A federal regulator has suspended the permit it issued to PolyMet Mining Corp. to fill or dredge more than 900 acres of wetland for Minnesota's first copper mine, handing a victory to the Fond du Lac Band of Lake Superior Chippewa.

The move spotlights the band's groundbreaking effort to assert Indigenous water quality standards as a "downstream state" under the Clean Water Act.

It also means that five major permits for the $1 billion PolyMet project are now stayed or under review.

The U.S. Army Corps of Engineers stayed the "404" wetlands permit it issued to PolyMet in order for the U.S. Environmental Protection Agency (EPA) to review whether the copper mine project will negatively affect the reservation waters of the Fond du Lac Band.

The affected wetlands surround the Partridge and Embarrass Rivers, which lead to the St. Louis River that runs through the reservation of the Fond du Lac Band. The reservation, northwest of Cloquet, is about 70 miles downstream from the proposed copper mine. The tribe uses the St. Louis River for fishing, hunting and other purposes.

The outcome of the EPA's review "may require the Corps to reconsider the 404 permit," the Corps of Engineers said in a March 17 letter to PolyMet, a copy of which was given to the Star Tribune by Friends of the Boundary Waters Wilderness.

"Depending on the outcome of the EPA's review, the Corps will make a decision to either reinstate, modify, or revoke the permit," Corps of Engineers Col. Karl D. Jansen wrote.

PolyMet spokesman Bruce Richardson said the company remains committed to the proposed copper mine.

"We plan to participate fully in the review, as appropriate, and believe the science will once again prevail," he said. "This temporary hold has no immediate bearing on the project as there is other litigation that is being resolved."

PolyMet, based in Toronto, is majority owned by Glencore in Switzerland.

In a statement released March 22, the Fond du Lac Band said it is pleased with the suspension. The previous Trump Administration "wholly failed to consult with the Band or listen to science," it said. The project doesn't comply with the Band's federally approved water quality standards, it said, and certain discharges are completely unregulated.

"This is a serious concern for the Band because PolyMet proposes to dump polluted wastewater and other contaminants into waterways that flow through the Band's Treaty territory and ultimately down to the Band's Reservation," the statement said. "As found by the Federal District Court in the Band's litigation, EPA had legal duty to make a determination on those downstream effects and observed that the Band had a 'slam dunk' claim that EPA did not comply with the law."

Chris Knopf, executive director of Friends of the Boundary Waters Wilderness, which has fought the mine for years, called the suspension "fantastic news." The Fond du Lac Band previously has been thwarted in its efforts to assert its regulatory authority over those waters, he said.

"They've just been dismissed in this process," he said.

Paula Maccabee, advocacy director and counsel of the environmental nonprofit WaterLegacy, said the Fond du Lac Band has its own EPA-approved water quality standards and they need to be recognized.

"The Fond du Lac Band is breaking new ground," Maccabee said.

"This is the first time that any downstream tribe has attempted to exercise their rights under the Clean Water Act to object to a federal permit," she said. "Tribal science and additional scientists all believe that there is a strong likelihood that the PolyMet project will increase mercury in the St. Louis River fish on the reservation."

The EPA and Army Corps of Engineers were pushed to the decision after the Fond du Lac Band sued both agencies in U.S. District Court in Minnesota and prevailed on several points.

Last month, the federal judge ruled that the EPA failed its duty to consider whether the discharge allowed under the wetlands permit could affect the band's waters and also failed to notify the band.

Judge Patrick Schiltz wrote: "The Band would seem to have a plausible (perhaps even a slam-dunk) claim that EPA did not act 'in accordance with the law.' "

Jennifer Bjorhus • 612-673-4683