Midnite Mine Cleanup Progresses

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Published: Thursday, 15 February 2018 17:57

After years of development and negotiation, remedial actions to cleanup Midnite Mine are progressing. The former uranium mine, which is located on the Spokane Indian Reservation, operated from 1955 to 1981 and covers over 320 acres. Radioactivity and heavy metals are among the human health and environmental risks being addressed.

The 2016 Midnite Mine Basis of Design Report identifies the project as a multi-year remedial design with construction activities expected to be completed in 2025. Remedial activities include backfilling two open pits with approximately 18 million cubic yards of mine waste rock and other affected materials which are part of the legacy mining operations.

Backfill operations began with the Pit 4 facility in 2016 and will continue this next construction season. Past Pit 4 operations included the implementation of highwall stabilization, dewatering, sediment removal, drain rock crushing, well installation, and drain rock placement. Over the next several years, waste rock and other materials placement in Pit 4 will be completed. The backfilled pit will be capped with clean soil and revegetated. While these activities are completed, remedial actions will be conducted preparing Pit 3 for backfill.

During 2017, EPA completed permitting of a new National Pollutant Discharge Elimination Permit (NPDES) for a new water treatment plant which will discharge treated water to the Spokane Arm of Lake Roosevelt. The plants development schedule calls for design in 2018, construction in 2019, and commissioning in 2020.

To conduct activities safely, many additional measures such as stormwater management, dust suppression, air quality monitoring, and water sampling are part of construction activities.

The project has been advanced from years of development and negotiation. A 2012 agreement makes EPA responsible for oversight of cleanup work in coordination with the Spokane Tribe.