And that doesn’t include the support facilities, a transportation corridor, powerhouse, wastewater treatment plants, offices and housing, and other infrastructure, it says.

Even the smallest mine’s impacts would be significant, it says.

The Bristol Bay area, home of the world’s largest sockeye salmon run, produces about half the world's sockeye salmon. Its salmon fishery has about $300 million in sales and provides more than 11,000 full- and part-time jobs.

The mine owners promise more than 4,700 construction jobs and 2,800 permanent jobs in Alaska for the first 25 years, and annual economic contributions of $400 million during construction and $1.2 billion to $1.4 billion over the 25 years.

The mine has drawn fire from fishing interests, Alaska Native tribes, conservation and clean water organizations, but Alaska’s senators are split. Sen. Lisa Murkowski (R) is a proponent of the mine who criticizes the EPA restrictions but says the state can oversee the project. Sen. Mark Begich (D) opposes the mine, calling it “the wrong mine in the wrong place.” Neither office responded to requests for more information.

“The Pebble Mine would be another disaster in the making,” says Lori Pottinger, spokeswoman for International Rivers, a water protection organization in Berkeley, Calif.

Pebble also would have multiple tailings dams, depending on the ultimate size of the mine.

“Tailings dams have a terrible record—they are more apt to fail than any other kind of dam worldwide,” Pottinger says.

Joel Reynolds, western director and senior attorney with the Natural Resources Defense Council, calls the Mount Polley breach “the toxic time bomb explosion that all of us who’ve fought the Pebble Mine have predicted would happen.”

And the Pebble Mine would be 10 times bigger with proportionately larger tailings impoundments, he writes in a blog.