USEPA_1997_Sudbury_ROD.pdf

EPA/ROD/R01-97/160

EPA Superfund

Record of Decision:

FORT DEVENS-SUDBURY TRAINING ANNEX

EPA ID: MAD980520670

OU 01, 02, 03

SUDBURY, MA

09/30/1997

<IMG SRC 971600>

<IMG SRC 97160A>

RECORD OF DECISION

AREA OF CONTAMINATION A4

AND AREAS OF CONTAMINATION A7 AND A9

MANAGEMENT OF MIGRATION OPERABLE UNITS

U.S. ARMY SUDBURY ANNEX

MIDDLESEX COUNTY, MASSACHUSETTS

SEPTEMBER 1997

TABLE OF CONTENTS

Figure Title Page No.

1.0 SITE NAME, LOCATION, AND DESCRIPTION....................................................1-1

2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES ................................................2-1

2.1 LAND USE AND RESPONSE HISTORY .....................................................2-1

2.1.1 AOC A4-Waste Dump ..........................................................2-2 2-1.2 AOC A7-Old Gravel Pit Landfill .............................................2-3

2.1.3 AOC A9-POL Bum Area ........................................................2-6

2.2 ENFORCEMENT HISTORY ...............................................................2-8

3.0 COMMUNITY PARTICIPATION ................................................................3-1

4.0 SCOPE AND ROLE OF RESPONSE ACTION ......................................................4-1

5.0 SUMMARY OF SITE CHARACTERISTICS ........................................................5-1

5.1 AOC A4 ............................................................................5-1

5.2 AOC A7 ............................................................................5-3

5.3 AOC A9 ............................................................................5-7

6.0 SUMMARY OF SITE RISKS ..................................................................6-1

6.1 SUMMARY OF RISKS AT AOC A4 ........................................................6-2

6.1.1 Human Health Risk Assessment Summary for AOC A4 ............................6-3

6.1.2 Ecological Risk Assessment Summary for AOC A4 ..............................6-5

6.2 SUMMARY OF RISKS AT AOC A7 ........................................................6-6

6.2.1 Human Health Risk Assessment Summary for AOC A7 ............................6-6

6.2.2 Ecological Risk Assessment Summary for AOC A7 ..............................6-8

6.3 SUMMARY OF RISKS AT AOC A9 .......................................................6-10

6.3.1 Human Health Risk Assessment Summary for AOC A9 ...........................6-10

6.3.2 Ecological Risk Assessment Summary for AOC A9 .............................6-12

7.0 DESCRIPTION OF THE NO ACTION ALTERNATIVE ...............................................7-1

8.0 DOCUMENTATION OF NO SIGNIFICANT CHANGES ................................................8-1

9.0 STATE ROLE .............................................................................9-1

APPENDICES

APPENDIX A - FIGURES

APPENDIX B - TABLES

APPENDIX C - RESPONSIVENESS SUMMARY

APPENDIX D - ADMINISTRATIVE RECORD INDEX

APPENDIX E - MASSACHUSETTS DEPARTMENT OF ENVIRONMENTAL

PROTECTION LETTER OF CONCURRENCE

APPENDIX F - GLOSSARY OF ACRONYMS AND ABBREVIATIONS

Figure Title 1 Location Map U.S. Army Sudbury Annex 2 Location of AOCs A4, A7, and A9 3 Site Map for AOC A4 4 Site Map for AOC A7 5 Site Map for AOC A9

Table Title

1 Human Health Risk Assessment Chemicals of Potential Concern at AOC A4 2 Summary of Human Health Baseline Risk Assessment for AOC A4 3 Human Health Risk Assessment Chemicals of Potential Concern At AOC A7 4 Summary of Human Health Baseline Risk Assessment for AOC A7 5 Human Health Risk Assessment Chemicals of Potential Concern At AOC A9 6 Summary of Human Health Baseline Risk Assessment for AOC A9

DECLARATION FOR THE RECORD OF DECISION

SITE NAME AND LOCATION

Areas of Contamination A4, A7, and A9 U.S. Army Sudbury Annex Middlesex County, Massachusetts

STATEMENT OF PURPOSE AND BASIS

This decision document presents the U.S. Army's selected remedial action decision for Area of Contamination (AOC) A4 - Waste Dump and the Management of Migration Operable Units (OUs) at AOCs A7-Old Gravel Pit Landfill and A9-POL Burn Area, at the U.S. Army Sudbury Annex, Middlesex County, Massachusetts. It was developed in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA) as amended, 42 USC ºº 9601 et seq. and the National Oil and Hazardous Substances Pollution Contingency Plan (NCP) as amended, 40 CFR Part 300, to the extent practicable. The Sudbury Annex Base Realignment and Closure (BRAC) Environmental Coordinator; the Devens Reserve Forces Training Area (RFTA) Installation Commander; and the Director of the Office of Site Remediation and Restoration, U.S. Environmental Protection Agency (USEPA) New England have been delegated the authority to approve this Record of Decision.

This decision document is based on the Administrative Record that has been developed in accordance with Section 113(k) of CERCLA. The Administrative Record is available for public review at the Devens BRAC Environmental Office, Building 666, Devens RFTA, Massachusetts, and at the Sudbury, Massachusetts Town Hall. The Administrative Record Index (Appendix D of this Record of Decision) identifies each of the items considered during selection of the remedial action.

