Sulfate pollution: Focus shifts from the future to the present

Map of south shore of Birch Lake

December 1, 2023: For the past decade in Minnesota, media coverage and public debate on sulfate have often focused on the future, warning of potential sulfate pollution from copper-nickel mining, which might or might not get a green light on the Iron Range.

But sulfate pollution is already a problem in northern Minnesota’s waters. And the culprit is iron and taconite mining, both current and past. That’s a fact that many in northern Minnesota— especially tribal communities— have known for years. But it’s been lost on some of the players in the ongoing debate about protecting the environment, especially the Boundary Waters Canoe Area Wilderness.

That blind spot is now coming into view, especially with the MPCA’s recent listing of Birch Lake and the Dunka River as impaired for sulfate as well as mercury. The map above shows how the sulfate-laden Dunka River passes between two mine pits (one active, one inactive) before emptying into Birch Lake: now the first major lake on the Impaired Waters list whose waters flow into the BWCAW. That makes this a watershed moment— in more ways than one.  

Birch Lake near BWCAW polluted by sulfate, advocates blame taconite mines” is the headline in a Nov. 29 article by Greg Seitz in the Quetico-Superior Wilderness News.  The piece includes the map excerpted below, showing the extent of the sulfate and mercury impairment on the threshold of the BWCAW, the darker-green areas outlined at the top and top-right corner.

Look for these features on the map (many water bodies have several color notations on them): 

  • Sulfate is represented by red outlines along several rivers and lakes.
  • Mercury is shown by diagonal red lines: difficult to see on the map, but this applies to Birch Lake among many others.
  • Wild rice areas are shown by yellow-dotted infill on several lakes, including Birch Lake.
  • The watershed line is shown by the dotted-yellow “height of land” line.

The Minnesota Pollution Control Agency updates its list of impaired waters every two years. Lake Vermilion and several rivers were listed in 2022, as noted in parentheses on the map. Birch Lake and the Dunka River are noted “2023” because they are on the current draft list, set for official listing in 2024. The MPCA is now taking public comment on its draft list and will host several online meetings on the subject, open to the public. The December 8 and 12 meetings will focus on sulfates in wild-rice areas as well as PFOS in fish tissue. Details here

Map excerpt: sulfate-polluted waters on the Iron Range            

Detail of map: “Sulfate and Its Sources: Contamination in Canoe Country Threatens Wild Rice and Fish.
(c) 2023 Quetico Superior Wilderness News. Data: Bureau of Land Management, U.S. Forest Service, State of Minnesota, U.S. Geological Survey, Open Street Map.