UNITED STATES ENVIRONMENTAL PROTECTION AGENCY REGION 6

1445 ROSS AVENUE, SUITE 1200 DALLAS, TX 75202-2733

JAN 26 2005

Ms. Cathy R. Scheirman Director, Environmental Management OC-ALC/EM 7701 Arnold Street, Suite 204 Tinker AFB, OK 73145-9100

Re: Tinker Air Force Base (EPA ID# OK1571724391) Five-Year Review Report

Dear Ms. Scheirman:

The enclosed Five-Year Review Memorandum documents the U.S. Environmental ProtectionAgency’s (EPA’s) concurrence with the protectiveness determinations in the Five-Year Review Reports forthe Tinker Air Force Base National Priority List (NPL) Site (site) (Tinker Air Force Base, March 2003). Asummary of findings and actions needed regarding the Five-Year Review Reports are included in theFive-Year Review Memorandum. This is the second five-year review for the site which was triggered due tothe implementation of the remedial action at the site.

The U.S. Air Force, as lead agency for Tinker Air Force Base, conducted this review The Air Forceprovided EPA with two Five-Year Review Reports for Tinker Air Force Base, one signed April 2003 forBuilding 3001 Operable Unit 1 and one signed February 2003 for Soldier Creek Sediment and SurfaceWater Operable Unit 2. This is EPA’s review of the final Five-Year Review Reports.

Should you have any questions pertaining to this letter. please contact me or Robert Sullivan of mystaff at sullivan.robert@epa.gov or (214) 665-2223.

Sincerely yours,

John R. Hepola Chief Superfund AR/TX Branch

Enclosure

cc: Robert Replogle, ODEQ Joseph Cecrle, OC-ALC/EM

Internet Address (URL) • http://www.epa.gov Recycled/Recyclable • Printed with Vegetable Oil Based Inks on Recycled Paper (Minimum 25% Postconsumer)

Five-Year Review Memorandum

Tinker Air Force Base Superfund Site EPA ID# OK1571724391

Oklahoma City, Oklahoma County, Oklahoma

This U.S. Environmental Protection Agency (EPA) memorandum documents the performance,determinations and approval of the Tinker Air Force Base Superfund Site Five-Year Review, including thetwo attached Five-Year Review Reports prepared by the U.S. Air Force.

Summary of Five-Year Review Findings

The U.S. Air Force, as lead agency for Tinker Air Force Base, Oklahoma City, Oklahoma County,Oklahoma (the site), conducted the Five-Year Review for both the Building 3001 Operable Unit 1 (TAFB,March 2003) and the Soldier Creek Sediment and Surface Water Operable Unit 2 (TAFB, March 2003).This is the second Five-Year Review for the site, which was triggered due to the implementation of theremedial action at the site on September 30, 1992. The first Five-Year Review Report (Parsons EngineeringScience Inc., September 1998) was approved by an EPA memorandum dated September 25, 2002. Thisreview is required by Section 121(c) of the Comprehensive Environmental Response, Compensation, andLiability Act (CERCLA), 42 U.S.C. §9621(c), which requires that a periodic review be conducted no lessoften than every five years after the initiation of remedial action at sites where hazardous substances,pollutants or contaminants will remain onsite above levels that allow for unrestricted use and unrestrictedexposure. The remedy components determined by the OU 1 Record of Decision (ROD) of August 15, 1990,and OU 2 ROD of September 14, 1993, are expected to remain protective of human health and theenvironment.

The Tinker Air Force Base Superfund Site is generally defined by the Building 3001Trichloroethene (TCE) and Chromium ground water plumes (OU 1), and the sediment and surface water ofthe main stem of Soldier Creek and the tributaries of Soldier Creek originating on Tinker AFB (OU 2). Theremedial objectives for the site are established in the ROD.

One specific goal identified in the ROD for OU1 is to prevent future human exposure by ingestion,inhalation or dermal exposure to TCE concentrations exceeding 5.0 pg/L in the ground water of thesaturated zone. No change in this goal has been effected since the first Five-Year Review. The remedycomponents for the site include a site-wide long term monitoring (LTM) plan; an enhanced ground waterextraction system installed in three aquifer zones; and a ground water Industrial Wastewater TreatmentPlant (IWTP) constructed specifically for the remedial action. Although the goa1 of 5.0 µg/L TCE in theground water of the saturated zone has not presently been achieved, the remedy components appear to haveprevented any further current migration of the Building 3001 TCE plume and the plume remains within thepresent boundary of the Federal facility. The remedy components are currently functioning as designed, andno deficiencies were identified in the Five-Year Review which impact the protectiveness of the remedies.Contaminant concentration data and water level data indicate that the extraction wells are capturing thecontaminants associated with Building 3001 (TAFB Building 3001 Five-Year Review Report – Section 9,Conclusions).

A Work Plan submitted by Tinker AFB supporting the temporary shutdown of the Building 3001(OU1) ground water pump and treat system was concurred to by EPA in a letter dated June 27, 2003. Theconditions for sampling, risk evaluation and parameters for re-start of the operating system are outlined inan Oklahoma Department of Environmental Quality (ODEQ) letter dated May 2, 2003. Tinker AFB ispresently collecting perforrnance monitoring data for use in an optimization evaluation of the OU1 remedialaction, as well as to monitor the plume stability.

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A memorandum submitted by Tinker AFB to confirm the decision to discontinue samplirig OfSoldier Creek-sediment and surface water (OU2) was received by EPA on August 20, 2004. The TinkerAFB memorandum documents by reference the annual sampling conducted in accordance with the RODrequirements. Results document there has been no exceedence of health-based screening levels in samplestaken during the five-year monitoring program. In addition, recent facility improvements, including theconstruction of a concrete culvert within the facility length of Soldier Creek, minimize the potential forsediments to move off-base and pose a human health or ecological threat to downstream receptors. The EPAconcurs with the Tinker AFB Five-Year Review recommendation that additional sampling is not necessaryto complete the OU2 Remedial Action Report. The ODEQ previously concurred by letter dated September14, 2004.

Tinker Air Force Base is currently operated by the U.S. Air Force, and access to the Base isrestricted and controlled. Future land use is not expected to change; however, if land use does change,in’stitutional controls (ICs) may be required to limit the use of the ground water in the saturated zone andprevent human exposure. Presently, the protectiveness of the remedial action is being verified by the LTM,which monitors sediment, surface water and ground water concentrations of chemicals of potential concern.

Actions Needed

The recommended actions below address issues concerning exposure assumptions; toxicity data;data collection; and performance monitoring for the selected remedy components. While these issues are notcurrently significant enough to call into question the protectiveness of the remedy, the performancemonitoring data will be needed to assess the future remedy protectiveness.

(1) The exposure assumptions used in the risk assessment have not changed. EPA conducted aDraft TCE Toxicity Risk Re-Assessment in September 2001. The Draft Re-Assessmentprovided for a range of potential TCE toxicity and established new “provisional values”.These provisional values are more stringent and EPA recommends the Air Force evaluaterisk using both values, as warranted.

(2) TCE contamination of the saturated zone ground water on the Tinker AFB property remainsabove the remedial goal of 5.0 µg/L. This contamination is predominantly from the Building3001 TCE plume. An institutional control (IC) program is a component of many of thealternatives being evaluated for the property. A ROD Amendment is required to implementand monitor an IC program if remedial goals are not based on unrestricted use andunrestricted exposure. EPA recommends use of the Institutional Control (IC) User Guidance(EPA540-F-00-005, September 2000), including the use of the IC Checklist and IC TrackingSystem (ICTS), as warranted. Other protective measures may be needed such as a base-widecomprehensive plan that formally restricts the use of ground water.

(3) EPA recently published the Draft Guidance For Evaluating The Vapor Intrusion To IndoorAir Pathway From Ground Water and Soils (Subsurface Vapor Intrusion Guidance)(EPA530-F-02-052, November 2002). EPA recommends that the Air Force conduct ascreening evaluation as to whether or not the vapor intrusion exposure pathway is completeand, if so, whether it poses an unacceptable risk to human health. EPA recommends that thisscreening evaluation is necessary for both occupied buildings and structures above theBuilding 3001 TCE plume, and for any remedial systems that off-gas TCE.

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(4) Performance monitoring and evaluation is necessary to continuously optimize the remedialaction at the site.

Determinations

I have determined that the remedy for the Tinker Air Force Base Superfund Site, Oklahoma City,Oklahoma County, Oklahoma, is protective of human health and the environment, and will remain soprovided the action items identified in the Five-Year Review Report are addressed as described above andin the report.

Approved By: Date:

Samuel Coleman, P.E. Director, Superfund Division U.S. Environmental Protection Agency Region 6

Five-Year Review Report for The Building 3001 NPL Site

Submitted to:

United States Environmental Protection AgencyRegion VI

Prepared by: Sara Sayler

OC-ALC/EMPE 7701 Arnold Street, Ste. 204 Tinker AFB, OK 73145-9100

Phone: 405/734-45SO Email: Sara.Sayler(@Tinker.af.mil

April 2003

SIGNATURE PAGE

TABLE OF CONTENTS

Page

EXECUTIVE SUMMARY 6SECTION 1 INTRODUCTION 7SECTION 2 BACKGROUND 7

Physical Characteristics 7Land and Resource Use 8

Surrounding Community 8Human Use of Resources 9

Contaminants 9Initial Response 10

SECTION 3 REMEDIAL ACTIONSRemedy Selection 11Remedy Implementation 11Operation and Maintenance Requirements 13

Extraction Well Field and Groundwater Transport System 13Groundwater Treatment Plant (GWTP) 14Product Recovery System at NTA 16

Operation and Maintenance Activities 16Groundwater Treatment Plant (GWTP) 16NTA Product Recovery System 17

SECTION 4 REMEDIAL ACTION OBJECTIVES 17Building 3001 17North Tank Area 17Pit Q-51 17

SECTION 5 PROGRESS SINCE LAST FIVE-YEAR REVIEW 17Protectiveness Statement from ROD 17Protectiveness Statement (Previous Review) 18Status of Recommendations and Follow-up Actions from Last Review 18Results of Implemented Actions and Intended Affect 18

SECTION 6 FIVE-YEAR REVIEW PROCESS 18Community Involvement 18Interviews 19Site Visits 19Data Review 20

Building 3001 Groundwater 20North Tank Area 22Pit Q-51 24

SECTION 7 TECHNICAL ASSESSMENT 24SECTION 8 ISSUES FROM PREVIOUS REVIEW 25SECTION 9 CONCLUSIONS 26SECTION 10 RECOMMENDATIONS 27SECTION 11 NEXT REVIEW 27

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LIST OF FIGURES

No. Title

1 Tinker Air Force Base Location Map 1 NPL Site Location Map 3 Building 3001 Operable Unit Site Map 4 Extraction Well Location Map 5 Generalized Site Geology 6 TCE concentration USZ June 2002 7 Chromium Concentration USZ June 2002 8 Potentiometric Surface Map (USZ) May/June 2001 9 TCE Concentration LSZ (Upper Portion) June 2002 10 Chromium Concentration LSZ (Upper Portion) June 2002 11 Potentiometric Surface Map (Upper Portion) June/July 2001 12 TCE Concentration LSZ (Middle Portion) June 2002 13 Chromium Concentration LSZ (Middle Portion) June 2002 14 Potentiometric Surface Map (Middle Portion) June/July 2001 15 TCE Concentration LSZ (Lower Portion) June 2002 16 Chromium Concentration LSZ (Lower Portion) June 2002 17 Potentiometric Surface Map (Lower Portion) June/July 2001

LIST OF TABLES

No. Title

1 Chronology of Activities for Building 3001 OU2 Summary of Remedy Development and Implementation Activities at Building 3001 3 Groundwater Extraction Wells by Hydrogeologic Zone

LIST OF APPENDICES

APPENDIX A List of Documents Reviewed APPENDIX B Sight Inspection Check List

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ACRONYMS AND ABBREVIATIONS

AFB Air Force BaseARAR Applicable or relevant and appropriate requirementATSDR Agency for Toxic Substances and Disease RegistryBattelle Battelle Memorial InstituteBHRA Baseline human health risk assessmentBTEX Benzene, toluene, ethylbenzene, and xylenesB&V Black & Veatch Waste Science and Technology CorporationCERCLA Comprehensive Environmental Response, Compensation, and Liability ActCOPC Chemical of potential concernCr ChromiumCSM Conceptual site modelCWA Clean Water ActDCE DichloroetheneDNAPL Dense non-aqueous phase liquidEPA U.S. Environmental Protection AgencyERA Ecological risk assessmentFFA Federal facilities agreementGWTP Groundwater treatment plantHHRA Human health risk assessmentHHRA I Human health risk assessment (first annual)HHRA II Human health risk assessment (second annual)HHRA III Human health risk assessment (third annual)HI Hazard indexHKS Harry Keith & Sons, IncorporatedIRP Installation Restoration ProgramIWTP Industrial wastewater treatment plantLSZ Lower saturated zoneMCL Maximum Contaminant Levelmg/Kg Milligrams per kilogrammg/L Milligrams per literNPDES National Pollutant Discharge Elimination SystemNPL National Priority ListNTA North Tank AreaOAC Oklahoma Administrative CodeOC-ALC Oklahoma City - Air Logistics CenterOC-ALC/EMPE Oklahoma City - Air Logistics Center/Environmental Management Programs,

Engineering BranchOCC Oklahoma Corporation CommissionODEQ Oklahoma Department of Environmental QualityO&M Operation and MaintenanceOSDH Oklahoma State Department of HealthOU Operable UnitPAH Polycyclic Aromatic HydrocarbonParsons ES Parsons Engineering Science, Inc.PCB Polychlorinated biphenylPCE Tetrachloroethene (Perchloroethene)ppb Parts per billion

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POL Petroleum oil lubricantsppm Parts per millionPRP Potentially responsible partyRA Risk assessmentRAO Remedial action objectiveRBCA Risk-based corrective actionRCRA Resource Conservation and Recovery ActRGO Remedial goal optionRI Remedial investigationRME Reasonable maximum exposureROD Record of DecisionSDWA Safe Drinking Water ActSF Slope factorSVOC Semi-volatile organic compoundTBC To-be-consideredTCE TrichloroethyleneTPH Total petroleum hydrocarbonTTNUS Tetra Tech NUS, Inc.USACE United States Army Corps of EngineersUST Underground storage tankUSZ Upper saturated zoneVEP Vacuum Enhanced PumpingVOC Volatile organic compoundWCFS Woodward-Clyde Federal Services

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EXECUTIVE SUMMARY

The remedy for the Building 3001 Operable Unit 1 site at Tinker Air Force Base, Oklahoma included thefollowing:

Building 3001 Groundwater: Extraction of contaminated groundwater from the perched zone, top ofregional aquifer zone and regional aquifer zone via extraction wells. Treatment of the contaminatedgroundwater in a treatment facility constructed specifically for the Building 3001 remedial action. Thetreated water will be reused in industrial operations.

Pit Q-51: Removal of approximately 45 gallons of liquid, steam cleaning of the pit, analysis of the liquidand washwater, and disposal in a facility that is approved to receive CERCLA waste. Backfilling the pitwith sand and covering it with an 8-inch concrete cap to prevent future use.

North Tank Area (NTA): Installation of a floating fuel product removal system to recover fuel productfloating above the groundwater table. Recovered fuel will be disposed of at a RCRA approved facility. Thegroundwater will be treated at the new Building 3001 treatment plant. In addition, a vapor extraction systemwill be installed to remove fuel vapors from the subsurface soils, which will then be destroyed in a thermalcombustor. Finally, a 750-gallon waste tank will be removed and disposed of, and a 235,000 gallon fuel oiltank will be properly closed.

Because the proposed remedial method for NTA was not efficient, the system was upgraded to includedual-phase extraction (or vacuum enhanced pumping (VEP)). This technology not only addressesremediation of the vapors (as specified in the ROD), but also adds remediation of contaminatedgroundwater as well.

The Building 3001 pump and treat system was installed and the treatment plant was placed on line in 1994.This is the trigger for the start of the five year reviews.

The assessment from this five-year review was that the remedies were constructed and operated inaccordance with the requirements of the Record of Decision (ROD). The remedy is functioning as designed;however, the remedy is not optimal An Explanation of Significant Differences (ESD) was submitted to theEPA requesting a temporary shutdown of the extraction wells around Building 3001 in order to obtain‘pre-system operation’ ambient and hydrogeological conditions as well as monitor plume stability. Thisadditional data is intended for use in optimizing the remediation of the contaminant plume under Building3001. The ESD was approved by regulatory agencies in May 2003. Preparations for system shut-down areunderway at this time.

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SECTION 1 INTRODUCTION

The U.S. Air Force has conducted a five-year review of the remedial action implemented at the Building3001 Federal Facilities National Priorities List (NPL) site at Tinker Air Force Base in Oklahoma. Thisdocument constitutes the second Five-Year Review. The previous review was completed in September1998. The primary purpose of the review is to determine whether the remedy remains protective of humanhealth and the environment. Five-year review reports identify deficiencies, if any, and recommendations toaddress them. Five-year review reports document the evaluation of the implementation of the remedy andoperation and maintenance (O&M), as well as the continued appropriateness of remedial action objectives(RAOs), including cleanup levels at a site.

