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Record of Decision System (RODS)



City & State:  FALMOUTH  MA  02542
EPA ID:  MA2570024487
EPA Region:  01
NPL Status:  Currently on the Final NPL
ROD Type:  Record of Decision
ROD ID:  EPA/541/R-99/104
ROD Date:  08/16/1999
Operable Unit(s):  08
Media:  Sediment, Soil
Contaminant:  Base Neutral Acids, Inorganics, Metals, PAH, PCBs, Pesticides, Petroleum Hydrocarbon, VOC
Abstract:  The Massachusetts Military Reservation (MMR) on Cape Cod, Massachusetts, whose Superfund name is Otis Air
National Guard, lies within the boundaries of the towns of Bourne, Mashpee and Sandwich, and abuts Falmouth,
Massachusetts. The MMR occupies approximately 22,000 acres and consists of several operating command units.
The U.S. Air Force (USAF) managed the base until the end of 1973 when base management was transferred to the Otis
Air National Guard.

MMR is organized into four principal functional areas: Cantonment Area; Range Maneuver and Impact Area; Massachusetts National Cemetery; and Cape Cod Air Force Station. The Cantonment Area occupies 5,000 acres in the southern portion of MMR; this area is the location of administrative, operational, maintenance, housing, and support facilities for the base. This is the most actively used section of MMR. The Otis Air Force Base facilities, including the flight line, are located in the southeast portion of the Cantonment Area. The Range Maneuver and Impact Area occupies 14,000 acres in the northern 70 percent of MMR and is used for training and maneuvers. The Massachusetts
National Cemetery consists of 750 acres along the western edge of MMR and contains the Veteran Administration cemetery and support facilities. The Cape Cod Air Force Station occupies 87 acres of the northern portion of the Range
Maneuver and Impact Area and is known as the Precision Acquisition Vehicle Entry Phased Array Warning System.

MMR activities that had the potential to contaminate the environment included the storage, handling, and disposal of solvents and petroleum fuels, as well as the leakage of these materials into sumps, leaching wells, storm water drainage systems, and the sanitary sewer system. Landfill operations, firefighter training, coal and ash storage, and numerous chemical and fuel spills also resulted in environmental contamination. The year round population is approximately 2,000 with an additional 800 nonresident employees. Intermittent use of the area for Reserve and National Guard activities increases the MMR population by as many as several thousand people. Both, year-round and seasonal residents live in the towns adjacent to MMR. A single groundwater flow system underlies western Cape Cod, including MMR. The aquifer system is unconfined and is recharged by infiltration from precipitation. It has been classified as a sole source aquifer.

The primary drinking water supply for MMR comes from a groundwater supply well located on the base and installed in glacial outwash. The adjacent towns of Bourne, Falmouth, Mashpee and Sandwich also derive their drinking water from supply wells within the recharge area of this aquifer. Falmouth has a reservoir for storage of drinking water obtained from groundwater. The water supply wells at MMR and the surrounding towns range from 40 to 412 ft deep, with the majority of wells extending to depths of 50 to 100 ft below ground surface, in areas where public water supply lines are not available, residents use private wells for domestic water supplies.

In November 1989, the U.S. Environmental Protection Agency (USEPA) placed MMR on the National Priorities List (NPL). A Federal Facility Agreement (FFA) between the Department of Defense, National Guard Bureau (NGB), U.S. Coast Guard, and USEPA, was signed in 1991 and updated in 1997. The FFA established a procedural framework for ensuring that appropriate response actions are implemented and required the Air National Guard to take the lead in the cleanup activities at MMR. In response to environmental contamination at MM., DOD implemented it multiphase Installation Restoration Program (IPR) at MMR, to identify and evaluate problems associated with past releases of hazardous substances. The IPR parallels the USEPA CERCLA investigation and cleanup process. The NGB and subsequently Air Force Center for Environmental Excellence (AFCEE), followed USEPA guidelines for most IRP investigations performed between 1986 and 1989 and for all investigations performed since 1989.

