Project Information
Project Title:
South32 Hermosa Critical Minerals Project
Sector:Mining
Project Location Address:
- Street address 1: 2210 E Fort Lowell Road
City: Tucson
State: Arizona
Zip: 85719 - Country: United States
Street address 1: 1860 E. River Road, Suite 200
City: Tucson
State: Arizona
Zip: 85719
County: Pima County
Coordinates:
- Latitude: 31.463702
Longitude: -110.726006
Project Sponsor Contact Information:
- Company Name/Agency: South32 Hermosa
Project Sponsor: South32 Hermosa, a wholly owned subsidiary of South32 Ltd
Street Address: 2210 E Fort Lowell Rd
City: Tucson
State: Arizona
Zip: 85719
POC Name: Pat Risner
POC Title: President, South32 Hermosa
POC Work Phone: 520-405-8895
POC Email Address: Pat.Risner@South32.net
Alternative Point Of Contact (Optional):
- Company Name/Agency: South32
Project Sponsor: South32 Hermosa
Street Address: 1100 15th Street, Suite 400
City: Washington
State: District of Columbia
Zip: 20005
POC Name: Judy Brown
POC Title: Head of External Affairs
POC Work Phone: 520-603-2799
POC Email Address: Judy.Brown@South32.net
Project Purpose:
South32 Hermosa Inc. (South32) is in advanced study and planning stages for the Hermosa Critical Minerals Project (Hermosa) - a zinc and manganese mining and processing operation. Hermosa contains one of the largest undeveloped zinc resources in the world and has proven potential to produce a battery-grade manganese that meets current battery chemistry requirements as well as evolving battery chemistries intended to meet the United States supply chain needs. Zinc and manganese are both designated critical minerals by the U.S. Geological Survey. Executive Orders 14154 ‘Unleashing American Energy’ and 14156 ‘Declaring a National Energy Emergency’ both cite the development of critical minerals as essential for national security, defense, and the economy. South32 plans to construct a small-footprint, underground mining operation applying best-in-class engineering principles.
Project Description:
The Hermosa Project is located at longitude 31.463702, latitude -110.726006 in an historic mining district in Santa Cruz County Arizona, near the US-Mexico border. Part of the Project area will involve subsurface and surface disturbance of lands within the Coronado National Forest.
Nearly 25 percent of Santa Cruz residents live below the poverty line, and the county's unemployment rate is consistently 50 percent above the state average. South32’s planned investment at Hermosa (estimated at $2.16 billion) would be the largest ever in Santa Cruz County bringing much economic benefits, including providing 625 direct mine worker jobs and supporting an estimated 1,021 workers in other industries for a total employment impact of approximately 1,646 workers in Santa Cruz County. South32 will work with local and State educational institutions to develop training programs ensuring workforce readiness with priority given to local hiring at the Hermosa Project. The Hermosa mine development would nearly double the county’s property tax base, which is currently ~$14 million. The Project’s contributions to the county’s GDP and economic output would equal about 20% of the current GDP and economic output for Santa Cruz County.
The proposed mining method at Hermosa is underground stoping complemented by backfilling of the stopes to mitigate the risk of surface subsidence and reduce the amount of tailings storage. Tailings will be managed using a dry-stack method that will significantly limit the surface disturbance and deliver the highest standards of safety and water conservation. South32 has already constructed an existing dry-stack facility in 2020 as part of a $30 million remediation of historic mine waste on its patented fee land. This remediation was completed in accordance with the Voluntary Remediation Program of the Arizona Department of Environmental Quality.
The company has also conducted Class III cultural resource surveys across its fee lands and adjacent federal lands. These surveys were conducted consistent with Arizona State Historic Preservation Office and Department of the Interior standards. Although there are no Tribal Nations located in the immediate vicinity of the Project, South32 recognizes and respects historic tribal affiliations in the area and is proactively engaging with local Tribal Nations.
Biodiversity, including sensitive species, monitoring has been ongoing since 2012. The Hermosa Project is being designed to avoid and minimize adverse impacts to biodiversity and critical habitat in the area, to the extent practicable.
Technical and Financial Ability:
Statement regarding the technical and financial ability of the project sponsor to construct the proposed project.
South32 Hermosa Inc. is a wholly owned subsidiary of South32, Ltd, a globally diversified mining and metals company.
• Technical
South32 operates several mines and is the largest producer of manganese ore in the world. The company conducts and measures sustainability performance against international standards and initiatives, including the International Council of Mining and Metals’ Mining Principles, United Nations Sustainable Development Goals and United Nations Global Compact. South32 also supports global efforts to align sustainability reporting standards and participates in several international working groups.
