DEPARTMENT OF THE AIR FORCE 90TH SPACE WING (AFSPC) … · 2020. 7. 17. · Cheyenne, Wyoming FINAL RECORD OF DECISION AMENDMENT ZONE C, OPERABLE UNIT 11, LANDFILL 3 REMEDIAL ACTION

SDMS Document ID DEPARTMENT OF THE AIR FORCE

90TH SPACE WING (AFSPC) 1031817

14 Sep 04

MEMORANDUM FOR

FROM:

MS. JANE CRAMER WDEQ/WQD Herschler BIdg, 4 West Cheyenne WY 82002

90 SW/EM 5305 Randall Ave F. E. Warren AFB WY 82005-2266

MR. ROBERT STITES (8EPR-F) EPA Region VIII RPM 999 18th Street, Ste 300 Denver CO 80202-2466

SUBJECT: Zone C - Final Record of Decision Amendment

1. We are sending the Final Record of Decision Amendment for Zone C, Operable Unit 11, Landfill 3 to Air Force Space Command (AFSPC) for signature today. I have attached copies for you to begin your internal reviews concurrently. Once we receive the signed signature pages from AFSPC I will forward them to you for appropriate signatures.

2. If you have any questions or need additional information, please contact Mr. Glen Verplancke at (307) 773-4384, or myself at (307) 773-4147, at your convenience.

L. WRIGHT, Gs43 FEW Remedial Project Manager

Attachment: ROD Amendment

GUARDIANS OF THE HIGH FRONTIER

FINAL

RECORD OF DECISION AMMENDMENT for

Zone C, Operable Unit 11, Landfill 3 Remedial Action

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F. E. Warren Air Force Base, Wyoming

September 2004

FINAL

RECORD OF DECISION AMMENDMENT for

Zone C, Operable Unit 11, Landfill 3 Remedial Action

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F. E. Warren Air Force Base, Wyoming

September 2004

Final Zone C ROD Amendment F. E. Warren Air Force Base

Cheyenne, Wyoming

FINAL RECORD OF DECISION AMENDMENT ZONE C, OPERABLE UNIT 11, LANDFILL 3 REMEDIAL ACTION

F.E. WARREN AIR FORCE BASE, WYOMING

1.0 INTRODUCTION

The purpose of this document is to explain the fundamental change made to the remedial action (RA) selected in the Record of Decision (ROD) for Zone C, Operable Unit 11 (OUl 1), Landfill 3 (LF3), F. E. Warren Air Force Base (FEW). The Zone C ROD (dated September 2001) was signed by the United States Air Force (USAF), the Wyoming Department of Environmental QuaUty (WDEQ), and the United States Envirormiental Protection Agency (EPA) in December 2001.

The Lead Agency for the site (Zone C, OUll, LF3, hereinafter Zone C) is the USAF. EPA and WDEQ are support agencies. This ROD Amendment has been prepared to fiilfill the* USAF's public participation responsibilities under Section 117(c) ofthe Comprehensive Environmental Response, Compensation, and Liability Act of 1980, 42 U.S.C. Section 9601, et seq. (CERCLA commonly known as "Superfund"), as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), and 40 C.F.R. Section 300.435(c)(2)(ii), which is part of the National Oil and Hazardous Substances Pollution Contingency Plan (NCP).

Based on pre-design pump testing and analyses, it does not appear feasible to extract the entire Zone C plume as was plaimed in the September 2001 Zone C ROD. The USAF and EPA with WDEQ concurrence have therefore changed the remedy selected to address the groundwater at Zone C from pump and treat to in-situ treatment combined with monitored natural attenuation (MNA). CERCLA and the NCP require a ROD amendment if a fundamental change is made to the remedial action selected in the original ROD. Since this action reflects a change in the primary treatment technology for this site, it is considered a fundamental change and a ROD amendment is the appropriate documentation.

The September 2001 Zone C ROD and all supporting docimientation, including the Supplemental FS, for the RA at Zone C are incorporated by reference herein and are included in the F. E. Warren Information Repository (IR), which is available for public review at the Laramie County Library, 2800 Central Avenue, Cheyenne, WY 82001. The library can be reached at (307) 634-3561 for hours of availability.

This ROD amendment will be made a part ofthe Administrative Record for this site as required by the NCP 300.825(a)(2) and will also be placed in the IR.

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Final Zone CROD Amendment F. E. Warren Air Force Base

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2.0 SITE HISTORY, CONTAMINATION AND SELECTED REMEDY

Based on previous investigations and groundwater plume maps, former LF3 is the apparent source of contaminants in Zone C. The landfill reportedly operated from the mid-1950s to the mid-1960s, receiving domestic solid waste, waste oils and solvents, battery acid, and other wastes. Detailed records were not maintained for the landfill; however, a review of air photographs indicates that landfill operations continued until at least 1969. During the removal action conducted in 2000, this landfill was completely excavated; wastes were sampled, characterized as non-hazardous, and were relocated to the Waste Co-location Area (WCA) at FEW. No further source response actions are planned for the LF3 area.

A plume of groundwater contaminated with chlorinated volatile organic compoimds (VOCs) originates in the south-central portion of former LF3 and extends east-northeast approximately one-half mile toward Crow Creek. As identified in the RI (USAF 2000b) and FS (USAF 2000c), the groundwater contaminants of concem (COCs) attributable to Zone C waste management activities are Trichloroethylene (TCE) and cw-1,2-dichloroethene (DCE). The maximum contaminant levels (MCLs) for TCE and DCE are 5 ug/L and 70 |j,g/L, respectively. The contamination in the Zone C groundwater is relatively shallow, with a maximum depth of contamination at approximately 55 ft bgs. The highest concentration within the plume is 110 Ug/L. Groundwater beneath FEW has not been formally classified by the Wyoming Department of Environmental QuaUty for a specific use. Although groundwater beneath Zone C is currently not used, the shallow groimdwater immediately off base is used for drinking water and agriculture. For a more detailed presentation ofthe nature and extent of contamination, see the Zone C RI (USAF 2000b) and FS (USAF 2000c).

