ST. PAUL  — State officials released a 2,200-page environmental review for the proposed PolyMet Mining Corp. copper-nickel mine to the public on Friday and urged Minnesotans to scrutinize the massive document as the state decides whether to embrace a new kind of mining.

PolyMet’s proposed open-pit NorthMet mine near Babbitt and processing plant near Hoyt Lakes would be Minnesota’s first copper-nickel mining operation if it wins all the necessary approvals. It could set the pattern for environmental protections for future nonferrous mining projects in the vast, untapped copper, nickel and precious metals deposits in northeastern Minnesota.

Department of Natural Resources Commissioner Tom Landwehr urged Minnesotans to take a “hard look” at the review — posted on the agency’s website — and respond with comments, questions and suggestions for changes “so that we can make sure that what we think is a good document really is the best document possible.”

The 90-day public comment period opens Dec. 14 and runs through March 13. The process includes public forums Jan. 16 in Duluth, Jan. 22 in Aurora and Jan. 28 in St. Paul where people can weigh in.

“We know that when the public is engaged and concerned about environmental protection, good things come from that,” John Linc Stine, commissioner of the Minnesota Pollution Control Agency, said at a briefing for reporters. “We welcome their concern because it helps define better protections and results for the environment.”

Standing next to two fat binders containing the report, Landwehr stressed that it’s not a “decision-making document.” He said the hard decisions about whether and how to proceed will occur after the public comment period, when PolyMet applies for around 20 major and lesser permits from state, federal and local government agencies.

Environmentalists have raised concerns because the metals are locked in sulfide-bearing minerals that can leach sulfuric acid and other pollutants when exposed to air and water. DNR officials said the project won’t produce acid drainage, but acknowledged the wastewater from the mine and processing site may require pollution controls to remove other contaminants for as long as 200 to 500 years respectively.

Sulfates and mercury are among the concerns. Excessive sulfates are thought to choke off wild rice beds, which are important to Minnesota’s American Indians, while mercury levels are so high in some fish in the region that officials recommend limits on eating them. The review concluded the planned reverse osmosis wastewater treatment systems will result in net reductions in mercury and sulfates entering the St. Louis River, which flows into Lake Superior.

Tribes that participated in the review disputed several findings. They said it didn’t fully account for all potential sources of mercury from the operation, and they were not satisfied that it properly applied the state’s sulfate standards for protecting wild rice waters.

Also, the tribes said they think the idea of an underground mine was prematurely eliminated, even though they believe it would minimize water quality and wetlands impacts. The DNR and other agencies said they adequately considered those issues.

Critics plan to study the review, formally known as a “supplemental draft environmental impact statement,” before commenting on the details, said Aaron Klemz, spokesman for the Friends of the Boundary Waters Wilderness. He also said they plan to hold an event in Duluth on Monday.

“This document is complex but the choices that Minnesotans have are simple,” Klemz said. “Are we going to take on 500 years of water treatment and the cost that goes along with that, and the environmental risk, in exchange for just 20 years of mining?”

PolyMet estimates the project would create 360 permanent jobs and more than 600 related ones — as well as temporary construction jobs — in a struggling part of the state. The company hosted a gathering with local elected officials and labor and business groups Friday in Hoyt Lakes to celebrate the milestone.

“We are committed to an operating plan that will meet or exceed regulatory requirements, that will enable us to obtain the required permits and build and operate a safe and productive mine,” PolyMet CEO Jon Cherry said in a statement.

PolyMet hopes to start mining in early 2015, but Steve Colvin, deputy director of the DNR’s Ecological and Water Resources Division, said it’s not clear how long it will take to process what’s expected to be a large number of comments to produce the final version. Noting that regulators rejected the original environmental impact statement in 2009, he said, “the project you’re looking at today is a whole lot different” because of criticisms leveled back then.

The DNR must deem the final document adequate before the permitting phase, where the timetable is also uncertain.

“It is not a foregone conclusion that all permits will be issued. That decision comes later,” said Jess Richards, director of the DNR’s Lands and Minerals Division.