The Minnesota Court of Appeals on Tuesday said an additional environmental review of the contentious PolyMet copper-nickel mine near Hoyt Lakes is not needed.

Opponents of the recently approved mine, set to be the first of its kind in Minnesota, argued the Department of Natural Resources erred when denying requests for a supplemental environmental impact statement after PolyMet indicated in a March 2018 technical report that its site had enough ore for a substantially larger mine in the future.

But in an opinion released Tuesday, Judge Renee Worke wrote that the DNR’s decision to deny requests for the additional review was legally sound.

“The DNR properly considered the facts that (1) the technical report itself characterizes the discussion as preliminary; and (2) no permits have been sought for expansion to the project,” Worke wrote.

While the DNR granted PolyMet its permit to mine and 10 other approvals last year, it was based on the company recovering about 32,000 tons of ore every day. Environmental groups argue the technical report released by PolyMet outlines the company's ambitions to triple that to 118,000 tons per day and that the impacts of that larger project must be factored into the environmental review.

Opponents have called that disclosure a last-minute “bait and switch.” Now that PolyMet is fully permitted for one mine plan, they argue, it will be easier for the state to approve an expansion. Therefore, opponents of the project maintain the environmental impacts of that larger project must be studied.

In a statement Tuesday, Chris Knopf, executive director of Friends of the Boundary Waters Wilderness, which filed the appeal with Minnesota Center for Environmental Advocacy and WaterLegacy, stood by that assertion.

“We respect the court, but profoundly disagree with its opinion. What PolyMet pulled was a classic bait-and-switch move, and we called them out on it,” Knopf said. “All evidence points to the fact that they fully intend to expand the mine after they begin operations. When they do, the political pressure to approve the expansion will be so great that it will be impossible to do any meaningful environmental study on its impact.”

Elise Larson, an attorney for the Minnesota Center for Environmental Advocacy, said the group is considering its next steps. That could include appealing Tuesday's decision to the Minnesota Supreme Court.

During oral arguments in March, PolyMet attorney Jay Johnson echoed points made previously both by PolyMet and the DNR: If PolyMet plans to expand its mine, the environmental impacts of that expansion would be studied at that time.

“So all the concerns about potential future environmental risks from a larger or a different mine will all be studied if and when any such thing is ever proposed,” Johnson said. “Right now, what’s proposed and permitted is a 32,000-tons-per-day mine, and that's the only thing that PolyMet is authorized to do.”

PolyMet celebrated the decision Tuesday.

“We are pleased that the Court of Appeals agrees with us and the DNR,” Jon Cherry, president and CEO of PolyMet, said in the release. “The court’s decision reaffirms the environmental review for NorthMet, which was the most comprehensive and lengthiest in the state’s history, appropriately addresses the scope of our plan to responsibly mine copper, nickel and precious metals from the world-class Duluth Complex in Northeastern Minnesota.”

The PolyMet environmental review was released in November 2015 and the DNR determined it was "adequate" in March 2016. In July and August 2018, the DNR rejected petitions by several environmental groups calling for additional environmental impact statements to consider the March report's potential project expansion.