Other articles by Tony Davis:

AZ Senate fails to act on gas-storage cavernVote pending on exemptions for underground gas storage Killing lions to save sheep faulted Natural gas threatens water, critics sayAZ wanted a jaguar collared despite 2 deaths in Sonora Ex-Gov. Castro, 93, reflects on AZ issues Audubon: Climate change is shifting bird migration Lawmakers decry US stance that it can't block Rosemont mine Bear, lion track count ends after 20-year run$900M financing sought for mine

Trades/Construction
RANCHO RESORT
MAINTANANCE POSITION Finance and Accounting
Charles E. Gillman Company
Accounting Specialist Administrative & Professional
Tucson Urban League
CEO/President Administrative & Professional
Jorgensen Brooks Group
Counselor Mechanical
Komatsu Equipment Co
Resident Field Mechanic Sales and Marketing
Everready Glass
Sales Reps

As the state investigates the cause of a recent 168,000-gallon acid spill at a Morenci copper mine, opponents of the proposed Rosemont copper mine are questioning whether such a spill could happen here.

State investigators have not yet determined whether human error or design flaws led to the release of the sulfuric acid solution into Eastern Arizona's Chase Creek in late October, according to a state inspection report.

The spill poured down the creek for almost two miles before earthen dams built by workers of mining giant Freeport McMoRan Copper & Gold Inc. stopped the liquids 40 feet from where the creek drains into the much larger San Francisco River.

A Freeport spokesman, Richard Peterson, said the cause was human error, but he declined to offer more details.

At Rosemont, the principal issues regarding potential spills center on whether the plans laid out in writing by Augusta Resource Co. for operating the mine in the Santa Rita Mountains south of Tucson are adequate.

Opponents are focusing on two areas. One is the mine's planned use of dry tailings to limit water consumption. The other is its stormwater-control measures. Those measures meet government standards, but opponents contend they are not strong enough to survive in an era of long-term climate change that many scientists say will lead to more extreme storms.

Augusta officials say they've taken plenty of steps to protect against spills and that they don't want to speculate on what might happen if the climate changes.

The company has proposed to mine 27 million tons a year of copper, molybdenum and silver on 4,400 acres of private and public land. The U.S. Forest Service is in the middle of conducting studies for an environmental analysis of the mine's effects, and it plans to release its report in about a year.

The company says it has planned extensive measures to prevent spills of any contaminated or potentially contaminated liquids used in mining at Rosemont. The mine, liquid storage ponds and buildings will all be put behind large, earthen structures to separate them from washes leaving the mine site.

Augusta is designing such barriers, including stormwater ponds and check dams it will build to withstand a 100-year flood, in accordance with state and federal standards, a company spokeswoman said. A 100-year flood is one large enough that it would statistically be expected to hit about once in a century. There's a 1 percent chance that a flood that big would happen in any given year.

The company is also keeping all of its mine facilities within one drainage, Barrel Canyon, whereas past mine plans for the site put tailings and other waste-rock storage areas in three canyons, Rosemont's mining plan said.

Stormwater runoff will be diverted away from the tailings piles, the plan said.

"Our philosophy is, 'Let's design it from the beginning to prevent these things from happening,' " said Augusta spokeswoman Jan Howard. "As for the Morenci mine, it is hard to speculate as to how it is different from ours.

"We're not familiar with what happened there. There's no way we can be appropriately compared to them."

Opponents, however, say they're worried that a spill from the Rosemont mine could reach Davidson Canyon, a highly prized riverfront riparian area that lies 2.7 miles downstream from the mine site. After Barrel Canyon passes through the Rosemont site, it feeds Davidson Canyon, which in turn is a tributary to Cienega Creek. Both Cienega Creek and Davidson Canyon contain Pima County-owned open space.

The Morenci-area spill happened in a populated area, where plenty of people saw it and had time to stop the acid liquid before it could reach the San Francisco River, said Elizabeth Webb, a community activist who lives about three miles east of Davidson Canyon and about seven miles from the Rosemont mine as the crow flies.

If a similar spill happened at Rosemont, "we would be the first ones to notice it," Webb said. "I cross Davidson Canyon every day to go home from work. How would we get home if we had to cross this mess?"

Webb and another activist drove to the site of the Freeport spill and videotaped the cleanup work, three days after the spill occurred. "We walked over the creek on a bridge, and our eyes were burning," Webb recalled.

All liquids were removed from Chase Creek by Nov. 4, the state inspection report said. Besides removing all the liquids, Freeport crews also hauled out tens of thousands of tons of soil from the creek for testing to see how contaminated it is. At one point, the company had 200 people and 60 pieces of equipment at the cleanup site, the state report said.

The dry tailings plan has been a hallmark of Rosemont's proposal from the start, not because of contamination issues, but as a water-saving tool. With dry stacking of tailings, in which a company mechanically removes water from the waste materials, that creates tailings with a very low moisture content.

The water can be reused many times, which the company has said would reduce its expected water use in half.

But Webb and other Rosemont opponents have said that the dry stacking method was designed primarily for very arid climates, such as the Chilean desert where about 2 inches of rain fall each year compared to 18 to 24 inches annually in the Santa Ritas. The opponents are concerned that the additional rain could make the tailings wetter and more prone to collapses and overflows that could lead to spills.

"What it boils down to is that the dry tailings design and everything that goes along with it is untested in our climate. It's not worth the risk," Webb said.

In a newly released report, however, a consulting firm hired by Rosemont mentioned two mine sites in Mexico that use dry stacked tailings in areas that get about 30 inches of annual rainfall. One is an open-pit silver-gold mine near the town of Alamos, Sonora. The other is a gold mine in southwestern Chihuahua.

The consultant's report listed 40 existing mines including these two that use the dry tailings technology, and nine others not including Rosemont that are studying the feasibility of using it for future operations.

While dry tailings aren't a panacea for the industry, their use is growing and they have potential environmental advantages over conventional tailings "largely because physical failures of tailings cannot occur," the report said.

Most of the dry stack operations studied by the consultant are far smaller operations than Rosemont's, which would mine nearly 75,000 tons of copper daily. The two Mexican mines studied, for instance, get between 3,500 and 5,300 tons daily.

Mine opponents also point to the summer 2006 storm that washed out the paved road in Sabino Canyon as an example of the kinds of storms that the Rosemont mine would not be protected against. During five days, the Catalina and Rincon mountains got a total of 5 to 11 inches of rain and Tucson got 1 to 6 inches in various areas.

The overall storm was a 1,000-year event, said a new report from the Pima County Regional Flood Control District. The peak flows on the Rillito and Tanque Verde creeks were 500-year floods and the peak on Sabino Creek was a 200-year flood, the report said.

While most climate scientists have cautioned that no single storm can be linked to climate change, they've said climate change is likely to bring more extreme storms in the future.

"They can't be designing to 100-year standards for Rosemont in such a sensitive area," said Lainie Levick, a board member for Friends of the Scenic Santa Ritas, which opposes Rosemont. Levick, who was stranded in her far Northeast Side neighborhood for a day during the 2006 flooding, said she's concerned that a larger-than-100-year flood at Rosemont could cause its tailings dam to fail. Levick is a senior research specialist in watershed management at the University of Arizona.

Augusta's Howard replied: "We're trying to build to as high a standard as is appropriate at this time. We don't want to speculate from a climate change standpoint about what the standard might be. That's something that the federal government is looking at.

"It seems to be a valid goal to build towards the 100-year storm."