Yellowstone National Park File

Soda Butte Creek, a tributary of the Lamar River, runs through Lamar Valley on July 13, 2017, in Yellowstone National Park.

Montana environmental officials plan to remove Soda Butte Creek from a list of impaired streams next year, a move that follows major abandoned mine cleanups they say fixed water quality problems there.

Officials with the Montana Department of Environmental Quality said the stream that flows into the northeastern corner of Yellowstone National Park now meets standards for heavy metals that had long tainted it.

The agency keeps an Impaired Waters List that it provides to the Environmental Protection Agency every two years, and DEQ has received preliminary approval from the EPA to scratch Soda Butte from the 2018 version.

“It will be delisted for all metals,” said Autumn Coleman, the manager of DEQ’s abandoned mine lands program, adding that it’s the first time such a thing has happened in Montana as a result of a mine cleanup.

Soda Butte Creek flows past the town of Cooke City and into Yellowstone National Park, where it feeds the Lamar River. Until 1953, the McLaren Mill operated on its banks just outside of the town. The mill processed ore that miners pulled out of a pit in the mountains.

While the mill was in operation, Soda Butte Creek was rerouted and mill waste was dumped behind a primitive dam, creating a tailings pond. The dam leaked, sending acid mine drainage into the creek.

Cleanups in the area began in the late 1990s, after a settlement between the federal government and Crown Butte Mining Inc. The Forest Service removed some of the tailings in the mid-2000s, and DEQ began construction there in 2010.

DEQ pulled out the rest of the tailings and buried them in a repository on a hill above the creek. DEQ also moved Soda Butte Creek back to the center of the meadow and planted vegetation. The entire project cost around $24.5 million and was completed in 2014.

Darrin Kron, a water quality specialist for DEQ, said water sampling shows that the loads of heavy metals in the stream are far below what they once were.

“The data showed that the cleanup made the water in the stream meet all of our metals standards,” he said. “That’s pretty significant.

The state’s list of impaired streams and its water quality report will be released next year and will be available for public comment. EPA will give an official review of the report in the summer or fall of next year, and DEQ expects the delisting to be finalized then.

The cleanup has also had benefits for fish there. Ken Frazer, the fisheries manager for the Billings region of Montana Fish, Wildlife and Parks, said cutthroat have now been spotted in tributaries above the old mill site. Contamination prevented the fish from traveling that far upstream in the system before it was removed.

“Whatever was there was strong enough that fish wouldn’t even pass through the plume area,” he said.

FWP and Yellowstone National Park poisoned the stream in 2015 and 2016 to eliminate non-native brook trout, which compete with cutthroat for space and food. Brook trout had persisted there for years, but Frazer said sampling work this fall turned up no sign of the non-native species.

Yellowstone National Park is also happy with the cleanup and the delisting of a stream that enters its borders. Vicki Regula, a park spokeswoman, said the cleanup serves the park’s larger mission of preservation.

“We’re really proud of this cleanup effort,” she said.

Michael Wright can be reached at mwright@dailychronicle.com or at 582-2638. Follow him on Twitter @mj_wright1.

Michael Wright covers the environment and wildlife issues for the Chronicle.

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