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Fish population in upper Clark Fork River in steep decline
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Fish population in upper Clark Fork River in steep decline

Concern over the cleanup of slickens

In this photo taken in August 2018 a barren moonscape created by old mine and smelting waste is one of several along the headwaters of the Clark Fork River near Warm Springs. 

With only 82 brown trout found in an upper reach of the Clark Fork River this past spring, a state official says the reach is 32 times lower in brown trout population than at its peak in 1985.

Nathan Cook, fish biologist for Montana Fish, Wildlife & Parks, said that the population decline has only occurred upstream of Deer Lodge. FWP conducted the fish survey in the spring of 2019 for 1.6 miles from the Clark Fork River’s confluence with Warm Springs Creek. During that survey, fish biologists found 82 brown trout.

But in 1985, that same portion of the river held 2,615 brown trout, Cook said.

During a meeting in Deer Lodge earlier this week to discuss the future of Warm Springs Ponds, Cook said that FWP has seen fish populations decline in the upper Clark Fork since 2013.

“What’s different in the river since 2013?” Cook asked. “Remediation and the removal of vegetation.”

The state-led remediation of the upper Clark Fork River has been an ongoing project for years. Joel Chavez, Department of Environmental Quality project manager for the work, said the remediated sections of the river will take time to heal and become healthy fish habitat.

“We have new banks, there’s no vegetation on those banks, no shade and no undercuts,” Chavez said. “The habitat has disappeared due to the remedy.”

But, he said, those are, ultimately, short-term aches and pains for the river. In the long run, the river will be healthier once the remediation is complete. The question is how long will that take. The cleanup has run into difficulty. DEQ had to stop cleanup work for two years, from 2016 to 2018, because of the amount of money the first few phases cost.

Chavez said the DEQ is “working on some things that will speed up the overall remedy," and he declined to estimate how long the DEQ cleanup will likely now take. The DEQ has been dogged by the high cost of the work and the fact that it received $95 million from Atlantic Richfield Company in 2008. That money has not been enough. 

Cook said habitat simplification is not the only issue, though it could be a contributing factor. Another contributor to the problem are slickens — concentrated deposits of mine waste — behind berms that are now failing along a stretch of river.

Will McDowell, Clark Fork Coalition restoration director, says his nonprofit group thinks the slickens could have been causing fish kills for a while now. But because of their location on the river, if there were fish kills in the past, no one found the dead fish.

The state found 32 dead fish in a stretch of the upper Clark Fork from Galen Road to Perkins Lane last month. The slickens and the failing berms were blamed for that incident.

The slickens, which are bluish-green in color, are high in copper. Fish can’t handle very much copper.

McDowell said Atlantic Richfield Company built the berms in the 1980s and 1990s to prevent runoff from the slickens during thunderstorms.

“The berms were probably not meant to last very long; everyone thought the cleanup was coming soon,” he said.

Now with the berms in failing condition, channels are cutting through them. They are also washing away, allowing thunderstorm runoff to send pulses of heavy metals into the river, McDowell said.

For the last year, the DEQ has been removing mine and smelting waste along the Clark Fork River at Grant Kohrs Ranch. The ranch, a National Historic Site, is 20 miles downstream of where the slickens are located.

But, due to a preceding agreement, the state leapfrogged from a section near the beginning of the river to the Deer Lodge-located ranch, which is open to the public. Chavez said he can’t reveal specifics yet, but the DEQ plans to head back up river next year and the berm and slicken areas will be targeted for work.

“That place is our next home,” Chavez said. “We’ll get every bit of it (the mine waste). We’re going to get all the slickens and all the berms.”

Cook said a really good test of what’s happening will be how many fish the agency finds in the upper Clark Fork during its annual fish survey in 2021.

That’s because FWP can estimate, based on flow conditions in one year, what the fish population will look like three years later. The year 2018 was a good flow year, Cook said.

“Based on the 2018 flow year alone, the fish numbers should get quite high,” Cook said. “If they don’t, then we know something is going wrong.”


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Environmental and natural resources reporter for the Montana Standard.

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