DEQ Press Releases

Davin, Moira

Board of Environmental Review Initiates Rulemaking for Selenium Water Quality Standards in Lake Koocanusa and the Kootenai River

HELENA—Today, the Board of Environmental Review initiated rulemaking to establish site-specific water quality standards for selenium in Lake Koocanusa and the Kootenai River in Lincoln County, Mont. The rule initiation follows a request made by the Montana Department of Environmental Quality (DEQ). 

Selenium is a micronutrient essential to biological functions in animals and certain plants at minute quantities. However, at elevated levels, selenium can adversely impact a broad range of aquatic life including fish, and birds that eat aquatic life. High selenium levels can cause reproductive effects, reduced growth and mortality in fish populations.  

Rising levels of selenium entering Lake Koocanusa have been identified as a result of historic and current ​coal mining in the Elk Valley in British Columbia, Canada. There are currently no entities with a permit to discharge in Montana that contribute selenium to Lake Koocanusa or the Kootenai River. DEQ listed Lake Koocanusa as threatened for selenium in 2012.

Lake Koocanusa is an international water body formed by the Libby Dam. The lake is fed by rivers near Canadian mining operations. The Kootenai River is also an international water body, originating in British Columbia. DEQ has worked closely with the British Columbia Ministry of the Environment & Climate Change Strategy, local tribes, industry, federal representatives and state representatives to develop a site-specific selenium standard for Lake Koocanusa. The goal for both Montana and British Columbia is to adopt aligned standards that protect aquatic life. 

The current selenium standard for the water bodies was established in 1987 at 5 µg/L. In 2016, the EPA developed updated recommended national criteria at a value of 1.5 µg/L for lakes and reservoirs and 3.1 µg/L for rivers—while also suggesting to use site-specific standards, whenever possible.  

The Board of Environmental Review is proposing water column and fish tissue selenium standards for both Lake Koocanusa and the Kootenai River. The proposed water column standard for Lake Koocanusa is 0.8 µg/L. This standard was developed based on the unique, site-specific aquatic ecosystem of the water body. The proposed standard for the Kootenai River is 3.1 µg/L and based on EPA's recommended national criteria

The proposed water column value for Lake Koocanusa is lower than the EPA’s national recommended criteria of 1.5 µg/L for lakes and reservoirs, but in alignment with the recommendation that, where possible, selenium standards should be established based on site-specific conditions. This is because selenium accumulates as it moves through the food chain in bugs, fish and other aquatic life. The accumulation differs from site-to-site depending on factors such as species and general water chemistry.  

The proposed fish tissue standards are broken down into egg-ovary (15.1 mg/kg), muscle (11.3 mg/kg) and whole-body (8.5 mg/kg) selenium values for both water bodies. 

The proposed standards are a culmination of more than six years of collaboration with leading selenium scientific experts and the Lake Koocanusa Monitoring and Research Working Group that included years of public meetings, data collection and a peer-reviewed modeling report. 

The Board of Environmental Review’s proposed selenium standards for Lake Koocanusa and the Kootenai River are designed to protect water quality and the health of aquatic life.  

The Board of Environmental Review has initiated the rulemaking process. The next step in the process is to file a notice of proposed rulemaking in the Montana Administrative Register, after which there will be a 45-day public comment period and a public hearing to be held in early November. 

For more information, visit DEQ’s website at:

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