Mike Horse clean up enters home stretch

Heavy spring rains and runoff had the nascent Blackfoot River churning through its new channel near the Upper Blackfoot Mining Complex Water Treatment Plant Thursday, May 21. Just upstream, the river formed at the confluence of Bear Trap and Anaconda Creeks.

Downstream, water filled the reconstructed side channels and wetlands as the last of the major work to restore the headwaters of the Blackfoot River got underway, with excavators moving woody debris and compost along the new floodplain.

David Bowers, the Montana Department of Environmental Quality project manager for the UBMC cleanup, said they hope to have the bulk of the work wrapped up between late June and the middle of July, with some revegetation work slated for this fall.

Once it's completed, it will end the massive cleanup project that began more than a decade ago, and included six years of waste removal and reconstruction between 2014 and 2020.

Despite the day's blustery conditions and constantly shifting winds, Bowers wasn't worried about the weather or the water.

"I'm really glad this is happening this year and not last year, because we still had waste in the floodplain. We would have been scrambling," he said.

In August 2019, the last of nearly 46,000 truckloads of mine waste pulled on to Highway 200 and headed west to the repository just off Highway 279. In total, between 900,000 and one million cubic yards of mine waste and contaminated material came out of the area.

Last year, crews completed reconstruction of the new river channel and excavation of the floodplain and tied it in with the upper marsh, but cold and snowy weather in October brought an early end to the construction season and forced them to wait until this year to complete the last of the floodplain work.

Glacier Excavating of Eureka will oversee the last of the restoration work. Missouri River Contracting, the company that has been the primary contractor on the project since 2016, will complete work on the remaining floodplain roughening in the areas know as Additive Alternative A and B. The two areas are the last sections of the fourth and final phase of the cleanup and restoration. They extend from the treatment plant downstream to the Upper Marsh near the Edith Mine.

"Roughening" the floodplain with woody debris helps create microclimates for the native vegetation that will be planted this spring and summer under the supervision of the Natural Resource Damage Program. Additional revegetation work should wrap up in the fall.

Several "wildlife tree pods" throughout the area are also designed to help the restoration

"When you've got all the heavy equipment, you really can't leave stuff. You obliterate, grub it out," Bowers said. "They took these snags and just planted them in there. The idea is for the cavity nesting birds to come back in, the insects to come back in. So, not just thinking about vegetation, but how do we give the riparian ecosystem a jumpstart as well."

MRC will also take care of some final landscape work to smooth out the hillside near the confluence of Mike Horse and Bear Trap Creeks. The area, once the site of the Mike Horse community that existed during the Mike Horse Mine heyday, was used as a clean fill source for the reconstruction work.

Just below the Water Treatment Plant, Missouri River workers are also installing a new bridge for the facility. The bridge, funded by a $300,000 grant from the Montana Department of Natural Resources, is designed to pass a 100-year flood and improve fish habitat.

"Once the bridge is in later this summer they will pull the temporary pipes out and restore up stream, downstream and underneath the bridge so it can pass water and fish, the way the restoration folks want it to," Bowers said.

The project was also awarded a $500,000 DNRC grant last year to assess the wetlands downstream of the project area.

From a budget perspective, Bowers said they are close to 'zeroing out," in terms of the money available for the removal of mine waste and the restoration of the area, but he said that doesn't mean they will be entirely out of money for the UBMC.

"We've got the $500,000 trust for the operation and maintenance of the repository. We have another $600,000 we have for monitoring and study we need to do around here. We've got money for the repository itself. When you take all of those out... we're getting really, really close to zero," he said. Nevertheless, he's confident they will complete the project to the existing boundary of the area specified in 2007 under the Engineering Evaluation/Cost Analysis, without the need for any additional funding or grants.

Beyond the EE/CA boundary lies the upper marsh, where Pass Creek flows into the Blackfoot River. The area was originally considered in the cleanup plan, but it is technically Forest Service property beyond the EE/CA boundary. Estimated to contain some 40,000 cubic yards of mine waste, vegetation and wildlife activity has reportedly helped settle and attenuate the contamination there.

During the next few years, the area will be monitored to determine if removing the mine waste there is necessary.

As a result, final closure of the UBMC waste repository is on hold for the next three to five years.

"We are buttoning up the repository this year. There will be a 12-inch soil cap that goes on it, basically the start of the base layer that goes on for closing the repository anyway," Bowers said. That soil layer will be sprayed with a tackifier to help prevent erosion.

If monitoring shows there isn't a need to remove waste from the marsh, the repository will be fully closed with a liner, additional soil and re-vegetation.