and technologically sound air stripping principals. However, as an operating treatment plan system it is subject to mechanical failures.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria6. Implementability
b. Reliability of the Technology c. Ease of Undertaking Additional Remedial Actions, if Necessary
d. Ability to Monitor Effectiveness of Remedy
Alternative 1 - No Action
Not applicable. Since this alternative involves no action it would provide no obstructions to other future action.
No actions and no continued monitoring would be undertaken.
Alternative 2 - Monitored Natural Attenuation (MNA)
Since this alternative does not include active implementation of a constructed alternative there would be few limitations on reliably implementing this technology.
Other remedial actions could be easily implemented at the site. However, additional actions would need to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation if this component of natural attenuation was expected to continue to operate.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
ERD is a reliable technology as it is relatively easy to implement. The technology is less reliable as to how rapidly amendments can be injected into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other additional remedial actions could be implemented at the site. Other remedial actions may be limited in application of certain technologies near the PRB walls which could damage or reduce the effectiveness of the walls. Likewise, additional actions would need to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Alternative 4 - ERD (Bio Barriers)
ERD is a reliable technology as it is relatively easy to implement. The technology is less reliable as to how rapidly amendments can be injected into the subsurface and how well those amendments are distributed during and after injection. Also, the presence of significant quantities of DNAPL may impact the reliability of the alternatives to treat the COCs.
Other remedial actions could be implemented at the site. However, additional actions would need to be compatible with maintaining a reductive environment in the aquifer to promote biodegradation.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Alternative 5 - Pump & Treat
Pump and treat is reliable technology as it is relatively easy to implement and uses basic ground water extraction well and technologically sound air stripping principals. However, as an operating treatment plan system it is subject to mechanical failures.
Other remedial actions could be implemented at the site. However, additional actions would need to take into account aquifer amendments that might be recovered by the pump and treat system and foul the system or reduce the effectiveness of the air stripping process.
Ground water monitoring wells can be readily installed to track the performance of this alternative.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria6. Implementability
e. Ability to Obtain Approvals from Other Agencies f. Availability of Offsite Treatment, Storage, and Disposal Services and Capacity
Alternative 1 - No Action
Since no actions would be taken there would be no approvals or coordination with another agencies for implementation of this alternative. However, it may be difficult to gain approval from other stakeholder agencies for no action to meet RAOs.
Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
This alternative will require access to public and private property to install monitoring wells. This will require approval or authorization from owners/agencies. The extended time period over which it will take PRB walls to address ground water exceeding PRGs may not be acceptable to some stakeholder agencies.
No substantial offsite treatment, storage, and disposal services not required for this alternative. Limited amounts of ground water monitoring well purge water would be generated that would require coordination for treatment or offsite disposal.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
This alternative will require access to public and private property. The substantial undertaking to install the PRBs to the 60-ft depths may require specialized large equipment that would require coordination to remove overhead utilities, divert traffic, etc. Additionally, approval to inject ERD amendments into the subsurface would be required. This will require approval or authorization from owners/agencies.
The very large volume of material excavated during the installation of the PRB walls would require offsite disposal. Material generated would not be expected to require disposal as hazardous waste. Volumes generated for offsite disposal and an appropriate disposal location would require additional site specific data and design considerations. Offsite treatment, storage, and disposal services would not be required for the bio barrier component of this alternative.
Alternative 4 - ERD (Bio Barriers)
This alternative will require access to public and private property and approval to inject ERD amendments into the subsurface. This will require approval or authorization from owners/agencies.
Offsite treatment, storage, and disposal services not required for this alternative.
Alternative 5 - Pump & Treat
This alternative will require access to public and private property, approval to reinject treated ground water, and approvals to discharge the treated air stream. This will require approval or authorization from owners/agencies.
Offsite recycling of GAC is readily available. Treated ground water will be reinjected back into the aquifer. The availability of reinjection is not limited, however, the technical viability of reinjection can be challenging. If offsite disposal of treated ground water was required an appropriate disposal option would need to be identified.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria6. Implementability
g. Availability of Necessary Equipment and Specialists
h. Availability of Prospective Technologies
Alternative 1 - No Action
Not applicable. Not applicable.
Alternative 2 - Monitored Natural Attenuation (MNA)
Drilling contractors for well installation to hire with the appropriate equipment and personnel to accomplish the monitoring well installation tasks for this alternative. These technologies are not specialized, therefore there are various vendors from which to chose.
Not applicable.
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
Specialty vendors are available to hire for both PRB and ERD applications with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from. Installation to the PRBs to depths of 60 ft bgs would be highly specialized and a vendor capable of executing the work may not be able to be identified.
Installation of PRB walls is an available technology, having greatly expanded over the last ten years. This technology requires bench-scale testing to determine the ideal reactive media to use within the wall, the amount of reactive material required to treat site contaminants, and the thickness of material required to meet the PRGs.
ERD is a readily available technology but requires some level of pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Alternative 4 - ERD (Bio Barriers)
Specialty vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. However, it is a rather specialized technology, so there are fewer companies to choose from.
ERD is a readily available technology but requires some level of pilot-scale testing to confirm carbon-source dosing, injection spacing, and other final remedy requirements.
Alternative 5 - Pump & Treat
Drilling contractors for well installation and air stripper treatment vendors are available to hire with the appropriate equipment and specialists to accomplish this alternative. These technologies are not specialized, therefore there are various vendors from which to chose.
Pump and treat systems are readily available technologies but require some level of pilot-scale testing to design final remedy requirements.
Remedial Alternative
Table 18Comparison of Remedial Alternatives
Deeper Ground Water
Evaluation Criteria7. Cost
a. Capital Costs b. Operating and Maintenance
c. Present Worth Cost
Lower Range Cost (-30%)
Upper Range Cost (+50%)
Alternative 1 - No Action
$0 $0 $0.00 $0.00 $0.00 No Not Acceptable
Alternative 2 - Monitored Natural Attenuation (MNA)
$344,006.00 $1,692,940.00 $2,036,946.00 $1,425,862.20 $3,055,419.00 No Acceptable
Alternative 3 - Zero-Valent Iron PRB with ERD from 60 to 80-ft bgs
$24,639,667.00 $3,092,791.00 $27,732,458.00 $19,412,720.60 $41,598,687.00 No Acceptable
Alternative 4 - ERD (Bio Barriers)
$1,630,186.00 $5,592,046.00 $7,222,232.00 $5,055,562.40 $10,833,348.00 Yes Acceptable
Alternative 5 - Pump & Treat
$3,828,902.00 $9,970,356.00 $13,799,258.00 $9,659,480.60 $20,698,887.00 No Acceptable
Remedial Alternative
8. State Acceptance
9. Community Acceptance
Table 19Cost Summary for Remedial Alternatives
Remedial Action ComponentPreferred Remedy Cost
Alternative OptionNo Action Vapor Mitigation System
Indoor Air $0 381,661.00$ 381,661.00$
Alternative OptionNo Action Thermal Treatment ISCO w/ Follow-On ERD ERD (Gridded)
Source Area Treatment $0 8,018,000.00$ 9,436,000.00$ 8,446,000.00$ 8,018,000.00$
Alternative OptionNo Action ZVI PRB - Multiple
TransectsISCO w/ Follow-On ERD ERD (Bio Barriers) Pump and Treat (1)
Shallow Plume Core & Hot Spot $0 5,774,000.00$ 6,731,000.00$ 1,876,000.00$ 13,509,000.00$ 6,731,000.00$
Alternative OptionNo Action Monitored Natural
AttenuationZVI PRB - Multiple
TransectsERD (Bio Barriers) Pump and Treat (1)
Shallow Plume Periphery $0 1,901,000.00$ 13,926,000.00$ 3,273,000.00$ 13,918,000.00$ 3,273,000.00$
Alternative OptionNo Action Monitored Natural
AttenuationZVI PRB w/ Deep ERD ERD (Bio Barriers) Pump and Treat (1)
Deeper Ground Water $0 2,037,000.00$ 27,732,000.00$ 7,222,000.00$ 13,799,000.00$ 7,222,000.00$
Subtotal of Preferred Alternatives Options 25,625,661.00$
Project Management 589,730.00$ Project Planning Documents (Work Plan, Field Sampling Plan, Quality Assurance Project Plan, Health and Safety Plan) 138,668.00$ Preliminary Design Field Investigation 1,230,019.00$ Ground Water Sampling Program 1,383,910.00$ 5-Year Reviews 240,000.00$
Subtotal of Required Components 3,582,327.00$
Total Remedial Action Cost 29,207,988.00$ Notes:1) The costs shown for pump and treat are the costs to install and operate a treatment plant to address contamination only within each specific plume area (core, periphery, or deep). If a pump and treat option was selected to treat the entire site (core, periphery, and deep), a single system would be installed which would be designed to handle the combined flows. As a result a cost benefit would be derived because each media specific option would not individually incur the full capital cost associated with a pump and treat system. The cost for the combined treatment system has been estimated to be $17,132,000.
