South32’s $2B Hermosa Arizona mine: NEPA clearance insights for project teams
Reviewed by Tom Sullivan

First reported on MINING.com
30 Second Briefing
South32’s $2 billion Hermosa zinc-silver project in southern Arizona has secured a Final Record of Decision from the US Forest Service, completing NEPA review for key infrastructure on Coronado National Forest land, including a primary access road, dry-stack tailings facility and part of a 138 kV transmission line. The mine, about 80 km southeast of Tucson and occupying roughly 750 acres, is designed to use about 90% less water than comparable regional operations and could produce up to five federally designated critical minerals. South32 has committed to more than 135 conservation, mitigation and monitoring measures, with construction on private land already about 50% complete and full production targeted by 2029.
Technical Brief
- Final Record of Decision from US Forest Service specifically covers access road, dry-stack TSF and 138 kV line segment.
- Hermosa was the first mining project accepted into the federal FAST-41 coordinated permitting programme.
- NEPA review involved over 120 days of public comment plus coordination across six federal and state agencies.
- Consultation included 12 Tribal governments, feeding directly into route selection and facility layout refinements.
- Dry-stack tailings facility was redesigned to avoid identified sensitive plant species within Coronado National Forest.
- Primary access road alignment was altered to reduce heavy-vehicle traffic impacts through the town of Patagonia.
- Project design now incorporates wildlife crossings and enhanced noise and emissions controls to limit surface disturbance.
- More than 135 conservation, mitigation and monitoring measures are now enforceable conditions under the approved mine plan.
Our Take
Hermosa strengthens South32’s pivot away from aluminium and towards base and critical minerals, echoing the company’s recent $5.6–$5.9 billion divestment of its aluminium portfolio to Alcoa and its ongoing copper exposure via Sierra Gorda in Chile.
Being able to claim up to five US-designated critical minerals from a single Arizona site positions Hermosa unusually high in our database of ‘critical minerals’ stories, where most US entries involve one or two target commodities per project.
The combination of FAST-41 treatment, coordination across six agencies and extensive tribal consultation suggests Hermosa could become a permitting template for other US zinc, manganese and copper projects seeking to navigate federal land and conservation constraints.
Prepared by collating external sources, AI-assisted tools, and Geomechanics.io’s proprietary mining database, then reviewed for technical accuracy & edited by our geotechnical team.
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