Minnesota nickel mine that would supply Tesla shelves its unusual excavation method

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.

In addition to typical dust from blasting activities underground, Talon has acknowledged to the state that some amount of silica fibers will be present in the air. Silica, when inhaled by workers in high amounts, causes an incurable and deadly lung condition known as silicosis.

The company also plans to sink two significantly smaller shafts to the underground mine to aid with airflow, according to documents.

Talon’s Tamarack Mine is only the third hard-rock mining proposal to reach environmental review in Minnesota. Two other projects near Babbitt, the Twin Metals mine the NorthMet mine proposed by the company PolyMet, have faced significant hurdles.

Talon is seeking to excavate 8.2 million tons of ore over the seven- to 10-year life of the mine. The company has also said it believes other rich nickel deposits lie near its proposed site, which could eventually create a nickel-mining district in the state. It plans to ship the ore to a still-unannounced location in North Dakota for processing, and has received a $114 million grant from the federal government to support that plant.

The company has stressed the underground mine design and lack of locally stored tailings as signs of its environmental friendliness. But many groups, including the Mille Lacs band of Ojibwe, are watching the project development closely for potential to pollute.

“We need proof beyond a doubt that this will not harm our environment,” said Kelly Applegate, the commissioner of natural resources for the Mille Lacs band. He said the tribe was reviewing the company’s latest documents.

Environmental review still in early stages. The state prepare a much more detailed environmental impact statement in the coming years.

A DNR spokesman did immediately have an answer for how long it would take the agency to review the latest submission.