Talon Metals, the company proposing an underground nickel mine near Tamarack, Minn., has backed away from a novel plan that would have used a subway-digging machine to carve an underground loop to reach the ore.
Instead, Talon, which hopes to one day supply the materials for Tesla’s electric-vehicle batteries, will dig a straight path down to those minerals. The revised environmental assessment worksheet filed Dec. 12 incorporated public, state and tribal feedback, said Jessica Johnson, the vice president of external affairs for Talon.
“We’re reducing the amount of ground disturbance and the amount of rock that we need to handle and manage,” Johnson said.
By no longer using a tunnel-boring machine, Talon has sidestepped early concerns from the Minnesota Department of Natural Resources about waste rock, potential contamination of water and an untested technology for mining. But building a single, diagonal shaft underground also means that Talon will be blasting rock closer to the surface, at 100 feet below as opposed to 300 feet below.
Talon is still studying how many sulfides will be in the waste rock between the surface and the nickel it is seeking, the company said in filings. Sulfide minerals that can interact with air and water to create acid mine drainage, or release sulfates that are toxic to wild rice.
The company also abandoned a proposal to pile waste rock outside on top of liners, and now says it will store excess rock inside a central building — or ship it along with ore to a processing plant it intends to build in North Dakota.
Several parts of the facility have been moved inside this building, and the central mine shaft will also reach the surface indoors. Johnson described the concept as a “mine in a box.”
But the new design also introduces new questions, said Paula Maccabee of the environmental group WaterLegacy. She questioned how Talon would be able to supply enough fresh air for workers in the mine when the main opening is enclosed. Previously, the loop design had two openings at the surface of the ground.