Montana DEQ Denies Petition to Modify the Selenium Standard for Lake Koocanusa

The Montana Department of Environmental Quality (DEQ) has denied the petition for rulemaking to modify the selenium water column standard for Lake Koocanusa and the definition of steady state.

 

On Sept. 2, 2025, DEQ provided a response to the Petitioner, the Board of County Commissioners of Lincoln County. The response includes a copy of the public comments DEQ received regarding the petition. Those who wish to view public comments, the petition and DEQ’s response can do so on the agency’s website.

 

DEQ accepted public comment regarding the petition for 30 days and held a public hearing in Helena on Aug. 13, 2025. The agency received and reviewed 305 comments including input from tribal representatives, local area businesses, the Environmental Protection Agency (EPA), state agencies, and the Petitioner.

 

In 2020, a site-specific water quality standard for selenium of .8 µg/L was adopted for the Montana portion of Lake Koocanusa. The standard was adopted after a process that lasted over six years, involving partners from the United States and Canada. EPA approved the site-specific water quality standard in 2021. The petition for rulemaking requested modification of the Lake Koocanusa standard to increase the water column criterion from 0.8 µg/L to 1.5 µg/L and to modify the definition of steady state. Steady state is defined in Montana Administrative Rule 17.30.632 as, “Conditions whereby there are no activities resulting in new, increasing, or changing selenium loads to the lake or river aquatic ecosystem, and selenium concentrations in fish living in the aquatic ecosystem have stabilized.”

 

Concerning selenium levels in Lake Koocanusa, DEQ continues to coordinate with British Columbia and other represented governments through participation in the International Joint Commission (IJC) Governance Body and Study Board, with the goal of reducing and mitigating the impacts of water pollution to protect the people and species in the Kootenai/y watershed.

 

DEQ staff would like to thank everyone who participated in the process by providing data, views, or position statements concerning the petition. For future public participation, every three years DEQ opens all water quality standards for public comment and hosts a hearing in a process called triennial review. The next triennial review will take place in 2026.