South32’s suite of assets include open-cut and underground mines, refineries, smelters and associated infrastructure. South32 produces bauxite, alumina, aluminum, copper, silver, lead, zinc, nickel, metallurgical coal, and manganese. We have more than 25 active exploration programs across the globe to discover our next generation of mines.
The Hermosa deposit and mine-design is like South32’s Cannington mine in Queensland Australia. The Cannington mine has been in operation for more than 20 years and is one of the world’s largest producers of silver, zinc, and lead. The operation consists of an underground hard rock mine and surface processing facility, a road-to-rail transfer facility and a concentrate handling and ship loading facility.
• Financial
South32 is a global mining and metals company listed on three exchanges and has a market capitalization of $15 billion as of March 2023. While South32 has applied for federal financial assistance under the Defense Production Act (DPA) Title III program administered by the Department of Defense (described below), South32 is not dependent on government funds to develop the Hermosa project.
Summary of Financing, Reviews, and Authorizations:
• Federal Financing
South32 has sought $20 million in funding under DPA Title III for expansion of domestic production capability and capacity (“Accelerated Access to Domestic Manganese Ore for Advanced Materials Assessment”). Any federal funds would be matched by a $43 million investment from South32 (including in-kind expenditures) to construct an exploration decline concurrent to ongoing feasibility study work related to the mine and processing facilities. The Hermosa Project can happen without federal financial assistance. DPA funding would facilitate early access to the ore body and shorten the time for production of manganese ores.
• Environmental Reviews and Authorizations
Operations at Hermosa would occur on and under lands of the Coronado National Forest. Upon South32’s submission of a Mine Plan of Operations to the US Forest Service (USFS) for approval under the USFS locatable minerals regulations, the USFS has become the lead federal agency for purposes of compliance with the National Environmental Policy Act (NEPA) and coordinating with other federal and non-federal parties on securing authorizations required by other federal and state environmental laws. These approvals will include: consultation with the U.S. Fish & Wildlife Service as required by the Endangered Species Act (ESA); securing a Section 404 permit under the Clean Water Act from the U.S. Army Corps of Engineers, if applicable; and consultation with the State Historic Preservation Officer and appropriate Tribal Historic Preservation Officer(s) under the National Historic Preservation Act (NHPA).
Project Assessment:
1. South32 Hermosa’s zinc-manganese integrated mine development is surrounded by the Coronado National Forest. South32 Hermosa is required to submit an Exploration and Mine Plan of Operations to the US Forest Service relative to proposed expansion of the Hermosa Project onto National Forest System lands. US Forest Service review and approval process will trigger NEPA and numerous other federal and state authorizations will be required.
2. South32 estimates that the total cost to construct the Hermosa Project will be approximately $2.16 billion – well in excess of the statutory minimum project cost of $200 million.
3. The Hermosa Project does not qualify for abbreviated authorization or environmental review processes under any applicable law.
The South32 Hermosa Project falls within (1) the mining sector (limited to “extracting ore, minerals, or raw materials from the ground”) and (2) manufacturing sector as operations will include beneficiation and mineral processing of the zinc and manganese ores.
Form Submitter Contact Information:
Name: Judy Brown
Title: Head of External Affairs
Work Phone: 520-603-2799
Email: Judy.Brown@South32.net
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Forest Service: Hermosa Critical Minerals Project
https://www.fs.usda.gov/r03/coronado/projects/65668
https://usfs-public.app.box.com/v/PinyonPublic/folder/249404091619
Consideration of project mitigation is a continuous process through completion of the EIS and Record of Decision. Multiple categories of mitigation have been incorporated into project planning:
- Design Features—environmental protection measures committed to by South32 Hermosa Inc. in the Critical Minerals Exploration and Mine Plan of Operations (MPO) and measures committed to by UNS Electric, Inc. in the Standard Form 299 Application for Transportation, Utility Systems, Communications, and Facilities on Federal Lands and Property.
- Standard permit conditions and best management practices (BMPs)—predictable industry standard measures or requirements designed to comply with regulations and reduce impacts to the environment.
- Measures which contribute to the conservation of ESA-listed species and critical habitats—Final conservation measures for ESA-listed species were also listed in the Biological Opinion (signed on 2/26/2026). Reasonable and Prudent Measures and their implementing Terms and Conditions are also included in the final Biological Opinion, and have been added as attachment 1 to the draft Record of Decision (published 6/6/2026).
- Avoidance project design features and mitigation measures produced in support of NHPA Consultation—The Forest Service, in consultation with NHPA Section 106 Consulting Parties, has executed a project-specific Section 106 Programmatic Agreement for the Project (Appendix E of Final EIS). As part of the agreement, South32 Hermosa and UNSE developed and are required to implement Historic Properties Treatment Plans (HPTPs) to resolve adverse effects on historic properties. The HPTPs include a monitoring and discovery plan, and avoidance and mitigation measures for historic properties.