DESCRIPTION OF THE SELECTED REMEDY

The U.S. Army and USEPA, with concurrence of the Massachusetts Department of Environmental Protection (MADEP), have determined that no action is necessary to ensure protection of human health and the environment at AOC A4 and the Management of Migration OUs at AOCs A7 and A9. Therefore, the Army's selected remedy is No Action Under CERCLA. At AOCs A7 and A9, previous removal and containment actions have eliminated underground storage tanks and removed or contained contaminated media which would otherwise be a continuing source of groundwater contamination.

DECLARATION

The U.S. Army and the USEPA, with concurrence of the MADEP, have determined that No Action Under CERCLA is necessary for protection of human health and the environment at AOC A4 and the Management of Migration OUs at AOCs A7 and A9. The selected remedy is consistent with CERCLA and to the extent practicable the NCP. Based on previous source area removal and containment actions and the results of the Site Investigation and Remedial Investigation, no action is necessary for AOC A4 and the Management of Migration OUs at AOCs A7 and A9 to ensure protection of human health and the environment.

Because this is a decision for No Action Under CERCLA, the statutory requirements of CERCLA Section 121 for remedial actions are not applicable, and no five-year review will be undertaken as part of this remedy. The Army will conduct long-term groundwater monitoring at AOC A7 as part of the remedy for the AOC A7 Source Control OU and will conduct five-year site reviews as part of that remedy.

The foregoing represents the decision for No Action Under CERCLA by the U.S. Department of the Army and the U.S. Environmental Protection Agency, with the concurrence of the Commonwealth of Massachusetts Department of Environmental Protection.

Concur and recommend for immediate implementation:

U.S. DEPARTMENT OF THE ARMY

<IMG SRC 97160B>

The foregoing represents the decision for No Action Under CERCLA by the U.S. Department of the Army and the U.S. Environmental Protection Agency, with the concurrence of the Commonwealth of Massachusetts Department of Environmental Protection.

Concur and recommend for immediate implementation:

<IMG SRC 97160C>

The foregoing represents the decision for No Action Under CERCLA by the U.S. Department of the Army and the U.S. Environmental Protection Agency, with the concurrence of the Commonwealth of Massachusetts Department of Environmental Protection.

Concur and recommend for immediate implementation:

<IMG SRC 97160D>

1.0 SITE NAME, LOCATION, AND DESCRIPTION

The U.S. Army Sudbury Annex (the Annex) is a National Priorities List (NPL) site under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The Annex occupies approximately 4.3 square miles (2,750 acres) in the Massachusetts towns of Hudson, Marlborough, Maynard, Stow, and Sudbury. It is located approximately 20 miles west of Boston and 12 miles northwest of Natick, Massachusetts (Figure 1 in Appendix A). Hudson Road divides the installation into two sections: the larger, northern section, and the smaller, southern section. The Annex became part of Fort Devens, now the Devens Reserve Forces Training Area (RFTA), in 1982.

The Annex historically served as a munitions storage area, ordnance test area, research and development facility, and as a troop training ground. The Annex currently contains military family housing, guest housing, a geophysical radar station operated by the U.S. Air Force, and offices for the Federal Emergency Management Agency (FEMA).

This Record of Decision addresses past releases of contaminants to all media at Area of Contamination (AOC) A4-Waste Dump, and past releases to groundwater at AOC A7-Old Gravel Pit Landfill and AOC A9-Petroleum Oil, and Lubricant (POL) Burn Area. For the purposes of site remediation, a source control (soil) operable unit (OU) and a management of Migration (groundwater) OU was created for AOCs A7 and A9.

Source control actions are documented in the Record of Decision for the source control OUs for AOCs A7 and A9. All three AOCs are located within the northern section of the Annex (Figure 2 in Appendix A).

In September 1995, the Annex was identified for cessation of operations and closure under the Defense Base Realignment and Closure (BRAC Act of September 1990, Closure is tentatively scheduled for November 1997. Except for a small area to be retained for Army housing within the southern section of the installation, the Annex will be transferred to three federal agencies. The majority of the land has been requested by the U.S. Fish and Wildlife Service (USFWS) and will become part of the Great Meadows National Wildlife Refuge. The U.S. Air Force and FEMA have also requested small parcels to continue their existing operations at the Annex.

A more complete description of the Annex can be found in the Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts, and the Addendum Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts, prepared by OHM Remediation Services, Inc. in 1994 and 1995, respectively). These reports, referred to as the SI/RI and SI/RI addendum reports in this Record of Decision, are both available for review at the BRAC Environmental Office at Devens RFTA, Devens Massachusetts, and the town libraries in Hudson, Maynard, and Stow.

2.0 SITE HISTORY AND ENFORCEMENT ACTIVITIES

2.1 LAND USE AND RESPONSE HISTORY

The facility presently known as the Annex was established in the late 1930s as the Maynard Ammunition Sub-depot. The properly was acquired by the U.S. Government in 1942 and named the Maynard Ammunition Backup Storage Point. It was used for ammunition storage and as a loading point for ammunition being transported overseas. Following World War II, jurisdiction over the facility was transferred from the Chief of Transportation to the Chief of Ordnance. In 1950, control of the facility was transferred to the First Army, as a subinstallation of Fort Devens, for storage and training.

