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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-98/132
ROD Date:  09/30/1998
Operable Unit(s):  03
Media:  Groundwater, Soil
Contaminant:  Base Neutral Acids, Dioxins/Dibenzofurans, Inorganics, Metals, PAH, Pesticides, VOC
Abstract:  Please note that the text in this document summarizes the Record of Decision for the purposes of facilitating searching and retrieving key text on the ROD. It is not the officially approved abstract drafted by the EPA Regional offices. Once EPA Headquarters receives the official abstract, this text will be replaced.

The Massachusetts Military Reservation (MMR) on Cape Cod, Massachusetts, whose Superfund name is Otis Air National Guard, lies within the boundaries 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 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 stormwater 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.

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, Nation Guard Bureau (NGB), U.S. Coast Guard, and USEPA, was signed in 1991 and updated in 1997. The FFA established a procedural frameword for ensuring that appropriate response actions are implemented and required the Air National Guard to take the lead in the cleanup activities at MMR.

Operable Unit 1 (OU1):
OU1 is the contaminated groundwater plumes at the site. Of the ten plumes, seven have migrated beyond the MMR facility boundary. The plumes are part of the regional groundwater system that underlies the site and Cape Cod.

The seven contaminated plumes migrating beyond the facility boundary are: the Landfill-1 (LF-1) Plume, the Storm Drain-5 (SD-5) Plume, the Petrol Fuel Storage Area Plume (PFSA), the Eastern Briarwood Plume, the Ashumet Valley Plume, the Fuel Spill-12 (FS-12) Plume and the Chemical Spill-4 (CS-4) Plume. Two contaminated plumes that are not migrating off site, but are located near its boundaries are named the CS-10 Plume and the Western Aquafarm Plume. One groundwater Plume, FS-1, was identified in 1995, but the extent of contamination was not known at the time the groundwater Record of Decision (ROD) was issued in September 1995.

The LF-1 Plume contamination has been attributed to the Main Base Landfill, and a former motor pool located immediately to the southeast of the landfill, designated Chemical Spill-9 (CS-9). From 1944 to until 1984 the LF-1 landfill was used as the primary solid waste disposal facility at MMR. After 1970, the disposal at the landfill was regulated. All disposal in the cell ceased in 1984. CS-9 contaminated soils and underground drainage structures were removed during the summer of 1994 as an add-on to the LF-1 capping project. The removed soils were treated using the on-site thermal desorption unit. According to the Remedial Investigation (RI), the LF-1 Plume is moving in the direction of the Town of Bourne water supply wells.

The source of the contamination for the SD-5 Plume is the SD-5A operable unit. This is a point source at the former site of the Non-Destructive Inspection Laboratory (NDIL), where a dry well was located. Waste penetrants, trichloroethene (TCE), other halogenated solvents, emulsifiers, and spent film developers were generated in the testing process at the NDIL. These wastes were discharged to a leaching well behind the NDIL building from 1955 to 1970.

The sources of contaminationidentified for the Western Aquafarm Plume include three OUs. The Western Aquafarm system, located on the western side of the Central Drainage Swale consists of six 25,000 gallon USTs that were used in the 1950s and 1960s to store and transfer aviation gasoline (AVGAS) and JP-4 jet fuel. Use of the Aquafarm was discontinued by 1970. The Eastern and Western Aquafarms operated on the principle of water displacement. Fuel was transferred from USTs to refueller trucks by pumping water into the tanks and displacing the fuel. To refill, fuel was pumped into the tanks, water was displaced and discharged into a 1-acre basin within the Central Drainage Swale. Up to 20 million gallons per year of flushed water may have been discharged to the Swale.

The Eastern Briarwood Plume contamination is believed to emanate from several locations, including the former heat plant and various maintenance shops and hangars. Four potential sources of contamination include the SD-4, CS-14, CS-15, FS-25 Study Areas. Study area SD-4 is a drainage course located on the southeast side of the Flightline Area of MMR. Storm water runoff from the SD-4 study area is collected in a series of ditches, some of which are unlined. The drainage ditches channeled flow to an oil/water separator, which discharged treated water to a ditch and a small wetland area to the south. Unknown quantities of solvents from Hangar 128 were flushed into the storm drain system. A leaching pit in Building 156, Study Area CS-14, received discharge from a room that housed a solvent vapor degreaser. Study Area CS-15 encompasses two buildings (Buildings 202 and 204) and jet engine test stands. Engine testing was performed inside Building 204 from 1949 to 1954. During that time, wastes generated in Building 204 were washed to a floor drain that led to a gasoline trap and then a drainage ditch. From 1954 to 1985, engine testing was performed outside at Building 202. During that period, wastes were reportedly washed off a concrete test pad and onto the ground. Study Area FS-25 is an area of petroleum contamination near Building 167. Study Area FS-25 is an area of petroleum contamination located near Building 167. Possible historical sources of the contamination include heavy equipment maintenance and/or refueling operations, and runoff from the nearby runway. Approximately 2,000 cubic yards of contaminated soil was excavated from FS-25 in 1989. The Eastern Briarwood Plume migrates southward towards Johns Pond, a trout stream and a cranberry bog system.