This review is required by statute. Section 121©) of the Comprehensive Environmental Response,Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments andReauthorization Act of 1986 (SARA), and Section 300.430 (1) (4) (ii) of the National Oil and HazardousSubstance Contingency Plan (NCP), require that periodic (no less often than every five years) reviews beconducted for sites where hazardous substances, pollutants, or contaminants remain at the site above levelsthat allow for unlimited use and unrestricted exposure following the completion of all remedial actions.

Executive Order 12580 delegates the authority to conduct five-year reviews to the Departments of Defenseand Energy, where either the release is on, or the sole source of the release is from, any facility under thejurisdiction of those departments In the Federal Facilities Agreement signed on December 9, 1988 betweenthe U.S. Air Force, EPA, and the Oklahoma State Department of Health (succeeded by the OklahomaDepartment of Environmental Quality in 1993), the U.S. Air Force was established as the lead agency forremediating the Building 3001 NPL site.

This review is being conducted following EPA guidance Five-year reviews are conducted as a matter ofpolicy at: 1) sites where no hazardous substances will remain above levels that allow unlimited use andunrestricted exposure after completion of remedial actions, but the cleanup levels specified in the Record ofDecision (ROD) will require five or more years to attain; and, 2) sites addressed before SARA at which theremedy, upon attainment of cleanup levels, will not allow unlimited use and unrestricted exposure. TheBuilding 3001 NPL site is subject to the five-year review because hazardous waste remains onsite andcontinued monitoring is required.

The trigger for this statutory review is the implementation of the remedial action at the Building30010perable Unit (OU) in 1993 The groundwater treatment plant was physically completed in February1993, and operational shakedown activities followed. Continuous operations of the groundwater treatmentplant commenced in June 1994.

SECTION 2BACKGROUND

PHYSICAL CHARACTERISTICS

The Building 3001 NPL site is located within the northeast quadrant of Tinker Air Force Base (AFB), OK(Figure 1). Included in the NPL site are the main stem of Soldier Creek, and all tributaries of Soldier Creekoriginating on Tinker AFB. The Building 3001 NPL site is designated as Operable Unit 1 (OU 1) (Figure 2).

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As stated in the ROD, the Building 3001 site includes the building complex (covering 50 acres), the NorthTank Area (located at the north end of the building), Pit Q-51 (located inside B3001), and the surroundingareas encompassed by the lateral extent of the groundwater contaminant plume (Figure 2). The entire OUencompasses an area of approximately 220 acres.

LAND AND RESOURCE USE

Prior to 1941, the site was located on undeveloped pasture and prairie lands. There were some agriculturalactivities and ranching but no known industrial uses prior to 1941. Beginning in 1941, 960 acres of land,including the area now occupied by the IWTP, were donated to the Army Air Corps by the City ofOklahoma City for the construction of the Midwest Air Depot. Renamed Tinker Field in 1942 andsubsequently Tinker Air Force Base in 1948, the entire base now covers 5,277 acres

The site is in the northeast quadrant of what became Tinker AFB, which is now the most industrialized areaof the base. The Building 3001 complex has been involved in reconditioning, modifying, and modernizingaircraft, including jet engine overhaul and missile repair. The industrial processes used or generatedsolutions containing organic chemicals including trichloroethylene (TCE), tetrachloroethylene (PCE) andmetals such as chromium. Fuels for the boiler system included No. 2 fuel oil stored at the NTA. Diesel,gasoline, and waste oil were also stored at the NTA

The Producing Zone (PZ) is a drinking water aquifer that exists at around 700 feet in depth. Shallower waterbearing zones exist in both the USZ and the LSZ, however, these are not used as drinking water aquifers.Dominant groundwater flow direction is to the southwest.

The land use plan for the B3001 operable unit is zoned only for industrial and heavy industrial use.

Surrounding Community The B3001 site and Tinker AFB lie within an area representing transition from residential andindustrial/commercial land use on the north and west to agricultural land use to the east and south SoldierCreek and its tributaries, which flow northwest through the area, are bordered by recreational and residentialareas with some areas supporting commercial and industrial land use. Some off-base industries, such as ametal plating facility and a dry cleaning facility, and commercial facilities such as gas stations, auto repairfacilities, and a closed sanitary landfill are located within the drainage basin. In addition, three schools,Soldier Creek Elementary, Steed Elementary, and Monroney Junior High are located within the drainagebasin. There are ten public parks within the genera] vicinity of Tinker AFB, including the Joe B. Barns,Fred F. Meyers, Kiwanis, and Lions Parks. A public golf course is also located north of the base. Five trailerparks are located north and northeast of Tinker AFB.

The land use plan for the area immediately north of Tinker AFB, between Sooner Road and DouglasBoulevard includes all levels of land use. The areas between Sooner Road and Midwest Boulevard(northwest of the base) are zoned primarily for housing (single and multifamily units) and low to mediumcommercial use. The area north of the base, between Midwest Boulevard and Douglas Boulevard, has beenincorporated as part of the ‘accident potential zone’ for the base runways.

Soldier Creek, which flows from Tinker AFB into adjacent neighborhoods, is reportedly used for wadingand playing by area children and is large enough to support edible fish. No hunting or fishing has beenreported to occur in the immediate area outside of Tinker AFB. Hunting is not permitted on base and fishingis not permitted in Soldier Creek within base boundaries. Beneficial uses of Soldier Creek includeagriculture, secondary recreation, process and cooling water, and aesthetics. Soldier Creek also supports awarm-water aquatic community.

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Human Use of Resources The most important source of potable groundwater in the Oklahoma City metropolitan area is the CentralOklahoma aquifer, which is commonly referred to as the “Garber-Wellington aquifer.” Tinker AFBpresently obtains the majority of its water supplies from wells that are completed in the Garber-Wellingtonaquifer. Base wells range from 700 to 1,100 feet in total depth, with yields ranging from 205 to 250 gallonsper minute (gpm).

On the east side of Tinker AFB, the Garber-Wellington aquifer has been classified as a Class IIA aquifer bythe State of Oklahoma, indicating that it provides groundwater from a major, unconfined basin that iscapable of being used as a drinking water supply with little or no treatment (OAC 785:45-7-3). The westernportion of the Garber-Wellington aquifer basin, which extends from the west side of the base to just west ofOklahoma County is classified as a Class IIC aquifer, a major confined groundwater basin. Tinker AFB andthe nearby communities of Midwest City and Del City derive a portion of their water supply from theGarber-Wellington aquifer.

Until 1993, groundwater was used as a domestic water source by several of the residents living within andadjacent to the boundaries of the site. Most of these wells were removed from service in 1994 aftermunicipal water distribution lines were conveyed to and installed at the residences and businesses. Thereare no off-base wells known to be used for drinking water purposes. All of the water supply wells on TinkerAFB are routinely sampled for contaminants.

CONTAMINANTS

The Air Force Installation Restoration Program (IRP) Phase I identified potential sources of contaminationthrough records searches and reviews of waste management practices. The first report of a release to theenvironment occurred in 1983 during routine wellhead sampling and testing. TCE and PCE were detected intwo of the base water supply wells (WS 18 and WS 19) at Building 3001. A Phase II IRP investigation wasconducted in 1984 to confirm and quantify contamination resulting from past waste storage practices atBuilding 3001. Sampling was also initiated at East and West Soldier Creek in 1984. Sample resultsindicated the presence of chromium and solvent contamination in the sediment and surface water. In 1985,fuel and free product contamination were found at the NTA. In September 1987, the Soldier Creek/Building3001 site was evaluated under the hazard ranking system with a score of 42.24 and was placed on the NPL.

Remedial investigations (RIs) were conducted at the Building 3001 OU between 1986 and 1987 todetermine the nature and extent of contamination associated with Building 3001, the NTA, and Pit Q-51.The areas with highest concentrations of groundwater contamination were located beneath Building 3001,the NTA, and the Southwest Tank Area (shown on Figure 3). TCE and chromium were considered theprimary groundwater contaminants, since their maximum concentrations were higher than the othercontaminants and they were consistently detected over a large portion of the site. Other significantcontaminants included dichloroethylene (DCE), PCE, acetone, toluene, benzene, xylenes, lead, nickel, andbarium.

Samples collected from sludge in Pit Q-51 in 1986 indicated TCE, cadmium, chromium, and leadcontamination. Leakage from this pit and other similar structures is considered as the source of soil andgroundwater contamination beneath Building 3001.

Fuel product in the form of No. 2 fuel oil was discovered beneath a leaking 235,000-gallon undergroundstorage tank (UST) at the NTA. As a result, the soils and groundwater beneath the NTA and the north end ofBuilding 3001 were heavily contaminated with fuel and other organic compounds.

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The groundwater used by residents and the work force of Tinker AFB was identified as an exposurepathway. Potential points of exposure included water supply wells and discharge to surface water bodies.Exposure with long-term health effects was deemed a possibility in the 1988 baseline risk assessment. Achronology leading to the NPL listing is provided in Table 1.

Table 1 Chronology of Activities Leading to NPL Listing for Building 3001 OU

Investigation/Activity Description Event Date (Source)

IRP Phase I records searchconducted

Records search conducted to identify pastwaste disposal activities that may havecaused environmental contamination

1981 (ES, 1982)

USTs removed at North TankArea

Two tanks (800-gallon waste oil tank and13,000-gallon gasoline tank) removed atNTA.

1983-1985 (Battelle,1993a)

IRP Phase IIConfirmation/Quantificationinvestigation conducted

TCE detected in groundwater in thevicinity of 1983Building 3001.

(Radian, 1985a and 1985b)

Supply wells in Building3001 taken out of service

Water supply wells (WS-18 and WS-19)located inside Building 3001 taken out ofservice.

1984 (EngineeringEnterprises, 1984)

Supply wells in Building3001 plugged

Water supply wells (WS-18 and WS-19)located inside Building 3001 plugged.

1986 (Dansby &Associates, 1986)

Remedial investigation andrisk assessment conducted

Pit Q-51 identified as containinghazardous contaminants. Investigationconducted to determine nature and extentof contamination

1986-1987 (USACE,1988a and 1988b)

NPL listing Building 3001 added to the NPL July 22, 1987

INITIAL RESPONSE

The U.S. Environmental Protection Agency (EPA), U S. Air Force, and Oklahoma State Department ofHealth (succeeded by the Oklahoma Department of Environmental Quality in 1993) signed a FederalFacilities Agreement (FFA) designating the Air Force as the only Potentially Responsible Party (PRP).Response actions initiated prior to the ROD are discussed below.

Between 1983 and 1985, two USTs, Tank 3403 (300 gallon waste oil tank) and Tank 3405 (13,000 gallonleaking gasoline tank), were removed from the NTA. Inside of Building 3001, the contents of three pitscontaining solvent and metals contamination were removed in 1985 The pits were backfilled and cappedwith concrete. Water supply wells WS 18 and WS 19 were plugged and abandoned in 1986 WS 17 wasplugged and abandoned in 1988.

The Building 3001 ROD was signed in August 1990. Soils and groundwater contamination remain onsiteand are in remediation. Groundwater concentrations remain above maximum contaminant levels (MCLs).

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SECTION 3 REMEDIAL ACTIONS

The selected remedy for the Building 3001 OU was comprised of three components: the groundwaterassociated with Building 3001 activities, Pit Q-51 contaminants, and the NTA impacts. This sectiondiscusses the components and operation and maintenance aspects of the Building 3001 OU. Figure 4illustrates the extraction well field associated with the system.

Remedy Selection

The Record of Decision (ROD) signed in August of 1990, addressed remedies for groundwater beneathBuilding 3001. In addition, an ESD as well as responses to EPA comments to the ESD were submitted in2002. Regulatory approval of the ESD was gained in May 2003

The remedial actions selected in the ROD incorporated the following components:

Building 3001 Groundwater• Addition of monitoring wells in order to monitor the groundwater contaminant plume. • Extraction of contaminated groundwater from the perched water zone, top of regional water zone,

and regional water zone by exterior and interior extraction wells. • Treatment of the contaminated groundwater in a treatment facility constructed specifically for the

Building 3001 remedial action. • Treatment of volatiles contamination by air stripping and carbon adsorption. • Treatment of metals by chemical reduction and precipitation. • Reuse of the treated water in TAFB’s industrial operations. • Disposal of the sludge from groundwater treatment operations at an offsite RCRA-permitted facility

approved to receive CERCLA waste.

Pit Q-51• Removal of approximately 45 gallons of liquid. • Steam cleaning of the pit, analysis of the liquid and wash-water, and disposal of wastes in a facility

that is approved to receive CERCLA waste. • Backfilling of the pit with sand and covering with an 8-inch thick concrete cap to prevent future use.

North Tank Area• Installation of a floating fuel product removal system to recover fuel floating above the groundwater

table. Disposal of the recovered fuel at a RCRA-approved facility.• Treatment of the recovered groundwater at the Building 3001 treatment plant • Installation of a vapor extraction system to remove fuel vapors from the subsurface soils.• Thermal combustion of fuel vapors recovered by the removal systems. • Removal and disposal of a 750 gallon waste tank and proper closure of a 235,000 gallon fuel oil

tank.

Remedy Implementation

A chronology of the remedy development and implementation activities for the Building 3001 OU isprovided in Table 2 below.

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Table 2 Summary of Remedy Development and Implementation Activities at Building 3001 OUInvestigation/Activity Description Date (and Source)

Remedial Investigation. Determine extent of groundwater contaminationfrom Building 3001.

1988 (USACE)

Feasibility study conducted Feasibility study for Building 3001 site evaluatedalternatives for remediating groundwater plume.

1988 (USACE)

FFA signed. Federal Facilities Agreement signed by TinkerAFB, EPA, and Oklahoma State Department ofHealth.

December 1988 (EPA)

Quarterly RI conducted. Supplemental remedial investigation conducted. 1988-1989 (USACE)

ROD signed. Record of decision for Building 3001 site,including Pit Q-51 and NTA, signed. Identifiedselected alternatives.

August 1990 (USACE)

Groundwater collection pilottest conducted at Building3001.

Tested proposed groundwater collection andtreatment system on a small-scale

September 1990(USACE, 1990b)

Product recovery initiated atNTA.

Product recovered from seven monitoring wellsinstalled at the NTA

May 1991 (Battelle)

Additional recovery wellsinstalled at NTA.

Two product recovery wells (RC-1 and RC-2)installed at NTA

December 1991 (CDM)

Pit Q-51 remediated. Pit Q-51 contents were removed and disposed ofoff-site. Decision document prepared. Site closed.

1991 (OC-ALC)

Modeling and system designconducted.

Modeled groundwater flow and designed full-scalegroundwater collection and treatment system.

1991 (Black & Veatch)

In-situ respiration and airpermeability tests in NTA soils.

Two vapor extraction wells, five tri-level vaporpressure monitoring points, and two blower unitswere installed for in-situ respiration and airpermeability tests.

March 1992 (Battelle)

One UST removed, oneabandoned at NTA.

1,200 gallon sump pump tank removed in April,and 235,000 gallon fuel oil tank abandoned inplace in May.

April and May 1992(Parsons ES andBattelle)

Additional recovery wellsinstalled at NTA.

Four additional recovery wells (RC-3, RC-4, RC-5,and RC-6) installed to enhance product removalat the NTA

September 1992 (Roy F. Weston)

Groundwater treatment plant(GWTP) construction initiatedat Building 3001.

GWTP construction initiated and 33 groundwaterextraction wells installed.

1992 (Black & Veatch)

GWTP constructioncompleted and intermittentpumping initiated,

GWTP construction completed and intermittentpumping of Building 3001 groundwater plumeinitiated.

February 1993 (Tinker AFB)

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Investigation/Activity Description Date (and Source)

Fracturing demonstrationproject conducted at NTA.

Fracturing demonstration project was conducted todetermine if fracturing could enhance productrecovery at the NTA.

Summer 1993(Parsons ES & Battelle)

Focused remedialinvestigation conducted atNTA.

Supplemental field investigation conducted at theNTA to further delineate the extent of productcontamination.

Oct.-Dec. 1993(Parsons ES & Battelle)

Extraction system operations Continuous pumping of groundwater extractionfully initiated. wells at Building 3001 site began.

June 1994 (Tinker AFB)

Expanded fracture injectiontreatment at the NTA.

Installed additional recovery wells at the NTA andfracture treated the uppermost aquifer.

January 1995 (Parsons ES)

Building 3001 remediationsystem evaluated.

Results from one full year of operation are evaluatedto determine what ways the system could beoptimized. Also, the volume of contaminationremoved and remaining in groundwater estimated.Estimates of the time to recover remainingcontaminants are made.

1996 - ongoing(Parsons ES)

Remediation continued Product recovery at NTA and groundwater extractionand treatment at Building 3001 continued.

