Prepared for National Aeronautics and Space Administration ... · estimated by EVS model, based on...

Final

Interim Record of Decision

Interim Action Project for Source Area 13Operable Unit 3

Prepared for

National Aeronautics and Space AdministrationMarshall Space Flight Center

Huntsville, AlabamaEPA ID# AL 1800013863

CERCLIS ID# AL7210020742

July 2007

10450094

Contents

Preface vAcronyms viiAuthorizing Signatures ix

1. Declaration 1-11.1 Site Name and Location 1-11.2 Statement of Basis and Purpose 1-11.3 Assessment of the Site : 1-11.4 Description of the Selected Remedy 1-21.5 Statutory Determinations 1-61.6 Data Certification Checklist 1-6

2. Decision Summary 2-12.1 Site Name, Location, and Description 2-12.2 Site History and Enforcement Activities 2-12.3 Highlights of Community Participation 2-72.4 Scope of SA-13 Interim Action 2-82.5 Summary of Site Characteristics ! 2-8

2.5.1 Hydrogeology 2-92.5.2 Nature and Extent of Contamination 2-102.5.3 Conceptual Site Model 2-11

2.6 Current and Potential Future Land Use Resources 2-152.7 Interim Remedial Action Objectives .: 2-152.8 Principal Threat Wastes 2-162.9 Summary of Site Risks ; 2-162.10 Description of Alternatives 2-182.11 Summary of Comparative Analysis of Alternatives 2-192.12 Selected Interim Remedy 2-19

2.12.1 Thermal Process Approach 2-212.12.2 Target Treatment Zone 2-212.12.3 IRA Configuration 2-222.12.4 Treatment System 2-272.12.5 In-situ Passive Flux Meters 2-322.12.6 System Installation 2-322.12.7 Startup Testing 2-322.12.8 System Operation and Monitoring 2-322.12.9 Post-IRA Monitoring and Land Use 2-33

2.13 Statutory Determinations 2-332.14 Explanation of Significant Differences 2-34

MGM07-NASA/IROO/001.00C

CONTENTS (CONTD)

3. Responsiveness Summary 3-1

4. References 4-1

AppendixA: Transmittal Letters and Responses to Comments

Tables1-1 IRAGS for Subsurface Soil 1-21-2 IRAGS for Residuum Groundwater 1-31-3 IRAGS for Bedrock Groundwater 1-41-4 Data Certification Checklist 1-72-1 Maximum Contaminant Levels Detected Since Pilot Test Completion 2-112-2 Summary of IRAOs 2-162-3 Groundwater COPC Comparison to MCLs or PRGs 2-172-4 Soil COPC Comparison to SSL 2-182-5 Comparison of Remedial Alternatives 2-20

Figures1-1 Conceptual Overview of ISTD System Components 1-62-1 SA-13 Site Location Map 2-32-2 SA-13 3D Model of TCE in Soil and Groundwater 2-52-3 Conceptual Site Model SA-13 2-132-4 Test Cell Conceptual Cross Section.... : 2-232-5 Conceptual Target Treatment Zone - Plan View 2-252-6 Vapor Pressure as a Function of Temperature for Select Metals 2-292-7 Expected Operation Schedule and Duration of Treatment System 2-33

MGM07-NASA/1ROD/001 .DOC

• Preface•

This Record of Decision (ROD) for an Interim Action for Source Area 13 (SA-13) at theNational Aeronautics and Space Administration's (NASA's) Marshall Space Flight Center(MSFC), Huntsville, Alabama, was prepared in accordance with requirements under theComprehensive Environmental Response, Compensation, and Liability Act of 1980 asamended by the Superfund Amendments and Reauthorization Act of 1986,42 United StatesCode Section 9601 et seq., and the National Oil and Hazardous Substances PollutionContingency Plan (NCP) (40 Code of Federal Regulations 300). The interim ROD documentsthe selected interim remedy for SA-13. Information in this document summarizesinformation from the Administrative Record, including the focused feasibility study andproposed plan for the interim action project.

MGM07-NASA/1ROD/001 .DOC

Authorizing Signatures

QAnn R. McNair[DirectorOffice of Center Operations

Gerald HardyChief of Land DivisionAlabama Department of tnvironmental Management

^Franklin E. Hill77" Director

Superfund DivisionU.S. Environmental Protection Agency

MGM07-NASMROIWOI DOC

Acronyms

ADEMARARbgs°CCERCLA

CERCLIS

CFRC02

COCCOPCCSMCVOCCYDADAFDNAPLEPAEVSFFAFSFFSftft2

ft/dayGACH2O2HRIRAIRAGIRAQIRODISCOISTDMCLMSFCug/LMgAgmg/LNASANCP

Alabama Department of Environmental ManagementApplicable or relevant and appropriate requirementBelow ground surfaceDegrees CelsiusComprehensive Environmental Response, Compensation, andLiability ActComprehensive Environmental Response, Compensation, andLiability Act Information SystemsCode of Federal RegulationsCarbon dioxideContaminant of concernContaminant of potential concernConceptual site modelChlorinated volatile organic compoundCalendar yearDepartment of ArmyDilution attenuation factorDense non-aqueous phase liquidU.S. Environmental Protection AgencyEnvironmental Visualization System®Federal Facilities AgreementFeasibility StudyFocused Feasibility StudyFeetSquare feetFeet per dayGranular-activated carbonHydrogen peroxideHydrogeologic regimeInterim remedial actionInterim remedial action goalInterim remedial action objectiveInterim Record of DecisionIn-situ chemical oxidationIn-situ thermal desorptionMaximum contaminant levelMarshall Space Flight CenterMicrograms per literMicrograms per kilogramMilligrams per literNational Aeronautics and Space AdministrationNational Oil and Hazardous Substances Contingency Plan

MGM07-MASA/1ROD/001 .DOC VII

ACRONYMS (CONTD)

NPLO&MOUPFMPPPRGPTSMRD/RARIRODRSASARASIDSSLSATCTCETTZVOC

National Priorities ListOperation and maintenanceOperable unitPassive flux meterProposed PlanPreliminary remediation goalPrinciple threat source materialRemedial Design/Remedial ActionRemedial InvestigationRecord of DecisionRedstone ArsenalSuperfund Amendments and Reauthorization Act of 1986State indirect dischargeSoil screening levelSource areaThermocoupleTrichloroetheneTarget treatment zoneVolatile organic compound

VIII MGM07-NASA/1ROD/001 .DOC

1. Declaration

1.1 Site Name and LocationNational Aeronautics and Space Administration (NASA)

Marshall Space Flight Center (MSFC)

Source Area (SA) 13 (north of Building 4705)

Marshall SFC, AL 35812

1.2 Statement of Basis and PurposeThis Interim Record of Decision (IROD) presents the selected interim remedial action (IRA)for groundwater SA-13, a site located just north of Building 4705 in the northwesternportion of MSFC. The interim action was chosen in accordance with the ComprehensiveEnvironmental Response, Compensation, and Liability Act of 1980 (CERCLA), as amendedby the Superfund Amendments and Reauthorization Act (SARA) of 1986,42 United StatesCode Section 9601 et seq., and the National Oil and Hazardous Substances PollutionContingency Plan (NCP) (40 Code of Federal Regulations [CFR] 300).

The IROD is based on the administrative record for MSFC, which includes a focusedfeasibility study and proposed plan (FFS/PP) for the SA-13 interim action project (NASA,2007) and other documents in the administrative record file for this area.

This document is issued by NASA as the lead agency for environmental restorationactivities at MSFC. The U.S. Environmental Protection Agency (EPA) Region 4 and theAlabama Department of Environmental Management (ADEM) are supportive agencies asparties of the Federal Facility Agreement (FFA) for this interim response action, and concurwith the selected remedy.

1.3 Assessment of the SiteRemedial investigations (RIs) in the area show a trichloroethene (TCE)-dominatedcontamination plume in the groundwater originating under the northwestern portion ofMSFC. TCE historically has been used as a solvent for degreasing and cleaning of partsduring industrial operations throughout MSFC. There are no current users of thegroundwater. However, the unsaturated soil, along with the saturated portion of thesubsurface soil beneath SA-13, is contaminated with TCE. These TCE-contaminated soilsserve as a continuing source of contamination to the dissolved-phase groundwater plumeand pose a risk to its remediation. In addition, there are downgradient springs that areknown to be primary points of discharge for the contaminated groundwater from thenorthwestern plume area of MSFC (including the SA-13 area) that may pose ecosystemrisks.

MGM07-NASA/1ROO/001.DOC 1-1

1. DECLARATION

1.4 Description of the Selected RemedyThis IRA fits into the overall NASA cleanup strategy by addressing soil and groundwatercontaminated with chlorinated volatile organic compounds (CVOCs) such as TCE. Interimremedial action objectives (IRAOs) were developed in the FFS/PP (NASA, 2007) anddescribe what the proposed interim action is expected to accomplish. Interim remedialaction goals (IRAGs) also were developed for this IRA to identify how meeting the IRAOswill be measured and evaluated (NASA, 2007). The IRAGs (and IRAOs) are provided inTables 1-1 through 1-3 for the contaminants of potential concern (COPCs) at SA-13. Asdiscussed in Section 2.9, the COPCs were identified by comparing sample results against theapplicable regulatory criteria for soil and groundwater, and identifying constituentconcentrations that exceeded those criteria. The COPCs for groundwater include somevolatile organic and metallic constituents that did not exceed the applicable regulatorycomparative criteria for subsurface soils.

Table 1-3 reflects two IRAG options corresponding to the two IRAOs for the bedrockgroundwater. It is possible (but not currently known) that some of the contamination willoccur in the upper portions of the bedrock included in the target treatment zone (TTZ). So,a percent reduction IRAG option was also included for the bedrock groundwater, as well asan option of meeting the maximum contaminant levels (MCLs) or the preliminaryremediation goals (PRGs) (as applicable) for the COPCs.

TABLE 1-1IRAGs for Subsurface SoilNASAMSFCSA-13IROD

COPCs IRAG OptionsSource (Literature, Bench

Scale Study, etc.) What Will Be Measured or Evaluated?

Trichloroethene (TCE)Perchloroethene (PCE)cis-1,2-dichloroethene

(cis-1,2-DCE)1,1,2-trichloroethane

(1,1,2-TCA)Carbon tetrachlorideChloroform

^ 80% reductionin estimatedmass, andaverageconcentrations, intarget treatmentzone(TTZ)

Technology vendorexperience; professionaljudgment

1. Reduction in pre- and post-treatmentmass estimates of COPCconcentrations in TTZ interval, asestimated by EVS model, based ondata results from subsurface soilsample depth intervals collected at thebeginning and end of the action and atprescribed depths and locations.

2. Reduction in pre- and post-treatmentaverage total VOC concentrations,based on subsurface soil samplescollected at the beginning and end ofthe remedial action at prescribeddepths and locations in the TTZ.

3. Evaluate the change in relative VOCcomposition of the pre- and post-subsurface soil data.

Notes:IRAQ subsurface soils = solvent-based contaminant mass reduction; reduction in solvent-based contaminant flux togroundwater systemIRAG = Interim remedial action goalEVS = Environmental Visualization System®COPC = Contaminant of potential concernVOC = Volatile organic compound

1-2 MGM07-NASA/IROD/001 .DOC

1. DECLARATION

TABLE 1-2IRAGs for Residuum GroundwaterNASA MSFCSA-13 /ROD

COPCs IRAG OptionsSource (Literature, Bench

Scale Study, etc)What Will Be Measured or

Evaluated?

Trichlorpethene (TCE)Perchloroethene (PCE)cis-1,2 dichloroethene


(1,1,2-TCA)1,1-dichloroethene

(1,1-DCE)

1,2-dichloroethane(1,2-DCA)

Carbon tetrachlorideChloroformBenzeneEthyl benzeneToluene

£ 80% reductionin estimatedmass, andaverageconcentrations, intarget treatmentzone(TTZ)

Technology vendor experience;professional judgment

1. Reduction in pre- and post-treatment mass estimates ofCOPCs in TTZ interval, asestimated by EVS model, based ondata results from residuumgroundwater samples collected atthe beginning and end of the actionat prescribed depths and locations.

2. Reduction in pre- and post-treatment average total VOCconcentrations, based on residuumgroundwater samples collected atthe beginning and end of the actionand at prescribed depths andlocations.