Table 20Final Cleanup Levels for Chemicals of Concern
Media: SoilSite Area: AllAvailable Use: ResidentialControls to Ensure Restricted Use (if applicable): N/A
Chemical of Concern Cleanup Level 1 Basis for Cleanup LevelRisk at Cleanup
Level 2
Tetrachloroethene 3.52 mg/kgProtection of Human
Health Cancer risk = 1 x 10-5
Trichloroethene 0.226 mg/kgProtection of Human
Health Cancer risk = 1 x 10-5
Cis-1,2-Dichloroethene d 24.9 mg/kgProtection of Human
Health Cancer risk = 1 x 10-5
Trans-1,2-Dichloroethene d 37.1 mg/kgProtection of Human
Health Cancer risk = 1 x 10-5
Vinyl chloride d 1.04a / 2.02b mg/kgProtection of Human
Health Cancer risk = 1 x 10-5
Tetrachloroethene 0.327 mg/kgProtection of Ground
Water at MCL Cancer risk = 1 x 10-6
Trichloroethene 0.327 mg/kgProtection of Ground
Water at MCL Cancer risk = 1 x 10-6
Cis-1,2-Dichloroethene d 2.18 mg/kgProtection of Ground
Water at MCL HQ=1
Trans-1,2-Dichloroethene d 3.27 mg/kgProtection of Ground
Water at MCL HQ=1
Vinyl chloride d 0.076 mg/kgProtection of Ground
Water at MCL Cancer risk = 1 x 10-6
Media: Ground WaterSite Area: AllAvailable Use: ResidentialControls to Ensure Restricted Use (if applicable): N/A
Chemical of Concern Cleanup Level Basis for Cleanup LevelRisk at Cleanup
Level 3
Tetrachloroethene 5 µg/LCompliance with Federal or
State ARARs Cancer risk = 1 x 10-6
Trichloroethene 5 µg/LCompliance with Federal or
State ARARs Cancer risk = 1 x 10-6
Cis-1,2-Dichloroethene 70 µg/LCompliance with Federal or
State ARARs HQ=1
Trans-1,2-Dichloroethene 100 µg/LCompliance with Federal or
State ARARs HQ=1
Vinyl chloride 1 µg/LCompliance with Federal or
State ARARs Cancer risk = 1 x 10-6
Bromoform 80 µg/LCompliance with Federal or
State ARARs Cancer risk = 1 x 10-6
Table 20Final Cleanup Levels for Chemicals of Concern
Media: Indoor Air (Vapor Intrusion)Site Area: AllAvailable Use: Residential
Controls to Ensure Restricted Use (if applicable): N/A
Chemical of Concern Cleanup Level Basis for Cleanup LevelRisk at Cleanup
Level 4
Tetrachloroethene 3.2 µg/m3Protection of Human
Health Cancer risk = 1 x 10-5
Trichloroethene c 12.2 µg/m3 Protection of Human
Health Cancer risk = 1 x 10-5
Cis-1,2-Dichloroethene d 35 µg/m3Protection of Human
Health HQ=1
Vinyl chloride d 1.1 µg/m3Protection of Human
Health Cancer risk = 1 x 10-6
Key
1. Cleanup levels will be to the most stringent standard when there is more than one basis of cleanup.
mg/kg: milligram per kilogramµg/L: microgram per literµg/m3: microgram per cubic meterARARs: Applicable or Relevant and Appropriate RequirementsMCL: Maximum Contaminant LevelHQ: Hazard Quotient
Cleanup Levels for Chemicals of Concern
2. Cleanup levels and residual risk information presented for soil are based on the risk associated with exposure to soil contamination through dermal contact by future on-site residents (lifetime).3. Cleanup levels and residual risk information presented for ground water are based on the risk associated with ingestion of contaminated ground water.4. Cleanup levels and residual risk information presented for indoor air are based on the risk associated with inhalation of contaminated air.a: Cleanup level for child exposure.
The purpose of this response action is to minimize migration of contaminants to ground water and to control risks posed by direct contact with soil and ground water and inhalation of indoor air. The results of the baseline risk assessment indicate that existing conditions at the site pose an excess lifetime cancer risk (ELCR) of 2x10-6 for a future resident's exposure to ground water, an ELCR of 1x10-6 for a future child resident's exposure to ground water, an ELCR range of 1x10-6 to 5x10-3 for an adult exposure to indoor air, and an ELCR range of 1x10-6 to 2x10-3 for a child exposure to indoor air. While sufficient direct soil exposure risk warranting soil cleanup was not identified in the baseline risk assessment, this remedy will address soil contamination to the extent necessary to protect ground water at the federal MCL. Treatment shall be monitored to ensure that cleanup levels are achieved. The site is expected to be available for unrestricted residential land use as a result of the remedy.
d: This compound is a potential COC for this medium.
c: The TCE action level has been calculated based on toxicity values developed by the California Environmental Protection Agency. Reportedly, the U.S. Office of Research and Development has encouraged Regions to use alternate toxicity values for TCE than the those values presented in USEPA's Draft Risk Characterization for TCE, prepared August 2001. USEPA Regions 4 and 8 have stated that they will be using an alternative toxicity value for addressing TCE risks. This alternative value, provided by Cal-EPA has been recommended for use by USEPA Region 4, and is provided here for evaluation of indoor air analytical data.
b: Cleanup level for adult exposure.
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Figure 4Site Conceptual ModelFlow-Chart FormGrants Chlorinated Solvents Plume SiteGrants, Cibola County, New Mexico
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Figure 5Site Conceptual ModelPictorial Form
Grants Chlorinated Solvents Plume SiteGrants, Cibola County, New Mexico
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Ground Waterand/orDNAPL
Migration
DNAPLDissolution
Shallow Ground Water (< 20 ft bgs)
Deeper Ground Water (> 20 ft bgs)
VolatilizationFrom Soil
Volatilization From Ground Water
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treet
Davis Avenue
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ie S
treet
Ande
rman
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et
Washington Avenue
Jefferson Avenue
Truman Avenue
Gei
s St
reet
Monroe Avenue
Firs
t Stre
et
Firs
t Stre
et
Seco
nd S
treet
Jefferson Avenue
Gei
s St
reet
Washington Avenue
Ande
rman
Stre
et
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DP-03
DP-01
DP-05 DP-06
DP-07
DP-02DP-34
DP-09
DP-14DP-15
DP-08
DP-11 DP-29
DP-13DP-12
DP-24
DP-23
DP-45
DP-41
DP-32 DP-30
DP-10DP-57 DP-20
DP-22DP-21
DP-17
DP-16
DP-31
DP-56
DP-55
DP-53DP-54
Figure 6Soil Sampling LocationsGrants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 200 400 600100
Feet
Legend
�� Direct-Push Soil Sampling Location
GCSP Site Boundary
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Davis Avenue
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et
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rman
Stre
et
Stephens Avenue
Washington Avenue
Jefferson Avenue
Truman Avenue
Gei
s St
reet
Monroe Avenue
Firs
t Stre
et
Firs
t Stre
et
Seco
nd S
treet
Jefferson Avenue
Gei
s St
reet
Washington Avenue
Ande
rman
Stre
et
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Adams Avenue
GC-11
GC-5
GC-10
GC-3.2
GC-3.3
GC-3.1
GC-6
GC-4
GC-8.2
GC-8.1
GC-7.2
GC-7.3
GC-7.4
GC-7.5
GC-7.1
GC-9
GC-2.4
GC-2.5 GC-1.4
GC-1.2GC-1.1
GC-2.3
GC-2.1
GC-2.2
GC-12
GC-1.3
HAW-06
HAW-03
HAW-01
HAW-02
HAW-04
HAW-07
HAW-05
DP-37DP-38
DP-39
DP-43
DP-44
DP-04
DP-03
DP-01
DP-05 DP-06
DP-07
DP-02
DP-36DP-35
DP-34DP-09
DP-50
DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-23
DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
DP-10DP-57
DP-20
DP-22DP-21
DP-17
DP-16
DP-52
DP-25
DP-70
DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-28DP-67
DP-85
DP-69
DP-84
DP-72
DP-75DP-83
DP-73
DP-66
DP-64
DP-65
DP-62
DP-76
DP-78
DP-74
DP-77
DP-60
DP-63
DP-81
DP-56
DP-55DP-53
DP-54
DP-82
RSJ-001
RSJ-002
RSJ-004
RSJ-005
RSJ-009
RSJ-010-S
RSJ-006 RSJ-007
RSJ-008
Figure 7Ground WaterSampling LocationsGrants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 300 600150
Feet
Legend
��Phase 1 Direct-Push Ground WaterSampling Location
��Phase 2 Direct-Push Ground WaterSampling Location
GCSP Site Boundary
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Hand Auger Ground WaterSampling Location
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Washington Avenue
Jefferson Avenue
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reet
Monroe Avenue
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t Stre
et
Firs
t Stre
et
Seco
nd S
treet
Jefferson Avenue
Gei
s St
reet
Washington AvenueAn
derm
an S
treet
Adams Avenue
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reet
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Figure 8Indoor Air and Soil VaporSampling Locations and ResultsGrants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
Notes:
Structure With Indoor Air ConcentrationsAt Or Below Tier 1 Action Level
Structure With Indoor Air ConcentrationsWithin Tier 2 Action Level
Structure With Indoor Air ConcentrationsAt Or Above Tier 3 Action Level
GCSP Site Boundary
�� October 2003 Soil Vapor Sampling Location
Refer to RI Tables 5-3 and 5-4 for indoor air sampling results.
Refer to RI Table 5-5 for soil vapor sampling results andexplanation of data qualifiers.
�� January 2004 Soil Vapor Sampling Location
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PCE = Tetrachloroethene.
TCE = Trichloroethene.
C12 = Cis-1,2-Dichloroethene.
VC = Vinyl Chloride.
B = Benzene.
T = Toluene.
E = Ethylbenzene.
Xm,p = m,p-Xylene.
Xo = o-Xylene.
MTBE = Methyl Tert-Butyl Ether.
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Gei
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reet
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et
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etJefferson Avenue
Gei
s St
reet
Washington Avenue
Ande
rman
Stre
et
(refusal)
GMW-6
GMW-5
W-5
W-4
W-3
V-1
W-2
W-1
W-7AW-10
W-8
GMW-2
W-9
GMW-1W-6 GMW-3
GMW-4
W-11
TMW-3
TMW-2
MW-11
MW-12
TMW-1MW-8
MW-7
MW-10
MW-6MW-9
HAW-06
HAW-01
Private 801
Private 700
Private 601
DP-37DP-38
DP-39
DP-43
DP-44
DP-04
DP-03
DP-01
DP-05 DP-06
DP-07
DP-02
DP-36DP-35
DP-34DP-09
DP-50
DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-23
DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
DP-10
DP-57 DP-20
DP-22DP-21
DP-17
DP-16
DP-52
DP-25
DP-70
DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-28DP-67
DP-85DP-69
DP-84
DP-72
DP-75DP-83
DP-73
DP-66
DP-64DP-78
DP-74DP-60
DP-81
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Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
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Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
�� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Direct-push sampling locations not on the map, or shown without a posted concentration, were non-detect for PCEduring the Phase 1 sampling event. Lab detection limitwas typically 1 �g/L.
L = Reported concentration is below the CRQL.
J = Estimated value.
* = Value not used for contouring.
