BABBITT— The Minnesota Pollution Control Agency has added Birch Lake to its draft list of the state’s impaired wild rice waters due to sulfate contamination from nearby mining operations. That list, which is updated every two years, was released in draft form on Tuesday. Pending public comments and approval from the federal Environmental Protection Agency, the final list is expected to be approved next April.
This year marks the first time that the MPCA has proposed to list Birch Lake as impaired for its sulfate levels. The agency has resisted calls to do so in the past but was faced this year with an extraordinary amount of water quality testing data gathered over the past four years by Northeastern Minnesotans for Wilderness. The Ely-based organization undertook initial testing in 2019, which seemed to confirm the group’s suspicions that Birch Lake’s average sulfate levels were above the state’s 10 milligram-per-liter (mg/l) sulfate limit for wild rice waters and many times the background level found in northeastern Minnesota waters that are unimpacted by mining discharges.
The group sought advice and field training from experts from the University of Minnesota and developed and launched a comprehensive testing program in 2020. Actual testing of water samples gathered as part of the effort was done by RMB Laboratories, which maintains offices in Bloomington, Detroit Lakes, and Hibbing.
Lisa Pugh, who oversaw the testing program for NMW, holds a BS degree in Fisheries, Wildlife, and Conservation from the University of Minnesota and has four years of experience in water quality sampling. She was certified to conduct sampling through a training program held at the University of Minnesota’s Crookston campus in 2020. The results of NMW’s sampling is consistent with other testing efforts which have been undertaken by the 1854 Treaty Authority and WICOLA, which have consistently shown elevated sulfate levels in Birch Lake.
Since 2020, NMW staff have gathered over 330 samples from 28 distinct test locations and have shared that data in a 630-page report provided to both the MPCA and the Timberjay.
The group’s efforts impressed Dr. Patrick Brezonik, a recently retired University of Minnesota professor and former director of the university’s Water Resources Center. He also served as former chair of the MPCA’s scientific peer review panel on the wild rice sulfate standard. 
“NMW has built a professional water monitoring program that has produced extensive water quality data on the Birch Lake area of the Boundary Waters watershed,” said Brezonik. “Its trained monitoring staff followed appropriate sample collection methods, and a state-certified lab analyzed the water samples using accepted analytical methods. As a result, NMW has produced a large quantity of reliable water quality data in and around Birch Lake, which is essential to provide science-based answers to important water quality questions. Indeed, I am impressed with their operation.” 
The data, which have now been accepted by the MPCA, provide the clearest evidence to date of the impact of mining discharges, emanating from Dunka River and Unnamed Creek, and how it is affecting sulfate levels in the popular, 7,000-acre lake.
Potential impacts of the listing
The listing of Birch Lake as impaired for sulfate is likely to affect the existing mining operations at the Peter Mitchell mine, which discharges sulfates to the Dunka River, although to what extent the mine could be affected won’t be known for some time. The listing is also expected to pose a major regulatory challenge for any new mining operation that could be proposed in the Birch Lake watershed.
“The Clean Water Act says agencies are not allowed to issue a permit that would lead to a net increase of a pollutant into a water body already impaired for that pollutant,” said Matt Norton, Policy and Science Director with the Campaign to Save the Boundary Waters.
In that sense, NMW’s data and the MPCA’s listing decision is a potential shot across the bow to Twin Metals, which only recently began intensifying its exploratory drilling around Birch Lake’s Bob Bay. That’s where NMW found, by far, the highest concentrations of sulfate, reflecting the longstanding effects of discharges from the Dunka Pit, originally developed by LTV Mining back in the 1960s.
The Dunka Pit, which was the subject of the Timberjay’s 2015 investigative report, Mining vs. Water, continues to discharge high concentrations of sulfate into Birch Lake’s Bob Bay. Test data submitted to the MPCA by Cliffs Natural Resources, which owned the site at the time, showed sulfate discharges at the north end of the pit regularly averaging 1,800 mg/l. Those discharges enter Unnamed Creek just downstream from the pit and wind their way to Bob Bay. NMW’s test data found sulfate concentrations as high as 326 mg/l where the creek enters the bay and the effects of that discharge is clearly seen in water quality in the bay itself, where sulfate levels regularly test at several times the 10 mg/l limit for wild rice waters.
The Dunka River, which enters Birch Lake about three miles west of Bob Bay, receives discharges from the Peter Mitchell mine, which have pushed sulfate levels in the river well above background levels, as much as three times above the sulfate limit for wild rice waters.