3. Reduction in pre- and post-treatment mass flux of VOCs inresiduum groundwater portion ofTTZ, as estimated by dataevaluation from passive fluxmeters.

Iron (Fe)Manganese (Mn)Arsenic (As)Chromium (Cr)

Evaluatetreatment systemeffects on thedistribution in thegroundwatersystem

MNA guidance; professionaljudgment

1. Relative changes in pre- and post-concentrations and distribution inthe groundwater system.

Notes:IRAQ residuum GW = solvent-based contaminant mass reduction; reduction in solvent-based contaminant flux to dissolvedGW plumeIRAG = Interim remedial action goalEVS = Environmental Visualization System®COPC = Contaminant of potential concernVOC = Volatile organic compoundMNA = Monitored natural attenuation

MGM07-NASA/IROD/001 .DOC 1-3

1. DECLARATION

TABLE 1-3IRAGs for Bedrock GroundwaterNASAMSFCSA-13IROD

COPCs IRAQ OptionsSource (Literature, BenchScale Study, etc) What Will Be Measured or Evaluated?

Trichloroethene (TCE)Perchloroethene (PCE)cis-1,2-dichloroethene



(1,1-DCE)1,2-dichloroethane

(1,2-DCA)Carbon tetrachlorideChloroformBenzeneEthyl benzeneToluene

2 80% reductionin estimatedmass, aridaverageconcentrations, intarget treatmentzone (TTZ)

Professional judgment If groundwater is encountered in theupper bedrock interval of the treatmentzone:

1. Reduction in pre- and post-treatmentmass estimates of COPCs in TTZinterval, as estimated by EVS model,based on data results from bedrockgroundwater samples collected at thebeginning and end of the action atprescribed depths and locations.

2. Reduction in pre- and post-treatmentaverage total VOC concentrations,based on bedrock groundwatersamples collected at the beginningand end of the action and atprescribed depths and locations.

3. Reduction in pre- and post-treatmentmass flux of VOCs in bedrockgroundwater portion of TTZ, asinterpreted by data evaluation frompassive flux meters and othermeasurements in residuumgroundwater.

Trichloroethene (TCE)Perchloroethene (PCE)cis-1 ,2-dichloroethene

(cis-1 ,2-DCE)1 ,1 ,2-trichloroethane


(1,1-DCE)1 ,2-dichloroethane

(1,2-DCA)Carbon tetrachlorideChloroformBenzeneEthyl benzeneTolueneArsenic (As)Chromium (Cr)Iron (Fe)Lead (Pb)Manganese (Mn)Nickel (Ni)

5 pg/L MCLs or PRGs (where no 1 . Relative changes in pre- and post-5 ug/L MCL exists). concentrations and distribution in70 ug/L groundwater system.

5 ug/L

7pg/L

5 M9/L

5 M9/L80 M9/L5 M9/L

700 ug/L1 ,000 pg/L

10 ug/LlOOpg/L300 ug/L15 ug/L50 ug/L73 (jg/L


1. DECLARATION

TABLE 1-3IRAGs for Bedrock GroundwaterNASAMSFCSA-13IROD

Source (Literature, BenchCOPCs IRAG Options Scale Study, etc) What Will Be Measured or Evaluated?

Vanadium (V) 25.5 M9/LTotal dissolved solids 500 mg/L

(IDS)

Notes:Note: IRAQ u«drockGw = solvent-based contaminant mass reduction in the bedrock treatment zone (upper 5 to 10 ft);reduction in solvent-based contaminant flux to dissolved groundwater plume in the upper bedrock groundwater flowsystem.IRAG = Interim remedial action goalEVS = Environmental Visualization System®COPC = Contaminant of potential concernVOC = Volatile organic compoundug/L = Micrograms per litermg/L = Milligrams per literMCL = Maximum contaminant limitPRO = Preliminary remedial goal

NASA has evaluated potential remedial alternatives and selected in-situ thermal desorption(ISTD) to accomplish a reduction in solvent contamination on the basis of its ability toremove volatile organic compounds (VOCs) from the soil and groundwater and to meet theIRAGs (NASA, 2006). ISTD is a physical process that entails heating the subsurface tovolatilize contamination from a liquid phase to a vapor phase, followed by capture andtreatment of the vapors. On the basis of the information currently available, this alternativeprovides the best opportunity for removing VOC mass from the subsurface. Thisalternative is expected to: 1) be protective of human health and the environment; 2) meetthe IRAGs for VOC removal; 3) use permanent solutions and alternative treatmenttechnologies to the maximum extent practicable; and 4) meet CERCLA requirements forimplementing IRAs. The site field work to implement this IRA currently was scheduled tobegin implementation during the fourth quarter of 2006, and will not be implemented laterthan 15 months after approval of this IROD, as required by CERCLA.

Figure 1-1 is a general schematic showing the ISTD process that will be applied, for theSA-13 IRA project. This process consists of a power delivery system, wellfield heaters,groundwater extraction wells, monitoring wells, soil borings, and the vapor extractionsystem, which includes a piping network and fluids treatment system. The ISTD systemand ancillary treatment train generally will be automated, with operators overseeing thesystem and collecting data and samples during the daytime. As the site is heated, fluids areextracted, cooled, separated, and treated. The subsurface process is monitored usingtemperature and pressure sensors and detailed sampling and analysis of subsurface fluids.

MGM07-NASA/IROD/001.DOC 1-5

1. DECLARATION

Treated vapor toatmosphere

Temperature and pressuremonitoring holes

Groundwaterextraction wells

Liquid transportedto Building 4761for Treatment

FIGURE 1-1Conceptual Overview of ISTD System ComponentsNASAMSFCSA-13IROD

1.5 Statutory DeterminationsThis IRA is protective of human health and the environment and is cost-effective. Thisaction complies with federal and state applicable or relevant and appropriate requirements(ARARs), with the exception of compliance with the groundwater MCL levels, which isbeing waived. Although this IRA is not intended to fully address the statutory mandate forpermanence and treatment to the maximum extent practicable, this interim action does usetreatment and thus supports that statutory mandate. Because this action does not constitutethe final remedy for NASA MSFC, the statutory preference for remedies that reduce toxicity,mobility, or volume as a principal element, although partially addressed in this remedy, willnot be satisfied by this IRA. Subsequent actions that fully address the groundwater andassociated subsurface soil contamination at NASA MSFC will be developed as part of theoverall OU-3 RI, Feasibility Study (FS), and remedial implementation program.

1.6 Data Certification ChecklistTable 1-4 lists the data included in this IROD and their respective locations. The purpose ofthis table and the data list is to certify the information that has been included in this IROD.

t-6 MGM07-NASA/1ROD/001 .DOC

1. DECLARATION

TABLE 1-4Data Certification ChecklistNASAMSFCSA-13IROD

Data Location in IROD

COPCs and their concentrations

Risk provided by the COPCs

Cleanup levels for COPCs

Source material threat mitigation

Current and reasonably anticipated future land use

Potential land use after implementation of the selectedremedy

Costs associated with the selected remedy

Key factors that led to the selection of the remedy

Table 2-1-Maximum Contaminant Levels DetectedSince Pilot Test Completion

Section 2.6-Summary of Site Risks

Tables 1-1 through 1-3-IRAGs for Subsurface Soil,Residuum Groundwater, and Bedrock Groundwater,respectively

Section 2.8.3-IRA Configuration

Section 2.5-Summary of Site Characteristics

Section 2.8.9-Post-IRA Monitoring and Land Use

Table 2-4-Comparison of Remedial Alternatives

Section 2.7-Summary of Comparative Analysis ofAlternatives

Notes:COPC = Contaminant of potential concernIRAG = Interim remedial action goalIRA = Interim remedial actionIROD = Interim Record of Decision


10 10 20 MILES

APPROXIMATE SCALE

Figure 1-1Facility Location Map

HnSt ^ _

2. Decision Summary

2.1 Site Name, Location, and DescriptionNASA MSFC is located in north-central Alabama and occupies 1,841 acres within the centralportion of the U.S. Department of the Army (DA) Redstone Arsenal (RSA). NASA'senvironmental management program at MSFC is under the federal CERCLA program. TheEPA waste generation identification (ID) number is AL1800013863 and the nationalSuperfund electronic database ID number (CERCLIS) for the facility is AL7210020742. Asindicated in Section 1.2, NASA is the lead agency for funding and implementingenvironmental restoration at MSFC, with ADEM and EPA in supportive roles under theFFA.

NASA has defined operable units (OUs) for MSFC as part of the CERCLA process. OU-3has been designated for all groundwater beneath the facility area. A draft OU-3 RI WorkPlan (NASA, 2005) has been submitted for agency review, and the RI phase for OU-3continues. In general, five major plumes of dissolved groundwater contamination existbeneath MSFC. The plumes largely consist of CVOCs, with TCE being a significant andcommon constituent in the plumes. TCE historically has been used as a solvent fordegreasing and cleaning parts during industrial operations throughout MSFC. The RIresults also indicate that the plumes probably are emanating from 14 main SAs wherecontaminants formerly were released to the environment.

As described in more detail in Section 2.5, the subsurface environment beneath MSFCconsists of a clayey residuum. The residuum is a geologic unit formed by the naturalweathering of the underlying fractured limestone bedrock. Groundwater can occur in boththe residuum and bedrock.

The general presence of a "hot spot" in residuum groundwater concentrations of CVOCsbeneath the area north of Building 4705 (location of SA-13) first became evident during theinitial phases of the OU-3 RI. In particular, the "outside-in" sampling approach showed thatthe highest concentrations of groundwater contamination (primarily TCE) occurred in thegeneral vicinity of a small concrete pad area located outside and just north of Building 4705(Figures 2-1 and 2-2).

2.2 Site History and Enforcement ActivitiesMSFC is located within RSA on a site previously occupied by the DA. In May 1994, EPAadded RSA to the National Priorities List (NPL) under the CERCLA program. MSFC wasincluded in the area of RSA listed on the NPL.

MSFC is NASA's principal propulsion development center. Its scientists and engineershave developed the propulsion systems for the engines used during the Mercury Programthrough the Space Shuttle Main Engine development efforts. MSFC also has developednumerous satellites, launch pad swing arms and hold-down bars, the lunar rover, the

MGM06-NASA/1ROD/001.DOC 2-1

The estimated 10,000 ug/l contour is only anapproximation. The extent of contaminationthroughout the area will be estimated as partof the remedial investigations for Operable Unit 3.

Approximate Extent ofInterim Remedial ActionArea (Including FormerConcrete Pad)

Approximate Extent ofTarget Treatment Zone

Legend

Upper Saturated Residuum GreundwatarTCE Concentration (ug/I)

1-10

Lower Saturated Rnlduum GroundwaterTCE Concentration (ugff)

10-100

\_f 100 -1,000

1,000-10.000

10-100

(_) 100 -1.000

1.000- 10.000

10.000-1.000.000

CH BuHflngs10.000-1.000,000

Rnads & SktewatoShallow Stormwater Drainages

• Map Area LA /"

Marshall Space Flight Center

Figure 2-1SA-13 Site Location MapNASA MSFC SA-13 (ROD

3 Document: (GAmaps\OU5\SA-13\P»o(06tou5_SA13_Rlo<Map.mxd)

1OO,OOO ppb

1O.OOO ppb

1,OOO ppb

1OO ppb

NOTE: 3D Model Orientedto Southwest

TCE above 1,000 ppbin soils and groundwater within the TTZ.

10O.OOO ppb

1O.OOO ppb

1,000 ppb

1OO ppb

NOTE: 3D Model Orientedto Southwest

TCE above 10,000 ppbin soils and groundwater within the TTZ.

23-MAY-2006Drawn By:

D. Scott Stevens

Figure 2-2SA-13 3D Model of TCE in Soil and GroundwaterNASA MSFC SA-13 IROD

2. DECISION SUMMARY

laboratory module of the International Space Station, and the Hubble Space Telescope.NASA recently finished the construction of a new propulsion laboratory for developing andtesting the newest propulsion system innovations at MSFC. Its scientists, engineers, andsupport personnel continue to play a major role in the National Space TransportationSystem by managing space shuttle mission activities, including the microgravity laboratory.

In addition, MSFC will be a significant contributor to several of NASA's future programs,including the International Space Station and Crew Launch Vehicle development, as well asresearch on a variety of space science applications.

