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EPA Superfund Record of DecisionEPA/ROD/R03-04/607 2004 EPA Superfund Record of Decision: ABERDEEN...

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  • EPA/ROD/R03-04/6072004

    EPA Superfund

    Record of Decision:

    ABERDEEN PROVING GROUND (EDGEWOOD AREA)EPA ID: MD2210020036OU 21EDGEWOOD, MD09/30/2004

  • GRACES QUARTERS (OPERABLE UNIT A) PRIMARY TEST AREA RECORD OF DECISION Final September 2004

    U.S. Army Garrison Aberdeen Proving Ground, Edgewood, Maryland

    DISTRIBUTION RESTRICTION STATEMENT APPROVED FOR PUBLIC RELEASE:

    DISTRIBUTION IS UNLIMITED

    6143-A-6

  • RECORD OF DECISION

    ABERDEEN PROVING GROUND, EDGEWOOD GRACES QUARTERS (OPERABLE UNIT A: GROUNDWATER)

    PRIMARY TEST AREA

    FINAL

    Directorate of Safety, Health and Environment Environmental Conservation and Restoration Division

    Installation Restoration Program U.S. Army Garrison Aberdeen Proving Ground, Edgewood, Maryland

    September 2004

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page ii of vi

    TABLE OF CONTENTS Section Page TITLE PAGE ................................................................................................................................................................................ i LIST OF FIGURES .....................................................................................................................................................................ii LIST OF TABLES .......................................................................................................................................................................ii LIST OF ACRONYMS AND ABBREVIATIONS ..............................................................................................................iv 1 DECLARATION .............................................................................................................................................................. 1 1.1 SITE NAME AND LOCATION ....................................................................................................................1 1.2 STATEMENT OF BASIS AND PURPOSE ................................................................................................1 1.3 ASSESSMENT OF THE SITE .......................................................................................................................1 1.4 DESCRIPTION OF THE SELECTED REMEDIES ..................................................................................1 1.5 STATUTORY DETERMINATIONS ............................................................................................................2 1.6 DATA CERTIFICATION CHECKLIST ......................................................................................................2 2 THE DECISION SUMMARY ...................................................................................................................................... 4 2.1 SITE NAME, LOCATION AND DESCRIPTION .....................................................................................4 2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES ...........................................................................6 2.3 COMMUNITY PARTICIPATION ................................................................................................................9 2.4 SCOPE AND ROLE OF THE OPERABLE UNIT ...................................................................................10 2.5 SITE AND OPERABLE UNIT CHARACTERISTICS ...........................................................................11 2.6 CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES .........................................21 2.7 SUMMARY OF SITE RISKS .......................................................................................................................21 2.7.1 Human Health Risk Assessment ........................................................................................................................21 2.7.2 Ecological Risk Assessment ...............................................................................................................................24 2.8 REMEDIAL ACTION OBJECTIVES ........................................................................................................25 2.9 DESCRIPTION OF ALTERNATIVES ......................................................................................................26 2.9.1 Alternative 1: No Action .....................................................................................................................................27 2.9.2 Alternative 2: Institutional Controls/LTM .......................................................................................................28 2.9.3 Alternative 3: Vitamin B12-catalyzed reductive dehalogenation in areas greaterthan 1,000 µg/L; MNA at all other locations .............................................................................................................................28 2.9.4 Alternative 4: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L; pump-and-treat at all other locations ..........................................................................................................29 2.9.5 Alternative 5: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L in the surficial aquifer; pump-and-treat at all other locations ...............................................................29 2.9.6 Alternative 6: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 100 µg/L (both aquifers); MNA at all other locations ................................................................................................30 2.9.7 Alternative 7: Pump-and-Treat at all locations .............................................................................................31 2.9.8 Alternative 8: Pump-and-treat in areas greater than 1,000 µg/L (both aquifers); LTM at all other locations ............................................................................................................................................................31

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page iii of vi 2.9.9 Alternative 9: ERH in areas greater than 1,000 µg/L in the surficial aquifer; pump-and-treat at all other locations ..................................................................................................................................................32 2.10 COMPARATIVE ANALYSIS OF ALTERNATIVES ................................................................................33

    2.10.1 Threshold Criteria ................................................................................................................................................33 2.10.2 Primary Balancing Criteria ...........................................................................................................................35 2.10.3 Modifying Criteria ...............................................................................................................................................38

    2.11 SELECTED REMEDY 39 2.12 STATUTORY DETERMINATIONS 43

    2.12.1 Protection of Human Health and the Environment ........................................................................................44 2.12.2 Compliance with ARARs Requirements ............................................................................................................44 2.12.3 Cost Effectiveness .................................................................................................................................................44 2.12.4 Utilization of Permanent Solutions and Alternative Treatment Technologies (or Resource Recovery Technologies) to the Maximum Extent Practicable ...................................................................................46 2.12.5 Preference for Treatment as a Principal Element ...........................................................................................46 2.12. 6 Five-year Review Requirements .......................................................................................................................46

    2.13 DOCUMENTATION OF SIGNIFICANT CHANGES FROM PREFERRED ALTERNATIVE OF PROPOSED PLAN ........................................................................................................................................................46 3 RESPONSIVENESS SUMMARY .............................................................................................................................47 3.1 OVERVIEW ...............................................................................................................................................................47 3.2 BACKGROUND ON COMMUNITY INVOLVEMENT .................................................................................47 3.3 SUMMARY OF COMMENTS RECEIVED DURING THE PUBLIC COMMENT PERIOD AND AGENCY RESPONSES ......................................................................................................................................................48 4 REFERENCES ................................................................................................................................................................ 55

    LIST OF FIGURES

    Figure 1. Graces Quarters location map .....................................................................................................................................5 Figure 2. Topographic and site location of the Primary Test Area, Graces Quarters (APG, 1999b) ...............................8 Figure 3. Primary Test Area, Graces Quarters (APG, 2002) ................................................................................................12 Figure 4. Graces Quarters Primary Test Area Conceptual Model of the Aquifer System (APG, 2002) .......................13 Figure 5. Graces Quarters Primary Test Area, Groundwater flow in the surficial aquifer (APG, 2002) ......................14 Figure 6. Graces Quarters Primary Test Area, Groundwater flow in the middle aquifer (APG, 2002) ........................15 Figure 7. Conceptual groundwater discharge areas, Graces Quarters (APG, 2002)..........................................................16 Figure 8. Isopleth map showing the horizontal extent of the total VOC plume in the surficial aquifer beneath the Primary Test Area, Graces Quarters (APG, 2001c) ...........................................................................................19 Figure 9. Isopleth map showing the horizontal extent of the total VOC plume in the middle aquifer beneath the Primary Test Area, Graces Quarters (APG, 2001c) ...........................................................................................20 Figure 10. Conceptual diagram of a recirculation well ..........................................................................................................41

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page iv of vi

    LIST OF TABLES Table 1. Areas and volumes of contaminated groundwater in Graces Quarters Operable Unit A-Primary Test Area (APG. 1999) ..............................................................................................................................................................18 Table 2. Primary constituents contributing to carcinogenic risk or noncarcinogenic hazard under future military multi-use scenario (APG. 1998a) ..........................................................................................................................23 Table 3. COC maximum concentrations. MCLs. and RAO concentrations (APG. 2004) ...............................................26 Table 4. Comparative Analysis of Alternatives ......................................................................................................................34 Table 5. Alternative 3 cost summary ........................................................................................................................................40 Table 6. Action-Specific Applicable or Relevant and Appropriate Requirements ...........................................................45

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page v of vi

    LIST OF ACRONYMS AND ABBREVIATIONS

    APG Aberdeen Proving Ground

    APGSCC Aberdeen Proving Ground Superfund Citizens Coalition

    ARAR Applicable or relevant and appropriate requirement

    bgs Below Ground Surface

    BRA Baseline Risk Assessment

    CA Chloroethane

    CAHs Chlorinated Aliphatic Hydrocarbons

    CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

    COCs Constituents of Concern

    COPCs Constituents of Potential Concern

    CS Ortho-chlorobenzolmalonoitrile

    CWM Chemical Warfare Materiel

    DSERTS Defense System Environmental Restoration Tracking System

    DNAPL Dense Non-Aqueous Phase Liquid

    DOD Department of Defense

    EM Electromagnetic Conductivity

    EPA U.S. Environmental Protection Agency

    ERA Ecological Risk Assessment

    ERH Electrical Resistance Heating

    °C Degree Celsius

    FFA Federal Facilities Agreement

    FS Feasibility Study

    ft Feet

    GB Isopropylmethylphosphonofluoridate

    GD Pinacolylmethylphosphonofluoridate

    GMS Groundwater Modeling System

    GPR Ground-Penetrating Radar

    HD 2,2'-dichlorodiethyl Sulfide (mustard gas)

