WASHINGTON — The Environmental Protection Agency on Friday announced severe restrictions on the proposed Pebble Mine in Alaska, a move that is likely to block a project the EPA said could devastate the best run of wild salmon left on the planet.

“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, Northwest regional administrator for the EPA.

The proposed mine has become one of the country’s biggest environmental controversies, with fishermen in Washington state and Alaska saying it could ruin their livelihoods.

The EPA said that, based on information the mine developer submitted to investors and the U.S. Securities and Exchange Commission, the pit of the proposed copper and gold mine could be nearly as deep as the Grand Canyon and produce waste that could fill a major football stadium 3,900 times.

The mining operation could cover an area bigger than Manhattan, the agency said.

The agency said its studies indicated the mine could wipe out nearly 100 miles of streams and 4,800 acres of wetlands even without a major accident.

The EPA said it will seek public comments until Sept. 19.

The new restrictions would prevent the developer from building the size of mine it envisioned and are liable to mean the death of the controversial project.