Ahead of President Joe Biden’s visit to Canada, U.S Sen. Jon Tester raised concerns pertaining to Northwest Montana in a letter sent to the White House, including ongoing selenium pollution in the region’s waterways.

Two of Tester’s top concerns involved water management along the border. Tester asked Biden to work with Canada on the selenium pollution in the Kootenai River and Lake Koocanusa. He also asked the president to aid in the renegotiation of the 1964 Columbia River Treaty.

“I also strongly encourage the administration to work with the Canadian Government to resolve the ongoing selenium contamination issue in the Kootenai watershed in Montana,” wrote Tester.

For years, the contamination from upstream metallurgical coal mining along the Elk River has seeped across the border, according to Tester. Selenium in small amounts is necessary for life, but in high concentrations it can cause environmental issues especially for fish reproduction.

Tester said levels of selenium coming from the Elk River have been increasing and that selenium concentrations have led to the degradation of water quality and aquatic life in Lake Koocanusa.

“Selenium contamination stands to cause significant harm to fish populations in Lake Koocanusa and the Kootenai River, threatening both Montana’s outdoor recreation economy and the Confederated Salish and Kootenai Tribes’ treaty-guaranteed water and fishing rights,” wrote Tester.

Tester urged the president to request a referral to the International Joint Commission in order to resolve the transboundary water issue.

According to State Sen. Mike Cuffe R-Libby, one way selenium concentrations could become problematic would be if the Canadian government exercised its treaty rights to pull water from the Kootenai River. Canada has the right to divert up to 1.85 million acre feet from the Kootenai river to the Columbia, Cuffe said.

Cuffe said he has encouraged Tester to work to prevent this from happening.

“Should they ever exercise that right, No. 1 it's going to decrease production at Libby Dam,” Cuffe said. “No. 2, it's going to increase the percentage of selenium in Lake Koocanusa. No. 3, it's going to be detrimental to the aquatic health of the Kootenai and the Columbia and Lake Koocanusa.”

Tester’s letter touched upon the modernization of the 1964 Columbia River Treaty, but did not draw the same connection to selenium pollution. The treaty appeared as a standalone issue in the senator's letter.

“The Columbia River Treaty has direct impacts on the economy, environment and flood control of Montana communities, any changes could have major impacts far into the future,” Tester wrote. “The United States now has less than one year to finalize negotiations with Canada before reaching a point at which either party can initiate significant changes to the treaty including termination, with 10 years notice to the other country.”

The treaty was originally brokered between the U.S and Canada to increase flood control on the Columbia River, but now Sen. Steve Daines, Montana Gov. Greg Gianforte and Tester have indicated that they are ready to negotiate the treaty differently, according to Cuffe. Tester is calling on Biden to negotiate an agreement that “will serve all the communities that rely on the Columbia River.”

“They have never made an attempt to divert that water, however it remains a threat to Montana as long as it's in the treaty,” Cuffe said.

Among Tester's other listed concerns is a vaccine requirement for truck drivers crossing the U.S-Canada border. The mandate is affecting supply chains and trade, according to the senator.

Tester also asked Biden to negotiate a new softwood lumber agreement with Canada to spur job growth in the American timber industry.