2.1 SUMMARY OF THE SEPTEMBER 2001 ZONE C ROD REMEDY

The remedy selected in the September 2001 Zone C ROD for cleaning up the contaminated groimdwater within Zone C at FEW was extraction and aboveground treatment of contaminated groundwater, otherwise known as "pump and treat." The ROD also documented all interim and removal actions taken at this site prior to its signing and incorporated these actions, by reference, into this final selected remedy for Zone C.

The primary remedial action objective (RAO) is to restore the aquifer to drinking water standards. The key applicable or relevant and appropriate requirements (ARARs) that drive the RAO are the drinking water MCLs. Restoration will be achieved when TCE and its degradation products are reduced to their respective MCLs. The MCL for TCE is 5 ^g/L. The selection of the pump and treat remedy was based on the Feasibility Study (FS) conclusions (USAF 2000b) and other documents in the Administrative Record. The selected remedy estabUshed the foUowing components ofthe Zone C pump and treat system:

September 2004 Page 2 of 16


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• Wells were to be installed within the contaminated groundwater plume to capture groundwater within all on-site areas with concentrations of TCE above the MCL of 5 ug/L.

• Groundwater would then be pumped from the wells into a treatment system designed to collect and treat groimdwater.

• The groundwater would then be treated to remove volatile organic compoimds (VOCs) by a proven technology. The treatment technology was to be selected during the remedial design phase of the process from among the four presumptive remedies for treatment of groundwater contaminated with VOCs. These were air stripping, carbon adsorption, chemical/ultraviolet (UV) oxidation, and aerobic biological reactors.

• Treated groundwater would then be discharged to the surface, re-mjected into the aquifer or discharged to a publicly owned treatment works. The effluent discharge option was to be selected during the remedial design phase ofthe process.

Refer to the September 2001 Zone C ROD for a complete description ofthe original remedy.

3.0 BASIS FOR THE CHANGE TO THE 2001 ZONE C ROD REMEDY

The change in remedial action was necessitated by information obtained during a supplemental field investigation conducted by the USAF during 2002. As stated in the Internal Draft Zone C Field Activities Report 2, Supplemental Field Investigation (USAF 2002), the hydrogeology in the vicinity of Zone C is highly variable, and this was not fully identified or accounted for in the Zone C Remedial Investigation (RI) or FS. Based on pre-design pump testing and analyses, it does not appear feasible to exfract the entire Zone C plume as was planned in the September 2001 Zone C ROD. The hydraulic conductivity (ability to transmit water) of the subsurface materials was much lower than expected over all but a small portion ofthe plume. Therefore, the USAF has re-evaluated altematives to address Zone C groundwater impacts. Results of these evaluations are presented in the Zone C Supplemental FS (USAF 2003). The Supplemental FS was prepared by evaluating recent information presented in the Zone C Field Activities Reports 1 (USAF 2001b) and 2 (USAF 2002) and the Zone C Supplemental MNA Groundwater ModeUng Report (Appendix A ofthe Supplemental FS).

4.0 DESCRIPTION OF ALTERNATIVES

In order to optimize the remedy selected, the Zone C aquifer was divided into shallow and intermediate/deep zones. The boundaries between these aquifer zones are distinct in some areas and difficult to discern in others. The shaUow zone generally corresponds to groundwater with a maximum depth of 25 feet below ground surface. The intermediate/deep zone generally corresponds to groundwater that resides between 25 and 50 feet below ground surface.

Each altemative also includes the Land Use Controls, described in Section 6.0, to minimize the potential for completing the ingestion and inhalation exposure pathways for the Zone C groundwater plume. These confrols would provide managerial means of ensuring the overall protectiveness ofthe remedy. For a detailed comparison of these altematives, please consult the supplemental FS (USAF 2003).



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Alternative 1, monitored natural attenuation (MNA)

Altemative 1 would involve periodic monitoring of existing groimdwater wells within and outside the plume area that would be utilized to monitor the natural attenuation process until remedial goals are met. Natural attenuation is comprised of biological, chemical, and physical processes that reduce contaminant mass, toxicity, mobility, volume, and/or concenfration without the application of actively engineered remediation techniques. Modeling results indicate that TCE would be reduced to the MCL of 5 |ig/L throughout the plume in approximately 50 years.

Alternative 2, In-Situ Treatment with MNA

Altemative 2 consists of in-situ freatment combined with MNA. The in-situ portion involves delivery of a chemical oxidant, such as potassium permanganate (KMn04), to contaminated media (groundwater or soil) to desfroy the contaminants or convert them to irmocuous compounds commonly found in natural settings. The delivery of a sfrong oxidant to the contaminated groundwater creates a spontaneous chemical reaction that breaks the carbon-carbon bonds in chlorinated VOCs such as TCE effectively converting the TCE into innocuous compounds. The in-situ freatment would be implemented in the intermediate/deep zone where the concenfrations of TCE are the highest. Only the higher concenfration portion (an area approximately 300' by 100') ofthe plume will be freated with in-situ chemical oxidation. The remainder ofthe plume would be allowed to reach remedial goals through MNA. The MCL of 5 (ig/L would be achieved after a period of approximately 30 years. The exact location ofthe freatment area and the specific chemical oxidant to be used will be determined in the design phase of the remedy.

