PolyMet on Thursday received the last permit it needs for the contentious copper-nickel mine it’s planning near Hoyt Lakes.

The U.S. Army Corps of Engineers announced Friday morning approval of a wetlands permit allowing PolyMet to discharge dredged and fill material into over 900 acres of wetlands as the company develops and builds its mine. The Corps said the project would avoid 500 acres of wetlands that PolyMet had requested in its original proposal.

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“This has been a very carefully weighed decision,” Col. Sam Calkins, commander of the St. Paul District, said in a news release.

PolyMet earned key permits from the Minnesota Department of Natural Resources and the Minnesota Pollution Control Agency in late 2018. But those permits, and a completed land exchange, are being challenged in court by opponents of the project who argue the project could send tainted runoff into the St. Louis River watershed and Lake Superior.

Kathryn Hoffman, CEO of the Minnesota Center for Environmental Advocacy, called the Corps’ approval a “permitted destruction” of wetlands, which would threaten native species and release more greenhouse gases.

“It's critical that the courts hear challenges to permits before PolyMet can start digging. Once these wetlands are destroyed, they can never be repaired,” Hoffman said.

PolyMet officials celebrated the permit in a release Friday, and said a deadline for $243 million in debt owed to global commodities giant Glencore had been extended to the end of July.

“While our immediate goal is to address the Glencore debt, we are proud to be the first mining

company to be fully permitted to responsibly build and operate a copper-nickel-precious metals

mine within the world-class Duluth Complex,” Jon Cherry, president and CEO of PolyMet, said in a news release Friday morning.

Through an offtake agreement, Glencore is set to purchase the first five years worth copper produced at PolyMet.

The company must now raise $945 million in financing for the project.

“Importantly, receipt of this final permit enables us to move forward with project financing which is expected to take several months,” Cherry said.

The company is still working on final engineering plans but some work at the former LTV Steel Mining Co. site such as well installations, asbestos abatement and drilling is already underway.

Over its 20-year mine life, PolyMet expects to mine billions of pounds of copper and millions of pounds of nickel, cobalt and other precious metals.

PolyMet spokesperson Bruce Richardson said a timeline on when construction or mining at the site would begin is not set.