– Throngs of Minnesotans turned out Thursday night to join the conversation about what could be the most contentious environmental issue the state has faced in decades — its first proposed copper-nickel mine.

An estimated 1,300 to 1,500 people braved blowing snow and low temperatures to attend a five-hour public hearing held by the Department of Natural Resources (DNR) and federal agencies to present details of a project that could define the future of the wildest and most beautiful corner of the state.

PolyMet Mining Corp. of Canada has proposed a $650 million open pit mine near Babbitt, on the eastern edge of Minnesota's storied Iron Range. It is just the first of many minerals companies lining up to tap one of the world's largest untouched deposits of copper, nickel and other such metals that lie beneath the forests and lakes of northeast Minnesota. Thursday's event was the first of three public hearings to debate the plan.

People started streaming into the Duluth Entertainment and Convention Center before 5 p.m., and the building soon had all the noise and flavor of a political convention — only this time two opposing factions occupied the same space. Signs, however, were not allowed to be posted. Most sported stickers that said either "I support jobs," or "Who Pays for Pollution?"

Brian Rebel was there to support PolyMet and represent his company, Ziegler Inc., of Minneapolis, which sells heavy equipment.

Speaking of PolyMet executives, he said, "These people know what they are doing. They are not going to do anything that would be negative in their own back yard."

About 1,500 people jammed a meeting room at the Duluth Entertainment and Convention Center Thursday night, Jan. 16, 2013 for the first public hearing about Polymet Mining's proposed open pit mine near Babbitt.

But John Schmidt of Duluth said the environmental risks of a new mining endeavor are too great.

"We made a commitment that we would leave this place a better place. There are too many unanswered questions," he said.

In a sprawling conference room on the main floor, the DNR and other agencies staffed tables and booths with detailed maps and technical information on air emissions, wetlands, mercury, water quality and other natural resource issues.

American Indian tribes from the region, who have disputed several conclusions by public regulators, were also allowed to present their views during an open house before the formal hearing.

"This is a sign of progress," said Nancy Schultz, environmentalist for the Fond du Lac Band of Chippewa.

About a dozen environmental groups, which say copper-nickel mining carries unacceptable risks for the St. Louis River watershed and Lake Superior, planned to pack the auditorium with bird-watchers, anglers, campers and some of the thousands of Minnesotans who have already registered their opinions through the DNR's public-comment period, which began in December.

About 500 people from the Iron Range arrived on seven buses provided by Minnesotans for Jobs, a pro-mining organization created by the Minnesota Chamber of Commerce, several labor unions, Minnesota Power and other business interests. Each one was greeted at the door with a handshake and "glad you could come down," from someone wearing an "I support mining" sticker.

Starting at 7 p.m., one by one, people stood to speak. They were chosen at random and were allowed to speak for three minutes.

DNR Commissioner Tom Landwehr and top-ranking officials from the Superior National Forest and the U.S. Army Corps of Engineers listened but did not respond.

The speakers were a cross-section of Minnesota: A former legislator, a resort owner from Ely, a young woman who lived in the woods with her family, environmentalists and retirees, among others. And after each one finished, half the room erupted into applause.

The prospect of hundreds of years of water treatment was a recurring theme.

"The lack of common sense and stupidity of it is breathtaking," Jane Whiteledge said. "That we would consider fouling our water forever."

But so was the need for jobs.

"Ely can't survive on tourism alone," said Joe Baltich, the resort owner from Ely. "Another slice of the pie is mining."

By the time the meeting concluded, about 80 people had had a chance to speak.

Next: Permits?

Between 1,300 and 1,500 people brought their opinions on the mine to the Duluth Entertainment and Convention Center on Thursday.

At issue Thursday was a DNR forecast — a dense, 2,200-page environmental impact statement released in December that took five years and cost PolyMet about $22 million — of the project's effect on northeastern Minnesota.

That analysis, together with public comments, will lay the foundation for decisions by the DNR next year on whether to grant PolyMet the permits that would allow the project to proceed.

In an election year, there are strong political overtones as well, with Gov. Mark Dayton and other public officials trying to find a balance between the demands of environmentalists and those of the labor and industry communities.

Many environmentalists are alarmed about potential new risks. Unlike taconite, which has long been mined on the Iron Range, the precious metals of hard-rock mining are found in ore that contains sulfide. When exposed to air and water, sulfide can create acid drainage that leaches heavy metals and mercury from rock. The acidity can destroy aquatic life.

State officials and PolyMet executives say that only 30 percent of the ore that PolyMet would mine is high in sulfide and that there is reliable technology to prevent acid generation and protect the region's natural assets.

But critics say that even the most-sophisticated mining and water-quality technologies can fail, and that large quantities of waste rock will generate additional pollutants such as heavy metals and sulfate, which is harmful to wild rice and other aquatic plants.

The DNR's public comment period continues through March 13. The remaining hearings will be held at Mesabi East High School in Aurora on Jan. 22 and at the St. Paul RiverCentre on Jan. 28.