The EPA gave the lowest possible rating to a draft environmental impact statement for the proposed Rosemont copper mine.

It's one of about a dozen times the Environmental Protection Agency's San Francisco regional office has done so since 1989.

"Based on the magnitude of the environmental impacts described … and the significant inadequacies of the document, EPA believes the project should not proceed as proposed," EPA Regional Administrator Jared Blumenfeld wrote Feb. 21 to the U.S. Forest Service in one of two highly critical letters he wrote about the planned mine south of Tucson.

In a second letter, which he wrote on Feb. 13 letter to the Army Corps of Engineers, Blumenfeld cited a half-dozen deficiencies in Rosemont Copper's permit application.

He said the company failed to show its plan is the least environmentally damaging yet still achievable alternative.

It offers "questionable" conclusions that its impacts to downstream river flows won't be significant or violate state standards, he said.

The proposal also would contribute to significant degradation of rare wetlands and could negatively effect recreation, aesthetics and this region's $2.95 million ecotourism economy, Blumenfeld wrote.

"The above considerations, if unresolved, could provide an adequate basis for permit denial under the regulations in any environmental setting" where federally regulated washes are affected, he wrote.

Blumenfeld said if the issues he raised aren't resolved, the EPA may refer the environmental impact statement to the Council on Environmental Quality in the White House. The agency may also request a review of the corps permit issue by EPA and corps officials in Washington, D.C.

Both actions would be very unusual.

The Forest Service and Rosemont Copper are preparing their response to both letters from the EPA.

The Forest Service will address "every issue brought up" in a Feb. 21 letter, along with those in 25,000 other public comments, Coronado National Forest Supervisor Jim Upchurch said last week.

The EPA's comments accompanying the letter said the environmental statements had understated the mine's effects of water quality and may have understated its impacts on air pollution.

"I think it points to the amount of analysis and concern that we have to have as we go forward with this project," Upchurch said. "This wasn't a surprise. It's a controversial project. We need to do the best thing that we can."

Rosemont Copper's Kathy Arnold said the company is developing a conservation, mitigation and monitoring plan in response to the letter to the Army Corps of Engineers. That letter raised concerns about the mine's impacts on neighboring Davidson Canyon and Cienega Creek, which EPA considers nationally significant water courses due to their biological richness in the desert.

The mining company needs an Army Corps permit to discharge fill material into surrounding washes.

The letter is "a step in the agency's normal course," Arnold, Rosemont Copper's vice president for regulatory and environmental affairs, said in a statement. "Although we expected such a letter might be issued, we obviously disagree that an area over 10 miles away could be affected by a modern facility using the latest technologies. In fact, all of the groundwater studies conducted for the draft EIS show no adverse impacts to these areas."

Some problems with the Rosemont mine can be fixed, but more analysis is needed to tell if all problems can be, said Enrique Manzanilla, director of the community and ecosystems division for EPA's for Pacific Southwest region that includes Arizona.

Upchurch said he hasn't decided whether to order a revised or supplemental environmental statement as EPA requested, and has no timetable for finishing the Rosemont review.

"We're not going to sign a decision until I'm comfortable that we met the test and we've done our best job of analysis, and we know that we're not going to not be in compliance with any laws and regulations," he said.

While the Forest Service could ignore EPA's comments, it would do so at its peril, said professor Bob Keiter of the University of Utah College of Law.

"The EPA's comments, coming from an expert agency, would likely be given real credibility by a court, should the matter go to litigation, and could provide a basis for a judicial finding that the service's decision was arbitrary and capricious," Keiter said.