The groundwater plumes exist throughout a large portion of the NASA MSFC facility.Because of the complex subsurface environment (see Section 2.5), the groundwatercontamination probably affects adjacent areas of RSA. NASA RIs of the groundwatercontamination have been ongoing since the late 1990s and additional RI activities currentlyare underway to evaluate the nature and distribution of the contamination in the sourceareas and the groundwater system. Once the RI report is approved by EPA and ADEM, anFS of remedial alternatives will be conducted as part of the final remedy selection for OU-3.Additionally, an IROD should be in place for OU-3 by the end of calendar year (CY) 2007that outlines the measures to be implemented as a means of ensuring protection of humanhealth at the facility until final remedies for OU-3 are identified, selected, and implemented.NASA is evaluating other interim actions that also may be implemented at the facility.More specifically, at SA-13, releases from a former drum storage area resulted in a TCE-based contaminant SA where use of in-situ chemical oxidation (ISCO) technology was notsuccessful in reducing contaminant levels. Additional information about the SA-13 area andconditions is presented in Section 2.5.

The FFS/PP for this project evaluated potential interim actions in accordance with therequirements of CERCLA and NCP. The document presented NASA's determination thatthe ISTD action is necessary and solicited public comment on that determination. Section 3of this IROD, the "Responsiveness Summary," documents public comments and NASA'sresponses to those comments.

2.3 Highlights of Community ParticipationThe FFS/PP for the SA-13 IRA project was released for public comment on April 1, 2007.The notice of the availability of the plan and other documents in the administrative recordwas published in The Huntsville Times. The administrative record file contains thedocumentation NASA considered in selecting the IRA for SA-13. These files are available atthe following locations:

Marshall Space Flight Center Redstone ArsenalNASA Public Affairs Office Redstone Arsenal Scientific LibraryBuilding 4200 Building 4484MSFC, AL 35812 Redstone Arsenal, AL 35898


2. DECISION SUMMARY

Huntsville/Madison County Public Library Triana Public LibraryReference Department . . Triana Youth Center ,915 Monroe Street 280 Zierdt RoadHuntsville, AL.35801 Triana, AL 35758

The 30-day public comment period for the proposed plan was April 2 through March 4,2007. NASA received no public comments (either verbally or in writing) on the documentand received no written requests for a public information session. Accordingly, the FFS/PPwas finalized and placed into the document repositories per the NASA CommunityRelations Plan.

2.4 Scope of SA-13 Interim ActionThis IROD addresses only the "hot spot" of contaminated subsurface soil and groundwateridentified at SA-13. Future CERCLA activities will be conducted for OU-3 in associationwith other interim, early, and/or final actions. This IRA is not intended to address othercontamination sources. However, the selected interim remedy will reduce the mass ofCVOCs in the subsurface at SA-13 and reduce the contaminant flux to the dissolved portionof the overall groundwater plume and the underlying bedrock system. The IRA will beconsistent with the final remedy for OU-3 implementation.

2.5 Summary of Site CharacteristicsSA-13 is located on the northern side of Building 4705 and most of the area is unpaved.NASA completed a historical evaluation of the SA-13 area. The evaluation concluded that aconcrete pad was formerly used to store drums of oil and waste solvents (including TCEused in the Building 4705 operations) and that spills occurred. Filled drums reportedlywere removed from the pad on a routine basis. However, drums were sometimes emptiedfor re-use in the building rather than waiting for delivery of new empty drums. Drumcontents were released to the land surface by running off the pad onto the immediateunpaved areas, released to the immediate unpaved areas, and/or were released throughleakage via small cracks in the pad. There were no records or information as to the numberof drums that were stored, emptied, or managed; the released volumes; or the time periodover which the pad was used for this purpose. The pad area is no longer used for drumstorage. Currently, no specific activities are being conducted in the area; however, the landuse is classified as industrial at SA-13, and there are no future plans to change this land useclassification along the northern side of Building 4705.

The concrete pad area formerly used to store drums of waste oil and TCE is connected to thebuilding by a concrete walkway. The surface topography of the area slopes to a lowerelevation toward the north to a shallow storm water ditch. This ditch channels storm waterthrough a culvert, under a road, and into a storm drain. The surface soils in the SA-13 areahave been designated as CERCLA site MSFC-094 and are being addressed in OU-5.

The upper portions of the subsurface profile are composed of weathered, relatively low-permeability clayey media, termed the residuum. This hydrostratigraphic unit is underlainby carbonate bedrock formations that compose the Tuscumbia-Ft. Payne Aquifer, which

2-8 MGM07-NASA/IROD/001.00C

2. DECISION SUMMARY

contains a karst flow path network. The bedrock occurs at depths from about 34 to 37 feet(ft) beneath ground surface (bgs) beneath SA-13. The groundwater-bearing portions of theresiduum and karst bedrock units form a complex, integrated groundwater system. Thedegree of hydraulic interconnection and vertical interchange of water between the units areboth spatially and temporally variable throughout MSFC. .

Two phases of ISCO pilot testing were completed in 2000 using a stabilized hydrogenperoxide (HaOz) and a proprietary iron catalyst solution. ISCO involves creation of asubsurface chemical reaction resulting from the injection of an oxidant to degrade organiccontaminants, producing carbon dioxide and water as by-products. The results indicatedlimited effectiveness in the overall reduction of TCE concentrations and mass. Given thereported treatment potential of ISCO technology, a decision was made to change the processand to conduct a third test phase. Phase in was completed in November 2002 using H2O2,following the addition of phosphoric acid for groundwater pH adjustment to increasereaction rates. The third phase also was preceded by pneumatic fracturing of theunsarurated subsurface soils to improve reagent delivery and distribution.

In summary, the results indicated that the injection phases had limited effectiveness inreducing TCE levels in the subsurface soil. Some localized reductions in groundwaterconcentrations were observed, but the TCE concentrations significantly increased upon thecompletion of the ISCO study; "rebound effects" were evident.

2.5.1 HydrogeologyGroundwater flow systems exist in regional, intermediate, and local subsurface basins, asdefined by a series of integrated subsurface and hydraulic influences. The basin systemsoccur in four defined hydrogeologic regimes (HRs), as described in the Conceptual Site Modelfor Redstone Arsenal and NASA MSFC, Madison County, Alabama (Redstone Arsenal andNASA, August 2004). The MSFC area lies in HR-1, which generally is dominated by thevertical flow conditions in the residuum, the increased prevalence of karst features alongbedding planes and other solution features in the upper bedrock intervals, and a generaldecrease in the frequency and size of karst features with depth. Groundwater from thebasins eventually discharges as diffuse seepage, and/or through springs that exist in thedowngradient surface water systems and were created by the impoundment of theTennessee River. Temporal (including seasonal) changes in the hydraulic interactionbetween the groundwater and surface water systems occur because of variations in watersurface elevations in the Wheeler Lake system.

Site characterization efforts for the SA-13 area included the completion of a karst assessmentusing surface and borehole geophysical methods. The assessment concluded that variationsin the bedrock surface beneath the area are generally gradual, with limited evidence tosuggest the presence of a closely spaced cutter/pinnacle weathered surface. The results didnot identify significant karst features at observed anomalies and concluded that if they arepresent, then they are localized and not laterally extensive. These results, along with theother site characterization data, are important elements of the site-specific conceptual sitemodel (CSM) (Section 2.5.3) and emphasize the importance of considering the localresiduum groundwater flow regime in the immediate area.


2. DECISION SUMMARY

2.5.2 Nature and Extent of ContaminationThe nature and extent of contamination in the SA-13 project area were refined from theinitial RI indications, as part of planning and implementing the ISCO pilot test. Soil boringsand monitoring wells (residuum groundwater) were installed to refine the nature and extentof contamination within, and around, the area. This subsection summarizes contaminationlevels as they were observed following the completion of the Phase III ISCO testing(December 2002). ,

The sampling results have shown clearly that TCE is the dominant COPC beneath theproject area. Other VOCs and some metal constituents have been detected, or qualitativelyidentified, at relatively low concentrations in the residuum groundwater. The presence ofthese types of constituents is consistent with the potential contaminants that were used inthe Building 4705 operations and potentially released to the environment.

The sampling results from the post-Phase III ISCO testing provide the latest data currentlyavailable regarding the conditions beneath the SA-13 project area (Figures 2-1 and 2-2).

These data were plotted using the Environmental Visualization System® (EVS) model, assummarized below:

• The data indicate that more of the higher concentrationsXabove 10,000 micrograms perkilogram [fig/kg]) in the subsurface soil media generally occur in the western half ofthe area, with the highest levels (above 100,000 fig/kg) present in the northeasterncorner. The post-Phase III mass of TCE in the subsurface soil media was estimated to beabout 133 pounds. .

• The highest TCE groundwater concentrations (above 600,000 micrograms per liter[ug/L]) are evident in the upper portions of the saturated residuum interval. The post-Phase III mass of TCE in the residuum groundwater was estimated to be about50 pounds.

Additional and more recent data will be obtained as part of implementing theSA-13 IRA project. Table 2-1 summarizes the highest levels of TCE and other COPCsdetected in the subsurface soil and groundwater since the completion of the Phase III ISCOtesting (December 2002). The soils were sampled once since the completion of the pilot test,and MWOO-304 has been sampled on a semiannual basis.

Table 2-1 indicates the presence of some inorganic metal constituents in the residuumgroundwater. Many of the metal constituents may also exist as mineral complexes orcharged ions (and not as elemental compounds) in the residuum subsurface soil. Many ofthese inorganics (especially iron and manganese) occur under background conditions(where no obvious anthropogenic or man-made sources of contaminants have been founddirectly attributable to the concentrations) in the residuum; thus, it is possible that some ofthe reported total metals concentrations in the residuum groundwater could be related tothe turbidity of (or the amount of residuum solid particles in) the water samples. However,historical Building 4705 operations did involve the use of substances (such as chromium-

2-10 MGM07-NASA/IROO/001.DOC

2. DECISION SUMMARY

TABLE 2-1

Maximum Contaminant Levels Detected Since Pilot Test CompletionNASAMSFCSA-13IROD

Contaminant Levels

Contaminant ouusumice own \ny*HJ varounuwawr \\iyii-)

Organic Compounds

Trichloroethene (TCE)

Tetrachloroethene (PCE)

c/s-1,2-DCE(c/s-1,2-DCE)

Carbon Tetrachloride

Chloroform

Benzene

1 ,1 ,2-Trichloroethane (1 ,1 ,2,-TCA)

Inorganic Compounds

Arsenic (As)

Chromium (Cr)

Iron (Fe)

Lead (Pb)

Manganese (Mn)

Nickel (Ni)

Vanadium (V)

504,000

2.9 J

75.5

15.5

16.6

ND

9.7

NS

NS

NS

NS

NS

NS

NS

615,000

7.1

212

7.1

32.7

NO (historical max. 164)

14.3

70

368

174,000

115

15,500

598

353

Notes:pg/kg = Micrograms per kilogramug/L = Micrograms per literNS = Not sampledND = Not detectedJ = Estimated detection

based salts) that included some of the inorganic constituents detected in the residuumgroundwater.

2.5.3 Conceptual Site ModelA hydrogeologic CSM represents, in narrative and/or graphical form, the synthesis of pastobservations and information about environmental conditions at a particular site. Itexpresses the current understanding about integrated relations between the contaminantsetting, subsurface conditions, and surface drainage systems that influence the movement ofgroundwater (and associated constituents) through the environment. The CSM is dynamicand changes in accordance with new information obtained over time.

MGM06-NASA/IROD/001 .DOC 2-11

2. DECISION SUMMARY

Figure 2-3 depicts the CSM relevant to conducting the SA-13 IRA. The site-specific CSMwill continue to be evaluated and updated as additional information becomes availablefrom process and monitoring well (including bedrock) installations in the area andsubsurface construction activities during the implementation of the IRA. The maincomponents of, and key uncertainties associated with, the site-specific CSM include thefollowing:

• The SA-13 area of study interest resulted from the presence of a former drum storagearea that was located at the concrete pad near the center of the IRA project area.Contaminants were released to land surface by running off the pad onto the immediateunpaved areas, released to the immediate unpaved areas, and/or were released throughleakage via small cracks in the pad. The volume and duration of released contaminantsare unknown.

