MINNEAPOLIS (AP) - A proposal for Minnesota's first copper-nickel mine takes a crucial step forward Friday.

That's when regulators release an environmental review that's certain to fuel the debate over whether the state can gain the hundreds of jobs a new era of mining could bring without sacrificing cherished waters.

Regulators sent PolyMet Mining back to the drawing board in 2009 when they rejected the original environmental impact statement for the planned open pit mine near Babbitt and processing plant near Hoyt Lakes.

The upcoming version has grown to around 1,900 pages, and PolyMet says it's confident the document will show that it can operate without harming the environment.

But environmental groups aren't reassured by recent drafts, particularly the suggestion that PolyMet's wastewater may require treatment for up to 500 years.