concord naval weapons station


Naval Weapons Station (WPNSTA) Concord (also known as Naval Weapons Station Seal Beach Detachment,Concord) is a 12,800-acre site located in the north-central portion of Contra Costa County. WPNSTA Concord is comprised of two geographically separate units, the Inland (5,170 acres) and Tidal (7,630 acres) Areas, and a radiography facility (approximately 1 acre) in Pittsburgh, California. Aside from typical administrative and support work activities, this facility is a major ammunition transshipment port of the West Coast for the Department of Department of Defense, under operation by the Department of Army. The Navy's Installation Restoration Program (IRP) identified 32 areas potentially containing hazardous substances. The Tidal Area is organized into two site groups or Operable Units that include the Tidal Area Sites and the Litigation Area Sites, and the Army is taking over the responsibility for cleanup from the Navy for this area. The Tidal Area Sites are represented by the Tidal Area Landfill (Site 1), the R-Area Disposal Area (Site 2), the Wood Hogger Area (Site 11), the Froid and Taylor Road Area (Site 9), and the Taylor Boulevard Bridge Disposal Area (Site 30). The Litigation Area is represented by four Remedial Action Sub-Sites (RASSs), that contain the original seven IR Sites (Sites 3, 4, 5, 6, 25, 26, and 28), and geographically includes a recently added Former N-P-K Fertilizer Plant Site (Site 31)(formerly Area of Concern-1). The contamination in the Tidal Area Sites, located in wetlands and low-lying areas in the northwestern portion of the facility, comes from past on-base waste disposal practices, including an estimated 3,000 tons of mixed wastes that were deposited in the landfill from the early 1940s to 1979, material and waste generated during the repackaging of conventional munitions, and chipped wood contaminated with pentachlorophenol (PCP). Investigations identified heavy metals to be the primary contaminants in these sites, but low levels of organochlorine pesticides, such as DDT and its breakdown products, and semi-volatile organic compounds (SVOCs) are also present. The contamination in the Litigation Sites, located in both wetlands and upland habitat on the northeastern portion of the Tidal Area, was the result of private industrial activities on portions of property that was subsequently purchased by the Navy to create a buffer zone for the activity at the facility's piers. Soil sampling that started in 1986 detected metals in these areas. Subsequent testing confirmed this result and expanded the areas impacted. Documented historical releases from industrial operations and tidal action in the wetlands transported and distributed contamination across wetlands and into engineered Mosquito Ditches and Lost Slough, a natural tidal channel. The Tidal Area Sites and Litigation Sites are located in critical habitat for endangered species, such as the Salt Marsh Harvest Mouse and the California Clapper Rail. Suisun Bay supports extensive sport fishing as well as providing habitat for the endangered fish species, Winter-run Chinook Salmon and Delta Smelt. Other areas of environmental concern are located in the Inland Area, which is still being addressed by the Navy, and include an expanded Site 22 (Building 7SH5 and Main Magazine Area) where elevated arsenic has been detected across wide areas in shallow soils, the Solid Waste Management Units (SWMUs) Sites 2,5,7, and 18, where industrial activity, such as waste storage, has resulted in contamination of soil and groundwater by volatile organic compounds (VOCs), and Former Ordnance Burn and Fire Training Area (Site 13) where low levels of perchlorate have been detected in groundwater and surface water. In November 2005, WPNSTA Concord was recommended for partial closure and realignment under the Base Realignment and Closure (BRAC) process. The final BRAC determination that was made resulted in approximately half of the facility (Tidal Area) transferred to the Department of the Army in 2008 and the remaining portion (Inland Area) being closed, transferred, and redeveloped.

Hazardous Ranking Score

50 / 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
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        People living
        within a 1 mile radius


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        Occupied homes

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