Dam breach data raises concerns

SANDPOINT — Idaho Department of Environmental Quality officials are poring over monitoring data on the Clark Fork River to determine whether the breach of the Milltown Dam in Montana is sending sediment contaminated by mining waste across the border.

Last week, the Missoulian newspaper reported that research indicates far more of the tainted sediment is moving downstream than was originally predicted.

Citing research data from the University of Montana, the U.S. Geological Survey and operators of the Thompson Falls Dam, the newspaper said an enormous amount of polluted sediment began moving downstream when the combined flows of the Clark Fork and Blackfoot rivers were released for the first time in more than a hundred years.

When the U.S. Environmental Protection Agency approved the dam-breaching plan, the agency acknowledged that there would likely be short-term drawbacks such as fish mortality and muddy waters. But the EPA ultimately concluded the long-term benefits — better fish passage and aquifer restoration — trumped the negative impacts.

But the combined data suggest that the dam breaching is revitalizing part of the river upstream while spreading a plume of mining pollution over a broader area downstream, the article said.

See DATA, Page 3

The dam was breached in March and celebrated as a major step in cleaning up one of the largest Superfund sites in the nation.

However, the owners of the Thompson Falls Dam, PPL Montana, have conducted regular sediment quality monitoring at the hydroelectric project and the results are troubling. Sampling done in May showed dramatic increases in metals concentrations.

Levels of arsenic were 12 times higher than when they were measured last year. Copper levels were five times higher and lead and zinc levels were each four times higher, according to a July 31 letter from PPL Montana's legal counsel to the EPA.

Montana's Thompson Falls Dam is approximately 150 miles below the drained Milltown Reservoir and only 60 miles from the Clark Fork's inflow to Idaho's Lake Pend Oreille.

June Bergquist, regional water quality compliance officer for IDEQ in Coeur d'Alene, said it's not immediately clear how much of the pollution is reaching Idaho. She's been examining monitoring data being collected by the Milltown project's contractor, but hasn't been able to access the EPA's project data because of technical problems.

But both those data sources cover only what's happening in Montana.

Bergquist said on Wednesday she was unaware if increased pollution is being detected in Idaho and referred inquiries to an IDEQ colleague, Bob Steed.

Steed did not respond to a message seeking comment on how the river is being monitored and what, if anything, is being detected.

Bergquist, however, said the dam breach's impact on the Clark Fork in Idaho will eventually become clear.

"We'll be looking at this information and comparing it to our state water quality standards. We'll also compare it to monitoring data that has been collected on the Idaho side over the years," she said.

Regardless of the dam breaching, Bergquist said there's always a load of metals flowing down the river because of upstream Superfund sites.

"If there is a plume of metals coming from the Milltown Dam, it may be hard to pick out of the background if the numbers are low enough. Then we'd have to compare when the dam was breached with our sampling. It's a lot of work to do," she said.

Bergquist added that tainted sediment could end up settling in the Noxon and Hungry Horse reservoirs in Montana. She said the metals tend to bind with the sediment particles, "which cleans up the river a lot before it gets to Idaho."