The Massachusetts Military Reservation (MMR) is a 22,000-acre military facility on western Cape Cod. Prior to 1973, the base was used to train National Guard troops, train and deploy troops during World War II, and provide air defense during the Cold War. Presently, the base is home to the Camp Edwards army-training site, the Otis Air National Guard Base fighter squadron, the Massachusetts National Cemetery, and several smaller military and civilian tenants. The Massachusetts National Guard Environmental & Readiness Center is a source for more information about the history and current activities at the MMR.

The MMR overlies the Cape Cod aquifer. The aquifer is composed mostly of sandy, unconsolidated sediment that were deposited at the edge of retreating ice sheets about 15,000 years ago (Masterson and others, 1997). At the MMR, the sediments are 150 to 300 feet thick and overlie crystalline bedrock. The only source of water to the aquifer is precipitation. About 48 inches of precipitation falls annually on western Cape Cod, and about 26 inches per year recharges the unconsolidated sediments; the remainder is lost to evaporation and transpiration. The recharge forms a water-table mound with the highest point, about 70 feet above sea level, on the eastern side of the MMR. Kettle ponds occupy depressions where the land surface intersects the water table. Groundwater flows radially outward from the top of the mound to discharge areas at wells, ponds, streams, wetlands, and the coast (Masterson and Walter, 2000). The average rate of groundwater flow is about 1-2 feet per day.

Military activities, primarily from the 1940s to the 1970s, introduced chemical wastes into the Cape Cod aquifer that formed plumes of contaminated groundwater. The plumes (shown in green on the adjacent map) originating from the northern 14,000 acres of the MMR are mostly from the use and disposal of munitions (Impact Area Groundwater Study Program). The plumes (shown in blue on the adjacent map) originating from the southern 8,000 acres include industrial solvents (predominantly PCE and TCE), fuel compounds, landfill leachate, and treated municipal wastewater. The Installation Restoration Program of the Air Force Center for Environmental Excellence is cleaning up contaminated soil and groundwater for the southern plumes. At the end of 2006, 59 extraction wells were pumping a total of 18 million gallons per day from 11 plumes to remove and treat contaminated groundwater and return it to the aquifer.