- Additional mitigation measures—The Forest Service used a structured screening process to consider additional measures identified or suggested by CNF Interdisciplinary Team members, stakeholders, agencies, and the public. The process followed and the outcome of the measures screened is documented in the Hermosa Critical Minerals Project Mitigation and Monitoring Screening and Evaluation Report. Measures that passed through the screening process and other measures identified through this process are presented in Appendix A of the Final EIS. The Hermosa Critical Minerals Project Mitigation and Monitoring Screening and Evaluation Report provides full details on the screening results, including the measures that did not pass the screening criteria.
Appendix A of the Final Environmental Impact Statement (published 6/6/2026) lists applicant-committed project design features, Forest Service standard permit conditions and best management practices, conservation measures for ESA-listed species, mitigation measures produced as a result of NHPA consultation, mitigation measures produced through the Coronado National Forest's screening and evaluation framework, management plans that will need to be produced in advance of approval of the final Exploration and Mine Plan of Operations, and measures required by other regulatory and permitting agencies. These project-specific avoidance, minimization, and mitigation strategies have been formulated based on scoping, comment period, interdisciplinary, and interagency input.
N/A
- On April 26, 2024, the Coronado National Forest posted the proposed South32 Hermosa Inc. Critical Minerals Exploration and Mine Plan of Operations (MPO) on the project website two weeks in advance of the scoping period. You can find the MPO in the Supporting Documentation folder here: https://usfs-public.app.box.com/v/PinyonPublic/folder/249404091619.
- A pre-recorded educational webinar was recorded to provide information about NEPA and how community members can engage in the NEPA process. This webinar was released on May 6, 2024, and was made available online in both Spanish and English.
- The scoping period for the Hermosa Critical Minerals Project ran from May 10 through June 10, 2024.
- The scoping period was announced through news releases, through the Coronado National Forest project website at https://www.fs.usda.gov/project/coronado/?project=65668, through Coronado National Forest social media at https://www.facebook.com/CoronadoNF/ and https://twitter.com/coronadonf, and through the Santa Cruz County website and the Town of Patagonia website.
- Additional opportunities to learn about proposed project activities and specific resource areas that will be analyzed in the project’s Environmental Impact Statement were provided at two in-person open houses. One open house was on May 20, 2024, between 4:30 pm and 6:30 pm at Patagonia Union High School, 200 Naugle Avenue, Patagonia, AZ, and the other was on May 21, 2024, between 4:30 pm and 6:30 pm at Hotel Americana, 639 N. Grand Avenue, Nogales, AZ. Spanish speakers were present and available at both in-person open houses. All written materials at the in-person open houses was provided in both Spanish and English.
- For those unable to attend either of the in-person open houses, a virtual open house accessed online was made available on May 20, 2024 at https://hermosacriticalmineralseis.com/. This virtual open house provided similar information as the in-person open houses, and included an option for visitors to submit project comments during the designated scoping period. The virtual open house materials were available in both Spanish and English.
- A 45-day public comment period on the Draft Environmental Impact Statement will commence with publication of the Notice of Availability in the Federal Register. This public comment period is scheduled to run from May 9 through June 23, 2025.
- Additional opportunities for public involvement and input on the proposed Hermosa Critical Minerals Project will be provided at two in-person open houses. One open house will be on May 27, 2025, between 4:30 pm and 6:30 pm at Patagonia Union High School, 200 Naugle Avenue, Patagonia, AZ, and the other will be on May 28, 2025, between 4:30 pm and 6:30 pm at Nogales High School, 1905 North Apache Boulevard, Nogales, AZ. Spanish speakers will be present and available at both in-person open houses. All written materials at the in-person open houses will be provided in both Spanish and English.
- For those unable to attend either of the in-person open houses, a virtual open house accessed online will be made available on May 9, 2025. This virtual open house will provide similar information as the in-person open houses, and it will include an option for visitors to submit project comments during the designated public comment period. The virtual open house materials will be available in both Spanish and English.
- A 45-day opportunity for filing of objections in accordance with regulations at 36 CFR 218 was announced via a legal notice in the Newspaper of Record, The Daily Territorial, on March 6, 2026. Outreach to inform the public of this opportunity to file objections was conducted via a number of additional outlets, including Nogales International, The Patagonia Regional Times, The Herald Review, the Federal Register, electronic mail distribution, social media, and a press release.
The US Forest Service was notified on 8/8/2024 that the U.S. Army Corps of Engineers - Regulatory had issued the approved jurisdictional determination for this project and there are no Section 404 waters within the project area. U.S. Army Corps of Engineers - Regulatory therefore requested to be modified from a cooperating agency to a participating agency. This also required removing the action from the project timetable.