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Our Concerns

Project Overview

The Hermosa Mine, proposed by Australian company South32, in the Patagonia Mountains of southern Arizona, is a large-scale underground mining project targeting lead, zinc, silver, manganese, and other metals tied to global supply chains. Located in the ecologically rich Sky Islands region, the project sits upstream of the town of Patagonia and within a sensitive watershed that supports local drinking water, wildlife habitat, and rural livelihoods.

Key Facts & Impacts

  • ~600–750 acres total surface footprint
  • Includes two main deposits: Taylor (zinc-lead-silver) and Clark (zinc-manganese)
  • Part of a broader land package with tens of thousands of acres under exploration
  • $2.16 billion investment (largest private investment in southern Arizona history)
  • Expected production start: ~2027
  • Estimated mine life: ~28 years (could be lengthened based on deposit size and market demands)
  • Planned processing capacity: ~4.3 million tonnes per year
  • Company claims 75–90% less water use than comparable mines, but this doesn’t account for the ~6 millions gallons/day of groundwater they are permitted to pump, treat, and discharge to Harshaw Creek. Dewatering is not counted as water “use.”
  • Underground dual-shaft mine design
  • Use of dry-stack tailings (less water-intensive than slurry ponds)
  • Planned remote operations center, “El Centro” in Nogales, AZ

Current Actions

  • EPA Air Permit Appeal

    PARA, alongside conservation partners at the Center for Biological Diversity, filed a formal petition to compel the U.S. Environmental Protection Agency (EPA) to act on objections to the mine’s air quality permit.The challenge highlights lack of enforceable pollution limits, inadequate monitoring, and Clean Air Act compliance failures.

    The EPA objected to the permit on several counts, forcing revisions. The revised permit approved by ADEQ still contains serious deficiencies. Further action is being discussed.

  • Barksdale Resources Exploratory Drilling (Humboldt Canyon)

    Barksdale Resources has launched Phase II drilling in Humboldt Canyon, bringing renewed industrial activity to a fragile landscape already under pressure.

    Alongside Earthjustice, we have an active lawsuit against the U.S. Forest Service for issuing these permits without fully analyzing cumulative impacts of the project’s proximity to the South32 Hermosa Project.

    The project includes up to 30 drill rigs running 24/7 for the next 7 years in critical habitat for threatened species including the Mexican spotted owl and yellow-billed cuckoo.

  • U.S. Forest Service Final Environmental Impact Statement (EIS)

    The U.S. Forest Service has announced that the final Environmental Impact Statement (EIS) for the South32 Hermosa Project was released on March 6, 2026, a critical milestone for our community.Last spring, PARA brought together a strong coalition of experts to rigorously review the draft EIS.

    In total, 16 organizations submitted 221 pages of detailed technical comments, exposing major gaps in the analysis and offering clear, science-based solutions to better protect our water, air, and surrounding ecosystems.

    Our legal and technical teams are ready to respond swiftly and ensure accountability at every step.

South32 Hermosa Mine, facing north from FR 4701

Photos by Russ McSpadden, Center for Biological Diversity. February 24, 2026

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