The U.S. Army Corps of Engineers suspended a wetlands permit for PolyMet, the company trying to open Minnesota's first copper-nickel mine, as the Environmental Protection Agency reviews whether the proposed project "may affect" the downstream Fond du Lac Band of Lake Superior Chippewa.

The Army Corps told PolyMet in a letter Wednesday that it was suspending its Section 404 permit, which allows PolyMet to discharge dredged and fill material into over 900 acres of wetlands, during the EPA's 90-day review.

A suspension was in the public interest, Col. Karl D. Jansen, district engineer for the Army Corps, wrote in the letter.

"The outcome of EPA’s 'may affect' determination may require the Corps to reconsider the 404 permit ... Depending on the outcome of the EPA’s review, the Corps will make a decision to either reinstate, modify or revoke the permit," Jansen said.

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The "may affect" review stems from a federal judge's decision last month that said the "EPA had a legal duty to make a 'may affect' decision." As a result, the EPA voluntarily filed a motion, later granted by the court, to allow it 90 days to determine any potential effects.

If during its review the EPA finds discharges from PolyMet "may affect" the Fond du Lac Band's waters, it would be required to notify the band. That would then allow the band to object to the permit and require the Army Corps to hold a hearing on the band's objection.

In a news release announcing 2020 financial results Thursday, PolyMet reiterated it would take part in the review: "The company is participating fully in this review, as appropriate."

The company did not oppose EPA's earlier motion to conduct the review.

PolyMet is proposed near Babbitt and Hoyt Lakes, 70 miles upstream from the Fond du Lac Reservation, and in the St. Louis River Watershed.

The Fond du Lac Reservation and treaty land sits on the St. Louis River. The band fears potential pollution from PolyMet, namely sulfides, would damage its wild rice and other resources.

Groups opposed to PolyMet welcomed news of the permit suspension.

“Public officials who issued the permit in the first place, who were in charge of safeguarding our environment and human health, did not do their job and failed to consider the impact the mine would have on the Fond du Lac Band," Chris Knopf, executive director at Friends of the Boundary Waters Wilderness, said in a statement.

A number of other PolyMet permits remain on hold amid numerous legal challenges to the project.