Less than a week after the U.S. Department of Interior issued a 20-year mining moratorium on 225,000 acres of federal land in Minnesota near the Boundary Waters that would effectively remove minerals from production that Twin Metals planned to mine, the U.S. Environmental Protection Agency (EPA) took steps to block a the Pebble Mine in Alaska.

The Associated Press reported that the EPA issued a final determination under the Clean Water Act that bans the disposal of mine waste in part of the bay’s watershed, about 200 miles southwest of Anchorage. Streams in the watershed are crucial breeding grounds for salmon, but the area also contains deposits of precious-metal ores thought to be worth several hundred billion dollars.

“This preemptive action against Pebble is not supported legally, technically, or environmentally,” said John Shively, chief executive of Pebble LP, a unit of Northern Dynasty Minerals Ltd.

He also said US President Joe Biden’s strategy to secure minerals for green energy goals seems to be giving “passing support” to minerals such as lithium in the United States and seeking an “enormous supply of copper … from other nations.”

The Pebble Limited Partnership is owned Canada-based Northern Dynasty Minerals Ltd.

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

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 their potential impact on 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 EPA, citing an analysis by the 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 about 100 miles (160 kilometers) of stream habitat, as well as wetlands.

The Pebble partnership has maintained that 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.”

Republican Alaska Gov. Mike Dunleavy said the EPA’s veto was a dangerous precedent that could affect future development in the state, while state Attorney General Treg Taylor called the agency’s action “legally indefensible.”

“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.

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

“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 in a statement.