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et
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reet
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t Stre
et
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et
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Gei
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reet
Washington Avenue
Ande
rman
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et
GMW-6
GMW-5
W-5
W-4
W-3
V-1
W-2
W-1
W-7AW-10
W-8
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W-9
GMW-1W-6 GMW-3
GMW-4
W-11
TMW-3
TMW-2
MW-11
MW-12
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MW-7
MW-10
MW-6MW-9
HAW-06
Private 801
Private 700
Private 601
DP-37DP-38
DP-39
DP-43
DP-44
DP-04
DP-03 DP-05 DP-06
DP-07
DP-36DP-35
DP-34DP-09
DP-50
DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-23
DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
DP-10
DP-57 DP-20
DP-22DP-21
DP-17
DP-16
DP-52
DP-25
DP-70
DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-85DP-69
DP-84
DP-74DP-60
Figure 11Structures With VaporIntrusion Mitigation SystemsGrants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
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Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Residential Structure Requiring VaporIntrusion Mitigation System Installation
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reet
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DP-44
DP-04
DP-03 DP-05 DP-06
DP-07
DP-36DP-35
DP-34DP-09
DP-50
DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-10
DP-57 DP-20
DP-22DP-21
DP-16DP-25
DP-48
DP-80
Figure 12Extent of Source AreaTreatmentGrants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 50 100 150
Feet
Legend
� �
�
Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Source Area
Extent of Source Area Soil Excavation
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Jefferson Avenue
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reet
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s St
reet
Washington Avenue
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rman
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et
GMW-6
GMW-5
W-5
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W-2
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W-8
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W-9
GMW-1W-6 GMW-3
GMW-4
W-11
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MW-12
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MW-7
MW-10
MW-6MW-9
HAW-06
Private 801
Private 700
Private 601
DP-39
DP-43
DP-44
DP-04
DP-03 DP-05 DP-06
DP-07
DP-36DP-35
DP-34DP-09
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DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-23
DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
DP-10
DP-57 DP-20
DP-22DP-21
DP-17
DP-16
DP-52
DP-25
DP-70
DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-28DP-67
DP-85DP-69
DP-84
DP-72
DP-74DP-60
Figure 13Conceptual Layout ofISCO with Follow-On ERD(Shallow Plume Core)Grants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
� �
�
Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Source Treatment Area
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ISCO = In-situ chemical oxidation
ERD = Enhanced reductive dechlorination
Rio San Jose
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treet
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Stre
et
Washington Avenue
Jefferson Avenue
Truman Avenue
Gei
s St
reet
Monroe Avenue
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t Stre
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t Stre
et
Jefferson Avenue
Gei
s St
reet
Washington Avenue
Ande
rman
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GMW-6
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W-5
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MW-12
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MW-7
MW-10
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Private 700
Private 601
DP-39
DP-43
DP-44
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DP-03 DP-05 DP-06
DP-07
DP-36DP-35
DP-34DP-09
DP-50
DP-51
DP-18
DP-19
DP-49
DP-14DP-15
DP-47
DP-46
DP-08DP-79
DP-11 DP-29
DP-13DP-12
DP-40
DP-24
DP-23
DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
DP-10
DP-57 DP-20
DP-22DP-21
DP-17
DP-16
DP-52
DP-25
DP-70
DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-28DP-67
DP-85DP-69
DP-84
DP-72
DP-74DP-60
Figure 14Conceptual Layout of ERDBio-Barrier(Shallow Plume Core)Grants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
� �
�
Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Source Treatment Area
Bio Barrier
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reet
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Figure 15Conceptual Layout of ERDBio-Barrier(Shallow Plume Periphery)Grants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
� �
�
Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Source Treatment Area
Bio Barrier for Shallow Plume Core
Shallow ground water plume core bio-barriers shown forreference only, and are not included in costs for peripherybio-barriers
Bio Barrier for Shallow Plume Periphery
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s St
reet
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rman
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Private 700
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DP-39
DP-43
DP-44
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DP-36DP-35
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DP-51
DP-18
DP-19
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DP-46
DP-08DP-79
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DP-13DP-12
DP-40
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DP-45
DP-41
DP-42
DP-32 DP-30
DP-33
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DP-22DP-21
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DP-25
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DP-48
DP-31
DP-58
DP-59
DP-61
DP-26
DP-68
DP-71
DP-80
DP-27
DP-28DP-67
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DP-84
DP-72
DP-74DP-60
Figure 16Conceptual Layout of ERDBio-Barriers(Deeper Plume)Grants Chlorinated Solvents Plume Site
Grants, Cibola County, New Mexico
�0 100 200 300 400
Feet
Legend
� �
�
Ground Water Monitoring Well
Private Well
Notes:
PCE = tetrachloroethene.
� Phase 1 Direct-Push Sampling Location
PCE Concentration Greater Than50,000 �g/L
PCE Concentration Ranging From5,000 �g/L to < 50,000 �g/L
PCE Concentration Ranging From500 �g/L to < 5,000 �g/L
PCE Concentration Ranging From50 �g/L to < 500 �g/L
PCE Concentration Ranging From5 �g/L to < 50 �g/L
PCE Concentration Ranging FromLab Detection Limit to < 5 �g/L
�� Phase 1 Hand-Auger Sampling Location
PCE maximum contaminant level (MCL) is 5 �g/L.
Source Treatment Area
Bio Barrier for Treatment to 80 ft bgs
Bio Barrier for Treatment to 60 ft bgs
Extent of Ground Water Exceeding PRGsBetween Surface and 20 ft bgs
Extent of Ground Water Exceeding PRGsBetween 20 and 60 ft bgs
� �
Extent of Ground Water Exceeding PRGsBetween 60 and 80 ft bgs
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Appendix A. Administrative Record Index
Prepared for
United States Environmental Protection Agency
Region 6
RECORD OF DECISION ADMINISTRATIVE RECORD
for
GRANTS CHLORINATED SOLVENTS SUPERFUND SITE
EPA ID No. NM0007271768
GS09K99BHD0010Task Order No. T0703BG1026
Sairam AppajiRemedial Project Manager
U.S. EPA Region 6
Prepared by
Science Applications International Corporation555 Republic Drive, Suite 300
Plano, TX 75074
JULY 17, 2006
1
PREAMBLE
The purpose of this document is to provide the public with an index to the AdministrativeRecord File (AR File) for the U.S. Environmental Protection Agency’s (EPA) selected remedialaction to respond to conditions at the Grants Chlorinated Solvents (the “Site”). EPA’s action isauthorized by the Comprehensive Environmental Response, Compensation, and Liability Act(CERCLA), 42 U.S.C. Section 9601 et seq.
Section 113 (j)(1) of CERCLA, 42 U.S.C. Section 9613 (j)(1), provides that judicial reviewof the adequacy of a CERCLA response action shall be limited to the Administrative Record (AR).Section 113 (k)(1) of CERCLA, 42 U.S.C. Section 9613 (k)(1), requires the EPA to establish an ARupon which it shall base the selection of its remedial actions. As the EPA decides what to do at thesite of a release of hazardous substances, it compiles documents concerning the site and it’s decisioninto an “AR File.” This means that documents may be added to the AR File from time to time.After the EPA Regional Administrator or the Administrator’s delegate signs the ActionMemorandum or the Record of Decision memorializing the selection of the action, the documentswhich form the basis for the selection of the response action are then known as the AdministrativeRecord “AR.”
Section 113(k)(1) of CERCLA requires the EPA to make the AR File available to the publicat or near the site of the response action. Accordingly, the EPA has established a repository wherethe AR File may be reviewed near the Site at:
New Mexico State UniversityGrants Campus
1500 Third StreetGrants, New Mexico
Contact: Steven ThomasTelephone:
The public also may review the AR File at the EPA Region 6 office in Dallas, Texas, bycontacting the Remedial Project Manager at the address listed below. The AR File is available forpublic review during normal business hours. The AR File is treated as a non-circulating referencedocument. Any document in the AR File may be photocopied according to the procedures used atthe repository or at the EPA Region 6 office. This index and the AR File were compiled inaccordance with the EPA’s Final Guidance on Administrative Records for Selecting CERCLAResponse Actions, Office of Solid Waste and Emergency Response (OSWER) Directive Number9833.3A1 (December 3, 1990).
Documents listed as bibliographic sources for other documents in the AR File might not belisted separately in the index. Where a document is listed in the index but not located among thedocuments which the EPA has made available in the repository, the EPA may, upon request, includethe document in the repository or make the document available for review at an alternate location.This applies to documents such as verified sampling data, chain of custody forms, guidance andpolicy documents, as well as voluminous site-specific reports. It does not apply to documents inEPA’s confidential file. (Copies of guidance documents also can be obtained by calling theRCRA/Superfund/Title 3 Hotline at (800) 424-9346.)
2
These requests should be addressed to:
Sairam AppajiRemedial Project Manager
U.S. EPA Region 61445 Ross Avenue
Dallas, Texas 75202-2733(214) 665-3126
The EPA response selection guidance compendium index has not been updated sinceMarch 22, 1991 (see CERCLA Administrative Records: First Update of the Compendium ofDocuments Used for Selecting CERCLA Response Actions [March 22, 1991]); accordingly, it is notincluded here. Moreover, based on resource considerations, the Region 6 Superfund DivisionDirector has decided not to maintain a Region 6 compendium of response selection guidance.Instead, consistent with 40 CFR Section 300.805(a)(2) and 300.810(a)(2) and OSWER Directive No.9833.3A-1 (page 37), the AR File Index includes listings of all guidance documents which may forma basis for the selection of the response action in question.
The documents included in the AR File index are arranged predominantly in chronologicalorder. The AR File index helps locate and retrieve documents in the file. It also provides anoverview of the response action history. The index includes the following information for eachdocument:
• Doc ID- The document identifier number.• Date - The date the document was published and/or released. “01/01/2525" means no
date was recorded.• Pages - Total number of printed pages in the document, including attachments.• Title - Descriptive heading of the document.• Document Type - General identification, (e.g. correspondence, Remedial Investigation
Report, Record of Decision.)• Author - Name of originator, and the name of the organization that the author is
affiliated with. If either the originator name or the organization name is not identified,then the field is captured with the letters “N/A”.
• Addressee- Name and affiliation of the addressee. If either the originator name or theorganization name is not identified, then the field is captured with the letters “N/A”.