In 1986, an extensive records search and review of available soil and groundwater data identified 73 areas at MMR as having potential for contamination. Four additional areas were later identified through anonymous sources and unrelated base construction projects, bringing the total to 77.
Remedy:  The selected remedy for Area of Contamination (AOC) Chemical Spill-10/ Fuel Spill-24 (AOC CS-10/FS-24) is excavation, on-site asphalt batching, and off-site disposal/in-situ thermally enhanced soil vapor extraction (SVE)/environmental monitoring. The major components of the selected remedy include removal of contaminated surface water from the Eastern Drainage Impoundment at Detail F for disposal at the base wastewater treatment plant or off-site treatment plant; excavation, dewatering (if necessary) and temporary on-site stockpiling of an estimated 3,400 cubic yards of contaminated surface soils and sediments from seven of the nine source areas (Details A through F and I) where contaminants of concern (COC) concentrations in the soils and/or sediments exceed soil target cleanup levels (STCLs); on-site cold-mix asphalt batching of recyclable excavated surface soils and sediments; and off-site disposal of nonrecyclable excavated surface soils and sediments. Confirmatory sampling will be performed during excavation to verify the extent of contamination exceeding STCLs and ensure that all soils and sediments with COC concentrations above such cleanup goals are removed from the source areas. All areas from which contaminated soils and sediments are removed will be backfilled with clean fill. In addition, at Detail C for the in situ thermally enhanced SVE, hot air injection wells, a vapor collection system, and a temporary impermeable cover will be installed. At Details G and H, a confirmatory sampling plan will be implemented. If sampling indicates that COC concentrations at Details G and H are below STCLs, then no further action will be recommended. Because the remedy is a source area remedial action, it does not include a groundwater migration management component; however, groundwater monitoring will occur annually for 5 years to support ongoing groundwater investigations, which will be a part of another report. To evaluate the performance of this remedy, 5-year reviews will be conducted at AOC CS-10/FS 24 to review monitoring and other pertinent data to assess whether the selected remedy remains protective of human health and the environment.

If source area soils and sediments require temporary on-site stockpiling, it will be done in accordance with the Resource Conservation Recovery Act (RCRA) and state hazardous waste storage regulations, which are action specific Applicable or Relevant and Appropriate Requirements for this AOC. In addition, excavated source area soils and sediments will be analyzed by the RCRA Toxicity Characteristic Leaching Procedure (TCLP) to determine whether they are characteristic hazardous waste under RCRA. Soils and sediments that are determined to exceed TCLP allowable concentrations or to contain contaminant concentrations above Massachusetts standards will be disposed in a RCRA Subtitle C treatment storage and disposal facility (TSDF). Soils and sediments that are determined to be below TCLP allowable concentrations and contain contaminant concentrations below Massachusetts standards will be treated at the on-site cold mix emulsion asphalt-batching plant. Remedial activities will also be conducted to meet the standards for visible emissions; dust, odor, construction, and demolition; noise; and volatile organic compounds (VOCs). If these standards are exceeded, emissions will be managed through engineering controls.

In addition, as part of the remedial design, it will be determined whether additional remedial action is warranted with regard to the Building 4606 drainage structures, including but not limited to removal of the drainage structures and all contaminated liquids in the structures, an investigation to determine the source of contamination in the structures and characterize any soil contamination associated with the structures, and excavation and/or treatment of any contaminated soils.

Additional parts of the selected remedy include: backfilling and restoration of excavations (e.g. reseeding grass) using clean borrow material; restoring the wetland at the eastern impoundment to existing conditions or the construction of a compensatory wetland area of similar wildlife habitat value at a nearby location; the performance of a treatablity study (as necessary) to determine whether the final treated product will meet the necessary roadway construction requirements; the use of asphalt-emulsion-coated product as a paving subgrade material at selected locations at Massachusetts Military Reservation (MMR); maintenance of site access restrictions and limit potential human exposure to contaminants, confirmatory sampling at Details G and H; groundwater monitoring; and five year reviews.
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