E.P.A. Bans Disposal of Mine Waste in Bristol Bay

First proposed nearly two decades ago, the Pebble mine project has had a roller-coaster existence, its prospects lurching from bright to bleak over the years.

In the late 2000s it gained support from Alaska’s governor at the time, Sarah Palin, a pro-development Republican. But the E.P.A. in the Obama administration moved to block the mine in 2014, citing the Clean Water Act and the risks to the salmon fishery.

The agency under President Trump then reversed the Obama-era ruling, giving the project new life. Late in the Trump administration, however, after opposition from some Republicans, including the president’s son Donald Trump Jr., an avid sport fisherman, the United States Army Corps of Engineers denied the project a critical permit.

The Pebble partnership has appealed the corps’ decision. Radhika Fox, the assistant E.P.A. administrator for water, said that if the company were to succeed in the appeal, the Corps still could not approve the project, given the E.P.A. determination, unless it were somehow changed and the new proposal “does not have the similar adverse effects of this proposal.”

Senator Maria Cantwell, Democrat of Washington, one of the first lawmakers to oppose the project, said she was “ecstatic” about the E.P.A. action. Washington State residents hold about a quarter of the commercial permits to fish for Bristol Bay sockeye, and much of the harvest passes through the state’s ports.

“This is such a big economic consequence to salmon and to the Northwest economy and lifestyle,” she said. “This isn’t just like an Alaska issue.”

The Pebble project proposal calls for an open-pit mine on a square mile of land, eventually dug to a depth of about 1,500 feet. Tens of millions of tons of rock ore would be removed annually and processed to extract gold and copper as well as molybdenum, which is used to strengthen steel in alloys.