In 1952, the facility, under control of the Chief of Ordnance, became known as the Maynard Ordnance Test Station. From 1952 to 1957, the primary military activities at the facility involved classified research and development by the Universal Match Corporation and the Arthur D. Little Company that may have included rocket, pyrotechnics, and explosives testing. At the expiration of the Universal Match Corporation contract in 1957, the Ordnance Corps transferred control of the facility to the Quartermaster Corps to help relieve crowded conditions at the nearby Natick Laboratories. In December 1957, the facility was designated the Maynard Quartermaster Test Activity.

From 1957 to 1982, the Annex was used as a field resource by Natick Laboratories. The Natick Laboratories mission was research and development in the physical, behavioral, and biological sciences, and engineering to develop commodities such as clothing and protective equipment. Physical research and development activities included the development of air drop techniques, field shelters and equipment, field organization equipment, fuel delivery systems, and food and food service systems. Scientific research and development included determination of the stability of various fungicides in materials exposed to outdoor environments, foamed plastics field tests, flame testing of clothing and equipment, toxic fumigant effects on insects, and the study of climatic data in support of various test programs and air drop testing.

In 1982, operational control of the Annex was transferred to Fort Devens. From 1982 through 1994, the Annex was used by Fort Devens to support its mission to train active duty and reserve personnel, and to support the U.S. Army Security Agency Training Center and School, U.S. Army Reserves, National Guard, Reserve Officer Training Corps, and Air Defense sites in New England. By agreement with Fort Devens, Natick Laboratories retained certain use and occupancy rights after property transfer to Fort Devens.

This agreement included conditional use of approximately 8 acres of land known as the POL Burn Area, use of a 30-acre area as an air drop zone, use of specific storage areas, and use of a field evaluation course.

Other agencies and organizations that have used or leased portions of the Annex include the U.S. Air Force and its contractors, Raytheon Corporation, Massachusetts Air National Guard, Massachusetts State Police Academy, Massachusetts Army National Guard, Massachusetts Fire Fighting Academy (MFFA), and FEMA.

2.1.1 AOC A4-Waste Dump

AOC A4 is located near the Eastern Gate and the intersection of Craven Lane and Patrol Road (Figure 3 in Appendix A). It occupies an area of approximately 1,000 by 200 feet along the northwestern side of Craven Lane, from Patrol Road to a wetland on the site's southwestern border. The center of the site consists of a grassy area, whereas trees and low bushes are present along the edges. The land surface slopes gradually from Craven Lane toward the southwest. Groundwater flow is toward the west and the wetland at the western site boundary. The site contains a surface dump near its southwest end and a building foundation dated to the late 1600's at the northeast end. At the time of the SI/RI, the ground surface was littered with plastic bags, empty food and beverage cans, empty paint cans, demolition debris, and glass. The site reportedly was used for the burial of unidentified chemical wastes and drums over a three to four year period from the late 1960s to early 1970s.

The following items summarize the history of AOC A4:

• Late 1960s to early 1970s. During this period, AOC A4 was reportedly used for the burial of unidentified chemical wastes and drums.

• 1980. AOC A4 (then designated Location 15) was identified as a suspected waste disposal site by the Army during a records search.

• 1983. The Army Environmental Health Agency (AEHA) performed an hydrogeologic and subsurface assessment which included installation of one groundwater monitoring well at AOC A4.

• 1984. A pre-CERCLA investigation was performed to characterize groundwater quality downgradient of reported dumping areas. Groundwater sampling indicated low concentrations of inorganics, volatile organic compounds (VOCs), and semivolatile organic compounds (SVOCs). Of the detected analytes, iron, manganese and methylene chloride exceeded U.S.

Environmental Protection Agency (USEPA) drinking water standards; however, iron and manganese concentrations were consistent with background concentrations and methylene chloride was concluded to be the result of laboratory contamination. It was concluded that the presence of other analytes not attributable to background conditions or laboratory procedures could be indicative of a low degree of groundwater contamination. Surface water and sediment samples collected from the bordering stream did not show significant contamination.

• 1991-1993. A two phase RI was performed to assess the nature and extent of contamination in surface soil, groundwater, sediment, and surface water at the site. Investigations included geophysical surveys to locate buried drums and other disposal debris, installation of additional groundwater monitoring wells and several test pits, collection of soil and groundwater samples, and a baseline risk assessment.

Because of seasonal dry-weather conditions, surface water samples could not be collected, and shallow groundwater samples were substituted. This was subsequently identified as a data gap.

• 1996. Data gap investigations were performed to assess surface water contamination. The technical memorandum prepared to discuss the findings of the data gap activities concluded that chemicals of potential concern in surface water were present at or below background concentrations and did not pose unacceptable risk to human health or the environment. The technical memorandum recommended that no further action be taken concerning soil and groundwater at AOC A4.

A more detailed description of AOC A4 site history can be found in the Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts; the Addendum Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts; and the Final Technical Memorandum, Remedial (Data Gap) Investigation, Area of Contamination A4, US. Army Sudbury Annex. These three reports are available for review at the BRAC Environmental Office at Fort Devens, and the town libraries in Hudson, Maynard, and Stow.

2.1.2 AOC A7-Old Gravel Pit Landfill

AOC A7 is a 10-acre site located on the north side of Patrol Road along the northern installation boundary (Figure 4). The northern edge of the site is within approximately 100 feet of the Assabet River. The site is generally wooded, but does have a large sandy clearing near its center. The ground surface slopes toward the north and the Assabet River from Patrol Road.

