The move by the agency, heralded by Alaska Native tribes and environmentalists who have long pushed for it, deals a potentially devastating blow to the proposed Pebble Mine and comes while an earlier rejection of a key federal permit for the project remains unresolved.

Pebble Limited Partnership CEO John Shively in a statement called the EPA’s action “unlawful” and political and said litigation was likely. Shively has cast the project as key to the Biden administration’s push to reach green energy goals and make the U.S. less dependent on foreign nations for such minerals.

The Pebble Limited Partnership, the developer behind Pebble Mine, is owned Canada-based Northern Dynasty Minerals Ltd.

Tuesday’s announcement marks only the 14th time in the roughly 50-year history of the federal Clean Water Act that the EPA has flexed its powers to bar or restrict activities over potential impacts to waters, including fisheries.

EPA Administrator Michael Regan said his agency’s use of its so-called veto authority in this case “underscores the true irreplaceable and invaluable natural wonder that is Bristol Bay.”

The veto is a victory for the environment, economy and tribes of Alaska’s Bristol Bay region, which have fought the proposal for more than a decade, said Joel Reynolds, western director and senior attorney with the Natural Resources Defense Council.

The mine would have jeopardized the region’s salmon fishery, which brings thousands of jobs to the area and supplies about half the world’s sockeye salmon, Reynolds said.

“It’s a victory for science over politics. For biodiversity over extinction. For democracy over corporate power,” Reynolds said.

The Pebble deposit is near the headwaters of the Bristol Bay watershed, which supports a bounty of salmon “unrivaled anywhere in North America,” the EPA has said.

The agency, citing an analysis by the U.S. Army Corps of Engineers, said discharges of dredged or fill material to build and operate the proposed mine site would result in a loss of nearly 100 miles (160 kilometers) of stream habitat, as well as wetland areas.

The Pebble partnership has maintained the project can coexist with salmon. The partnership’s website says the deposit is at the upper reaches of three “very small tributaries” and expresses confidence any impacts on the fishery “in the unlikely event of an incident” would be “minimal.”

Alaska Gov. Mike Dunleavy, a Republican, said the EPA’s veto constituted a “dangerous precedent” that could have ramifications down the road for development in the state. State Attorney General Treg Taylor also called the decision “legally indefensible” and a subversion of Alaska’s permitting process.

“Alarmingly, it lays the foundation to stop any development project, mining or non-mining, in any area of Alaska with wetlands and fish-bearing streams,” Dunleavy said.

Tuesday’s announcement represents the latest blow to the project. Late in former President Donald Trump’s term in 2020, the Army Corps of Engineers denied a key permit for the project. An appeal filed by the Pebble partnership is pending.

The EPA’s decision said it is prohibiting certain waters from being used as disposal sites for the discharge of material for the construction and operation of the project Pebble proposed. The decision also prohibits future proposals to build or operate a mine to develop the deposit that would result in the same or greater level of impacts and imposes restrictions related to future proposals to develop the deposit.

Sen. Lisa Murkowski, an Alaska Republican, said she opposed the mine, but added the EPA’s veto shouldn’t be allowed to jeopardize future mining operations in the state.

“To be clear: I oppose Pebble. To be equally clear: I support responsible mining in Alaska, which is a national imperative. This determination must not serve as precedent to target any other project in our state and must be the only time EPA ever uses its veto authority under the Clean Water Act in Alaska,” Murkowski said.

Sen. Maria Cantwell, a Washington Democrat, called the EPA’s actions “the final nail in the coffin for the Pebble Mine” and the culmination of a “hard fought battle.”

“Now, we will have a thriving Bristol Bay salmon run for generations to come,” she said.

Tribes in the Bristol Bay region in 2010 petitioned the EPA to pursue protections for the area under the federal Clean Water Act. Alannah Hurley, executive director of United Tribes of Bristol Bay, said that to call the EPA announcement “welcome news is an understatement.”

The EPA during the Obama administration proposed restrictions on large-scale mining in the region that were never finalized. The Pebble partnership said the proposed restrictions were based on hypothetical mine plans and argued the project should be allowed to go through the permitting process.

In 2017, during the Trump administration, the parties reached a settlement giving the Pebble partnership time to file a permit application with the Corps of Engineers, which it did. Eventually the EPA withdrew the proposed restrictions, leading to a court challenge from mine critics.

The EPA during the Biden administration asked a judge to vacate the withdrawal decision and send the matter back to the agency for further consideration. That led to the process culminating in Tuesday’s announcement.

The EPA’s action means the Army Corps of Engineers could not approve the mining project as it was proposed even if it made it through an appeals process, said Radhika Fox, EPA assistant administrator for water.

The project is about 200 miles (320 kilometers) southwest of Anchorage. The nearest villages are within about 20 miles (32 kilometers) of the deposit.

The EPA’s action ignores the rights of Alaska to see development on more than 300 square miles (777 square kilometers) of its land and ignores the interests of the rural villages in the area whose residents could benefit from jobs and economic development, Shively said.

Leila Kimbrell, executive director for the Resource Development Council for Alaska Inc., called the EPA’s decision “a dangerous abuse of power and federal overreach.” The National Mining Association also said in a statement that the EPA’s decision is “is in stark contrast to national and global realities” due to “skyrocketing minerals demands and the fragility of our global supply chains.”