ADMINISTRATIVE RECORD INDEX07/17/2006
ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
198864Docid:000001Bates: 000026To:09/01/1993Date:26Pages:PRESUMPTIVE REMEDIES: SITE CHARACTERIZATION AND TECHNOLOGY SELECTION FOR CERCLA SITES WITH VOLATILE ORGANIC COMPOUNDS IN SOIL
Title:
Doc Type: FACTSHEET
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
103935Docid:000027Bates: 000114To:10/01/1998Date:88Pages:PRELIMINARY ASSESSMENT FOR THE GRANTS CHLORINATED SOLVENTS SITETitle:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: GATTERMAN, DAVID NEW MEXICO ENVIRONMENT DEPARTMENT
Name OrganizationAddressee: NONE, NONE
934847Docid:000115Bates: 001234To:04/01/2001Date:1120Pages:SITE INSPECTION REPORT FOR THE GRANTS CHLORINATED SOLVENTS PLUME SITE (PART 1)
Title:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: NONE, NEW MEXICO ENVIRONMENT DEPARTMENT
Name OrganizationAddressee: NONE, NONE
Page 1 of 1007/17/2006
ADMINISTRATIVE RECORD INDEX07/17/2006
ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
198886Docid:001235Bates: 001317To:04/20/2001Date:83Pages:BUILDING RADON OUT: A STEP-BY-STEP GUIDE ON HOW TO BUILD RADON-RESISTANT HOMES
Title:
Doc Type: FACTSHEET
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
198837Docid:001318Bates: 001495To:11/01/2002Date:178Pages:OSWER DRAFT GUIDANCE FOR EVALUATING THE VAPOR INTRUSION TO INDOOR AIR PATHWAY FROM GROUNDWATER AND SOILS
Title:
Doc Type: FORM
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
199036Docid:001496Bates: 001500To:10/29/2003Date:5Pages:[REDACTED] VALIDATED INDOOR AIR SAMPLING RESULTS SUMMARY FOR 10/20/2003 THROUGH 10/29/2003
Title:
Doc Type: SAMPLING / ANALYSIS
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
Page 2 of 1007/17/2006
ADMINISTRATIVE RECORD INDEX07/17/2006
ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
163866Docid:001501Bates: 001668To:11/21/2003Date:168Pages:[SOIL - GAS SAMPLING FOR OCTOBER 2003]Title:
Doc Type: SAMPLING / ANALYSIS
Name OrganizationAuthor: THOMPSON, BEN NONE
Name OrganizationAddressee: MINCHAK, JEFF NONE
159760Docid:001669Bates: 002052To:12/01/2003Date:384Pages:SAMPLING AND ANALYSIS PLAN FOR GRANTS CHLORINATED SOLVENTS PLUME SITETitle:
Doc Type: SAMPLING / ANALYSISELECTRONIC RECORD
Name OrganizationAuthor: NONE, SCIENCE APPLICATIONS INTERNATIONAL
CORPORATION GEOMARINE, INCORPORATIONNONE, CH2M HILL
Name OrganizationAddressee: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
174944Docid:002053Bates: 002057To:12/23/2003Date:5Pages:TECHNICAL MEMORANDUM: INDOOR AIR SAMPLING RESULTS FOR 10/20/2003 THRUGH 10/21/2003
Title:
Doc Type: REPORT / STUDYELECTRONIC RECORD
Name OrganizationAuthor: MINCHAK, JEFFREY D CH2M HILL
Name OrganizationAddressee: APPAJI, SAIRAM U.S. ENVIRONMENTAL PROTECTION AGENCY
Page 3 of 1007/17/2006
ADMINISTRATIVE RECORD INDEX07/17/2006
ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
199025Docid:002058Bates: 002062To:01/21/2004Date:5Pages:[REDACTED] VALIDATED INDOOR AIR SAMPLING RESULTS SUMMARY FOR 10/20/2003 THROUGH 01/21/2004
Title:
Doc Type: SAMPLING / ANALYSIS
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
163865Docid:002063Bates: 002069To:02/03/2004Date:7Pages:HEALTH CONSULTATION - ATSDRTitle:
Doc Type: HEALTH ASSESSMENT
Name OrganizationAuthor: NONE, U.S. DEPARTMENT OF HEALTH AND HUMAN
SERVICES
Name OrganizationAddressee: NONE, NONE
174945Docid:002070Bates: 002071To:03/02/2004Date:2Pages:[INDOOR AIR DATA REVIEW OF RESIDENTIAL SAMPLING EVENTS ON 10/20/2003 AND 01/20/2004]
Title:
Doc Type: CORRESPONDENCEELECTRONIC RECORD
Name OrganizationAuthor: RILEY, DAVID U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: APPAJI, SAIRAM U.S. ENVIRONMENTAL PROTECTION AGENCY
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ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
199031Docid:002072Bates: 002077To:06/16/2004Date:6Pages:[REDACTED] VALIDATED INDOOR AIR SAMPLING RESULTS SUMMARY FOR 06/15/2004 THROUGH 06/16/2004
Title:
Doc Type: SAMPLING / ANALYSIS
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
198559Docid:002078Bates: 002081To:03/01/2005Date:4Pages:VALIDATED INDOOR AIR SAMPLE RESULTS FOR 01/21/2005 THROUGH 01/21/2005Title:
Doc Type: ELECTRONIC RECORDSAMPLING / ANALYSIS
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
198581Docid:002082Bates: 002082To:04/15/2005Date:1Pages:USGS STATEMENT OF WORK FOR GRANTS CHLORINATED SOLVENTS PLUME SITETitle:
Doc Type: ELECTRONIC RECORDREPORT / STUDY
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
Page 5 of 1007/17/2006
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ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
195881Docid:002083Bates: 002096To:11/01/2005Date:14Pages:TECHNICAL MEMO: DESCRIPTION OF FS ALTERNATIVES FOR GRANTS CHLORINATED SOLVENTS PLUME SITE
Title:
Doc Type: ELECTRONIC RECORDREPORT / STUDY
Name OrganizationAuthor: STERLING, DARNELL NONE
Name OrganizationAddressee: APPAJI, SAI U.S. ENVIRONMENTAL PROTECTION AGENCY
195882Docid:002097Bates: 002099To:11/08/2005Date:3Pages:CONFERENCE CALL MEETING MINUTES - GRANTS FS MEMOTitle:
Doc Type: ELECTRONIC RECORDCORRESPONDENCE
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
195877Docid:002100Bates: 002607To:12/01/2005Date:508Pages:FINAL REMEDIAL INVESTIGATION REPORTTitle:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: NONE, CH2M HILL
Name OrganizationAddressee: NONE, NONE
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ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
197898Docid:002608Bates: 002621To:12/01/2005Date:14Pages:[RESPONSE TO COMMENTS ON THE DRAFT REMEDIAL INVESTIGATION REPORT FOR GRANTS CHLORINATED SOLVENTS]
Title:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: NONE, CH2M HILL
Name OrganizationAddressee: NONE, NONE
198835Docid:002622Bates: 002634To:12/30/2005Date:13Pages:HEALTH CONSULTATION FOR GRANTS CHLORINATED SOLVENTTitle:
Doc Type: ELECTRONIC RECORDHEALTH ASSESSMENT
Name OrganizationAuthor: NONE, AGENCY FOR TOXIC SUBSTANCES AND DISEASE
REGISTRY
Name OrganizationAddressee: NONE, NONE
196272Docid:002635Bates: 002637To:01/09/2006Date:3Pages:SITE STATUS SUMMARY FOR GRANTS CHLORINATED SOLVENTSTitle:
Doc Type: ELECTRONIC RECORDFACTSHEET
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
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ADMINISTRATIVE RECORDSite Name:CERCLIS:OUID:SSID:Action:
GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
197376Docid:002638Bates: 002646To:02/24/2006Date:9Pages:[COMMENTS ON THE DRAFT FS REPORT AND RECOMMENDATIONS OF ALTERNATIVES FOR GRANTS CHLORINATED SOLVENTS PLUME SITE]
Title:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: JETTER, STEVE STATE OF NEW MEXICO ENVIRONMENT
DEPARTMENT
Name OrganizationAddressee: APPAJI, SAI U.S. ENVIRONMENTAL PROTECTION AGENCY
198474Docid:002647Bates: 002910To:03/01/2006Date:264Pages:FINAL FEASIBILITY STUDY REPORT FOR GRANTS CHLORINATED SOLVENTS PLUME SITETitle:
Doc Type: REPORT / STUDY
Name OrganizationAuthor: NONE, CH2M HILL
NONE, SCIENCE APPLICATIONS INTERNATIONAL CORPORATION GEOMARINE, INCORPORATION
Name OrganizationAddressee: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
198834Docid:002911Bates: 002912To:03/16/2006Date:2Pages:COMMENTS ON THE DRAFT ATSDR HEALTH CONSULTATIONTitle:
Doc Type: CORRESPONDENCE
Name OrganizationAuthor: BAHAR, DANA NEW MEXICO ENVIRONMENT DEPARTMENT
Name OrganizationAddressee: MANN, JOHN AGENCY FOR TOXIC SUBSTANCES AND DISEASE
REGISTRY
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GRANTS CHLORINATED SOLVENTSNM0007271768
HERECORD OF DECISION
198580Docid:002913Bates: 002943To:03/30/2006Date:31Pages:RESPONSE TO COMMENTS ON THE DRAFT FEASIBILITY STUDY REPORTTitle:
Doc Type: ELECTRONIC RECORDREPORT / STUDY
Name OrganizationAuthor: NONE, CH2M HILL
Name OrganizationAddressee: NONE, NONE
198937Docid:002944Bates: 002969To:04/01/2006Date:26Pages:EPA ANNOUNCES PROPOSED PLAN FOR GRANTS CHLORINATED SOLVENTSTitle:
Doc Type: FACTSHEET
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
198935Docid:002970Bates: 002970To:04/12/2006Date:1Pages:[PUBLIC NOTICE: EPA ANNOUNCES PROPOSED PLAN FOR THE GRANTS CHLORINATED SOLVENTS]
Title:
Doc Type: FACTSHEET
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
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HERECORD OF DECISION
204145Docid:002970.001Bates: 002970.002To:05/26/2006Date:2Pages:NMED COMMENTS AND RECOMMENDATIONS ON RECORD OF DECISION FOR THE GRANTS CHLORINATED SOLVENTS SITE
Title:
Doc Type: TABLEELECTRONIC RECORD
Name OrganizationAuthor: NONE, NONE
Name OrganizationAddressee: NONE, NONE
203745Docid:002971Bates: 003259To:06/30/2006Date:289Pages:RECORD OF DECISION FOR GRANTS CHLORINATED SOLVENTSTitle:
Doc Type: RECORD OF DECISION / AMENDMENT
Name OrganizationAuthor: NONE, U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: NONE, NONE
948605Docid:003260Bates: 003261To:01/01/2525Date:2Pages:[COMMENTS ON DRAFT SAMPLING AND ANALYSIS PLAN]Title:
Doc Type: CORRESPONDENCE
Name OrganizationAuthor: WILLIAMS, DONALD U.S. ENVIRONMENTAL PROTECTION AGENCY
Name OrganizationAddressee: HALLORAN, AMY CH2M HILL
Page 10 of 1007/17/2006
Appendix B. Cost Estimate for Selected Remedy
Table B-1Cost Estimate Summary for the Selected Remedy
Remedy Component Item Description Quantity Unit Unit Cost CostInstall 14 Vapor Mitigation Systems LS 425,000.00$ One-time Vapor Pump Replacement 14 EACH 500.00$ 7,000.00$
Vapor Intrusion Mitigation Capital Costs 395,000.00$ Vapor Intrusion Mitigation O&M Costs (see Table B-2) 46,560.00$
NM Gross Receipts Tax (7.5%) 33,120.00$ Vapor Intrusion Mitigation Subtotal 474,680.00$
Vendor Design and Permitting Input LS 150,000.00$ Mobilization and Procurement LS 79,000.00$ Drill and Install Borings, Wells, and Sub-Grade Infrastructure LS 1,523,000.00$ Vapor Cover Installation LS 104,000.00$ Electrical Construction LS 105,000.00$ Mechanical Construction LS 185,000.00$ Vapor and Water Treatment System LS 750,000.00$ Commissioning LS 80,000.00$ Maintenance Hardware, Etc. LS 218,000.00$ Operations Labor, Per Diem LS 417,000.00$ Power ($0.072 per kWh) LS 1,014,000.00$ Process Sampling and Analysis LS 37,000.00$ Waste and GAC LS 32,500.00$ Rental and Fees LS 30,000.00$ Demobilization LS 55,000.00$ Vendor Reporting LS 30,000.00$ Vendor Travel, Office, and Engineering Support LS 647,000.00$ Licensing Fees LS 199,000.00$ Vendor Contingency and Indirect Cost LS 774,000.00$
Total Thermal Source Area Treatment Vendor Costs 6,429,500.00$ Total Thermal Source Area Treatment O&M Costs (see Table B-2) -$
Thermal Source Area Program Management and Support (10%) 643,000.00$ Thermal Source Area Project Design (6% of Capital Costs) 386,000.00$
NM Gross Receipts Tax (7.5%) 559,000.00$ Thermal Source Area Treatment Subtotal 8,017,500.00$
Pre-Construction Activities (Including Pilot-Scale Testing) LS 419,450.00$
Injection and Monitoring Well Construction LS 474,100.00$ Trailer-Mounted Injection System LS 36,000.00$ Initial ISCO Injection - Mobilization LS 51,000.00$ Initial ISCO Injection - Potassium Permanganate 527,793 LBS 1.55$ 818,079.00$ Initial ISCO Injection - Potassium Permanganate Shipping 527,793 LBS 0.13$ 68,613.00$ Initial ISCO Injection - Sodium Thiosulfate (Oxidant Neutralizer) 550 GAL 7.25$ 3,988.00$ Initial ISCO Injection - Sodium Thiosulfate Shipping 1 LOAD 600.00$ 600.00$ Initial ISCO Injection - Water 1,795 1,000 GAL 1.64$ 2,944.00$ Initial ISCO Injection - Mixing Equipment and Material LS 50,000.00$ Initial ISCO Injection - Equipment Setup and Related Expenses LS 59,900.00$ Initial ISCO Injection - Royalties, Construction Management Fees, and Markup LS 126,600.00$ Initial ISCO Injection Labor LS 241,375.00$ Second ISCO Injection - Mobilization LS 22,500.00$ Second ISCO Injection - Potassium Permanganate 263,945 LBS 1.55$ 409,115.00$ Second ISCO Injection - Potassium Permanganate Shipping 263,945 LBS 0.13$ 34,313.00$ Second ISCO Injection - Sodium Thiosulfate (Oxidant Neutralizer) 550 GAL 7.25 3,988.00$ Second ISCO Injection - Sodium Thiosulfate Shipping 1 LOAD 600.00$ 600.00$ Second ISCO Injection - Water 898 1,000 GAL 1.64$ 1,473.00$ Second ISCO Injection - Mixing Equipment and Material LS 5,000.00$
Source Area - Thermal Treatment Capital Costs (vendor price quote with
adjustment for local drilling rates)
Vapor Intrusion Mitigation Capital Costs
Shallow Plume Core and Hot Spot - ISCO With Follow-On ERD Capital Costs
Table B-1Cost Estimate Summary for the Selected Remedy
Remedy Component Item Description Quantity Unit Unit Cost Cost
Shallow Plume Core and Hot Spot - ISCO With Follow-On ERD Capital Costs Second ISCO Injection - Equipment Setup
and Related Expenses LS 34,000.00$ Second ISCO Injection - Royalties, Construction Management Fees, and Markup LS 61,300.00$ Second ISCO Injection Labor LS 127,700.00$ Primary Performance Monitoring LS 15,000.00$ Reporting LS 31,200.00$ Undefined Scope and Market Allowance LS 464,800.00$
Total ISCO With Follow-On ERD Shallow Plume Core Treatment Capital Costs 3,563,638.00$ Total ISCO With Follow-On ERD Shallow Plume Core Treatment O&M (ERD Treatments) Costs (see Table B-2) 1,933,857.00$
Shallow Plume Core and Hot Spot Treatment Program Management and Support (10%) 549,750.00$ Shallow Plume Core and Hot Spot Project Design (6% of Capital Costs) 213,800.00$
NM Gross Receipts Tax (7.5%) 469,600.00$ Shallow Plume Core and Hot Spot Treatment Subtotal 6,730,645.00$
Pre-Construction Activities (Including Pilot-Scale Testing) LS 250,770.00$
Injection and Monitoring Well Construction LS 355,600.00$ Trailer-Mounted Injection System LS 36,000.00$ Undefined Scope and Market Allowance LS 96,360.00$
Total ERD Shallow Plume Periphery Treatment Capital Costs 738,730.00$ Total ERD Shallow Plume Periphery Treatment O&M (ERD Treatments) Costs (see Table B-2) 1,989,050.00$
Shallow Plume Periphery Treatment Program Management and Support (10%) 272,800.00$ Shallow Plume Periphery Project Design (6% of Capital Costs) 44,320.00$
NM Gross Receipts Tax (7.5%) 228,370.00$ Shallow Plume Periphery Treatment Subtotal 3,273,270.00$
Pre-Construction Activities (Including Pilot-Scale Testing) LS 263,270.00$
Injection and Monitoring Well Construction LS 837,500.00$ Trailer-Mounted Injection System LS 36,000.00$ Undefined Scope and Market Allowance LS 170,520.00$
Total ERD Deep Plume Treatment Capital Costs 1,307,290.00$ Total ERD Deep Plume Treatment O&M (ERD Treatments) Costs (see Table B-2) 4,729,000.00$
Deep Plume Treatment Program Management and Support (10%) 603,630.00$ Deep Plume Project Design (6% of Capital Costs) 78,440.00$
NM Gross Receipts Tax (7.5%) 503,880.00$ Deep Plume Treatment Subtotal 7,222,240.00$
RD/RA Project Management 589,730.00$ Project Planning Documents (Work Plan, QAPP, HASP) 138,668.00$ Preliminary Design Field Investigation 1,230,019.00$ Ground Water Sampling Program 1,383,910.00$ Five-Year Reviews 180,000.00$
Required RD/RA Components Subtotal 3,522,327.00$
Total Present Worth Estimated Cost of Preferred Remedy 29,240,662.00$
Notes
LS = Lump SumGAL = GallonLBS = PoundkWh = Kilowatt-hourQAPP = Quality Assurance Project PlanHASP = Health and Safety Plan
Capital cost estimates are not discounted because the construction work will be performed in the first year. O&M costs are reported as present worth estimates given a 7% discount rate over the duration of the respective treatment period (6 years for shallow plume core; 20 years for shallow plume periphery; 20 years for deep plume). O&M costs are detailed in subsequent Tables B-2 and B-3. Cost estimates are based on estimated quantities and assumptions described in the Feasibility Study, and may be refined following the Preliminary Design Field Investigation and during the Remedial Design. Cost estimates are within +50 to -30% accuracy expectation.