Groundwater flow is also to the north. Aerial photographs indicate the area was first used as a source for gravel during the early 1940s.

Interviews with Natick Laboratories employees identified AOC A7 as the location of laboratory chemical dumping from the late 1950s through 1971. Chemicals were reportedly buried in a shallow trench as well as poured directly onto the ground. General refuse was reported buried at the site as early as 1941; a practice which continued into the 1980s. Refuse including metal pipes, abandoned fuel tanks, drums, and debris was observed during site investigations. Site P8, a reported transformer disposal site, is situated along the eastern edge of AOC A7. Site P8 was identified in 1990 as the possible location of transformer disposal within the A7 site. During the file search, no reference to transformer disposal at the site could be located.

The following items summarize the history of AOC A7:

• Early 1940s through early 1950's. Site used as a borrow pit.

• 1940's through 1980s. AOC A7 used for general refuse dumping, burning, and burial.

• Late 1950s through 1971. AOC A7 reportedly used for disposal of waste chemicals.

• 1980. AOC A7 (then designated Location 12) was identified as a dumping, chemical disposal, and burning ground by the Army during a records search.

• 1983. AEHA installed one groundwater monitoring well and performed groundwater sampling and analysis for drinking water parameters as part of an investigation to evaluate the hydrogeologic setting and groundwater quality. The only detections were low concentrations of fluoride and nitrate.

• 1984. A second monitoring well was installed and groundwater samples collected. In addition, surface water and sediment samples were collected from a small unnamed stream at the eastern edge of the site. Analytical results indicated potential groundwater contamination with phthalates and inorganics, including hexavalent chromium. Surface water samples contained low concentrations of iron and acetone, and sediment contained arsenic at concentrations consistent with background and low concentrations of several polynuclear aromatic hydrocarbons (PAHs).

• 1991-1993. A two phase RI was performed to assess the nature and extent of contamination in surface soil, subsurface soil, groundwater, sediment, and surface water at the site.

Investigations included a geophysical study, test pit excavation with subsurface soil sampling, surface soil sampling, installation of soil borings with soil sampling, installation of additional groundwater monitoring wells with groundwater sampling, surface water and sediment sampling, an hydrogeologic assessment, an ecological assessment, and a baseline risk assessment.

Although groundwater contamination was identified, the SI/RI addendum report was unable to conclude whether it had migrated beyond the installation boundary. This was identified as a data gap requiring additional investigation.

• 1993. A feasibility study was performed to evaluate potential remedial alternatives for source area (soil) and management of migration (groundwater) OUs at AOC A7.

• September 1995. The Record of Decision for the Source Control Operable Unit at AOC A7 was signed. The selected source area remedy included removal of chemical waste debris in the laboratory dump area, considered to be the primary source of groundwater contamination, construction of a double-barrier (RCRA Subtitle C) landfill cap to contain remaining site contaminants, operation and maintenance, institutional controls and land use restrictions to limit future use of the land at AOC A7, long-term groundwater monitoring, and five-year site reviews to assess whether the remedy remains protective of human health and the environment.

• July-November 1996. A part of the source area cleanup, chemical waste debris in the laboratory dump area, was excavated for off site disposal, and a double-barrier (RCRA Subtitle C) landfill cap was constructed to contain remaining site contaminants. The two-acre landfill cap was used to contain approximately 6,200 cubic yards of waste material from AOC A7 as well as 5,800 cubic yards of non-hazardous material from other Annex sites needed as fill to meet the design specifications for the cap.

• 1996. Data gap investigations were performed to assess whether groundwater contamination had migrated beyond the installation boundary. The technical memorandum prepared to discuss the findings of the data gap investigations concluded that although groundwater contamination was present beyond the installation boundary, it did not pose an unacceptable risk to human health or the environment. The technical memorandum recommended that no further action be taken concerning groundwater at AOC A7.

• February 1997. The Final Operations and Maintenance Plan For The Landfill At Area Of Concern A7 outlined the long-term monitoring program for AOC A7. The initial program includes semi-annual sampling of 13 monitoring wells located to enable assessment of contaminant migration from AOC A7. These monitoring wells include wells along the site perimeter and three wells located near the Assabet River to monitor potential contaminant migration toward the river. Samples will be analyzed, at a minimum for the following parameters: VOCs, pesticides, metals, phosphate, sulfate, chloride, nitrate, ammonia, total dissolved solids, chemical oxygen demand, dissolved oxygen, and cyanide.

A more detailed description of AOC A7 site history can be found in the Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts, the Addendum Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts; and the Final Technical Memorandum, Remedial (Data Gap) Investigation, Area of Contamination A7, U.S. Army Sudbury Annex. These three reports are available for review at the BRAC Environmental Office at Fort Devens, and the town libraries in Hudson, Maynard, and Stow.

2.1.3 AOC A9-POL Burn Area

AOC A9 is an eight acre site located on the north side of Patrol Road along the northern installation boundary, approximately 600 feet north of AOC A7 (Figure 5 in Appendix A). The northern edge of the site is within approximately 100 feet of the Assabet River. The site is level and predominately grassy with some pine and oak trees along the western and northern edge. Groundwater in the area flows toward the Assabet River.