• TCE is the dominant COPC in the SA-13 project area. Over time, most of the TCEvolatilized or degraded from the upper soils, or migrated vertically, through preferentialpathways to deeper subsurface intervals, where various processes have affected theultimate fate and transport of the contaminant in the environment.

• The limestone bedrock underlying the residuum is a mildly undulating surface with nosignificant, laterally extensive karst features apparent in the immediate SA-13 vicinity.The bedrock surface generally slopes toward the SA-13 study area from the west, north,and east and then maintains a general southerly slope through the northern portion ofthe Building 4705 area. A low degree of vertical hydraulic connection is believed to existbetween the residuum and the underlying limestone bedrock beneath IRA project area.

• The remaining TCE contamination is thought to be largely contained within both theunsaturated and the saturated intervals at the base of the residuum. No appreciableamounts of dense non-aqueous phase liquids (DNAPLs) have been observed in thesubsurface media. However, groundwater TCE concentrations beneath some of thestudy area typically exceed 1 percent of the solubility of TCE (approximately1,100 milligrams per liter [mg/L]); this correlation is often used to indicate the likelypresence of DNAPLs. DNAPLs have not been directly observed in groundwater or soilsamples collected from SA-13.

• The saturated residuum interval is composed mainly of gravel and sand, withintermixed silts and clays; this interval appears to be continuous throughout the SA-13area. The average saturated thickness of this interval beneath the project area isapproximately 4.5 ft, with average hydraulic conductivity values ranging from about 9 ftper day (ft/day) in the upper portion to 75 ft/day in the lower portion of the interval.The interval serves as the primary local groundwater flow and transport pathway, withlateral groundwater flowing in response to hydraulic gradients, hydraulic characteristicsof the media, and top-of-bedrock elevations. Measured gradients indicate a generalsouth to southwesterly movement, with maximum seepage rates seasonally rangingbetween 2 and 4 ft/day. The localized groundwater flow from the SA-43 study areaeventually enters an intermediate subsurface basin system through karst features thatare located away from the immediate area.

2-12 . MGM07-NASA/IROD/001.DOC

SUMMARY OF KEY CSM UNCERTAINTIES

© Quantity of TCE used and released to the environment

© Presence of major secondary sources of contamination

© Presence of NAPL

© Vertical extent of groundwater contamination

NOTES:1. Locations and scales are approximate.

Approximate Scale in Feel

30 60

LEGEND*.

,0-3010

SA-13 Area - Plan View

Residuum Groundwater Monitoring Locations

Expected Direction of Shallow Groundwater Flow

Estimated Extent of TCE Detections

Potential Secondary Source Material

Approximate Area of Proposed Interim Action

V o

Approximate Scale in Feet•Z I100 200 SA-13 Area-Aerial View

LEGEND

Y Groundwater Level

I Monitoring WeO

= Monitoring Wei Screened= Interval

Local/lnlermedlata Groundwaler"*~~ Ftow Patlams

Former Contarnlnallnc;Discharges

Dense Non-Aqueous PhaseLiquids (DNAPLs)

Potential Secondary SourceMaterial

Diffusion In Bedrock Fractures• and Malrii

Disserved GroundwatarContamination

Background or Relatively-Uncontamlnatad Groundwater

Karat Fractures and Conduits

Residuum (Clays and Sills withLenses of Sands, Gravels)

Transitional Interval (Saturated)

Tuscumbfa-FL Payne Limestone

Approximate Top of BedrockSurface

Looking West

MWOO-304

610

•600

•590

580

•570

•560

•550

•540

•530

520

SA-13 Area - Generalized Cross-Section

RevisionsFIGURE 2-3Conceptual Site Model SA-13NASAMSFCSA-13IROD

EP022006002GNV

. 2. DECISION SUMMARY

The extent of the remaining TCE contamination in the SA-13 study area will continue to berefined and conditions understood to the extent practicable. Despite the relatively smallsize of the SA-13 project area and the close spacing between sampling locations, spatialvariability in observed contaminant levels is inherent and expected. This variability iscreated by natural heterogeneities in the residuum matrix, as well as previous in-situtreatability study testing that may have affected preferential flow (and contaminantmigration) paths and contaminant mass distribution beneath SA-13. It also is possible thatminor karst features are present in the SA-13 area.

2.6 Current and Potential Future Land Use ResourcesCurrent land use at SA-13 (as well as throughout MSFC) is classified as industrial and willretain this classification throughout the duration of NASA's occupation of the property.NASA maintains a Master Plan for the facility that manages land use consistent withNASA's missions and programs. NASA maintains a Land Use Control Assurance Plan toensure that land use controls imposed as part of remedy selections at MSFC stay in effect sothat the remedy remains fully protective of human health (and the environment, asapplicable). NASA also has an active a site access control program to protect workers andvisitors at CERCLA sites and provide centralized control of access, work activities,associated land use activities, and related construction activities (including proposedgroundwater withdrawals for dewatering or other purposes). By the end of CY 2007, NASAalso should have an IROD in place for OU-3 to preclude groundwater withdrawals forpotable (drinking water) purposes and to provide management control over all other non-potable groundwater uses and discharges throughout MSFC.

2.7 Interim Remedial Action ObjectivesIRAOs were developed in the FFS/PP (NASA, 2007) and describe what the proposedinterim action is expected to accomplish. IRAGs also were developed for this IRA toidentify how meeting the IRAOs will be measured and evaluated (NASA, 2007). The IRAGs(and IRAOs) are summarized in Tables 1-1 through 1-3 for the COPCs at SA-13.

Table 2-2 is a synopsis of the IRAOs for the specific target media in the TTZ. The IRAOsserve as a general basis of design for evaluating remedial options and understanding howrisks posed by the contaminants are addressed by the proposed action.


2. DECISION SUMMARY

TABLE 2-2Summary of IRAOsNASA MSFC SA-131ROD

Target Media Interim Remedial Action Objectives

Subsurface soils 1. Solvent-based contaminant mass reduction

2. Reduction in solvent-based contaminant flux to groundwater system

Residuum groundwater 1. Solvent-based contaminant mass reduction

2. Reduction in solvent-based contaminant flux to dissolved groundwaterplume

Bedrock groundwater 1. Solvent-based contaminant mass reduction in the bedrock treatmentzone (upper 5 to 10 feet)

2. Reduction in solvent-based contaminant flux to dissolved groundwaterplume in the upper bedrock groundwater flow system

2.8 Principal Threat WastesPrincipal threat source material (PTSM) is represented by source material contaminants(such as DNAPL-like conditions) that present an obvious potential threat to human healthand the environment, either because of the nature and extent of contamination or because alarge mass of leachable material in the ground. TCE constitutes the primary PTSM in theTTZ at SA-13 because of the elevated and dominant concentrations of this COPC; the formsin which it probably exists; and its fate and transport properties, which allow primarilydissolved phase migration into and within the groundwater system.

The proposed IRA will result in the reduction in the mobility, toxicity, and volume of thePTSM. However, it is likely that some residual contamination will remain in the TTZ afterimplementation of the IRA, and other contaminated areas exist adjacent to the TTZ. Theseareas will continue to be monitored and evaluated as part of the CERCLA RI/FS processthat will lead to decisions regarding the final remedies for OU-3.

2.9 Summary of Site RisksThe human health risks posed by the contamination beneath SA-13 are addressed below.The ecological risks associated with surface media in this area will be evaluated as part ofMSFC-094 (Building 4705 West Clean Room and North Satellite Waste Accumulation Area(including the Industrial Sewer west of Building 4705 and north of MH-105N) in OU-5.

The contamination beneath SA-13 generally has been detected at a depth beginning about18 ft bgs. An ecological risk assessment was not performed as part of this ERA because ofthe incomplete exposure pathway to ecological receptors at depths below 12 ft bgs.


2. DECISION SUMMARY

The human health risks posed by the groundwater beneath the SA-13 IRA project area areprimarily related to VOC contamination. Because the FFS/PP and this IROD are in supportof the IRA, only a streamlined risk evaluation was required; the overall OU will beaddressed in a more comprehensive, quantitative human health risk assessment thataddresses all media, the streamlined human risk evaluation involved comparingmaximum site concentrations to drinking water standards or PRGs for tap water to providea qualitative analysis of human health risks associated with future potable use of thegroundwater at this site. Table 2-3 provides the maximum concentration of COPCs in thegroundwater beneath SA-13, compared to the federal MCLs for potential drinking watersources, or the EPA Region 9 PRGs for constituents that do not have an MCL value.

TABLE 2-3

Groundwater COPC Comparison to MCLs or PRGsNASA MSFC SA-13 IROD

Contaminant



c/s 1 ,2-Dichloroethene (cis-1 ,2-DCE)

Carbon Tetrachloride

Chloroform

Benzene

1 , 1 ,2-Trichloroethane (1,1 ,2,-TCA)

Arsenic (As)

Chromium (Cr)

Iron (Fe)

Lead (Pb)

Manganese (Mn)

Nickel (Ni)

Vanadium (V)

Groundwater (ug/L)

615,000

7.1

212

7.1

32.7

ND (historical max. 164)

14.3

70

368

174,000

115

15,500

598

353 .

MCL or PRG (ug/L)

5

5

70

5

80

5

5

10

ioo

300

15

50

73

25.5

Notes:Ni and V comparison criteria are EPA Region 9 PRGs; the remainder of the parameters arecompared to the MCLs.pg/L = Micrograms per literMCL = Maximum contaminant limitPRG = Preliminary remediation goal

As listed in Table 2-3, if the groundwater were used for future potable purposes, it wouldpose unacceptable risks because the maximum concentrations detected in site groundwatersignificantly exceed the drinking water standards and screening levels.

MGM06-NASA/IROD/001 DOC 2-17

2. DECISION SUMMARY

Another risk posed by the contamination involves the teachability characteristics of the.contamination and the soil-to-ground water pathway for the contamination. The VOCsdetected in the subsurface soil were screened against the EPA Region 9 soil screening levels(SSLs) using a dilution attenuation factor of four. These results are provided in Table 2-4.

As presented in Table 2-4, the concentrations of some constituents in soils, primarily TCE,exceed the teachability criteria, indicating that site soils have the, potential to affectgroundwater; this potential is confirmed by the presence of the same compounds ingroundwater at concentrations that currently exceed the drinking water standards andguidance levels.

TABLE 24Soil COPC Comparison to SSLNASA MSFC SA-13 IROD

Contaminant



c/'s 1 ,2-Dichloroethene (cis-1 ,2-DCE)

Carbon tetrachloride

Chloroform

1 , 1 ,2-Trichloroethane (1,1 ,2,-TCA)

Soil (pg/kg)

504,000

2.9 J

75.5

15.5

16.6

9.7

SSL (DAF =4) (pg/kg)

12

12

80

12

120

3.6

Notes:pg/kg = Micrograms per kilogramSSL = Soil screening levelDAF = Dilution attenuation factorJ = Estimated detections

The comparisons noted in Tables 2-3 and 2-4 show that the contamination detected beneathSA-13 exceeds the screening criteria by orders of magnitude in some instances, and isactionable under CERCLA.

2.10 Description of AlternativesNASA considered three interim remedial action alternatives for the VOC-contaminatedmedia below the SA-13 IRA project area. These included: 1) no action; 2) ISCO; and 3) ISTD.These alternatives were included as part of the FFS/PP for the SA-13 IRA project (NASA,2007). Each alternative is summarized below:

1. No Action-The no action alternative was used for comparison purposes in the FFS. Thisalternative assumed that NASA will not implement the proposed IRA.

2. /SCO-The ISCO alternative would include pneumatically fracturing the subsurface soilto increase the bulk permeability of the matrix. Once the fracture network has beenestablished, dilute phosphoric acid would be pumped into the subsurface followed byhydrogen peroxide solution (Fenton's chemistry). These chemical reagents would be

2-18 MGM07-NASA/IROD/001.DOC

2. DECISION SUMMARY

applied in specific intervals of the subsurface on the basis of the contamination dataexisting at the time of the IRA implementation.

3. /STD-The application of heat to the subsurface acts to accelerate the mobilization offree-phase (if present) and residual contaminants present at the site. VOC removal isdominated by vaporization and distillation processes. Under elevated temperature,volatilization of VOCs is accelerated by the application of heat, resulting in the transferof the contaminant from the bulk liquid to vapor. Continuous removal of vaporprevents the vapor and liquid mixture from reaching equilibrium, thereby promotingcontinued volatilization and eventual cleanup.

