USFS approval of South32 Hermosa mine plan: schedule and infrastructure lens for engineers
Reviewed by Joe Ashwell

First reported on MINING.com
30 Second Briefing
US Forest Service approval of South32 Hermosa’s Final Mine Plan of Operation clears construction of key ancillary works on federal land in southern Arizona, including a primary access road, a secondary drystack tailings storage facility, high‑voltage transmission line and water discharge points. The Hermosa district hosts one of the world’s largest undeveloped zinc deposits plus battery‑grade manganese and the Peak copper discovery, with a projected 70‑year mine life producing five federally designated critical minerals. Construction on private land is about 50% complete, with underground zinc mining targeted for late 2027 and first plant product in H1 2028.
Technical Brief
- Final Mine Plan of Operation approval enables construction of the secondary drystack tailings storage facility on USFS land.
- Plan approval also permits a second access road and defined water discharge points on Forest Service ground.
- Hermosa is the first mining project fully processed under the federal FAST‑41 permitting framework.
- Initial works now allowed include earthworks, survey control, exploration drilling platforms and geotechnical investigation programmes.
- Federal agencies involved span the Forest Service, USDA, US Fish and Wildlife Service and the Permitting Improvement Steering Council.
Our Take
Hermosa’s FAST‑41 status, highlighted in our July 29, 2026 coverage, signals that the US Forest Service and the Federal Permitting Improvement Steering Council are treating this zinc‑silver and critical minerals hub as a template for compressed federal timelines on complex underground builds in the US Southwest.
With South32 already lifting first‑stage capex for the Taylor deposit at Hermosa to $3.3 billion and pushing first output to H2 FY2028 in our April 30, 2026 piece, a 70‑year potential operation life implies a long payback window that will make cost control on early infrastructure and power‑water solutions in Arizona particularly sensitive.
Our database shows multiple Southwest US copper and lithium projects, including Ivanhoe Electric’s Santa Cruz deposit and Thacker Pass, running into basin‑scale water constraints; Hermosa’s multi‑decade zinc‑manganese‑copper profile in southern Arizona will likely face similar scrutiny on groundwater and surface‑water allocations as it moves from plan approval to detailed engineering.
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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