Shallow Plume Periphery - ERD Bio Barriers Capital Costs
Deep Plume Treatment - ERD Bio Barriers Capital Costs
Table B-2Estimated O&M Costs for the Selected Remedy
Remedy Component Item Description Quantity Unit Unit Cost Cost Present Worth O&M Cost 1
Five-Year Indoor Air Sampling Event LS 38,118.00$ Ten-Year Indoor Air Sampling Event LS 38,118.00$
Vapor Intrusion Mitigation O&M Costs 76,236.00$ Present Worth Cost of $38,118 expended during years 5 and 10 at 7% discount rate = 46,560.00$
Thermal Source Area Treatment O&M Costs No O&M Costs for Thermal Treatment -$ -$
Thermal Source Area Treatment O&M Subtotal -$ -$ Injection Mobilization; Site Trailer LS 12,000.00$ Emulsified Edible Oil 121 DRUM 1,050.00$ 127,050.00$ Emulsified Edible Oil - Shipping 2 LOAD 1,200.00$ 2,400.00$ Water 875 1,000 GAL 1.64$ 1,435.00$ Rentals, Equipment, and Materials LS 6,500.00$ Injection Labor LS 167,280.00$ Reporting LS 24,850.00$
Performance/Effectiveness Monitoring LS 64,200.00$ Total ISCO With Follow-On ERD Shallow Plume Core Treatment O&M Costs 405,715.00$
O&M Period 6 YearsPresent Worth Cost of $405,715 per year for 6 years at 7% discount rate = 1,933,900.00$
Shallow Plume Periphery - ERD O&M Costs Injection Mobilization; Site Trailer LS 9,000.00$
Emulsified Edible Oil 66 DRUM 1,050.00$ 69,300.00$ Emulsified Edible Oil - Shipping 2 LOAD 1,200.00$ 2,400.00$ Water 317 1,000 GAL 1.64$ 519.88$ Rentals, Equipment, and Materials LS 9,500.00$ Injection Labor LS 62,320.00$ Reporting LS 24,850.00$
Performance/Effectiveness Monitoring LS 56,800.00$ O&M Period 20 Years
Total ERD Shallow Plume Periphery Treatment O&M Costs 234,689.88$ Total Annual Shallow Plume Periphery Treatment O&M Costs (Injection Every 15 Months) 187,751.90$
Present Worth Cost of $187,752 per year for 20 years at 7% discount rate = 1,989,050.00$
Deep Plume - ERD O&M Costs Injection Mobilization; Site Trailer LS 21,000.00$ Emulsified Edible Oil 184 DRUM 1,050.00$ 193,200.00$ Emulsified Edible Oil - Shipping 6 LOAD 1,200.00$ 7,200.00$ Water 1,000 1,000 GAL 1.64$ 1,640.00$ Rentals, Equipment, and Materials LS 14,000.00$ Injection Labor LS 190,240.00$ Reporting LS 48,900.00$
Performance/Effectiveness Monitoring LS 81,800.00$ O&M Period 20 Years
Total ERD Deep Plume Treatment O&M Costs 557,980.00$ Total Annual Deep Plume Treatment O&M Costs (Injection Every 15 Months) 446,384.00$
Present Worth Cost of $446,384 per year for 20 years at 7% discount rate = 4,729,000.00$ Notes1: Present value costs use a discount rate of 7% over the O&M performance period.2: Vapor mitigation system O&M costs include indoor air sampling after 5 years and 10 years. Present value costs assume a 7% discount rate.Thermal source area treatment does not have an O&M component as costs are expected to be incurred during the first year of the RA.LS = Lump SumGAL = Gallon
Vapor Intrusion Mitigation O&M Costs 2
Shallow Plume Core and Hot Spot - ISCO With Follow-On ERD O&M (ERD Treatments) Costs
Appendix C. NMED Concurrence With
the Selected Remedy
06/19/06 _15:07_FAX_ 5058272965 GROUND WATER BUREAU |gj002
•?State of New Mexico
ENVIRONMENT DEPARTMENTOffice of the Secretary
Harold Runnels Building
*' im St-Francis Drive> p-°-Box 2611°Sattta Fe, New Mexico 87502-6110
'- " Telephone: (505) 827-2855BILL RICHARDSON pnr. fc(ic\ 017 joi* RON CURRY
GOVERNOR FaX- (5°5) S27~2836 SECRETARY
DERRITH WATCHMAN-MOOREDEPUTY SECRETARY
June 16,2006
Mr. Samuel J. Coleman, P.E.DirectorSuperfund DivisionUSEPA Region 61445 Ross Avenue, Suite 1200Dallas, TX 75202-2733
RE: Concurrence on Record of Decision for the Grants Chlorinated Solvents Plume SuperfundSite, Grants, New MexicoEPA CERCLIS ID #NM007271768
Dear Mr. Coleman,
The New Mexico Environment Department (NMED) has reviewed the United States EnvironmentalProtection Agency's (EPA) Draft Record of Decision (ROD) for the Grants Chlorinated SolventsPlume Superfund Site located in Grants, New Mexico.
NMED concurs with the remedial 3.ctions outlined in the draft ROD to address contaminationassociated with this Site including:
1. Indoor Air - Vapor Mitigation System2. Source Area-Thermal Treatment3. Shallow Ground Water Plume and Hot Spot - In-Situ Chemical Oxidation (ISCO) with
Follow-On Enhanced Reductive Dechlorination (ERD)4. Shallow Ground Water Plume Periphery-ERD5. Deeper Ground Water contamination - ERD
NMED appreciates EPA's acceptance of a 1 x 10~5 risk factor for soil and vapor intrusion clean uplevels which are in line with NMED risk based clean up guidance. In addition, NMED is pleased withthe aggressive treatment technology selected to address Indoor Air Vapor Intrusion, the Source Areaand the Shallow Ground Water Plume Core and Hot Spot
NMED's concurrence is based on (he facts presented in the draft ROD and on available-data collectedto date. NMED understands that any changes to the selected remedy will require NMED concurrence.
06/19/0615:08 FAX 5058272965 GROUND WATER BUREAU@003
Mr. Samuel J. ColemanJune 16,2006Page 2
Please note that based upon the current available site data, NMED does not support the contingency inthe draft ROD for potentially using EJ thanced Reductive Dechlorination (ERD) as a stand alonetechnology in the Shallow Ground Water Plume Core and Hot Spot Area as it may adversely impactthe overall effectiveness and timeframe of the clean up. Similarly, at this time, it is NMED's positionthat the contingency in the draft ROD for the potential use of Monitored Natural Attenuation as aremedial strategy for the Shallow Ground Water Plume Periphery and Deeper Ground Watercontamination is not appropriate for ttie same reasons listed above. NMED also understands that anynew information associated with this site, including adverse health risks or data regarding the extent ofcontamination and migration of contaminants, identified during subsequent design investigations andnot presented in this draft ROD will be addressed by EPA as part of this Superfund site.
This draft ROD is a culmination of cooperative work conducted by the EPA and NMED. As in thepast, NMED project staff will continue to work closely with EPA staff on design and implementationof the remedy. NMED appreciates uhe continued supportive working relationship with EPA in thesematters. If you have any questions, please call me at (505) 827-2855, or Steve letter of my staff at(505) 827-2334.
Sim
RC:sj
cc: Sai Appaji, EPA Remedial Project ManagerDon Williams, EPA, Team LeaderDana Bahar, NMED Superfrmd Oversight Section ManagerSteve Jetter, NMED Projec: Manager
Appendix D. Responsiveness Summary
Stakeholder Issues and Lead Agency Responses
NMED Comments
Comment 1 In reference to the Land and Ground Water Use Assumptions - NMED emphasizes that
the New Mexico Water Quality Control Commission (NMWQCC) Regulations, NMAC
20.6.2.4101.A(1) requires that all ground water of the State of New Mexico with a TDS of
<10,000 mg/l be remediated or protected for use as domestic and agricultural water
supply. Although the contaminated ground water (from 5 to 80 ft bgs) at the site is not
currently used as a drinking water supply, there are no enforceable institutional controls
that would prohibit the use of this aquifer, now or in the future, as a drinking water
supply. The fact that three shallow private wells exist within the site boundaries is
evidence that the aquifer can be used for beneficial use. As proposed, ground water
must be remediated to the more stringent requirements of the Federal Safe Drinking
Water standards (MCLs) and/or NMWQCC standards.
EPA Response:
Comment noted. EPA’s final clean up levels for the COCs at this Site is federal MCL
and NMWQCC standards.
Comment 2 Preliminary Remediation Goals and use of 1x10-4 excess lifetime cancer risk (ELCR) as
the targeted cleanup level - The National Contingency Plan established a targeted risk
level 1 x 10-6 as a “point of departure” for determining remediation goals. There has
been no justification presented by EPA to modify this targeted risk level and justify the
use of a less stringent risk-based clean up level. At a minimum, an ELCR of 1 x 10-5 and
an HI of 1 which is consistent with the NMWQCC Regulations and NMED’s Technical
Background Document for Development of Soil Screening Levels, Revision 3.0, August 2005,
should be used for establishing targeted cleanup levels for indoor air and soil. NMED
requests that the PRGs for COCs in soil and from vapor impacts be established using at
least a 1 x 10-5 ELCR and an HI of 1 and a residential land use scenario.
1
EPA Response:
1E-06 is the point of departure, and EPA has the flexibility to modify cleanup levels for
carcinogens within the range of 1E-06 to 1E-04, especially when considering site-specific
conditions. This is indicated in the NCP (40 CFR 300.430(e)(2)(i)(A)(2 ):
“For known or suspected carcinogens, acceptable exposure levels are generally concentration
levels that represent an excess upper bound lifetime cancer risk to an individual of between 10-4
and 10-6 using information on the relationship between dose and response.”
The EPA agrees with NMED’s concerns regarding uncertainties at the Site and will take
Remedial Action at the lower risk level (1x10-5).
Comment 3 In reference to risk and the preliminary remediation goals. NMED does not support the
use risk based clean up levels that are less stringent than residential clean up levels for
this site. The site is located in a mixed commercial and residential use area and there are
no enforceable institutional controls that can be implemented to restrict future land use.
Therefore, the more restrictive clean up levels, i.e. residential, should be used.
EPA Response:
EPA will use NMED’s Guidance document (Technical Background Document for
Development of Soil Screening Levels, Revision 3.0, August 2005) on Soil Screening
Levels to establish clean up levels based on residential use.
Comment 4 In reference to the flexible approach in selection of the final remedy for the Shallow
Plume Core and Hot Spot Area - NMED is concerned with how the final selection
between ISCO and ERD will be determined due to the difficulties associated with
detecting the DNAPL in the field. NMED is concerned that a significant amount of time
and expense could be expended without conclusively determining whether or not
DNAPL is absent from this area. In addition, the pre-design investigations proposed in
the Feasibility Study did not include investigation activities associated with determining
2
the nature and extent of DNAPL but instead concentrated on definition of the dissolved
phase plume and soil contamination in the two source areas. As stated in the RI report
and in literature on the subject, it is generally assumed that DNAPL is present if ground
water exceeds 1 to 5 percent of the chemicals solubility limit in water and the dissolved
PCE concentrations observed within the Plume Core Area are as high as 35%. At this
concentration it should be assumed that DNAPL is present in close proximity to the
sample locations and ISCO is better suited for this condition. Finally, because ISCO with
follow-on ERD alternative addresses the entire plume through the installation of a grid
pattern of wells the ISCO alternative is more amenable to treating the Core
Plume/Hotspot area verses the passive nature of diffusion associated with the ERD
alternative. If residual DNAPL is present between the ERD bio-barriers, the likelihood
of effective and timely clean-up using the ERD bio-barrier alternative is greatly reduced.
