Copper Bluff Mine is an inactive copper and zinc mine on the Hoopa Valley Indian Reservation in northeastern Humboldt County, California. Mining ran from 1957 to 1962, with exploration dating back to 1928. The site was added to EPA's National Priorities List in May 2019, placing it among the country's most contaminated sites that require federal cleanup action. The mine contains more than 2,000 feet of underground tunnels, and a portal entrance sits about 300 feet above the Trinity River.
The main problem is acid mine drainage. When groundwater inside the mine contacts certain minerals, it forms sulfuric acid, which dissolves metals from the surrounding rock. That contaminated water flows out of the mine portal at rates between 5 and 500 gallons per minute depending on the season. The primary contaminants are copper, cadmium, zinc, and iron. These metals are being carried into the Trinity River, which is a federally designated Wild and Scenic River and critical habitat for federally threatened Coho Salmon. People walking a path near the site can come into contact with the acidic water and orange sludge produced by the drainage. A tunnel collapse could also suddenly release large amounts of contaminated water into the river. Human exposure to contamination is not under control, meaning unsafe levels have been detected and people could reasonably be exposed.
EPA is leading the cleanup investigation. A combined remedial investigation and feasibility study began on September 13, 2019, for the site's single operable unit. This work will determine how far contamination has spread and evaluate possible cleanup options. No remedy has been selected yet, and construction of any cleanup action has not started. EPA is monitoring the drainage rate and seasonal patterns to better understand contamination sources and inform next steps.
Community members can get involved by contacting EPA's Community Involvement Coordinator to sign up for notifications. EPA conducts outreach through tribal council presentations, community information booths, direct mailers, fact sheets, and email updates. A Community Involvement Plan was developed with input from community members and local organizations. Public documents related to the site are available at the Kim Yerton Memorial Library at 370 Loop Road in Hoopa and at the Hoopa Tribal Environmental Protection Agency at 12 Cannery Road in Hoopa.
