Regulators have begun work on a new document to supplement environmental studies for PolyMet Mining's controversial copper-nickel mine near Hoyt Lakes.
PolyMet's initial draft Environmental Impact Statement got a cold reception from the Environmental Protection Agency.
The EPA raised concerns about wetlands, water quality and a land exchange between PolyMet and the U.S. Forest Service.
PolyMet Mining spokeswoman Latisha Gietzen says the new supplemental review will address EPA's concerns, because the EPA is helping to write the new document.
"EPA is coming into this process as a cooperating agency, and so they're at the table participating in the background discussions and work on the supplemental [report]," she said.
Mine opponent Paula Maccabee with the group WaterLegacy says she's concerned about language indicating the mine might expand beyond the initial 2,800 acres.
"Is this opening the door for destruction of not just 2,000-plus acres of wetlands and uplands in the National Forest, but as much as 6,500?" Maccabee asked.
Opponents also fear the mine will produce damaging acidic runoff.
The supplemental environmental document could be finished next summer.