1994 - ongoing

Remedial ProcessOptimization Report

Study performed to evaluate the effectiveness of thecurrent pump/treat system.

December 2000(AFCEE @ Parsons ES)

TI Waiver Work Plan Initiate the data needed for support of Technical andImpractability Waiver for the Building 3001 OU.

January 2001(Parsons ES)

SVE Pilot Test Work performed to determine if SVE is a viableremediation technology

April 2001 (Parsons ES)

ESD Submitted in order to obtain approval to shut downpump and treat system in order to obtain ambientbackground conditions.

April 2002(Tinker AFB)

OPERATION AND MAINTENANCE REQUIREMENTS

Elements of the Building 3001 OU that require O%M include: 1) the extraction well field and groundwatertransport system associated with Building 3001 groundwater; 2) the groundwater treatment plant (GWTP)for Building 3001 Groundwater and 3) the product recovery system at the NTA. The removal of thecontents from Pit Q-51 and its off-base disposal was a permanent remedy and therefore required no O&M.These elements are discussed in further detail below.

Extraction Well Field and Groundwater Transport System The Building 3001 extraction well network consists of 33 extraction wells installed in three aquifer zones,as shown in Table 3 below. It should be noted that the TOR-series wells are completed primarily in theupper portion of the lower saturated zone (LSZ), but two of the wells also penetrate the lower portion of theLSZ.

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Table 3Groundwater Extraction Wells by Hydrogeologic Zone

Tinker AFBGroundwater

Conceptual ModelTinker AFB, 1994)

U.S. Army Corps ofEngineers Designation

(USACE, 1988a)Number of

horizontal wellsNumber of

vertical wells

USZ P-1 through P-19(Perched Aquifer)

3 16

LSZ (upper) TOR-1 through TOR-7(Top of Regional Aquifer)

1 6

LSZ (lower) R-1 through R-7 (Regional Aquifer)

1 6

Each well is surrounded by a water-proof well vault containing the well head, piping from the well into thepipe manifold which transports the water to the GWTP, electrical equipment, and instrumentation. Thepump in each well pumps with sufficient head to carry the extracted water to the influent holding tank of theGWTP.

This system is operated and maintained by the same staff responsible for operating the GWTP. Somerequirements for the extraction and transport system overlap with the GWTP requirements. Specific O&Mrequirements for this system are as follows:

1. Perform Daily Inspections and Operations Tasks - see that wells pump according toschedule; observe equipment, instruments, and unit processes for proper operation; maintaindaily operating log in current condition; check instruments, controls, and alarms for properoperation; check for visible sign of leaks; collect samples; check sampling results andprovide proper feedback to well field operation and control.

2. Perform Periodic Inspections and Routine Maintenance of Equipment -perform periodicinspections of pumps, valves, and piping to identify wear, needs for special maintenance, andinsure proper operation; perform lubrication at specified intervals; perform cleaning atspecified intervals or as required; repair as necessary.

3. Perform Instrument Inspections and Calibration – periodically, at specified intervals, inspectall instruments including meters, controllers, and electrical equipment for proper working,needs for maintenance; clean; calibrate; repair as necessary.

4. Perform Well Field Maintenance – perform periodic inspections of extraction and monitoringwells; perform maintenance and well redevelopment tasks as needed.

2) Groundwater Treatment Plant (GWTP) The GWTP is contained in a pre-engineered meta] building. This building also contains chemical storagefacilities, a maintenance area, and a control room, which includes office space. The GWTP is located east ofBuilding 3001 and lies within the secured area of the base. An alarm on the door to the building alerts theon-duty operator to the arrival of anyone into or out of the building.

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The GWTP consists of the following components:• An influent holding tank to which the extracted water is pumped. • An air stripper coupled with a vapor phase activated carbon system for the removal of volatile

organics. • A chemical reduction system for the reduction of hexavalent chromium. • A chemical precipitation system for the precipitation and removal of trivalent chromium and other

metals. This system consists of chemical addition systems, flocculation, and sedimentation in aninclined plate settler.

• Granular media filtration for the removal of additional suspended solids. This filter is a “movingbed” type (Dynasand brand).

• Sludge handling using a sludge holding tank, recessed plate filter press, and thermal sludge dryer.Dried sludge is disposed in a RCRA landfill certified to receive CERCLA wastes.

• An effluent holding tank from which the treated water is pumped for reuse.

O&M requirements for the GWTP: 1. Develop and Maintain Adequate Operations and Supervisory Staff – hire, train, and supervise O&M

staff. 2. Meet Performance Requirements – keep system running, keep down time to a minimum, meet

performance specifications including required effluent quality, air quality, and sludge quality; advisemanagement of any major problems or potential major problems.

3. Meet Reporting Requirements perform system monitoring, collect required data, perform laboratoryaudits, if required, develop and maintain system for data management, submit reports as required,make notifications of abnormal operating conditions, maintain daily operations logs, maintenancelogs, spare parts inventory, and other logs required, perform all waste manifesting in a timelymanner.

4. Perform Daily Inspections and Operations Tasks – manage water flow through system includingassociated air flows, sludge flows, and chemical feeds; observe equipment, instruments, and unitprocesses for proper operation; maintain daily operating log in current condition; check instruments,controls, and alarms for proper operation; check for visible sign of leaks; collect samples; checksampling results and provide proper feedback to GWTP operation and control.

5. Perform Periodic Inspections and Routine Maintenance of Small Equipment – perform periodicinspections to identify wear, needs for special maintenance, and insure proper operation; performlubrication at specified intervals; perform cleaning at specified intervals or as required; repair asnecessary.

6. Perform Instrument Inspections and Calibration – periodically, at specified intervals, inspect allinstruments for proper working, needs for maintenance; clean; calibrate; repair as necessary.

7. Perform Inspections and Maintenance of Major Equipment – inspect major equipment (majorrotating equipment, other equipment with moving parts, and large and/or complicated pieces ofequipment) at specified intervals; perform routine maintenance including cleaning, lubrication,performance checks, etc., perform preventive maintenance tasks; repair, recoat, and replace asnecessary; schedule next inspection.

8. Keep and Update Maintenance Records – using the prescribed system, keep records up to date,regarding maintenance history, equipment replacement, maintenance advisories, etc.

9. Perform Periodic Leak Inspections – in addition to daily observations for leaks, make more thoroughinspections on a periodic basis; report findings.

10. Perform Periodic Infrastructure Inspections – periodically inspect building, loading/unloading areas,on-site maintenance area, and utilities supply points for repair and maintenance needs; be aware ofand correct any hazards to operators, visitors, delivery personnel, etc.

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11. Employ Proper Emergency Procedures - keep staff properly trained in emergency operatingprocedures, response procedures, and safety practices; update requirements as necessary.

12. Maintain Spare Parts Inventory – update inventory as parts are used; periodically review and updaterequired inventory based on maintenance history.

13. Review and Update O&M Manual and Operating Procedures - perform periodically as required.

Product Recovery System at NTA The original design of the product recovery system specified a dual phase recovery system consisting of ahydrocarbon recovery pump and a groundwater pump. The groundwater pump was installed to depress thewater table and create a cone of depression around the wellbore so the hydrocarbon pump could collect thephase-separated hydrocarbon off the surface of the water table. This system was installed in 1991, but thegroundwater depression pumps are no longer used. It was intended that the water pumped from below theproduct would be discharged to the Building 3001 moundwater treatment system; however, this designapproach was never realized. The pneumatic hydrocarbon pumps are still run intermittently to skim productfrom the surface of the water table in 2 of the recovery wells. An O&M manual was developed for thesystem, which was expanded to a total 6 wells and included submersible electric pumps as well as thepneumatic pumps. The original pumping schedule and protocols are no longer used except for routinemaintenance of the compressor and repairs (Battelle, 1993a).

Three additional dual pump pneumatic recovery wells were added in 1995 (Parsons ES, 1995). Tworecovery wells were installed on the west side of Building 3001 and one monitoring well was converted to arecovery well north of the abandoned 235,000-gallon fuel tank. All pump controls are maintained inside of alocked metal building within the fenced and secured compound.

Perimeter wells around the NTA are equipped with hydrocarbon sensor probes in the event fuel begins tomigrate away from the NTA An ORM Plan was developed to monitor these sensors (Parsons ES, 1996c).The sensors record water level and other groundwater data and have an illuminating alarm at the well-headto signal if free-phase hydrocarbons are entering the well.

Operation and Maintenance Activities

Experienced environmental contractors conduct O&M activities. The contractor personnel are trained inoperational and health and safety procedures relevant to the job performance. O&M activities related to theextraction and transport system include the necessary tasks to carry out the responsibilities enumerated inthe next section. Based on the inspections associated with this project, all of the required activities are beingeffectively and regularly performed.

Groundwater Treatment Plant (GWTP) O&M of the GWTP is currently contracted to TTNUS. TTNUS is responsible for operator staffing, operatortraining, engineering support, system maintenance, monitoring, and reporting results to the on-site TinkerAFB personnel. The operations staff performs some maintenance while other tasks are subcontracted byTTNUS to outside vendors. TTNUS is also responsible for containerizing dewatered and dried sludge fromthe sludge handling operation and recovered organics from the air stripping operation for shipment offsite.This waste is transported and disposed under another Tinker AFB contract. TTNUS’s responsibilities at theGWTP begin at the influent holding tank (Tank T-1) and continue to the pumping of treated effluent into thereuse system downstream of the effluent holding tank (Tank T-2). TTNUS is also responsible for operatingthe extraction well field and transport system and monitor these components from the GWTP control room.

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The GWTP is staffed with an operator 24 hr/day, 7 days/wk. Process engineering support is available from aTTNUS staff person located at the base. At the time this inspection was performed, the lead operator wasMr. Jim Holcomb. Jason Flaming (OC-ALC/EMPE) is responsible for the TTNUS contract. Mr. Flamingconducts regular site visits. Based on the inspections associated with this project, all of the requiredactivities are being effectively and regularly performed.

NTA Product Recovery System O&M of the product recovery system is currently contracted to JA Jones. Product recovery wells are eitherequipped with skimmer pumps that operate automatically or wells are periodically pumped or purged forfree phase hydrocarbon by the contractor. The contractor also performs weekly gauging of the tanks and sitemonitoring wells. The NTA site manager for Tinker AFB is Mr. Dan Hunt (OC-ALC/EMPE).

SECTION 4 REMEDIAL ACTION OBJECTIVES

ARAR’s reviewed included Maximum Contaminant Levels (MCLs) established under the Safe DrinkingWater Act (SDWA), Clean Air Act (CAA) requirements under which relate to the emission standards forambient air quality, and RCRA requirements for the management of hazardous waste.

Building 3001 No changes in MCLs or RAOs have been effected since the previous Five-Year Review.

North Tank Area At this time, the appropriate groundwater ARARs at the NTA are the federal MCLs as promulgated underthe SDWA. Other ARARs include Oklahoma Water Quality Standards for the contaminants of concern andlevels for benzene, toluene, ethylbenzene, and xylenes (BTEX) and total petroleum hydrocarbons (TPH) ingroundwater and soils for petroleum, oil, lubricating (POL)-contaminated sites as established under theOklahoma Corporation Commission (OCC).

Because the NTA is a CERCLA site, MCLs are the primary ARARs for the site. Since the previousfive-year review, MCLs for the contaminants of concern have not changed.

Pit Q-51 Since the contents of Pit Q-51 were permanently removed from the Building 3001 site and disposed at afacility approved to receive the waste material, all ARARs have been met.

SECTION 5 PROGRESS SINCE LAST FIVE-YEAR REVIEW

Protectiveness Statement from ROD

The remedial actions would remove contaminated groundwater from the upper regions of theGarber-Wellington aquifer and treat it to acceptable levels for reuse in the TAFBs industrial operations. Byremoving and treating the contaminated groundwater, destruction of the mobile contaminants includingmost of the known and suspected carcinogens will be achieved.

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The EPA reported acceptable carcinogenic risks fall within the range of 1.0 X 10-4 to 1 0 X 10-5. Thecarcinogenic risk for the site if no action were taken is 1.2 X 10-7, which falls outside acceptable limits. Thisnumber will be further reduced when the proposed remedial action is implemented. Therefore, nounacceptable short-term risks would result from implementation of the remedial alternative.

The final remedial action would prevent the contaminants from migrating further horizontal and verticallywithin the aquifer thus reducing the risk of exposure to the drinking water zone in the lower aquifer.Unacceptable short-term risk or cross-media impacts will not be caused by implementation of the selectedremedial alternatives. The remedial action will be permanent and will adequately protect human health andthe environments.

Protectiveness Statement (previous review)

While it appears that improvements should be made to the Building 3001 extraction well field, the currentremedial action is protective of human health and the environment.

Status of recommendations and follow-up actions from last review

See Section 7, Issues From Previous Review.

Results of Imp1emented Actions and Intended Affect Although the system is installed and operated in accordance with the ROD, attainment of MCLs for TCE isunrealistic. At the time of the ROD, it was estimated that 85% of the contamination will be removed in 5years. Based on actual data, VOC mass removal rates from groundwater have varied during the operation ofthe extraction system through February 2000, but have not yet reached asymptotic levels. The system hasremoved approximately 15 drums (about 8,625 pounds) of VOCs, including CAHs, from the onset of thesystem operation in June 1994. The recovered contaminants consist mainly of TCE (about 75 %) with theremainder consisting of benzene, toluene, PCE and 1,2-DCE. These statistics represent recovery from theentire extraction system including the USZ and LSZ. Optimistically speaking, if current VOC removal ratesare sustained, approximately 52,000 pounds of total VOCs could be removed by the year 2024. Based oncurrent operating costs, the total cost for system expenditures would be projected to be $25.9 million in theyear 2024 In reality, the projected removal rates will drop substantially over time thus increasing projectedoperating costs for a system that will never achieve current clean up goals.

SECTION 6 FIVE-YEAR REVIEW PROCESS

Site visits and interviews were conducted by Sara Sayler of the Oklahoma City Air Logistics CenterEnvironmental Management Directorate Programs Engineering division (OC-ALC/EMPE) at Tinker AFB.Site inspection checklists for NTA and Building 3001 can be found in Appendix B. The O&M contractorfor the sites is TTNUS. Both the environmental management directorate, program engineering division(EMPE) and TTNUS maintain a constant presence at the sites.

Community Involvement

Community involvement was initiated at the October 29th, 2002 community advisory board (CAB)meetings by announcing that a Five-Year Review process was underway. In addition, questions, comments

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or concerns were solicited from the public during the January 28, 2003 CAB meeting. No comments havebeen received from the public at this time.

Interviews

Building 3001 Groundwater: Interviews were conducted with Jason Flaming (OC-ALC/EMPE) currentproject manager of remediation system and plant oversight In addition, interviews were conducted with JimHolcomb of the contract operating company, TTNUS, on November 12, 2002.

North Tank Area: Interviews were conducted with Dan Hunt (OC-ALC/EMPE) the site manager on April 7,2003.

Pit Q-51: Because Pit Q-51 is closed according to the ROD, no interviews were conducted as part of thisfive-year review.

Site Visits

Building 3001 Groundwater A site visit to the Building 3001 groundwater treatment plant and extraction well field was conducted onApril 16th, 2003. The site visit was attended by Jason Flaming (EMPE) and Jim Holcomb of TTNUS.

During the Groundwater Treatment Plant (GWTP) inspection several key documents were reviewedincluding: daily and monthly operation logs for the GWTP, quarterly reports, chemical use inventories, anddesign drawings. Discussions were held at the GWTP with plant operating and supervisory personnel tofurther assess operating condition of equipment, level of maintenance, housekeeping practices, performancehistory and operator knowledge.

North Tank Area A site visit was completed on the afternoon of April 7, 2003. This visit was attended by the OC-ALC/EMPEsite manager’s alternate, James Dawson, and was conducted to establish the current conditions of the siteand monitoring systems.

During the previous Five-Year Review, the recovery wells, monitoring wells, product recovery tanks, flowlines, flow controls were observed and inspected for performance. No leaks, spills, or other potentialreleases were observed during the inspection and no deterioration of primary or secondary containment wasevident; however, the above-ground carrier lines from the well heads to the pump controls are weatheredand aging. The site manager stated that the carrier lines are replaced annually. The product pumping andrecovery schedule were discussed and a list of wells currently recovering product was evaluated. O&Mplans were not available onsite.

Since the previous review, things have changed substantially. First, the recovery system described in thefirst five-year review was a pneumatically driven skimming system Those carrier lines were completelyremoved in 1999 and replaced with VEP lines through the same conduits. Therefore, there are no longer anyabove ground flow lines. Currently, all recovered groundwater and contamination is pumped to thetreatment unit and manifolded to a liquid ring pump. Although this represents a change from the initia1system that was installed as a result of the ROD, the essential remediation mechanics remain the same.While the ROD specifies a vapor extraction remedy, the upgraded system goes one step farther to includenot only vapor extraction but also contaminated groundwater extraction.