Therefore, NMED may not support the use of ERD as the stand alone remedial
technology for the Shallow Plume Core and Hot Spot area.
EPA Response:
EPA’s policy is to treat principal threats posed by the Site through use of treatment
technologies. By utilizing treatment as a significant portion of the Selected Remedy, the
statutory preference for remedies that employ treatment as a principal element is
satisfied. The EPA agrees and will select ISCO with Follow-On ERD (Flexible) treatment
approach for the Shallow Plume Core and Hot Spot for the following reason:
Thermal treatment at the Source Area is expected to achieve complete removal of
principal threat waste. After Source Area treatment is complete and if it can be
demonstrated that the principal threat waste no longer exists in the Shallow Plume Core
and Hot Spot area then the EPA will re-evaluate the two treatment technologies
(ISCO/with Follow-On ERD or ERD alone) to determine which one of these better meets
the Statutory Preference for Treatment. Based on this determination the EPA will
implement either of the two technologies to address the Shallow Plume Core and Hot
Spot Area.
3
Community Comments
The following comments were received from members of the public that were in
attendance at the Proposed Plan public meeting held on April 20, 2006.
Comment 1 How was the contamination originally verified at the GCSP Site?
EPA Response:
The NMED-PSTB discovered chlorinated solvents in ground water at the GCSP Site
during a UST investigation at the Allsup’s 200 gas station in 1993. Following the
discovery, NMED conducted two years of ground water monitoring at the Allsup’s
monitoring wells to verify contamination.
Comment 2 Are the depths of the City Drinking Water wells known?
EPA Response:
Yes. City well Grants B-40 is screened at a depth from 246 feet (ft) below ground surface
(bgs) to 346 ft bgs and the total depth of the well is 367 ft bgs. The second City well,
Grants B-38, is screened between 149 ft bgs and 300 ft bgs and the total depth of this well
is 300 ft bgs. Both of these wells are upgradient and are located approximately 1.5 miles
northwest of the GCSP Site.
Comment 3 Are the City wells located in the same aquifer that is impacted at the GCSP Site?
EPA Response:
No. The contamination at the GCSP Site is in a shallow aquifer and the vertical extent is
not fully known at this time. The City drinking water wells pump water from much
greater depths, and are upgradient of the GCSP Site. The maximum depth at which
contamination was detected during the RI is 85 ft bgs. The EPA will fully characterize
the maximum depth of contamination during the Pre-Design Field Investigation.
4
Comment 4 Is the project funded for the Remedial Design?
EPA Response:
Yes. Funding for Remedial Design has been planned for fiscal Year 2006.
Comment 5 Are there many other sites in the country similar to Grants?
EPA Response:
Yes. There are a number of other Superfund sites in the country that are similar to
Grants. In New Mexico alone there are five sites, including the GCSP Site, where EPA is
cleaning up ground water contaminated with chlorinated solvents. These five sites
include Fruit Avenue Plume, Albuquerque; North Railroad Avenue Plume, Espanola;
McGaffey and Main, Roswell; Griggs and Walnut, Las Cruces; and the GCSP Site,
Grants.
Comment 6 Is the bio-barrier wall a physical wall installed underground?
EPA Response:
Bio-barrier walls are not actual physical walls but function as a wall when nutrients are
injected across sections of the plume. Injection points are closely spaced along a line
across the plume, such that the aquifer between each injection point is filled with the
injected oxidant or carbon source amendment. When the oxidant or carbon source
amendments are injected into the ground they permeate into the aquifer and begin
treating the ground water.
Zero-valent iron permeable reactive barriers are actual physical walls constructed of iron
filings installed within trenches dug across the plume. The walls required for the GCSP
Site would be as thick as 36 inches and up to 60 ft deep. A zero-valent iron permeable
reactive barrier was considered as one of the alternatives for the Site but was not chosen
as the Selected Remedy.
5
Comment 7 Will the public be notified when a final decision is made regarding the Preferred
Remedy?
EPA Response:
Yes. The EPA will notify the community of the final selection of the remedy after it
reviews and responds to all the comments received during the comment period.
Newspaper notification will be made in the local newspaper when the Record of
Decision is signed.
6
Appendix E. NRRB Comments and EPA Region 6 Responses
UNITED STATES ENVIRONMENTAL PROTECTION AGENCYDALLAS, TX 75202
MEMORANDUM
SUBJECT: Response to the National Remedy Review Board (NRRB) Comments for theGrants Chlorinated Solvents Plume Superftmcf Site
FROM: Samuel Coleman, DirectorNational Remedy Review Board
^THROUGH: Donald WilliamsTeam Leader, Supefund Division
TO:
Purpose
David E. Cooper, ChairNational Remedy Review BoardU.SEPA
This memorandum documents the Region 6's response on the Grants ChlorinatedSolvents Plume Site (Site) comments received from the NRRB's advisory committee.
NRRB Comments and EPA Region 6 Responses
NRRB Comment 1The site information package acknowledges that data characterizing subsurface conditions,contaminant distribution, fate and transport, and risk are limited. These unknowns producesignificant uncertainties in the selection, design, and implementation of remedial options andthe estimated costs and time frames associated with these options. The Board recommendsthat the Region consider a ROD that contains a phased approach that allows flexibility inremedy design and implementation as additional characterization and performancemonitoring data become available. For example, Phase 1 could include actions to eliminateexposure to vapors intruding into homes and thermal treatment of the source area. Phase IIcould include remediation of the Shallow Ground Water Plume Core and Hot Spot Area,along with shallow ground water peripheral plume and deep ground water actions.
NRRB Comments and Region 6 Responses
EPA Region 6 Response to Comment 1Region 6 agrees with the Board comment and believes that a phased approach and a RODproviding flexibility during Remedial Design (RD) and implementation will work better atthe Site. Using a phased approach, additional site characterization data collected during theearly phases will allow a more detailed evaluation of how best to implement subsequentphases and will streamline the work effort and provide the greatest opportunity for costsavings.
A phased approach would allow data collection efforts conducted during early phases ofwork to provide the evidence necessary to support the selection of MNA for certain portionsof the Site. The ROD for the Site will have a contingency to switch to MNA if it can bedemonstrated as an effective alternative.
NRRB Comment 2The Board notes there is uncertainty regarding the existence of dense non-aqueous phaseliquids (DNAPL) in the Shallow Plume Core and Hot Spot Area. As a result, the Boardunderstands the concern expressed by the State of New Mexico that the enhanced reductivedechlorination (ERD) remedy may not be sufficiently effective. Therefore, the Boardrecommends that the Region consider the results of Phase 1 (as recommended in comment #1above) and investigate the presence or-absence of DNAPL in the Shallow Plume Core andHot Spot Area prior to implementing a final remedy, for this area.
EPA Region 6 Response to Comment 2Region 6 agrees with the Board recommendation and has selected the more aggressiveISCO/with follow-on ERD for the Shallow Plume Core and Hot Spot Area. However, theROD will be flexible enough to revert to using only ERD if conditions warrant. EPA Region6 will evaluate ground water data after source removal and if it can be demonstrated thatDNAPL no longer exists then EPA with NMED's concurrence will implement only the ERDcomponent for the Shallow Plume Core and Spot Area.
NRRB Comment 3The Board recommends, based on the results of Phase I and the investigations for thepresence or absence of DNAPL, that the Region consider evaluating an alternative whichuses ISCO followed by a less extensive ERD component for the Shallow Plume Core andHot Spot Area. If ISCO is used to treat the Shallow Plume Core and Hot Spot Areaaggressively, ISCO could address the potential DNAPL and significantly reduce the highconcentrations of volatile organic compounds (VOCs) in ground water. The ERDcomponent could then be optimized, which should result in a reduced number of wells, thusreducing cost. This approach would likely eliminate the bulk of the VOC contaminationquickly, but may result in a longer timeframe to achieve cleanup levels. This approach maystill be protective and consistent with the NCP expectation to restore ground water tobeneficial use in a time frame that is reasonable given the particular circumstances of the site(e.g., given that the shallow aquifer is not currently being used).
NRRB Comments and Region 6 Responses
EPA Region 6 Response to Comment 3The EPA Region 6 agrees with the board recommendation and has structured the ROD to beflexible in applying treatment in the Shallow Plume Core and Hot Spot Area.
NRRB Comment 4The Board recommends that the Region further evaluate the implementation of ISCO as aremedial alternative in the Source Area. In the ISCO alternative presented to the Board forthe Source Areas, significant costs are included for soil excavation and disposal, as well astrench dewatering and water treatment. However, the soil excavation and disposal followedby trench dewatering and treatment components may not be required. ISCO can be aneffective option for remediating organic contaminants in the unsaturated zone and its use inunsaturated zones is becoming increasingly common, thereby eliminating the need toexcavate and dispose of contaminated soils. ISCO also could be used to treat organiccompounds in water that collects in trenches. Oxidant injection and mixing directly in thetrench, would be easily implementable and likely to be successful at this site for oxidizingthese contaminants, as well as for providing residual oxidant to the underlying aquiferthrough infiltration. Potential limitations to using the ISCO technology at the site givensubsurface conditions at the site (soil, geologic, and hydrologic settings), as expressed by theNew Mexico Environmental Department (NMED), also need to be considered. Furtherevaluation of these technical issues is recommended.
EPA Region 6 Response to Comment 4EPA Region 6 agrees with the Board recommendation and further evaluated the ISCOalternative for the Source Area. However, given the soil conditions at the site Region 6believes that Thermal Treatment is a better technology than ISCO for treating the SourceArea. Thermal Treatment will remove the principal waste in a relatively very short timeframe compared to ISCO that will require at least six years.
NRRB Comment 5The Board agrees with the Region's preference not to include a zero-valent iron permeablereactive barrier as part of the preferred alternative. The clay and thin sandy layers present atthe site may not lend themselves to this technology. Smearing of the clay along the face ofthe trench during excavation could significantly decrease permeability. Also, a barriercontaining 100% iron and constructed to depths of 60 feet would need further study todemonstrate implementability and effectiveness. The Board recommends that the Regioninclude a discussion of the potential limitations of installing such a deep trench and the likelydecrease in permeability due to the 100% iron composition of the barrier in the decisiondocuments to further explain its preference against this alternative.
tEPA Region 6 Response to Comment 5Comment Noted. The ZVI-PRB alternative is very expensive and would be extremelydisruptive to the community when installed in a residential area. The recommendeddiscussion will be provided in the decision document.