The origin of the FS-12 groundwater contamination and free product was a reported leak of approximately 70,000 gallons from a section of the Cape Cod Canal Fuel Transfer Line. The leaking section of the pipeline was repaired in 1972. The NGB has initiated remediation of the free product as a Time-Critical Removal Action in 1995.

The CS-10 study area is 38 acres in size and is located near the eastern edge of the MMR property line and west of Snake Pond. The USAF maintained ground to air missiles at the Boeing Michigan Aerospace Research Center located within the CS-10 study area. The CS-10 Plume receives contamination from this facility. A fuel spill occurred at CS-10 in 1985 during the removal of a 25,000-gallon UST. Less than 500 gallons of fuel were reportedly released and soils affected by the spill were excavated and removed from the site.

The Ashumet Valley Plume contamination is reported to be the result of two sources. The sewage treatment plant (STP) is the most likely source of contamination in the past. Fire Training Area-1 was used for activities such as pouring used fuels and solvents onto the ground and igniting the liquid for fire fighting training exercises. The Ashumet Valley Plume has migrated south and reached the Town of Falmouth municipal supply well. The NGB funded two interim remedial measures to address the impact of the Ashumet Valley Plume. The NBG reimbursed the Town of Falmouth for the cost of the Ashumet Valley water supply well, and provided funds to extend the Falmouth municipal water system into the Ashumet Valley neighborhood north of Route 151.

The Petrol Fuel Storage Area (PFSA) was used from 1956 to 1971 to support Otis Air Nation Guard (ANG) training. Up to 1,500 gallons of halogenated solvents; waste petroleum, oil and lubricants; ethylene glycol, and fuel were discharged into the Central Drainage Swale.
A Remedial Investigation (RI) for the Southeast Region Groundwater Operable Unit was performed in 1993 and 1994. The purpose was to identify the nature, distribution, and impact of the contaminants in groundwater in an area encompassing the SD-5, Western Aquafarm, and PFSA plumes, all of which are located in the region near the southeast edge of MMR.

An interim remedial alternative was presented addressing seven contaminated groundwater plumes (LF-1, SD-5, Western Aquafarm, Eastern Briarwood, FS-12, CS-10, and the Ashument Valley) in one of two RODs completed in September 1995.

OU2 is the Area of Contamination (AOC) Chemical Spill Area No. 4 (CS-4) source area located 1.1 miles from the southern MMR boundary on the northwestern side of West Truck Road. The AOC CS-4 groundwater plume extends approximately 11,000 feet from the source area.
AOC CS-4 was operated for the maintenance of military vehicles by the U.S. Army from 1940 to 1946 and by the USAF from 1955 to 1973. Wastes generated and potentially spilled or dumped during this period include oils, solvents, antifreeze, battery, electrolytes, paint, and waste fuel. The base Defense Property Disposal Office (DPDO) maintained a storage yard in the northern portion of AOC CS-4 between 1965 and 1983. Wastes were transported to the DPDO from shops and laboratories operating at MMR. Liquid wastes were stored in containers or tanks in an unbermed area, or deposited in six 5,000-gallon underground storage tanks (USTs) installed to store motor gasoline when the motor pools were operational. The USTs were used until January 1984; in September 1984, the last USTs used for waste storage were emptied and removed. The area has been inactive since 1986.

The interim remedial alternative for containing the AOC CS-4 groundwater plume were presented in a May 1992 Record of Decision (ROD).

OU3 is the AOC Chemical Spill No. 3 (CS-3) occupying approximately 3.5 acres in the south central portion of the MMR. The AOC is the former location of an automobile service and gasoline station.

Hazardous substances may have been introduced to the AOC from 1951 to 1979. Leaded motor gasoline was stored and dispensed, and maintenance operations were performed generating petroleum, oil and lubricant (POL) wastes. These wastes were temporarily stored in an UST, Abandoned Tank (AT-23). In 1985, AT-23 was found to be leaking. The UST and associated petroleum contaminated soils were removed from the site, and a replacement above ground tank was installed. In 1994, three former gasoline USTs (Current Product Tank - 40, 41, and 42) were removed and replaced with above ground tanks as part of the Fuels Upgrade Program in 1994. Approximately 340 cubic yards of contaminated soils were removed from the tank grave, and clean soils were backfilled. Sediment and sludge inside the leaching well were removed during the Drainage Structure Removal Program (DSRP), but the leaching well and associated drainage pipes were not removed because that would cause structural damage to Building 5202.

One of the two September 1998 RODs presented a No Action remedial alternative for OU3.

OU4 is the AOC Chemical Spill Area No. 1 (CS-1) source area located adjacent to the eastern boundary of the MMR and covers about 224 acres of land. The AOC CS-1 lies in the upgradient capture zone for two Town of Sandwhich supply wells: Boiling Springs well Nos. 2 and 3. These wells are approximately three miles downgradient of AOC CS-1.

