REGIONAL—Representatives of Twin Metals Minnesota offered their latest vision of the company’s proposed copper-nickel mining operation south of Ely at a recent meeting of the Laurentian Vision Partnership.
It’s an early—and far from final— peek at the project as the company continues work on its prefeasibility study, a largely internal company document that forms the basis for development of a full-fledged mining plan.
Bob McFarlin, company vice president for public and governmental affairs, said Twin Metals remains in the early stages of its work. “We are still at least two years away from proposing a specific project,” McFarlin said.
Currently, the company is using a set of guidelines and principles as it explores a variety of alternative locations for some of its mine-related facilities.
McFarlin said the company is focused on minimizing surface impacts, by keeping as much of its operation underground as possible. The company is also looking seriously at locating its tailings basin southwest of the Laurentian divide, which would limit any discharge of pollutants to watersheds that feed into the Boundary Waters Canoe Area Wilderness.
The company is focusing its energies on development of an underground mine at the Maturi deposit, located along the southeast bank of the South Kawishiwi River. It’s the largest of the three deposits currently controlled by the company, with a current indicated resource in excess of 1 billion tons of ore, testing out at 0.59 percent copper, and 0.19 percent nickel. Twin Metals’ current vision calls for a concentrating plant tentatively slated for construction just south of the Ely airport. The company has yet to select the metallurgical process it might use in its concentrator, said McFarlin.
From the concentrator, the company would construct a deep underground corridor that would link the plant to the mine site, located about two miles to the east. The initial crushing would be done underground, according to McFarlin, and the crushed rock would then be transported to the concentrator through the underground corridor.
About 50 percent of the waste rock would be used as backfill in the underground mine, while the remainder would be discharged to a tailings basin. Company officials are currently considering use of a pipeline (described as a “surface corridor” on a project map) to transport tailings slurry from the concentrator to a tailings basin located just southwest of Babbitt. A separate pipeline would transport a slurry of ore concentrate to the Babbitt site as well, where it would be shipped to customers. McFarlin said the company has no plans for further refinement of the ore here in Minnesota, but will leave that to others.
Another potential pipeline would link the concentrating facility to the Dunka Pit, where the company would access water for the concentrator. The water pipeline would travel above ground for most of its path, but would be buried underground where it passes across Birch Lake.
Most of the water used in processing would be recycled, said McFarlin, although some will be discharged through the tailings and concentrate slurries.
If the company does utilize the Dunka Pit, McFarlin said Twin Metals would assume responsibility for managing any discharges from the pit, which was created by previous mining operations undertaken by LTV.
Whether any of these ideas make it into the final mine plan remains to be seen, said McFarlin. Company officials, and the public, should get a better idea, once the prefeasibility study is completed later this year.