Alternative 3, Groundwater Extraction and Treatment

Altemative 3 consist of "full plume" groundwater exfraction and freatment involving exfraction of contaminated groundwater, aboveground freatment to remove the COCs, and discharge of freated groundwater.

This altemative was eliminated from further evaluation because groundwater modeling results indicate that the entire plume could not be feasibly exfracted and the addition of more wells attempting to achieve this provides almost no additional remediation or cost benefit. Modeling suggests that it would not be feasible to constmct a groundwater exfraction system capable of exfracting the entire Zone C plume.

Alternative 4, Groundwater Extraction and Treatment combined with MNA

Altemative 4 consists of "partial plume" groundwater exfraction and granular activated carbon (GAC) freatment in combination with MNA. A groundwater exfraction and freatment system would be implemented to remove contaminated groundwater from the high concenfration area of the intermediate/deep zone TCE plume. The exfraction system would be shut off once TCE concenfrations were reduced to 5 ug/L in the zone of influence ofthe system (approximately 10 years). Modeling results indicate that an additional 20 years of MNA will be needed to reduce TCE concenfrations to 5 ug/L in the remainder ofthe plume for a total of 30 years to reach the MCL. The number and location ofthe exfraction wells will be determined in the design phase of



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the remedy.

5.0 EVALUATION OF ALTERNATIVES

The NCP remedy evaluation criteria were applied to the each of the potential cleanup altematives. The relative performance of each altemative was evaluated with respect to each of the first seven ofthe nine NCP criteria. The remaining two criteria are addressed in Section 10, Agency Comments and the attached Responsiveness Summary for this ROD Amendment. To comply with the NCP, the criteria must be applied to all remedial altematives. These criteria, outUned in Guidance for Conducting RI/FSs Under CERCLA (EPA 1988) and the NCP [40 CFR 300.430(f)(5)(i)], fall into three categories: threshold criteria, balancing criteria and modifying criteria. Table 1 summarizes the nine criteria within these broad categories. For a detailed discussion ofthe comparative analysis of altematives please refer to the Supplemental FS Report (USAF 2003).

5.1 Overall Protection of Human Health and the Environment

Altemative 1 provides adequate protection of human health and the environment through the natural attenuation processes that reduce TCE in the groundwater over time. This altemative would reduce concenfrations of TCE throughout the plume to the MCL in approximately 50 years. Use of the groundwater as a drinking water source would pose an unacceptable risk and would be addressed through the implementation of land use confrols until MCLs are met. Long term monitoring would allow continued evaluation of contaminant migration and natural attenuation.

Altemative 2 provides adequate protection of human health and the enviroimient through in-situ freatment, using a chemical oxidant, combined with natural attenuation processes. Use of the groundwater as a drinking water source would pose an unacceptable risk and would be addressed through the implementation of land use confrols until MCLs are met in approximately 30 years.

Altemative 4 provides adequate protection of human health and the envfronment through exfraction and aboveground freatment combined with natural attenuation. Use of the groundwater as a drinking water source would pose an unacceptable risk and would be addressed through the implementation of land use confrols until MCLs are met in approximately 30 years.

5.2 Compliance with ARARs

No new ARARS have been added in this amendment. A complete description of ARARs is found in Section 2.13.2 ofthe September 2001 Zone C ROD (USAF 2001a). A brief assessment of comphance with the ARARs is provided below.

Altemative 1. With LUCs, the use of MNA as a remedial altemative for contaminated groundwater in Zone C would comply with all potential location- and action-specific ARARs. The modeling results indicate that the chemical-specific ARAR (reduce TCE to 5 ̂ g/L



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throughout the plume) would be reached in approximately 50 years. No permits would be needed for this altemative.

Altemative 2. With LUCs, the use of in-situ chemical freatment and MNA as a remedial altemative for contaminated groundwater in Zone C would comply with all potential location-and action-specific ARARs. The modeling results indicate that TCE would be reduced to the MCL of 5 ug/L, the chemical-specific ARAR, in approximately 30 years.

Altemative 4. Exfraction and freatment combined with MNA as a remedial altemative would be designed to comply with all potential location- and action-specific ARARs. The modeling results indicate that TCE would be reduced to the MCL of 5 |i,g/L throughout the plume in approximately 30 years.

5.3 Long-Term Effectiveness

Altemative 1 would provide long-term effectiveness and permanence because the contaminant concenfrations would be reduced to acceptable levels, altiiough it would occur over a longer period of time. The effectiveness would be verified by long-term monitoring, which provides a confrol through management ofthe plume. LUCs would limit or prevent the use of groundwater and eliminate the exposure pathway.

Altemative 2 provides long-term effectiveness and permanence because this altemative uses an active freatment technology to reduce risks. Chemical freatment will reduce the concenfrations of TCE in the intermediate zone and natural attenuation processes are expected to fiirther reduce contaminant concenfrations to MCLs over time. Continued momtoring would provide a reUable means to assess the residual concenfrations. Land Use Confrols would limit or prevent the use of groundwater and eliminate the exposure pathway.

Altemative 4 relies on the effectiveness of groimdwater exfraction and hydraulic confrol to reduce contaminant concenfrations and minimize contaminant migration over time. This altemative provides the highest degree of long-term effectiveness and permanence because it uses removal and active freatment technologies to reduce risks. Altemative 4 actively exfracts and freats the contaminated groundwater for a period of 10 years. Exfraction and GAC freatment of contaminated groundwater would have a freatment residual (spent carbon) that would be removed from the site and regenerated or disposed of off site.