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In addition, the thermal oxidizer that was on site during the early phases of the project, is no longeroperating because exhaust emissions continue to be below de minimus levels. Treated water obtained inassociation with the free product removal is discharged to the IWTP. All other equipment on site appears tobe secure and compliant with all codes and laws.

Pit Q-51 The location of former Pit Q-51 was visited to observe the condition of the concrete cap on April 9, 2003.Equipment and materials were staged on top of the patch, but the surface was sufficiently visible todetermine the condition of the concrete. The concrete patch was intact and all the seals around the jointswere in good condition and no separation or deterioration was evident.

Data Review

Building 3001 Groundwater The performance and effectiveness of the groundwater extraction and treatmentsystem was reviewed. Based on the site inspections and data review, the GWTP was found to be in goodoperating order, well maintained, staffed with competent operating personnel, and supervised by aknowledgeable and informed base staff. According to records reviewed, the system has consistentlyperformed at or above required operating levels and was found to meet effluent requirements withoutexception. Beginning in 1998, groundwater extracted at the Southwest Tank Area was being pumped to theGWTP.

The system has operated continuously with the exception of down-time associated with the connection ofnew extraction wells installed for other systems in the area as well as problems with an acid tank leak andstripper overload causing de minimus problems with air emissions. All represent temporary shutdowns andall were reported as required to the appropriate regulatory agencies.

The subsurface underlying Building 3001 site has been divided into 5 discrete hydrostratigraphic units.Figure 5 illustrates these in descending order, these units include: the upper saturated zone (USZ), the uppershale, the LSZ, the lower shale, and the production zone (PZ).

Only the USZ (formerly known as the “Perched” aquifer) and the LSZ (formerly divided and referred toindividually as the “Top of Regional” and “Regional” aquifers) portions of the aquifer system underlyingTinker AFB were evaluated. The deeper “Producing Zone” is not part of the ROD for the Building 3001 OUand was not evaluated.

Well measurements obtained in June 2002 were used to evaluate the effectiveness of the recovery wells atkeeping the plume from migrating. However, based on results of the temporary system shutdown, furtherinformation will be gathered as to the validity of these results. Ambient hydrogeologic conditions will likelyindicate that the plume is in equilibrium naturally and that there is a strong possibility that the extractionsystem could be detrimentally mobilizing the contaminant.

Free-phase dense non-aqueous phase liquid (DNAPL) TCE has not been identified at the Building 3001 site,but it is likely that it is present. According to the EPAs Dense Nonaqueous Phase Liquids WorkshopSummary (EPA, 1992). “groundwater concentrations of 1% or less of effective solubility can be found evenin the immediate proximity of the DNAPL.” The effective solubility of TCE is 1,000 mg/L, andconcentrations greater than 10 mg/L might indicate the presence of DNAPL Concentrations of TCE in theUSZ are as high as 250,000 ppb (1-70B); therefore, DNAPL may be present. In addition, given that TCEconcentrations in layers 3 and 5 are as high as 20,000 mg/L, it is possible that the DNAPL has migrated tothese layers as well.

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Evaluation of USZ The USZ is a shallow, unconfined, water-table aquifer that is known to be perched in the vicinity ofBuilding 3001. The lower boundary of the USZ is the upper shale. The saturated thickness of the USZranges from 0 on the east where the upper shale subcrops along Soldier Creek, to 33 9 feet on the westwhere the depth of the upper shale reaches 50 feet. The mean thickness of the USZ is 15.1 feet.

Figure 6 shows the distribution of TCE in the USZ in June 2002. TCE concentrations ranged from less than1 ppb to a maximum of 120,000 ppb (well 1 -70B). The cleanup level for TCE is 5 ppb. Since 1994,concentrations have generally decreased at the eastern edges of the plume. and concentrations in the centerof the plume, in the vicinity of P-8 and P-9, have increased. The increase in concentration is considered tobe the result of mobilization of TCE to those extraction wells. It should also be noted that hydraulic capturemay not be established near P-12.

Figure 7 shows the distribution of chromium in the USZ in June 2002. Chromium concentrations rangedfrom less than 10 ppb to a maximum of 10,600 ppb (well P-17). Note that the cleanup level for chromium is50 ppb, while the MCL is 100 ppb. Since 1999, the concentrations of chromium have generally decreased atseveral locations across the site; particularly at well 1-6BR.

The water table map for the USZ (Figure 8) generated from water levels measured in June 2002 clearlyshows the depression of the water table by the Building 3001 extraction system immediately west of thebuilding. A trough beneath the north-central portion of Building 3001 coincides with the locations of thehorizontal wells and indicates that the water table in this area has also been lowered by the extraction wells.With the exception of P-18, the capture zones of the extraction wells located on the east side of the buildingare much less pronounced.

Evaluation of LSZ (Uppermost portion) The uppermost portion of the LSZ is unconfined under much of Building 3001. Between 1,000 and 1,500feet west of Building 3001, water levels intersect the aquitard resulting in confined or semi-confinedconditions in the uppermost LSZ to the west. The unsaturated zone also thins north of Building 3001. Aneast-west trending groundwater mound located north of Building 3001 is coincident with the discontinuityin the upper shale unit believed to exist at the I-76 well cluster location and a depression in the USZ watertable at the same location. Groundwater flow directions in this layer are generally to the west-southwest

The highest concentrations of TCE and chromium in the uppermost LSZ layer plume are observed in wellsTOR-3. These high concentrations may be due to the downward movement of DNAPL and/or a result of thedownward vertical gradient between each aquifer unit.

Figure 9 shows the distribution of TCE in the uppermost LSZ in June 2002. TCE concentrations rangedfrom less than 1 ppb to a maximum of 5,100 ppb (well TOR-3). The cleanup level for TCE is 5 ppb. Since1994, concentrations have substantially decreased, with the exception of TOR-3. Concentrations in thevicinity of TOR-3 have increased, likely as the result of mobilization of TCE to those extraction wells.

Figure 10 shows the distribution of chromium in June 2002. Chromium concentrations ranged from lessthan 1 ppb to a maximum of 726 (well TOR-3). Note that the cleanup level for chromium is 50 ppb, whilethe MCL is 100 ppb. Since 1994, the chromium plume has been reduced in both size and concentration, andis essentially limited to the area around well TOR-3.

The water level map for the LSZ (Figure 11) shows the capture zone is well developed across this layer. Allof the TCE, except possibly in the vicinity of well M-2AR, is enclosed by the capture zone. The chromiumplume is completely captured by the recovery system.

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Evaluation of LSZ (Middle Portion) The middle portion of the LSZ lies below the uppermost portion (discussed above) and acts as a confinedaquifer. Groundwater flow in this layer is primarily to the southwest, except northeast and west of Building3001. There is a local groundwater divide located northeast of Building 3001. The groundwater dividetrends northwest-southeast between TOB-2 and the northeast corner of the IWTP. Northeast of the divide,groundwater flow is to the northeast. The southwesterly flow pattern is also interrupted by the capture zoneof the extraction wells located just west of Building 3001.

Figure 12 shows the distribution of TCE in the middle portion of the LSZ in June 2002. TCE concentrationsranged from less than 1 ppb to a maximum of 5,100 ppb (well TOR-3). The source of TCE in this area hasnot been determined. The TCE concentrations have decreased substantially since 1994, however, since 1999the levels have remained fairly constant. This may be an indication that the extraction system is no longerfunctioning optimally for this portion of the LSZ

Figure 13 shows the distribution of chromium in this part of the LSZ in June 2002. Chromiumconcentrations ranged from less than 1 ppb to a maximum of 4,910 ppb (well 34B). Note that the cleanuplevel for chromium is 50 ppb, while the MCL is 100 ppb. Since 1994, concentrations of chromium at well34B have substantially decreased.

The water level map for June 2001 (Figure 14) indicates a long, deep capture zone is well developed acrossLSZ (middle portion). The capture zone encompasses both the TCE and chromium plumes associated withBuilding 3001. However, the TCE and chromium detected under the runways west of Building 3001appears to be outside of the capture zone

Evaluation of LSZ (Lower Portion) Groundwater in the lower portion of the LSZ is confined or semi-confined by the overlying shale lensescomprising the units above. In addition, the hydraulic heads are generally less than 5 feet lower than in theoverlying layer. The general flow direction in this unit is to the southwest but is interrupted by the capturezone of the extraction wells just west of Building 3001.

Figure 15 shows the distribution of TCE in the lower LSZ in June 2002. TCE concentrations ranged fromless than 1 ppb to a maximum of 4,100 ppb (well 1-SA). The cleanup level for TCE is 5 ppb. Since 1994contaminant concentrations measured in the extraction wells have decreased indicating that the extractionsystem in this layer is no longer functioning optimally.

Figure 16 shows the distribution of chromium in this layer in June 2002. Chromium concentrations rangedfrom less than 1 ppb to a maximum of 285 ppb (well 1-60CR). Note that the cleanup level for chromium is50 ppb, while the MCL is 100 ppb. Since 1994 the chromium plume associated with Building 3001 has beengreatly reduced.

The water level map for June 2001 (Figure 17) indicates a capture zone is well developed across the layer.Both the TCE and chromium plumes are completely enclosed by the capture zone with the exception of 19ppb TCE and 12.8 ppb chromium in well M-3CR and 65 ppb of TCE in well M-ZC.

North Tank Area

Documents from the administrative record were reviewed in order to assess the progress and actions takenat the NTA.

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Source Removal Tank 3404 was abandoned in place between April and June 1992. Approximately 3,500 gallons of productwere removed from the tank during the abandonment. After the roof of the tank and appurtenances wereremoved, debris was removed from the floor of the tank, and concrete was poured into the base of the tank.Clean soil was used to backfill the tank to near surface and a concrete cover was placed over the soil atslightly below grade. Additional fill was placed over the concrete and the area planted with Bermuda grass.

Free Product Removal Free product removal began on May 26, 1991. Recovery of floating fuel has been accomplished by anumber of methods, including bailing, product-only pumping, dual fluid, and total fluids (product andwater) pumping. In addition, pneumatic fracturing of the aquifer was performed in 1993 to enhance productrecovery. Between May 1991 and December 1994, approximately 6,400 gallons of free product wereremoved from the aquifer as a result of well pumping and hand bailing. The ROD specified dual-fluidmethods of product recovery was discontinued at the end of 1994 due to excessive water production. Totalfluids recovery was discontinued for the same reason. Additional recovery wells were installed and furtherpneumatic fracturing performed on the aquifer in January 1995. Product-only pumping was re-initiated inFebruary 1995. Hand bailing at selected wells was also re-established on a weekly basis in October 1996.

Overall, the total volume removed is estimated at 23,605 gallons between July 1991 and February 2001 atthe NTA. Based on estimates from a pilot study using surfactant flushing between February 2001 and May2001, another estimated 6,400 gallons of product were removed bringing the cumulative removed &eeproduct to approximately 30,000 gallons by May 2001. Exact data for May 2001 through December 2002 isnot available at this time, but it is estimated that the VEP system has been making about a 9 gallon cut ofproduct per day for the last year and one half (-5000 additional gallons).

Results of focused RIs (Parsons ES and Battelle, 1994) indicate that the majority of the fuel is not floatingon the unconfined aquifer. The product is trapped in a lower confined unit, because the bottom of the tankthat leaked was below a confining clay layer

Though the free product continues to be a source of contamination to the groundwater, the dissolved fuelcompounds in both the unconfined and the confined shallow aquifer are, and will be, contained and/orcaptured by the vacuum enhanced pumping system. In addition, dissolved fuel residuals in the NTA will besubject to continuing natural biodegradation processes, which will limit migration from the NTA.

Vapor Extraction Implementation of a soil vapor-extraction remedy was tested in three separate efforts beginning in 1990.The Advance Final Design Analysis (Triax 1990), indicated that the soil permeabilities were less thananticipated during the original design, that the radius of influence for soil vapor extraction wells would beno more than 20 feet, and that an extensive network of horizontal well screens would be required along withthe blower(s) operating at a high output level.

In 1993, the New Jersey Institute of Technology performed pneumatic fracture injections in the vadose zoneof the NTA. Results indicated that the vadose zone permeability was improved, but the information from thetest as to the overall application of fracture injection to remediating the vadose zone soils contaminationwas inconclusive.

Based on results of the focused RI (Parsons ES and Battelle, 1994), remediation through natural attenuationwas recommended. This no-action alternative was recommended because time is not a critical factor due tolong-term monitoring for the Building 3001 groundwater plume. The shallow soils are considered

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sufficiently impermeable so that soil vapor exposure to potential receptors at the surface will not occur.There are also institutional controls in place to prevent unprotected workers from digging in the NTA.

Pit Q-51 Other than ARARs, no data were evaluated for Pit Q-51

SECTION 7 TECHNICAL ASSESSMENT

Building 3001 Question A: Is the remedy functioning as intended by the decision documents?: Although the system isinstalled and operated in accordance with the ROD, attainment of MCLs for TCE is unrealistic. VOC massremoval rates from groundwater have varied during the operation of the extraction system through February2000, but have not yet reached asymptotic levels. The system has removed approximately 15 drums (about8,625 pounds) of VOCs, including CAHs, from the onset of the system operation in June 1994. Therecovered contaminants consist mainly of TCE (about 75 %) with the remainder consisting of benzene,toluene, PCE and 1,2-DCE. These statistics represent recovery from the entire extraction system includingthe USZ and LSZ. Optimistically speaking, if current VOC removal rates are sustained, approximately52,000 pounds of total VOCs could be removed by the year 2024. Based on current operating costs, the totalcost for system expenditures would be projected to be $25.9 million in the year 2024. In reality, theprojected removal rates will drop substantially over time thus increasing projected operating costs for asystem that will never achieve current clean up goals.

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectivesused at the time of remedy selection still valid? Although the desired clean up levels have not changed,since the time of the ROD, it has been established that pump and treat will not be successful in achievingclean up levels outlined in the ROD. Therefore, those clean up goals outlined in the ROD are no longervalid. Because there is very little data that was acquired prior to system start-up, an Explanation ofSignificant Differences (ESD) has been submitted to the EPA in April 2002 requesting that the extractionfield be shut down for a period of at least a year in order to obtain site-specific ambient (pre-systemstart-up) geochemical and hydrogeologic data. In addition, plume studies will be performed in order todetermine if the plume would be in a steady-state equilibrium without the influence of the pump and treatsystem. During the shutdown, it is proposed that the plume be monitored to ensure protectiveness of humanhealth and the environment. All of the data acquired will be used to support a TI waiver. Regulatoryapproval for the ESD was received in May 2003.

Question C: Has any other information come to light that could call into question the protectiveness of theremedy? Not at this time.

North Tank AreaQuestion A: Is the remedy functioning as intended by the decision documents?: Yes, the remedy required bythe decision document was to remove free product and to address vapor in the vadose zone. As an additionto the ROD requirement, a dual phase extraction system has been installed to address not only thecontaminated soils, but also contaminated groundwater. This upgrade not only satisfies the RODrequirement, but also goes a step further towards site remediation.

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectivesused at the time of remedy selection still valid? There have been no changes since the previous five-yearreview.

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Question C: Has any other information come to light that. could call into question the protectiveness of theremedy? Not at this time.

SECTION 8 ISSUES FROM PREVIOUS REVIEW

The remedies specified in the ROD were implemented to the extent possible. Deviations from the selectedremedies are supported by the results of site-specific investigations and tests conducted prior to andsubsequent to the ROD, which were previously summarized. In particular, comments were made by EPAregarding the installation of a VEP system as opposed to an SVE system. The ROD only references a “vaporextraction system”, therefore, a VEP system complies with the ROD requirement.

Included in the previous Five-Year Review were questions posed by the EPA (in italics) followed byresponses from Tinker EM. These are as follows:

Building 3001 Groundwater The previous Five-Year Review recommended that the extraction rate at well P-1 should be increased toensure efficient recovery of contaminants near well 1-75B. As a result of this recommendation, the pumpingrate was increased in well P-1 to just below its cycle rate.

The previous review also recommended an additional USZ well be placed southwest of P-12 toconfirm/deny the presence of TCE beyond the P-12 capture zone. Well 2-428B was placed southwest ofP-12. June 2000 sample results indicated a TCE concentration of 7.4 ppb.

The source of contamination at wells 1-65B and 1-67B should be identified. The source of contamination atwell has yet to be determined. Keep in mind however that the contamination concentration in well 1-65B isfairly low at 7.5 ppb (as of June 2000 sampling). Well 1-67B is located in CG039 and the source is beingaddressed in an RFI being completed for that area The TCE concentration for this well is only 1.4 ppb.

Identify the source of contamination at well 1-72B. This well is also located in CG039 and the source isbeing addressed in an RFI being completed for that area.

Additional investigations should be conducted west of the north-south runway in layers 1 through 7 todetermine the horizontal and vertical extent of contamination. Following delineation, recommendations forremediation should he completed and an alternative selected and implemented. Additional monitor wellshave been placed in the USZ and LSZ and are sampled and analyzed annually through the basewidesampling program.

