Pima County Raises Water Concerns as Copper World Mine Advances

Pima County is renewing scrutiny of the massive Copper World mining project southeast of Tucson.

A memorandum sent Monday to the Pima County Board of Supervisors details potential water impacts east of the Santa Rita Mountains, including previously observed increases in dissolved metals in Davidson Canyon. It points to unresolved questions about metals detected in nearby water as the proposed mine advances under a substantially different regulatory structure than its predecessor.

But county officials acknowledge that the water-quality findings themselves aren’t new and that no one has established that activity associated with the Copper World project caused them.

“The source of the elevated metals remains unresolved but is concerning,”  Nicole Fyffe, senior advisor in the Pima County Administrator’s Office, told Arizona Globe.

The county plans to continue monitoring the area and will seek a meeting with the Arizona Department of Environmental Quality to discuss the state agency’s role in protecting the streams and how the county’s data should be used, Fyffe said.

The new memo instead highlights how much the mining proposal—and the regulatory framework surrounding it—have changed since Hudbay acquired the Rosemont Mine in 2014.

University of Arizona hydrologist Jennifer McIntosh, whose research on water quality in Davidson Canyon became the subject of a dispute between Pima County and Hudbay last year, told the Globe that her team has collected no new samples since last summer.

“Things have changed with the Copper World project,” McIntosh said.

The original Rosemont proposal focused on the eastern side of the Santa Rita Mountains and contemplated placing mining waste on federal Forest Service land. That brought federal permitting and environmental-review requirements into play.

Copper World is considerably different. The project incorporates the former Rosemont deposit, along with additional deposits discovered by Hudbay. The company has designs to operate on private land and patented mining claims.

Hudbay says that structure allows Phase I to proceed with state and local permits rather than federal permits. A potential Phase II expansion onto federal land would be subject to federal permitting.

The company has already received the major Arizona permits required for Phase I, including an aquifer protection permit from ADEQ in 2024 and an air-quality permit in 2025. Hudbay describes Copper World as fully permitted and says the initial mine would operate for approximately 20 years.

McIntosh said the difference matters when evaluating the county’s concerns. The footprint of the proposed operation has changed, as have some of the environmental reviews and monitoring measures that were contemplated when Rosemont was the project on the table.

Officials are trying to draw attention to those changes while questions surrounding the earlier water samples remain unanswered.

“Pima County has been actively opposing this proposed mine and its predecessor, the Rosemont Mine, for 20 years,” Fyffe said. The Board of Supervisors has adopted four resolutions opposing the project, she said.

Fyffe characterized Monday’s report as one of a series of updates county administrators have given supervisors over the years. With newer supervisors, staff members and residents unfamiliar with the long-running Rosemont and Copper World dispute, she said the county is also using the report to explain the history and what officials consider the project’s anticipated effects.

County staff, she said, have spent two decades reviewing information supplied by the mining companies and state and federal regulators, identifying potential public-health and environmental impacts, advocating for the supervisors’ opposition to the mine, and pushing for stronger monitoring and mitigation if it goes forward.

That history is important because it makes the county an outspoken opponent of Copper World rather than a neutral observer of the project.

At the same time, the earlier water findings remain unresolved through the transformation of Rosemont into the larger Copper World proposal.

McIntosh said some land disturbance and preparatory activity has already occurred around the project. Neither the county nor McIntosh has established whether that activity is responsible for the metals previously detected in Davidson Canyon.

For Pima County, that uncertainty is part of the argument for continued scrutiny rather than evidence that the mine has contaminated the watershed.

Now the county plans to take its concerns to Arizona environmental regulators.