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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-00/005
ROD Date:  02/18/2000
Operable Unit(s):  09
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 is a comprehensive response to the Chemical Spill (CS)-4, CS-20, CS-21, and Fuel Spill (FS)-13 plumes in the Southwest Operable Unit (SWOU). The selected remedy will aggressively capture the CS-4, CS-20, and CS-21 plumes through axial extraction. These plumes contain approximately 95 percent of the total contaminant mass in the SWOU. The selected remedy calls for limited action with monitoring and institutional controls for the FS-13 plume. The contaminants remaining within the FS-13 plume are immobile and can be allowed to safely remain in place until they naturally degrade. The selected remedy for the CS-4 plume is Alternative 6 (Three New Extraction Wells, Expanded Treatment Capacity in Combination with CS-20 Plume Treatment). This remedy includes the discontinued operation of the existing CS-4 plume extraction well fence, which partially captures the plume, and install new extraction wells along the axis of the plume. Extracted water will be treated at the existing CS-4 treatment plant and discharged at the existing CS-4 infiltration gallery. If additional treatment capacity is necessary, water will be sent to a granular activated carbon treatment plant and discharge system that will be constructed to clean up the CS-20 plume. The remedy includes both monitoring the plume and performance monitoring of the treatment system. Alternative 5 (Extraction, Treatment with Granular-Activated Carbon and Reinjection for Plume Capture) is the selected remedy for the CS-20 Plume. This remedy includes design, construction, and operation of an ETR system to hydraulically capture and treat plume contaminants. Also included in this alternative are long-term monitoring of the plume, performance monitoring and evaluation of the treatment system, and ecological sampling to monitor the impacts of the system on the environment. Water that is treated using the granular-activated carbon treatment plant will be discharged to infiltration galleries.

The selected remedy for CS-21 is Alternative 11 (Extraction, Treatment and Reinjection for Expedited Cleanup (ETR)). The modeled system includes five axial extraction wells pumping a total of 1200 gallons per minute, and a separate leading edge extraction and reinjection well pair and treatment system processing 200 gallons per minute. The selected remedy is capable of hydraulically capturing and treating the CS-21 plume; the high pumping rates will result in an expedited cleanup schedule. Alternative 2 (Limited Action w/Institutional Controls) includes three distinct components. These components include conducting periodic sampling of monitoring wells in and downgradient of the FS-13 plume to monitor the natural degradation of plume contaminants. Monitoring would continue until levels of fuel-related constituents are no longer detectable at concentrations greater than risk-based threshold concentrations. Institutional controls compose two parts of the selected remedy. Institutional controls to prevent the use of groundwater contaminated with FS-13 plume contaminants. Additional institutional controls to prevent the use of contaminated groundwater in the event that the land above the FS-13 plume is sold or transferred while unacceptable concentrations of contaminants remain.

Costs Associated w/ CS-4 Plume Selected Remedy:
Capital Cost: $1,600,000
Annual O&M Costs: $310,000
Total O&M Costs: $3,100,000
Present Worth Cost: $5,400,000
O&M Duration: 12 yrs Discount Rate: 7%

Costs Associated w/CS-20 Plume Selected Remedy:
Capital Cost: $6,600,000
Text:  View full-text ROD [ 2.17M ]
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