5.4 Reduction of Toxicity, Mobility, and Volume

Altemative 1 relies entfrely on natural processes to reduce the contaminant concenfrations. Altematives 2 and 4 rely on natural processes to achieve reductions of concenfrations to 5 ug/L after initial in-situ freatment. Altemative 2 would also effectively reduce the toxicity, mobiUty, and volume. Altemative 4 would most effectively reduce the toxicity, mobility, and volume of contaminants in groundwater. This altemative includes freatment processes that remove the contaminants from groundwater. Altemative 4 involves exfracting the contaminated



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groundwater and adsorption ofthe contaminants onto GAC. The GAC would be a contaminated residual; however, the GAC is easily removed and contaminants desfroyed as part of the regeneration or offsite disposal process.

5.5 Short-Term Effectiveness

Altemative 1 involves no constmction of a freatment system and would result in no short-term impacts to the community, workers, or the envfronment.

Altemative 2, which involves installing a number of piezometers and chemical handling would have minimal short-term impacts during implementation.

Altemative 4, which involves installing four wells, an aboveground freatment system, and discharge line to surface discharge, would have a few short-term impacts due to constmction activities for this altemative.

Altematives 2 and 4 would achieve the RAOs in the shortest period of time (30 years) as compared to Altemative 1, which would achieve the RAOs in 50 years.

5.6 ImplementabUity

Altemative 1 is very easy to implement because no constmction of a freatment system is requfred and O&M would be minimal.

Altemative 2 is easy to implement. Conventional and readily available drilling equipment and chemicals would be used. In-situ freatment has been tested and optimized over the years. It can be considered an innovative technology and its appUcabiUty is very site-specific. Minimal performance data exist for full-scale applications, although in-situ chemical freatment has been used effectively for freatment of smaller scale "hot spot" sites.

Altemative 4 is moderately easy to implement. Conventional and readily available equipment and materials would be used. GAC freatment is a proven technology and easy to operate and maintain. Offsite regeneration, disposal, and replacement services for the spent carbon are readily available. Infrastmcture in the area and discharge monitoring would have to be addressed.

5.7 Cost

Altemative 1 has the lowest capital cost while Altemative 2 has the highest capital cost due to installation of 76 groundwater injection wells and chemical freatment. The Net Present Value (NPV) costs, excluding institutional confrols, range from $3.4 million to $3.6 milUon. Altematives 1 and 2 have the lowest NPV cost of $3.4 miUion. Altemative 4 has the highest NPV cost of $3.6 million.



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Table 3 provides a summary ofthe cost estimates for each altemative.

6.0 Land Use Controls

At sites where contaminants are left in place at levels that do not allow for unlimited use and unrestricted exposure, Land Use Confrols (LUCs) are used to ensure that the contaminants do not pose an unacceptable risk to human health or the envfronment. LUCs consist of adminisfrative, engineering and/or physical confrols. Since TCE-contaminated groundwater will remain for a time, LUCs are appropriate. The LUCs shall remain in place until the TCE concenfration in the groundwater is at a level to allow for unlimited use and unrestricted exposure. The general areas for which LUCs will be implemented are illusfrated on Figure 1.

A. Land Use Confrol Objectives:

A.1 To prohibit the use of groundwater impacted by Landfill 3, other than for envfronmental monitoring or testing, until MCLs are met for TCE and its degradation products.

A.2 To prohibit new constmction in the area above the Zone C groundwater plume without proper ventilation confrols.

B. Land Use Confrol Implementation Actions: To meet the LUC Objective the following actions and restrictions shall be implemented and maintained on the groundwater areas identified in Figure 1.

B.l. Employ Afr Force adminisfrative procedures to frack all development activity at F. E. Warren AFB. Existing procedures are included in Afr Force Instmction (AFI) 32-1021, Planning and Programming of FaciUty Projects, and work request procedures under AFI 32-1001, Operations and Management, or their equivalents as they may be amended. Afr Force Instmctions and procedures requfre coordination with and prior approval by envfronmental personnel if a proposed project is located on or near an Envfronmental Restoration Project (ERP) site. Base personnel would verify location of potentially contaminated sites via the available information (maps, documents, databases, GIS, etc.). The Afr Force will ensure that these or equivalrait instmctions, processes, and/or requfrements will be complied with for all proposed constraction activities within Zone C.

B.2 Update the Base General Plan (GP). The GP implements "zoning-like" requirements at F. E. Warren AFB. The General Plan is one of the first and main documents to be reviewed when installation personnel are proposing projects on the installation. AFI 32-7062 requires this comprehensive planning document for the estabUshment and maintenance of adminisfrative and physical confrols. The GP resides in the office of the Base Community Planner. The Afr Force will update the existing Zone C LUC map included in the GP to show the location and dimensions of the Zone C groundwater contamination as well as the LUCs, boundaries, and expected durations within 90 days of ROD Amendment signature. The LUC section includes a comprehensive Usting and map of all LUCs on the installation.


Final Zone C ROD Amendment F.E. Warren Air Force Base

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The Air Force may change the GP and agrees to notify EPA and WDEQ at least 30 days prior to a change that addresses or effects LUCs at Zone C.

B.3 The following restrictions will be incorporated into the GP and cross-referenced to this map:

B.3.1 No drilling for or use of groundwater impacted by Landfill 3, other than for environmental monitoring or testing, until the concenfration of hazardous substances in the groundwater are at such levels to allow for unrestricted use and exposure.

B.3.2 All proposed new constmction over the groimdwater plume shall be requfred to have sub-slab ventilation systems.

