The US Senate voted 50-49 last week to overturn a 20-year federal mining ban on 225,378 acres of the Superior National Forest in Minnesota. The resolution now heads to President Trump, who is expected to sign it.

Why it matters

The vote opens the door for Twin Metals Minnesota, owned by Chilean conglomerate Antofagasta, to build a copper-nickel mine near Ely. The Boundary Waters Canoe Area Wilderness draws more than 250,000 visitors a year and sits directly downstream from the proposed mine site.

The case for mining

Supporters say the project will create hundreds of jobs in northern Minnesota’s Iron Range, where mining has been the economic backbone for over a century. Republican Congressman Pete Stauber, who introduced the House version, called the minerals “essential to national security and the clean energy transition.”

Copper, nickel, cobalt and platinum deposits beneath the forest are among the world’s largest undeveloped reserves. Proponents argue modern underground mining techniques can extract them without surface damage.

The case against

Opponents say copper-sulphide mining has never been done in Minnesota without polluting nearby water. Environmentalists warn that acid mine drainage will flow through the watershed into the Boundary Waters, contaminating lakes with mercury and sulphides.

The Lac La Croix First Nation and Minnesota Chippewa Tribe oppose the project. Basswood Lake, which borders the proposed site, is an ancestral homeland and sacred place for Anishinaabe people. Wild rice, central to tribal culture and diet, is particularly vulnerable to water contamination.

Senator Tina Smith delivered a lengthy floor speech opposing the measure, calling it “an irreversible decision about an irreplaceable place.”

The vote

Two Republicans crossed party lines. Susan Collins of Maine and Thom Tillis of North Carolina warned the Congressional Review Act was being used in an “irregular” way that could set a precedent against future Republican land protections. All Democrats present voted against.

What happens next

Trump’s signature is expected within days. Twin Metals must still complete an environmental review and obtain state and federal permits, a process that could take several years. Environmental groups have signalled they will challenge the permits in court.