A coalition of environmental and other groups has asked for twice as much time as originally set to review a voluminous environmental impact statement for the proposed PolyMet Mining Corp. copper-nickel mining project in northern Minnesota.

Steve Morse, executive director of Minnesota Environmental Partnership, said he thinks the public needs more than the current 90 days to review and comment on the 2,200-page statement, which was released Dec. 6.

The PolyMet proposal calls for three open-pit mines on land 6 miles south of Babbitt in the Superior National Forest, which the statement describes as "relatively undisturbed." The operation would continue for 20 years and bring 350 jobs. The proposal also calls for a land swap of more than 6,000 scattered acres between the company and the U.S. Forest Service.

In October, state regulators announced they had determined that the mine would create water pollution for up to 500 years and require billions of dollars in long-term cleanup costs.

An initial environmental impact statement was published in 2009; the one released Dec. 6 was a "supplement" to that.

In a letter Friday to the Minnesota Department of Natural Resources, the U.S. Forest Service and the U.S. Army Corps of Engineers — the lead agencies reviewing the proposal — Morse asked for a 180-day comment period, which would extend into June.

Morse said he is confident the agencies will grant the extension, given the complexity of the proposal. Spokespeople for the agencies Friday said they are willing to discuss it. Among the groups seeking the extension is the League of Women Voters.

DNR spokesman Chris Niskanen said the size of the statement and objections to the 2009 environmental impact statement were taken into consideration in establishing the 90-day review. Forty-five days is the typical length for public comment periods on environmental impact statements, including the controversial Keystone pipeline, Niskanen noted.

"As the objective analyzer, we had all our best scientists look at this," Niskanen said about the five-year, $22 million process of drawing up the supplemental document.

Nearly 3,000 comments have already been received online and via e-mail since the public comment period opened Dec. 13, Niskanen said Friday. Public hearings have been scheduled for:

• Jan. 16 at the Duluth Entertainment Convention Center.

• Jan. 22 at Mesabi East High School in Aurora.

• Jan. 28 at the St. Paul RiverCentre.

Other details of the project, hearings and comment process are available at the DNR's website, www.startribune.com/a2536.

Bill McAuliffe • 612-673-7646