US authorities on Thursday said they intend to re-establish environmental protections to a bay in Alaska that would block a controversial gold and copper mine project.
The Bristol Bay watershed "is an Alaskan treasure that underscores the critical value of clean water in America," said Environmental Protection Agency chief Michael Regan.
"What's at stake is preventing pollution that would disproportionately impact Alaska Natives, and protecting a sustainable future for the most productive salmon fishery in North America," he said.
Bristol Bay is home to a vast wild salmon run. The exceptional quality of the water in the rivers and marshy areas provide ideal habitat for the fish.
The EPA tried to block the mining project in 2014 under president Barack Obama, emphasizing the negative impact the mines would have on local fisheries.
But the Donald Trump administration authorized Pebble Limited Partnership, a subsidiary of the Canadian group Northern Dynasty Minerals, to apply for an operating license by lifting environmental protections.
Last year the US Army Corps of Engineers said the project is "against the public interest" and could not grant a mining permit as currently planned.
Thursday's EPA decision is aimed at ensuring that the project is stalled for the long term, including if a revised application is presented, by using a provision of the Clean Water Act.
The EPA said it has begun the process of cancelling the 2019 notice of withdrawal of the environmental protections that took place under Trump.
Bristol Bay supports commercial, subsistence, and recreational fisheries worth hundreds of millions of dollars, the EPA said, adding that it creates thousands of jobs.
"The salmon populations are critical to the health of the entire ecosystem, which is home to more than 20 fish species, 190 bird species, and more than 40 terrestrial mammal species, including bears, moose, and caribou," the EPA said.