    HEAST Health Effects Assessment Summary Tables

    HI Hazard Index

    IRIS Integrated Risk information System

    kW-hr Kilowatt Hour

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page vi of vi

    LIST OF ACRONYMS AND ABBREVIATIONS (cont'd)

    LECR Lifetime Excess Cancer Risk

    LTM Long-term Monitoring

    LUC Land Use Controls

    MCL Maximum Concentration Level

    SIDE Maryland Department of the Environment

    ULNA Monitored Natural Attenuation

    NCP National Contingency Plan

    NGVD National Geodetic Vertical Datum

    NPDES National Pollutant Discharge Elimination System

    NPL National Priorities List

    O&M Operation and Maintenance

    ppb Part Per Billion

    PVC Polyvinyl Chloride

    RA Risk Assessment

    RAB Restoration Advisory Board

    RAGS Risk Assessment Guidance for Superfund

    RAO Remedial action objective

    RBC Risk Based Concentration

    RCRA Resource Conservation and Recovery Act

    RfDs Reference Doses

    RI Remedial Investigation

    ROD Record of Decision

    SARA Superfund Amendments and Reauthorization Act

    SFs Slope Factors

    µg/L Microgram per Liter

    USGS U.S. Geological Survey

    UXO Unexploded Ordnance

    VOC Volatile Organic Compound

    VX o-ethyl-s-(2-diisopropylaminoethyl) methylphosphonothioate

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 1 of 56 1 DECLARATION 1.1 SITE NAME AND LOCATION Graces Quarters, Operable Unit A (Groundwater), Primary Test Area. Aberdeen Proving Ground (APG), Edgewood, Maryland (EPA Superfund Site ID number MD2210020036). 1.2 STATEMENT OF BASIS AND PURPOSE This Record of Decision (ROD) presents the selected remedy for Operable Unit A; Groundwater at Graces Quarters, Primary Test Area, APG, Edgewood, Maryland. The remedial action is chosen in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), as amended by the Superfund Amendments and Reauthorization Act (SARA), and to the extent practicable, the National Oil and Hazardous Substances Pollution Contingency Plan (NCP). The information supporting the decisions on the selected remedy is contained in the administrative record for APG. The U.S. Department of the Army (the site owner) is the lead agency for this action with coordination from the State of Maryland Department of the Environment (MDE); the U.S. Environmental Protection Agency (EPA) is the lead regulatory agency and together the Army and EPA issue this ROD. 1.3 ASSESSMENT OF THE SITE Actual or threatened releases of hazardous substances from this site, if not addressed by implementing the response action selected in this ROD, may present an imminent and substantial endangerment to public health, welfare, or the environment. 1.4 DESCRIPTION OF THE SELECTED REMEDIES Groundwater beneath the Primary Test Area at Graces Quarters has been impacted by chlorinated solvents, which were used during activities conducted formerly at the site, including development and testing of chemical agent munitions. A groundwater plume of chlorinated volatile organic compounds (VOCs) with localized concentrations of 1,1,2,2-tetrachloroethane, carbon tetrachloride, and trichloroethene greater than 1,000 micrograms per liter (µg/L), exists beneath a portion of the Site, posing a potential threat to human health and the environment. The selected remedial action includes treatment technologies to eliminate principal threats and stimulation of natural attenuation to address non-principal threats, as well as institutional controls (land use restrictions) that were already in place at the site. The major components of the selected remedial action are as follows: • In-situ treatment of chlorinated VOCs in areas having concentrations greater than 1,000 µg/L of 1,1,2,2-

    tetrachloroethane, carbon tetrachloride, and trichloroethene using injection of vitamin B12 amendment into the aquifer through recirculation wells to stimulate catalyzed reductive dehalogenation, followed by Monitored Natural Attenuation (MNA);

    • MNA at all other locations containing low levels of chlorinated VOCs; and,

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 2 of 56 • Land use controls on the use of groundwater in the surficial and middle aquifers until MCLs are met. 1.5 STATUTORY DETERMLNATIONS This remedy attains the mandates of CERCLA Section 121 and, to the extent practical the NCP. The selected remedy is protective of human health and the environment, complies with Federal and State requirements that are legally applicable or relevant and appropriate to the remedial action, is cost effective, and utilizes permanent solutions and alternative treatment technologies to the maximum extent practicable. This remedy also satisfies the statutory preference for treatment as a principal element of the remedy (i.e., reduces the toxicity, mobility, or volume of hazardous substances, pollutants, or contaminants through treatment). Because this remedy will not result in hazardous substances, pollutants, or contaminants remaining on-site above levels that allow for unlimited use and unrestricted exposure, but will take more than five years to attain remedial action objectives (RAOs) and cleanup levels, a policy review may be conducted within five years of construction completion for the site to ensure that the remedy is, or will be, protective of human health and the environment. 1.6 DATA CERTIFICATION CHECKLIST The following information is included in the Decision Summary section of this ROD. Additional information can be found in the Administrative Record file for this site. • Constituents of concern (COCs) and their respective concentrations. • Baseline risk represented by the COCs. • Cleanup levels established for COCs and the basis for these levels. • Current and reasonably anticipated future land use assumptions and current and potential future beneficial uses

    of groundwater used in the baseline risk assessment (BRA) and ROD. • Potential land and groundwater use available at the site as a result of the selected remedy. • Estimated capital, annual operation and maintenance (O&M), and total present worth costs, discount rate, and

    the number of years over which the remedy cost estimates are projected. • Key factor(s) that led to selecting the remedy (i.e., a description of how the selected remedy provides the best

    balance of tradeoffs with respect to the balancing and modifying criteria, highlighting criteria key to the decision).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 3 of 56

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 4 of 56 2 THE DECISION SUMMARY 2.1 SITE NAME, LOCATION AND DESCRIPTION APG is a 72,500-acre Army installation located in southern Harford County and southeastern Baltimore County, Maryland, on the western shore of the Upper Chesapeake Bay. Graces Quarters is a peninsula located approximately five miles southeast of White Marsh, Maryland, and two miles southeast of Chase, Maryland, as shown in Figure 1. Access to the property is controlled by chain link fences, a locked gate, and patrols by military police. Paved and gravel roads are present on the peninsula. The only current permanent large structure is an emergency radio transmitter and tower originally constructed by the Federal Emergency Management Agency. Graces Quarters covers 414 acres, of which approximately 151 acres (36 percent) are classified as wetlands. The land mass consists of tidal and non-tidal wetlands, open fields, and wooded areas. Maximum elevation is approximately 40 feet (ft) above National Geodetic Vertical Datum (NGVD). Graces Quarters is bordered to the east and south by the Chesapeake Bay; to the west by Gunpowder Falls State Park, and residential areas; and to the north by the towns of Edgewood, Joppa, Magnolia, and Aberdeen. The Bush River divides APG into the Edgewood Area to the west of the river and the Aberdeen Area to the east. Carroll Island and Graces Quarters (Figure 1) are located in the Edgewood Area; both were listed on the NPL (CERCLIS# MD2210020036) in 1990. The Primary Test Area was identified as Site 5 followed by Defense System Environmental Restoration Tracking System (DSERTS) number EAGQ02-D, while the impacted groundwater below the site was evaluated as Operable Unit A in the Remedial Investigation (RI) of Graces Quarters (APG, 1998a). Chlorinated VOCs -- carbon tetrachloride, 1,1,2,2-tetrachloroethene, trichloroethene, chloroform and tetrachloroethene -- are the major contaminants that potentially pose a threat to human health and the environment. Chemical Warfare Materiel (CWM), unexploded ordnance (UXO) and other hazardous substances, may also be encountered at the Primary Test Area and will be managed in accordance with the previously submitted and approved ROD (APG, 2001a) for Operable Unit B (CWM). Remedial Action is required for this site because the potential exists for future exposure of human receptors. Additionally, there is potential for transport of contaminants to wetlands and the Chesapeake Bay. The Army is the Lead Agency which provides the funding for this Remedial Action. This document is issued by the Army (the site owner and lead agency) and the EPA (the lead regulatory agency for site activities), and in coordination with MDE (the State environmental agency).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 5 of 56

    Figure 1. Graces Quarters location map.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 6 of 56 2.2 SITE HISTORY AND ENFORCEMENT ACTIVITIES