As subsurface temperatures increase during heating, contaminant removal by distillationalso may occur. This process will occur when the vapor pressure of the combinedsystem is equal to one atmosphere. The boiling point of pure phase TCE under ambientconditions is approximately 87 degrees Celsius (°C); pure water under identicalconditions boils at 100°C. However, when TCE and water are mixed, the vapor pressureof the combined system allows the mixture to boil at approximately 73°C.

The physical processes previously described are the dominant removal mechanisms. Toa lesser extent, contaminant removal may be aided by secondary physical, chemical, andbiological processes that are favored by elevated temperatures.

The ISTD system includes the installation of a series of vertical wells to extractcontaminated groundwater before and during hearing, to electrically heat the TTZ, andto withdraw the vapors. The system incorporates treatment processes to control vaporphase emissions. Recovered groundwater, and condensate that forms as part of thevapor extraction-treatment process, are collected and managed separately.

2.11 Summary of Comparative Analysis of AlternativesThe preferred alternative to address the elevated VOCs beneath SA-13 is ISTD. A detailedanalysis of the alternatives in terms of compliance with the required criteria under CERCLAis included in the SA-13 FFS/PP (NASA, 2007). Table 2-5 compares the remedialalternatives to the nine evaluation criteria, as presented in the FFS.

2.12 Selected Interim RemedyThe selected interim remedy for SA-13 is ISTD. This option is believed to best accomplishthe IRAOs and IRAGs for the IRA, to be the more technically effective and reliable option,and to best meet the CERCLA requirements for implementing IRAs. While involving highercapital cost expenditures, the estimated costs for both options are essentially the same orderof magnitude; however, given the expected contaminant reduction resulting from theselected option, it should result in a significantly lower unit cost (on a dollars per pound ofcontaminant removed basis) than the other oph'on. A detailed description of the remedy isprovided in the following subsections.


2. DECISION SUMMARY

TABLE 2-5Comparison of Remedial AlternativesNASAMSFCSA-13IROD

EvaluationCriteria

Alternative 1-No Action Alternative 2-ISCO Alternative 3-ISTD

a

IO2ous

I

Protection ofHuman Health andthe Environment

Compliance withARARs

Not protective ISCO is potentially capable ofoxidizing TCE and other VOCs inmany subsurface environments andcan be protective of human healthand the environment.

Does not ISCO is potentially capable ofcomply with significantly reducing the mass ofARARs, waiver TCE and other VOCs in manyrequired subsurface environments.

However, MCLs are not likely to beachieved due to the large mass ofVOCs in the subsurface and thelikely difficulties in effectivelydelivering reagents in the TTZ atSA-13.

ISTD is capable of volatilizingVOCs from the subsurface toa vapor extraction andtreatment unit and can beprotective of human healthand the environment.

ISTD is capable ofsignificantly reducing themass of VOCs in thesubsurface. However, MCLsmay not be achieved due tothe large mass of VOCs in thesubsurface and the significantpercentage reduction requiredto achieve them. Thisalternative will result incompliance with all otherARARs.

.5

I-OO>

'oO

Reduction ofToxicity, Mobility,or Volume

Long-term Not effective Potentially effective in reducingEffectiveness VOC mass in many subsurface

environments; however, hydrogenperoxide is not stable in thesubsurface for more than a fewdays. Previous studies at SA-13showed that VOC reduction wasminimal in the long-term.

No reduction ISCO is a potentially effectivealternative for reduction in VOCmass, resulting in a lower toxicity,mobility, and volume ofcontamination in many subsurfaceenvironments. Previous studies atSA-13 showed that VOC reductionwas minimal.

Short-term Not effective ISCO exhibits potential short-termEffectiveness effectiveness in reducing VOC

mass in many subsurfaceenvironments. Previous studies atSA-13 showed some short-termVOC reduction in the lower intervalof the groundwater-bearingresiduum. ISCO technology mayrequire more than one applicationevent to achieve the desired degreeof treatment.

Effective in reducing VOCmass in the subsurface;however, MCLs may not bemet in the long-term(100 years) without theimplementation of othertechnologies.

ISTD is an effectivealternative for reduction inVOC mass, resulting in alower toxicity, mobility, andvolume of contamination.

ISTD exhibits short-termeffectiveness in reducing VOCmass.


2. DECISION SUMMARY

TABLE 2-5

Comparison of Remedial AlternativesNASAMSFCSA-13IROD

.22•coo>

EvaluationCriteria

Alternative 1-No Action Alternative 2-ISCO Alternative 3-ISTD

Implementability Easilyimplemented

Feasible to implement; requireschemical staging area and safehandling practices.

Estimated CapitalCost

$0 $457,960

Feasible to implement;requires electrical power andconversions, heating andvapor recovery equipment, airemissions control equipment,and liquid wastehandling/disposal.

$695,550

AgencyAcceptance

Not acceptable Generally acceptable to Agencies.

Public Acceptance No publiccommentssubmitted

No public comments submitted

Generally acceptable toAgencies.

No public commentssubmitted

Notes:The details for developing the costs for Alternatives 2 and 3 are provided in the SA-13 FFS/PP (NASA, 2007).ISCO = In-situ chemical oxidationTCE = TrichloroethleneVOC = Volatile organic compoundMCL = Maximum contaminant levelSA = Source AreaISTD = In-situ thermal desorptionARAR = Applicable or relevant and appropriate requirementTBD = To be determined

2.12.1 Thermal Process ApproachAn area approximately 41 ft x 26 ft in SA-13 will be heated to the boiling point of water. Assteam temperatures are reached, in-situ boiling is induced by the continued input of heat,which leads to steam formation and steam stripping of the site contaminants.

2.12.2 Target Treatment ZoneThe IRA. area covers approximately 1,066 square feet (ft2), with approximate plan viewdimensions of 41 by 26 ft. The TTZ, measuring 32 ft by 15 ft, lies within this area and isspecifically targeted for treatment by the ISTD system. The IRA area is larger than the TTZbecause the heating is expected to extend beyond the TTZ due to the thermal conductivityof the subsurface soils. The treatment depth spans approximately 15 to 42 ft bgs, extendingapproximately 5 ft into the bedrock and 12 ft above the saturated, permeable portion of theresiduum. The vertical thickness of the TTZ averages about 27 ft, depending on the

MGM06-NASA/IROO/001 DOC 2-21

2. DECISION SUMMARY

variations in bedrock elevation, saturated residuum thickness, and surface topography. Thevolume contained in the TTZ is approximately 480 cubic yards, assuming an average TTZthickness of 27 ft. A conceptual cross section of the selected TTZ is shown in Figure 2-4.

2.12.3 IRA ConfigurationA conceptual layout of wells and borings for the IRA is shown in Figure 2-5. The wells andborings are located near the pad where the TCE was released and the highest concentrationshave been detected in the subsurface. TCE constitutes the main principal threat sourcematerial (PTSM) present at SA-13 because of the elevated concentrations and its fate andtransport properties, which allow migration within the groundwater. By locating the wellsand borings in the areas of highest contamination, a reduction of mobility, toxicity, andvolume of VOCs in the soil and groundwater beneath SA-13 should be achieved. Theproposed layout consists of an inner treatment cell surrounded by extraction wells to keepthe inner area hydraulically isolated, such that contaminated fluids do not enter from theoutside during system operation. The treatment cell is equipped with several types of wellsand extraction points.

2.12.3.1 Heater WellsTo ensure complete heating, a total of 18 vertical heater borings will be installed. Theelectrical resistance heaters are controlled by thermostats that are configured to deliver auniform wattage of heat output across the target depth interval.

2.12.3.2 Fluid Extraction PointsGroundwater and vapor will be extracted from four locations, in addition to the vaporextraction points co-located with the heater wells. In addition, four existing monitoring wellswill be used for fluids extraction to control groundwater influx along the southern, eastern,and western sides of the test cell.

2.12.3.3 Process Monitoring WellsDuring the operation of the ISTD, nine process monitoring wells will be used toincrementally monitor subsurface pressure and temperature to a depth of about 5 ft intobedrock, or approximately 42 ft bgs. Tracking of heat propagation will be used to delineateareas where target heating goals are achieved; monitoring subsurface pressure gradientswill ensure control of recovered contaminant of concern (COC) vapors. Process monitoringwells will be equipped with multiple thermocouples (TCs).

2-22 MGM07-NASA/IROD/001.00C

2. DECISION SUMMARY

CW03-010 . CW03-020

CW03-040.C WO 3-0 30

565-

LEGEND

Approximate Extant of TTZ I

Not to Scab

RGURE2-4Test Cell Conceptual Cross SectionNASAMSFCSA-13IROD

Note:A. Well locations are approximate. Final locations will bedetermined during final system design.

B. System wells may serve multiple functions during pilot test.Expected applications will be tabulated as part of the final design.

C. Specific well Identifications for final locations will be providedIn a drawing, as part of the O&M manual submlttal.

BUILDING\S-4703 j

ABANDONED UNE-(1 1/2" NITROGEN LINE

77%

BUILDING^S-4705

«. -II WATER HYDRANT

\

CW03-022<:wbVoz>

\

Approximate Extentof Study Test Cell

--£ ** • OV03-031®': &~~

/*-<•

CONCRETE PAD

/'— Approximate Extent of

Target Treatment Zone

I/

CONCRETEPAD

GAS"CHILLER

LINES

TRANSFORMERAREA

DROP INLET

CONCRETE PAD

BRASS MONUMENTN = 1512594.055E= 402604.4026EL = 606.03

LEGEND9 = MONITORING WELLO = BRASS MONUMENT» = WATER LINES

—Q — = ELECTRICAL LINES- as - = NATURAL GAS LINES--•=.- = CHILLER LINES

= NITROGEN GAS LINES (ABANDONED)= TARGET TREATMENT ZONE

;;.-;..: = STUDY TEST CELL8 = NEW HEATER BORING• = NEW HEATER BORING WITH VAPOR EXTRACTION SCREEN

8 = NEW PROCESS MONITORING WELL (TEMP, PRESSURE, COC)= NEW PROCESS MONITORING WELL (TEMP, PRES., COC, PFM)

® = EXISTING WELL FOR EXTRACTION© = EXISTING WELL FOR GROUNDWATER MONITORINGX = NEW BEDROCK MONITORING WELL

APPROXIMATE SCALE10 Q f 10

(IN FEET)1 INCH " 20 FT.

RevisionsFIGURE 2-5Conceptual Target Treatment Zone - Plan ViewNASAMSFCSA-13IROD

EP022006002GNV

2. DECISION SUMMARY

2.12.3.4 Groundwater Performance Monitoring Wells

Monitoring locations include six existing residuum wells, in addition to two bedrockgroundwater monitoring wells. These will be sampled before and after treatmentoperations as part of the performance assessment.

2.12.4 Treatment SystemThe extracted fluids include air, contaminant vapors, and steam at varying temperaturesand pressures; a robust combination of unit operations is required to treat these processstreams. Groundwater and vapor extracted from the test cell will be cooled, separated, andtreated.

Vapor not condensed in the compression-chiller subsequently will be treated by adsorptiononto granular activated carbon (GAC). Treated vapor from the carbon beds will bedischarged to the atmosphere and monitored for compliance with local and stateregulations. A completed ADEM Form 448 (dated August 2002) for the remediation systemwill be submitted to the ADEM Air Branch for approval before the IRA is initiated.

Liquid condensate accumulated in the knock-out tank and compression-chilling system willbe transferred by pump to liquid phase GAC treatment units, where contaminants will beremoved. The treated water will then be stored onsite in a holding tank; a vacuum truckwill be used to periodically empty the site tank. Treated water collected from the SA-13 IRAwill be transferred by truck to the site industrial wastewater treatment plant atBuilding 4761. Building 4761 is equipped with an air sparging system that will further treatthe recovered liquids from the SA-13 IRA project. The treated water will then be dischargedto the sanitary sewer from Building 4761 per NASA's State Indirect Discharge (SID) permitand will undergo additional treatment at the DA's sewage treatment plant.

As discussed in Section 2.5.2, concentrations of several total metals have been detected inthe residuum groundwater beneath the IRA area. These metal constituents have beendesignated as COPCs for the groundwater (Section 2.9). Although some of the metals occurnaturally within the residuum, it is possible that former Building 4705 activities could haveresulted in releases of some metal-containing wastes and affected groundwater in the TTZbeneath the IRA area.