NRRB Comment 6As part of the Region's preferred alternative presented to the Board, vapor intrusionmitigation systems would be installed in three residential structures. Long-term indoor air
NRRB Comments and Region 6 Responses
monitoring would be undertaken at a larger number of residences situated above the groundwater plume. Given the high costs of air monitoring in relation to the mitigation systems, theBoard recommends that the Region consider expanding the installation of mitigation systemsto all residences potentially impacted by indoor air contamination. In the event that long-term monitoring is chosen, homes above and in the proximity of the ground water plume,especially the homes near the Source Area, should be monitored to take into accountpreferential subsurface pathways that may exist at this site. The Board also recommends thatthe Region consider taking action under removal authorities at those occupied residenceswith vapor intrusion risks exceeding 1 x 10"4 lifetime excess cancer risk.
EPA Region 6 Response to Comment 6Region 6 agrees with the Board's recommendation and has plans to install vapor mitigationsystems in all homes potentially impacted by indoor air contamination (14 homes).However, the Region prefers to address vapor intrusion under its Remedial authority, as therisk is more a long term issue than imminent.
NRRB Comment 7The Region's preferred remedial alternative for indoor air consists of the installation of three
vapor mitigation systems and an indoor air monitoring program for a minimum period of fiveyears. If the Region decides to implement the air monitoring program as described to theBoard, then indoor air samples will be collected from within 14 structures overlying thegroundwater plume where it exceeds a concentration of 1,000 ug/1 perchloroethylene (PCE)in ground water. The Board suggests that the area to be considered for indoor air monitoringalso be based on concentrations of trichloroethylene (TCE) in ground water. The Boardrecommends this because the Region's indoor air preliminary remediation goals (PRGs) arebased on PCE and TCE, and the risks from TCE appear to be driving the indoor air responseaction more than PCE. The Board also recommends that the Region not define the study areatoo narrowly, considering the uncertainties in the correlation between TCE concentrations inground water and vapor concentration.
EPA Region 6 Response to Comment 7The text of the FS report was modified to provide for indoor air monitoring of structuresoverlying portions of the ground water plume exceeding PCE and/or TCE concentrations ofl,OOOug/L.
NRRB Comment 8It is unclear from the package presented to the Board whether benzene, toluene,ethylbenzene, xylene, and methyl tert-butyl ether (MTBE) are contaminants of concern forthe site, because they are related to a different source and are being addressed by NMED-Petroleum Storage Tank Bureau. Similarly, the package does not provide much informationon bromoform, but it is also identified as a contaminant of concern. The Region should beclear in decision documents whether these contaminants are actually contaminants of concernfor the site. If they are, then remedial goals addressing these contaminants should bedeveloped.
NRRB Comments and Region 6 Responses
EPA Region 6 Response to Comment 8MTBE was not identified as a contaminant of concern (COC) for site ground water withinthe Baseline Human Health Risk Assessment Report (BHHRA). BTEX compounds wereidentified as COCs for the site within the BHHRA, but the FS report discusses the fact that.the BTEX compounds are being addressed separately under the NMED Petroleum StorageTank Bureau (PSTB). BTEX compounds that are co-mingled in the chlorinated solventplume will be addressed as part of the remedy. However, Region 6 is concerned that BTEXremedial goal will not be attained in areas that are not co-mingled. Therefore no specificremedial goals have been set for BTEX.
Bromoform was identified in samples submitted to the Contract Laboratory Program (CLP)labs during the Remedial Investigation, but was not detected in split samples submitted to aseparate laboratory. Bromoform is not considered a common laboratory contaminant, but isone of three trihalomethane compounds commonly associated with water disinfectionprocesses. A determination of the presence or absence of bromoform in site ground water isanticipated during the Preliminary Field Investigation.
NRRB Comment 9The Board recommends that the cost estimates provided be reviewed and, as appropriate,revised to ensure accuracy and consistent consideration of costs in the decision documents.The following are specific concerns identified by Board members that should, at a minimum,be addressed in this cost review:
a. Ground water pump and treat costs for the three zones are shown as individualcost estimates in the package. The decision documents should also containinformation on the cost for pump and treat as a stand-alone, site-wide remedy.
. . This alternative can clarify that all ground water pump and treat costs are notcumulative; for example, the cost to install the treatment plant will not be incurreda second time if pump and treat is selected for both Shallow Ground Water PlumeCore and Deeper Ground Water.
b. The thermal treatment costs are not sufficiently itemized and appear to be low,based on the experience of other Regions.
c. The costs to conduct five-year review evaluations appear to be over-estimatedbased on the experience of other Regions.
d. The O&M for vapor intrusion remediation should not be zero, as the cost ofblower replacements should be considered.
e. It was unclear to the Board how cost of treatability studies was included.f. Costs for the ISCO alternative for the Source Area appear to be over-estimated
based on the experience of other Regions. See comment 4 on components thatmay warrant reconsideration.
EPA Region 6 Response to Comment 10The EPA has reviewed the cost estimates as recommended by the Board and has thefollowing responses to the specific concerns raised by the Board:
a. Region 6 has evaluated the pump and treat costs for the three zones as a stand-alone, site-wide remedy. However, based on site characteristics, the region didnot include this stand-alone remedial alternative in the Record of Decision.
NRRB Comments and Region 6 Responses
b. The thermal treatment costs are based on two separate vendor quotes and wereincreased based on the contractor's experience with costs for drilling in NewMexico. The vendors did not provide a detailed breakdown of costs but thecontractor has provided a more detailed cost estimated to Region 6. One potentialreason for a reduced estimated cost for thermal treatment at the GCSP site is thelow permeability of the shallow aquifer leading to a low flux of recharge waterthrough the treatment zone which otherwise create a significant cooling effect.
c. The Five-Year Review costs are comparable to other sites in the region. Theregion expects that after the first Five-Year Review subsequent review costs to belower.
d. The region has included O&M Costs for vapor mitigation systems and providedthese in the Record of Decision.
e. Treatability studies (pilot-scale tests) of applicable treatment technologies wereincluded in the estimated costs for 'Pre-Construction Activities' within thesummary cost tables provided in the FS report.
f. Region 6 has requested the experts at the National Risk Management ResearchLaboratory, Ada, OK, to review costs for the ISCO alternative in the Source Area.Any revisions to the estimated costs will be updated as part of the RemedialDesign.
NRRB Comment 10 .Based on the information presented to the Board, the Board understands that the Region hasbeen planning to implement the remedy in the primary Source Area while leaving therelatively large building housing the dry cleaner in place. Because the effectiveness of theshallow ground water remedy is dependent on thorough removal of the Source Area, theRegion should fully evaluate the effectiveness of any remedy for the area under the building.
EPA Response to Comment 10While Source Area treatment would be greatly simplified (and less expensive) without anoverlying building, the thermal treatment and the other alternatives considered in the FS areeffective even with the building in place. The region evaluated the implementation of theSource Area remedy without the dry cleaner building in place. However, cleanup can beaccomplished without removing the building. This reduces EPA costs and any hardship tothe business related to removing the building.
NRRB Comment 11The Board notes that the New Mexico soil screening guidance is not an Applicable orRelevant and Appropriate Requirement (ARAR). It might be a "to be considered" guidanceunder the National Contingency Plan for the soil cleanup itself. The Board recommends thatthe Region explain the role, if any, of the soil screening guidance in selecting soil cleanuplevels for ground water protection, where maximum contaminant levels are ARARs at thissite.
EPA Response to Comment 11Region 6 agrees that New Mexico soil screening levels (SSLs) are not ARARs, but they areTo-Be-Considered (TBC) criteria. However, NMED has clearly stated that because of the
NRRB Comments and Region 6 Responses
residential setting at the site soil cleanup should be performed to protect the public fromexposure to contaminated soil.
NRRB Comment 12The preferred alternative includes monitored natural attenuation (MNA) as a contingentremedy. However, no data were presented to the board to demonstrate that MNA isoccurring or will occur in the future; consequently, the Board cannot evaluate the
• effectiveness of MNA. However, based on the presentation and discussion at the meeting,the Board recommends that the Region consider MNA as a component of the preferredalternative which will follow active remediation rather than as a contingent remedy if theactive remedy does not work. Active remediation can be used to significantly reduce themass of contamination, with the MNA component used to achieve final cleanup levels. TheBoard recommends that the Region clarify in the decision documents how MNA may betriggered and its technical basis, consistent with Use of Monitored Natural Attenuation atSuperfund, RCRA, Corrective Action, and Underground Storage Tank Sites, OSWERDirective 9200.4-1 IP, April 21, 1999.
EPA Response to Comment 12Region 6 will evaluate the site conditions to determine if monitored natural attenuation(MNA) is a viable remedial alternative during the Five-Year Review reporting period. Oncesource control has been established in the source areas and Shallow Ground Water Plumedata indicates evidence of MNA, EP.A, with NMED concurrence, may switch from the activeremedy to MNA for the Shallow Ground Water Periphery and Deeper Ground WaterPlume. The ROD for the site documents the stated language.
NRRB Comment 13The.Board notes that one of the costs associated with site cleanup appears to be payment ofState tax on engineering services. The Board encourages the Region's efforts in workingwith the State to reach agreement on issues involving a waiver of this tax. The Boardrecommends for this situation that the Region ensure that the New Mexico tax be handled ina manner that is consistent with the Agency's ongoing cost management initiative.
EPA Response to Comment 12Comment noted. Region 6 will continue to pursue relief from the tax where appropriate withthe New Mexico Department of Taxation and Revenue regulations.
Region 6 thanks the NRRB for the recommendations and appreciates the value it bringsto the Superfund Program. Please call me at (214) 665-6701 should you have any questions.
cc: M. Cook (OSRTI)E. Southerland (OSRTI)S. Bromm (OSRE)
' J. Woolford (FFRRO)Rafael Gonzalez (OSRTI)NRRB members
NRRB Comments and Region 6 Responses