A federal judge in Arizona is weighing whether the U.S. Forest Service can regulate groundwater pumping from private wells when the result harms nearby public lands. The dispute centers on the Pinto Valley Mine, which has reduced the flow of Pinto Creek by over 90% in the last decade while extracting 5 trillion gallons of water annually for copper production. The mine, located east of Miami, Arizona within the Tonto National Forest, relies on private wells outside Forest Service jurisdiction, leaving the agency arguing it lacks authority to limit pumping.
The Sierra Club filed a lawsuit in 2024, alleging the Forest Service violated the National Environmental Policy Act and the Endangered Species Act by approving the mine’s 2021 expansion without addressing groundwater depletion. The group claims the agency ignored evidence of harm to two endangered bird species—the yellow-billed cuckoo and the southwestern willow flycatcher—whose habitats depend on the creek’s flow.
In court arguments last week, Thomas Delehanty, an attorney for Earthjustice representing the Sierra Club, argued the Forest Service can impose restrictions if private well operations materially affect public land. He pointed to agency regulations requiring protection of natural resources and federal law mandating mine operators mitigate harm to fisheries and habitats. The 2021 environmental impact statement for the mine’s expansion acknowledged that the private wells were part of the mining operation, not independent activity, Delehanty said.
Forest Service vs. State Water Rights
The Department of Justice, defending the Forest Service, conceded that mining operations degrade surrounding land but argued the agency cannot interfere with state-granted water rights. Andrew Smith, a DOJ attorney, noted that Arizona, not the federal government, regulates groundwater pumping from private wells. The Forest Service had sought help from the Arizona Department of Water Resources in 2019, asking it to declare the mine’s water use violated the agency’s 1999 instream water right—a legal claim designed to prevent mining-related degradation. The state declined, leaving the Forest Service with no alternative but to approve the expansion.
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A key question in the case is whether the Forest Service must consider the full impact of groundwater depletion on Pinto Creek, even if pumping occurs on private land. The Sierra Club argues the agency excluded over 90% of the creek’s protected area from its analysis, focusing only on a “drawdown area” where the water table drops more than five feet. Outside that zone, the club claims, the mine’s pumping still reduces surface flow by forcing groundwater to the surface downstream.
Science Debate Over Creek’s Flow
Norm James, an attorney for Capstone Copper, which owns the mine, countered that the creek’s flow is already halted by an impermeable granite bed beneath the stream. He argued no further drawdown occurs downstream, meaning the mine’s impact is limited to the analyzed area. However, Delehanty disputed this, explaining that even if the water table drops upstream, the creek’s flow would still decline because all subflow emerges at the surface.
The judge, Dominic Lanza, a Donald Trump appointee, issued a tentative ruling on September 2, siding with the Forest Service on the private well question but aligning with the Sierra Club on the agency’s analysis of subflow effects. The full ruling is pending, though Lanza indicated he would decide as soon as possible. Oral arguments lasted 2.5 hours, suggesting the legal and scientific complexities of the case may require careful review.
