Aerial view of a small river flowing through tundra.
Bristol Bay Watershed Aerial views of the Bristol Bay watershed in southwest Alaska, near the location of the proposed Pebble Mine. © Bridget Besaw


The Nature Conservancy Opposes Pebble Mine Review Outcome

People of Bristol Bay Deserve Fair Process

Based on its own scientific analysis and significant concerns about a deficient process, The Nature Conservancy has joined partners across Alaska and the country in condemning the U.S. Army Corps of Engineers Final Environmental Impact Statement (FEIS) on the proposed Pebble Mine in Bristol Bay.

The FEIS has moved this project a dangerous step closer to permitting. The Nature Conservancy strongly urges the EPA to veto the Clean Water Act permit for Pebble Mine, and we respectfully call on Congress to demand the same.

Bristol Bay and its people deserve better. They deserve a fair and thorough scientific review from the U.S. Army Corps of Engineers, and they deserve answers to the major questions left unanswered in the FEIS.

Steve Cohn State Director, The Nature Conservancy in Alaska

“Bristol Bay and its people deserve better,” said Steve Cohn, Alaska state director for The Nature Conservancy. “They deserve a fair and thorough scientific review from the U.S. Army Corps of Engineers, and they deserve answers to the major questions left unanswered in the FEIS. The Pebble mineral deposit lies in the headwaters of the planet’s most productive wild salmon streams, yet what the Corps released displays a disregard for Bristol Bay’s unmatched wild salmon resource, the generations of people who have always relied on it, and the health of a globally important, environmentally sustainable fishing industry.”

The FEIS, issued July 23, did not address questions and concerns about the scientific rigor of the process. These were formally presented by The Nature Conservancy in Alaska and others during the review process, including local tribes, regional economic organizations, and a range of federal and state agencies such as the Environmental Protection Agency and the Alaska Department of Fish and Game. 

The FEIS revealed that the mine’s construction and early operations will cause significant destruction to salmon habitat in Bristol Bay watersheds, with some impacts exceeding scientific thresholds by more than double. Beyond that, the Conservancy’s science also reveals that impacts rise exponentially when analyzing the long-term implications for water quality and the need for toxic wastewater management in perpetuity—through unproven, highly complex systems and technologies. 

The document also does not account for a potential failure of the mine’s dams to contain toxic wastewater and contaminated sediment (also known tailings), as standard industry practice dictates. TNC’s scientific analysis, in partnership with the Bristol Bay Regional Seafood Development Association and Lynker Technologies, revealed that a small dam breach would deposit tailings in 155 miles of streams and salmon habitat, and a large breach would send tailings 80 miles downstream, impacting 200 miles of salmon habitat and likely flowing all the way to the bay. 

Despite this, and despite a highly critical internal review of the dam design by AECOM, a multinational engineering firm hired by the Corps and billed as the “the world’s premier infrastructure firm,” the agency has not required that Pebble address such a potential failure. The largest failure scenario considered in the FEIS is a 6-hour pipeline break representing just .005% of the mine tailings to be stored on the site forever.

Development in this region must align with the health and well-being of Alaska Natives who have stewarded and relied upon these lands and waters for millennia.

Director of Conservation for The Nature Conservancy in Alaska

“Failing to consider this critical scenario of the dams proposed at Pebble Mine is not just scientifically inadequate; it is irresponsible given that the mine will be located in a seismically active area and will generate an extremely large quantity of toxic wastewater,” added Cohn.

By not addressing these concerns and questions, the Corps has not heeded direction from Congress. Alaska Sen. Lisa Murkowski inserted language in the 2019 Senate Appropriations bill, which Congress approved, emphasizing that “sound science must guide Federal decision making and all gaps and deficiencies identified in comments” must be fully addressed; and that “adverse impacts to Alaska’s world-class salmon fishery and to the ecosystem of Bristol Bay, Alaska, are unacceptable.”

The mine developers and the Corps also disregarded critical input from Tribes that oppose Pebble Mine. The impact statement cites an updated transportation route that runs through lands owned by many Alaska Native Corporations, who are vehemently opposed to the mine.

“It remains clear the Corps didn’t take seriously the concerns from state, federal and Tribal cooperating agencies, the public or Congress, as the document remains virtually the same as early drafts of the EIS, dangerously underestimating and ignoring the devastating impacts Pebble would have on our region,” said Ralph Andersen, Bristol Bay Native Association President and CEO.

“Development in this region must align with the health and well-being of Alaska Natives who have stewarded and relied upon these lands and waters for millennia,” said Adrianna Muir, director of conservation for The Nature Conservancy in Alaska. “A failure to consult and collaborate with these sovereign nations not only overlooks important scientific insight but also raises serious issues of environmental injustice.”

Since the mid-1990s, The Nature Conservancy in Alaska has advocated for the long-term sustainability of Bristol Bay and the future of its communities. These lands and waters produce the planet’s largest population of wild salmon, and these robust runs have been at the heart of the local way of life for thousands of years. Because so much is at stake, TNC has invested decades of effort in scientific research and participated in all public processes by providing expert comments.

The Nature Conservancy is a global conservation organization dedicated to conserving the lands and waters on which all life depends. Guided by science, we create innovative, on-the-ground solutions to our world's toughest challenges so that nature and people can thrive together. We are tackling climate change, conserving lands, waters and oceans at an unprecedented scale, providing food and water sustainably and helping make cities more sustainable. Working in 76 countries and territories: 37 by direct conservation impact and 39 through partners, we use a collaborative approach that engages local communities, governments, the private sector, and other partners. To learn more, visit or follow @nature_press on Twitter.