In a year notably short on good news, activists in northern Minnesota—and wilderness lovers nationwide—were overjoyed to learn Thursday morning that the Obama administration had denied mining lease applications next to the Boundary Waters Canoe Area. Citing more than 30,000 public comments, many expressing concerns about acid mine drainage, the U.S. Forest Service and the Interior Department jointly denied the Twin Metals Minnesota application to renew its leases on two potential mine sites, one directly adjacent to the BWCA and the other three miles away. 

“It’s wonderful news,” says Luther Dale, a member of the Sierra Club’s North Star Chapter executive committee who has worked on the issue for the past two years. “It’s a great example of the Sierra Club partnering with other organizations in the preservation of something so important to the American people.”           

Conor Mihel documents the effort to save the 1.1-million-acre wilderness area from destructive mining in “Protecting the Boundary Waters Canoe Area,” from the current issue of Sierra: 

A place that's half land and half water is the absolute worst location for a new mine, critics insist. Antofagasta [Twin Metals' parent Chilean parent company] is targeting deposits of copper and nickel buried in sulfur-bearing bedrock. Such mines are essentially waste-management industries. The Twin Metals deposit, for example, contains barely 0.5 percent copper. The rest of the worthless ore would be stored in rock piles mounding across an area the size of 100 football fields. Finer, chemically processed materials would be quarantined in tailings ponds.  

Problems arise when the sulfur in waste materials reacts with air and water to produce sulfuric acid, a process known as acid mine drainage. Heavy metals like arsenic, cadmium, and mercury are more likely to leach out of rock in acidic conditions. Acid mine drainage is almost impossible to prevent and can happen at any time—even long after a mine has been closed. . . . The EPA calls the mining of sulfide ore America's most toxic industry. In 2010, such mines accounted for 41 percent of all toxins released into the environment. "It is not a question of whether, but when, a leak will occur that will have major impacts on the water quality of the Boundary Waters Canoe Area," says Tom Myers, a hydrogeologist and water resources consultant. 

Antofagasta/Twin Metals’ claims are located on federal land on the southern end of the BWCA watershed, near the town of Ely, and date back to 1966. The company failed to develop the copper-and-nickel-rich claims, however, and the leases expired in 2013. The company then sought to renew them, but that application was rejected in today’s action. 

“Today’s best available science is helping us understand the value of the land and water and potential impacts of development in places like the Boundary Waters,” said Interior Secretary Sally Jewell. “This is the right action to take to avoid irrevocably damaging this watershed and its recreation-based economy, while also taking the time and space to review whether to further protect the area from all new mining.” 

The Forest Service is also proposing further protection for the BWCA by applying to withdraw portions of the watershed that feeds it from mining development for the next two years, with the possibility of an extension to 20 years. Boundary Waters activists are now setting their sights on a permanent mining ban. “We’re hopeful that this will lead to full protection of the Boundary Waters as America’s most popular wilderness,” Dale says.