Midnite Mine is an inactive uranium mine on the Spokane Reservation in Wellpinit, Washington. It operated from 1955 to 1981 and was added to the National Priorities List in May 2000. The site includes two open pits, backfilled pits, waste rock piles, and ore stockpiles. Contaminated water drains toward Blue Creek and Franklin D. Roosevelt Lake. The cleanup is organized under one primary remedial operable unit, with the final remedy selected in a Record of Decision issued September 29, 2006.
EPA identified 25 contaminants of concern across multiple media. Metals in surface water include aluminum, cadmium, copper, lead, and zinc, among others. Groundwater contains uranium, manganese, and uranium-234. Sediment holds chromium, radium-226, selenium, uranium, and vanadium, plus other substances. Solid waste contains lead-210, radium-226, and uranium. Radon is present in air. The greatest health risk comes from ingesting or having direct contact with contaminated groundwater, surface water, soil, or sediment. Human exposure pathways posing unacceptable risks are currently being controlled. Groundwater migration has not yet been confirmed as stabilized due to insufficient data.
Dawn Mining Company, LLC, and Newmont USA Limited are responsible for carrying out the cleanup under a consent decree finalized in January 2012. EPA oversees the work in coordination with the Spokane Tribe. The cleanup approach includes excavating mine waste, consolidating materials in lined pits, placing protective covers, and operating a water treatment system. A treatment system already captures contaminated water emerging below waste rock and ore piles. Site preparation began in May 2016. In 2023, crews backfilled the Pit 4 Waste Containment Area with 350,000 cubic yards of mine waste, treated 77.6 million gallons of water, and verified that 222 acres met cleanup criteria. The project employed 101 people in 2023 and logged 125,000 worker-hours with zero lost-time accidents.
Work in 2024 focuses on constructing the Pit 4 cover, building a sub-waste liner in Pit 3, completing a 5.2-mile effluent pipeline, and finishing a new water treatment plant. About 120 workers, primarily tribal members, are expected to be employed. Additional remedial action phases are estimated to run from late 2026 through late 2028. Physical construction is not yet complete, and the site has not been deleted from the National Priorities List. EPA conducts five-year reviews to check that cleanup protects public health. The most recent review was completed in April 2024, and the next is estimated for mid-2028.
Community members can stay involved through the Community Involvement Plan finalized by EPA and the Spokane Tribe, which outlines engagement with tribal members, residents, and local organizations. Weekly and monthly progress reports are available online. Key contacts for questions include EPA's Remedial Project Manager and Community Involvement Coordinator, as well as designated liaisons from the Spokane Tribe. Physical documents can be reviewed at the EPA Region 10 Superfund Record Center in Seattle or at the Alfred McCoy Administration Building in Wellpinit.
