On the eve of his 85th birthday, former Minnesota Gov. Arne Carlson stood on the steps outside Duluth City Hall Monday to share his concerns over PolyMet, which is vying to be the state's first copper-nickel mine but faces numerous legal and permitting challenges.

"The biggest concern that I have is the appalling lack of transparency," Carlson said in front of a crowd of PolyMet opponents and news media.

The flawed process and potential for pollution, Carlson told the News Tribune, is what made him such a passionate opponent of the mine.

Carlson, who served as governor from 1991 to 1999, was first a Republican but didn't earn his party's nomination in the 1994 election. During his two terms, he was fiercely pro-business.

On Monday, he cited his efforts in the 1990s to ensure Northwest Airlines opened facilities throughout the Northland and noted that Delta Air Lines still employs people at the former Northwest call center in Chisholm after the two airlines merged.

So it might strike some as odd that Carlson has become such a staunch opponent of PolyMet, which could support 300 jobs at its open-pit copper-nickel mine and processing facility near Hoyt Lakes and Babbitt.

But Carlson doesn't see it that way. Instead, he summarized a point made by Elizabeth Warren, a U.S. senator from Massachusetts and presidential candidate, during her campaign.

"If you are for capitalism, you are also for good behavior," Carlson said.

In the decades since serving as governor, Carlson has endorsed multiple Democrats running for office. Today, he considers himself an independent.

From first writing about PolyMet on his blog in 2015 to penning a letter earlier this summer with other former politicians and government officials, Carlson has highlighted the potential for environmental damage if the mine is operational.

"We ought not to see any segment of our economy as anti-environment," Carlson said. "All segments must be part of the environment."

Speaking at Monday's event, Chris Knopf, executive director of Friends of the Boundary Waters Wilderness, said he appreciated having Carlson advocate for communities downstream of PolyMet, which is planned for the St. Louis River watershed.

"I want to say how inspiring it is to have Gov. Carlson here on the eve of celebrating his 85th birthday to be passing the baton on and still fighting for all of us," Knopf said. "We need that kind of spirit."

As the News Tribune has reported, the Environmental Protection Agency was concerned a draft of the water permit would not meet the Clean Water Act standards unless the Minnesota Pollution Control Agency made substantial changes, and a leaked email showed an MPCA official requested the EPA not comment on the draft permit until public comment ended.

The revelations spurred three separate inquiries — by the EPA's Office of Inspector General, Minnesota's Office of Legislative Auditor, and Minnesota Court of Appeals, which ultimately put PolyMet's water permit on hold.

Just last week, the court also placed PolyMet's permit to mine and tailings dam permit on hold after concerns were raised over whether Glencore, PolyMet's new majority shareholder, would be added to the permits and if the DNR properly considered the Brunadinho dam failure in Brazil.

That's all the more reason a hearing should be held on the issue, Carlson said.

"Not a single public hearing in the state Legislature," Carlson said during his speech. "Not one."