Movement on the Mike Horse 

If everything goes according to the schedule released last week by the U.S. Forest Service, work on the infamous Mike Horse Dam, near the headwaters of the Blackfoot River, could finally begin next summer.

In 1975, floodwaters breached the tailings impoundment at the Mike Horse mine near Lincoln, releasing metal-bearing tailings that flowed 10 miles downstream, covering the stream bed, poisoning the water and destroying the native westslope cutthroat trout fishery in the upper river.

Now, more than 30 years after the disaster, and little more than a year after the Forest Service released a report describing the dam as “a compromised structure” that should be removed from service, the agency last week released a draft describing potential courses of action and a timeline for dealing with Mike Horse once and for all.

The six alternatives range from leaving the dam alone to what Clark Fork Coalition Conservation Director Matt Clifford calls the “Cadillac version,” which includes full removal of the dam and all the toxic tailings behind it.

“Given the circumstance, the timeline is the best we could have hoped for,” says Clifford, referring to the fact that the company responsible for the cleanup, former copper giant Asarco, filed for Chapter 11 bankruptcy protection last August.

Asarco was supposed to begin preparing two environmental and engineering cost assessment (EECA) studies last fall (the documents would provide a road map for cleaning up the mess and determining how much it will cost), but the process has been held up by the bankruptcy.

According to Amber Kamps, Lincoln district ranger for the Helena National Forest, a bankruptcy trustee recently released $80,000 to fund the EECA. An additional $20,000 was set aside to cover any emergency actions necessary to prevent a repeat of the 1975 disaster. It remains unclear who is going to pay for final cleanup of the dam.

Clifford says the only viable option is total removal. “You can dink around with trying to shore it up and patch it,” he says. “But as long as we keep that huge mass of tailings up there, sooner or later it’s at risk of moving downstream.”

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