The U.S. Environmental Protection Agency has issued a scorching pair of letters blasting the proposed Rosemont mine.

The agency's San Francisco regional office wrote a letter that fiercely attacks the Forest Service's draft environmental impact statement for the mine. EPA officials said later it's one of the worst such statements they've seen, saying it underestimates the project's environmental effects.

The agency wrote a separate letter to the Army Corps of Engineers over a proposed permit that would let Rosemont discharge fill material into neighboring washes.

It warned that the mine could do legally unacceptable damage to to water supplies and water quality in sensitive riparian areas in nearby Davidson Canyon and Cienega Creek.

Both letters urge that the mine project not proceed without extensive additional analyses. The EPA also urged the Forest Service to publish a revised or supplemental draft environmental impact statement rather than moving ahead to publish a final statement as it had planned.

EPA, a Cabinet-level agency, can veto a Clean Water Act permit even if the corps approves it. It can't order the Forest Service, part of the Agriculture Department, to issue a new environmental report. But three law professors said last week that the EPA's letter could be ammunition for a future lawsuit against the Forest Service by a group opposed to the mine.

Rosemont Copper officials took the EPA's comments in stride.

"This is a standard part of what a regional EPA office does," CEO Rod Pace said in a news release. "It's part of a rigorous review process."

INSIDE: What the Forest Service's environmental impact study says, and why the EPA thinks it's full of holes. Page C9