AOC A9 was used for flame testing of fire regardant clothing, POL testing and/or storage, MFFA training, and destruction of confiscated fireworks. Testing of fire regardant clothing involved exposing clothing to a JP-4 jet fuel fire in an asphalt lined pit. A 1,000 gallon underground storage tank (UST) (Site P-12) was used to store JP-4 at the site, presumably to supply fuel for this testing. Testing reportedly occurred during a two week period each year from the late 1950s to the 1980s.

Starting around 1970, the MFFA used the area to conduct training on flammable liquid fires. This training reportedly involved extinguishing fires of No. 2 fuel oil and JP-4 tank bottoms floating on water in a shallow concrete pit. Other fire training was conducted in unlined pits and trenches. This training continued until at least 1994 and also included control of flames and smoke associated with the testing of fire regardant clothing by Natick Laboratories. Natick Laboratories also performed some POL testing at the site.

The Massachusetts State Police burned confiscated fireworks at AOC A9 from the early-to-mid 1970s until 1991.

During a 1986 site inspection by representatives by the Massachusetts Department of Environmental Quality Engineering (MADEQE), numerous drums of unidentified material were being stored at the site.

The following items summarize the history of AOC A9:

• Late 1950s-1986. Natick Laboratories conducted fire regardant clothing testing at the site.

• 1962. Natick laboratories began POL testing and continued for an unknown length of time.

• 1970-1984. MFFA conducted fire training exercises at the site.

• Mid 1970s-1991. Massachusetts State Police burned confiscated fireworks at the site.

• 1980. AOC A9 (then designated Location 4) was identified as a fire test facility by the Army during a records search.

• 1984. Investigation of the site begins. Samples collected between 1984 and 1987 indicate that surface soil is contaminated with PAHs, phthalates, and hydrocarbons. Groundwater is contaminated with chlorinated VOCs and fuel related hydrocarbons including ethylbenzene, toluene, and xylenes.

• March 1986. Representatives of the MADEQE observed standing oil in trenches, oil stained soils, and unmarked drums at the site.

• June 1986. All above ground tanks and drums are removed.

• 1987-1988. Approximately 1,100 cubic yards of contaminated soil are removed up to a depth of approximately 26 feet below ground surface (bgs) and disposed of under manifest.

• 1991-1993. A two phase RI was performed to assess the nature and extent of contamination in surface soil, subsurface soil, and groundwater at the site. Investigations included a geophysical study, soil-gas study, surface and subsurface soil sampling, installation of additional groundwater monitoring wells with groundwater sampling, an hydrogeologic assessment, an ecological assessment, and a baseline risk assessment.

The SI/RI addendum report identified both petroleum-related and chlorinated solvent contamination in groundwater. Although free-phase chlorinated solvents were not encountered during SI/RI activities, the inability to rule out the presence of a dense non-aqueous phase liquid (DNAPL) plume was considered a data gap.

• 1992. The 1,000 gallon UST (Site P-12) and approximately 31 cubic yards of contaminated soil were removed.

• 1993. A feasibility study was performed to evaluate potential remedial alternatives for source area (soil) and management of Migration (groundwater) OUs at AOC A9.

• 1996. As part of the source area cleanup, approximately 11 cubic yards of contaminated soil from hot spot locations were excavated and transported to AOC A7 for containment under a landfill cap.

• 1996. Data gap investigations were performed to assess the presence or absence of DNAPL at AOC A9. The technical memorandum prepared to discuss the findings of the data gap investigations concluded that DNAPL plumes were not present and recommended that no further action be taken concerning groundwater at AOC A9.

A more detailed description of AOC A9 site history can be found in the Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts; the Addendum Site/Remedial Investigation Report, Fort Devens Sudbury Training Annex, Middlesex County, Massachusetts; and the Final Technical Memorandum, Remedial (Data Gap) Investigation, Area of Contamination A9, U.S. Army Sudbury Annex. These three reports are available for review at the BRAC Environmental Office at Fort Devens, and the town libraries in Hudson, Maynard, and Stow.

2.2 ENFORCEMENT HISTORY

On January 29, 1987, the Annex was classified as a Federal Facility under the jurisdiction, custody, and control of the U.S. Department of Defense, within the meaning of Executive Order 12580, and within the meaning of the Defense Environmental Restoration Program (DERP), 10 U.S.C., Section 2701 et seq.

On February 21, 1990, the Annex was placed on the NPL under CERCLA, as amended by the Superfund Amendments and Reauthorization Act of 1986 (SARA), to evaluate and implement response actions to cleanup past releases of hazardous substances, pollutants, and contaminants. A Federal Facility Agreement (FFA) to establish a procedural framework for ensuring that appropriate response actions are implemented at the Annex was developed and signed by the U.S. Army and the USEPA Region I on May 13, 1991, and finalized on November 15, 1991. AOCs A4, A7, and A9 are considered subsites to the entire installation.

In 1991, the U.S. Department of Defense, through the U.S. Army Environmental Center (USAEC), initiated an SI/RI for AOCs A4, A7, and A9, and the final SI/RI report was issued in January 1994. An addendum to the report was issued in September 1995. The purpose of the SI/RI was to determine the nature and extent of contamination, assess human health and ecological risks, and assess whether additional response actions were necessary. A feasibility study to develop and evaluate candidate alternatives to protect human and ecological receptors from unacceptable risks associated with potential exposure to contaminated media at AOCs A7 and A9 was completed in 1995.