Groundwater extraction will occur as part of the treatment process. This liquid wastestream will contain both organic and inorganic constituents and will be managed separately,as described above.

The steady-state temperatures of the operating treatment system are expected to be around100°C. This temperature is significantly below those required to mobilize even volatile,elemental forms of the metals (if they existed in this state, which they do not) from thesubsurface soils into the vapor phase waste stream generated by treatment systemoperations. More information supporting this general conclusion is provided below.

MGM06-NASA/1ROD/001.DOC 2-27

2. DECISION SUMMARY

Because the heater assemblies are capable of generating high temperatures, vapor pressuredata for elemental forms of the identified metal COPCs (arsenic, chromium, iron, lead,manganese, nickel, vanadium, and water) were reviewed. Vapor pressure, as a function oftemperature, for the referenced metals and water, are presented in Figure 2-6 and representthe unique pressure and temperature points where the referenced materials could transferto the vapor phase. For each of the referenced materials, pressure and temperaturecombinations above the lines represent the vapor state, and combinations below correspondto liquid or solid phases, depending on the species.

Superimposed on Figure 2-6 are the anticipated operating conditions in the TTZ and on theimmediate boundary of a heater assembly. Because of thermal conduction of energy fromthe heater assembly into the surrounding residuum formation, steep thermal gradients fromthe heaters will be observed during system operation. However, although the heaters cangenerate high temperatures, the radial influence of these conditions will be extremelylimited in the adjacent residuum. Additionally, maximum thermal output could only bereached in the unsaturated intervals of the residuum. At an assumed maximum heateroutput temperature of 700°C under the potential vacuum conditions (likely to rangebetween 0 and 12 inches of mercury during system operation), only the boiling point ofelemental arser<c could be exceeded:

• Uf jenario, although the heaters would be capable of potentially reaching the0 : t of elemental arsenic, it is unlikely that the compound exists in this state in

«; TTZ. Under near-neutral pH conditions typical of soil and groundwater systems(sue"- ^s r ihe TTZ), arsenic typically exists as the arsenate anion, which exhibits anep ge. Given this chemical property, volatilization of arsenate from

would not be possible, regardless of temperature.

• The arsenate anion also tends to be well adsorbed by ferric, manganese, and aluminumoxyhydroxide minerals that frequently exist in oxygenated environments such as theresiduum. Therefore, as soil moisture local to the heaters is removed, mineralinteractions will become the principal component controlling arsenic adsorption anddesorption from the subsurface soils.

COPCs for groundwater in the TTZ also include chromium, lead, iron, manganese, nickel,and vanadium. The high temperature behavior of these metals is summarized below.

• Historical operations conducted in the adjacent Building 4705 may have involved theuse of chrome-based salts of potassium, ammonia, or sodium:

- . Under standard temperature and pressure, chromate (CrOr2) and dichromate(Cr2Cv2)-based salts of potassium, ammonia, and sodium are solids. However,solutions of chrome salts were the most likely form used in the Building 4705operations. Chrome salts are appreciably soluble in water and, once dissolved,undergo complete dissociation, yielding chromate or dichromate anions. Becausedissociation results in the formation of a negatively charged chrome species, likearsenic (previously discussed), chromate and dichromate anions are not susceptibleto volatilization processes at any temperature.

2-28 • MGM07-NASA/IROD/001.DOC

r r r

10000

1000

u2,¥0>n.

100

SA-13 PilotISTD Heater Operating Range

—•—Arsenic-*- Chromium-©-Vanadium

10 15

Applied Vacuum (in Hg)

20 25 30

FIGURE 2-6Vapor Pressure as a Function ofTemperature for Select MetalsNASAMSFCSA-13IROD

2. DECISION SUMMARY

- During heating operations, moisture will be driven from the subsurface in the TTZ.As subsurface soils containing chromate or dichromate dry, crystallization of chromesalts of potassium, ammonia, or sodium would be anticipated. Solid forms ofchrome salts could present a potential health hazard; however, because dryingwould occur in the subsurface, there would be no viable path for the exposure of siteworkers to these materials.

- Under ambient conditions, crystalline chrome salts are stable solid materials. Withincreasing temperature, solids salts will undergo thermal decomposition. Forexample, potassium dichromate decomposes at about 500°C. Although thistemperature is well in excess of target heating goals (100°C), it is possible that thesetemperatures may be reached immediately adjacent to the heater wells. However,thermal decomposition of chrome salts would result in the production of chrome(III) oxides, which are significantly less mobile and less toxic than compounds wherechrome exists in +VI oxidation state.

• Vapor phase migration of lead is most often associated with particulate fumes that maybe created when lead (or any other metal) is directly exposed to high and intense heatsources (such as welding):

- As indicated in Figure 2-6, the temperatures and pressure required to vaporize leadare significantly above the operating range of the hearing and treatment system.Therefore, volatilization of lead from the subsurface soils is not possible.

- Operating conditions of the ISTD system are not expected to provide treatment or toaid in mobilization of lead that may be present in the subsurface soils. Under the pHand oxidation reduction potential conditions in the TTZ, lead probably is present inthe +2 oxidation state. In the presence of carbon dioxide (CCh), lead(II) will readilyform highly insoluble, carbonate-based complexes. Products of precipitationgenerally are considered immobile in porous media; however, lead may bedetectable in residuum groundwater samples that have high turbidity.

• Like lead, the volatilization of iron and manganese is not possible from the proposedtreatment system operation. Both iron and manganese occur naturally in the residuum,and it is likely that both.will be detected in extracted groundwater as either mineralcomplexes or charged ions; the elevated temperatures associated with ISTD operationare expected to have little effect on the observed concentrations of these metals.Subsurface geochemical conditions will control iron and manganese speciation anddistribution in the extracted groundwater and post-treatment groundwater quality;however, assuming that oxidative conditions prevail, both metals should exist asimmobile mineral complexes. The detection of these metals in groundwater probablywill be attributed to sample turbidity.

No direct anthropogenic sources of nickel and vanadium have been identified from theBuilding 4705 operations. Nickel is often associated with plating operations, which have notbeen conducted in the building area. Both nickel and vanadium also are components ofstainless steel and some alloys. In any event, volatilization of nickel and vanadium that mayexist in the subsurface soils is not possible from the proposed treatment system operations

MGM06-NASA/1ROD/OOVDOC 2-31

2. DECISION SUMMARY

(Figure 2-6), and elevated temperatures associated with system operations would have noeffect on these constituents.

2.12.5 In-situ Passive Flux MetersBefore system implementation and as part of pre-IRA site characterization efforts, passiveflux meters (PFMs) will be installed in selected monitoring wells at the SA-13 project area.PFMs are innovative devices composed of one or more permeable absorbent media (usuallyGAC) and volatile (alcohol-based) tracers. When installed in si£w, groundwatercontaminants are adsorbed to the media at a rate proportional to the concentration.Concurrently, the volatile tracers are released to the groundwater at a rate proportional tothe flow through the porous media. Following a known period of exposure to siteground water, the devices are removed and analyzed. The results, which include the massof groundwater contaminants adsorbed and the mass of volatile solvents lost, are then usedto estimate the mass flux of groundwater at the monitoring point. When multiple PFMlocations are evaluated simultaneously, the velocity (rate and direction) of contaminantflows can be evaluated.

2.12.6 System InstallationFollowing the completion of the well installations, system equipment will be mobilized andinstalled by the thermal contractor. This task will include the extension and connection ofthe utilities necessary to start and operate the system.

2.12.7 Startup TestingUpon the completion of the system installation, the startup of the system will be conductedin a staged, incremental manner, while the system operation is monitored continuouslyuntil the entire treatment system is in operation. The various system components will beadjusted to optimize system efficiency and effectiveness.

2.12.8 System Operation and MonitoringEquipment used in the IRA will be operated and monitored in accordance with an operationand maintenance (O&M) plan. An engineer or field technician will be onsite daily tomonitor the operation of system equipment and to collect process data that will be used toverify technology performance. Vapor recovery, flow, temperature, and vapor VOCconcentrations will be monitored at the total fluid extraction wells.

Thermocouples will be used to monitor temperature changes in the subsurface resultingfrom in-situ heater operation. Contaminant mass removal by the remediation system will beestimated using analytical data collected from the extraction wells and treatment system.

The system is expected to operate approximately 95 days. Figure 2-7 shows the anticipatedoperation schedule for the system.

2-32 MGM07-NASA/1ROD/001.DOC

2. DECISION SUMMARY

1009080706050403020100

1 I

Extractionphase

ISTD heat-upphase

i•fl

I

Polishingand boiling

phase

Cool-downfi

£• phase"

Time

FIGURE 2-7

Expected Operation Schedule and Duration of Treatment SystemNASA MSFC SA-13IROD

2.12.9 Post-IRA Monitoring and Land UseThis source reduction action is an IRA. It is expected that some residual contamination willremain in the subsurface after the implementation of the IRA. These areas will continue tobe monitored, as described in the Remedial Design/Remedial Action (RD/RA) Plan andMSFC's ongoing semiannual groundwater and surface water monitoring plan. In addition,the area will be subject to NASA's CERCLA site access control program, which serves as avehicle for exposure control for activities occurring within MSFC's boundaries. The landuse in this area is not expected to change from industrial upon the completion of this IRA,because NASA's mission activities will continue to use the shops in Building 4705.

2.13 Statutory DeterminationsSection 121 of CERCLA establishes several statutory requirements and preferences,including compliance with ARARs. This IRA will achieve compliance with the ARARs forthe following: 1) the construction of groundwater wells; 2) discharge permits and treatmentrules for wastewater discharges; 3) the release of VOCs to the atmosphere; and 4) health andsafety requirements for workers. This action, however, will not achieve compliance with theARAR for groundwater MCLs, which is being waived because it is an interim action.Statutory requirements specify preferences for cost-effectiveness, use of permanentsolutions, and innovative treatment technologies or resource recovery technologies to themaximum extent practicable, and finally a preference for use of treatment that permanentlyreduces the toxicity, mobility, or volume of hazardous substances.

This interim action is protective in the short term by removing contaminant mass to controlthe potential spread of the detected contamination beneath SA-13. NASA believes that the

MGM06-NASA/IROD/001 DOC 2-33

2. DECISION SUMMARY

selected interim action represents the-best balance of tradeoffs in terms of short-termeffectiveness and implementability for its limited scope. The action does reduce thepotential for contaminant migration and is appropriate for an interim response.

The selected interim remedy is expected to significantly reduce the contamination present inthe TTZ, compared to the other (ISCO) option. Given this expected return, and the samegeneral order of magnitude of the capital costs to implement the options, the selectedremedy also is believed to be the most cost-effective option.

2.14 Explanation of Significant DifferencesThe FFS/PP for the IRA at SA-13 was advertised for public comment on April 1, 2007, witha public comment period from April 2 through May 4, 2007. The FFS/PP identified theISTD alternative as the preferred alternative. NASA received no public comments (eitherverbally or in writing) on the document and received no written requests for a publicinformation session. Accordingly, the document was finalized and placed into thedocument repositories per NASA's Community Relations Plan.

2-34 • MGM07-NASA/1ROD/001.DOC

3. Responsiveness Summary

As discussed in Section 2.14, NASA received no public comments (either verbally or inwriting) on the FFS/PP document that identified the ISTD alternative as the preferredalternative, and received no written requests for a public information session about theinterim action project. Accordingly, the FFS/PP document was finalized and placed into thedocument repositories per NASA's Community Relations Plan.

•The ISTD alternative presented in the FFS/PP for the IRA is now the selected interimremedy for SA-13 under this IROD. This decision is based on the administrative record forSA-13 in OU-3, including the FFS/PP document, public comments, and other documents inthe administrative record file for this site.


4. References

National Aeronautics and Space Administration. March 2007. Final (For Public Comment)Focused Feasibility Study/Proposed Plan for Volatile Organic Compound Contamination beneathSource Area 13 at the Marshall Space Flight Center, Huntsville, Alabama.

National Aeronautics and Space Administration. November 2005. Draft Addendum to theSitewide Remedial Investigation/Feasibility Study Work Plan to Address Additional Sampling atOU-3.

Redstone Arsenal and National Aeronautics and Space Administration. August 2004.Conceptual Site Model for Redstone Arsenal and NASA MSFC, Madison County, Alabama.