    Graces Quarters was acquired as U.S. Army property in 1918 as part of the original Edgewood Arsenal (AEHA, 1989). Little documentation is available on the use of Graces Quarters prior to the 1940's, but it does not appear that there was any Army activity at the site until the 1940's. Records of testing of CWM at Graces Quarters are only available for the period between 1964 and 1971; however, it is known that testing was conducted before this time. Outdoor testing of lethal CWM ceased in 1969. Open-air testing of simulants and non-lethal incapacitants continued at Graces Quarters until 1971, at which time all open-air testing of CWM ceased at the site. Detailed descriptions of the history and land use of Graces Quarters are presented in the Resource Conservation and Recovery Act (RCRA) Facility Assessment (AEHA, 1989) and the RI Report (1998a). Graces Quarters is expected to remain under military authority with limited military training activities currently being conducted. CERCLA activities at APG are being conducted under a Federal Facilities Agreement (FFA) with EPA signed in March 1990. The bulk of the CWM testing took place at the Primary Test Area, which is approximately 22 acres and is classified predominantly as uplands. No structures are present at this site, and it is currently an open, grassy area. The site has gently sloping relief, ranging between 5 to 20 ft above NGVD, and slopes toward the southwest. The Primary Test Area is located near the middle of the Graces Quarters peninsula and is bounded to the east by the Gunpowder River and the Northern Perimeter Dump; to the south by the Southern/Southwest Perimeter Dumps; to the west by the Dugway Proving Ground Test Site and a north-south access road; and to the north by the east-west access road across Graces Quarters (Figure 2). A small amount of testing was also conducted in the small wooded area southwest of the Primary Test Area. The Mustard Gas (2,2'-dichlorodiethyl sulfide or HD) Test Annuli located north of the Primary Test Area were used in decontamination studies with HD, o-ethyl-s- (2-diisopropylaminoethyl)-methylphosphonothioate (VX), and fuming nitric acid. Surveillance testing was conducted in the small area southwest of the Graces Quarters Disposal Area. A small amount of testing was also conducted in the Graces Quarters Disposal Area. Compounds used at Graces Quarters included HD, VX, ortho-chlorobenzolmalonoitrile (CS), isopropylmethylphosphonofluoride (GB), pinacolylmethylphosphonofluoridate (GD), and chlorinated solvents. Wastes from testing activities were disposed of by dumping or burial, primarily at Graces Quarters Disposal Area. Based on historical uses of Graces Quarters, the principal contaminants that could be present include CWM, explosives, and associated degradation products (most likely via hydrolysis reaction). In addition, other contaminants that could potentially be present include VOCs, semi-VOCs, pesticides/polychlorinated biphenyls, and inorganics. During site operations, use of the decontaminating agent DANC (Decontaminating Agent Non-Corrosive) likely resulted in releases to the subsurface of 1,1,2,2 tetrachlorethane and other VOCs. There exists the potential that some wastes associated with testing and support activities may not have been located/identified, due to the difficulty of detecting these wastes with existing technology. Based on the 1998 RI, the VOC contaminated groundwater beneath the Primary Test Area is designated as Operable Unit A, whereas all CWM and other hazardous substances that have not been located and/or remediated at Graces Quarters are designated as Operable Unit B (APG, 1998a). A ROD has been prepared and approved to address combined Operable Units B at Graces Quarters and Carroll Island, both of which are similar in the types of contaminants, environment, and potential remedial actions (APG, 2001a). All of the land and shoreline areas are included

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 7 of 56 within the Operable Unit B of Carroll Island and Graces Quarters, and the Selected Remedy -- Public Access Controls, Land Use Restrictions, and Erosion Controls -- was chosen as the highest level of protection of human health and the environment. A public meeting was held on May 11, 2000 to formally present the Proposed Plan (APG, 2000) for Operable Unit B at Graces Quarters and Carroll Island. EPA and MDE concurred with the Army's preferred alternative, which then became the selected remedy in the 2001 ROD (APG, 2001a). The community also agreed with the selected remedy. Because the selected remedy for Operable Unit B will allow CWM (if any), hazardous substances, and pollutants to remain on site, remedy reviews will be performed every five years, as required by the NCP (APG, 2001a).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 8 of 56 Figure 2. Topographic and site location of the Primary Test Area, Graces Quarters (APG, 1999b).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 9 of 56 2.3 COMMUNITY PARTICIPATION Community relations activities that have taken place at APG to date include monthly Restoration Advisory Board (RAB) meetings, APG Superfund Citizens Coalition (APGSCC) meetings, public meetings and site tours, as well as press releases, and public access to the APG website. Administrative Record – Consistent with requirements of CERCLA section 113(k), an Administrative Record containing information associated with CERCLA cleanup activities at APG is available to the public. The locations, contact information and hours of operation for the administrative record file are as follows: Harford County Library – Aberdeen Branch 21 Franklin Street Aberdeen, MD 21001 (410) 273-5608 Hours: Mon., Tues., Thur. - 10 a.m. to 8 p.m. Wed. - 1 p.m. to 8 p.m. Fri., Sat. - 10 a.m. to 5 p.m. Sun. - 1 p.m. to 5 p.m. (Oct-May only) Hanford County Library – Edgewood Branch 2205 Hanson Road Edgewood, MD 21040 (410) 612-1600 Hours: Mon., Tues., Thur. - 10 a.m. to 8 p.m. Wed. - 1 p.m. to 8 p.m. Fri., Sat. - 10 a.m. to 5 p.m. Sun. - closed Kent County – Washington College Miller Library Chestertown, MD 21620 (410) 778-2800 Hours: Mon. to Fri. - 8 a.m. to 12 a.m. Sat. - 10 a.m. to 10 p.m. Sun. - 11:45 a.m. to 12 a.m. Baltimore County Public Library - Essex Branch 1110 Eastern Boulevard Essex, Maryland 21221 (410) 887-0295 Hours: Mon. to Thur. - 10 a.m. to 9 p.m. Fri., Sat. - 10 a.m. to 5:30 p.m. Sun. - closed Mailing List – A mailing list of all interested parties in the community is maintained by APG and updated regularly. Fact Sheet – A fact sheet describing the status of the Installation Restoration Program was last distributed to the mailing list addressees on April 21, 2004.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 10 of 56 Proposed Plan – The Proposed Plan regarding this remedial action was made available to the public for their comments. The Feasibility Study (FS) and Proposed Plan for Graces Quarters Operable Unit A (Groundwater) were made available to the public in February 2004 and April 2004, respectively. They can be found in the Administrative Record file and the information repository maintained at the EPA Docket Room in Region III and the public libraries in Harford County, Kent County, and Baltimore County. The notice of the availability of the Proposed Plan was published in newspapers, including The Aegis and The Cecil Whig on April 14, 2004; and The Avenue, The East County Times, and The Kent County News on April 15, 2004. A public meeting was held on April 27, 2004 at the Marshy Point Nature Center, 7130 Marshy Point Road, Baltimore, MD 21220 to present the Proposed Plan. At this meeting, representatives from the Army, EPA and MDE answered questions about problems at the site and the remedial alternatives. The Army and EPA also used this meeting to solicit a wider cross-section of community input on the reasonably anticipated future land use and potential water resources at the site. Response to the comments received during this period is included in the Responsiveness Summary, which is a part of this ROD. 2.4 SCOPE AND ROLE OF THE OPERABLE UNIT An Operable Unit is defined by the NCP as "a discrete action that comprises an incremental step toward comprehensively mitigating site problems". Based on the complexity of the problems (i.e., distinctive nature of contaminants in the soil and the groundwater, and different pathways of exposure) two Operable Units associated with Graces Quarters were established for the purpose of managing the site-wide response action (APG, 1998a). • Operable Unit A: Groundwater associated with the Primary Test Area containing primarily chlorinated VOCs. • Operable Unit B: Entire areas of Graces Quarters addressing all CWM and hazardous substances. As previously mentioned, Operable Unit B of Graces Quarters was addressed together with Operable Unit B of Carroll Island due to their similarity in the types of contaminants, environment, and potential remedial actions. A separate ROD was prepared and approved, which addresses all CWM and hazardous substances that have not been located at both Graces Quarters and Carroll Island (APG, 2001a). This ROD addresses only Operable Unit A of Graces Quarters as the concentrations of chlorinated solvents in the groundwater, primarily 1,1,2,2-tetrachloroethane and carbon tetrachloride in the vicinity of the Primary Test Area, warrant remediation. Based on the concentrations of total VOC's, residual dense non-aqueous phase liquid (DNAPL) may exist in localized areas beneath the Primary Test Area. This suspected DNAPL residual is considered to be a principal threat to human health and the environment. A FS has been prepared to evaluate remedial alternatives addressing the contaminated groundwater (APG, 2004). The selected remedy for Operable Unit A is intended to prevent both human exposures to COCs, and to prevent the migration of COCs from the Primary Test Area at Graces Quarters. The selected remedy for Operable Unit A is designed to destroy the principal threat wastes via in-situ