Pinpointing the sources
The sulfate inflows from both the Dunka River and Unnamed Creek appear to be responsible for elevated sulfate levels on the west end of Birch Lake, where NMW’s testing shows that average sulfate levels are above the 10 mg/l threshold for impairment as a wild rice water. Their testing further confirms the highest levels of sulfate are found within Bob Bay and in the immediate vicinity of the outflow from Dunka River.
Birch Lake does receive inflow from other significant streams, including the Stony River, but NMW has undertaken testing upstream of Birch Lake on several of its tributaries that are unimpacted by mining discharges. Those test data show sulfate levels ranging from about 0.6-1.5 mg/l, which is typical of sulfate readings found in natural waters within the Rainy River watershed. Those data provide further evidence that the higher sulfate levels within Birch Lake are the result of discharges from mining locations. Outside of streams impacted by mining, the Rainy River watershed is known to contain some of the highest water quality of any watershed in the lower 48 states and much of it flows through the Boundary Waters Canoe Area Wilderness. The waters from Birch Lake feed into the BWCAW as they pass through the White Iron chain of lakes and enter the wilderness at the north end of Fall Lake.
The data suggests that water quality improves in Birch Lake near the mouths of streams entering the lake from areas unaffected by mining discharges. A lake sampling site closest to the entrance of the Stony River, for example, consistently showed sulfate levels in the 1.5-3 mg/l range, which would be considered only marginally above background levels. The impact of dilution from the inflow of a major tributary, like the Stony River, is evident elsewhere on the lake, where testing data shows sulfate levels in Birch Lake waters averaging 5-8 mg/l at sampling sites located downstream from the entrance of the Stony River.
Norton notes that the mining industry is, in effect, benefitting from the pristine quality of so much of the water in the Rainy River watershed that is unaffected by mining discharges. “The mining companies are dumping all this sulfate and relying on the dilutionary effects of one of the cleanest watersheds in the state,” he said. “It is stunning the degree to which the state has been willing to look the other way.”
While sulfate levels slowly decline further downstream, recent testing by NMW has found sulfate readings as far downstream as the north end of Farm Lake above 4 mg/l, a level that’s at least three times the typical background level in the Rainy River watershed. That’s over 20 miles downstream from the sources of the sulfate pollution.
NMW plans to continue its existing testing and to expand it in the near future, to try to rule out other sources of elevated sulfate within the White Iron chain. For now, it’s keeping some of the locations of that testing to themselves.
EPA involvement
NMW’s testing program would have been for naught if not for the 2021 decision by the Environmental Protection Agency to overrule the MPCA’s decision not to list wild rice waters as impaired. Minnesota’s strict wild rice standard for sulfate was originally passed in 1973, but has not been enforced since its adoption until recently, due mostly to opposition from the state’s mining industry. Instead of limiting discharges of sulfate, the Legislature passed a series of laws beginning in 2015 that prohibited the MPCA from regulating sulfate pollution until it can create a new, looser standard.
In objecting to the MPCA’s failure to list impaired wild rice waters, the EPA contended that those laws enacted by the Legislature violate the Clean Water Act, which prohibits states from weakening or refusing to enforce water quality standards unless there’s a scientific basis. The Legislature, back in 2015, funded additional research on the subject in hopes of disproving the validity of the 10 mg/l standard, but the results mostly supported the limit. Without the means to weaken the standard, the Legislature passed a law prohibiting the MPCA from requiring compliance with the law. The MPCA, citing the Legislature’s action, had determined that it could not list wild rice waters as impaired even if sulfate levels required doing so. By overruling that decision, the EPA left the MPCA no choice but to add wild rice lakes with sulfate levels above 10 mg/l to the impaired waters list.
Sulfate, even at relatively low levels, has been shown to lead to the loss of wild rice in many cases. Minnesota is home to much of the wild rice found naturally in North America, which prompted state officials in the 1970s to adopt a strict wild rice standard for sulfate pollution in order to protect the unique resource.
Sulfate, at even lower levels, is known to facilitate the methylation of mercury, which can convert elemental mercury into far more toxic methyl mercury, which is known to bioaccumulate into fish tissues.

Editor's Note: An earlier version of this story had identified Franconia Minerals as the owner of the Dunka Pit. In fact, it is owned by Cliffs Erie.