The Proposed Plan detailing the Army's plan of No Action Under CERCLA for AOC A4 and the Management of migration OUs at AOCs A7, and A9 was issued in June 1997 for public comment. Technical comments presented during the public comment period are included in the Administrative Record. The Responsiveness Summary, Appendix C to this Record of Decision, contains a summary of these comments and the Army's responses, and describes how these comments affected the No Action Under CERCLA decision.

3.0 COMMUNITY PARTICIPATION

The Army has held quarterly public Technical Review Committee (TRC) meetings, issued newsletters and press releases, and held a number of public meetings to keep the community and other interested parties informed of activities at the Annex.

In April 1992, the Army released, following public review, a community relations plan that outlined a program to address community concerns and keep citizens informed about and involved in remedial activities at the Annex. As part of this plan, the Army established a TRC, which first met May 13, 1991.

The TRC, as required by SARA Section 211 and Army Regulation 200-1, included representatives from USEPA, USAEC, Fort Devens, Massachusetts Department of Environmental Protection (MADEP), U.S. Army Corps of Engineers (USACE), local officials, and the community. The TRC meets quarterly to review and provide technical comments on schedules, work plans, work products, and proposed activities for the study areas at Sudbury Annex. The SI/RI, SI/RI addendum, and feasibility study reports, technical memoranda, Proposed Plan, and other related support documents were submitted to the TRC for their review and comment.

During the week of June 9, 1997, the Army published a public notice announcing the Proposed Plan, public informational meeting, and public hearing in the Sudbury Town Crier, the Middlesex News, the Marlborough-Hudson Enterprise, the Stow Villager, and the Maynard Beacon. The Army also made the Proposed Plan available to the public at the information repositories at the libraries in Stow, Hudson, Sudbury, and Maynard, and at Devens RFTA.

From June 9 through July 8, 1997, the Army held a 30-day public comment period to accept public comments on the Proposed Plan. On June 10, 1997, the Army held an informal public hearing at the Stow Town Building, in Stow, Massachusetts to discuss the Proposed Plan and to accept verbal or written comments from the public. Verbal comments were received from the Four Town Focus and subsequently were elaborated upon in writing. Public comments and the Army's response to comments are included in the Responsiveness Summary (Appendix C of this Record of Decision).

All supporting documentation for the No Action Under CERCLA decision for AOC A4 and the Management of Migration OUs at AOCs A7 and A9 is contained in the Administrative Record The Administrative Record is a collection of all the documents considered by the Army in making the No Action Under CERCLA decision. On March 20, 1994, the Army made the Administrative Record available for public review at the Sudbury Annex BRAC Environmental Office, and at the Sudbury Town Hall, Sudbury, Massachusetts.

4.0 SCOPE AND ROLE OF RESPONSE ACTION

This No Action decision addresses all media at AOC A4 and the management of migration (i.e., groundwater) OUs at AOCs A7 and A9 at the U.S. Army Sudbury Annex. The risk assessments contained in the SI/RI and SI/RI addendum reports for these AOCs indicate that environmental media at AOC A4 and groundwater contamination at AOCs A7 and A9 does not pose an unacceptable risk to human health or the environment.

Technical memoranda for AOCs A4, A7, and A9 completed subsequent to the SI/RI reports provide additional support for this conclusion. Based on this conclusion, the U.S. Army and the USEPA, with the concurrence of the MADEP, have determined that No Action Under CERCLA is required for AOC A4 and the Management of migration OUs at AOCs A7 and A9.

Potential risks to human health and the environment posed by AOC A4 have not previously been addressed by a Record of Decision. Potential risks to human health and the environment posed by source area OUs (i.e., contaminated soil and waste material) at AOCs A7 and A9 were addressed in the final Record of Decision for source control OUs for A7 and A9 signed in September 1995. No other OUs or known sources of contamination of concern exist at these AOCs.

USEPA has the authority to revisit the No Action Under CERCLA decision if future conditions indicate that an unacceptable risk to human health or the environment would result from exposure to contaminants at AOCs A4, A7, and A9. Such a review could occur even if the Annex is removed from the NPL.

5.0 SUMMARY OF SITE CHARACTERISTICS

The Army performed SI/RI activities in 1992 and 1993 and data gap activities in 1996 to characterize the nature and distribution of contaminants at AOCs A4, A7, and A9. Detailed descriptions of the investigations and available data are presented in the SI/RI and SI/RI addendum reports as well as technical memoranda. The following subsections summarize significant findings of the contamination assessments from those reports.

5.1 AOC A4

Soils. During the Phase I and Phase II RI sampling, eight surface soil and 23 subsurface soil samples were collected for analysis. In general, target analytes included Target Compound List (TCL) VOCs, SVOCs, pesticides, polychlorinated biphenyls (PCBs), chlorinated herbicides, explosives, and Target Analyte List (TAL) metals. Several samples were also analyzed for organophosphorus pesticides and total petroleum hydrocarbons (TPH).

VOCs were detected at low concentration in several Phase I samples; however, all were attributed to laboratory contamination or to naturally occurring turpenes. Only one SVOC, chrysene, was detected above soil screening concentrations. Because it was found in only one sample of 24, it was not considered a chemical of potential concern (COPC).

All pesticide detections were at concentrations less than Massachusetts Contingency Plan (MCP) S-1/GW-1 standards. TPH was detected at a maximum concentration of 35 Ig/g. PCBs and explosives were not detected. With the exception of lead and zinc, all metals were detected at concentrations less than screening criteria or at concentrations representative of background.

