The South32 Hermosa Project — a developing mine in Southern Arizona — says the Arizona Department of Environment Quality has issued an updated Class I Air Quality Permit following a review by the U.S. Environmental Protection Agency.
Last May, the EPA partially denied a petition filed by the Center for Biological Diversity and other health and environmental groups to reject an air quality permit issued by ADEQ for the developing mine that’s located outside of the town of Patagonia.
In June 2024, ADEQ issued the proposed final air quality permit to authorize South32 to begin construction and also referred the proposed permit and response to public comments to the EPA for a required 45-day review period. There were no objections by the federal agency, however, it did provide comments that ADEQ says were addressed.
A final air quality permit was issued to South32 in August 2024. That September, however, the EPA received a petition from environmental groups calling for a review of the air quality permit and in May 2025, the federal agency issued an order to ADEQ to reopen and revise the permit within a 90-day period and solicit public comment.
The petitioners argued that the permit failed to assure compliance with specific requirements under the Clean Air Act and that the Hermosa project threatens to release hundreds of tons of toxic air pollution annually, putting communities and the environment at risk.
“Clean air is essential for people, the environmental and all living creatures,” said Jeremy Nichols, senior advocate at the Center, in a statement.
The Center later announced that in June, the EPA had rejected the air pollution permit.
Pat Risner, Hermosa’s president, told AZPM that the permit was never denied.
“EPA asked ADEQ to supplement the permit, [to] put some additional language in…They wanted us to report on the effectiveness of some of the controls in the mine,” he said.
Five out of 20 claims were reviewed, followed by a public hearing that was held in Patagonia last September.
Some of the commenters cited concerns about the lack of clear limits, transparency and strong monitoring, as well as concerns towards manganese emissions, greenhouse gas emissions, clear air, dust pollution or the lack of independent verification of blasting and explosive use, according to a responsive summary document by ADEQ.
Manganese, which is one of the federally designated critical minerals that South32 wishes to mine, can cause several neurological side effects and illness due to overexposure.
While some of the concerns were out of ADEQ’s scope for the reopening of the particular permit, some of the changes that were made to the revised permit include new monitoring, recordkeeping and reporting requirements, and compliance reassurances and is valid for five years.
The final air quality permit was issued on Monday, Feb. 9.
