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Water quality data raises doubts about DNR legal claims

Extensive testing shows path of pollution reaches Boundary Waters

Marshall Helmberger
Posted 1/23/25

REGIONAL—A legal proceeding now in its fifth year has the potential to reshape state rules surrounding the permitting of non-ferrous mining operations. The case, filed by Northeastern …

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Water quality data raises doubts about DNR legal claims

Extensive testing shows path of pollution reaches Boundary Waters

Posted

REGIONAL—A legal proceeding now in its fifth year has the potential to reshape state rules surrounding the permitting of non-ferrous mining operations. The case, filed by Northeastern Minnesotans for Wilderness, or NMW, back in 2020, seeks to require the Department of Natural Resources to revise it mining regulations to provide greater protection to the Boundary Waters Canoe Area Wilderness.
NMW alleges that the current rule, established decades ago by the DNR, is inadequate to protect ground and surface water because it fails to prohibit mining of nonferrous metals, like copper and nickel, within those portions of the Rainy River watershed located upstream of the BWCAW.
The DNR, for its part, argues that the Boundary Waters is adequately protected under the Clean Water Act, which designates the waters within the 1.1-million-acre wilderness as “prohibited outstanding resource value waters.” The federal law prohibits any degradation whatsoever of waters with this pristine designation. In other words, there’s no possibility an upstream copper-nickel mine could pollute the Boundary Waters, according to the DNR, because federal law prohibits it.
Yet lawyers for NMW argued in a contested case hearing in November that laws, by themselves, don’t protect resources like the Boundary Waters from pollution— only enforcement of those laws can do that. And based on the intensive water testing program undertaken by NMW in recent years, they argued the DNR appears to already be failing to meet the requirements of the Clean Water Act.
Indeed, the Minnesota Pollution Control Agency, citing NMW’s water testing data, added Birch Lake to the state’s list of impaired waters for wild rice last year due to sulfate pollution from the Peter Mitchell pit, located east of Babbitt, as well as the sulfide-bearing waste rock piles at the nearby Dunka pit. NMW’s rigorous testing program, which included more than 330 samples from 28 distinct locations, has documented a path of sulfate pollution extending downstream more than 20 miles from the two taconite pits, extending into the BWCAW through the White Iron chain of lakes. NMW has documented that its sampling meets all appropriate collection standards and all testing is done by independent labs.
While the Peter Mitchell pit remains active, the Dunka pit was closed more than 40 years ago yet has continued to discharge pollutants ever since. NMW’s testing data shows the highest levels of sulfate just downstream from the Dunka pit, where levels in Unnamed Creek routinely register over 300 milligrams per liter. The state’s wild rice standard limits sulfate levels to 10 mg/l in wild rice lakes.
The sulfate levels in Birch Lake decline as water flows to the northeast and as other streams and rivers, unimpacted by mining, enter the lake and dilute the sulfate levels. Even so, NMW’s testing has found sulfate levels remain 50 percent higher than normal background (0.5 - 1.5 mg/l in the region) as far north as Newton Lake, located in the Boundary Waters, more than 20 miles downstream of the sources of the pollution.
The copper-nickel deposits that Twin Metals hopes to mine are located several miles closer to the Boundary Waters than either the Peter Mitchell or Dunka pits and would be mining ore high in sulfur, which converts to sulfate when exposed to oxygen.
According to Becky Rom, who has opposed the Twin Metals proposal as head of the national Campaign to Save the Boundary Waters, the DNR has claimed that the pollution from the mining operations only extends downstream about two miles, but she says that NMW’s test data proves that claim is false.
Predicting pollution
For years, mining supporters have argued that the Twin Metals project should have the chance to prove it can operate safely by going through the environmental review process. NMW, in its case, has argued that such reviews are rarely accurate and routinely underestimate the amount of pollution that is eventually seen from mining operations. They pointed to a 2005 peer-reviewed study, Predicting Water Quality at Hardrock Mines by James Kuipers and Ann Maest, that highlighted the complexities of modeling impacts that may play out over centuries, long after mines have ceased operation. “The degree of confidence in the models is severely limited in part because the models are so complex that they cannot be easily reviewed by regulatory staff and the public,” noted the study’s authors. “Considering the difficulty in representing physical and chemical properties of mined materials, the meaning of “accuracy” in water-quality modeling must be reconsidered in the regulatory process,” the authors concluded. In the end, said Rom, the study found that modeling of mines near ground or surface typically underestimated the water quality impacts nine out of ten times.
The DNR challenged that study during the November contested case hearing, arguing that it was nearly 20 years old and that its review did not include any mines in Minnesota.
Yet, NMW countered that the DNR has much more recent evidence of the failure of modeling from right on the Iron Range.
They point to the results of a stockpile of sulfide-bearing rock exposed in 2019 as part of expansion of the Peter Mitchell pit. Both the DNR and Northshore modeled the impact of the new stockpile with the implementation of the planned mitigation, including a cover to eliminate water infiltration that would release sulfate and other pollutants. That study concluded the average increase in sulfate discharge from the stockpile of between two and five percent, but subsequent monitoring showed a much higher rate of discharge—approximately 43 percent higher.
“Actual pollution was significantly greater than predicted pollution based on modeling, and this is a modern mine in Minnesota,” said Rom.
Such conclusions raise questions about the validity of environmental review of mining operations, particularly those in water-rich environments, where the pathways of pollution may be varied and highly complex.
The Timberjay sought comment from the DNR for this story, but officials declined given the ongoing nature of the litigation.
Findings expected
in April
During the hearing in November, the DNR offered up its own evidence and expert testimony to argue that the rules as written are adequate to protect water quality. Post-trial briefs in the case are due Feb. 12 and findings and recommendations from the administrative law judge are expected sometime in April.
The DNR won’t need to abide by the recommendations, but the overall case is being overseen by a Ramsey County judge who could overrule the DNR if its ultimate decision in the matter isn’t consistent with the administrative law judge’s findings.