MINNEAPOLIS — A plan for Minnesota’s first copper-nickel mine passed a major milestone Thursday with the Department of Natural Resources approving the project’s final environmental review, meaning the company can now start pursuing the long list of permits it needs to move forward.

DNR Commissioner Tom Landwehr said he determined that the 3,500-page environmental impact statement for the proposed PolyMet mine in northeastern Minnesota meets all the legal requirements. If the project is built as described, he said, “we will meet standards … intended to protect public health and the environment.”

The approval lets PolyMet Mining Corp. begin applying for the more than 20 permits it needs to build the mine near Babbitt and processing operations six miles away near Hoyt Lakes, at the site of the former LTV Steel taconite plant that has been closed since 2001.

“That’s where the real environmental review, as far as I’m concerned, is going to take place,” Gov. Mark Dayton said of the permitting process.

Landwehr declined to speculate on how long securing those permits might take but said PolyMet must have several permits in hand “before they can put a shovel in the ground.”

PolyMet and its backers have promoted the project as a boon to the economically depressed Iron Range. More than 2,000 workers have been laid off from Minnesota’s iron mining companies in the past year, while the governor’s office estimates that more than 3,000 other people have lost jobs at companies that serve the industry.

The company’s president and CEO, Jon Cherry, called it “a huge day” for the Iron Range and the state. He said the decision opens the doors to perhaps 100 years of copper-nickel-precious metal mining in the region.

PolyMet said the project will directly generate up to 500 temporary construction jobs and about 360 permanent jobs that will pay about $36 million in annual wages and benefits, as well as support hundreds of jobs indirectly.

But environmental groups consider PolyMet a threat to nearby pristine areas and water supplies — and a precedent. PolyMet’s experience is expected to set the pattern for approval of future projects including the proposed Twin Metals mine near Ely, which would be close to the Boundary Waters Canoe Area.

“This project cannot be permitted. It violates state water quality standards. It violates the (federal) Clean Water Act,” said Paula Maccabee, an attorney for WaterLegacy, one of several group working together to fight the project.

Dayton said he remains “genuinely undecided” on the final decision of whether the mine will ultimately be allowed.

“We’re glad to see Gov. Dayton saying he’s going to take a hard look. We’re disappointed that the DNR did not address the issues it should have addressed,” said Aaron Klemz, spokesman for Friends of the Boundary Waters Wilderness.

PolyMet began its initial environmental work in 2004. But the original impact statement, released in 2009, drew a poor review from the U.S. Environmental Protection Agency. The project was then extensively redesigned to address water quality, waste rock disposal and other concerns. The final version was released in November.

Cherry said permitting should go significantly faster than the environmental review.