U.S. Sen. Maria Cantwell is asking President Barack Obama to take action to restrict or prohibit the development of large-scale mining in the Bristol Bay watershed.
In a letter sent Thursday, Cantwell asked Obama to invoke a rarely used authority under the federal Clean Water Act to protect the region that is home to the world's largest sockeye salmon fishery.
The Democratic senator says thousands of jobs in Washington state are tied to Bristol Bay salmon fishing.
She, fishermen and others are rallying against the proposed Pebble Mine Thursday in Seattle.
The U.S. Environmental Protection Agency released a report last week concluding that large-scale mining in the Bristol Bay watershed poses significant risks salmon.
Pebble Limited Partnership spokesman Mike Heatwole says Cantwell's request is unprecedented and has never been used before a resource project has filed for permits. He says "it flies in the face of due process."
He also criticized the EPA document as a political report intended to harm the project's ability to apply for permits.