Lake Iliamna, a nursery for wild salmon, would have faced damage from the construction of the Pebble Mine in Alaska. (Bill Roth/Anchorage Daily News/Tribune News Service/Getty Images)

The Trump administration on Wednesday denied a key permit for a massive gold and copper mine in Alaska, striking a devastating blow to a project opposed by an unlikely coalition that includes the president’s son and other prominent Republicans, as well as conservationists, commercial fishermen and Alaska Natives.

In a statement, U.S. Army Corps of Engineers Alaska Commander Col. Damon Delarosa said that a plan to deal with waste from the Pebble Mine “does not comply with Clean Water Act guidelines,” and that “the proposed project is contrary to the public interest.”