B.4 The Afr Force shall not modify or terminate Zone C LUCs or modify land use from the currently anticipated open space and residential use within the affected areas of Zone C without the concurrence of EPA and WDEQ. The Afr Force shall seek prior concurrence before any anticipated action that may dismpt the effectiveness ofthe LUCs.

B.4.1 For proposed land use changes that do not include fransfer ofthe property, the Afr Force will notify EPA and WDEQ at least 45 days in advance of any anticipated Base proposal inconsistent with the use restriction and assumptions described herein, any anticipated action which may dismpt the effectiveness of the LUCs, or any action which may alter or negate the need for the LUC.

B.4.2 The Afr Force will provide notice to EPA and WDEQ, consistent witii CERCLA Section 120(h) at least six (6) months prior to any fransfer or sale of land containing any portion of Zone C, including fransfers to private, state or local entities, so that EPA and WDEQ can be involved in discussions to ensure that appropriate provisions are included in the fransfer terms or conveyance documents to maintain effective LUCs. If it is not possible for the facility to notify EPA and WDEQ at least six months prior to any fransfer or sale, then the faciUty will notify EPA and WDEQ as soon as possible but no later than 60 days prior to the fransfer or sale of any property subject to LUCs. In addition to the land fransfer notice and discussion provisions above, the Afr Force further agrees to provide EPA and WDEQ with similar notice, within the same time frames, as to federal to federal transfer of property accountabiUty and adminisfrative confrol of property within Zone C. The Afr Force shall provide a copy ofthe executed deed to EPA and WDEQ. The Afr Force will provide similar notification as to leases of Zone C property, in addition to fransfers by deed.

B.5 The Afr Force will conduct periodic monitoring of the LUCs at Zone C (at least annually). The Afr Force shall provide notice to EPA and WDEQ within 10 business days of discovery of any activity that is inconsistent with the LUC requirements, objectives or confrols, or any action that may interfere with the effectiveness of tiie LUCs. The Afr Force shall include in such notice a Ust of corrective actions taken or planned to address such deficiency or failure.



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B.6 The Afr Force shall also provide annual advisory notices to the Nob Hill residents, an off base housing area, that the groundwater should not be used for domestic use (drinking, showering, or cooking). A copy of this notice shall be made part of the annual LUC monitoring report.

B.7 The Afr Force will fully comply with and be accountable for the LUCs identified herein and will timely submit to the EPA and the State an annual monitoring report (AMR) on the status ofthe LUCs, including the operation and maintenance, and monitoring LUCs, and how any LUC deficiency or inconsistent use has been addressed.

B.7.1. The LUC AMR shaU be filed in the Adminisfrative Record and Information Repository.

B.7.2. The LUC AMR is not subject to approval and/or revision by the EPA and the State and will be provided to each for informational purposes only.

B.8 The Afr Force is responsible for implementing (to the degree confrols are not afready in place), monitoring, maintaining, and enforcing the identified LUCs. If the Afr Force determines that it cannot meet specific LUC requfrements, it is understood that the remedy may be reconsidered and that additional measures may be required to ensure the protection of human health and the envfronment. The Afr Force shall obtain the concurrence of the EPA and the State prior to modifying or terminating any Land Use Confrols, Objectives, or LUC Implementation Actions.

C. Long-Term Monitoring (LTM): Long-term groundwater monitoring will be performed as part of the selected remedy to evaluate the long-term performance and effectiveness of the remedy. An LTM Plan will be developed as part ofthe remedial design and/or remedial action work plan for the Zone C remedy.

7.0 DESCRIPTION OF NEW SELECTED REMEDY

Alternative 2, in-situ treatment combined with MNA, is the technology being selected for use at Zone C to address groundwater impacts.

By combining in-situ freatment with MNA a reduction of 20 years in remediation time is predicted over MNA alone. In-situ freatment was selected instead of groundwater exfraction and freatment based upon its ability to quickly reduce the concenfrations to MCLs and because it will not bring water to the surface requiring long term monitoring.

The MNA component of this remedy uses natural attenuation processes to achieve remediation objectives with a comprehensive monitoring program. Monitoring results will be used to calculate the rate of natural attenuation occurring at Zone C, which will then be compared to contaminant removal rates estimated from previously obtained site characterization data and groundwater modeling predictions.



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The in-situ freatment component of the remedy will consist of deUvery of a chemical oxidant, such as potassium permanganate (KMn04), to contaminated media (groundwater or soil) to desfroy the contaminants or convert them to innocuous compounds commonly found in natural settings. Only the higher concenfrations (hot spot) ofthe intermediate/deep aquifer zone within the contaminated area of Zone C wiU receive in-situ freatment. The remainder of the intermediate layer and the shallow layer will be allowed to naturally attenuate. The depth ofthe intermediate zone is estimated to be 25 to 50 ft bgs (below ground surface). Additional tests will be completed during the design phase to refine the requfrements for implementing this technology at Zone C.

Long-term Monitoring (LTM) will be performed as part of the selected remedy to evaluate the long-term performance and effectiveness ofthe remedy. A LTM Plan will be developed as part of the remedial design and/or remedial action work plan for the Zone C remedy. Land use confrols as listed in Section 6 will be implemented to ensure protectiveness during the remedial process.

Table 2 provides a side-by side comparison of the September 2001 Zone C ROD remedy with the revised remedy selected by the USAF.

