MINNEAPOLIS — The Department of Natural Resources wasn’t taking chances when it picked a site for the first of three public forums on a proposed copper-nickel mine in northeastern Minnesota: It booked one of the largest venues the region.

And the agency may need all the space it has reserved in the Duluth Entertainment Convention Center for tonight’s meeting on PolyMet Mining Corp.’s proposed mine near Babbitt and processing plant near Hoyt Lakes. Passions run deep on both sides. The Jobs for Minnesotans coalition of business and union groups has chartered seven buses to help bring what they promise will be more than 500 people from the Iron Range to Duluth for a show of force. Opponents hope to turn out a roughly equal crowd. The space will seat about 1,500.

The open house and hearing are intended to give the public a chance to learn about the mine proposal and, more specifically, to comment on a massive draft environmental review for the project, which the DNR released last month. But the discussion may go well beyond the narrow topic of whether the nearly 2,200-page analysis of the project is sufficient and expand into a broader debate about whether Minnesota should even enter a new era of copper-nickel mining.

The DNR is hopeful of keeping the discussion focused on the environmental review and has worked hard to explain the purpose of the meeting, spokesman Chris Niskanen said. DNR Commissioner Tom Landwehr made the rounds of newspapers and broadcasters in northeastern Minnesota last week to appeal for a civil discussion that concentrates on the document, saying the meeting is not meant to be a referendum on mining.

“If folks want to get up and say what they think about the project as a whole without being too specific and technical, that should be their right as well,” said Aaron Klemz, spokesman for the Friends of the Boundary Waters Wilderness, one of several groups arguing that the environmental risks are too high. But he also said he hopes the discussion will be calm. “I think this meeting will be a real shame if it ends up with people on two sides of the room yelling at each other,” he said.

PolyMet is grateful for the anticipated high turnout from the Iron Range, spokesman Bruce Richardson said.

“It’s really quite humbling to hear about the people who are supportive of this. I think it’s good for everyone to see where the support is. These are folks that understand mining,” Richardson said.

Similar meetings are scheduled for Aurora on Jan. 22 and St. Paul on Jan. 28. The DNR is also taking written comments through March 13. After the agency digests all the comments and publishes the final document, it would begin a separate process for issuing the necessary permits, which would also allow for public comments.