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State officials cleaning up mining waste in the upper Blackfoot Valley are taking a “pause” to evaluate funding and next steps going forward.

Major cleanup of the Mike Horse Mine tailings impoundment has been ongoing for the last few years, led by the Montana Department of Environmental Quality working with the U.S. Forest Service and Montana Department of Justice. The project calls for removal of nearly a million cubic yards of contaminated material, trucked down U.S. Highway 200 to a repository off of U.S. Highway 279.

Cleanup in the Upper Blackfoot Mining Complex is funded through a roughly $39 million settlement with former site owner Asarco. There is $11.4 million remaining.

Due to some unanticipated expenditures, officials are looking at potential design modifications to finish the project and still comply with laws and regulations.

“I think with any remediation process there’s always something like this at the tail end of the project when we really know what needs to be completed,” said Jenny Chambers, DEQ Remediation Division administrator.

Four main expenses were unanticipated as needing funding in the Asarco settlement.

In the planning stages engineers determined that the original repository site was unsuitable, which meant additional analysis and purchase of the current Highway 279 site.

Secondly, the road to the impoundment was too dangerous to run the caravan of heavy dump trucks and other machinery, necessitating construction of a second road.

A third major expense came in 2011 when heavy spring runoff brought serious concerns that the dam holding back nearly 800,000 cubic yards of tailings could fail.

In 1975, part of the berm on the impoundment collapsed due to heavy rain. Between 100,000 and 200,000 cubic yards of mining waste washed down the Blackfoot River, causing an environmental catastrophe that killed much of the aquatic life for miles.

Concerned that it could fail again, officials brought in pumps and pumped water to the tune of about $500,000, said DEQ construction manager Shellie Haaland.

More recently officials discovered a two-inch pipe running under a water treatment pond. The pipe was undocumented and found to be releasing contamination, leading to the decision to move the pond down drainage.

An on-site water treatment plant operates from separate funding, and has seen cleaner water coming into the facility as the project progresses, Haaland said, including using fewer chemicals to treat water and potential plans to go without treatment during the winter.

“All of that was really good news up until the earthquake,” she said.

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Exactly what happened deep underground is unknown, but what officials do know is that a pulse of contaminated water has come into the treatment plant. Haaland and others theorize that the network of underground mine workings saw its share of collapses over the years, and one collapse likely segregated a pool of contaminated water. When the 5.8 magnitude earthquake hit earlier this summer, they believe it allowed that water to discharge.

“We’re hoping (water quality) will equilibrate, but the remediation itself has been successful and we’re very happy about that,” Haaland said.

Working in a mountain valley in the shadow of the Continental Divide brings its challenges. Volatile weather, wildfire potential and the relatively remote location can be difficult and hazardous.

A month of heavy rain last year left tailings saturated and unable to be safely stored in the repository, so contractors stockpiled material until it dried this year.

Remaining work includes removal of additional waste including in downstream wetlands, closing the repository and final restoration of both the formerly contaminated valley and repository site. New contracts going out estimate completion at another two to three years.

“What we do with that $11.4 million – we’re making sure we have enough funding left and that’s where we’re taking this pause to determine what our priorities are and what contingencies might arise because we can no longer absorb those (costs) in the project,” Chambers said.

But even with Montana’s long winters to contend with, DEQ and contractors have brought the valley once filled with contaminated tailings to a natural layout where eventually Bear Trap Creek will flow freely and cleanly.

Chambers noted any decisions or project modifications must also align with ecological requirements, engineering standards and federal obligations. As officials analyze those next steps, she is optimistic that the support is there at both the state and federal level to see the project completed and successful.

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Tom Kuglin Helena Independent Record​

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Natural Resources Reporter

Natural Resources Reporter / Assistant Editor for The Independent Record.

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