Groundwater. A total of 17 groundwater samples were collected from six monitoring wells during Phases I and II of the SI/RI. In general, target analytes included TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, and TAL metals. Several samples were also analyzed for organophosphorus pesticides.

VOCs were not detected above screening criteria in any samples. Toluene was detected at a low concentration in the Phase I sample from one monitoring well; it was not detected in Phase II samples.

Only one SVOC was detected; however, its presence was attributed to laboratory contamination. Pesticides were detected in samples from two monitoring wells at concentrations below federal drinking water Maximum Contaminant Levels (MCLs). PCBs and explosives were not detected.

Several inorganics were detected in groundwater. Of these, lead in one unfiltered Phase I sample showed the greatest potential to be a contaminant of concern. Analysis of unfiltered and filtered samples from the same monitoring well in Phase II showed unfiltered concentrations well below the federal drinking water action level of 15 micrograms per liter (Ig/L). Lead was not detected in the filtered sample.

Aluminum, iron, and manganese were detected in several samples at concentrations greater than federal drinking water Secondary Maximum Contaminant Levels (SMCLs). No other metals were detected at concentrations above screening criteria.

Surface Water. Characterization of surface water during the Phase I and Phase II SI/RI included collection and analysis of seven surface water samples. Most of the samples were analyzed for TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, and TAL metals. Several samples were also analyzed for organophosphorus pesticides.

There were no positive identifications of VOCs and SVOCs or confirmations of explosives in the samples.

The pesticides endrin aldehyde and 2,2-bis(para-chlorophenyl)-1,1,1-trichloroethane (DDT) and the herbicide dacthal were each reported once. No other pesticides or herbicides were reported.

Concentrations of metals, including lead, aluminum, chromium, copper, and zinc, exceeded aquatic life screening criteria at several locations. With the exception of zinc, exceedances were attributed to the presence of high suspended particulate concentrations in the samples. Elevate concentrations of zinc were attributed to laboratory contamination. Concentrations of arsenic were below screening criteria for aquatic life, but exceeded human health screening criteria.

As part of data gap activities to assess surface water contamination, three surface water samples were collected in 1996 and, based on evaluation of previous data, analyzed for lead. Lead was not detected in two of the samples and was present at a concentration below background in the third.

Sediment. Sediment samples were collected from eleven locations during the Phase I and Phase II SI/RI.

Most of the samples were analyzed for TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, and TAL metals. Phase II samples were also analyzed for organophosphorus pesticides.

Several VOCs and SVOCs were detected in sediment samples, but all were common laboratory contaminants and were not considered site-related. The pesticides 2,2-bis(para-chlorophenyl)-1,1-dichloroethane (DDD) and 2,2-bis(para-chlorophenyl)-1,1-dichloroethene (DDE) were both detected once at low concentrations. The explosive HMX was detected in one Phase I sample.

Concentrations of several metals, including arsenic, beryllium, barium, copper, lead, nickel, and selenium, were detected at concentrations exceeding screening criteria. However, the SI/RI addendum report concluded that detected concentrations were consistent with concentrations in the Assabet River and that distribution patterns did not suggest that AOC A4 was a significant contributor to sediment metal concentrations.

Summary. Surface and subsurface soil data are consistent with previous dumping of organic chemicals at the site. Elevated concentrations of lead were present at isolated locations. Groundwater data show concentrations of aluminum, iron, and manganese above SMCLs. Although concentrations of metals in SI/RI surface water samples appear high, this is likely the result of high concentrations of suspended matter in the samples. Surface water samples collected during data gap investigations had concentrations of lead which were less than background. AOC A4 does not show widespread contamination and does not appear to be a source of sediment or surface water contamination.

A complete discussion of AOC A4 site characteristics can be found in Section 2.0, of the SI/RI addendum report and the AOC A4 Technical Memorandum.

5.2 AOC A7

Soils. Characterization of soil during the SI/RI included collection of 14 surface soil samples, collection of 53 soil samples from 19 test pit locations, and collection of 27 soil boring and 2 hand-auger subsurface soil samples. In general, these samples were analyzed for TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, and TAL metals. A portion of Phase II samples were also analyzed for organophosphorus pesticides.

At the laboratory waste disposal area soil contaminants exceeding screening criteria were primarily pesticides and chlorinated VOCs. The organochlorine pesticides dieldrin, lindane, DDD, and DDT were detected at concentrations greater than screening criteria. Chlordane, heptachlor, heptachlor epoxide, DDE, and PCBs were also detected. The organophosphorus pesticides Demeton-0, Fenthion, and methyl parathion were also detected at concentrations greater than screening criteria. In the VOC analyses, 1,1,2-trichloroethane, 1,2-dichloroethane, chloroform, and tetrachloroethene were detected at concentrations greater than screening criteria. Acetone, chlorobenzene, ethylbenzene, trichloroethene, and xylenes were also detected. Lead was detected in all 10 subsurface soil samples from this area.

At the solid waste landfill, exceedances of screening criteria for were noted for DDT, DDD, and DDE only in the south-central portion of AOC A7. Within this small area, DDT, DDD, and DDE were detected at concentration above screening criteria. The only other compound detected above screening criteria in this area was the SVOC 2-methylnaphthalene.