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 11 of 56 treatment, address the diluted plume via natural attenuation, and restore the aquifers' potential for beneficial use in years to come. 2.5 SITE AND OPERABLE UNIT CHARACTERISTICS The surficial sediments at Graces Quarters are primarily those of the Patapsco Formation, as described and discussed in the RI Report (APG, 1998a). The clay facies of the Patapsco Formation outcrop mainly in the northeastern part of the peninsula (Bennett and Meyer, 1952), and generally are topographically higher than the rest of Graces Quarters. The sand facies of the Patapsco Formation outcrop in the topographically lower areas of Graces Quarters, and directly underlie the Primary Test Area. In the Primary Test Area (Figure 3), a surficial unconfined aquifer composed of yellow, clean, fine-to-medium quartz sand with thin layers of silty clay underlies the site. This surficial aquifer extends to depths approximately 40 to 50 ft below ground surface (bgs) where it is underlain by a discontinuous confining layer that is composed of silty clay. A semi -confined sand unit, termed the middle aquifer, is present from approximately 40 to 80 ft bgs. The middle aquifer predominantly consists of yellow, clean, fine-to-medium quartz sand with thin stringers of silty clay. Beneath the middle aquifer is a continuous clay aquitard. Figure 4 provides a conceptual model of the affected aquifer system beneath the Primary Test Area. Groundwater flow in the surficial aquifer is predominantly south and southwest toward the wetland areas located in the southern portion of the peninsula (Figure 5). Surficial groundwater likely discharges to these wetland areas and the surrounding water bodies, and locally recharges the middle aquifer where the middle confining layer is absent. Groundwater in the middle aquifer flows radially away from the holes in the confining layer. It is probable that groundwater in the middle aquifer discharges to the Gunpowder River or Saltpeter Creek (Figure 6). However, because the middle aquifer is deeper and separated from the surface water bodies by clays and silts, it likely takes a longer time to do so than water from the overlaying surficial aquifer. A conceptual figure showing the likely discharge area for groundwater from these aquifers is provided as Figure 7. Further detailed discussion of the hydrogeology is presented in the Graces Quarters RI (APG, 1998a), the Additional Groundwater Investigations Data Report (APG, 1998b), and the Conceptual Site Model (APG, 2001c). Groundwater in the surficial and middle aquifer at the Primary Test Area is contaminated with VOCs, particularly chlorinated aliphatic hydrocarbons (CAHs). The most frequently detected contaminants include 1,1,2,2-tetrachloroethane, carbon tetrachloride, tetrachloroethee, chloroform, and trichloroethene. The contaminants have formed a plume of contaminated groundwater originating in the surficial aquifer, migrating to the south, and into the middle aquifer.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 12 of 56

    Figure 3. Primary Test Area, Graces Quarters (APG, 2002).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 13 of 56 F

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  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 14 of 56

    Figure 5. Graces Quarters Primary Test Area, Groundwater flow in the surficial aquifer (APG, 2002).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 15 of 56 Figure 6. Graces Quarters Primary Test Area, Groundwater flow in the middle aquifer (APG, 2002).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 16 of 56

    Figure 7. Conceptual groundwater discharge areas, Graces Quarters (APG, 2002).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 17 of 56 Groundwater samples were collected from approximately 46 geoprobes, approximately 10 borings, and approximately 42 monitoring wells. Geoprobes are temporary sampling points and are removed after samples have been collected. The compound detected at the highest concentration was 1,1.2.2-tetrachloroethane at 181.000 µg/L in a groundwater sample from a geoprobe. Confirmed peak detections (repeated detections in permanent wells) of 1.1.2.2-tetrachloroethane are much lower and are on the order of 2,000 to 3,000 µg/L. Carbon tetrachloride, trichloroethene and chloroform were detected in the 1,000 to 3,000 µg/L range, although the majority of the positive detections were below 1,000 µg/L. Tetrachloroethene was detected at lower concentrations than the previously mentioned constituents. There are no known specific contaminant source areas at Graces Quarters. It is likely that the contaminants were introduced to the surficial aquifer as multiple non-point source releases of solvents used during the testing of CWM. The contaminants have formed a plume of contaminated groundwater originating in the surficial aquifer and migrating to the south and into the middle aquifer through pathways in the confining layer. Based on the distribution of contaminants and detected concentrations, it is believed that residual DNAPL may exis t in the surficial aquifer in the area where concentrations exceed 1,000 µg/L total VOCs. This presumption is consistent with the EPA current guidance suggesting DNAPL should be considered as the principal threat and be suspected at areas where the concentration levels of individual constituents exceed one or more percent of their effective solubilities. The EPA guidance also advises using treatment to destroy principal threats and to contain or use engineering methods to address non-principal threats (e.g., dilute VOC plume). In 1999 and 2000, pilot scale testing was conducted to assess the efficacy of injecting a vitamin B12 amendment into the subsurface via recirculation wells. This test demonstrated that this technology effectively degraded the contaminants in the aquifer, rapidly reducing the concentrations within an 80 ft radius of the test well. Concentrations did not rebound following shut down of the system indicating the treatment is effective at remediating potential residual, dense non-aqueous phase solvents. During operation of the system, reducing conditions created in the aquifer temporarily mobilizes naturally occurring arsenic in the formation. Concerns regarding this condition raised by EPA were addressed in a 2004 technical memorandum demonstrating that this is a temporary and reversable condition. It is believed that contamination in the middle aquifer has been transported as dissolved phase only and that no residual DNAPL exists in the middle aquifer -- total VOC concentrations in the middle aquifer are typically less than 1,000 µg/L although peak concentrations exceed 3,000 µg/L. Table 1 presents the areal extent and volume of groundwater contamination in the surficial and middle aquifers at various concentration ranges. These estimates are based on calculations using the Groundwater Modeling System (GMS) software, present understanding of contaminant distribution, and a porosity of 20 percent. Figures 8 and 9 show the areal extent of the total VOC plumes in the surficial and middle aquifers, respectively.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 18 of 56 Table 1. Areas and volumes of contaminated groundwater in Graces Quarters Operable Unit A -Primary Test Area (APG, 1999).

    Area (square feet, ft2)

    Volume (gallons) Concentration Range

    (Total VOCs) Surficial Aquifer

    Middle Aquifer

    Surficial Aquifer Middle Aquifer

    >1,000 µg/L 60,200 14,500 2,230,000 524,000

    100 – 1,000 µg/L 183,000 145,000 4,470,000 3,510,000

    5 - 100 µg/L 546,000 1,150,000 16,700,000 35,500,000

    Bi-annual monitoring of the plumes has been occurring since 1998. Sampling through 2002 suggests that: • The plume in the surficial aquifer remains relatively stable but may be extending into the marshes south of the

    Primary Test Area; • Groundwater modeling suggests that although discharge to the surface water bodies surrounding Graces

    Quarters may occur in the future, it will not occur for a considerable amount of time; and • The plume in the middle aquifer also appears to be fairly stable.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 19 of 56 Figure 8. Isopleth map showing the horizontal extent of the total VOC plume in the surficial aquifer beneath the

    Primary Test Area, Graces Quarters (APG, 2001c).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 20 of 56 Figure 9. Isopleth map showing the horizontal extent of the total VOC plume in the middle aquifer beneath the

    Primary Test Area, Graces Quarters (APG, 2001c).

