The Otis Air National Guard Base/Camp Edwards site covers approximately 22,000 acres and is more commonly known as the Massachusetts Military Reservation (MMR). Although the occupants and property boundaries have changed several times since MMR was established in 1935, the primary mission has always been to provide training and housing to Air Force and/or Army units. A review of past and present operations and waste disposal practices identified numerous potentially contaminated areas, including several areas located on the southern portion of MMR. These contaminated areas are the result of historic chemical/fuel spills, fire training activities, landfills, and drainage structures. Additionally, effluent from the former sewage treatment plant was historically discharged into sand beds where it seeped into the groundwater. In 1984, the U.S. Geological Survey detected contaminants in monitoring wells down gradient of this former plant. In 1983 and 1984, the Air Force detected volatile organic compounds (VOCs) in on-site monitoring wells near the Base Landfill and a Fire Training Area. Monitoring had also detected VOCs in several hundred private wells (all of which are now on municipal water) and in one town well (which is shut down). Numerous remediation projects addressing both the soil and groundwater contamination at MMR have been implemented since the mid to late 1990's. Approximately 100,000 tons of soil have been treated at MMR, while to date, there are numerous treatment plants in place which treat approximately 10.6 million gallons a day of contaminated groundwater.