After legislators from northwest Montana first opposed and then required that several months be spent studying Lake Koocanusa’s new selenium limits, the state has decided the standards are valid and will remain.

The Montana Department of Environmental Quality this week released final written findings that justify selenium standards specific to Lake Koocanusa that were initially accepted in late 2020 to protect aquatic life in the reservoir and the Kootenai River below the reservoir.

Selenium is an essential nutrient but it can be toxic to fish above certain concentrations, primarily affecting the reproductive system. Through a process called bioaccumulation, selenium amounts increase as little fish eat plants or bugs and big fish eat little fish. So large fish can suffer more contamination and selenium limits  are needed to protect them.

But often, fish die from deformities while they’re still embryos or fry since selenium affects development. The percentage of deformed adults caught by biologists or anglers probably under-represents all the fish that are affected, officials have said.

In October 2020, Idaho’s Clean Water Act report listed the Kootenai River as impaired for selenium. Idaho’s sampling in 2019 found mountain whitefish with selenium levels in their reproductive organs that exceeded EPA limits.

The standards DEQ adopted in 2020 to protect fish include a concentration limit of 0.8 micrograms per liter in the lake water and 3.1 micrograms per liter in the Kootenai River. Streams can have higher limits because the water is moving, constantly flushing out. There are also limits for various fish tissues, especially eggs and ovaries.

However, the water column concentration in Lake Koocanusa already exceeds the DEQ standard, coming in at more than 1 microgram per liter due to pollution from coal mining in British Columbia’s Elk River Valley just north of Lake Koocanusa.

Coal mines owned by Teck Resources sit along the Elk River and have been leaching selenium and nitrogen into the river for decades. The concentration of selenium at the mouth of the Elk River started exceeding the British Columbia guidelines in the early 1990s. It’s now four times the B.C. guidelines. Studies show about 95% of the selenium in Lake Koocanusa comes from the Elk River.

In November 2021, the Province of British Columbia finally proposed a selenium standard of 0.85 micrograms per liter for Canada’s half of Lake Koocanusa.

After the U.S. Environmental Protection Agency approved Montana’s standards in February 2021, Teck Coal Limited and Lincoln County challenged the standards, petitioning the Board of Environmental Review – which oversees DEQ - to declare Montana’s standards to be more stringent than federal standards. The EPA standard for water-column selenium is 1.5 micrograms per liter, however the EPA says selenium limits can be situation-dependent.

After the election of Gov. Greg Gianforte in November 2020, new people were appointed to the Board of Environmental Review that didn’t know the seven-year history of the development of the selenium standards, and the petitioners hoped the board would give them relief. Legislators from Lincoln County have repeatedly said they heard nothing about the standards until they were approved. Claiming the process was “rushed,” they’ve demanded DEQ conduct a new analysis.

The board did determine in February that the DEQ’s standard was more stringent than that of the EPA, but that’s where the Board’s authority stops. The board could only require the DEQ to publish written findings.

DEQ issued its initial draft in April and then accepted close to 150 public comments. Opponents worried the standard could affect future development in Montana, but the DEQ found little selenium in Montana’s soils and concluded that simple best practices could control any locally produced selenium. The vast majority of selenium in the lake comes from Canada. So the final ruling went unchanged.

Meanwhile, the 2021 Legislature passed House Joint Resolution 37 directing a committee to study the Koocanusa selenium standards. In early May, the committee published a draft paper finding that a significant amount of science and public participation went into the development of the 2020 standards. The committee’s only question related to the calibration of the models. The special committee’s next meeting is July 5.

If the selenium standards are now truly final, DEQ can do little to reduce selenium concentrations in the reservoir until Teck Resources reduces its selenium pollution. To that end, last week, the U.S. State Department said President Joe Biden supports a bi-national investigation into the selenium pollution coming from Teck Resources’ mines.

"The (State) Department reaffirmed the administration's support for a joint reference to the International Joint Commission under the Boundary Waters Treaty of 1909 for the Kootenai Basin regarding the transboundary impacts of mining," said a State Department statement issued June 8.

The U.S. embassy in Ottawa said the State Department has been "in discussions" with Canada over the issue since September, according to the Canadian Broadcasting Corporation.

Contact reporter Laura Lundquist at