It is recommended that the RAOs for this site be reassessed based on changes in MCLs and the likelihoodthat DNAPL exists. We are currently in the process of performing a TI Waiver for this site and the RAOswill be re-evaluated during this project. The review of RAOs will focus more on the TCE contaminationrather than total aquifer restoration and will also consider the. feasibility benefit and risk associated withnatural attenuation of TCE.

North Tank Area A VEP system is planned for NTA. It is recommended that a complete O&M plan (with monitoringrequirements) be completed with this new system. The VEP system was activated in 99 and remainsoperational at the site. A Remedial Action Plan (RAP) was submitted to the Oklahoma Corporation

25

Commission (OCC) in accordance to their rules and regulations. The OCC issued a closure letter for thesite. The O&M Plan, although programmed, was never completed. The site was put under contract forQuarterly Monitoring through 2001 and is currently under contract for semi-annual monitoring.

Pit Q-51 Annual inspection of the concrete cap is recommended to ensure that the cap integrity is maintained. Theconcrete cap is part of the floor of Building 3001, the integrity of which is addressed as a maintenancefunction of 3001. Therefore, the Pit Q-51 Cap is maintained on a regular basis

Status of any other prior issues Not applicable.

SECTION 9 CONCLUSIONS

Building 3001 Groundwater The O&M records of the GWTP were reviewed and found to meet effluent requirements without exception.Overall, the extraction system appears to effectively control the TCE and chromium groundwater plumes;however, there are areas of the site with isolated occurrences of TCE and chromium that do not appear to berelated to Building 3001.

The ROD predicted that the GWTP extraction system would remove approximately 72 percent of the TCEand 77 percent of the chromium in the first five years of operation and that 85 percent of both contaminantswould be removed within 20 years. It is important to note that these estimates did not take intoconsideration the addition of contaminants into the flow system as a result of recharge through sourcezones, the effects of retardation (sorption, desorption, chemical reactions), the likely presence of DNAPL ortravel time to the extraction wells. Incorporation of these factors would have resulted in a more realisticestimation of cleanup times.

In general the highest concentrations of TCE and chromium have declined beneath Building 3001.Concentrations in some of the monitoring wells have risen and fallen erratically since full scale monitoringof this OU was initiated in 1994. However, the June 2002 contaminant concentration data and water leveldata indicate that the extraction wells are capturing the contaminants associated with Building 3001.

North Tank Area Free product at the site is relatively immobile. Although the free product remainsthroughout the NTA, product thickness within the formation has significantly decreased within the last 12months. Multiple pilot testing using SVE and pneumatic fracturing has determined that formationpermeability is very low and soil contamination is not very conducive to contaminant removal using thesetechnologies. Natural attenuation is an appropriate remedial action based on cost and on the presumptionthat time is not a factor due to the anticipated long-term remediation and monitoring for the Bldg 3001groundwater plume

As long as the fuel product remains relatively immobile, the O&M activities currently performed at the siteare protective of human health and the environment. Sufficient monitoring and institutional controls are inplace to determine if product is migrating form the NTA.

Pit Q-51 Pit 0-5 1 has been effectively remediated with removal of the pit contents and sealing with an8-inch thick concrete cap. The site inspection confirmed that the cap is intact.

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SECTION 10 RECOMMENDATIONS

Building 3001 Groundwater It is recommended that pre-pump and treat system conditions be established so that ambient data can beobtained. This will only be achieved by shutting down the extraction well field. Additionally, obtaining datanecessary to support a TI waiver is an important step in establishing the fact that the ROD requirements willnever be achieved. Because this plume rests underneath a large industrial facility and because sourcelocations under the building cannot be determined, the plume cannot be remediated given currenttechnologies. Long term monitoring is recommended to prove that the plume is in equilibrium and is notmigrating and will therefore be protective of human health and the environment.

North Tank Area The conclusion in the Focused RI (Parsons ES and Battelle, 1994) is that natural attenuation is appropriatebased on cost and on the presumption that time is not a factor due to the anticipated long-term remediationand monitoring of the Building 3001 groundwater plume. A vacuum enhanced pumping (VEP) technologydemonstration is in place for the NTA Existing wells are screened across the vadose, unconfined, andconfined portions of the USZ. Fluids are removed from the subsurface using a vacuum pump and treatedon-site with air stripping and thermal oxidation if necessary.

It is recommended that free-product removal continue until such time as the effectiveness and efficiency ofthe VEP system can be weighed against the benefits of alternative remediation such as Monitored NaturalAttenuation. If shown feasible, monitored natural attenuation should be pursued. Using this technology willstill maintain protectiveness of human health and the environment.

Pit Q-51 Annual inspection of the concrete cap is recommended to ensure that the cap integrity is maintained.

SECTION 11 NEXT REVIEW

The U.S. Air Force will conduct the next five-year review in 2008, fifteen years after implementation of thegroundwater remedy at the Building 3001 OU.

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APPENDIX ALIST OF DOCUMENTS REVIEWED

ATSDR, 1995. Public Health Assessment Addendum, Tinker Air Force Base (Soldier Creek/Building 3001),Midwest City, Oklahoma County, Oklahoma (addendum to Health Assessment, May 20, 1988). U.S.Department of Health and Human Services, Public Health Service, Agency for Toxic Substances andDisease Registry. February 27, 1995.

B&V, 1991. Technical Memorandum Groundwater Modeling and Extraction System DesignConsiderations, Draft Revised Final Report. Prepared for U.S. Army Corps of Engineers, TulsaDistrict. Black & Veatch Waste Science and Technology Corporation. November 1991.

B&V, 1992a. Overall Design Concept Summary for the Building 3001 Groundwater Remedial Action,Revised Final Report. Prepared for the U.S. Army Corps of Engineers. Black k. Veatch WasteScience and Technology Corporation. February 1992.

B&V, 1992b. Operation and Maintenance Manual, Building 3001 Groundwater Treatment System,Volumes I & II, Draft Final. Prepared for U.S. Army Corps of Engineers, Tulsa District. Black &Veatch Waste Science and technology Corporation. December 1992.

Battelle, 1993 a. North Tank Area Data Summary and Soil Remediation Alternatives Report for Tinker AFB,Oklahoma. Battelle Memorial Institute, Columbus, Ohio. February, 1993.

Battelle, 1 993b. In-Situ Respiration and Air Permeability Test Report for Tinker Air Force BaseBioremediation Demonstration, North Tank Area (NTA) Site, Final. Prepared for U S. Air Force,Tinker Air Force Base, Environmental Management Directorate, Oklahoma City, Oklahoma underContract DE-ACO6-76RLO 1830. Battelle Columbus Operations for Environmental ManagementOperations under a Related Services Agreement with the U.S. Department of Energy. February1993.

Battelle, 1995a. Groundwater Flow and Solute Transport Modeling, Draft Report, Battelle MemorialInstitute, Columbus, Ohio, December 1995.

Dansby & Associates, Inc., 1986. Report of the Plugging Procedures Water Wells 18 and 19. Tinker AirForce Base. Contract F34650-85-C-0404. 1986 Dynamic Graphics, Inc. 1996. EarthVision, Version3.0.

Engineering Enterprises, Inc., 1984. Investigation of Water Wells 18 and 19. Tinker Air Force Base. August1984.

EPA, 1988. Federal Facilities Agreement under CERCLA Section 120, in the Matter of the U.S. Departmentof the Air Force and Tinker Air Force Base, Oklahoma. U.S. Environmental Protection Agency.Administrative Document Number NPL-U3-2-27. December 9, 1988.

ES, 1982. Installation Restoration Program Phase I: Records Search. Prepared for Tinker Air Force Base,Oklahoma. Engineering-Science, Inc. April 1982.

OC-ALC, 199la. Decision Document for Pit Q-51. Oklahoma City Air Logistics Center, OC-ALC/EMR.June 1991.

OC-ALC, 1991b. Closeout Document for Pit Q-51. Oklahoma City Air Logistics Center. June 199128

Parsons ES & Battelle, 1994. North Tank Area Focused Remedial Investigation Report. Prepared forOklahoma City Air Logistics Center, Tinker Air Force Base, Oklahoma. Parsons EngineeringScience, Inc. and Battelle. December 1994

Parsons ES, 1995. North Tank Area Treatability Investigation Special Case Investigation Report, Tinker AirForce Base, OK, Parsons Engineering Science, Inc. St Louis MO, June 1995.

Parsons ES, 1996b. Optimization Report for the Groundwater Treatment Plant Extraction System. Preparedfor Department of the Air Force, Oklahoma City Air Logistics Center, OC-ALC/EMR. ParsonsEngineering Science. September 1996.

Parsons ES, 1996c. Evaluation of In Situ Sensor Utilization and Long-Term Monitoring Protocols for theNorth Tank Area, Tinker AFB, Oklahoma, Operation and Maintenance Plan. Parsons EngineeringScience 1996.

Parsons ES, 1998a. Groundwater Treatment Plant Extraction System Assessment. Prepared for Departmentof the Air Force, Oklahoma City Air Logistics Center, OC-ALC/EMR. Parsons EngineeringScience. April 1998.

Parsons ES, 1998b. Remedial Investigation Report, Tinker Air Force Base Industrial Wastewater TreatmentPlant/Soldier Creek Off-Base Groundwater Operable Units, Volumes I -III, Final. Prepared forDepartment of the Air Force, Oklahoma City Air Logistics Center, OC-ALC/EMR. ParsonsEngineering Science. July 1998.

Radian, 1985a. Installation Restoration Program, Phase II Confirmation/Quantification Stage 1, FinalReport. Radian Corporation. September 1985.

Roy F. Weston, 1992. Final Report for the Installation of Recovery Wells and Recovery CompoundConstruction for the North Tank Area, Final Report. Roy F. Weston, Inc. October 1992.

Tinker AFB, 1994. Hydrogeologic Conceptual Model for Tinker Air Force. Tinker AFB, 1994.

USACE, 1988a. Building 3001 Remedial Investigation Report, Tinker Air Force Base InstallationRestoration Program, Final. U.S. Army Corps of Engineers, Tulsa District. January 1988.

USACE, 1989a. Building 3001 Supplemental Quarterly Remedial Investigations, Draft Report. U S. ArmyCorps of Engineers, Tulsa District. August 1989.

USACE, 1989b. Building 3001 Feasibility Study Report. U.S. Army Corps of Engineers, Tulsa District.August 1989.

USACE, 1990a. North Tank Area (NPL Site) Operable Unit to B 3001, Design Summary Report, Tinker AirForce Base, Oklahoma City, Oklahoma. Installation Restoration Program, Project No. WWYK880349B U.S. Army Corps of Engineers, Tulsa District. March 1990.

USACE, 1990b. Building 3001 (NPL Site) Record of Decision .Tinker Air Force Base, Oklahoma, Final. Installation Restoration Program, Project No. WWYK86-3 11. U.S. Army Corps of Engineers, TulsaDistrict. August 1990.

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APPENDIX B

1. Site inspection checklist for Soldier Creek Surface Water and Sediment. 2. Site inspection checklist for Building 3001 OU.

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Five-Year Review Report for The Soldier Creek Sediment and Surface Water Operable Unit 2

Submitted to:

United States Environmental Protection AgencyRegion VI

Prepared by: Sara Sayler

OC-ALC/EMPE 7701 Arnold Street, Ste. 204 Tinker AFB, OK 73145-9100

Phone: 405/734-45SO Email: Sara.Sayler@tinker.af.mil

February 2003

SIGNATURE PAGE

TABLE OF CONTENTS

SECTION 1 INTRODUCTION 1SECTION 2 BACKGROUND 1

Site Description 1Land and Resource Use 3

Surrounding Community 3Human Use of Resources 5

Contaminants 5Initial Response 6

SECTION 3 REMEDIAL ACTIONS 7Remedy Selection and Implementation 7Operation and Maintenance Requirements 9Remedial Action Objectives 9Human Health Risk Assessment 9Comparison of Data to Health-Based Cleanup Goals 11Ecological Risk Assessment 12Additional Remedial Actions 14

SECTION 4 PROGRESS SINCE LAST FIVE-YEAR REVIEW 14Protectiveness Statement from ROD 14Protectiveness Statement from Last Five-Year Review 14Status of Recommendations from Last Review 14

SECTION 5 FIVE-YEAR REVIEW PROCESS 15Site Inspection 15

Interviews 15Site Visit 15

Community Involvement 15Data Review 15

Seventh Year Long Term Monitoring Annual Report Surface Water 16Sediment 16

Eighth Year, First Event Sampling Report 17

SECTION 6 TECHNICAL ASSESSMENT 18

SECTION 7 ISSUES FROM PREVIOUS REVIEW 19

SECTION 8 CONCLUSIONS 19Interpretation of Human Health Significance 19Interpretation of Ecological Significance 19

SECTION 9 DEFICIENCIES 21

SECTION 10 RECOMMENDATIONS 21

SECTION 11 NEXT REVIEW 21

LIST OF FIGURES

No. Title Page

1 Tinker AFB and Vicinity Map 2 Site Location Map 3 Soldier Creek Quarterly Monitoring Sampling Locations

LIST OF TABLES

No. Title

1 Chronology of Activities for SCSSW OU 102 Summary of Remedy Development and Implementation Activities 13

at SCSSW OU 3 Long Term Monitoring Maximum Analyte Concentrations in Surface Water App. A4 Long Term Monitoring Maximum Analyte Concentrations in Sediment App. A5 Sediment Sample Results Greater than BHRA 10-6 Screening Criteria App. A6 Sediment Sample Results Greater than HHRA 10-6 Screening Criteria App. A

LIST OF APPENDICES

APPENDIX A Data Tables APPENDIX B List of Documents Reviewed APPENDIX C Photos

ACRONYMS AND ABBREVIATIONS

AFB Air Force BaseARAR Applicable or relevant and appropriate requirementATSDR Agency for Toxic Substances and Disease RegistryBattelle Battelle Memorial InstituteBHRA Baseline human health risk assessmentBTEX Benzene, toluene, ethylbenzene, and xylenesB&V Black & Veatch Waste Science and Technology CorporationCERCLA Comprehensive Environmental Response, Compensation, and Liability ActCOPC Chemical of potential concernCr ChromiumCWA Clean Water ActDCE DichloroetheneDNAPL Dense non-aqueous phase liquidEPA U.S. Environmental Protection AgencyERA Ecological risk assessmentFFA Federal facilities agreementGWTP Groundwater treatment plantHHRA Human health risk assessmentHHRA I Human health risk assessment (first annual)HHRA II Human health risk assessment (second annual)HHRA III Human health risk assessment (third annual)HI Hazard indexIRP Installation Restoration ProgramIWTP Industrial wastewater treatment plantLSZ Lower saturated zoneMCL Maximum Contaminant Levelmg/Kg Milligrams per kilogrammg/L Milligrams per literNPDES National Pollutant Discharge Elimination SystemNPL National Priority ListOAC Oklahoma Administrative CodeOC-ALC Oklahoma City Air Logistics CenterOC-ALC/EMPE Oklahoma City Air Logistics Center/Environmental Management Program

EngineeringOCC Oklahoma Corporation CommissionODEQ Oklahoma Department of Environmental QualityO&M Operation and MaintenanceOSDH Oklahoma State Department of HealthOU Operable UnitPAH Polycyclic Aromatic HydrocarbonParsons ES Parsons Engineering Science, Inc.PCB Polychlorinated biphenyl PCE Tetrachloroethene (Perchloroethene)ppb Parts per billionPOL Petroleum oil lubricantsppm Parts per millionPRP Potentially responsible party

RA Risk assessmentRAO Remedial action objectiveRCRA Resource Conservation and Recovery ActRGO Remedial goal optionRI Remedial investigationRME Reasonable maximum exposureROD Record of DecisionSCSSW Soldier Creek sediment and surface waterSCOBGW Soldier Creek off-base groundwaterSDWA Safe Drinking Water ActSF Slope factorSVOC Semivolatile organic compoundTBC To-be-consideredTCE TrichloroetheneTPH Total petroleum hydrocarbonTTNUS Tetra Tech NUS, Inc.µg/L Micrograms per literUSACE United States Army Corps of EngineersUSZ Upper saturated zoneVOC Volatile organic compoundWCFS Woodward-Clyde Federal Services

Executive SummaryThe ROD, signed in August 1993 provided for a limited action remedy for the Soldier Creek Sediment andSurface Water Operable Unit 2. The remedial actions selected in the ROD incorporate the following: l) afive-year monitoring program of the Soldier Creek sediment and surface water at on-base and off-baselocations to determine if contaminant migration has occurred and, if so, determine if migration has resultedin contaminant concentrations greater than health based cleanup goals, 2) an ecological investigation ofSoldier Creek sediment and surface water to further define potential environmental risk, 3) annualmonitoring reports to present and evaluate monitoring results for levels exceeding health-based cleanupgoals and, finally 4) a five-year ROD review to ensure that the remedy continues to provide adequateprotection of human health and the environment or whether additional remedial actions are necessary. Thetrigger for this second five-year review was the first five year review which was completed in 1998 andgained regulatory acceptance in October 2002.