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 21 of 56 2.6 CURRENT AND POTENTIAL FUTURE SITE AND RESOURCE USES Graces Quarters is expected to remain under military authority with limited military training being conducted. In addition to limited military activities, future land uses at the site will include a limited-access Natural Resource Management Area for implementation of the selected remedy. Both military personnel and natural resources management workers were considered as the potential receptors for the BRA; the exposure factors for the latter type of worker were conservatively assumed the same as that of an industrial worker. There are currently no drinking water wells at Graces Quarters and the groundwater is not in use. Future use of groundwater at the site will be restricted until the site-specific RAOs have been achieved. The land use within an approximate 5-mile radius of Graces Quarters is generally residential and recreational. Several communities are present within the 5 mile radius, and some industrial/commercial use is also documented. Both the Hammerman Area of Gunpowder Falls State Park and the Dundee Natural Environmental Area are within close proximity to Graces Quarters. The estuaries and creeks around Graces Quarters are an important natural resource and are used for public recreation including boating, fishing, and swimming—although a restriction on these activities is imposed directly around the military property. The water bodies, marshes, and upland areas (particularily on the military installation where development has not occurred) are also an important habitat for waterfowl, fish, and other wildlife species. 2.7 SUMMARY OF SITE RISKS The BRA estimates what risk the site poses if no action is taken. It provides the basis for taking action, if necessary, and identifies the contaminants and exposure pathways that need to be addressed by the remedial action. This section of the ROD summarizes the results of the baseline risk asses sment for this site. 2.7.1 Human Health Risk Assessment The purpose of a human health risk assessment is to determine whether exposure to site-related contaminants could adversely affect human health. The focus of the human health risk assessment is on the possible human health effects that could occur under current or potential future use conditions in the event that contamination is not remediated. The risk is expressed as lifetime excess cancer risk (LECR) for carcinogens, and hazard index (HI) for noncarcinogens. For example, an LECR of 1 x 10-6 represents the probability of one additional cancer, in a population of one million people exposed. The cancer risk range of 1x 10-4 and . l x 10-6 is the "target range" within which the EPA strives to manage risks. A hazard index is the ratio of anticipated exposure of an individual to the reference dose, the dose at which no adverse effects are expected to occur. If this ratio is less than or equal to one, then no adverse non-cancer effects are expected to occur A hazard quotient (HQ), the sum of the hazard indices for all site contaminants and/or routes of exposure, above one presents a likelihood of non-carcinogenic health effects in exposed populations. 2.7.1.1 Identification of Chemicals of Concern The chemicals of concern in groundwater beneath the Primary Test Area include 1,1,2,2-tetrachloroethane, 1,1,2-trichloroethane, 1,1-dichloroethene, carbon tetrachloride, chloroform,

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 22 of 56 tetrachloroethene, trichloroethene, and vinyl chloride (as listed in Table 2 in Section 2.7.1.3). Maximum and average concentrations are provided in Section 2.8 (Table 3). Groundwater plumes range in concentration from non-detect at their boundaries to the peak concentrations (as listed in Table 2) and accordingly a concentration range is not provided by this table. 2.7.1.2 Exposure Assessment As discussed in Section 2.5, Site and Operable Unit Characteristics, the Conceptual Site Model indicates a relatively shallow aquifer system (classified a Type I by the MDE and Type IIB by the EPA) beneath the Primary Test Area. Groundwater from these aquifers ultimately discharges to the surrounding surface water bodies. It was determined that under the current land use conditions (groundwater is not in use and there are currently no drinking water wells) exposure to groundwater is unlikely. However, for future land-use, civilian and military workers involved with "military multiple-use" (periodic training and light equipment testing activities) of the Primary Test Area may potentially have contact with site groundwater. For military multiple-use workers, there is exposure potential via ingestion of groundwater as assumed in the Risk Assessment (the military multiple-use scenario is essentially a light industrial use assessment which has limited groundwater ingestion assumptions inherent in the scenario. Risks calculated under this scenario (as detailed in Section 2.7.1.3) use the standard EPA default parameters for workers with ingestion as the exposure route). Additional risk scenarios were evaluated at the request of the EPA. While residential land use scenarios are considered unlikely, and the reasonable worst case was assumed to be military multiple -use, residential evaluation was included for comparison purposes and to ensure a complete understanding of the spectrum of potential risk at the site. Under the hypothetical residential scenario, ingestion, inhalation, and dermal exposure routes were evaluated per EPA policy. However, it is noted that the industrial use (reasonable worst case) risk assessment is the basis for remedy selection at this site. 2.7.1.3 Toxicity Assessment The human toxicity assessment was performed in order to identify numerical toxicity criteria with which to assess human health exposures. For non-cancer health effects, chemical-specific Reference Doses (RfDs) were compiled. Chronic RfDs were used to assess long-term exposures ranging from seven years to a lifetime. Subchronic RfDs were used to evaluate the potential for adverse health effects associated with exposure to constituents over a period of 2 weeks to 7 years. Subchronic RfDs were used to evaluate the short-term construction worker hazards. Although the exposure duration for children was less than seven years, chronic RfDs were conservatively used. For cancer endpoints, chemical-specific cancer slope factors (SFs) were compiled. Whenever possible, route-specific toxicity values were used. However, toxicity values for dermal exposures have not yet been developed by EPA; therefore, the oral toxicity values and the gastrointestinal absorption efficiency were used to derive adjusted toxicity values (adjusted to the absorbed dose) for use in assessing dermal exposure.Toxicity data used to calculate the risks associated with the chemicals of concern present at the site (as listed on Table 2) under future military multiple -use and residential land use scenarios were obtained from the 1997 Integrated Risk Information System (IRIS), the 1997 Health Effects Assessment Summary Tables (HEAST), or from direct guidance from the EPA risk assessment

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 23 of 56 group. Of the chemicals of concern listed in Table 2, one (vinyl chloride) is a known carcinogen and all of the remaining chemicals with the exception of 1,1,2 – TCA are considered by the EPA to be possible carcinogens. The primary target organs that are affected by long term exposure to the majority of the chemicals listed in Table 2, include but are not limited to the liver, lungs, kidney, and the central nervous system. 2.7.1.4 Risk Characterization For military multiple use scenario, the calculated carcinogenic risk based on total VOCs is 4x10-3 and the noncarcinogenic HI is 30 (this HI is almost exclusively due to carbon tetrachloride). Table 2 presents the constituents that contributed a risk greater than or equal to 1x10-6, or HI greater than or equal to 1.0, and their calculated exposure point concentration. Table 2. Primary constituents contributing to carcinogenic risk or noncarcinogenic hazard under future military

    multi-use scenario (APG, 1998a).

    Constituent1 RI Exposure Point

    Concentration 2, µg/L Contribution to Risk Contribution to HI

    1,1,2,2-TeCA 4,400 3x10-3 N/A

    1,1,2-TCA 7.21 1x10-6 0.02 1,1-DCE 3.44 7x10-6 0.004

    CT 2,000 9x10-4 30

    CF 22.9 5x10-7 0.02

    PCE 27.7 5x10-6 0.03

    TCE 850 3x10-5 N/A

    VC 3.8 3x10-5 N/A

    Total VOCs 4x10-3 30

    1 Acronyms: TeCA, tetrachloroethane; TCA, trichloroethane; DCE, dichloroethene; CT, carbon tetrachloride; CF, chloroform; PCE, tetrachloroethee; TCE, trichloroethene; VC, vinyl chloride. 2 These data are based on RI data collected prior to 1998 that were used to calculate the risk. For residential land use scenario, the calculated carcinogenic risk of 3x10-2 and the noncarcinogenic HI of 100 (which is almost exclusively due to carbon tetrachloride) sugges ted that the groundwater at Graces Quarters would warrant active remedial actions to mitigate risks associated with exposure to the contaminated groundwater under a residential usage scenario. A breakdown of the contribution of individual constituents to the overall residential risk is detailed in the RI (APG, 1998a); the hypothetical residential exposure is unlikely, however. Diverse uncertainties are inherent in the Superfund-type Human Health BRA methodology and in the assumptions on which it is based. Both the Risk Assessment Guidance for Superfund (RAGS) methodology and the Graces Quarter-specific assumptions are conservative. The potential risk and hazard from exposure to site related contamination at Graces Quarters may differ by one or more orders of magnitude from those calculated—probably being lower. That is, where a pathway is judged to be complete and a chemical has a toxicity criterion, the calculated risk or HQ for that chemical is probably higher than the actual potential risk.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 24 of 56 2.7.2 Ecological Risk Assessment An ecological evaluation of Graces Quarters was conducted as part of the RI. Chemical analyses were performed on samples of surface soil, surface water and sediment from freshwater ephemeral ponds, and shoreline surface water and sediment from brackish water habitats (i.e., Saltpeter Creek and Gunpowder River). A survey was also conducted of the terrestrial, wetland, and aquatic flora and fauna of Graces Quarters that could be exposed to constituents of potential concern (COPCs). Surface soil, ephemeral pond surface water, and ephemeral pond sediment samples were collected from locations within the Primary Test Area and could thus be directly associated with the site. The connection between the shoreline surface water samples and the Primary Test Area is less clear because COPC, in these samples may originate from sources other than the Primary Test Area or even other than the Graces Quarters peninsula, given the tidal character of the water bodies. Thus there is a qualitative component to the evaluation of the shoreline COPC data with respect to Primary Test Area contribution. Details of the approach used to evaluate each medium are provided in the RI (APG, 1998a). The ecological risk assessment (ERA) results are summarized as follows: • During the RI, none of the chlorinated solvents that comprise the plumes in the surficial and middle aquifers

    were detected in surface soil, ephemeral pond surface water, or ephemeral pond sediment associated with the Primary Test Area.

