The Minnesota Court of Appeals on Monday, Aug. 5, ruled against environmental groups seeking to hold up a mining project in northeast Minnesota that the environmentalists say could pollute Lake Superior.

The ruling upheld the state’s non-ferrous mining rules, which were challenged after the Minnesota Department of Natural Resources granted PolyMet a permit to mine for the company's proposed copper-nickel mine near Hoyt Lakes — the first mine of its kind to be permitted in Minnesota.

The groups, led by the Minnesota Center for Environmental Advocacy, had argued the DNR’s non-ferrous mining rules — rules that regulate the mining of metals that do not contain iron such as copper, nickel and other precious metals — were too vague and, therefore, unenforceable.

But on Monday, three appellate judges unanimously upheld the rules and determined the DNR’s non-ferrous mining rules to be “valid.”

Opponents of the project argued the DNR’s rules did not have strict, specific reclamation standards while the DNR maintains the rules were strong yet flexible.

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In a statement Monday, DNR Deputy Commissioner Barb Naramore said the agency was “pleased” with the court ruling in their favor.

“The decision affirms that, in seeking to promulgate rules that are both rigorous and appropriately flexible, the DNR did not exceed its statutory authority or violate constitutional provisions,” Naramore said.

Opponents of the project, who have long argued the project could send tainted runoff into the St. Louis River watershed and Lake Superior, disagreed.

Kevin Reuther, legal director for the Minnesota Center for Environmental Advocacy, signaled the group was looking to appeal the Court of Appeals decision to the Minnesota Supreme Court.

PolyMet opponents argue “Non-ferrous mining presents new and unknown dangers, and DNR's rules are not sufficient to protect Minnesota’s resources,” Reuther said in a statement. “The state's highest court should review these rules given what's at stake.”

PolyMet, which still needs to raise almost $1 billion to build its mine, considers Monday’s ruling a win.

“We are pleased that the Court of Appeals ruled in our favor,” said Jon Cherry, president and CEO of PolyMet. “Minnesota’s standards for non-ferrous mining are among the strictest anywhere in the world, and we demonstrated through the extensive environmental review and permitting process that we can meet or exceed these standards.”

Duluth for Clean Water, Friends of the Boundary Waters Wilderness, Center for Biological Diversity, Save Lake Superior Association, Friends of the Cloquet Valley State Forest and Save Our Sky Blue Waters had also joined MCEA on the petition.