National Aeronautics andSpace Administration

George C. Marshall Space Flight CenterMarshall Space Flight Center, AL 35812

Reply to Ann of:AS10(50-07) ' July 13,2007

Mr. Stephen BallRemedial Project ManagerEnvironmental Protection Agency4WD-FFB61ForsythStS.W.Atlanta, GA 30303-8960

Ms. Sarah GillProject ManagerAlabama Department of Environmental ManagementGovernment Facilities SectorHazardous Waste Branch-Land Division1400 Coliseum BlvdMontgomery, AL 36110

Subject: Final Interim Record of Decision - Interim Action Project for Source Area No. 13 •Operable Unit No. 3 (July 2007), Marshall Space Flight Center, HuntsviUe,Alabama

Mr. Ball and Ms. Gill:

Enclosed is the Final Interim Record of Decision - Interim Action Project for Source Area No. 13 -Operable Unit No. 3 (July 2007), Marshall Space Flight Center, Huntsvilk, Alabama thatincorporates both agencies comments.

NASA has signed the Authorizing Signature declaration and is routing to EPA and ADEMfor your signatures. Please call me if you have any questions at 256-544-6935.

Sincerely,

Farley DavisEnvironmental Engineering and Occupational Health Office

Mission Success Starts with Safety

Responses to Agency Comments on

Draft - Final Interim Record of Decision - Interim Action Project forSource Area No. 13 - Operable Unit No. 3 (March 2007)

Marshall Space Flight Center, Huntsville, Alabama

EPA Comments (April 2,2007)1. EPA Specific Comment #1 was not addressed in the Draft Final IROD. Please

incorporate the agreed1 upon response in section 1.1 of the Draft Final document

RESPONSE: Tiie national Superfitnd electronic data base ID. Number (CERCUS) wasindiided onthe fly-sheet and in Hie first paragraph under Section 2.1 of the document. However, the I.D. was notincluded and will be added to the front cover oftlie Final version ofthelROD document.

2. In regards to EPA Legal Comments (December 5,20.06), Comment #1 asks that "and iscost effective" be added to Section 1.5 Statutory Determinations. In the Draft Finalversion the text reads "and is potentially cost effective." Adding "potentially" into thatstatement could cause the public to question that we are using taxpayer dollarseffectively. The Focused FS should make the determination that this interim remedy iscost-effective, so we should state that without question unless NASA feels that it is notcost effective.

RESPONSE: NASA.believestlwtthecosteJftctiwnessofthe thermal technology as a site-wideremedy, based ort its SA-13 IRA application, has not yet been determined. However, within tiiecontext oftlie IRA, NASA agrees that the alternative was determined to be cost-effective and tiieword "potential" will be deletedin the final version of tiie IROD.

3. Please include the signature page in the Declaration. EPA's signature block should looklike the following:

Franklin E. HillActing DirectorSuperfund Division

RESPONSE:: The signature blocksfir NASA, EPA and ADEM will be, added to the final version ofthelROU.

ADEM Comments (May 24,2007)1, Page 2-9, Sectiqn 2.5 SumihJiry of Site Characteristics, second paragraph: 'HiO* is

written in two pl&ces without, the'2's as subscripts. Please correct

RESPONSE: TJiese corrections wilibe made,

2. Page 2-18, Section 2.9, Summary of Site Risks: The wording of the second paragraph onpage 2-18 (comparing soil cbhcenfrations to SSLs) suggests that all of the compounds inthe comparison significantly exceeded the DAT4 SSLs. However, according to Table 2-4,TCE was the only compound to significantly exceed the SSL/the other compounds were

MGMO&NASA/1ROD/RTC.DRAFT_RNAL.SA13 IROO,062107 (2J.DOC

RESPONSE TO COMMENTS - DRAFT FINAL WOO - SA-13TNTERIM ACTION PROJECT

either less than the SSL or just slightly over the SSL, Please revise this paragraph toreflect what is shown in Table 2-4.

RESPONSE: Tiie wording of this paragraph will be.clarified via tiie following underlines for entriesand strike-throughs for deletions:

As presentediii Table 2-4, the concentrations of some constituents in sou's, primarily TCE,significantly exceed the teachability criteria, indicating that site soils have the potential to affectgroundwater;this potential is confirmed by tiie presence of the same compounds in groundwater atconcentrations that currently exceed the drinking water standards and guidance levels.

3. Pages 2-21 arid 2-22> Section 2.12,2 Target Treatment Zone: At the bottom of page 2-21the document states that 'The vertical thickness of the TTZ averages about 27 ft. *.'•,however/ at the top of page 2-22 an average TTZ thickness of 20 ft is used toapproximate the TTZ volume. Please clarify why two different average TTZ thicknessesare given.

RESPONSE: Tiie paragraph segntent at the top of Page 2-22 will be corrected via tiie followingunderlines foi• entriesand strike-throughs for deletions. The correction was identified duringdevelopment of tiie Draft-Final SA-13 RD/RA Work Plan document:

"variations in bedrock elevation, saturatedi residuum thickness, and surface toppgrapjry. The volumecontained in the TTZ is approximately i?9QQ 480 cubic yards, assuming an average TTZ. thickness of2Q 27ft. A conceptual cross section of UKselected TTZ is shmuri in Figure 2-4."

4. Page 2-31, Section 2.12.4 Treatment System: In the fifth and sixth paragraphs on page 2^31, 'in-situ thermal desorptipn' is abbreviated 33 'BIT instead of 'ISTD'. Please correct.

RESPONSE: Tliis correctiomuill be made.

5. Page 2-32, Section-2;12.4 Treatment System: The closing •)' is missing after the referenceto 'Figure 2-&. Please correct

RESPONSE: This correction will be niade.

6. Page 3-33,.Sectipn 2.13 Statutory Determinations: Overall, MSFC has adequatelyrevised the document to address prior ADEM and EPA comments regarding ARARs.However, at the bottom of page 2-33 the sentence "There are no specific ARARs to thisiriterirh action' needs to be deleted since it |s no longer consistent with the ARARdiscussions in the rest of the document.

RESPONSE: This sentence on Pages 2-33 and 2-34 will be deleted

7. Page 3-1, Section 3.0 Responsiveness Summary: The note at the top states that thesection-may be significantly revised after^eFFS/PP public comment period.,Please becertain this is done and that the information in the first paragraph regarding the numberof people who'submitted comments (presumably included as an example, since thepublic comment period was not complete when this document was written) is correctlyupdated in the Final document.

RESPONSE: There were no public comments on tiie FFS/PP public-release version. Section 2.14will be revised^as follows:

MGMO&NASWlROtVRTC.DRAR_FINAL.SA131ROD.062107 (2),DOC

RESPONSE TO COMMENTS - DRAFT FINAL IROO- SA-13 INTERIM ACTION PROJECT

"TheFFS/PPfor the IRA at $A-13>was advertised for public comment on April 1,2007, with apublic comment period from April!"*through May 4,2007. The:FFS/PP identified tite 1STDalternative as tlie preferred alternative. NASA received no public comments (neither verbally nor inivriting) on the document and received no written requests for a public inforination session.Accordingly, tfte document was finalized and placed into the document repositories per ourcommunity relations plan".

MGM06.NASA/iROO/RTC.ORAFT_FINAL.SA13 IROD.062107 (2).DOC

National Aeronautics and Space Administration

George C. Marshall Space Flight CenterMarshall Space Right Center, AL 35812

March9,2007

Mr. Stephen BaDRemedial Project ManagerEnvironmental Protection Agency4WD-FFB6lForsythStS.W.Atlanta, GA 30303-8960

Ms. Sara GillProject ManagerAlabama Department of Environmental ManagementGovernment Facilities SectorHazardous Waste Branch-Land Division1400 Coliseum BlvdMontgomery, AL 36110

Subject: Draft-Final Interim Record of Decision - Interim Action Project for Source AreaNo. 13 - Operable Unit No. 3 (March 2007), Marshall Space Flight Center,Huntsville, Alabama

Mr. Ball and Ms. Gul-

Enclosed is the Draft-Final Interim Record of Decision - Interim Action Project for Source AreaNo. 13 - Operable. Unit No. 3 (March 2007), Marshall Space Flight Center, Huntsvttle, Alabama.

NASA believes that the document substantially reflects agreed-upon comments on the DraftIROD and looks forward to issuance of the final version as soon as practicable. In theinterim, please feel free to call me at 256-544-6935 if there any questions or concerns.

Sincerely,

Farley DavisEnvironmental Engineering and Occupational Health Office

01 6SS8 t*S 9SS 0TSb DdSW yd 6T :0T

CH2MHILL T R A N S M I T T A L

To: Dr. Julie Corkran From: CH2M HILLSenior Remedial Project Manager Vicky Potter/MGMEnvironmental Protection Agency4WD-FFB61 Forsyth St. S.W.Atlanta, GA 30303-8960

Ms. Nelly SmithProject ManagerADEMGovernment Facilities SectorHazardous Waste Branch-Land Division1400 Coliseum Blvd.Montgomery, AL 36110

Attn: Dr. Corkran and Ms. Smith Date: June 8, 2006

Re: Draft Interim Record of Decision: Interim Action Project for Source Area 13, OperableUnit 3, NASA MSFC

We Are Sending You: Method of shipment:

X Attached Under separate cover via

Shop Drawings Documents Tracings

Prints Specifications Catalogs

Copy of letter Other:

Quantity Description

1 each Hard Copy and CD (EPA)

1 Hard Copy (ADEM)

2 CDs (ADEM)

If the material received is not as listed, please notify us at once.

Remarks:

The referenced CDs are being sent as a follow-up to the hard copy reports sent earlier.

Copy To:

Jim Ashworth/TechLaw, Inc. (1 Hard Copy and 1 CD)

SA-13 DRAFT IROOJRANSMITTALDOC 1 338516A1.01

Responses to Agency Comments on

Draft - Interim Record of Decision - Interim Action Project forSource Area 13 - Operable Unit 3 (May 2006)

Marshall Space Flight Center, Huntsville, Alabama

EPA Comments (November 30,2006)

General Comments

The Draft IROD appears to be in good shape. There are a few of minor sections that aremissing and a few editorial comments. For more information on what to include in themissing sections, please refer to EPA guidance titled, "A Guide to Preparing SuperfundProposed Plans, Records of Decision and Other Remedy Selection DecisionDocuments."

Please ensure the correct public comment dates are present in the IROD for SA 13.

RESPONSE: Comments acknowledged.

Specific CommentsSection 1.1

• Please include the National Superfund Database identification number.

RESPONSE: The EPA waste generation ID. Number AL1800013863 and the national Superfundelectronic data base I.D. Number (CERCUS) AL7210020742 for MSFC will be included as part ofthis section.

Section 1.4

• On page 1-6 in the third sentence there is only a reference to the subsurface. Pleaseadd language that references groundwater also.

RESPONSE: In this context, the term "subsurface" was meant to be generic and inclusive of allmedia. To clarify, and for consistency, this term will be replaced with the phrase "soil andgroundwater".

Section 2.1

• Please include generic language on the name and location of MSFC, the lead andsupport agencies involved, a statement on who is paying for the clean-up, and theNational Superfund electronic database identification number.

RESPONSE: The following text will be added as the first paragraph under this section in the Draft-Final version of the document:

MGM07-NASA/1ROD/SA-13 RTC J)RAFT_SA13 IROD.DX

RESPONSES TO AGENCY COMMENTS ONDRAFT - INTERIM RECORD OF DECISION - INTERIM ACTION PROJECT FOR SOURCE AREA 13 - OPERABLE UNIT 3 (MAY 2006)

"NASA MSFC is located in north-central Alabama and occupies 1,841 acres within the centralportion of the U.S. Department of the Army (DA) Redstone Arsenal (RSA). NASA'senvironmental management program at MSFC is under the federal CERCLA program. TheEPA waste generation l.D. Number is AL1800013863 and the national Superfund electronicdata base l.D. Number (CERCLIS) is AL7210020742for the facility. As indicated in Section1.2, NASA is the lead agency for funding and implementing environmental restoration atMSFC, with ADEM and EPA in supportive roles under the FFA."

• In the second sentence, please confirm that the reference to the OU 3 RI Reportshould be the OU 3 RI Work Plan.

RESPONSE: The reference should be to the OU-3 RI Work Plan and this correction will be made inthe Draft-Final version of the document.