The assessment of this review indicates that there is no longer danger posed to human health and theenvironmen1. Numerous remedial activities not required by the ROD have occurred in the area that serve toremove or reduce potential contaminant sources. In addition, results of the human health risk assessmentsindicate no unacceptable risk to human health. Because there have been no exceedences of health basedscreening levels (based on 10 ) in the sampling over the past five years, it is recommended that sampling bediscontinued and the site be considered closed in accordance with the ROD After gaining regulatoryacceptance of this Five-Year Review, Tinker AFB will request de-listing of the OU.

SECTION 1 INTRODUCTION

The U.S. Air Force has conducted a five-year review of the remedial action implemented at theSoldier Creek site at Tinker Air Force Base in Oklahoma (Figure 1) The primary purpose of the review is todetermine whether the remedy remains protective of human health and the environment. Five-year reviewreports identify deficiencies, if any, and recommendations to address them. Five-year review reportsdocument the evaluation of the implementation of the remedy and operation and maintenance (O&M), aswell as the continued appropriateness of remedial action objectives (RAOs), including cleanup levels at asite This is the second five-year review for the Soldier Creek site. The previous Five-Year Review,submitted September 1998, gained regulatory approval through a letter from the USEPA dated 10/22/2002.

This review is required by statute. Section 121©) of the Comprehensive Environmental Response,Compensation, and Liability Act of 1980 (CERCLA), as amended by the Superfund Amendments andReauthorization Act of 1986 (SARA), and Section 300.430(f)(4)(ii) of the National Oil and HazardousSubstance Pollution Contingency Plan (NCP), require that periodic (no less often than every five years)reviews be conducted for sites where hazardous substances, pollutants, or contaminants remain at the siteabove levels that allow for unlimited use and unrestricted exposure following the completion of all remedialactions.

Executive Order 12580 delegates the authority to conduct five-year reviews to the Departments ofDefense and Energy, where either the release is on, or the sole source of the release is from, any facilityunder the jurisdiction of those departments. In the Federal Facilities Agreement signed on December 9,1988 between the U.S. Air Force, EPA, and the Oklahoma State Department of Health (succeeded by theOklahoma Department of Environmental Quality in 1993), the U.S. Air Force was established as the leadagency for remediating the Soldier Creek Site.

SECTION 2 BACKGROUND

SITE DESCRIPTION

The main portion of Soldier Creek is to the east of Tinker AFB; however, two unnamed tributaries(East and West Soldier Creeks) originate on the Base. Soldier Creek flows to the north from its headwatersnear Southeast 59th Street to its confluence with Crutcho Creek approximately six miles downstream (Figure2). According to the Federal Facility Agreement (FFA) for the Base, the Soldier Creek Operable Unitincludes Soldier Creek, its tributaries, and any area underlying or adjacent to the waterway that may becontaminated by the migration of hazardous substances, pollutants, or contaminants from Tinker AFB.

The Soldier Creek Sediment and Surface Water (SCSSW) site, or Operable Unit 2 (OU-2), includesSoldier Creek, its tributaries, and any area underlying or adjacent to the waterway that may be contaminatedby the migration of hazardous substances or pollutants from Tinker AFB. The tributaries of Soldier Creekare unnamed, but are referred to as East and West Soldier Creeks in this report. As required in the SCSSWROD, a work plan was created for monitoring this OU and the boundaries of the OU were established in thework plan. As defined in the work plan (WCFS, 1994), these boundaries are as follows: 1) All sediment andsurface water of East Soldier Creek that originate on Tinker AFB to the intersection of East Soldier Creekand Interstate 40 north of Tinker AFB, and 2) All sediment and surface water of West Soldier Creek thatoriginate on Tinker AFB to the intersection of West Soldier Creek and Interstate 40 north of Tinker AFB.

1

The boundaries include the ditches leading from the eight NPDES outfalls to East and West SoldierCreeks, the lower portion of the stream defined as Tributary B in the RI/FS documents (just prior to itsconfluence with East Soldier Creek), and terrestrial habitats within the 100-year floodplain of theaforementioned stream segments (or within 50 feet from either bank of the stream where it is not located inthe 100-year floodplain). These boundaries supercede the boundaries originally established in the SoldierCreek RI (B&V, 1993b).

Environmentally sensitive areas within the Soldier Creek site include the Garber-Wellington aquiferand Soldier Creek as described above The closest Superfund site is the Mosley Road Landfill site locatedapproximately 6 miles north of Tinker AFB.

LAND AND RESOURCE USE

Prior to 1941, the site was located on undeveloped pasture and prairie lands. There were someagricultural activities and ranching but no known industrial uses prior to 1941. Beginning in 1941, 960 acresof land were donated to the Army Air Corps by the City of Oklahoma City for the construction of theMidwest Air Depot. Renamed Tinker Field in 1942 and subsequently Tinker Air Force Base in 1948, theentire base now covers 5,277 acres.

The on-base portion of the Soldier Creek site is in the northeast quadrant of Tinker AFB, which isthe most industrialized area of the base.

The off-base properties within the Soldier Creek site include the Kimsey Addition to the north, alongwith commercial/retail establishments and mobile homes to the east. The Kimsey Addition is a residentialarea consisting of approximately 100 homes bounded by Tinker AFB to the south and west, Interstate 40 tothe north, and Douglas Boulevard to the east. The commercial/retail facilities between Tinker AFB and EastSoldier Creek include convenience stores and self-storage units Other than the Evergreen Mobile HomePark, the remainder of the site east of Douglas Boulevard and northwest of East Soldier Creek isundeveloped between the mobile home park and Interstate 40.

Soldier Creek and its tributaries receive surface runoff from approximately 9,000 acres (14 squaremiles), at its confluence with Crutcho Creek. Areas of Tinker AFB that contribute runoff or discharge toSoldier Creek and its tributaries include the eastern-most runway areas and the Building 3001 complex.Prior to April 1996, the IWTP discharged treated water to East Soldier Creek. Recharge from East SoldierCreek to the aquifer occurs and remains within the boundaries of Tinker AFB.

Surrounding Community

The Soldier Creek site and Tinker AFB lie within an area representing transition from residentialand industrial/commercial land use on the north and west to agricultural land use to the east and south.Soldier Creek and its tributaries, which flow northwest through the area, are bordered by recreational andresidential areas with some areas supporting commercial and industrial land use. Some off-base industries,such as a metal plating facility and a dry cleaning facility, and commercial facilities such as gas stations,auto repair facilities, and a closed sanitary landfill are located within the drainage basin. In addition, threeschools, Soldier Creek Elementary, Steed Elementary, and Monroney Junior High are located within thedrainage basin. There are ten public parks within the general vicinity of Tinker AFB, including the Joe BBams, Fred F. Meyers, Kiwanis, and Lions Parks. A public golf course is also located north of the base.Five trailer parks are located north and northeast of Tinker AFB.

3

The land use plan for the area immediately north of Tinker AFB, between Sooner Road and DouglasBoulevard includes all levels of land use. The areas between Sooner Road and Midwest Boulevard (seeFigure 1 for location) are zoned primarily for housing (single and multifamily units) and low to mediumcommercial use. The area between Midwest Boulevard and Douglas Boulevard is zoned primarily for heavycommercial and moderate to heavy industrial use.

Soldier Creek, which flows from Tinker AFB into adjacent neighborhoods, is reportedly used forwading and playing by area children and is large enough to support edible fish. No hunting or fishing hasbeen reported to occur in the immediate area outside of Tinker AFB. Hunting is not permitted on base andfishing is not permitted in Soldier Creek within base boundaries. Beneficial uses of Soldier Creek includeagriculture, secondary recreation, process and cooling water, and aesthetics. Soldier Creek also supports awarm-water aquatic community.

Human Use of Resources

The most important source of potable groundwater in the Oklahoma City metropolitan area is theCentral Oklahoma aquifer, which is commonly referred to as the “Garber-Wellington aquifer.” Tinker AFBpresently obtains part of its water supplies from wells that are completed in the Garber-Wellington aquifer.Base wells range from 700 to 1,100 feet in total depth, with yields ranging from 205 to 250 gallons perminute (gpm).

On the east side of Tinker AFB, the Garber-Wellington aquifer has been classified as a Class IIAaquifer by the State of Oklahoma, indicating that it provides groundwater from a major, unconfined basinthat is capable of being used as a drinking water supply with little or no treatment (OAC 785:45-7-3). Thewestern portion of the Garber-Wellington aquifer basin, which extends from the west side of the base to justwest of Oklahoma County, is classified as a Class IIC aquifer, a major confined groundwater basin. TinkerAFB and the nearby communities of Midwest City and Del City derive a portion of their water supply fromthe Garber-Wellington aquifer.

Until 1993, groundwater was used as a domestic water source by several of the residents livingwithin and adjacent to the boundaries of the site. Most of these wells were removed from service in 1994after municipal water distribution lines were conveyed to and installed at the residences and businesses.There are no off-base wells adjacent to the northeast portion of the base that are known to be used fordrinking water purposes. All of the water supply wells on Tinker AFB are routinely sampled forcontaminants.

CONTAMINANTS

The Air Force Installation Restoration Program (IRP) Phase I identified potential sources of contaminationthrough records searches and reviews of waste management practices. The first report of a release to theenvironment occurred in 1983 during routine wellhead sampling and testing. Trichloroethene (TCE) andtetrachloroethene (PCE) were detected in two of the base water supply wells (WS 18 and WS 19) atBuilding 3001. A Phase II IRP investigation was conducted in 1984 to confirm and quantify contaminationresulting from past waste storage practices at Building 3001. Sampling was also initiated at East and WestSoldier Creek in 1984. Sample results indicated the presence of chromium and solvent contamination in thesediment and surface water. In September 1987, the Soldier Creek site was evaluated under the hazardranking system with a score of 42.24 and was placed on the NPL

5

The groundwater used by residents and the work force of Tinker AFB was identified as an exposurepathway. Potential points of exposure included water supply wells and discharge to surface water bodies.Exposure with long-term health effects was deemed a possibility in the 1988 baseline risk assessment. Achronology leading to the NPL listing is provided in Table 1.

Remedial investigations of the SCSSW OU were conducted between 1990 and 1991. Results of thesediment analyses indicated acetone, chloroform, methylene chloride, PCE, toluene, xylene, cadmium,chromium, and lead were the primary sediment contaminants. The primary surface water contaminants wereacetone, chloroform, methylene chloride, PCE, toluene, 1,1,1 trichloroethane, cadmium, chromium, andlead.

The surface water and sediment of Soldier Creek were considered as potential exposure pathwaysfor human receptors, but results of the 1993 risk assessment for these media indicated that there was not anunacceptable risk to human health.

Table 1 Activities Leading to NPL Listing for SCSSW OU

Investigation/Activity Description Event Date (Source)

Sediment and surfacewater sampling

Evaluate water quality effects of wastewaterdischarge from Tinker AFB on Soldier andCrutcho Creeks

October/November 1984(USEPA, 1984)

Sediment sampling Site investigation to evaluate magnitude ofcontamination in East and West Soldier Creeks

October 1985(HKS, 1985)

Sediment dredging Dredging of unknown volume of sediment fromon-base portions of East and West Soldier Creeks

April/May 1986(HKS, 1986)

NPDES surface watersampling

Determine surface water concentrationsdownstream of IWTP effluent discharge location

September 1986- July1987(Tinker AFB)

Sediment and surfacewater sampling

Sampling was performed to collect sediment andsurface water samples at the IWTP and sanitarywastewater treatment plant outfalls.

March-September 1987(Source: B&V, 1993b)

NPL listing Main stream of Soldier Creek and all tributaries ofSoldier Creek originating on Tinker AFB wereincluded in the NPL site

July 22, 1987

INITIAL RESPONSE

The U.S. Environmental Protection Agency (EPA), U.S. Air Force, and Oklahoma State Departmentof Health signed a Federal Facilities Agreement (FFA) designating the Air Force as the only PotentiallyResponsible Party (PRP). Response actions initiated prior to the ROD are discussed below.

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In 1986, excavation activities were conducted along East and West Soldier Creek to identify andeliminate potential sources of contamination to Soldier Creek. Approximately 7,500 cubic yards of sedimentwere removed. In 1990 and 1991, several industrial cross-connections were removed that may have beencontaminating the Soldier Creek storm-water system. Between 1990 and 1993, fourteen solvent pits andUSTs in the vicinity of Soldier Creek were removed or abandoned.

The SCSSW ROD was signed in September 1993. Contamination remains on-site, but there havebeen no unacceptable human health risks associated with the levels of contaminants detected. Numerouscontaminants, however, were found to present an unacceptable ecological risk These risks were based onconcentrations of site contaminants, which exceeded the lowest available ecotoxicological benchmark forthe exposure pathway. The adverse effects were limited to a localized scale in on-base areas.

SECTION 3 REMEDIAL ACTIONS

Remedy Selection and Implementation

The ROD, signed in August 1993 provided for a limited action remedy for the SCSSW OU. Theremedial action objectives for the OU were to prevent the ingestion of, or dermal contact with, sediment andsurface water with contaminant concentrations greater than health-based cleanup goals and to preventoff-base migration of contaminants with concentrations greater than health-based cleanup goals. Existing orpotential groundwater contamination was to be addressed separately under the Soldier Creek Off BaseGroundwater (SCOBGW) OU due to the complexity of potential groundwater interactions between all ofthe OUs at Tinker AFB The IWTP/SCOBGW investigations included evaluation of the interactions betweenthe creeks and groundwater.

The baseline risk assessment determined that the Soldier Creek sediment and surface water did notpose a risk to human health or the environment in excess of the acceptable risk-based levels established byEPA. However, the environmental assessment conducted as a part of the baseline risk assessment was onlyqualitative and could not be used to fully assess ecological risk. Long-term monitoring would be used todetermine if levels in the creek remain below the health-based cleanup goals over time and quantitativelyevaluate the environmental risk, if any, existing at the OU. The remedial actions selected in the RODincorporated the following components:

• A five-year monitoring program of Soldier Creek sediment and surface water at on-base andoff-base locations to determine if contaminant migration has occurred and, if so, determine ifmigration has resulted in contaminant concentrations greater than health-based cleanupgoals.

• An ecological investigation (quantitative and qualitative) of Soldier Creek sediment andsurface water to further define potential environmental risk.

• Annual monitoring reports to present and evaluate monitoring results for levels exceedinghealth-based cleanup goals

• A five-year ROD review to ensure that the remedy continues to provide adequate protectionof human health and the environment or whether additional remedial actions are necessary.

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A chronology of the remedy development and implementation activities for the SCSSW OU is provided inthe Table 2 below.

Table 2 Summary of Remedy Development and Implementation Activities at SCSSW OU

Investigation/Activity Description Date(and Source)

Quarterly groundwatersampling

Sample groundwater in area of East andWest Soldier Creeks, Building 3001, andIWTP.

December 1987-March 1989USACE, Tulsa District(Source: WCFS, 1998)

Final storm water Sample surface water to identifycontaminant investigation release fromBuilding 3001 storm sewers to East andWest Soldier Creeks

October 1989(NUS, 1989)

Phase I and Phase II RI/FS Determine extent of sediment and surfacewater contamination along East, Main,and West Soldier Creeks

Phase I-July 1990Phase II-June1991(B&V, 1993b)

HI-IRA and qualitative ERA Quantitative HHRA and qualitative ERAto establish potential current and futurerisk to on-base and off-base receptorsutilizing sediment, surface water, andgroundwater data

February 1993(B&V, 1993c)

ROD issued/signed Establish remedial action for the site Issued - August 1993Signed - September 14, 1993(B&V, 1993a)

Quantitative ERA II Quantitative ERA to determine potentialeffects of chemicals in surface water andsediment on biological environment -included biological survey to determinecharacteristics of species within on-baseand off-base portions of the OU(conducted as ROD requirement)

Vols. I, II, IIIWCFS, 1997

First – Seventh yearlong-term monitoring andannual reports

Quarterly monitoring of sediment andsurface water and yearly reporting topresent monitoring results and HHRA I(conducted as ROD requirement)

November 1994 throughOctober 2002

Remedial responses Numerous past and on-going remedialactions in the area to provideprotectiveness of the environment such assediment removal and cementing of creekbeds in 1999. (actions not identified as aROD requirement)

1990 – on-going

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Operation and Maintenance Requirements

There are no O&M requirements associated with the continued monitoring remedy. Flight linecriteria at Tinker AFB have prompted upgrades to the landscape along West Soldier Creek The channel ofWest Soldier Creek has also been concreted. This action serves as a facility improvement for Tinker’smission, as well as a remedial measure (although not identified as a ROD requirement) to minimize thepotential for sediments to move off base and pose a human health or ecological threat to downstreamreceptors.

