U.S. Rep. Ron Barber's recent call for a new environmental impact statement on the proposed Rosemont Copper mine has angered the mine's backers.

The Tucson Metropolitan Chamber of Commerce held a news conference Thursday afternoon to slam Barber for unnecessarily trying to delay the ongoing review of permits for the mine. The mine is proposed for an area southeast of Tucson in the Santa Rita Mountains outside Sonoita.

"Put your trust in the designated regulatory agencies and let them do their work," Mike Varney, chamber president and CEO, said in a message to Barber. "Congressman Barber's recent actions can only serve to delay or kill jobs in our community, and those are jobs we need very badly."

In an Oct. 17 letter to the secretary of agriculture, Barber asks for the new environmental impact statement because of "significant" changes in Rosemont Copper's operation plan. He points out concerns about increases in heavy truck traffic, more uncertainties about long-term water usage and the likelihood of leaching of stockpiled oxide ore. He asks for a 90-day period for public review.

Barber said he's acutely aware of the need for more jobs in Southern Arizona, but he must protect the long-term interests of residents in his district. He said he was satisfied with the environmental review until the company changed the mine plan. His staff spent time studying the plan and came to the conclusion the changes were significant enough to call for a new environmental review.

"When you are dealing with an issue as complex as this that could have a negative impact on businesses in Green Valley, Sahuarita, Sonoita and Patagonia, it's not unreasonable to ask that the people who are going to be affected by this have their say," Barber said.

Barber, a Democrat, is not the only one calling for a new environmental impact statement. Pima County Administrator Chuck Huckelberry sent a six-page letter Thursday to the U.S. Forest Service with a similar request. Ray Carroll, a Republican member of the Pima County Board of Supervisors, agrees a new environmental impact statement is needed.

Varney insisted Thursday's news conference - which came less than two weeks before the Nov. 6 election - was not political. He said the chamber is not endorsing Barber's opponent in Congressional District 2, Republican Martha McSally, either. He said he and others simply couldn't go without publicly challenging "misinformed statements" made by Barber in the letter sent last week. They met with Barber on Wednesday but came away unhappy with what they heard.

The changes in the plan came after careful consideration and will make the mine more efficient, said Bill Assenmacher, president of the Southern Arizona Business Coalition. There will be less truck traffic per day, the same water and electricity usage as in the old plan and "overall environmental improvements," Varney said.

Even though mining will be extended from 18 to 21 years in the new plan, only 4 percent to 5 percent more material will be extracted because the new plan calls for focusing only on sulfide ore and scrapping plans for oxide ore. He said Barber has been fed misinformation that has clouded his opinion.

"The plan is more focused," Assenmacher said. "You are going to have a more efficient mine." He said the public review process, which has included 20-plus public hearings, has gone on long enough.

"Delays send a message to other businesses that it is indeed difficult to do business in Southern Arizona," Varney said.

Though they are clearly not in Barber's corner, mine proponents aren't backing McSally either in the CD2 race.

She received one $500 contribution in March from James Sturgess, senior vice president of corporate development for Rosemont Copper, but she returned that contribution three weeks later, FEC records show.

Rosemont Copper executives have given thousands to candidates who supported the mine, including $6,650 to Republican Jesse Kelly, who lost to Barber in the June 12 special election; $4,750 to Republican Dave Sitton, who finished fourth in the CD8 special election GOP primary; and $7,750 to Republican Gabriela Saucedo Mercer, a CD3 candidate.

McSally, a retired Air Force colonel, says she's pro-mining in general and had hoped to be able to give the mine her full backing. But after meeting with both sides, she came to the conclusion the concerns about water levels, water quality and impacts on eco-tourism are legitimate. She owns land near Elgin, which is in the same general area as the mine.

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"I am going to be focusing on not picking winners and losers, but on providing that oversight to the federal agencies during the permitting process to make sure that they are fair and that they are timely," McSally said last month.

Barber, who was elected to finish former Rep. Gabrielle Giffords' term in the old Congressional District 8, has said he is not against mining but that the Rosemont mine is in the wrong place and done the wrong way. His principal concern is that the mine will further deplete the aquifer in the area.

"Yes, it will bring jobs," Barber said. "But how many jobs will be lost as a result?"

Assenmacher called concerns about water a "distortion of facts." He said Rosemont Copper has offered to extend the Central Arizona Project into Green Valley, put in a recharge station and vowed to put back as much water as it takes out.

But Barber said getting water from the CAP to replenish the aquifer is an idea but not a certainty.

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Reporter Carli Brosseau contributed to this story. Contact reporter Brady McCombs at 573-4213 or bmccombs@azstarnet.com. On Twitter @BradyMcCombs