The Rosemont Mine could worsen air quality in Saguaro National Park, disturb cultural resources — including human burial sites — and reduce water flows into Davidson Canyon and Cienega Creek, said the U.S. Forest Service.

The “No Action” alternative is the environmentally best alternative among six proposals for the mine site currently before the Forest Service, the agency said Friday.

But the service “cannot materially interfere with reasonably necessary activities” under the 1872 Mining Law and other laws and regulations that opened up the West to mining as long as the mine is legal, the service said.

Of five mining proposals available for Rosemont, the “Barrel Alternative” that it has chosen not only meets all the laws, but is the best one environmentally, the Forest Service said.

Those and many more thoughts went into the service’s new draft decision that, if ratified, would approve the mine on more than 5,000 acres in the Santa Rita Mountains, southeast of Tucson.

Released Friday, the decision from Coronado National Forest Supervisor Jim Upchurchsets the stage for what’s likely to be a highly contentious four months, starting Jan. 1.

That’s when opponents and critics of the mine can start filing formal objections. By early May, Upchurch must make a final decision.

Upchurch wrote his decision is based on a thorough review of the final Rosemont environmental impact statement and consultation with the public, government agencies, interested tribes and the public record. He said he considered “relevant scientific information, public concerns and opposing viewpoints.”

Friday, three federal agencies that have raised concerns about the mine — the National Park Service, the Bureau of Land Management and the Environmental Protection Agency — weren’t ready to say if they would formally object. A Tucson environmentalist,Randy Serraglioof the Center for Biological Diversity, said environmentalists will definitely file objections.

The EPA declined a request from the Star for an interview on the decision. The BLM didn’t return a phone call from the newspaper. A Saguaro National Park official said the agency hopes to resolve its differences with the Forest Service through discussions, although the park service isn’t ruling out filing an objection.

Pima County Administrator Chuck Huckelberry, an early opponent, said, “We will obviously comment on the draft record of decision. If we file anything that’s going to be meaningful, it would take the form of a formal objection.”

While the Forest Service agreed with other agencies that major impacts will occur, it didn’t give ground on every detail of the agencies’ issues with the project. In a statement, the opposition group Save the Scenic Santa Ritas said the mine proposal has numerous problems caught by the agencies that the environmental report — and this decision — failed to address.

But Upchurch wrote of trying to resolve scientific uncertainties and disagreements, “I have also sought out and considered the professional opinion of resource specialists from federal agencies, private industry and third-party consultants. I have met on numerous occasions with interested members of the public to listen to their concerns and issues.” 

In his 96-page decision, Upchurch also laid out a list reasons showing the Barrel Alternative was the best of the five proposals presented. Among his reasons:

• Barrel was the only one of the options the Forest Service concluded will meet federal air-quality standards at the site’s fence line. While it would be possible to move the fence line for the other four options farther from mine activities to meet the air rules, Upchurch wrote that he did not regard that as an acceptable option because that would close off more forest lands to the public.

• The Barrel Alternative would reduce surface-water flows into neighboring Barrel and Davidson canyons by the smallest amount. Barrel would cut flows by 17 percent, compared to 23 to 46 percent for the other proposals, although those levels are still unacceptable to opponents.

• Upchurch wrote that all five mine alternatives would meet state groundwater and surface-water quality standards, including seepage of pollutants from mine tailings into groundwater. However, he did not mention concerns raised by the state Game and Fish Department that dissolved solids and sulfates — which don’t have legal standards, but can affect taste and health — could seep into groundwater.

• The Barrel Alternative would cause the second-lowest reductions of sediment delivered by stormwater into Barrel Canyon. Sediment is important to prevent scouring of the canyon’s stream channel.

• The Barrel choice would reduce groundwater flows into Cienega Creek by the lowest percentage: 4.4 percent compared to 11.7 percent for Rosemont Copper’s mine proposal.

• Barrel would harm the second-smallest number of acres of streams and creeks that are protected by the Federal Clean Water Act — about 68 acres. The EPA, however, has projected impacts of more than 100 acres.

• Barrel would have slightly less sky brightness than the other alternatives, a benefit for the neighboring Whipple Observatory.

• Barrel is the only alternative without the mine’s proposed heap leaching, so its selection avoids risk of groundwater contamination from leaching chemicals.

• While the five mine alternatives would potentially hurt or dry up about 78 springs and seeps in the mine area, Barrel tied with another alternative for the smallest number of springs — 16 — that are likely to be harmed.

So far, the only federal agency to comment on the mine’s impacts since release of the final environmental report is the National Park Service.

The biggest concerns are an increase in deposits of nitrogen onto the park’s ground due to nitrogen oxide emissions from mine haul trucks, and the degrading of visibility at both park units due to emissions. The nitrogen deposits could help the spread of invasive plants in the park, particularly buffelgrass.

Upchurch, while acknowledging these problems could occur, wrote they wouldn’t violate the Federal Clean Air Act. The Park Service wants more mitigation measures, but the Forest Service hasn’t agreed to them, saidScott Stoneham, Saguaro’s chief of science and resource management.

Now, the Park Service is seeking negotiations with the Forest Service to resolve these concerns, possibly with the federal Council on Environmental Quality facilitating the discussions, Stoneham said.

“We’re held responsible for insuring conservation and protection of resources of Saguaro National Park, and that’s what we’re committed to,” he said.

Contact reporter Tony Davis at tdavis@azstarnet.com or 806-7746. Follow him on Twitter at tonydavis987.