The U.S. Bureau of Land Management is intensifying the debate over the proposed Rosemont Mine’s impacts on neighboring streams by bluntly challenging the Forest Service view that the mine probably won’t do major, short-term environmental damage to Cienega Creek.
BLM’s formal comments on the latest draft of the Rosemont environmental impact statement make it one of two federal agencies — along with the Environmental Protection Agency — that disagree with the Forest Service on this question. Pima County, the EPA and the Arizona Department of Environmental Quality are also registering concerns about the service’s view about Rosemont’s impacts on a companion stream in Davidson Canyon.
BLM says it’s concerned that, contrary to Forest Service assurances based on computer models, the mine will or likely could reduce flows to Cienega Creek. It’s one of the prime attractions in the BLM-owned Las Cienegas National Conservation Area, lying southeast of Tucson and across Arizona 83 from the proposed mine site.
David Baker, BLM’s acting Tucson office field manager, said the bureau won’t relinquish its water rights to that stream without a fight, although he stopped short of saying the BLM would sue over this issue.
In a statement, Rosemont Copper said the BLM is overstating the possible impacts of groundwater decline due to the mine.
Coronado National Forest Supervisor Jim Upchurch said last week that his staff has been meeting with officials of these agencies in hopes of reaching consensus on the crucial Davidson-Cienega issue before the service publishes a final environmental impact statement and makes a decision on the mine.
Upchurch has said he hopes to decide by Sept. 27. But as of Friday, he said he doesn’t know if he’ll make it by that day, when Forest Service rules change on objecting to federal decisions in a way that would delay a decision at least three to four months.
The two streams are state-designated Outstanding Waters, meaning they aren’t supposed to be degraded. If the mine was found to be likely to damage either stream, that could place it in violation of environmental laws. Upchurch has said a condition for his approving the mine is that it meet all applicable environmental laws.
“We have to sit down with BLM and talk over their comments,” Upchurch said Friday. “We’ve been having ongoing discussions with EPA and ADEQ to try to figure out how to resolve these issues.
“It’s not something we’re ignoring and saying we’re OK. We try to ensure where people have regulatory responsibility that we’ve identified that, and then respond to the concerns.”
In an Aug. 15 introduction to the BLM comments, the bureau’s Baker wrote that his agency wants the opportunity to provide a more detailed, dissenting opinion for the final environmental report “concerning the nature, scope and intensity” of mine impacts on the conservation area.
“We’re trying to keep our options open until a decision comes out and they finalize all the issues,” Baker said. “If there is a problem with the (Las Cienegas) NCA, if there’s some reason we want to write one, we are going to do it if we can’t reach consensus.”
At stake in this debate is a section of Cienega Creek, a partly perennial, partly intermittent stream that cuts through the conservation area.
The conservation area lies south and upstream of the better known section of creek that occupies the Pima County-owned Cienega Creek Natural Preserve east and southeast of suburban Vail. Both stretches of creek have suffered in recent years from declining stream flows due to drought.
In its draft version of the final Rosemont environmental impact statement, the Forest Service said there’s no indication that Cienega Creek’s streamflow will be reduced in the short term because the groundwater aquifer at the Rosemont site will be lowered and “dewatered” to make way for the copper mine’s open pit.
Stream-flow reductions over 1,000 years are possible, but making specific predictions would be “highly speculative,” the Forest Service said. The service based that conclusion on three computer model studies, including one by a consultant for Rosemont opponent Pima County.
But in its comments, BLM said if the stream-flow and riverfront habitat of a tributary to Cienega — Empire Gulch — is affected by the mine, then so will Cienega Creek. In several parts of that draft, the Forest Service does say Empire Gulch will be impacted by the mine. In other sections, it describes those impacts as “speculative.”
Empire Gulch, which like Cienega has a cottonwood grove, is in parts perennial, intermittent and ephemeral — the latter is a term for streams that run only during and immediately after big storms.
BLM is concerned the computer models used by the Forest Service don’t account for extensive rock fracturing that occurs underneath the conservation area — fractures that could move groundwater from south to north and potentially affect stream flow, BLM biologist Jeff Simms said.
“The modelers simply ignored fractures,” Simms said. “That’s one of the shortcomings of computer models.”
In its comments, the bureau also said repeatedly that “BLM does not relinquish existing surface and groundwater rights,” in reference to federal water rights it says it owns in the Las Cienegas area.
“We have to have the water to fulfill our mission of protecting the national conservation area,” Baker said.
Conservative computer models have predicted the decline will be less than 1 foot in the Cienega Creek area, even 1,000 years after the mine is closed, Rosemont Mine officials said.
As for Empire Gulch, the same models predict a 3- to 6-foot potential groundwater level decline over 1,000 years, but less than 2½ feet over a “more realistic time frame of 150 years,” said Jamie Sturgess, Rosemont Copper’s senior vice president for corporate development and government affairs.
Sturgess said adding the models can be speculative because of many variables.
The mine’s statement said the company has committed 150 acre-feet of surface water rights annually to the Upper Cienega Creek Basin for agencies’ use in managing waters.
The bureau is currently suing the Arizona Department of Water Resources to prevent a big Sierra Vista development and its groundwater pumping from damaging the San Pedro River in Cochise County, to which the bureau owns federal water rights.
Baker said he doesn’t know if BLM would sue over Rosemont, adding, “We’d leave that up to our solicitors. I don’t play in that arena.
“These are all politically charged issues.”
But in Las Cienegas, the bureau’s water rights are implied under federal law, whereas on the San Pedro they are explicitly spelled out in the law that created that river’s national conservation area.