8.0 AFFIRMATION OF THE STATUTORY DETERMINATIONS

Considering the new information that has been collected and evaluated, the USAF believes that in-situ freatment combined with MNA will adequately protect human health and the envfronment and meet the RAOs; thereby satisfying the requfrements of CERCLA Section 121. In-situ freatment combined with MNA complies with federal and state requfrements that are applicable or relevant and appropriate to this remedial action. The chemical-specific requirement would be achieved after a period of approximately 30 years. Reduction of toxicity, mobiUty, and volume would be achieved with in-situ freatment. Minimal short-term impacts to the community, workers, or the environment would occur. The remedy utiUzes permanent solutions and altemative freatment technologies or resource recovery technologies, to the maximum extent practicable. The remedy meets tiie requfrements of 40 CFR section 300.430(f)(5).

9.0 PUBLIC PARTICIPATION

In accordance with 40 CFR Section 300.435(c)(2)(ii), the Revised Proposed Plan for Zone C was made available to the public in Febmary 2004. A notice of the availabiUty of the Revised Proposed Plan was pubUshed in the Wyoming Tribune Eagle on Febmary 26, 2004. Copies of the Revised Proposed Plan for Zone C along with all other supporting documents are available for pubUc viewing at the Laramie County Library. A public comment period was held from March 9,2004 through April 8,2004. hi addition, a pubUc meeting was held on March 23, 2004 to present the Proposed Plan to interested members of the local community. At the meeting representatives from F. E. Warren, EPA and the WDEQ answered questions regarding the remedial altematives for Zone C. A response to the comments received during this period is included in the Responsiveness Summary, which is part of this Record of Decision Amendment.



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AUTHORIZING SIGNATURES

The undersigned representatives concur with the Record of Decision for the Selected Remedy at Zone C: OUl 1, LF3, F.E. Warren Air Force Base, Wyoming.

Daniei P. L W Lieutenant General, USJ VicesConuagnder Afr Force Space Command

SLt Bcraj^ Date

b. The undersigned representatives concur with the Record of Decision for the Selected Remedy at Zone C: OUl 1, LF3, F.E. Warren Air Force Base, Wyoming.

NOV - 8 2004

Max H. Dodson Assistant Regional Adminisfrator Ecosystems Protection and Remediation U. S. Envfronmental Protection Agency - Region 8

Date

c. The undersigned representatives concur with the Record of Decision for the Selected Remedy at Zone C: OUl 1, LF3, F.E. Warren Air Force Base, Wyoming.

JohyV. Corra Dfrector, Wyominat)epartment of

invfronmental Quality

Page 12 of 16 September 2004


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10.0 REFERENCES

United States Afr Force (USAF). 1999. Final Report. Treatability Study in Support of Monitored Natural Attenuation at Landfill 3 (SiteLF3). F.E. Warren AFB, Wyoming. Prepared for Afr Force Center for Envfronmental Excellence. December.

USAF. 2000b. Final Remedial Investigation for Zone C, F.E. Wairen AFB, Cheyenne, Wyoming. May.

USAF. 2000c. Final Report. Feasibility Study for Zone C. F.E. Warren AFB, Cheyenne, Wyoming. December.

USAF. 2001a. Final Report. Recordof Decision for Zone C, Operable Unit 11, Landfill 3. F.E. Warren AFB, Wyoming. September.

USAF. 2001b. Field Activities Report. Zones B and C Groundwater Remedial Design Field Investigation. F.E. Warren AFB, Wyoming. Prepared for Afr Force Center for Envfronmental Excellence. ConfractF41624-00-D-8028, Delivery Order 037. December.

USAF. 2001d. Draft Removal Action Report. Waste Excavation from Landfill 2A/2B, Landfill 3, Landfill 5B, and Three Other Excavations Around Landfill 6. F.E. Warren AFB, Wyoming. Prepared for Afr Force Center for Envfronmental Excellence. December.

USAF. 2002. fritemal Draft Report. Zone C Field Activities Report 2, Supplemental Field Investigation. Zone C Groundwater Remedial Design. F.E. Warren AFB, Wyoming. Prepared for Afr Force Center for Envfronmental Excellence. June.

USAF. 2003. Final Report. Zone C Supplemental Feasibility Study. Zone C Groundwater F.E. Warren AFB, Wyoming. Prepared for Afr Force Center for Envfronmental Excellence. July.

USEPA, Wyoming Department of Envfronmental Quality (WDEQ), and USAF. 1991. Federal Facilities Agreement. September, plus modifications.

USEPA. 1988a. OSWER Dfrective 9355.3-01, Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA (hiterim Final). EPA/540/G-89/004. October.

USEPA. 1988b. Guidance on Remedial Actions for Contaminated Groundwater at Superfund.

USEPA. 1999. A Guide to Preparing Superfund Proposed Plans, Records of Decision, and Other Remedy Selection Decision Documents.



Cheyenne, Wyoming

RESPONSIVENESS SUMMARY FOR THE RECORD OF DECISION AMMENDMENT

ZONE C, OPERABLE UNIT 11, LANDFILL 3 REMEDIAL ACTION

INTRODUCTION

The responsiveness summary is organized into sections as foUows:

A. Overview B. Background on Community Involvement C. Summary of Comments Received D. Agency Concems

A. OVERVIEW

Zone C, Operable Unit 11 (OUll), at F. E. Warren AFB, Wyoming (FEW) consists of tiie former Landfill 3 (LF3) and the groundwater contaminated by LF3. A final Zone C Record of Decision (ROD) was signed in September 2001. The original remedy for this site was to pump the groundwater and freat it before discharge. Field testing in 2002 demonsfrated that most of the area of contamination couldn't be effectively pumped. As a result, the original remedy needed to be reconsidered. The revised remedy for cleaning up the groundwater at LF3 has changed to in-situ freatment combined with monitored natural attenuation. This revised remedy has been selected by the Afr Force and EPA, with Wyoming DEQ concurrence.

