Cleanup of Midnite Mine on reservation to begin by 2015

Newmont Mining Co. expects to begin cleanup of a defunct uranium mine on the Spokane Indian Reservation by 2015.

The company is working on design proposals for the remediation of the Midnite Mine, which opened in the 1950s to produce uranium for the U.S.-Soviet nuclear arms race. About 33 million tons of radioactive waste rock and ore remain at the 350-acre site above the Spokane River.

The plan is to fill in open pits left from the mine excavations with the waste rock and ore, said Lou Miller, a consultant for Newmont. The pits would be capped to keep radon gas from escaping. Groundwater in the pits will be collected and treated and then piped 7 miles to the Spokane River.

Newmont already collects and treats water at the old mine site, but that water is currently discharged into Blue Creek, a tributary of the Spokane River. Discharging the treated wastewater directly into the Spokane River will reduce the impacts to Blue Creek, where the tribe is working to re-establish a native redband trout run, said Randy Connolly, Superfund director for the Spokane Tribe.

The water discharged into the Spokane River must meet the tribe’s water quality standards for radionuclides, heavy metals and other pollutants, which are stricter than state and federal standards, Miller said. The cleanup work is also subject to permits from the U.S. Environmental Protection Agency.

The cleanup will take about a decade and cost an estimated $193 million. Under a consent decree signed with the federal government last year, Newmont and its subsidiary, Dawn Mining, will pay for most of the work. The U.S. Department of the Interior will contribute $42 million for cleanup activities for failing to fulfill federal trust responsibilities to the Spokane Tribe through proper oversight of the mine during its operation.