This 15-acre Superfund site sits at the edge of the UC Davis campus in Davis, California. It covers two distinct areas: one used by the U.S. Department of Energy (DOE) for low-level radiation studies on animals from the 1950s through the mid-1980s, and one where the University of California, Davis (UCD) disposed of campus waste in three landfill units from the early 1940s until 1967. The site was added to the National Priorities List (NPL) in May 1994 and has been in active cleanup for more than three decades.
Contamination varies by area. The DOE area contains radioactive substances including radium-226, strontium-90, carbon-14, and cesium-137 in soil, along with polycyclic aromatic hydrocarbons, chromium, mercury, and other chemicals. The UCD area has groundwater contaminated with chloroform, hexavalent chromium, nitrate, 1,2,3-trichloropropane, 1,2-dichloropropane, and 1,4-dioxane. Soil and soil gas in the UCD area also contain volatile organic compounds, heavy metals such as lead, cadmium, and mercury, pesticides including DDT and its breakdown products, and other industrial chemicals.
For the DOE area, EPA issued a cleanup plan in 2009 calling for institutional controls and monitoring. DOE had already excavated about 8,500 cubic yards of contaminated soil and debris between 1996 and 2002, sending most of it to licensed radioactive waste disposal sites in Washington and Utah. That cleanup work was completed in October 2016 and is now in operation and maintenance status. For the UCD area, EPA's cleanup plan calls for multi-layer caps over the three landfills, drainage systems, and restrictions on future land use to keep out residences, schools, and hospitals. EPA and UCD are also studying groundwater treatment options, including pilot projects to speed up biodegradation of certain contaminants and to test chromium removal by groundwater extraction. Cap design finished in September 2023, and construction is expected to run from October through December 2027.
Human exposure across the entire site is currently under control, meaning EPA has found no unacceptable exposure pathways. Contaminated groundwater is also stabilized within its original area and is not discharging to surface water at unacceptable levels. Even so, physical construction is not yet complete sitewide, and the site remains on the NPL. The most recent five-year review was completed in August 2021, and EPA will continue monitoring to confirm contaminated groundwater stays in place.
Cleanup is being carried out under an agreement among EPA, the California Department of Toxic Substances Control, and the University of California. Community members with questions can contact EPA's Community Involvement Coordinator or Remedial Project Manager directly.
