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NPL Site Narrative for Concord Naval Weapons Station

Concord, California

Federal Register Notice:  December 16, 1994

Conditions at Proposal (February 7, 1992): Concord Naval Weapons Station is located in the north-central portion of Contra Costa County, California. Approximately 30 miles northeast of San Francisco, it is bordered to the north by Suisun Bay and to the south and west by the City of Concord. The facility encompasses over 12,800 acres in three separate holdings: the Inland Area (6,150 acres), the Tidal Area (6,650 acres), and a radiography facility in Pittsburg, California. On-site activities also include administrative and support work. Transshipment operations are centered on the wetlands bordering Suisun Bay (Tidal Area). Wastes generated on site from base operations have been disposed of in the Tidal Area since base operations began in 1942.

The Navy's substantial investigations of the station have identified 19 sites to be investigated under the Installation Restoration (IR) program, of which 8 are located in the Tidal Area. In addition, 24 Solid Waste Management Units (SWMUs) will be investigated, pursuant to RCRA, 4 of which are located in the Tidal Area.

The Tidal Area Landfill, R-Area Disposal Site, and the Wood Hogger Site are wetlands in the western portion of the Tidal Area contaminated from on-base waste disposal. The 20 acre site was a major disposal area from 1944 to 1979 and received an estimated 33,000 tons of waste. Materials and waste generated during the segregation of conventional munitions were discarded in the R-Area Disposal Site. At the Wood Hogger Site, wood contaminated with pentachlorophenol (PCP) was chipped and placed in an adjacent wetland. Another potential wetland area of concern is the Froid and Taylor Road site. Chemical analytical data identified hazardous substances including zinc, copper, cadmium, lead, arsenic, naphthalene, and methylene chloride, in soil, sediment, or surface water.

The Kiln Site and the K-2 Area are wetlands in the eastern portion of the Tidal Area. They were contaminated as a result of private sector industrial activities, and were subsequently purchased by the Navy to create a "buffer zone" for base operations. Soil sampling in these areas in 1986 detected zinc, copper, lead, cadmium, and arsenic. High tides inundated the sources, carrying contaminants to Suisun Bay. Elevated levels of copper, zinc, lead, and arsenic were detected in surface and composite soil samples in the K-2 Area.

The contaminated areas are critical habitats for the salt marsh harvest mouse, a Federally endangered species. The black California rail, a candidate Federally endangered species, and the California clapper rail, a Federally endangered species, inhabit adjacent wetlands. Suisun Bay supports extensive commercial and recreational fishing and is a habitat for the Winter-run Chinook Salmon, also a Federally endangered species.

Status (December 1994): Workplans for the Tidal and Inland Areas have been completed and approved. Field sampling occurred in the Tidal Area in 1994 and is planned for the Inland Area in the spring of 1995. RCRA solid waste management units will also be sampled in 1995. Those requiring clean up will be folded into the CERCLA remediation.

The Navy conducted a removal of sediments in the Litigation Area in 1994. A post removal ecological assessment is also planned for 1995.

For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet at ATSDR - ToxFAQs (http://www.atsdr.cdc.gov/toxfaqs/index.asp) or by telephone at 1-888-42-ATSDR or 1-888-422-8737.

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