    • No chlorinated solvents were detected in shoreline sediment samples, and only one chlorinated solvent

    (1,1,1-trichloroethane) was detected in one of the twelve shoreline surface water samples. This detection was five orders of magnitude below the Federal Ambient Water Quality Criteria. The compound 1,1,1-trichloroethane is not a significant component of the chlorinated solvent groundwater plume associated with the Primary Test Area.

    • The ERA concluded that based on comparison of the concentrations of chemicals detected in sediment to the

    available toxicity values, it is reasonable to conclude that no adverse effects are currently occurring to benthic communities from chemicals in sediments from the Primary Test Area.

    • The ERA concluded that based on comparison of the concentrations of chemicals detected in surface water to

    the available toxicity values, it is reasonable to conclude that no adverse effects are currently occurring to aquatic life from chemicals in surface water from the Primary Test Area.

    However, predictive groundwater model simulation using a starting point of plume configuration in the mid-1990's, and published by the U.S. Geological Survey (USGS) in 2001, suggested that contaminants may spread throughout various parts of the surficial and middle aquifers if no remedial action is taken (no source removal and no stimulated natural attenuation). Potential VOC discharge to the marshes south of the Primary Test Area; the marshes at the end of the Graces Quarters; or just offshore in the estuaries was also suggested by this work (USGS, 2001). Bi-annual monitoring of wells in the marshes just south of the Primary Test Area has been conducted since 1998 with the most recent round of data (December 2002) indicating continuing plume migration toward the marshes south of the Primary Test Area and VOC (1,1,2,2-

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 25 of 56 tetrachloroethane, carbon disulfate, and vinyl chloride) detections for the first time in the marsh piezometers (APG, 2003). 2.7.2 Basis for Action Based on the likelihood of future contaminant discharge to the marshes and surface waters surrounding Graces Quarters; the calculated risks to future military personnel under the reasonable worst case exposure scenario (military multiple use); the degradation of a Type I aquifer in Maryland; and the uncertainties associated with the future migration of the contaminants in the aquifer system beneath the Primary Test Area, a response action has been selected for the site that will mitigate these risks. The response action selected in this ROD is necessary to protect public health or welfare or the environment from actual or threatened releases of hazardous substances into the environment. 2.8 REMEDIAL ACTION OBJECTIVES The selected remedy is expected to meet all of the specific RAOs determined based on a review o f available data and all ARARs. RAOs consist of medium-specific goals for protecting human health and the environment. These objectives can be achieved by reducing exposure (e.g., limiting access) as well as by reducing the level of COCs. There exists the potential for exposure to contaminated groundwater associated with the Primary Test Area, although public access controls and land use restrictions are currently in place. Qualitative and quantitative RAOs are established for Operable Unit A to restore the aquifer for future beneficial use. The RAOs for Operable Unit A are as follows: • Prevent exposure to groundwater from the surficial and middle aquifers until such time as constituent

    concentrations decline below levels specified in the selected remedial alternative. • Restore the aquifers' potential for beneficial use by lowering constituent concentrations to acceptable levels that

    are established as quantitative RAOs. Quantitative RAOs are developed for groundwater constituents that produce LECRs greater than or equal to 1x10-6, have an HI greater than 1.0, are present at concentrations above their maximum contaminant level (MCL) established under the Safe Drinking Water Act, or are at cleanup levels acceptable to EPA. The maximum and average concentrations, the MCLs, and the RAOs for the COCs in the Primary Test Area groundwater are shown in Table 3.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 26 of 56 Table 3. Maximum and Average COC Concentrations, MCLs, and RAO Concentrations (APG, 2004)

    COCs1 Maximum

    Concentrations2 (µg/L)

    Average Concentrations2

    (µg/L) MCL (µg/L) RAO3 (µg/L)

    1,1,2,2-TeCA 4,400 767 N/A 5

    1,1,2-TCA 26 9.4 5 5 1,1-DCE 4.2 2.1 7 7 CT 5,710 575 5 5 PCE 120 30 5 5 TCE 963 242 5 5 VC 16 3.5 2 2

    1Acronyms: TeCA, tetrachloroethane; TCA, trichloroethane; DCE, dichloroethene; CT, carbon tetrachloride; PCE, tetrachloroethene; TCE, trichloroethene; VC, vinyl chloride. 2The maximum and average COC concentrations are based on the bi-annual monitoring data collected since 1998. RI data collected through 1998 are not included in this table. 3MCLs are identified as the RAOs for those COCs with a final MCL. 2.9 DESCRIPTION OF ALTERNATIVES A summary of the nine remedial alternatives has been developed to provide a conceptual design and cost estimate and allow for evaluation of each alternative with respect to the required evaluation criteria. While this ROD provides the basis for sound estimates for a preliminary evaluation, additional work will be required to fully assess/design a remedial system on-site. The remedial alternatives generated using the remedial action screening process for the Primary Test Area are summarized as follows: • Alternative 1: No action. • Alternative 2: Institutional controls/long-term monitoring (LTM). • Alternative 3: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L; MNA at all

    other locations. • Alternative 4: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L; pump -and-treat

    at all other locations. • Alternative 5: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L in the surficial

    aquifer; pump -and-treat at all other locations. • Alternative 6: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 100 µg/L (both aquifers);

    MNA at all other locations. • Alternative 7: Pump -and-treat at all locations.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 27 of 56 • Alternative 8: Pump -and-treat in areas greater than 1,000 µg/L (both aquifers); LTM at all other locations. • Alternative 9: Electrical resistance heating (ERH) in areas greater than 1,000 µg/L in the surficial aquifer;

    pump-and-treat at all other locations. Institutional controls and groundwater compliance monitoring are included for each alternative except Alternative 1. These controls will include appropriate warning signs, and land and water patrols, and will be detailed in the remedial design in a separate design document. Land use restrictions will be used at Graces Quarters to prohibit the unauthorized extraction and use of groundwater in Operable Unit A. Residential or military residential housing will also be prohibited. Annual site inspections will be conducted to ensure these controls are in place. The Graces Quarters groundwater Operable Unit will be included in the regularity scheduled CERCLA 5-year reviews at APG. UXO screening/clearance is required for all intrusive activities occurring at the site, but is not otherwise addressed under Operable Unit A. These issues are addressed by the Selected Remedy for Operable Unit B -- Public Access Controls, Land Use Restrictions, and Erosion Controls -- as detailed in the ROD for Carroll Island and Graces Quarters Operable Unit B (APG, 2001a). In each of the following alternatives present worth O&M cost was listed instead of annual O&M costs because most of the alternatives involve an up-front treatment option. The O&M cost is different in different years for each alternative, and continues for a different length of time in the different alternatives. Consequently, there is no uniform annual O&M cost that could be listed. The details of the O&M annual cost breakdown are given in the FS (APG, 2004) and can be found in the administrative record. 2.9.1 Alternative1: No Action • Estimated Capital Cost: $0 • Estimated Present Worth Operation & Maintenance (O&M) Cost: $0 • Estimated Total Present Worth Cost: $0 • Estimated Time to Achieve RAOs: Will not Achieve RAOs The EPA FS process requires that a "no action" alternative be evaluated as a basis for comparing alternatives. Although security patrols are presently conducted at APG and warning signs exist, no "additional" action is taken. Therefore, no efforts are undertaken to locate or prevent exposure to VOC contaminated groundwater. This alternative is used for comparison purposes to evaluate other alternatives. Under the No Action alternative for Graces Quarters Operable Unit A, no remedial efforts would be made to control risks to human or ecological receptors; treat or remove waste; or reduce the toxicity, mobility, or volume of contaminated media. Institutional actions (such as land use restrictions) specifically pertaining to Operable Unit A would not be implemented and would not continue if in place now. There are no costs associated with capital, O&M and net present worth.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 28 of 56 2.9.2 Alternative 2: Institutional Controls/LTM • Estimated Capital Cost: $0 • Estimated Present Worth O&M Cost: $400,000 • Estimated Total Present Worth Cost: $400,000 • Estimated Time to Achieve RAOs: undefined With this alternative, no actions are conducted to remediate groundwater contamination at the site. This alternative does include institutional controls that will be implemented at Graces Quarters as part of the Selected Remedy Appropriate access controls will include warning signs, and land and water patrols, the institutional controls will be detailed in the remedial design in a separate design document. Land use restrictions will be placed on the Primary Test Area Operable Unit A to prohibit the unauthorized extraction and use of groundwater. Residential or military residential housing, and extraction/use of groundwater will be prohibited. Annual site inspections will be conducted to ensure the controls are in-place. This alternative also includes LTM of groundwater at the Primary Test Area which will continue as long as exceedances of MCLs are present in the groundwater. Annual groundwater monitoring will be performed to document the plume configuration and concentration. The design workplan will outline the wells to be sampled, sample analysis, contingency plans, and criteria for discontinuation of the monitoring program. As discussed in the FS Report, groundwater monitoring will consist of sampling 20 compliance wells for VOCs annually. An annual report will present the data results and describe the plume configuration, migration, and change in contaminant levels. 2.9.3 Alternative 3: Vitamin B12-catalyzed reductive dehalogenation in areas greater than 1,000 µg/L; MNA at all other locations • Estimated Capital Cost: $2,111,496 • Estimated Present Worth O&M Cost: $3,588,504 • Estimated Total Present Worth Cost: $5,700,000 • Estimated Time to Achieve RAOs: 30 years Alternative 3, which was identified as the Preferred Alternative in the Proposed Plan issued in April 2004, involves treating areas with VOC concentrations greater than 1,000 µg/L with vitamin B12 amendment and using MNA where concentrations are less than 1,000 µg/L. Land use restrictions (described in Alternative 2) will be enforced to prevent exposure to groundwater contaminants until remediation goals are achieved. Institutional controls will be detailed in the remedial design documents. The vitamin B12 treatment technology has been demonstrated during a pilot study conducted at the Primary Test Area from September 1999 to December 2000 (APG, 2001b). The technology introduces a buffered solution of vitamin B12, titaniu m citrate, and other carbon substrates into the subsurface. The vitamin B12 amendment will be introduced into the subsurface via a recirculation well or other alternative methods such as direct injection or injection through standard wells. Vitamin B12 is a transitional-metal coenzyme containing a cobalt atom in the center of the molecule that, in a chemically reducing environment, catalyzes dechlorination of CAHs. The vitamin B12 treatment technology is expected to meet the performance standard of reducing the total VOCs concentrations to below 100 µg/L in the treatment zones within five years. This

