Coast Wood Preserving is an 8-acre former wood treatment facility located three miles south of Ukiah, California. It has been on the federal Superfund National Priorities List (NPL) since 1983. The NPL is EPA's list of the most serious hazardous waste sites in the country. Physical cleanup construction finished in 2020, and the site is ready for its anticipated reuse, though it has not yet been deleted from the NPL.
The site has three contaminants of concern: arsenic, chromium, and copper. All three were found in both soil and groundwater. Wood treatment operations left these chemicals behind, and hexavalent chromium in groundwater has been a particular focus of cleanup efforts. EPA organized cleanup under one operable unit covering the overall site.
Cleanup actions started early. In 1981, the North Coast Regional Water Quality Control Board ordered a stop to toxic waste releases. By 1983, the company was pumping contaminated groundwater and had built a slurry wall and interceptor trench to keep contamination from spreading off-site. A formal cleanup remedy was selected in 1989. Soil cleanup in accessible areas finished in early 1990. When the facility stopped operating in June 2018, workers were able to reach previously blocked areas. Between August 2018 and November 2019, about 3,700 tons of contaminated soil was removed. Calcium polysulfide injections have been used to treat hexavalent chromium in groundwater, and follow-up injections will continue until cleanup goals are met.
EPA has determined that human exposure is under control. Contaminated soil is covered with pavement, the site is fenced with posted signs, and a Land Use Covenant restricts groundwater use and limits future development to commercial or industrial purposes. Groundwater contamination is stabilized in its original area, with no unacceptable discharge to surface water. Long-term monitoring will continue to confirm that affected groundwater stays within the contaminated zone.
Community members can stay informed through EPA's ongoing Five-Year Review process. The seventh such review is underway in 2026, and the report will be posted online and sent to EPA's Superfund Records Center at 75 Hawthorne Street, 3rd Floor, San Francisco, CA 94105, by September 30, 2026. These reviews check whether the cleanup continues to protect human health and the environment. Anyone with questions can contact the EPA Community Involvement Coordinator or the Remedial Project Manager.
