Idaho Power plans dropped its lawsuit against the Environmental Protection Agency after the federal agency approved the State of Idaho's 2012 request to increase maximum water temperature criteria in a stretch of the Snake River below Hells Canyon Dam for two weeks each fall.

EPA's approval, however, will not result in a new water temperature standard unless Oregon also approves it. EPA's and Idaho's site-specific criteria change would only affect the stretch of the Snake River from just below Hells Canyon Dam to the Snake's confluence with the Salmon River.

Idaho Power spokesman Brad Bowlin told NW Fishletter in an email the company plans to petition Oregon for the criteria change, which the Idaho Legislature finalized and adopted in 2012.

The utility filed the lawsuit—Idaho Power Company v. United States Environmental Protection Agency, et al.—in June 2018, after EPA failed for six years to act on Idaho's request for the site-specific criteria change. U.S. District Judge B. Lynn Winmill dismissed the case on Dec. 11, two days after Idaho Power filed a notice of voluntary dismissal.

According to a Nov. 21 letter from EPA to the Idaho Department of Environmental Quality, the agency's approval is based on a recent biological opinion by the National Marine Fisheries Service concluding that the change, "although likely to adversely affect Snake River Fall Chinook spawning, would not jeopardize the Snake River Fall Chinook [evolutionarily significant unit]."

Snake River fall Chinook were listed as threatened in 1992.

Under current standards in Idaho and Oregon, maximum water temperatures in all rivers must reduce from 66.2 degrees to 55.4 degrees on Oct. 23, and remain at or below 55.4 degrees through April 15.

The new site-specific standard—if Oregon agrees—would step down the maximum temperature to 58.1 degrees for two weeks beginning Oct. 23, and then drop again to 55.4 degrees from Nov. 7 through April 15.

Idaho Power says the higher water temperature standard could save its customers between $50 million and $100 million in fees over 50 years, instead of being paid as mitigation to a stewardship program when temperatures exceed the current standards.

Bowlin said EPA's approval does not directly impact Idaho's efforts to relicense the Hells Canyon complex. "We are pleased with the EPA's decision to approve; it's an important step but it does not immediately change anything related to relicensing," he wrote.

K.C. Mehaffey covers fish issues for Clearing Up, and is editor of the NW Fishletter. She joined the NewsData writing team in February 2018. From lawsuits to scientific studies, she is enjoying the deep dive into the Columbia Basin's many fish topics.