Republican senators voted Thursday to allow new mining projects near the Minnesota Boundary Water Canoe Area Wilderness, one of the most visited and expansive stretches of wilderness in the United States. 

The resolution, which passed in a narrow 50 to 49 vote, would repeal a Biden-era 20-year moratorium on mining across the roughly 350 square miles that make up the Superior National Forest, which includes the Boundary Waters.

This vote is victory for Twin Metals Minnesota, a subsidiary of the Chilean mining conglomerate Antofagasta, which has proposed plans to build a copper and nickel mine five miles from the wilderness area and within the watershed of the Boundary Waters. 

Twin Metals has worked for more than a decade to establish a mine along Birch Lake, as environmental groups have fought back to block their proposal over the years because of the risk of heavy metal contamination it poses to Northern Minnesota’s Great Lakes. 

Minnesota Sen. Tina Smith led the Democratic opposition against the measure, which was introduced and passed in the U.S. earlier this year by Duluth native Rep. Pete Stauber (R-Minn.). 

Stauber called the Senate vote on Thursday “a major victory for America and Minnesota’s 8th Congressional District” on social media. 

Smith spoke for nearly five hours Wednesday evening in an attempt to block the vote. 

“You may be wondering why I am standing here at nearly midnight keeping everyone up. Here’s why: Because I know people in Minnesota are wondering whether anybody in this building cares about what they think,” Smith said. 

Smith, joined by other Senate Democrats, spoke again on Thursday morning, calling on their Republican colleagues to oppose the repeal prior to it passing. 

Smith said in a press conference following the vote that she is deeply disappointed, but the fight continues. She added that opponents to mining near the Boundary Waters are currently weighing their legal options. 

“I would anticipate that there will be outside groups who have standing in this issue, who may well decide that this is something that they need to file a lawsuit on, because the Senate and the House should follow the law,” Smith said.

The measure is headed to President Donald Trump, who is expected to sign the resolution into law.