Bristol Bay is home to the world's largest sockeye salmon run.
The Environmental Protection Agency made clear Friday it doesn't plan to allow a huge copper and gold mining project in southwest Alaska's Bristol Bay watershed.
The agency, in a proposed Clean Water Act finding, said large-scale mining of what's known as the Pebble deposit could "result in significant and unacceptable adverse effects on ecologically important streams, wetlands, lakes, and ponds, and the fishery areas they support." Bristol Bay is home to the world's largest sockeye salmon run.
"The science is clear that mining the Pebble deposit would cause irreversible damage to one of the world's last intact salmon ecosystems," said Dennis McLerran, who heads EPA's Alaskan and Pacific Northwest operations, in a statement.
EPA's action is sure to inflame GOP allegations of overreach. EPA critics say the agency should not "preemptively" thwart Northern Dynasty Minerals' project. The developers of the open-pit mine have not yet submitted a formal plan and application.
But EPA's draft finding Friday said there would be substantial harm even from a mine that's much smaller than what developers, in filings with securities regulators, have signaled they're hoping to build.
"Based on mine proponents' prospectus, EPA estimates the mine would require excavation of the largest open pit ever constructed in North America and would cover nearly seven square miles at a maximum depth of over 3/4 of a mile," EPA said in a summary of its findings, noting for comparison that the Grand Canyon's maximum depth is one mile. Mine waste would "fill a major football stadium up to 3,900 times," EPA said.
EPA is proposing restrictions on mining development that would prevent the loss of more than five miles of streams that salmon use or loss of 1,100 or more acres of wetlands, lakes, and ponds connected with those streams or their tributaries, among other limits.
The Pebble Partnership, the group that's seeking to develop the mine, in May sued EPA over what it contends have been illegal steps to preemptively block the project. Pebble Partnership CEO Tom Collier, in a statement, said he was "outraged" that EPA took new action Friday "when litigation on their underlying authority to do so is pending in federal court in Alaska."
"We will continue to fight this unprecedented action by the agency, and are confident we will prevail," he said.
Environmentalists cheered EPA's action. "For 10 years, the proposed Pebble Mine has cast a cloud of uncertainty on Bristol Bay. Today's announcement provides hope that we are nearing the finish line to protecting the world's most prolific salmon fishery," said Chris Wood, president and CEO of Trout Unlimited, in a statement.