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Proposal To Expand East Boulder Mine Waste Storage Moves Forward

Montana is getting ready to green light the proposed expansion of a waste-holding pond at a mine in south central Montana.

The Custer Gallatin National Forest and the Montana Department of Environmental Quality (DEQ) issued a final assessment Friday for construction that could extend the East Boulder platinum and palladium mine’s life by six years and increase the permitted disturbance area by roughly 40 acres.

Stillwater Mining Company has proposed building up the mine’s waste storage pond, which contains byproducts like nitrogen. The company is required to maintain pre-development levels of water nutrients at the East Boulder River watershed, where the site is located.

DEQ’s Dan Walsh says expansion would increase the height of the impoundment walls by up to 14 feet.

“If you think of the way you build a pyramid, you’re gonna continue to build the sides of it, and it keeps getting taller as you build that. So, ultimately with a tailings impoundment, they have to keep building the sides up in order to put more in the middle of it," Walsh said.

The project expansion may include relocating supporting buildings and infrastructure, including two pump houses, access roads and a pipeline. DEQ says it could issue its official decision sometime in the coming days or weeks.

Copyright 2020 Yellowstone Public Radio

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