Twin Metals Minnesota, the company that plans to open an underground copper-nickel mine on the doorstep of the Boundary Waters Canoe Area Wilderness, has submitted formal plans to state and federal officials Wednesday, marking the start of what promises to be a long and contentious public review process that will determine whether the controversial project can proceed.

The move was expected; state officials signaled earlier this month that they anticipated Twin Metals would submit its mine plan of operation before the end of the year. 

Still, it represents a significant step forward for the company, which has invested more than $450 million and more than a decade of work to get to this point.

The documents, submitted to the Minnesota Department of Natural Resources and the U.S. Bureau of Land Management, lay out in detail how Twin Metals plans to mine copper, nickel and precious metals deep beneath the Superior National Forest. 

They also outline how the company proposes to mitigate the project’s environmental impacts, including potential severe water pollution that could flow into the nearby wilderness.

While Twin Metals has revealed major aspects of the proposed operation in the past, some new details emerged in today’s filing:

  • The company is now predicting the mine would create 765 jobs over its expected 25-year life. That’s an increase from earlier projections of 700 positions, and is related to Twin Metals’ revised plans to store the mine’s tailings — finely crushed waste material left over after the minerals are extracted from the ore — using an approach known as dry stacking.

  • The mine would be accessed by two tunnels, 20 feet by 20 feet and 1.25 miles long, sloping downward to the ore body. Conveyor belts would carry crushed ore to the surface, where it would be processed into metal concentrates at a nearby processing plant. There would be lighting, ventilation, office space and places for employees to gather deep underground.

  • While the ore body extends under Birch Lake, Twin Metals now says it does not plan to mine underneath the lake, to limit the potential for environmental impacts and for overall mine stability. Most mining would occur from 400 feet down to a depth of potentially about 4,500 feet. 

  • Twin Metals predicts it would not discharge any water from its mine site, and therefore won’t need to build a wastewater treatment plant. That claim will be tested during the environmental review process.

 The official project submission triggers the start of the environmental review process, in which state and federal regulators will analyze in detail how the company proposes to mine and how it plans to mitigate its environmental impacts.

The Minnesota DNR announced last month it will conduct its own review of the project, rather than collaborate with federal officials, as it did with the recent PolyMet Mining proposal. The DNR said that’s the best way to ensure a thorough, scientific and neutral review.

The Bureau of Land Management will conduct the federal review. Members of the public will have several chances to comment on the project throughout the process.

Twin Metals chief regulatory officer Julie Padilla estimates that environmental review and permitting could take five to seven years. The environmental review creates the source documents for the permitting process — the final stage in which state and federal officials decide whether to grant the permits the mine would need to open.

It took nearby PolyMet Mining — which won its approvals from state and federal officials last year and is poised to become Minnesota’s first copper-nickel mine — about 14 years to navigate that process.

“It's an opportunity that every business in this state should have,” Padilla said, “the ability to put a project forward for review and input and ultimately a decision by state and federal agencies on whether we meet the meet and exceed those standards that are in place.”

But even before Twin Metals submitted its formal plan, the mine’s opponents, including former DNR commissioner Tom Landwehr, staged a rally at the State Capitol in St. Paul Tuesday. 

They’re urging Gov. Tim Walz to direct his agencies to refuse to review the project until the federal government releases the findings from a study of the environmental impacts of copper-nickel mining within Boundary Waters watershed that was canceled by the Trump administration last year.

“The buck stops with Gov. Walz,” said Lukas Leaf, executive director of Sportsmen for the Boundary Waters. “He can and should protect the Boundary Waters by halting any of his department's actions to permit the proposed Twin Metals project.”

A 21st century mine?

If approved, the Twin Metals project would be the first underground mine to operate in Minnesota in more than 50 years, since the Pioneer iron ore mine in nearby Ely closed in 1967. “And we're doing it with 21st century technology,” said Padilla.

In its formal proposal filed Wednesday, Twin Metals’ says its research has shown that the mine would not produce what’s called acid mine drainage. That’s a kind of major toxic pollution that these types of hard-rock mines have historically left in their wake.

The metals are bound up in ore that contains sulfides. When those sulfides are exposed to water and air, they produce sulfuric acid, which can leach heavy metals into surrounding groundwater and surface water.

That’s why the Twin Metals proposal in particular has been so divisive. Since it’s located only five miles from the southern edge of the Boundary Waters Canoe Area, and within the wilderness watershed, near the shore of the South Kawishiwi River and Birch Lake, any pollution from the mine would have a very short pathway to reach the Boundary Waters.

And if it gets there, said Landwehr, who now leads the Save the Boundary Waters Campaign, “there is no remediation. You can't go into the Boundary Waters with a water treatment plant and re-purify the water. The damage that happens to the Boundary Waters is forever.”

Twin Metals also plans to use a method of mine waste storage called dry stacking, which environmental groups have supported in the past. That approach eliminates the need for the giant dams typically used to hold back a basin filled with a wet slurry of the mine waste tailings. In recent years, dam failures at mines in Canada and Brazil have caused catastrophic environmental damage.

According to the plan, about half the tailings left over from the Twin Metals mine will be mixed with cement and used to backfill and stabilize the mine. Company officials say there won’t be any need for waste rock storage piles on the surface, further minimizing the possibility of pollution.

“I'm confident that we can meet and exceed all of the regulatory standards in place,” said Padilla. “We believe that we can protect the environment and mine.”

For environmental groups, state rules aren’t enough

But groups fighting to stop Twin Metals argue that state environmental standards aren’t sufficient to stop pollution from reaching the Boundary Waters, since they would allow for some degradation of the wilderness’s pristine waters.

They also argue that Twin Metals Minnesota, a subsidiary of the Chilean mining giant Antofagasta, never should have been able to reach this point in the process.

In the waning days of the Obama administration, the federal government rescinded key mineral leases in the Superior National Forest that are central to Twin Metals' plans. The U.S. Forest Service at the time also proposed a 20-year moratorium on any new mining projects within the Boundary Waters watershed, citing unacceptable risks to the wilderness.

But since then, the Trump administration has reversed all those actions. The U.S. Bureau of Land Management first returned the mineral leases to Twin Metals, and then renewed them for 10 years.

“I would still assert that this project should not be even alive right now, because it was officially killed in 2016,” Landwehr said.

Environmental groups and businesses filed a lawsuit challenging the government’s reinstatement of those leases. A hearing is scheduled in federal district court in Washington this Friday.

The government also canceled a study on the proposed mining ban after 20 months of work on it, and has refused repeated calls from members of Congress to release it. Just this week language that would have required the administration to finish the study was removed from an Interior Department appropriations bill.

Landwehr speculated the documents likely conclude that the Twin Metals project should not be allowed to proceed. “They wouldn't be withheld if they said the project should be approved,” he said.

In a statement, Walz spokesperson Teddy Tschann said “the Boundary Waters is deeply — and personally — important to Governor Walz.”

But he did not respond directly to Twin Metals opponents’ request that he halt the review process of the mine. “The Governor believes that no mining project should move forward unless it passes a strict environmental review process that includes meaningful opportunities for public comment.”

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