Twin Metals is one step closer to officially proposing a copper-nickel mine in northern Minnesota.

Federal regulators Wednesday renewed two mineral leases held by the company, which wants to build the underground mine adjacent to the Boundary Waters Canoe Area Wilderness. It is the last step in the Trump administration's attempts to undo the Obama administration's efforts to block new mining projects near the wilderness area.

The Bureau of Land Management's renewal of the leases clears the way for Twin Metals to submit a formal mine plan of operation to state and federal officials. That filing would then trigger a multiyear state and federal environmental review and permitting process before the company can break ground on the project.

In a statement, the company said it will submit that plan "in the coming months," and said it's spent more than $450 million so far in developing the project.

The mineral leases renewed this week give the company access to the copper, nickel and other precious metals underneath nearly 5,000 acres of land in the Superior National Forest. The spot is about 9 miles southeast of Ely, Minn., along Birch Lake and the South Kawishiwi River, which flows into the Boundary Waters.

It's part of one of the largest untapped copper-nickel deposits in the world. But so far, no mines of this type have opened in Minnesota. PolyMet Mining has received all the permits it needs to begin construction on a mine that would be located about 15 miles south of the Twin Metals site, but has yet to raise the required financing.

Several conservation groups are fighting PolyMet because copper-nickel mining, unlike iron ore mining in Minnesota, can result in what's known as acid mine drainage, which can leach heavy metals into groundwater and nearby waterways.

That's why Twin Metals' proximity to the pristine lakes and rivers of the Boundary Waters has led to such fierce opposition from conservation groups and previous federal administrations' officials, who fear that copper-nickel mining within the watershed of the wilderness area could lead to severe water pollution that might prove impossible to contain.

But in announcing the decision to renew the leases for another 10 years, Joe Balash, the Interior Department's assistant secretary for land and mineral management, said mining on public lands balances conservation policies with the "need to produce minerals that add value to the lives of all Americans."

The decision was expected. In May 2018, the Interior Department announced it would reinstate the leases that the Obama administration had revoked a year and a half earlier. Then, in December 2018, the department released a draft environmental assessment of the site, signaling its intention to renew the leases for another decade.

The Bureau of Land Management received nearly 39,000 comments on its proposal, most of them in opposition to renewing the leases. The agency said those comments generally cited potential ecological degradation of the Boundary Waters from mining, as well as negative socioeconomic impacts on the surrounding area as reasons for opposing the renewal.

As a result of those comments, the bureau said it made changes to the terms of the leases. Twin Metals will now be required to submit a mine plan of operation, obtain all necessary permits and meet specific mine construction milestones — all within the 10-year term, or the leases will be terminated.

A major point of contention in the process is exactly when an environmental review of the mining proposal should happen.

Twin Metals' leases were first granted in 1966, before federal environmental laws were in place, and also more than a decade before the Boundary Waters Canoe Area Wilderness was created. As a result, proposals to mine copper and nickel near the Boundary Waters have never undergone strict review.

Bureau of Land Management officials say an environmental impact statement, which would analyze all potential environmental impacts of a mine and how the company proposes to mitigate them, will be prepared once Twin Metals submits a mine plan of operation. Officials have said that because the leases themselves won't result in mining, it's premature to conduct an extensive analysis.

Opponents of the Twin Metals mine — including Tom Landwehr, the former state Department of Natural Resources chief who now leads the nonprofit Save the Boundary Waters campaign — argue that it's not too early to be asking whether it makes sense to build a copper-nickel mine so close to the Boundary Waters.

"This is all public land, and when you look at it from the air, it is not an industrial mining site," Landwehr said. "It is unbroken forest, it is clean, pure water, and it is just unconscionable that anybody could think this is a good site for a mine."

Landwehr's group and others have already sued to overturn the Trump administration's reinstatement of Twin Metals' original leases last year, a step the government needed to take before it could officially renew the leases for another 10 years. He said they're considering now whether to also file a lawsuit to try to block this lease renewal.

But others, including Minnesota Republican Reps. Tom Emmer and Pete Stauber, praised the Interior Department's decision. Stauber, who represents northeastern Minnesota's 8th Congressional District, and Emmer, who represents central Minnesota's 6th District, joined Interior Department officials Wednesday when they signed the lease renewals.

"In northeastern Minnesota, mining is our past, present and future," said Stauber, whose district includes the proposed mine site. "We know that with modern technology, we can develop the resources that all Americans utilize and create a boon for Minnesota, while preserving our precious environment."

Twin Metals expects to "nail down its project configuration" over the next two months, and plans to share that information publicly as soon as possible, said chief regulatory officer Julie Padilla.

The company plans to submit its mine plan of operation later this year.

Meanwhile, a coalition of environmental groups, businesses and outdoor organizations believe they have a strong case in their federal lawsuit seeking to overturn the Trump administration's decision reinstating Twin Metals' leases. A decision in that case could also come later this year.