Water quality study finds toxic compounds more widespread than previously thought in Clark Fork

Preliminary results from water quality testing done last summer on the Clark Fork River released this week show toxic compounds in the river are more widespread than state officials previously thought, which could lead to a reassessment of the fish consumption advisory that has been in place since 2020.

The passive water monitoring study was done at 19 sites in July and August from between where Silver Bow Creek enters the Clark Fork all the way down to Cabinet Gorge Reservoir on the Idaho border, including the Flathead, Bitterroot, and Blackfoot rivers.

The preliminary results show there are toxic compounds in the river – including polychlorinated biphenyls (PCBs), dioxins and furans – that are products of both industrial activities that have historically occurred along the river and natural sources, including wildfires.

Data from fish sampling also done as part of the study is still being analyzed but will be released in the coming weeks or months, Montana Fish, Wildlife and Parks Fisheries Pollution Biologist Trevor Selch said in an interview Tuesday.

Biologists with FWP have been doing surveys on the river since the Smurfit-Stone paper mill north of Missoula near Frenchtown closed in 2010, which led to an initial fish consumption advisory for northern pike and rainbow trout.

FWP then worked with the U.S. Environmental Protection Agency in 2018 and 2019 to expand those surveys, leading to an updated consumption advisory in 2020 that recommended people avoid eating any fish from the Clark Fork between where the Bitterroot River runs into the river down to its confluence with the Flathead River.

That also included revised recommendations for rainbow trout and northern pike on an upper section of the Clark Fork and on the Blackfoot and Bitterroot rivers.

The toxic compounds that biologists are finding in the water and in fish are stored inside the muscles and fat of fish and can be harmful to people who eat them, but can also cause issues within the fish population, Selch said.

FWP said the data have not yet shown a correlation between the toxic compounds and any particular site but that biologists will continue to investigate the sources of them. But runoff from mining and the waste from the paper mill have found to affect the Clark Fork’s water quality in areas.

Last year, the conservation organization American Rivers deemed the Clark Fork one of the nation’s most endangered rivers due in part to the toxic chemicals and compounds that have made it into the river during the past 100+ years.

Selch said some of the highest levels of the toxic compounds were found in Silver Bow Creek, which he said was both surprising and not because of the mining runoff in the area and because the river becomes more voluminous as it moves downstream.

The team also found higher concentrations near Bearmouth between Drummond and Missoula, as well as on the Blackfoot near the Scotty Brown Bridge Fishing Access Site below Monture Creek.

But they also found lower concentrations downstream of Missoula’s wastewater treatment plant, which Selch said was somewhat unexpected.

“Those will have to be more refined in future studies to really figure out where (the toxic compounds) are coming from,” he said. “…There’s definitely going to be more investigation. I think we’re already starting to look into conducting a similar study kind of upstream of our highest site there so we can identify where anything might be coming from in that Butte area as well.”

FWP worked with the Confederated Salish and Kootenai Tribes, Trout Unlimited, Missoula County, the Clark Fork Coalition, and the Natural Resource Damage Program on the project after receiving a $221,000 grant from the EPA.

Once the team gets the fish sample results back, it will analyze them alongside the water sampling to see where higher levels of toxic compounds in the rivers are causing higher concentrations in fish that live in the area, Selch said.

Working with the Department of Environmental Quality and Department of Public Health and Human Services, the teams will determine if they need to adjust the 2020 fish consumption advisory in light of the compounds being found below the confluence with the Flathead River and higher upstream near Butte.

“We’ll be getting that information out to folks and seeing where the bounds of that advisory will be,” Selch said. “The current advisory is a recommendation to avoid all fish. Another advisory might be, you can have X amount of meals per month, two meals per months, five meals per month. So that will also be in place depending on what the final concentrations end up being.”

The group received the grant funding through the Columbia River Basin Restoration Funding Assistance Program in 2022 and had to match the grant with about $83,000 of its own money. Selch said the EPA recently made the grant awards a minimum of $300,000, but getting the matching funds together for another application this year might not be feasible.

“We’ve been pursuing some other avenues,” he said. “DEQ is looking into some potential funding that we can do the level of study we need to in that area (near Butte). And then we’re just really trying to get this data wrapped up and finalized and validated, then the next step, we’ll be having those conversations with all sorts of interested parties throughout the basin.”

Blair Miller is a reporter based in Helena. The Daily Montanan is a nonprofit newsroom.