VIRGINIA, Minn. — Twin Metals Minnesota says the copper, nickel and precious metals mining projects that it is planning for the Ely area of northeastern Minnesota would keep the company in business for more than a century.

Bob McFarlin, vice president of public and governmental affairs for Twin Metals, said much planning remains ahead and it’s still not clear when the company might start mining.

“No final decision has been made. These are preliminary for our first operation,” McFarlin said.

The company identified sites in the Ely and Babbitt areas as major components of its first operation. But McFarlin said the company also plans other projects in the mineral-rich Duluth Complex, which would keep the company in business on the Iron Range “well in excess of a century,” he said.

Twin Metals is currently in the “pre-feasibility” phase of the project.

A feasibility study, and an extensive environmental review and permitting processes will follow.

Another project is much farther along in the process. PolyMet Mining Corp. wants to build the state’s first copper-nickel-precious metals mine near Babbitt and convert a former taconite processing plant near Hoyt Lakes. The public comment period closed earlier this month on the latest environmental review for PolyMet.

Both PolyMet and Twin Metals have drawn opposition from critics who say such mining poses new threats to the Minnesota environment because the nonferrous metals are locked in sulfide-bearing minerals that can leach acid and other pollutants when exposed to air and water.

Twin Metals’ preliminary plan calls for starting with an underground mine 1,500 to 3,000 feet below the surface in what the company calls the Maturi Deposit near Birch Lake, rather than its nearby Spruce or Birch deposits, McFarlin said.

A site near the Ely airport, west of the deposit, is being considered for the mine access and other facilities, he said. Underground corridors would connect facilities to the mine to minimize surface impacts. The operation would draw water from a closed iron mine known as the Dunka Pit rather than tapping underground sources or Birch Lake. Half of the tailings would be reburied in the underground mine.

The other half potentially would be stored in a surface facility south of Babbitt, which would put it in a watershed that eventually flows into Lake Superior rather than into the Boundary Waters Canoe Area Wilderness.

Twin Metals currently has 40 employees, split evenly between its Ely-Babbitt and St. Paul offices. The company has already put about $250 million into the project and could provide a total $2.5 billion capital investment, McFarlin said.