A large lake has varying sulfate levels: Is it “impaired”?

Map of south shore of Birch Lake

February 2023: On Minnesota’s Iron Range, the 20-mile-long reservoir known as Birch Lake snakes through the forest northeast of Babbitt. With shorelines rich in wild rice, these waters ultimately flow north into the Rainy Lake watershed and the Boundary Waters. But on Birch Lake’s south shore, sulfate pollution levels have been found to exceed the state standard set to protect wild rice: 10 milligrams per liter. Those levels are markedly higher in the two bays where water from two nearby mine pits— one active, one inactive— drain into the lake. Should the Minnesota Pollution Control Agency include Birch Lake on the state’s Impaired Waters list, which is now being updated? Marshall Helmberger outlines the issue in the Timberjay (Northern St. Louis County, MN), Feb. 1, 2023. Read it online or as a PDF. For more details, read the MPCA’s Public Notice Comments document: see Comment 11, pages 10–13.  

Map: Southwest end of Birch Lake and environs. Note that the inactive Dunka Pit (now a lake) drains into Bob Bay while the active Northshore Mining pit drains into Dunka Bay.