In the southeastern portion of AOC A7, exceedances of screening criteria for the pesticides endrin, heptachlor epoxide, and total chlordane were noted in samples from test pit A7TPS. An exceedance of total chlordane was also noted in the sample from soil boring A7B12. Lead was detected in test pit

A7TPS.

SVOCs were detected at concentrations greater than screening criteria at two closely spaced sampling locations in the north-central portion of AOC A7. Chrysene was detected at a depth of 2.0 to 4.0 feet bgs in test pit A7TPE. 2-Methynaphthalene, benzo(a)anthracene, and benzo(a)pyrene were detected at surface soil sampling location A7SO6.

Groundwater. Groundwater sampling during the SI/RI included collection of 30 samples from 10 monitoring wells. Target analytes generally consisted of TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, phosphate, and TAL metals.

Groundwater quality in the vicinity of the laboratory waste disposal area was assessed with data from monitoring wells OHM-A7-8, OHM-A7-45, and OHM-A7-46. The groundwater quality downgradient (north) of this source area was assessed with data from monitoring wells OHM-A7-51 and OHM-A7-52. Exceedances of groundwater screening criteria were primarily noted in source area wells OHM-A7-8 and OHM-A7-46, and in downgradient monitoring well OHM-A7-51. The majority of the contaminants detected in the groundwater were also present at elevated concentrations in area soils.

The pesticides lindane, DDD, and dieldrin and the VOCs 1,1,2-trichloroethane, acetone, carbon tetrachloride, chloroform, and tetrachloroethene, all detected at elevated concentrations in area soils, were also detected in source area groundwater at concentrations exceeding screening criteria. Lead was not detected above screening criteria in any of the monitoring wells.

During the ground water sampling event performed in December 1993, both unfiltered and filtered groundwater samples were submitted for pesticide and PCB analysis for all monitoring wells in, and downgradient of, the laboratory waste disposal area. Pesticides were detected at similar concentrations in both the unfiltered and filtered samples from several monitoring wells.

Groundwater quality downgradient of the solid waste landfill area was assessed with data from ground water samples collected from monitoring wells OHM-A7-9, OHM-A7-10, OHM-A7-11, and OHM-A7-12. An exceedance of the drinking water action level for lead in one sampling round was not confirmed during two other sampling rounds. Lead is therefore not considered to be a contaminant of concern in groundwater in this area. Methylene chloride was detected a total of 5 times in these monitoring wells at concentrations slightly exceeding the MCL. Four of these detections occurred during the October 3, 1991 sampling event, while the fifth occurred during the June 25, 1992 sampling event. None of the methylene chloride detections were confirmed during other sampling events, and SI/RI report considered the positive detections laboratory artifacts. These analytical results indicate that buried solid waste in the central and eastern portions of AOC A7 is not significantly affecting groundwater quality at this time.

Data gap activities to assess contaminant migration in groundwater included installation of three new monitoring wells and collection and analysis of two rounds of groundwater samples from the three new and six existing monitoring wells. Target analytes consisted of VOCs and pesticides. The analytical results showed that contamination with VOCs and lindane did extend beyond the installation boundary, however, comparison of data from existing monitoring wells with previous data indicated that concentrations were generally lower than in earlier samples collected from those monitoring wells.

Surface Water. Characterization of surface water was based on seven surface water/sediment pair samples collected during the SI/RI and two surface water/sediment pair samples collected during earlier studies.

In general, the surface water samples were analyzed for TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, and TAL metals. Phase II samples were also analyzed for phosphorus and organophosphorus pesticides.

VOCs and SVOCs were only detected in one sample collected in 1984. The reported organic compounds were all common laboratory contaminants, and the lack of confirmatory results from subsequent sampling led to the SI/RI conclusion that they are not contaminants of concern in the stream.

Arsenic was detected at A7SW2 and E3-BCK-DO3 at concentrations below the freshwater chronic Ambient Water Quality Criteria (AWQC), but above the human health AWQC. Although arsenic, lead, zinc and aluminum were detected in several surface water samples from AOC A7 and Study Area (SA) P9 at concentrations above USEPA Region I Environmental Services Assistance Team (ESAT) surface water and freshwater chronic AWQC criteria, all concentrations were below maximum background values. Elevated zinc concentrations were attributed to laboratory contamination, as the rinseate blank concentrations were comparable to the field sample concentrations. Aluminum exceeded ESAT criteria at A7SW2 and A7SW3. In general, there were no significant differences in metal concentrations between the upstream and downstream sample locations.

Sediment. Sediment characterization was based on seven surface water/sediment pair samples collected during the SI/RI and two surface water/sediment pair samples collected during earlier studies. Sediment samples were analyzed for TCL VOCs, SVOCs, pesticides, PCBs, chlorinated herbicides, explosives, total organic carbon, and TAL metals. Phase II samples were also analyzed for phosphorus and organophosphorus pesticides.

VOCs were only detected in samples collected during the RI The three detected VOCs (acetone, methyl ethyl ketone, and methylene chloride) are common laboratory contaminants and were not considered site-related contaminants. Several PAHs were detected at one sampling location in 1984. PAHs were not detected in the sediment sample which was collected immediately downstream of that location in 1993.

Pesticides and PCBs were not detected in the sediment samples from AOC A7. DDE and DDT were detected at concentrations above ESAT sediment criteria in one background sample. DDT, DDD, and DDE were also detected at concentrations above screening values in sediment samples collected from upstream locations at SA P9.

Arsenic,…