mather air force base (ac&w disposal site)


The U.S. Air Force built Mather Air Force Base (MAFB) in 1918 to serve as a flight training school. After World War II, MAFB was the sole aerial navigation school for U.S. military and its allies. In 1958, the Strategic Air Command B-52 squadron was assigned to Mather, a position it kept until 1989. Up to 1993, when it was decommissioned as an active air base under the Base Realignment and Closure Act (BRAC), MAFB's primary mission was training of military personnel. At the time of closure, the base encompassed 5,845 acres, including 129 acres of easements. Most of the base was ruled surplus to the needs of the federal government and has been transferred or leased to various entities, primarily the County of Sacramento. In 1995, Mather Airport was officially reopened as a 2,675-acre cargo airport and another 1,432 acres became the Mather Regional Park. Other areas of the former AFB have been developed for housing, a business park, the Veterans Administration Medical Center, and the Federal Aviation Administration’s Northern California TRACON facility. Environmental investigations began at MAFB in 1982 and continued for several years. A total of 89 areas with significant contamination were identified. Most of these Installation Restoration Program (IRP) sites had contaminated soils/sediments and included fire training areas, drainage ditches, waste pits, oil/water separator sites, spill sites, landfills and a sewage treatment plant. Soils are contaminated from toxic and hazardous materials, such as petroleum, oils, lubricants, solvents and protective coatings used during routine maintenance and operation of Mather. In addition, groundwater is contaminated beneath portions of MAFB with five groundwater plumes identified. One of the groundwater plumes is in the Aircraft Control and Warning (AC&W) Disposal Area, located on the east-central part of the base between family housing and the aircraft alert apron. The AC&W groundwater plume contains trichloroethene (TCE). The AC&W Disposal Area was listed on the National Priorities List (NPL) in July 1987. Another groundwater plume, the Site 7 plume, begins at the southern edge of MAFB and extends off-base; it is associated with the Site 7 Disposal Area. Landfills in the northeastern area of the base are believed to be the source of the Northeast plume that has low concentrations of chlorinated solvents in proximity to two closed landfills. The groundwater plume of greatest concern is the Main Base/Strategic Air Command (SAC) Area plume which is two plumes that have commingled and migrated over a mile offbase. Approximately 10,000 people live within a 1-mile radius of the site, and approximately 60,000 people within a 3-mile radius of the site depend on groundwater for their main drinking water supplies. The entire base was listed on the NPL in November 1989.

Hazardous Ranking Score

29 / 100

A score of 28.5 or higher qualifies a site for the Superfund National Priority List.

Regional Contact

Region 9
Phone: (415) 947-4251

Contact Region



Site Inspection
Preliminary Assessment
Final Listing On NPL

Contaminants & Health Effects

      Endocrine Disrupter
      Reproductive Toxin
      Persistent, bioaccumulative and toxic


        African American
        American Indian and Alaska Native
        Native Hawaiian


        People living
        within a 1 mile radius


        Average Income


        Occupied homes

        Potentially Responsible Parties

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