Remedial Action Objectives

The selected remedial action goals for the SCSSW were based on results of the baseline riskassessment (RA) conducted for the OU (B&V, 1993c), which included a quantitative baseline human healthrisk assessment (BHRA), and a qualitative ecological risk assessment (ERA). Results of the BHRA showedthat potential risk to human health from Soldier Creek sediment and surface water was within acceptablerisk-based exposure levels established by the EPA. The qualitative ERA identified several contaminants thatmay pose a potential environmental concern, however, additional study was recommended to fullycharacterize potential risk.

The health-based cleanup goals were identified in the ROD as to-be-considered (TBC) criteria to beused as guidelines for evaluating future concentrations of contaminants detected in Soldier Creek sedimentand surface water. TBCs are evaluated in the five-year review with respect to any changes since the time oftheir development. TBCs can vary due to changes in site characteristics (e.g., receptors, exposures, orpathways) and/or characteristics of the contaminant (e.g., new toxicity information and level ofcontaminant). The TBCs were initially based on the existing site conditions and contaminant characteristicscomputed by back-calculating equations used in the BHRA (B&V, 1993b; 1993c).

The ROD response action was based on sediment and surface water data collected during Phase Iand Phase II of the RI For these media, the BHRA evaluated potential risks for incidental ingestion anddermal contact for adult workers and child/adult recreators Based on the conceptual site model (CSM),which identifies and describes exposure pathways, which may be potentially complete for the site, tenreasonable maximum exposure (RME) scenarios were selected to represent the current and future land use.The exposure pathways and RME assumptions initially evaluated in the BHRA are considered to beapplicable to current conditions.

The qualitative ERA focused on the effects of contaminant exposure on general populations ofaquatic and terrestrial species typical of the OU area (B&V, 1993 c). It was found that the presence ofseveral metals in surface water and sediment (barium, cadmium, chromium, copper lead, nickel, selenium,silver, and zinc) were of potential environmental concern to aquatic species; however, additional data wereneeded to fully characterize this risk as well as the potential risk to terrestrial species.

Human Health Risk Assessment

The first annual human health risk assessment (HHRA I) was prepared to provide information onpotential “current” and future risks based on data for surface water and sediment samples collected inNovember 1994, and January, April, and June 1995. The stream segments that were sampled are shown onFigure 3. The data were also used to compare results with those of the RI (B&V, 1 993b) and determine ifprevious conclusions remained valid. Based on results of the second year of quarterly monitoring, the

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second annual HHRA (HHRA II) was prepared to address the same issues as the HHRA I. “Current” datafor HHRA II (collected in October 1995, and March, May, and August 1996) were used to identify potentialrisk and also verify that previous conclusions remained valid. These issues were similarly addressed in thethird annual HHRA (HHRA III) using monitoring results from samples collected in January and July 1997.

Although not impacting the overall results, slight differences in methodology are noted between theoriginal BHRA and the long-term HHRAs:

• PCB/pesticide analyses were added as sampling criteria in the long-term monitoring study(these analytes were not included in the RI samples);

• Four stream segments were evaluated for risk in the long-term HHRAs (nine segments wereevaluated in the BHRA); and

• Age-corrected skin surface areas for the potential receptors were used in the long-termHHRAs for evaluating exposure to surface water and sediments (these parameters were notcorrected in the BHRA)

Despite these slight differences in approach, there were no unacceptable cancer risks ornon-carcinogenic hazards calculated during any of the long-term HHRAs. Thus, under the “current” orfuture stream use conditions for potential on-base or off-base population exposures to sediment and surfacewater in the SCSSW OU, there continues to be no unacceptable human health risk.

Comparison of Data to Health-Based Cleanup Goals

Based on the remedial action requirements for the SCSSW OU, human health-based cleanup goalswere developed to evaluate the long-term monitoring results. These health-based goals were calculated foreach chemical using the most health-protective exposure scenario (i.e., the scenario associated with thehighest calculated risk or hazard). The residential exposure scenario was used for chemicals found off-baseand the construction worker scenario was used for on-base chemicals.

Four sets of human health-based cleanup goals were developed based on acceptable risk levelsestablished by the EPA. This included three levels for carcinogens based on the EPA-acceptable cancer riskrange of 10-6 (one additional case of cancer per one million), 10-5 (one additional case per one hundredthousand), and 10-4 (one additional case per ten thousand). One health-based risk level was also calculatedfor each non-carcinogenic chemical based on the target Hazard Index (HI) of 1.0. For chemicals with bothcarcinogenic and non-carcinogenic properties, the lower (more health-protective) level was selected. Sincesurface water is dynamic (constantly changing), the calculated health-based cleanup goals are referred to as“health-based indicators of water quality.” Both sediment and surface water values, however, provide thebasis for comparing chemical concentrations to health-based levels and for evaluating whether additionalremedial action may be necessary at the site.

During the BHRA and subsequent long-term monitoring HHRAs, health-based indicators for waterquality were not exceeded for any detected contaminants. No analytes in sediment samples exceeded the 10-4 RAO, which is the highest TBC concentration for a chemical detected at the site based on theUSEPA-accepted risk range (10-6 to 10-4). The third year long-term monitoring annual report (WCFS, 1998)contains the results of the comparison of site data to the acceptable 10-4 to 10-6 range of health-basedcleanup goals.

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TBCs are evaluated in the five-year review with respect to any new information on chemicaltoxicity, which may increase or decrease the TBC. Since the time of the third year monitoring report,toxicity data for two of the detected contaminants (alpha-chlordane and beryllium) have been updated(EPA, 1998). The new cancer and non-cancer toxicity data for alpha-chlordane show that the chemical isless toxic than indicated in the HHRAs. Beryllium was not identified as presenting a potential human healthrisk using the previous toxicity data, and although new data indicate that the chemical is slightly more toxicas a non-carcinogen, the change in the toxicity value is not significant for the site. [The change in thetoxicity value would result in a decrease of the non-carcinogenic action level for sediments from 21,800 to8,720 milligrams per kilogram (mg/kg). Compared to the range of detected concentrations for beryllium insediments (1.7 to 0.27 mg/kg), this change is not significant]. Since beryllium was not detected in surfacewater during the third year monitoring results, there is no effect on the level of risk for this medium.Additionally, the oral slope factor (SF) for beryllium has been withdrawn (the toxicity data show thatberyllium is not carcinogenic by ingestion). Thus, the chemical would not be calculated as a carcinogen viaingestion of sediments (i.e., the calculated overall carcinogenic risk would decrease).

Ecological Risk Assessment

The ecological investigation mandated by the ROD for the SCSSW OU was conducted as part of theenvironmental monitoring program to quantify potential effects of contaminant concentrations on thebiological environment of the creek (WCFS, 1997b) The main ERA field activities were performed duringOctober 1994 and June 1995. One noted observation of the ecological survey was that no federally listedthreatened or endangered species or their habitats were found to occur within the SCSSW OU.

For sampling data evaluated in the ERA, a constituent was selected as a chemical of potentialconcern (COPC) if it was detected in one ecological or quarterly-monitoring sample (i.e., detected in at leastone sampling event and at one location) at a concentration that exceeded the lowest availableecotoxicological benchmark for the specific medium. Using this screening process, forty-six COPCs(including chemical “groups” in some cases) were identified in either sediment, surface water, or bothmedia. These forty-six chemicals, or groups of chemicals, included:

• Nineteen inorganics. aluminum, antimony, arsenic, barium, cadmium, chromium, cobalt,copper, cyanide, iron, lead, manganese, mercury, molybdenum, nickel, selenium, silver,vanadium, and zinc;

• Eleven VOCs/SVOCs: acetone, benzidine, bis(2-ethylhexyl)phthalate, carbon disulfide,chlorobenzene, 1,4-dichlorobenzene, methylene chloride, toluene,2,3,6-trichloronaphthalene, triphenyl phosphine sulfide, and total xylenes,

• Four phenols and substituted phenols/nonylphenols: 2,4-dimethylphenol, pentachlorophenol,phenols and various substituted phenols (counted as one chemical group), and nonylphenols(counted as one chemical group);

• Total PCBs (counted as one chemical group): Aroclor 1254 and other mixtures; • Eight organochlorine pesticides: aldrin, alpha- and delta-BHC (counted as one pesticide),

alpha-chlordane, dieldrin, endosulfan sulfate, heptachlor, heptachlor epoxide, andmethoxychlor,

• Low molecular weight PARs (counted as one chemical group): acenaphthene, anthracene,fluorene, and phenanthrene;

• Medium molecular weight PAHs (counted as one chemical group): fluoranthene and pyrene;and

• High molecular weight PAHs (counted as one chemical group) benzo(a)anthracene,benzo(a)pyrene, benzo(g,h,i)perylene, benzo(k)fluoranthene, chrysene,dibenz(a,h)anthracene, and indeno(1,2,3-cd)pyrene.

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At the concentrations estimated for direct exposures to strictly-aquatic organisms (algae, benthic andwater-column invertebrates, and fish) and/or the doses estimated for indirect exposure (via the ingestionpathway) to terrestrial/semi-aquatic birds and mammals, sixteen of the forty-six chemicals were found topose a potential threat to ecological species. In general, the potential risks to strictly-aquatic organisms weresomewhat greater than the potential hazards to terrestrial animals. The potential risks associated with bothdirect (aqueous) and dietary exposures were largely, but not entirely, confined to on-base portions of Eastand West Soldier Creeks.

Results of the ERA showed that the most significant COPCs for sediments were cadmium,chromium, copper, nickel, silver, zinc, total PCBs, PAHs, certain organochlorine pesticides, and certainphenolic compounds. Among these, cadmium, chromium, copper, nickel, PCBs, and PAHs were the mostubiquitous. The ERA indicated that potential effects of these contaminants may extend downstream(northward) beyond the ERA study boundary at Interstate 40. However, the potential for downstreamhazards was not considered to be of major ecological significance, particularly at higher levels of biologicalorganization (i.e., populations, communities, ecosystems).

The most significant chemicals in surface water were barium, cadmium, chromium, copper, lead,rnolybdenum, and zinc. All of these chemicals, except molybdenum, were ubiquitous, and were alsoconsidered, to some extent, as possible contaminants of concern for areas downstream of Interstate 40.Copper and chromium were of particular concern due to their phytotoxicity and indirect effect on highertrophic levels. These two metals, as well as cadmium and zinc (and possibly barium), were also consideredto possibly directly affect invertebrate and fish communities.

Chromium, PCBs, and high molecular weight PAHs appeared to be the most significant chemicalsfor the ingestion pathways of terrestrial/semi-aquatic receptors. However, the lack of relevant dietarytoxicological data prevented detailed quantitative estimation of dietary risk to amphibians and semi-aquaticreptiles (e g, certain turtles and water snakes), which may be the most sensitive wildlife receptors for theOU.

Toxicity tests (acute and chronic effects under controlled laboratory conditions) were also measuredon ecological species exposed to sediment and surface water. With the exception of conditions in off-baseportions of West Soldier Creek, which did not appear to be as hazardous to aquatic receptors as indicated bythe risk estimates described above (based on the hazard quotient I hazard index approach), the toxicity testresults of the initial ERA generally corroborated the risk estimates. Biological surveys, particularly ofbenthic invertebrate and fish communities, also generally supported conclusions of the risk estimates.

Initial chemical-specific concentrations referred to as preliminary remedial goal options (RGOs)were developed as protective levels for ecological receptors in sediment and surface water of Soldier Creek.These levels are similar to the human health-based cleanup goals and can be used for evaluating chemicalconcentrations detected in the on-going five-year monitoring efforts and for evaluating whether additionalremedial action may be necessary at the site.

It should be noted that the ERA is based on very conservative exposure values and that the riskcharacterization is inflated by additive conservative assumptions. The degree to which exposures andtoxicities are overestimated leads to a great deal of uncertainty in the assessment. Additionally, the adverseeffects identified in the assessment were limited to a localized scale in on-base areas. Further data arenecessary to more accurately characterize the extent of contamination and the associated potential hazardsto ecological receptors in downstream areas. Interpretation of the ecological significance of the ERA resultsis provided in Section 6.

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Additional Remedial Actions

In addition, although it was not required by the ROD, additional corrective measures have beenpursued as a means to alleviate the risk to human health and the environment. These measures includeremoval of contaminated soils in West Soldier Creek and cementing the on-base portion of the channel. Inaddition, contaminated sediments were removed from East Soldier Creek and the channel was cementedaround the dam near the IWTP.

SECTION 4 PROGRESS SINCE LAST FIVE-YEAR REVIEW

Protectiveness statement from ROD

As stated in the ROD, the protectiveness statement is as follows: the selected remedy is protective ofhuman health and the environment because monitoring of the concentrations of the chemicals of concern inSoldier Creek sediment and surface water will be conducted and an ecological investigation will beperformed. Continued monitoring will determine if a human health risk develops from these media at theoperable unit. Implementation of the selected remedy does not pose any unacceptable short-term risks orcross-media impacts. Because carcinogenic risk levels are within the acceptable risk range (1E-04 to 1E-06)and the HIs for noncarcinogens are less than 1.0, the sediment and surface water contamination at theSoldier Creek Sediment and Surface Water Operable Unit does not present a significant threat to humanhealth. Based on the qualitative environmental assessment conducted as a part of the baseline riskassessment, a significant threat to the environment does not exist. Therefore, the only response actionrequired at this time is that specified in the selected remedy. The continued monitoring of Soldier Creeksediment and surface water at on-base and off-base sampling locations will be adequate to address operableunit contamination because the concentrations of the sediment and surface water COCs do not exceed theremediation goals (risk-based cleanup levels) established for the operable unit. The ecological assessment tobe conducted will determine the effects of contaminant concentrations on the biological environment ofSoldier Creek. Yearly and at the time of the five-year review, the results of the monitoring program will beevaluated to determine if a remedial action needs to be implemented or additional monitoring needs to beconducted at the operable unit.

Protectiveness Statement from last Five-Year Review

As stated in previous Five-Year Review. The results from the ERA indicated that potential forecological risk in the area Subsequent remedial measures have been implemented by OC-ALC/EM toremove or reduce potential contaminant sources and .minimize the potential for sediments to move off baseand pose a human health or ecological threat to downstream receptors. Continued annual monitoring andevaluation will determine the need for further remedial actions, if necessary.

Status of Recommendations from Last Five-Year Review

Recommendations made in the previous five-year review are as follows: 1) To ensure that exposureto and migration of contaminants does not occur at concentrations greater than human health based andecological remediation goals, annual monitoring efforts and risk evaluations should continue, 2) theadditional sampling details identified in the initial ERA should be added to the next round of monitoring tomore clearly define the ecological risk, and 3) the new toxicity data should be used in subsequent HHRAs.As of this Five-Year review, all recommendations from the previous review have been completed.

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As a result of recommendations made in the previous five-year review, the second ERA generatednew HHRAs using current toxicity data. Additional objectives of the second ERA were as follows: 1) toevaluate the effects of rerouting (removal) of IWTP and STP discharges on the distribution of COECs andany adverse ecological impact in East Soldier Creek, 2) to reduce the uncertainty associated with theprevious exposure and toxicity assessments and 3) to include improved/expanded sample analyses.Incorporation of those factors mentioned above into the second ERA indicated no detriment to ecologicalrisk Further discussion on the risk assessments is included in the conclusions in Section 8.

Additional Progress Since last Five-Year Review

As previously mentioned, although it was not required by the ROD, additional corrective measureshave been pursued as a means to alleviate the risk to human health and the environment. These measuresinclude removal of contaminated soils in West Soldier Creek and cementing the on-base portion of thechannel. In addition, contaminated sediments were removed from East Soldier Creek and the channel wascemented around the dam near the IWTP.

SECTION 5 FIVE-YEAR REVIEW PROCESS

A level 1 review was conducted for the SCSSW OU. The review was conducted by Sara Sayler ofOC-ALC/EMPE. The key elements of the five-year review included: document review, interviews, siteinspection, evaluation of findings and report preparation.

Site Inspection

Interviews An interview was conducted with the SCSSW Site Manger James Dawson (OC-ALC/EMPE) on

November 16, 2002, to discuss the status of the SCSSW OU.

Site Visit A site visit was conducted on January 8, 2003. During the site visit, landscaping and current

conditions of portions of the SCSSW site was noted. A walking/jogging path has been constructed along thecreek. No distressed vegetation was observed.

Community Involvement

Community involvement was initiated at the October 29th, 2002 community advisory board (CAB)meetings by announcing that a Five-Year Review process was underway. In addition, communitycomments/concerns were solicited during the January 28th, 2003 CAB meeting

Data Review

Since the time of the original BHRA and qualitative ERA, additional information on the nature andextent of contamination has been collected, including additional sediment and surface water sampling, aswell as information on pesticides and polychlorinated biphenyls (PCBs) not previously evaluated. A reviewof the Seventh Year Long Term Monitoring Annual monitoring data is discussed below. Table 3 inAppendix A contains the sample results of the Seventh Year Long Term Monitoring. This table includesdata obtained from November 1994 to September 2001.

