State regulators issued an air quality permit to South32’s Hermosa Mine this week, clearing one more hurdle for the manganese and zinc project planned for the Patagonia Mountains in Southern Arizona.
The Arizona Department of Environmental Quality issued a Class 1 air quality permit after the Environmental Protection Agency completed a 45-day review. While South32 officials called the permit a “significant step,” an environmental group based in nearby Patagonia said they would push the EPA for more action.
Just five miles from the town of Patagonia, the mine’s operations will likely to emit regulated pollutants into the air, requiring an quality permit. State officials said the mine will has the potential to emit air pollution, including nitrogen oxides, carbon monoxide, and “hazardous air pollutants” as workers pursue deposits of Taylor sulfide, a zinc-lead-silver deposit, and Clark oxide, a zinc-manganese-silver deposit.
South32, an Australian company, acquired the Hermosa project in 2013 when they bought Arizona Minerals, and has pushed to develop what company officials call a “modern, state-of-the-art” mine that will extract high-grade zinc-lead-silver and “battery-grade” manganese, central to building high-capacity batteries for electric cars. South32 said it would invest $2.16 billion to develop the mine, including funding to build key infrastructure projects, including water management systems, power, site facilities, underground shaft sinking, and other work.
The mine will also extract silver and lead “essential for harnessing renewable energy,” the company said. Unlike the pit mines expected for copper mining like the long-controversial Rosemont project, the project will sink two shafts and use remote-controlled vehicles to extract the minerals.
The mine will occupy around 750 acres, and South32 has said the mine will use advanced technology to minimize air pollution and use 75 percent less water than other mines. South32 said they will use sealed containers to transport concentrates and manganese ore from the Hermosa project site to other locations, adding “Based on air modeling conducted by third parties,” the potential inhalation exposure for people in the area “is expected to be below the applicable limits established by the Agency for Toxic Substances and Disease Registry for the protection of public health.”
Over the summer, ADEQ issued a proposed air quality permit allowing South32 to continue the mine’s construction, and state regulators sent their proposed final permit and public comments to the EPA for their review. The EPA responded and asked state officials to close a “loophole” that allowed the mine to release some pollutants during an emergency without punishment.
The EPA said this hinges on a determination made last year following an appellate court’s decision. “These provisions, which have never been required elements of state operating permit programs, are being removed because they are inconsistent with the EPA’s interpretation of the enforcement structure of the Clean Air Act in light of prior court decisions from the U.S. Court of Appeals for the D.C. Circuit,” the EPA said.
The EPA asked for more than a dozen changes, including telling state regulators some provisions in the permit were “too vague.”
ADEQ said they addressed the EPA’s comments and decided to issue the permit on Monday, Aug. 26.
South32 said the proposed operations from Hermosa “must adhere to all state and federal air quality standards.”
“Based on third-party, agency-accepted modeling, air emissions from proposed operations at the Hermosa project site are expected to be within the applicable limits established by the U.S. Environmental Protection Agency for the protection of public health,” said South32 in a statement announcing the ADEQ permit.
“Because we have the opportunity to build Hermosa from the ground up, we are using advanced technology, world-class engineering and industry best-practices to enhance safety for the surrounding community when it comes to air quality,” said Pat Risner, president of South32 Hermosa. “This air permit represents a significant step in securing the required approvals to fully develop the site while continuing our proactive approach to protecting the health and well-being of everyone working on our sites and living in our surrounding communities.”
“South32 is dedicated to being a responsible neighbor. That’s why we are engaging with independent public health organizations to inform our approach to monitoring community and worker health,” he said.
Risner said the project will use “industry best-practice systems” to measure dust and manganese levels in surrounding communities before the mine begins operations, and the collected data will help Hermosa “better understand any potential changes as well as provide a baseline assessment of existing community exposure.”
“We are pleased that ADEQ revised the permit based on EPA comments but the issued permit has significant deficiencies,” said Carolyn Shafer with the Patagonia Area Resource Alliance. “We will be filing a Petition to EPA for additional action,” she said.
Following the EPA’s review, there is a 60-day appeal period and the public can ask the EPA to veto the permit if they believe there are deficiencies that have not been addressed, the Arizona Republic reported.
South32 said it plans to open a remote operations center in Nogales, where workers will monitor underground and surface equipment at the site about 28 miles away, the Nogales International reported.
The mine will be developed on private land, limiting how much environmental groups can challenge the mine’s development. The Hermosa site was once home to a Civil War-era mine where extracted lead was sold to the Confederates to make bullets until owner Sylvester Mowry was arrested and charged with treason.
The mine later supported the Trench Camp, a lead smelter and processing facility in the 1960s.
The project was fast-tracked for federal permits last year after federal officials declared minerals like zinc and manganese “critical minerals” under a process known as FAST-41, but a final decision is still not expected until late 2026.
The mine has faced sharp opposition from local groups, including the Tucson-based Center for Biological Diversity and PARA. PARA has also opposed the mine’s permitting with state officials at the Arizona Department of Environmental Quality.
Over the summer, the Forest Service began its own environmental review of the mine.
Last week, a federal judge agreed to a consent motion and outlined a series of deadline for a supplemental review by the U.S. Forest Service as part of a lawsuit over the mine from PARA.
On Wednesday, U.S. District Judge Jennifer G. Zipps ordered the Forest Service to complete a Supplemental Information Report and consider another report under the National Environmental Policy Act and gave both parties a schedule of deadlines extending through April 2025.
Meanwhile, a draft environmental impact statement, or EIS will be published in May 2025 for public review and comment, and federal officials expect approval of mine’s plan of operations by Sept. 2026.