Black Butte Mine sits near Cottage Grove, Oregon, where mercury mining ran from the late 1880s to the late 1960s. The site was added to the National Priorities List (NPL) in March 2010. NPL is the federal government's list of the most serious uncontrolled hazardous waste sites in the country. EPA has divided the site into four operable units covering the former mine, surrounding lands, a pathway to Cottage Grove Lake, and the lake itself.
Mercury is the main contaminant of concern, along with arsenic and other toxic metals. These pollutants are found in mine tailings, furnace wastes, soil, sediment, surface water, and groundwater. Heavy rain and high stream flows move contamination downstream through Furnace Creek and Garoutte Creek and into the Coast Fork Willamette River and Cottage Grove Reservoir. Inorganic mercury from the mine converts to methylmercury, the form that builds up in fish tissue. The Oregon Health Authority has issued a fish advisory for the area.
EPA completed an early removal action in 2007, regrading the main tailings pile and capping contaminated soils. Field investigations ran from 2012 to 2017 to track mercury movement downstream. In 2018 and 2019, EPA excavated mercury-containing tailings and soils from the Furnace Creek area and placed them in an on-site repository. EPA completed the remedial investigation for the former mine site in 2020. Removal actions continued through 2022 at multiple locations.
The health risk picture is mixed. Exposure pathways that could pose unacceptable risks are currently being controlled in the short term. At the same time, EPA has determined that human exposure is not yet fully under control across the entire site, meaning unsafe contamination levels have been detected and people could potentially be exposed. Groundwater migration is under control, with no unacceptable discharge to surface water. Physical construction of the full cleanup is not yet complete, and the site is not ready for its anticipated future use. Feasibility studies for the former mine site and the pathway to Cottage Grove Lake are both estimated to finish between August and October 2028.
Community members can stay involved through EPA's Community Involvement Plan. Public meetings are announced online, by email, and in local newspapers. Two EPA contacts and one Oregon Department of Environmental Quality (DEQ) contact are available to answer questions about the site.
