Tracy Defense Depot is a 448-acre former military site near Tracy, California. Past operations included chemical repacking, pesticide storage, vehicle maintenance, and waste treatment. Those activities left behind a wide range of contaminants. The site was added to the National Priorities List on August 30, 1990, after an initial assessment in October 1986. It remains on that list today.
More than 100 chemicals have been identified as contaminants of concern. Soil and soil gas contain volatile organic compounds including trichloroethene and tetrachloroethene, pesticides such as DDT, dieldrin, chlordane, and heptachlor, heavy metals including lead, arsenic, and chromium, and polychlorinated biphenyls and dioxins. Groundwater holds trichloroethene, tetrachloroethene, carbon tetrachloride, chloroform, and several heavy metals. Surface water and sediment contain DDT breakdown products along with lead and selenium. The site is divided into three operable units covering the overall site, a main groundwater area, and a northwest corner groundwater area.
The U.S. Army and the Defense Logistics Agency lead cleanup under EPA oversight. Work has included groundwater pump-and-treat systems, soil vapor extraction, excavation and disposal of contaminated soils, engineered caps, and institutional controls restricting land use. Twenty-five subsites were declared to need no further action. A soil vapor extraction system in Area 3 was refined in 2021, and by the end of 2022 contaminants there had dropped below cleanup goals. The system was shut down in early 2023 to confirm those levels hold. A gravel cover was placed in the Northern Depot Soils Area in 2016, and a perimeter fence was added in 2023. Indoor air sampling at Building 237 in 2017 and 2018 showed no unacceptable vapor intrusion risks. In 2020, sampling of drinking water wells for PFAS found levels below EPA screening levels at that time.
Human exposure is currently under control and groundwater migration is stabilized. Physical construction of cleanup work is complete across the site. However, the site has not yet achieved all cleanup goals needed for unrestricted future use, and not all required land-use restrictions are fully in place. The most recent five-year review was completed on September 30, 2025. The Defense Logistics Agency continues to operate treatment systems and monitor conditions until all groundwater and soil cleanup goals are met.
Community members can stay involved by joining the Tracy Site mailing list. Contact the Public Affairs Office at (209) 839-4226 or djcpublicaffairsoffice@dla.mil to be added. A Community Involvement Plan updated in October 2020 is available online. Site records are also available for in-person review at the Public Information Repository at 25600 S. Chrisman Road in Tracy. The EPA staff assigned to the site can answer questions as well.