B. BACKGROUND ON COMMUNITY INVOLVEMENT

Community interest in CERCLA/IRP (InstaUation Restoration Program) activities at F. E. Warren Afr Force Base has been mixed over the years since the records search and interviews conducted for the Afr Force m September 1985. No specific individuals or organizations have been consistently involved over this period, although numerous groups and persons have been involved from time to time. There were no concerns expressed during the Zone C, OUll Remedial Investigation or Supplemental FeasibiUty Study, which were conducted prior to the pubUc comment period.

C. SUMMARY OF COMMENTS RECEIVED

The pubUc comment period on the Revised Proposed Plan for the Zone C, OUl 1 Remedial Action at F. E. Warren Air Force Base was held fix)m March 9,2004 to April 8,2004. No additional comments, written or verbal, were received during the comment period. All comments from the pubUc were received at the pubUc meeting that was held on March 23, 2004. Comments received during this meeting are summarized below:

1. Question: Community Member - How long did the plume take to develop and will it reach Crow Creek?



Cheyenne, Wyoming

Response: - It began development around the 1950's, so it's been developing for approximately 50 years. Modeling shows it's not Ukely to reach Crow Creek.

Question: Community Member - Are there any plans to develop that area and, if so, are there restrictions prohibiting the development?

Response: A new school for the city is being built near this area. The school will not be built over the plume and will have a sub-slab ventilation system. The FEW RPM has attended planning meetings and has informed all parties involved about the groundwater plume. Parities involved with the design ofthe school are fully aware ofthe additional requfrements for building in the Zone C area.

Question: Community Member - If it's (the plume) not moving and won't reach the creek, why not just do MNA? How do we know if it's safe putting potassium chemicals in the ground? Why not just let it be as that's the same cost?

Response: - The estimated remediation time for the preferred remedy is 30 years, as opposed to 50 years for MNA alone. The projected costs for these two altematives are approximately equivalent therefore; the option that results in a reduction of around 20 years would be the appropriate choice.

The risks associated with injecting potassium permanganate are mimmal given the resulting chemical reaction is fafrly well understood and the concentration ofthe injected solution is only 1% potassium permanganate, mixed with potable water.

D. AGENCY CONCERNS

No concems have been expressed by the agencies and both EPA and WDEQ concur with the selected remedy.



Cheyenne, Wyoming

Table 1: Evaluation Criteria For Superfund Remedial Altematives.

SlI'S

;§ S S 8 S

Overall Protection of Human Healtii and the Environment determines whether an altemative eliminates, reduces, or controls threats to public health and the environment through institutional controls, engineering controls, or treatment.

Compliance with ARARs evaluates whether the altemative meets federal and state environmental statutes, regulations, and other requirements that pertain to the site, or whether a waiver is justified.

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Long-Term ElTectiveness and Permanence considers the abiUty of an alternative to maintain protection of human health and environment over time.

Reduction of Toxicity, Mobility, or Volume of Contaminants Through Treatment evaluates an alternative's use of treatment to reduce the harmful effects of principal contaminants, their ability to move in the environment, and the amount of contamination present.

Short-term Effectiveness considers the length of time needed to implement an altemative and the risks the altemative poses to workers, residents, and the environment during implementation.

Implementability considers the technical and administrative feasibility of in^lementing the alternative, including factors such as the relative availability of goods and services.

Costs include estimated capital and annual operations and maintenance costs, as well as present worth cost. Present worth cost is the total cost of an altemative over time in terms of today's dollar value. Cost estimates are expected to be accurate within a range of+50 to -30 percent.

•2'i I « i S

State/Support Agency Acceptance considers whether the State agrees with or opposes the preferred alternative. WDEQ reviews and comments upon all important documents throughout the process.

•C .a

a m T3 3

^ w s 131:

Community Acceptance considers whether the local community agrees with or opposes the preferred altemative. Comments received on the Proposed Plan are an important indicator of community acceptance.

Page 1 of3 August 2004

Final Zone CROD Amendment F.E. Warren Air Force Base

Cheyenne, Wyoming

Table 2: Comparison of Remedy Components.

Remedy Component

WeU Installation

Groundwater Pumping

Groundwater Treatment

Discharge of Treated Groundwater

Estimated Remediation Time Frame Estimated Clean Up Cost

September 2001 ROD

(Pump and Treat) Wells installed throughout groundwater plume to capture contaminated groundwater.

Groundwater would be pumped from the wells to a treatment system.

Extracted Groundwater would be treated by air stripping, carbon adsorption, chemical/ultraviolet (UV) oxidation, and/or aerobic biological reactors.

Treated groundwater would be discharged to surface, re-injected in the formation, or a publicly owned treatment works.

*15 Years

• $2,434,318 (2003 NPV**)

ROD Amendment

(In-situ Treatment with MNA) Ten^jorary borings will be placed within the groundwater plume and utilized to inject potassium permanganate into the intermediate groundwater zone. Additional monitoring wells may be added for the MNA conqjonent.

No groundwater will be pumped to the surface.

Groundwater in the intermediate zone will be treated in-situ by chemical oxidation. Groimdwater in the shallow zone will be allowed to naturally attenuate. No groundwater treatment will occur ex-situ.

No groundwater will be discharged to siuface.

