The proposed Rosemont Mine would “cause or contribute to” violations of Arizona water quality standards and trigger “significant degradation” of federally regulated washes, said a lower-level Army Corps of Engineers office in recommending against granting it a key federal permit.

In a recent letter to the mine company’s general manager, a top Corps official for the first time revealed these and other reasons underlying that office’s recommendation last year to deny a federal Clean Water Act permit for the $1.5 billion, Tucson-area project.

The letter said the Corps’ Los Angeles District concluded:

  • Rosemont Copper’s plan to buy, preserve and environmentally restore more than 4,800 acres to offset its impacts is inadequate.
  • Completion of what would be the U.S.’ third-largest copper mine would negatively affect surface water quality, sediment distribution and use of the area by humans and wildlife, including federally protected species.
  • Granting the permit would be against the general public interest. To approve a permit, the Corps must find that it would be in the public interest.

The Dec. 28 letter went to Hudbay Minerals Inc. Arizona General Manager Patrick Merrin from Col. Pete Helmlinger, commander of the Corps’ San Francisco-based South Pacific Division.

Helmlinger, who oversees the Corps’ L.A. office, will make the agency’s decision on the mine, which Hudbay can appeal to Corps’ higher-ups if it’s negative.

The Star obtained that and other recent letters between the Corps and Hudbay through the U.S. Freedom of Information Act.

Hudbay’s Arizona subsidiary Rosemont Copper responded to the Corps letter only with a statement saying, “Rosemont continues to work on the permitting process with a goal of satisfying the requirements of the agencies. We have always said we support the permitting process and the time required by the agencies to complete it successfully.”


The Corps has been tight-lipped about Rosemont since September 2014, when it received the company’s final mitigation plan for preserving and enhancing the 4,800 acres.

Helmlinger’s letter responded to requests from Hudbay for more transparency about the agency’s deliberations.

The Corps’ has declined to release a copy of the L.A. office’s July 2016 recommendation against the mine permit, a document the Star has requested under the Freedom of Information Act.

But it recently released a July 25, 2016 memo to Helmlinger from Corps official Kirk Gibbs, head of the Los Angeles office, saying that “to assure your review process is impartial and independent, I will not share my reasoning” or the recommendation itself with Hudbay, the Environmental Protection Agency or the U.S. Forest Service, which must make a separate decision on the mine.

In a Sept. 7 letter to Helmlinger, Hudbay’s Merrin noted the company has consistently said permitting agencies should get the time they need to finish their work using the best information.

“All we have asked is for the process to be applied fairly and transparently,” Merrin wrote. “If an agency has had questions or concerns, or needed additional information, we have always done our best to respond quickly.

“To our regret, we found the L.A. District of the Corps essentially unwilling to communicate with us,” since September 2014, Merrin wrote.

He sought from Helmlinger “a direct and clear understanding of the reason the district engineer recommended a denial of our permit. As of this moment, we have received virtually no explanation of this action or opportunity to respond to the district’s underlying concerns.”

In November, Merrin wrote Helmlinger a second time, saying he had personally made eight written and numerous oral requests to the Corps seeking to understand its concerns and indicating a desire to remedy them.

“These requests have been ignored,” he wrote.

Based on records Hudbay has received through Freedom of Information Act requests, “we are concerned that the district’s recommendation was not based upon a comprehensive record, did not properly assess the project’s impacts and mitigation and may have considered perceived issues that were beyond the scope of the Corps’ mandate,” he wrote.

The Corps’ permit decision has been the biggest unknown in the longstanding Rosemont dispute. The Forest Service has said it has no legal right to deny the mine if it meets all federal rules.

The Corps and Forest Service decisions are the last major approvals the mine needs after having received three approvals from the Arizona Department of Environmental Quality and a favorable biological opinion from the U.S. Fish and Wildlife Service, among other approvals.


At issue is the mining company’s proposal to dredge and fill various washes near the mine site, in the Santa Rita Mountains southeast of Tucson, with mine tailings and waste rock. These activities are expected to cause direct and indirect impacts to 68 acres of washes, the Corps has said.

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Federal officials have long said the areas that could be affected are nationally significant for their aquatic habitat and provide a significant source of drinking water for the Tucson area. Nearly two years ago, EPA official Jared Blumenfeld wrote that the Upper Santa Cruz River groundwater sub-basin, where Rosemont would be located, provides 20 percent of the total groundwater recharge for the state’s water management area covering Tucson and its suburbs.

In his Sept. 7 letter, Hudbay’s Merrin said the project wouldn’t materially affect special aquatic sites or other types of unique aquatic resources and that the washes flow only during storms. The larger washes serve as numbered and maintained Forest Service roads, Merrin wrote.

He added that the company's total mitigation cost is $700,000 per acre for the 68 acres that would be impacted. That comes to about $48 million total. That plan “as far as we know, exceeds anything the Corps’ Arizona office has previously required,” Merrin wrote.

Overall, nine years of review and analysis of this project has “helped us design a mine that minimizes associated impacts and meets or exceeds the regulatory standards for air, water and biological impacts,” Merrin wrote Helmlinger on Nov. 17.

He noted that the state has issued 14 permits for the project and that former Gov. Jan Brewer and current Gov. Doug Ducey have written the Corps in support of the project — two letters last year, in Ducey’s case.

But in his Dec. 28 letter, Helmlinger wrote that the mine would cause substantial reductions of functions and services in the washes, and contribute to degradation of state-protected “Outstanding Waters.” The state Department of Environmental Quality has classified stretches of neighboring Davidson Canyon and Cienega Creek as Outstanding Waters, which under state rules aren’t supposed to be degraded.

While Hudbay’s 4,800 acres would mitigate the mine’s indirect impacts, permanent, direct impacts and loss of 40.4 acres of washes won’t be mitigated, Helmlinger wrote. They include an effort to re-establish washes at Sonoita Creek Ranch in Santa Cruz County and mitigation land buys in Davidson Canyon and of other lands outside the watershed where Rosemont would be built, Helmlinger wrote.

Among key concerns regarding public interest are the mine’s adverse effects on cultural resources and traditional cultural properties important to tribes, he wrote. The Tohono O’Odham tribe and others have warned that the mine would seriously damage artifacts and other cultural resources in the Santa Ritas, although the mining company has promised extensive mitigation .

The Corps’ L.A. office staff met with Rosemont officials about once a week for a year and frequently throughout its review of the permit, which dates back to 2011, he wrote.

Responding to Hudbay’s request for a chance to respond to the L.A. office’s concerns, Helmlinger wrote, “If at any point you intend to modify, supplement or withdraw the proposal, please let me know promptly. Supplementation or any other changes should be in writing.”

If the proposal does change, it may be sent back to the L.A. office’s district engineer for evaluation and, potentially, for more analysis which could include consulting with other agencies and getting more public comment, Helmlinger wrote.

The Corps and Hudbay are supposed to meet this month to discuss permit matters.

Contact reporter Tony Davis at or 806-7746. On Twitter@tonydavis987