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SURFACE WATER

Metals Twenty metals were detected during the seventh year of monitoring. Total metals detected in surface

water by Method 6010/6020/7740 were: aluminum, antimony, arsenic, barium, beryllium, cadmium,calcium, chromium, cobalt, copper, iron, lead, magnesium, manganese, nickel, potassium, sodium, thallium,vanadium, and zinc. Metals concentrations in surface water did not exceed BHRA or HHRA I screeningcriteria during the seventh year of monitoring. Metals concentrations in surface water samples have notexceeded screening criteria during the past seven years of long-term monitoring.

PCBs and Chlorinated Pesticides No PCB or pesticide analytes were detected in surface water samples during the seventh year of

monitoring. Therefore, PCB and pesticide concentrations did not exceed BHRA or HHRA I risk-basedscreening criteria in surface water. PCB and pesticide concentrations in surface water samples have notexceeded screening criteria during the past seven years of long-term monitoring.

Semivolatiles Bis(2-Ethylhexyl)phthalate and Diethyl phthalate were the only semivolatile compounds detected in

surface water during the seventh year of monitoring. Bis(2-Ethylhexyl)phthalate was detected in fivesurface water samples. The maximum detected concentration of bis(2-Ethylhexyl)phthalate was 8micrograms/liter at QW06-SW-1701. Diethyl phthalate was detected in one sample at a concentration 1.1micrograms/liter at QE11-SW-1801.

Semivolatile concentrations did not exceed BHRA or HHRA I risk-based screening criteria insurface water during the seventh year of monitoring. Semi-volatile concentrations in surface water haveexceeded screening criteria in only one sample during the past seven years of monitoring. During the fourthof sampling, bis(2-Ethylhexyl)phthalate exceeded the HHRA 10-6 screening criteria at QE02, located onOutfall G.

Volatiles Toluene was the only volatile organic compound was detected in surface water during the seventh

year of monitoring. Toluene was detected in one sample (QW07-SW-1701) at 5 micrograms/li ter.

Volatile concentrations in surface water did not exceed BHRA or HHRA I risk based screeningcriteria during the seventh year of monitoring. VOC concentrations in surface water samples have notexceeded screening criteria during the past seven years of long-term monitoring

Wet Chemistry Surface water samples were analyzed for the following wet chemistry parameters: alkalinity,

chemical oxygen demand, hardness, total dissolved solids, total organic carbon, total suspended solids,chloride, and sulfate.

SEDIMENT

A total of 30 sediment samples were collected during the seventh year of long-term monitoring.Sample results can be found in Table 4 of Appendix A.

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Metals Twenty four metals were detected during the seventh year of monitoring. Metals detected by

Methods 6010 and 7471 were: aluminum, antimony, arsenic, barium, beryllium, cadmium, calcium,chromium, cobalt, copper, iron, lead, magnesium, manganese, mercury, molybdenum, nickel, potassium,selenium, silver, sodium, thallium, vanadium, and zinc. Metals concentrations in sediment did not exceedBHRA or HHRA I screening criteria in any of the past seven years of long-term monitoring.

PCBs and Chlorinated Pesticides Aroclor 1254 was the only PCB detected in sediment during the seventh year of monitoring. It was

detected in one sample (SC-QW05-SD-1801) at 410 micrograms/kilogram. Pesticides and PCBs were notidentified as potential COPCs in the BHRA. HHRA I carcinogenic and non-carcinogenic screening criteriafor PCBs and pesticides were not exceeded during the seventh of monitoring.

Semi-Volatile Organics Twenty-six semi-volatile organic compounds (SVOCs) were detected during the seventh year of

monitoring. The highest SVOC concentration was pyrene (4,900 microgram/kg), which occurred inQW05-SD-1801. The most frequently detected SVOC with 23 detections in sediment samples wasbis(2-Ethylhexyl)phthalate. Five SVOCs were identified as potential COCs by exceeding the 10-6 risk basedscreening criteria during the seventh year of monitoring. The PAHs benzo(a)anthracene,benzo(b)fluoranthene, benzo(a)pyrene and chrysene, exceeded the BHRA 10-6 screening criteria inQW05-SD-1801 Benzo(k)fluoranthene, benzo(b)fluoranthene, and benzo(a)pyrene exceeded the HHRA 10-6

screening criteria in QW06-SD-1801. Benzo(a)pyrene exceeded the HHRA 10-6 screening criteria inQW05-SD-1801 and QW06-SD-1801 samples during the seventh year of monitoring. The primary source ofrelease of PAHs to the environment occurs as a result of combustion emissions. Discharges may also occurfrom spills of fuel oils, gasoline, etc., or from runoff from sources such as roadways, asphalt parking lot, orrailroad ties.

Historically, there has been an exceedence of 10-6 BHRA and HHRA screening criteria for a seriesof PAHs ((benzo(a)anthracene, benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, andchrysene). In the past, concentrations of analytes decreased off-base as compared to on-base. Prior to theseventh year, the only off-base West Soldier Creek exceedences of 10-6 screening criteria (BHRA andHHRA I) occurred during the 3Qtr 1Yr and 1 Event 3Yr-monitoring events in segment QW05. The onlyoff-base East Soldier Creek exceedences of 10-6 screening criteria (BHRA) occurred during the 4Qtrl Yrmonitoring event in segment QE10. Analytical results from the furthest downstream segment of East SoldierCreek (QE11) have not exceeded BHRA or HHRA I screening criteria during any sampling event since theonset of long-term monitoring.

Volatiles Seven volatile compounds (VOCs) were detected in sediment samples during the seventh year of

monitoring. The VOCs detected during the seventh year of monitoring are presented in Table 3 of AppendixA (Table 3 also includes all sample data from November 1994 through September 2001). Volatileconcentrations in sediment did not exceed BHRA or HHRA I screening criteria. The highest VOCconcentration was chlorobenzene detected in sample QE11-SD-1701 at 3,400 microgram/kg.

EIGHTH YEAR SAMPLING EVENT

At the time of this writing, only the First Event of the Eighth Year Sampling Report had beencompleted. The results are discussed in the following text.

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The sampling was conducted from April 10-11, 2002. A total of six surface water samples andtwelve sediment samples were collected during the field effort. Contaminant concentrations associated withthis sampling event were compared with risk-based screening criteria which were based on exposure factorsdeveloped in the BHRA conducted as part of the RI/FS and the HHRA I for human health.

BHRA Screening Exceedances No exceedances of BHRA screening criteria were identified for surface water analytical results from

East Soldier Creek and West Soldier Creek. Sediment analytical results did not exceed BHRA screeningcriteria for the non-carcinogenic screening criteria or 10-4 carcinogenic risk.

Sediment analytical results exceeded BHRA 10-6 screening criteria in a segment located off-baseEast Soldier Creek (QE11). No screening criteria were exceeded on West Soldier Creek or on-base EastSoldier Creek. The BHRA contaminants of concern with concentrations in excess of 10-6 carcinogenicscreening criteria were benzo(a)anthracene, benzo(a)pyrene, benzo(b) fluoranthene, benzo(k) fluoranthene,and chrysene.

HHRA I Screening Exceedances No exceedances of HHRA I screening criteria were identified for surface water analytical results

from East Soldier Creek and West Soldier Creek. Sediment analytical results did not exceed HHRA Inon-carcinogenic screening criteria or screening criteria for 10-5 or 10-4 carcinogenic risk.

Sediment analytical results exceeded HHRA I 10-6 screening criteria in two segments locatedoff-base East and West Soldier Creek (QE11 and QW06). No screening criteria were exceeded on-base EastSoldier Creek, or on-base West Soldier Creek. The HHRA I contaminant of concern with concentrations inexcess of 10-6 carcinogenic screening criteria was benzo(a)pyrene.

Tables 5 and 6 of Appendix A contain the results of the BHRA and HHRA 10-6 Screening Criteriarespectively.

SECTION 6 TECHNICAL ASSESSMENT

Question A. Is the remedy functioning as intended by the decision documents? The remedy specified by theROD included only requirements for sampling at specific locations in and around the OU. The past fiveyears of sampling indicated no consistent areas of concern. Given this information, the remedy can beconsidered to function as intended.

Question B: Are the exposure assumptions, toxicity data, cleanup levels, and remedial action objectives(RAOs) used at the time of the remedy selection still valid? Any changes in these parameters have beenaccounted for in additional rounds of both ecological and human health risk assessments.

Question C. Additional information arisen to question the protectiveness of the selected remedy? Not at thistime.

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SECTION 7 ISSUES FROM PREVIOUS REVIEW

The following are comments and subsequent OC-ALC/EM responses pertaining to the Soldier CreedSediment and Surface Water section of the previous Five-Year Review document:

1) Q. What was the basis for the change in the SCSSW OU boundary? A. The original RI sampled Soldier Creek all the way to Reno Avenue. The sampling area wasreduced based on results from the RI. The sampling area was reduced to approximately I-40 sincethe RI indicated that this sampling area would be sufficient.

2) Q: What is the status of the ERA? A On-base areas were excavated and removed. Sampling still occurs at the base boundary andoff-base to confirm that there is no contamination there Because the contaminants were removed,there is no longer a necessity to address ecological issues beyond what is done in the annual reports.

3) Q Are there any known off-base wells known to be used for drinking water purposes? A. To the best of our knowledge, there are no off-base wells known to be used for drinking water.

SECTION 8 CONCLUSIONS

Interpretation of Human Health Significance

As required by the ROD, the five-year monitoring program for the SCSSW OU has beenimplemented. Over the five-year duration of the monitoring program, health-based indicators for waterquality (health-based cleanup goals) were not exceeded for any chemical detected in water. Additionally, noanalytes in sediment samples exceeded the 1E-04 RAO, which is the highest TBC level (humanhealth-based action level) for a detected chemical based on the EPA-acceptable risk range (1E-06 to 1E-04).

In addition to these results, the quantitative HHRAs did not show an unacceptable health risk.Results of the HHRAs for the first three years of the monitoring program, as well as results of the BHRA,indicate that under “current” or future stream use conditions there is no unacceptable human health risk(cancer or noncancer risk) for potential on-base or off-base receptors due to sediment and surface waterexposures for the SCSSW OU.

Interpretation of Ecological Significance

Initial ERA Results The initial ERA indicated that forty-six chemicals, or chemical groups, were of ecological concern

(pesticides, PCBs, PAHs, and other volatile and semi-volatile compounds). Ecological exposures werefound to pose some risk of acute and chronic, sub-lethal effects to certain individual receptors or individualsof receptor classes.

The study indicated that the ecological exposures and effects were largely confined to the on-baseportions of the SCSSW OU. The concentrations of the PAHs were found to vary between sampling

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segments and sampling events suggesting that multiple on-base origins for the PAHs may exist. Forexample, highest PAH concentrations for the second year of monitoring occurred in the stream segmentrepresenting Outfall G, but during the third year of monitoring, many of the highest PAR concentrationsoccurred in the segment representing Outfall F. Data also indicated that discharge from Outfall G is apossible source of the PCB contamination. Although all electrical transformers with PCB-containing oilwere replaced at the base in 1989, minor leaks or spills of old transformer oil may have previously enteredthe storm drain system. There are no known industrial processes that use PCBs in the area.

The ERA states that the adverse affects are clearly limited to a localized scale. This is also whyresults showed that the most ecologically-relevant actual or potential effects are those on strictly-aquaticcommunities (i.e., algae, benthic and water-colurnn invertebrates, fish) and small terrestrial/semi-aquaticanimals. The ERA states that it is unlikely that larger terrestrial vertebrates (wildlife) are at much risk fromsite-related chemicals.

The conclusions of this limited initial ERA also indicate that the risk characterization is inflated byadditive conservative assumptions and that there is much uncertainty related to the degree to whichexposures and toxicities are overestimated. The conclusions indicate that better understanding of theingestion-pathway exposures is needed (as opposed to estimating dietary constituent concentrations ofchemicals) and additional sampling may be required. As an example, the ERA suggests sampling andanalyses of plant tissues (particularly fruits), amphibians, and/or small mammals to provide a betterunderstanding of the dietary exposures to higher-level consumers as well as more insights into the actualavailability for direct uptake of the chemicals

Second ERA Results completed since last Five-Year Review Two basic factors led to the second EA: 1) salient changes in conditions within the SCSSW OU –

specifically, the complete removal of the Industrial Waste Treatment Plant and Sewage Treatment Planteffluents, and 2) the substantial uncertainty associated with risk characterization in the first EA. In order toreduce the uncertainty associated with the previous exposure and toxicity assessments, expanded and/orimproved procedures intended to fill, or mitigate, many of the key data gaps identified by the initial EAwere developed This was done by: 1) reviewing analytical methodologies to obtain increased analyticalsensitivity for some analyses, 2) expanding replication of samples to increase statistical confidence, 3)sampling biological tissues in multiple potential forage or prey items, 4) measuring several physicochemicalcharacteristics to provide further insight into the fate and transport (especially bioavailability) of theCOECs, and 5) developing biota-sediment accumulation factors using field-collected biological tissues anddata from bioaccumulation tests conducted in the laboratory. Based on the ecological endpoints previouslyestablished and focusing on the COECs identified during the initial EA, the second EA re-evaluatesexposures to ecological receptors in light of changed conditions, updated toxicological information and theexpanded and/or improved site-specific information obtained in 1997.

Interpretation of ecological significance is summarized as follows. The estimated and apparentadverse effects of several of the COECs, based on the results of this second EA, suggest impact at thepopulation and community levels, primarily to strictly-aquatic receptors and small semiaquatic vertebrates).However, these effects are largely confined to on-base portions of the SCSSW OU. In addition,interpretation of significance is blurred by the overt presence of numerous other stresses, particularly theextensive physical modifications of habitats in both creeks.

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SECTION 9 DEFICIENCIES

There were no deficiencies identified for the second Five-Year Review of the SCSSW OU.Recommendations identified in the previous Five-Year Review were carried out.

SECTION 10 RECOMMENDATIONS

Based on results of the HHRAs and comparison of data to health-based action levels, there is nounacceptable risk to human health for the SCSSW OU

In addition, numerous activities have occurred in the area of the SCSSW OU that serve to remove orreduce potential contaminant sources. Certain remedial measures have also recently been implemented byOC-ALC/EM at West Soldier Creek. Flight line criteria at Tinker AFB have prompted upgrades to thelandscape along the creek. The channel of the creek has also been concreted. This action serves as a facilityimprovement as well as a remedial measure (although not identified as a ROD requirement) to minimize thepotential for sediments to move off-base and pose a human health or ecological threat to downstreamreceptors.

Protectiveness of the environment has been attained by these remedial responses. As required in theROD for this site, annual monitoring efforts were carried out during the previous five years to ensure nodanger to human health or the environment exists. However, since there have been no exceedences of healthbased screening levels (based on 10-4) in the sampling over the past five years, it is recommended thatsampling be discontinued at the SCSSW OU and the site be considered closed in accordance with the ROD.

SECTION 11 NEXT REVIEW

After gaining regulatory acceptance of this Five-Year Review, Tinker will request de-listing of theOU. If the site is de-listed, no additional Five-Year Reviews will be required.

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APPENDIX A

APPENDIX B

APPENDIX B LIST OF DOCUMENTS REVIEWED

B&V, Record of Decision, Tinker AFB-Soldier Creek Sediment and Surface Water Operable Unit, FinalReport, August 1993.

B&V, Remedial Investigation Report, Multi-Phased Remedial Investigation (RI) of Surface and SubsurfaceContamination of Soldier Creek at Tinker AFB, Oklahoma, Final Report, February 1993.

Ch2MHill, Seventh Year Long-Term Monitoring Annual Report for Long-Term Monitoring of Soldier CreekSediment and Surface Water Operable Unit, Final Report, October 2002.

CH2MHill, First Event Eighth Year Sampling Report (April 2002 Sampling Event) for Long-TermMonitoring of Soldier Creek Sediment and Surface Water Operable Unit, Final Report, June 2002

OC-ALC/EMR, Memorandum for Chris Villarreal (EPA) on Soldier Creek Sediment and Surface WaterOperable Unit, January 2002.

OC-ALC, Memorandum for Cathy Scheirman (OC-ALC/EM) on Soldier Creek Sediment and Surface WaterOperable Unit, October 2002.

Parsons ES, Five-Year Review Report for the Soldier Creek/Building 3001 APL Site, Final Report,September 1998

URS Greiner Woodward Clyde, Ecological Assessment II Report for the 1997 Ecological Assessment ofSoldier Creek, Tinker AFB, Oklahoma City, OK, Final Report, Volumes I, II, and III, May 1999.

APPENDIX C

APPENDIX C PHOTOS

1. Stream gauging and sampling point at Outfall G to East Soldier Creek. 2. Stream sampling segment QEO6 on East Soldier Creek. 3. Excavation at West Soldier Creek, prior to concrete pouring. 4. Preparation for concrete channel along West Soldier Creek. 5. Excavation of West Soldier Creek channel for concrete resurfacing. Note monitoring wells for

Building 3001 recovery system in background. 6. Excavation activities prior to concrete pouring for flightline drainage Building 3001 to the east,

flightline and runway to the west. Monitoring wells and extraction well field to east.