Avista concludes mineral oil cleanup

NOXON, Mont. — Avista is wrapping up cleanup efforts on the Clark Fork River after a mineral oil spill earlier this year.

“There’s no indication that the incident caused any harm to fish, wildlife or water supplies,” said Bruce Howard, director of environmental affairs for Avista. “However, we made a commitment to take extra precautions and keep absorbent booms on the water as long as necessary to ensure we cleaned up as much mineral oil as possible.”

The spill was discovered at Avista’s Noxon Rapids hydroelectric project on Feb. 26. A buildup of ice on the face of the dam gave way and broke a pressure gauge on the valve of a pipe carrying transformer oil, causing oil to spill on the transformer deck.

Final calculations indicate that just over 1,000 gallons of the lightweight mineral oil entered the river between the Noxon and Cabinet Gorge dams.

Material collected from the river over the six-week period was routinely tested and showed little or no presence of mineral oil and no presence of polychlorinated biphenyls, also known as PCBs.

“What we’ve collected from the river in recent weeks appears to come from other sources, including biological materials typical of vegetation and other natural substances that accumulate on the water during spring runoff,” said Howard.

“We’re at the bottom end of a very substantial river drainage system, so we see everything that enters the river upstream.”

The U.S. Environmental Protection Agency applauded Avista’s response to the incident.

“The cleanup of the mineral oil release in Noxon posed many unique challenges and the Avista team worked very long hours under difficult circumstances to complete the removal,” said Duc Nguyen of EPA.