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 29 of 56 technology also is consistent with the EPA guidance using treatment to destroy principal threats, particularly at DNAPL areas, in conjunction with MNA solutions Effective treatment of the hot spot areas will facilitate the use of MNA to remediate areas of the plume where concentrations are less than 1,000 µg/L. In addition to source treatment, the addition of vitamin B12 amendment is expected to expand the extent of the chemical reducing zones beyond the immediate treatment area over time as the vitamin B12 is transported through the aquifer beyond the initial treatment areas. Reduction in contaminant concentrations by natural attenuation will be documented and evaluated through a MNA program to be specified in the design workplan. The achievement of MCLs, which were identified as the RAOs, for the COCs allows termination of monitoring and other requirements. It is anticipated that the design and construction will take two years or less, duration of vitamin B12 injections will be for approximately a year, and that the requirement of MNA monitoring will be 30 years or less.LTM will include monitoring for arsenic and the design specifications for such monitoring will be included in the design workplan. Naturally occurring arsenic may be temporarily released from the aquifer matrix (soil) in response to the reducing conditions created by the treatment technology. This is a reversible condition and arsenic concentrations will drop following completion of the active remedy. 2.9.4 Alternative 4: Vitamin B12-catalyzed reductive dehalogenation in areas greater than

    1,000 µg/L; pump-and-treat at all other locations • Estimated Capital Cost: $3,324,793 • Estimated Present Worth O&M Cost: $6,075,207 • Estimated Total Present Worth Cost: $9,400,000 • Estimated Time to Achieve RAOs: 20 years Alternative 4 involves treating areas with VOC concentrations greater than 1,000 µg/L with the vitamin B12 amendment as detailed under Alternative 3. Groundwater extraction and surface treatment by conventional technologies will be used where concentrations are less than 1,000 µg/L. To capture the groundwater plume where concentrations are between 5 and 1,000 µg/L, groundwater will be ext racted, treated above ground using air stripping and carbon adsorption, and discharged to the Gunpowder River meeting the requirements of the National Pollutant Discharge Elimination System (NPDES) using MDE approved discharge parameters. Conventional or horizontal extraction wells would be used as needed to capture this groundwater. It is anticipated that the design and construction will take two years or less. The vitamin B12 treatment technology is expected to meet the performance standard of reducing the total VOC concentrations to below 100 µg/L in the treatment zones within five years. The performance standard that triggers a shut down of the pump -and-treat operation will be based upon the achievement of MCLs or residential RBCs for the COCs. A monitoring program will be specified in the design workplan. 2.9.5 Alternative 5: Vitamin B12-catalyzed reductive dehalogenation in areas greater than

    1,000 µg/L in the surficial aquifer; pump-and -treat at all other locations • Estimated Capital Cost: $2,471,264 • Estimated Present Worth O&M Cost: $6,128,736 • Estimated Total Present Worth Cost: $8,600,000 • Estimated Time to Achieve RAOs: 30 years.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 30 of 56 Alternative 5 combines vitamin B12-catalyzed reductive dechlorination in areas greater than 1,000 µg/L in the surficial aquifer with pump -and-treat for the remaining areas of the plume, including areas in the middle aquifer greater than 1,000 µg/L. The vitamin B12 component of Alternative 5 is similar to that described for Alternatives 3 and 4. However, this alternative only delivers vitamin B12 amendment using recirculation wells in the surficial aquifer plume in areas with total VOC concentrations above 1,000 µg/L. The groundwater extraction and treatment component of Alternative 5 is the same as that described for Alternative 4, capturing groundwater with VOC concentrations between 5 and 1,000 µg/L. For the middle aquifer, this alternative includes groundwater extraction and treatment for all contamination above 5 µg/L. As described in Alternative 4, extracted groundwater will be treated above ground using air stripping and carbon adsorption, and then discharged to the Gunpowder River meeting the requirements of the NPDES using MDE aproved discharge parameters. It is anticipated that the design and construction will take two years or less. The implementation of vitamin B12 treatment technology is expected to meet the performance standard of reducing the total VOC concentrations to below 100 µg/L in the treatment area in the surficial aquifer within five years. The performance standard that triggers a shut down of the pump -and-treat operation in both surficial and middle aquifers will be based upon the achievement of MCLs or residential RBCs for the COCs. A monitoring program will be specified in the design workplan. 2.9.6 Alternative 6: Vitamin B12-catalyzed reductive dehalogenation in areas greater than

    100 µg/L (both aquifers); MNA at all other locations • Estimated Capital Cost: $5,304,838 • Estimated Present Worth O&M Cost: $8,995,162 • Estimated Total Present Worth Cost: $14,300,000 • Estimated Time to Achieve RAOs: 20 years The vitamin B12 component of Alternative 6 is similar to that described for Alternative 3. However, Alternative 6 includes vitamin B12 treatment in areas of the plume, in both the surficial and middle aquifers, where total VOC concentrations exceed 100 µg/L. The vitamin B12 system represented here is conceptually the same as for Alternative 3 other than the increased number of wells required to treat the larger area, the increased flow rate, and an increased amount of vitamin B12 amendment used. Additionally, a pipeline installed three feet underground may be necessary to supply the vitamin B12 amendment to the delivery wells under this alternative. MNA will be used to remediate areas of the plume where total VOC concentrations are less than 100 µg/L. Reduction in contaminant concentrations by natural attenuation will be documented and evaluated through a MNA monitoring program to be specified in the design workplan. It is anticipated that the design and construction will take two years or less. The vitamin B12 treatment technology is expected to meet the performance standard of reducing the total VOC concentrations to below 100 µg/L in the treatment areas within five years. Following the termination of the vitamin B12 injections, MNA is expected to meet the MCLs or residential RBCs for COCs within 30 years, and when these levels are reached, monitoring will cease.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 31 of 56 2.9.7 Alternative 7: Pump-and-Treat at all locations • Estimated Capital Cost: $1,494,890 • Estimated Present Worth O&M Cost: $5,005,110 • Estimated Total Present Worth Cost: $6,500,000 • Estimated Time to Achieve RAOs: Indeterminate length of time due to possible DNAPL Alternative 7 consists of groundwater pump -and-treat for all of the surficial and middle aquifers where VOC contamination exceeds 5 µg/L. The extracted groundwater will be treated above ground using conventional technologies such as air stripping and carbon adsorption, and discharged to the Gunpowder River meeting the requirements of the NPDES using MDE approved discharge parameters. Compliance monitoring (documentation of the plume configuration and concentration) will consist of sampling compliance wells for VOCs, and the groundwater extraction wells for VOCs and iron quarterly during the first two years. Subsequently, the compliance wells and the extraction wells will be sampled annually during years three through five, and bi-annually thereafter. Throughout operation of the system, influent and effluent groundwater samp les will be collected from the air-stripping/adsorption system on a quarterly basis and analyzed for VOCs. Similarly, vapor samples will be collected before and after the granular activated carbon units and analyzed for VOCs to evaluate system performance. It is anticipated that the design and construction will take two years or less. A potential problem with pump -and-treat technology at this site is that contaminants, particularly DNAPL, may continue to desorb from the soil matrix once the treatment is stopped, and rebound to concentrations above the cleanup criteria. Therefore, the time required for the operation of pump -and-treat alone is indeterminate, and the long-term O&M costs may become substantial. The pumping of the diluted plume will continue until MCLs or residential RBCs for COCs are achieved. A groundwater monitoring plan will be specified in the design workplan. 2.9.8 Alternative 8: Pump-and-treat in areas greater than 1,000 µg/L (both aquifers); LTM

