Laura Lundquist

(Missoula Current) The first results of potential lumber mill pollution in the Clark Fork River are in, and while the Smurfit Stone mill site might be one source, pollution shows up elsewhere too.

At Thursday’s meeting of the Frenchtown Smurfit Stone Community Advisory Group, Trevor Selch, Fish, Wildlife & Parks pollution control biologist, presented water quality results collected by passive water samplers in local rivers last summer.

While pollution concentration increased near the Smurfit site, pollution spikes were also found in other locations.

“We were looking for dioxins, furans and coplanar PCBs,” Selch said Thursday. “Dioxins are a lot more toxic than the PCB’s. I also looked at the biotic sediment accumulation factor, and what that is is how readily they accumulate in the biota and the fish particularly. Coplanar PCBs are so much more bio-accumulative than the dioxins, so that’s what was really driving the fish advisory.”

Dioxins, furans and dioxin-like PCBs often occur together, the byproduct of pulp, paper or pesticide manufacturing, and can cause reproductive and developmental problems, damage the immune system and cancer in people, fish and wildlife.

The Smurfit-Stone pulp mill produced bleached pulp for 39 years, and the site contains more than a million tons of bleached-pulp waste, which is a source of dioxins and furans. Groundwater and soil samples taken at the site contain dioxins and furans.

After fish were collected in 2018 and 2019 in the Clark Fork River, fish tissue data showed that rainbow trout and Northern pike carried enough toxins that FWP had to issue a new fish consumption advisory. A 2013 advisory cautioned people to avoid eating pike from the river below Missoula and limit trout to four meals a month. The 2019 advisory warned people to avoid all pike and rainbow trout throughout the Clark Fork River from Bonner to St. Regis.

Since then, the state trustees and the Community Advisory Group have been asking the Environmental Protection Agency for more sampling to learn more about whether the Smurfit Stone site is adding to the pollution in the Clark Fork River, which is contaminating fish.

The former Smurfit-Stone mill site. (Laura Lundquist/Missoula Current)
The former Smurfit-Stone mill site. (Laura Lundquist/Missoula Current)
was awarded

So last summer, biologists collected fish and water samples to assess pollution beyond what may be coming from the Smurfit site. Selch said the fish tissue data are not yet available due to quality control procedures, but the data from the passive water samplers are.

In mid-July, technicians deployed passive water samplers in 19 locations from the upper Clark Fork River above Anaconda to the Flathead River near Cabinet Gorge and left them in the water for 30 days. Although they expected to lose some samplers to vandalism or environmental factors, they managed to get 18 back.

Passive water samplers are basically lipid or fat bags with semi-permeable membranes that sample water slowly, so they are better than a one-time grab sample at mimicking how fish absorb pollutants in the water. That’s especially important on free-flowing rivers where the flows change and where pollutants might be released at different times.

When Selch calculated the relative toxicity of the three kinds of pollutants at each site, he found peaks for dioxins and furans on the Clark Fork River downstream from Butte – which had the highest concentration – at Bearmouth and at the Thompson Falls Reservoir.

High readings were also recorded at Harpers Bridge just above the Smurfit site and two locations downstream from the Smurfit site. Peaks also showed up on the Blackfoot River at Scotty Brown Bridge and on the Bitterroot River near Hamilton.

Selch said he could not explain the high readings found upstream of the Smurfit site.


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When Selch looked at PCBs alone, the highest readings were in the Blackfoot River just above the confluence with the Clark Fork and on the Clark Fork River between Paradise and Plains. But there were significant readings just above the Smurfit site at Harpers Bridge with readings increasing downstream to St. Regis that weren’t explained by sources upstream.

“The Blackfoot site is just across from the Bonner mill so maybe there’s a source there. But by the time we get to Missoula, we’re just not seeing any signature,” Selch said.

As the Clark Fork River progresses from its headwaters west toward the Montana border, the river grows as more streams add to the flow. Higher flows can dilute the concentration of pollutants but fish can still be affected. To compensate for the flow, Selch calculated the pollution load – how many pounds of a contaminant is pushed downstream per day – at each site.

“As we move downstream, the flows pick up and the overall concentration may be going down. But when we calculate the load, the load kind of increases as we go downstream,” Selch said.

While it appears that the Smurfit site may be contributing to the dioxins, furans and PCBs in the Clark Fork, Selch said the fish tissue data would provide more information. He hopes to get that information out soon, maybe by the next Community Advisory Group meeting.

In 2021, Jamie Holmes, consulting scientist and vice president of Abt Associates, told the Community Advisory Group that the primary PCB found in the EPA fish samples was PCB 126, the most toxic of 209 congeners. The U.S. banned all PCBs congeners in 1978 after their toxicity and environmental longevity were discovered.

Montsanto was the only U.S. manufacturer and produced a number of PCBs under the trade name Aroclor for almost 50 years.

Contact Laura Lundquist at

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