30 Years

$ 3,400,000 (2003 NPV)

Notes: *Data collected during a supplemental field investigation indicated that ftill plume exfraction was not feasible given existing hydrogeologic conditions. Therefore the estimated remediation time and the cleanup cost are no longer valid, hi order to provide a better comparison of costs, the NPV shown has been escalated from 2001 dollars to 2003 dollars utiUzing a factor of 5%. **NPV- Net Present Value

Page 2 of3 August 2004

Legend

Restricted Zone No Groundwater Use and

Sub-slab Ventilation Systems Required for

New Sructures

Zone Boundary

Figure 1 Zone C Land Use Controls F. E. Warren Air Force Base Zone C Record of Decision

Tables SUMMARY OF DETAILED ANALYSIS OF REMEDIAL ALTERNATIVES

Remedial Altemative

ALTERNATIVE 1 -Monitored Natural Attenuation

ALTERNATIVE 2 -In-situ Treatment and MNA

ALTERNATIVE 4 -Groundwater Extraction, Treatment and MNA

Overall Protection of Human Health and Environment

Protects human health and the environment under current conditions through natural attenuation processes. No unacceptable short-term or cross-media impacts are expected. Currently protective because the RI found no current exposure and land use controls will prevent future exposure.

Protects human health and the environment under current conditions through In-situ chemical treatment and natural attenuation processes. No unacceptable short-term or cross-media impacts are expected.

Protects human health and the environment under current conditions through removal and treatment of the contaminated groundwater and natural attenuation processes. No unacceptable short-term or cross-media impacts are expected.

Compliance with Potential ARARs

Complies with all potential chemical-, action-, and location-specific ARARs. No discharge permits are needed for this alternative.

Complies with all potential chemical-, action-, and location-specific ARARs. Any soil spoils generated from installation ofthe piezometers will remain on site in accordance with potential ARARs.

Complies with all potential chemical-, action-, and location-specific ARARs. Any soil spoils generated from installation ofthe wells will remain on site in accordance with potential ARARs. Compliance with the substantive requirements of an NPDES discharge permit is needed for this alternative, which may require additional treatment system components and monitoring.

Long-Term Effectiveness and Permanence

Natural processes will reduce contaminant levels in groundwater to MCLs over time. Continued monitoring provides a reliable means to assess the residual concentrations and manage the risk posed by the residual. Land use controls would limit or prevent use of groundwater. No untreated residual contamination would be produced by this treatment process. Minimal operation and maintenance of wells and groundwater sampling are required. In-situ treatment will reduce contaminant levels in groundwater. Continued monitoring provides a reliable means to assess the residual concentrations and manage the risk posed by the residual. Land use controls would limit or prevent use of groundwater. No untreated residual contamination would be produced by this treatment process. Minimal operation and maintenance of piezometers and groundwater sampling are required.

Ex-sItu treatment will reduce contaminant levels in groundwater. Continued monitoring provides a reliable means to assess the treatment effectiveness. Land use controls would limit or prevent use of groundwater. Activated carbon would retain the TCE, however, it would be shipped off site for destruction through regeneration.

Reduction of Toxicity, IVIobility, and Volume through Treatment

Toxicity, mobility, and volume of TCE are reduced over time from natural attenuation of contaminants in groundwater. TCE levels are reduced to MCLs. No residuals present in groundwater at completion. Irreversible.

Toxicity of higher TCE concentrations is reduced in a shorter time. Reduction in TCE volume over time. Potential treatment residual (KMn04) in groundwater. Treatment is irreversible.

Toxicity, mobility, and volume of TCE are reduced over time from ex-situ treatment of groundwater. TCE adsorbed to activated carbon. TCE levels in groundwater reduced to MCLs. Treatment is irreversible.

Short-Term Effectiveness No additional risk to site workers and the environment because there is no construction of a treatment system. No Increased risk to workers, the community, or the environment during implementation. Time to achieve MCLs within Zone C is estimated to be approximately 50 years.

Minimal additional risk to site workers and the environment during installation of piezometers and chemical injection. Excavated material will remain on site; therefore, the community does not incur incremental risk associated with traffic and offsite disposal. No increased risk to workers, the community, or the environment during Implementation. Time to achieve MCLs is estimated to be approximately 30 years. Moderate additional risk to site workers and the environment during construction. Excavated material will remain on site; therefore, the community does not incur incremental risk associated with traffic and offsite disposal. No increased risk to workers, the community, or the environment during implementation. Transport of spent carbon vessel to offsite regeneration facility would pose minimal risk to community. Time to achieve MCLs is estimated to be approximately 30 years.

Implementability Easy to Implement. Should not create schedule delays. Passive prbcess that does not require removal, aboveground treatment, or TSD services. Monitoring the effectiveness Is simple. FEW administrative requirements include modifying the General Plan.

Easy to implement. Should not create schedule delays. An innovative technology implementability is very site specific. Field testing required conventional drilling techniques would be used. Chemical is readily available and easy to apply. In-situ treatment that does not require removal, aboveground treatment or TSD services. Monitoring the effectiveness is simple. FEW administrative requirements include modifying the General Plan. Moderately easy to implement. Carbon adsorption is a proven and reliable technology. Equipment (carbon vessels, pumps) and carbon regeneration services are readily available. Conventional construction techniques would be used and should be easy to construct and not create schedule delays. Monitoring the effectiveness is simple, but adds monitoring for compliance with the requirements ofthe NPDES program. Multiple suppliers of carbon equipment are available. Competitive bids can be obtained. Administrative requirements include modifying the General Plan.

Approximate Cost (million $)

Capital $0

O&M $6.0

Net Present Value $3.4

Capital $0.6

O&M $3.9


Capital $0.3

O&M $4.6


Page 3 of 3 September 2004