Section 2.2

• Please add a brief discussion of the activities that have lead to the current problemand a brief statement discussing previous actions taken at this site.

RESPONSE: The following text will replace the 2nd paragraph on Page 2-4 in the Draft-Final versionof the document:

"The groundwater plumes exist throughout a large portion of the NASA facility. Due to thecomplex subsurface environment (see Section 2.5), the groundwater contamination likely affectsadjacent areas of RSA. NASA remedial investigations of the groundwater contamination havebeen ongoing since the late 1990's and additional RI activities are currently underway toevaluate the nature and distribution of the contamination within the source areas and thegroundwater system. Once the RI report is approved by EPA and ADEM,a feasibility study ofremedial alternatives will be conducted as part affinal remedy selection for OU-3. Additionally,an interim record of decision (IROD) will be in place for OU-3 by the end of September 2007that outlines measures to be implemented as a means of ensuring protection of human health atthe facility until final remedies for OU-3 are identified, selected, and implemented. NASA isevaluating other interim actions that may also be implemented at the facility." More specifically,at SA-13, releases from a former drum storage area resulted in a TCE-based contaminant sourcearea where use ofin-situ chemical oxidation technology was not successful in reducingcontaminant levels. Additional information about the SA-13 area and conditions is presented inSection 2.5, below."

Section 2.4

• Please state that this IRA will be consistent with the final remedy at OU 3.

RESPONSE: The following sentence will be added at the end of section on page 2-5 in the Draft-Final version of the document: "The IRA will be consistent with the final remedy selected for OU-3implementation."

Section 2.8

• Please add a summary of the Rationale for the Selected IRA.

• Please add a discussion on estimated ERA Cost.

MGM07-NASA/IROD/SA-13 RTC_DRAFT_SA13 IROD.DOC


RESPONSE: The text immediately following the Section 2.8 header line will be modified with theunderlined provisions in the Draft-Final version of the document:

"The selected interim remedy for SA-13 is ISTD. This option is believed to best accomplish theIRAOs and IRAGsfor the IRA, to be the more technically effective and reliable option, and tobest meet CERCLA requirements for implementing IRAs. While involving higher capital costexpenditures, the estimated costs for both options are essentially the same order of magnitude;however, given the expected contaminant reduction resulting from the selected option, it shouldresult in a significantly lower unit cost (on a dollars per pound of contaminant removed basis)than the other option. A detailed description of the interim remedy is provided in the followingsubsections."

Section 2.9

• Please add a discussion on cost effectiveness.

RESPONSE: A new paragraph will be added to the section on Page 2-25 in the Draft-Final version ofthe document, to read:

"The selected interim remedy is expected to significantly reduce the contamination presentwithin the TTZ, as compared to the other (ISCO) option. Given this, and the same general orderof magnitude of the capital costs to implement the options, the selected remedy is also believed tobe the most cost-effective option."

Missing sections

• Please add a section after section 2.5 titled Current and Potential Future Land andResource Uses.

RESPONSE: A new Section 2.6 Current and Potential Future Land and Resource Uses will be addedto Page 2-11, with subsequent sections re-numbered accordingly, in the Draft-Final version of thedocument:

"Section 2.6 Current and Potential Future Land and Resource Uses

Current land use at SA-13 (as well as throughout MSFC) is classified as industrial and willremain this classification throughout the duration of NASA's occupation of the property.NASA maintains a Master Plan for the facility that manages land use consistent with NASA'smissions and programs. NASA maintains a Land Use Control Assurance Plan to ensure thatland use controls imposed as part of remedy selections at M.SFC stay in effect so that the remedyremains fully protective of human health (and the environment, as applicable). NASA also hasan active a site access control program to protect workers and visitors at CERCLA sites andprovide centralized control of access, work activities, associated land use activities, and relatedconstruction activities (including proposed groundwater withdrawals for dewatering or otherpurposes). By the end of September 2007, NASA will also have an IROD in place for OU-3 topreclude groundwater withdrawals for potable (drinking water).purposes and providemanagement control over all other non-potable groundwater uses and discharges throughoutMSFC."

• Please add a section after section 2.6 titled Interim Remedial Action Objectives.

RESPONSE: Section 1.4 of the draft document describes the selected remedy and includes the IRAGsfor the IRA. The discussions mention the associated IRAOs; the specific IRAOs for the target media


RESPONSES TO AGENCY COMMENTS ONDRAFT - INTERIM RECORD OF DECISION - INTERIM ACTION PROJECT FOR SOURCE AREA 13 - OPERABLf UNIT 3 (MAY 2006)

are identified in the notes of each IRAG table. The tables are identical to those in the SA-13 FFS/PPdocument. NASA proposes no changes in this regard but would be willing to re-organize the reportand incorporate a specific IRAQ and IRAG section into the Draft-Final version of the document ifEPA feels it is prerequisite to approval.

REVISED RESPONSE: The new section will be added, as agreed in the January 11, 2007teleconference. The IRAOs will be re-iterated from Section 1.4 of the draft document. Section 1.4 willremain per the draft, but a statement will be added to direct the reader to the new section for moreinformation on the IRAOs. The new section will also include information regarding the basis andrationale for the IRAOs and how the IRAOs address the risks identified in the risk assessment.

• Please add a section after section 2.7 titled Principle Threat Wastes.

RESPONSE: A new Section 2.7 Principle Threat Wastes will be added, with subsequent sections re-numbered accordingly, in the Draft-Final version of the document:

"Section 2.7 Principle Threat Wastes

Principal threat source material (PTSM) is represented by source material contaminants (suchas DNAPL-like conditions) that present an obvious potential threat to human health and theenvironment, either because of the nature and extent of contamination or because a large mass ofleqchable material in the ground. TCE constitutes the primary PTSM within the TTZ at SA-13because of the elevated and dominant concentrations of this COPC, the forms that in which itlikely exists, and its fate and transport properties that allow primarily dissolved phase migrationinto and within the groundwater system.

The proposed IRA will result in the reduction in the mobility, toxicity, and volume of thePTSM. However, it is likely that some residual contamination will remain in the TTZ afterimplementation of the IRA, and other contaminated areas exist adjacent to the TTZ. These areaswill continue to be monitored and evaluated as part of the CERCLA RI/FS process that will leadto decisions on final remedies for OU-3."

EPA Comments (December 5,2006)1. Section 1.5 Statutory Determinations: The following needs to be added to the end of the

first sentence: "and is cost effective." As to ARARs, this IRA does have associatedARARs as shown in Table A-l of the FFS. The second sentence should be deleted andreplaced with the following:

"This action complies with Federal and State applicable or relevant andappropriate requirements (ARARs) with the exception of compliance withgroundwater MCL levels which is being waived. Although this interim actionis not intended to address fully the statutory mandate for permanence andtreatment to the maximum extent practicable, this interim action does utilizetreatment and thus supports that statutory mandate."

In the present third sentence, after the words "principle element" the following shouldbe inserted "although partially addressed in this remedy."

RESPONSE: These changes will be incorporated into the Draft-Final version of the document.



REVISED RESPONSE: These changes mil be incorporated into the Draft-Final version of thedocument. Per the January 11, 2007 teleconference, this section of the Draft-Final document will alsoconsider EPA comments on the OU-3 PP regarding ARARsfor consistency.

2. Table 2-4: In the "Compliance with ARARs" row and "Alternative 3" column of Table 2-4, there is a statement about MCLs not being achieved but no statement about otherARARs. To clarify the ARARs compliance issue, the following sentence should beadded to the end of the present statement. "This Alternative will result in compliancewith all other ARARs."

RESPONSE: These changes will be incorporated into the Draft-Final version of the document.

3. Section 2.9 Statutory Determinations: In the first paragraph, replace the first sentencewith the following:

"Section 121 of CERCLA establishes several statutory requirements andpreferences, including compliance with ARARs. This IRA will achievecompliance with the ARARs for (1) the construction of groundwater wells, (2)discharge permits and treatment rules for wastewater discharges, (3) therelease of VOCs to the atmosphere, and (4) health and safety requirements forworkers. This action, however, will not achieve compliance with the ARAR forgroundwater MCLs which is being waived on.the basis that this is an interimaction."

RESPONSE: This addition will be incorporated into the Draft-Final version of the document.

ADEM Comments (October 13,2006)1. Section 1.4 Description of the Selected Remedy, page 1-4, Table 1-3: The table is

divided into two sections. Does the second section represent an alternative interimremedial action goal (IRAG) option, or is it simply listing the MCLs and PRGs for thechemicals of potential concern? It is difficult to understand the table the way it ispresented and there is no explanation provided in the text. In the document pleaseclarify why there are two sections to Table 1-3.

RESPONSE: The table reflects two IRAG options corresponding to the two IRAOsfor the bedrockgroundwater. It is possible (but not currently known) that some of the contamination will occurwithin the upper portions of the bedrock included within the target treatment zone: So, the %reduction IRAG option was also included for the bedrock groundwater, as well as an option ofmeeting MCLs orPRGs (as applicable) for the COPCs.

2. Section 1.5 Statutory Determinations, page 1-7,1st paragraph: Why are all of theapplicable or relevant and appropriate requirements (ARARs) listed on page A-2 of theMay 2006 Draft-Final Focused Feasibility Study/Proposed Plan (FFS/PP) being waived,instead of just the chemical specific ARARs? The chemical specific ARARs listed werewaived since the IRA is not expected to achieve maximum contaminant levels (MCLs)and preliminary remediation goals (PRGs), but the action specific ARARs identified inthe FFS/PP could still be met. Please clarify.

RESPONSE: Please refer to the responses to EPA comments, below, for related changes that will be

MGM07-NASA/IROD/SA-13 RTC_DRAFT.SA13 IROD.DOC

RESPONSES TO AGENCY COMMENTS ONDRAFT - INTERIM RECORD OF DECISION - INTERIM ACTION PROJECT FOR SOURCE AREA 13 - OPERABLE UNfT 3 (MAY 2006)

incorporated into the Draft-Final version of the document.

3. Section 2.8.4 Treatment System, page 2-22, 7th paragraph: Should the portion of thesentence that states "...significantly below the operating range..." actually read"...significantly above the operating range..."? Please check.

RESPONSE: The correction mill be made in the Draft-Final version of the document.

4. Section 2.8.4 Treatment System: Based on the information provided there is a very lowprobability of metal volatilization, however, it is possible the boiling point of arseniccould be exceeded in the immediate vicinity of the heaters. If, during the treatmentprocess, the heater output temperature exceeds the boiling point of arsenic the treatedvapor and condensate should be analyzed for arsenic. Please incorporate this into theSA-13IROD.

RESPONSE: The heater output temperature in the immediate vicinity of the heater element willlikely be higher than the boiling point of arsenic. However, the residuum matrix will be under avacuum created by the SVE system and the vapor temperature entering the SVE system (which willbe monitored) is expected to be up to 100° C or less, significantly below this level. There is no objectiveto operate the system at higher temperatures. As a result, we don't believe arsenic monitoring isrequired. .

MSFC Response to ADEM Comment 4 on the Draft IROD, via Janary 18, 2007 Email(and identical comment on FFS/PP): I need a bit more clarification on your response.The way I am reading it is: There is a possibility that arsenic could be vaporized in theimmediate vicinity of the heater elements due to the high temperature, however, theSVE system will be drawing off all vapor. The vapor will be at less that 100 degreeswhen it enters the SVE, so tine implication is that any arsenic that had vaporized will bere-deposited in the subsurface before it has a chance to enter the SVE? Is this correct?

REVISED RESPONSE: While it is feasible that temperatures immediately adjacent to the heaterborings will approach or exceed the boiling point of arsenic, the conduction of thermal energy throughthe casing in the heater borings and to the bulk formation will result in strong temperature gradientsin the subsurface soils during system operation. This condition may result in temperatures wherearsenic vapor could be produced (e.g. at the heater); however, since the subsurface zones immediatelysurrounding the heater wells are expected to be significantly below the boiling point of arsenic, themigration of the compound in vapor phase from the subsurface is considered highly unlikely.

5. Section 2.8.8 System Operation and Monitoring, page 2-24, Table 2-7: The x-axislabels are partially cut off. Please correct.

RESPONSE: This correction will be made in the Draft-Final version of the document.

MGM07-NASA/1ROD/SA-13 RTC_DRAFT_SA13 IROD.DOC

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