    at all other locations • Estimated Capital Cost: $801,934 • Estimated Present Worth O&M Cost: $2,208,066 • Estimated Total Present Worth Cost: $3,010,000 • Estimated Time to Achieve RAOs: Indeterminate length of time due to possible DNAPL Alternative 8 consists of groundwater pump -and-treat for all of the surface and middle aquifers where VOC concentrations are above 1,000 µg/L and LTM where concentrations are below 1,000 µg/L. Land use restrictions (described in Alternative 2) will be enforced to prevent exposure to groundwater contaminants until re mediation goals are achieved, if achievable under this alternative. The groundwater extraction and treatment component of Alternative 8 is similar to that of Alternatives 4, 5, and 7, capturing groundwater with VOC concentrations greater than 1,000 µg/L. The extracted groundwater will be treated above ground using conventional technologies such as air stripping and carbon adsorption, and then discharged to the Gunpowder River meeting the requirements of the NPDES using MDE approved discharge parameters. It is anticipated that the design and construction will take two years or less. As described in Alternative 7, evaluation of the system performance will include monitoring of compliance wells, extraction wells, influent and effluent groundwater samples of the air-stripping/adsorption system, and vapor samples after

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 32 of 56 the vapor phase granular activated carbon units. LTM, to be specified in the design workplan, will be instituted to assess the impact on the dissolved phase plume in response to the source control pumping, and any naturally occurring attenuation process. The pumping of the ground water plume would continue until MCLs or residential RBCs for COCs are achieved. As discussed for Alternative 7, pump -and-treat systems are known to potentially fail in areas where residual products and DNAPLs are present, as is suspected at Graces Quarters. In addition, VOCs in areas where their concentrations are below 1,000 µg/L, but still above their regulatory cleanup levels, will remain largely untreated by this alternative and may not be contained during the anticipated long treatment duration. This alternative, therefore, may not meet the performance standard of MCLs or residential RBCs for COCs. 2.9.9 Alternative 9: ERH in areas greater than 1,000 µg/L in the surficial aquifer; pump-and-treat at all other locations • Estimated Capital Cost: $3,038,504 • Estimated Present Worth O&M Cost: $6,861,496 • Estimated Total Present Worth Cost: $9,900,000 • Estimated Time to Achieve RAOs: 30 years Alternative 9 involves using ERH for remediation of the surficial aquifer where VOC concentrations exceed 1,000 µg/L. For areas in the surficial aquifer where VOC concentrations are below 1,000 µg/L, and for the entire plume in the middle aquifer, pump -and-treat will be used. This technology uses low-frequency electricity delivered to three electrodes in a triangular array to uniformly heat the target area to the boiling point of water, converting the subsurface moisture (groundwater) and contaminants to steam and vapor. The steam and vapor are extracted via conventional extraction technologies such as soil vapor extraction and are treated on site. Three-phase electricity can be obtained from the existing power source that runs to the vitamin B12 pilot study building (APG, 2002). The expected maximum temperature in the target area (100,000 ft2) will be 100 to 112 degree Celsius (°C) and the estimated power required to operate the system is 9,250,000 kilowatt hours (kW-hr) over the year of anticipated operations. ERH technology, however, is not suitable for the middle aquifer because of the difficulties involved with placing electrodes in the middle aquifer and collecting the steam and vapors. Possible concerns with ERH are the potential for releases of hazardous vapors to the atmosphere, the potential remobilization of DNAPLs into the aquifer due to decreased viscosity as it is heated by the ERH process, and physical hazards associated with high voltage and high temperatures. The latter may potentially explode the UXO, if present, and melt polyvinyl chloride (PVC) materials that are commonly used for monitoring wells in the subsurface. The pump -and-treat component of this alternative will be similar to that described in Alternatives 4, 5, 7 and 8. The extracted groundwater will be treated above ground using conventional technologies such as air stripping and carbon adsorption, and then discharged to the Gunpowder River meeting the requirements of the NPDES using MDE approved discharge parameters. It is anticipated that the design and construction will take two years or less. Evaluation of the system performance will include monitoring of compliance wells, extraction wells, influent and effluent groundwater samples of the air-stripping/adsorption system, and vapor samples after the vapor phase granular activated carbon units. The monitoring program will be specified in the design workplan. The pumping of the diluted plume will continue until MCLs or residential RBCs for COCs are achieved.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 33 of 56 2.10 COMPARATIVE ANALYSIS OF ALTERNATIVES In evaluating the remedial alternatives for Operable Unit A, the potential performance of each alternative is evaluated in terms of the nine evaluation criteria required by the NCP: • protection of human health and the environment; • compliance with ARARs; • long-term effectiveness; • reduction of toxicity, mobility, and volume of chemicals through treatment; • short-term effectiveness; • implementability; • cost; • state acceptance; and • community acceptance. The nine criteria are categorized into one of three groups: threshold criteria, primary balancing criteria, or modifying criteria. The alternative selected must satisfy the threshold criteria, which are of primary importance. The primary balancing criteria are used to weigh the major tradeoffs among the alternatives, and the modifying criteria are considered after the public has commented on the Proposed Plan. A summary of the ranking of each alternative is provided as Table 4, Comparative Analysis of Alternatives. 2.10.1 Threshold Criteria Overall Protection of Human Health and the Environment Overall protection of human health and the environment addresses whether each alternative provides adequate protection of human health and environment and describes how risks posed through each exposure pathway are eliminated, reduced, or controlled, through treatment, engineering controls, and/or institutional controls. Alternative 1 (no action) may not provide adequate long-term protection of human health and the environment because no restrictions are assumed to be in place to prevent future use of the contaminated groundwater at the site. Although the site is on Department of Defense (DOD) property, this alternative assumes that land use restrictions will not be enforced. Groundwater monitoring will not be conducted, so no data will be available to evaluate contamination concentrations and migration. Alternatives 2 through 9 are considered protective of human health because land use restrictions will prohibit future use of groundwater from the Primary Test Area and Alternatives 3 through 9 provide for remediation of the groundwater. These alternatives vary, as detailed in the FS Report, with respect to long-term protection of human health and the environment (APG, 2004). Overall, Alternative 6 receives the best rating for this criterion due to its aggressive treatment of almost the entire plume (at a proportionally larger cost). Alternatives 3, 4, 5, 7, and 9 receive a good rating. Alternatives 2 and 8 receive an adequate rating while Alternative 1 a poor rating.

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 34 of 56

  • Record of Decision September 2004 Graces Quarters Operable Unit A: Groundwater Final Aberdeen Proving Ground, Edgewood, Maryland Page 35 of 56 Compliance with ARARs Section 121(d) of CERCLA and NCP §300.430(f)(1)(ii)(B) require that remedial actions at CERCLA sites at least attain legally applicable or relevant and appropriate Federal and State requirements, standards, criteria, and limitations which are collectively referred as "ARARs," unless such ARARs are waived under CERCLA section 121(d)(4). The MCLs specified in the National Primary Drinking Water Standards are relevant and appropriate requirements. Based on the high formation permeability, the natural water quality and low total dissolved solids, the aquifers beneath the Primary Test Area are classified by the State of Maryland as Type I (COMAR 26.08.02.09). The EPA classifies both the unconfined and middle aquifer

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EPA/ROD/R03-04/607 2004 EPA Superfund Record of Decision: ABERDEEN PROVING GROUND (EDGEWOOD AREA) EPA ID: MD2210020036 OU 21 EDGEWOOD, MD 09/30/2004
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