Editor's Note: This story has been updated with comments from Twin Metals.

ELY— A broad coalition of over 170 businesses, conservation organizations, and sportsmen’s groups from around the U.S. have voiced their opposition to the recent renewal of federal mineral leases for Antofagasta’s proposed Twin Metals copper-nickel mine on the Superior National Forest.

The businesses, ranging from large national brands like Patagonia to dozens of small, independently-owned companies in northeastern Minnesota, along with groups like Backcountry Hunters & Anglers and the Boundary Waters Business Coalition, have submitted letters to federal Interior Secretary Ryan Zinke and Agriculture Secretary Sonny Purdue requesting an immediate suspension of all mineral development activities on federal lands in the Rainy River watershed while a two-year study of a proposed 20-year mineral withdrawal is completed.

The organizations submitted their letters in response to the May 2 reinstatement of two federal mineral leases located near the Boundary Waters Canoe Area Wilderness that date back to 1966. Secretary Zinke approved the lease reinstatements despite a two-year federal moratorium on the issuance of new leases while the U.S. Forest Service conducts a study of the risks associated with sulfide mining within the watershed of the 1.1-million-acre wilderness, a region renowned for pristine water quality. The two-year study, which is expected to be completed by the end of the year, will be used to determine if mineral leasing and mining should be prohibited from about 234,000 acres of federal lands within the BWCAW’s watershed for the next 20 years.

“The Boundary Waters forms a part of our public lands heritage whose importance is impossible to quantify, providing opportunities to hunt, fish, canoe, hike and camp in a wilderness setting that is accessible to all,” said Land Tawney, President and CEO of Backcountry Hunters & Anglers. “Folks from 5 to 95 years-old can experience this world-class resource. For years now, hunters, anglers, and others have been engaged in exposing the threat posed by the proposals to develop large-scale mines within the Boundary Waters watershed. We’re not about to back down now. These iconic public lands must be conserved.”

Twin Metals spokesperson Bob McFarlin said the company’s mining proposal is not threatening the wilderness and argued that opponents of the project are “fighting facts with fear.” He continued: “There is no mining being proposed or contemplated within the Boundary Waters Canoe Area or its state and federal protective buffer zones, and mining in those areas is prohibited under state and federal law. Any mining proposal in the region in areas where mining is allowed and encouraged will be subject to rigorous, multi-year, project-specific environmental study per the Environmental Impact Statement process conducted by multiple state and federal agencies.”

The groups opposed to the project say that the proposed mine will pose significant risks to the wilderness, both from potential acid drainage as well as from the impacts of adjacent industrialization. Sulfide mining does have a checkered history in the U.S., many with longstanding histories of environmental damage.

Opponents note that Twin Metals has been exploring several sulfide-based deposits along what’s known as the Duluth Complex, including one located directly adjacent to the wilderness boundary, so the impact of their project could go well beyond a single mine.

Organizers with the Ely-based Campaign to Save the Boundary Waters, which helped coordinate the latest letter-writing effort, have indicated they also plan a legal challenge to the mineral lease reinstatement. That lawsuit could be filed later this month, and it is expected to cite previous legal determinations by the Interior Department that found that the federal government had discretion on whether to renew the Twin Metals leases and a determination by the Forest Service that allowing sulfide mining within the BWCAW’s watershed posed high risks to water quality in the wilderness.

McFarlin, in a statement, said those previous determinations were based on “legal error,” by the Obama Interior Department. “The reinstatement of the leases corrected the error and allowed the proper lease renewal process to resume,” said McFarlin. “The organizations that signed letters to Secretary Perdue and Secretary Zinke today are requesting that the legal error, and the denial of legal rights stemming from the error, be allowed to stand.”

Opponents of the project note that Boundary Waters is America’s most visited wilderness, encompassing more than 1,100 pine-studded lakes located within a glacially-carved landscape containing thousands of miles of interconnected waterways and over 1,200 miles of designated canoe routes. Tens of thousands of outdoor recreationists from around the world come to the Boundary Waters each year to paddle, fish, hike, ski, observe wildlife, and camp. “The Boundary Waters is a national treasure— a crown jewel of our public lands system, owned by every single American,” said Lisa Pike Sheehy, Vice President of Environmental Activism for Patagonia. “We simply can't afford to let a foreign mining conglomerate with a long history of pollution put an industrial copper mining pit less than a mile from one of America's most popular wilderness areas.”

The groups are also responding to an updated Twin Metals proposal released May 24, in which the company indicated plans to locate its processing plant near the shores of Birch Lake, east of Babbitt. “If allowed to mine, it would locate a processing plant, a major source of water pollution, on the banks of Birch Lake, a popular fishing and recreation lake that flows into the Boundary Waters,” stated the groups in a press statement issued May 31.

“The Boundary Waters Canoe Area Wilderness is the most visited wilderness area in America, helping to support 18,000 jobs and pumping $852 million in sales revenue to the region. This should be reason enough for the administration to push pause on the rush to approve controversial new mineral leases there and wait for sound scientific studies of the potential impact to be completed,” said Amy Roberts, Outdoor Industry Association Executive Director. “The administration shouldn’t be in the business of fast-tracking the interests of mineral developers at the expense of wildlife, outdoor recreation, rural economies and the future of our public lands."

McFarlin said Twin Metals is committed to protecting the region’s environment. “Twin Metals Minnesota recognizes environmental stewardship as a core value and strives to be a leader in protecting Minnesota’s wilderness, natural environment, and recreational and cultural resources,” he said.