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Air Quality Division | Site/Facility of Interest

Hermosa Project — South32 Hermosa Inc.

Revised On: Oct. 28th, 2026 - 12:03 pm

This site/facility of interest online resource provides interested parties easy access to information about the Hermosa Project, owned by South32 Hermosa Inc., formerly Arizona Minerals Inc. (AMI).

Air Quality Permitting

On Jan. 30, 2026, ADEQ received an application for Significant Permit Revision No. 114492 from South32 Hermosa Inc. for the Hermosa Project. 

  • Application | View Application >
  • Modeling Report | View Report >
  • Emission Calculations 
    • Plan I Facility-Wide Emissions | Coming Soon
    • Plan II Facility-Wide Emissions | Coming Soon
    • Plan I Road Emissions  | Coming Soon
    • Plan II Road Emissions | Coming Soon

ADEQ has developed a draft air quality permit and technical support document for Significant Permit Revision No. 114492, which will be posted soon for public input. As part of this process, ADEQ:

  • Evaluates emissions sources within the facility’s property and estimates the potential emissions from those sources; and
  • Reviews air dispersion modeling conducted by the applicant to ensure that public health will be protected from the proposed facility.

Once ADEQ completes this work, ADEQ will:

  • Conduct an informal community meeting to review the draft air quality permit (see the following community engagement section).
  • Start the formal public participation process by publishing an official public notice in two local newspapers. This public notice seeks interested parties’ input and includes the start and end date of the public comment period (must be a minimum of 30 days) and provides interested parties with links to the draft air quality permit and technical support document on ADEQ’s website and details about how to:
    • Submit comments in writing or in person, and 
    • Attend the formal public hearing.
  • Review and consider all public comments received during this comment period and may make changes to the draft air quality permit prior to submitting it to EPA for its review.
  • Prepare a Responsiveness Summary that addresses all comments received.
  • Submit its proposed final air quality permit and Responsiveness Summary to EPA for its review, in tandem with providing this information to everyone who provided comments.

Following an EPA Order issued in May 2025, ADEQ reopened and revised South32's original Class I Air Quality Permit (No. 96653). ADEQ completed the public process and EPA review, issuing the final revised permit on Feb. 9, 2026.

Community Engagement

2026

On Nov. 12, 2026, ADEQ will host an informal community meeting to discuss the draft air quality permit under Significant Permit Revision No. 114492 beginning at 6 p.m. at Patagonia Elementary and High School located at 200 W. Naugle Avenue, Patagonia, AZ 85624  | View Flyer > | View Event >

The public comment period for the reopened/revised draft air quality permit ended on Sept. 25, 2025 | View 2025 Notice >

On Sept. 25, 2025, ADEQ held an in-person public hearing to accept oral comments on the reopened/revised draft air quality permit. 

The public notice comment period began on Jan. 5, 2024 for the draft air quality permit and was extended to Feb. 26, 2024 | View 2024 Notice >

On Jan. 11, 2024, ADEQ held an informal community meeting to discuss the draft air quality permit | View 2024 Fact Sheet >

On Feb. 26, 2024, ADEQ held a public hearing for the public to comment in person on the draft air quality permit. Both the informal community meeting and public hearing were held at Patagonia Elementary and High School located at 200 W. Naugle Avenue, Patagonia, AZ 85624.

Documents

On Oct. 24, 2022, ADEQ received a Class I Air Quality Permit application from South32 Hermosa Inc.

On June 10, 2024, ADEQ issued the proposed final permit to authorize South32 Hermosa Inc. to begin actual construction, but not operation, of the Hermosa Project. On the same day, ADEQ submitted the proposed final permit and the response to public comments to the U.S. Environmental Protection Agency (EPA) for its 45-day review period.

ADEQ addressed comments on the proposed final permit received from EPA on July 24, 2024, and issued the final air quality permit to South32 Hermosa Inc. on Aug. 26, 2024. 

On May 30, 2025, ADEQ received an Order from the EPA Administrator that granted and denied in part a petition filed in September 2024 that objected to the permit. The Order required ADEQ to reopen and revise the permit within 90 days and solicit public comment. Construction activities for the project are not affected by the Order and can continue | View EPA Order >

ADEQ held a public comment period and public hearing for the public to review and comment on the reopened/revised draft air quality permit. Details can be found in the Community Engagement section. 

After thoroughly reviewing and considering all comments submitted during the public comment period, ADEQ made the determination to issue the proposed final air quality permit to South32 Hermosa Inc. on Dec. 19, 2025. 

ADEQ values the input we received during the formal public comment period, which resulted in changes to the proposed final air quality permit. ADEQ’s changes to the proposed final air quality permit are highlighted in the public comment Responsiveness Summary.  

As required, ADEQ sent the proposed final air quality permit and supporting documents to EPA for its 45-day review. EPA did not object the proposed final air quality permit, and ADEQ issued the final air quality permit on Feb. 9, 2026

For more information about South32 Hermosa Project, visit the Site/Facility of Interest section within the My Community page | View Page >

Looking for water quality permitting related to this facility? | View >