Minnesota’s first copper-nickel mine cleared its final hurdle with state regulators Thursday, while federal officials opened a path for a second mine just outside the Boundary Waters Canoe Area Wilderness.

Proponents hailed the decisions on the projects, the most significant in a generation for northern Minnesota, as key to reviving the state’s struggling mining industry, adding jobs and providing an economic boost to the region and state. Opponents, however, assailed the decisions, saying the mines will jeopardize clean water and some of the state’s most pristine wilderness areas.

Both sides are still waiting on a wetlands permit from the U.S. Army Corps of Engineers for the PolyMet Mining Corp. project.

While Thursday’s actions by state and federal officials appear to open the door for copper-nickel mining, the fight may just be moving to the courtroom.

Early Thursday, the Minnesota Pollution Control Agency announced that it had approved final air and water permits for PolyMet’s $1 billion mine and processing plant. Hours later, the U.S. Department of the Interior announced it will begin the process of renewing mineral leases for the proposed Twin Metals copper-nickel mine on the edge of the BWCA near Ely.

Both projects are highly controversial because copper-nickel mining poses greater environmental risks than the iron and taconite mining that have been part of the state’s history. Copper-nickel operations produce sulfuric acid and generate heavy metals and other pollutants. This runoff, sometimes called “acid mine drainage,” can contaminate lakes and streams.

Pete Stauber, newly elected congressman in Minnesota’s Eighth District, said the state’s review shows that PolyMet will meet or exceed every environmental standard and deserves to move forward.

“This will bring about $520 million of economic activity to northeastern Minnesota every year for a minimum of 20 years,” he said. That compares to last year’s Super Bowl, which brought about $505 million in economic activity, he said. “This is like bringing the Super Bowl to northeastern Minnesota every year.”

He said he is convinced that those new opportunities won’t be at the expense of the environment.

“We have the best environmental standards in the world,” Stauber said. “This is where we live. This is our backyard, and it’s our playground too. We don’t want to damage or harm our environment.”

But environmental groups have taken issue with the state’s review of the PolyMet project, as well as the push to renew the mineral leases near the BWCA, challenging both in court. Last month they asked the state Court of Appeals to reject crucial permits that the Department of Natural Resources had approved. They’ll review the MPCA permits and decide whether to file a court challenge to them. Earlier this year, they filed federal lawsuits challenging the Interior Department’s authority to reinstate the Twin Metals leases.

The fact that the MPCA gave its go-ahead on the project the same day the Interior Department announced its decision on the leases was not lost on environmentalists, who have said that decisions on the PolyMet project will set standards for the next copper-nickel mine.

“The important lesson for Minnesota is that we can’t make these decisions in isolation from one another,” said Aaron Klemz, spokesman for the Minnesota Center for Environmental Advocacy. “If Twin Metals receives their leases, then the next stage is to apply for a permit. What we’ve seen is how weak and vague some of our rules are. It gives us a great deal of concern whether this industry can protect air and water in Minnesota, especially delicate ecosystems that haven’t had any mining in the watershed.”

Environmental groups have argued that copper-nickel mining will permanently alter one of the most heavily visited wilderness areas in the nation. A recent analysis by a pair of Harvard economists concluded that the short-term economic benefits of the Twin Metals project would be outweighed by the negative impact of mining on recreation and tourism in the BWCA.

“The Boundary Waters is our Yellowstone, our Grand Canyon,” said Aaron Hebeisen, co-chair of the Minnesota chapter of Backcountry Hunters and Anglers. “Both from a scientific and economic point of view, it does not make sense to have a mine in that area.”

Mining interests prevail

Mining companies have long eyed the BWCA, which is next to one of the largest untapped deposits of precious metals in the world. Twin Metals Minnesota, a St. Paul-based subsidiary of the Chilean mining conglomerate Antofagasta PLC, has said that if its mining project is ultimately approved, it will build a 100-acre ore-processing facility on the banks of Birch Lake, whose waters flow north into the BWCA.

The decision by the Interior Department to renew the Twin Metals leases reverses a decision made in the closing weeks of the Obama administration and could open the door to a massive mining operation.

Becky Rom, who grew up in Ely and is chairwoman of the Campaign to Save the Boundary Waters, one of the environmental nonprofits fighting the Twin Metals project, said the decision runs counter to the popular will of Minnesotans. During a public comment period last year, more than 117,000 comments supported a ban on mining within the Boundary Waters watershed.

“They are saying to the public, ‘We don’t care what you think,’ ” Rom said. “ ‘We don’t care what the science says and what the law says.’ ”

The decision to begin the process of renewing the leases for Twin Metals marks a dramatic turn in the proposed project’s long and contentious history. In 2016, the Interior Department’s Bureau of Land Management terminated the leases when, after years of study and public comment, the former chief of the U.S. Forest Service concluded that a copper-nickel mine in the same watershed as the BWCA “might cause serious and irreplaceable harm to this unique, iconic, and irreplaceable wilderness area.”

Gov. Mark Dayton lashed out at the Twin Metals decision, saying it was “driven by greed and willful ignorance” in the Trump administration. “The Boundary Waters Canoe Area is a priceless, irreplaceable environmental asset for our state and nation that must be protected,” he said. “Endangering its pristine waters and natural wonders for the sake of foreign corporate profits is shameful and wrong.”

Still, any mining at the Birch Lake site might be years away. Twin Metals has yet to submit a formal mining plan, which would have to go through an extensive environmental review.