The AOC CS-1 is made up of several sources of contamination: the Transmitter Building former hazardous waste drum storage area, the buried fuel line and former dumping area near the Transmitter Building, the 4,000-gallon above ground fuel tank, the septic leach field, the former storage building, an alleged dump site east of the Transmitter Building, and a magnetic anomaly west of the Transmitter building.
From 1969 to 1975 hazardous wastes may have been introduced to AOC CS-1. Reportedly, activities including the disposal of waste solvent on the ground and the reported burial of used electrical components, including capacitors and transformers, in a trench south of the Transmitter Building occurred during this period.

One of the two RODs completed in September 1995 presented the No Action remedy for AOC CS-1.

OU5 is comprised of six AOCs: Fire Training Area No. 2 and Landfill No. 2 (FTA-2/LF-2); Petroleum Fuels Storage Area, Fuel Spill No. 10, and Fuel No. 11 (PFSA/FS-10/FS-11); Storm Drainage Ditch No. 2, Fuel Spill No. 6, and Fuel Spill No. 8 (SD-2/FS-6/FS-8); Storm Drainage Ditch No. 3, Fire Training Area No. 3, and Coal Storage Yard No. 4 (SD-3/FTA-3/CY-4); Storm Drainage Ditch No. 4 (SD-4); and Storm Drainage Ditch No. 5 and Fuel Spill No. 5 (SD-5/FS-5).

AOC FTA-2/LF-2 is located west of the southern end of Runway No. 5, and occupies approximately 11 acres and includes a fire training area developed on top of a buried municipal landfill.

AOC PFSA/FS-10/FS-11 is located on the north side of South Outer Road, and has been the main fuel delivery and distribution area for the flightline since the early 1950s. FS-10 and FS-11 occurred at the PFSA in the 1960s. FS-10 was a 2,000-gallon jet fuel spill in one of the pumphouses. FS-11 was an approximate 2,000-gallon fuel spill from overfilling one of the tanks. In 1993, approximately 11 cubic yards of fuel-contaminated soil were excavated. In 1994, four 50,000-gallon USTs were removed from the PFSA. In 1996, heavy rain and a pump failure at the PFSA caused 6,000-gallons of fuel-contaminated water to spill from Building 172. Some fuel discharged to SD-2 south of the PFSA. In response to the spill, 480 cubic yards of fuel-contaminated soil was removed from the PFSA, and 120 cubic yards were excavated from the SD-2 drainage ditch as part of an Immediate Response Action.

AOC SD-2/FS-6/FS-8 extends from the base boundary approximately 2,500 feet south to Ashumet Pond. SD-2 receives runoff water from the PFSA, an aircraft maintenance ramp, and hangars. In the early 1960s, two fuels spills (FS-6 and FS-8) occurred on the aircraft maintenance ramp, resulting in the release of approximately 23,000 gallons of fuel.

AOC SD-3/FTA-3/CY-4 is near the southeastern boundary of MMR and east of the runways in an industrialized area. SD-3 was constructed in the 1950s to receive the discharge from storm drains serving aircraft hangers and several streets west of Granville Avenue and the discharge from the Central Heating Plant. From 1956 to 1958, FTA-3 was used for firefighter-training exercises. Subsequent to these activities, the site was backfilled with construction debris, fill, and coal ash. In 1994, 42,000 cubic yards of material, representing the majority of coal and coal ash at CY-4, were excavated and used as fill below the main base landfill (LF-1) cover system.

AOC SD-4 is a drainage way which lies on both sides of Reilly Road. In the 1950s, SD-4 began receiving stormwater runoff from the runway, aircraft maintenance ramp, aircraft hangars, support buildings, and a fuel pumphouse.

AOC SD-5/FS-5 includes a storm drainage swale and several buildings on the western side of Runway No. 5. In the 1950s, SD-5 began receiving stormwater runoff from a number of sources including the Eastern and Western Aquafarms, the former Nondestructive Inspection Laboratory (NDIL), the Corrosion Control Shop, and the Permanent Field Training Site hangar. In the early 1960s, three refueling aircraft were destroyed in a fire, resulting in the FS-5 fuel spill of up to 15,000 gallons of aviation gasoline (AVGAS). In 1994, the NDIL and the Corrosion Control Shop were demolished and removed, and two 12,000-gallon USTs were removed from the AVLUBE area. In 1994/1995, a total of 17 USTs, including all six 25,00-gallon tanks at the Western Aquafarm, all four 25,000-gallon tanks at the Eastern Aquafarm, and seven 550-gallon tanks associated with water separator control pits were removed. In 1996, the NDIL leaching well and surrounding soil were removed.

One of the two RODs completed in September 1998 addresses the six AOCs in OU5: FTA-2/LF-2, PFSA/FS-10/FS-11, SD-2/FS-6/FS-8, SD-3/FTA-3/CY-4, SD-4, SD-5/FS-5.
Remedy:  No action is considered necessary for Area of Contamination Chemical Spill No. 3 (AOC CS-3).

Estimated Capital Cost: Not documented
Estimated Annual O&M Costs: Not documented
Estimated Present Worth Costs: Not documented
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