PacifiCorp outlines cleanup details at Bigfork hydroelectric facility

There’s more work to be done cleaning up contaminated soil in the Swan River near the Bigfork powerhouse.

PacifiCorp, the owner of the Bigfork hydroelectric facility, recently submitted a voluntary cleanup plan to the Montana Department of Environmental Quality. The plan outlined the levels of contamination left in the Swan River and adjacent riverbank after decades of leaking electrical transformers and other chemical uses at the facility.

The plan that PacifiCorp recently submitted to the DEQ is a voluntary one, but it must meet state levels of allowable contamination. The state outlined dozens of additional requirements that PacifiCorp must comply with in the cleanup.

The transformers used at the site contained polychlorinated biphenyls, or PCBs, which leaked from the transformer station into the adjacent soil and waterway. Other chemicals of concern that were tested for were dioxins and PAHs, or polychlorinated aromatic hydrocarbons.

The transformers that the contained the PCBs were removed in the 1980s. In 2012 PacifiCorp used a specialized piece of heavy equipment in the Swan River to extract riverbed contamination, but it did not extract all of the contamination. 

Kevin Wilkinson, DEQ project manager for the Bigfork facility, said the contamination is centered in a couple of “hot spots” right around the powerhouse in downtown Bigfork.

He said the PCBs can attach to organic matter, making it difficult to extract them. “It’s very long lasting,” he said. In addition to PCB contamination, the report said there is also dioxin present in the sampled soils near the Bigfork powerhouse.

PCBs are a chemical that is prone to accumulation in wildlife, also. Wilkinson said testing of mackinaw from Flathead Lake revealed elevated levels of contamination. However, it’s unknown whether that contamination is from the Bigfork hydroelectric plant. “There’s no telling all the sources it could have come from,” Wilkinson said. “I can’t say this is the only place that created that.”

Removing the contaminated soil will require additional excavator work in the streambed, Wilkinson said.

PacifiCorp began the voluntary cleanup plan two years ago, and submitted its plan to the Montana DEQ in August. The company has five years to complete its plan.

PacifiCorp owns 166 acres on the south side of the Swan River in Bigfork, including the spillway upstream of the powerhouse, as well as the diversion channel that feeds water into the powerhouse. The facility was built in 1910, and expanded in 1924 and 1928.