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11 INITIAL RELEASE DDJC Tracy SUMMARY The Agency for Toxic Substances and Disease Registry (ATSDR) evaluated environmental data and exposure information associated with the Defense Depot San Joaquin (DDJC) Tracy site and determined that DDJC Tracy poses no apparent public health hazard. DDJC Tracy is located on approximately 900 acres, 20 miles south of Stockton and northeast of Lathrop in California's San Joaquin County. The site consists of a 448-acre depot and the 460- acre Tracy Annex. Since 1942, DDJC Tracy has a stored and distributed food, medical, construction, clothing, electrical, industrial, and general supplies. Prior to the early 1970s, wastes, such as pesticides, battery acids, construction materials, embalming fluids, and fuels, were discharged, buried, or burned on site. In the 1980s, groundwater monitoring at the site detected trichloroethylene (TCE) and tetrachloroethylene (PCE) in monitoring wells at levels exceeding the U.S. Environmental Protection Agency(EPA) and California maximum contaminant levels of 5 parts per billion. These compounds had been used as cleaning fluids in the depot's industrial areas until 1976. Additional monitoring indicated that soil and groundwater at the site were also contaminated with other volatile organic compounds (VOCs), pesticides, and metals, and that groundwater contaminated with TCE and PCE had migrated approximately 2,000 feet off site in a northeasterly direction near agricultural and private domestic use wells. Since these findings, representatives from DDJC Tracy have worked with EPA, the California Department of Health Services, and the California Regional Water Quality Control Board to specify the process to be followed in conducting further remedial investigations and to identify cleanup measures. ATSDR evaluated the groundwater, soil, soil gas, and food chain pathways to determine whether people have been, or are being, exposed to site-related contaminants at levels associated with public health hazards. The exposure pathway of principal concern to ATSDR is consumption of contaminated groundwater that might feed into on-site drinking water supply wells, off-site private drinking water wells, and area agricultural wells. ATSDR evaluated data generated from site investigations and determined that TCE and PCE have not been present in on-site water supply wells, off-site private drinking water wells, or agricultural wells at levels likely to pose public health hazards to people who have or who currently use these water supplies. Moreover, it is unlikely that future exposures to groundwater will pose public health hazards because DDJC Tracy installed a groundwater pump-and-treat system that should maintain conditions acceptable for drinking water purposes in areas where wells draw water. ATSDR also evaluated potential exposures that may occur through contact with surface soil, inhalation of soil gas, and ingestion of area crops and fish from an on-site lagoon. ATSDR concluded that any low-level contamination present in these media is unlikely to pose public health hazards. From the review of the potential exposure pathways, ATSDR considers the groundwater, on-site soil, soil gas, and food chain pathways associated with DDJC Tracy to pose no apparent public health hazards. 1