Sulfate pollution poised to affect Minnesota’s Boundary Waters

Map showing Birch Lake's proximity to BWCA

Nov. 15, 2023:  It’s a grim landmark for a watershed. The Minnesota Pollution Control Agency has released its 2023 draft list of impaired waters in the state, and for the first time it includes Birch Lake, the 20-mile-long reservoir on the Iron Range. Birch Lake is part of the Rainy River watershed and drains into the protected Boundary Waters Canoe Area, as noted in the Star Tribune’s Nov. 14 article Lake that flows to Boundary Waters placed on state’s list of polluted waters. By doing so, “MPCA has indicated that enough sulfates have built up to harm the growth of wild rice,” says the article’s author, Chloe Johnson. Of all the water bodies that flow into and through the BWCA, Birch Lake is the first significant one to be named as impaired for sulfate, exceeding the 10 mg/L standard set for wild rice waters.

Our February 2023 post noted the two taconite mine pits that have for decades leached sulfate into the lake, two bays in particular. It’s worth noting that Clearwater BioLogic’s offices are housed on the shore of Birch Lake. The company has lab and field tested mining-impacted waters with high sulfate concentration and has successfully reduced sulfate to below the wild rice standard.

For details on other waters new to the list, read Dan Kraker’s MPR story State officials add dozens of lakes and streams to impaired waters list (Nov. 15). The MPCA is now accepting public comments on its draft list of impaired waters.

Map credit: C.J. Sinner, Star Tribune