South32 Hermosa President Pat Risner and three newly hired consultants spoke with the Santa Cruz County Advisory Panel on the Hermosa Project at a Nov. 15 meeting at the Tin Shed Theater in Patagonia.
Risner, South32 staff, and other members of the panel, including Carolyn Shafer of the Patagonia Area Resource Alliance, gave updates on various aspects of the Hermosa project (see sidebar below), but the bulk of the two-hour meeting was devoted to addressing a single topic: manganese. Here’s what was discussed.
Manganese Processing Sites
Risner reported that a pilot plant for processing battery-grade manganese from ore—in what he described as “a lab setting”—has been operating at the Hermosa mine in the Patagonia Mountains since July.
“We’re now at the point with that pilot plant where it’s producing sufficient volumes for making that available to customers to test it,” he said. “There’s a long process for customers to determine whether it meets their specifications.”
Risner said South32 now has three memorandums of understanding with customers building electric vehicle battery production sites in the U.S., and is in discussions with nine others. He said that these customers will require “small volumes” of processed manganese in early 2026, which South32 plans to produce at a “small-scale demonstration facility.” A much larger, full-scale commercial facility will come online later.
(In a Nov. 27 email to the PRT, Risner clarified that the site for the demonstration facility has not yet been finalized. “We have not yet determined its location, as well as the location for the full-scale facility, but they will not likely be in the same location,” Risner said. “However, both facilities will feature leading-edge technology designed to ensure all materials are handled safely and securely—including sealed-container transport and enclosed storage—with strict operational controls and regulatory oversight.”)
At the Nov. 15 Advisory Panel meeting, Risner noted that sentiment from the Panel and the broader community was playing an important part in making the decision on where the full-scale facility would be located. He said this facility has an unknown time frame. “We don’t know when we would take the manganese project to full production, because we still are learning from the customers the rate at which their facilities will come online and the demand will grow,” he said.
Risner said the full-scale facility will likely be around 120 acres at first, and eventually 250 acres, with tailings that could be as high as 5-6 stories.
Manganese Production Process
Risner said videos and information circulating online regarding historical and contemporary manganese processing around the world had little to nothing in common with the specific process that Hermosa was developing.
“This facility is not a smelter,” he said. “It’s really just a building with a bunch of tanks in it, where we take the manganese oxide and convert it into a high-purity manganese sulfate through a series of treatment steps.”
Risner said Hermosa’s process of mining manganese and transporting it to the processing facility was designed not to generate manganese dust.
“Most of the videos you see online are where they’re actually smelting [alloy] into a manganese metal that goes into steel production,” he said. “About 90% of the manganese in the world right now goes into steel production, where they’re hauling manganese concentrates that are going into smelters. It’s really fine material, which makes it easier to be airborne.
“That’s not what we’re doing [at Hermosa]. We will be hauling ore that comes from the mine that is actually the size of your fist, which really can’t become airborne like really fine particles. Nonetheless, it will be direct discharge of ore into sealed containers, and the onload and offload will be fully contained and enclosed. From the time it’s mined to the time it goes into a container on a truck and transported to the processing facility, offloaded into the facility to produce the battery-grade manganese and loaded to go to the customer, it’s not exposed to the environment at any point. We have the ability to do that now; in the ’60s and ’70s they didn’t necessarily have the ability to do that.”
Risner said the dry stack tailings at the processing facility will be compacted to 95% compaction and have a clay barrier underneath, as well as two layers of geo-membrane liner and other protective features that are also being employed at the tailing facility at the mine site.
“Obviously we cap this ultimately down the track, but the compaction helps quite a bit with the dust suppression,” he said. “We’ll have other measures and engineering controls in place too. It’s really an ‘engineered fill,’ not a tailings stack, because it gets dewatered, it gets placed in thin layers and compacted, much like you would compact the base of a road before you lay asphalt.”
He said South32 will share more details of the processing plant, including renderings of the plant’s interiors, as the design evolves.
Impacts of Manganese Mining and Processing on Communities and the Environment
In early November, South32 contracted with Ramboll, an independent multinational consultancy with headquarters in Copenhagen, to assist the Hermosa project in limiting exposure of manganese and other minerals to the local community and the environment.
Risner said, “It’s important that we understand the condition of the environment and the health of the community before we ever do anything, to make sure those [health and safety] controls we have are effective throughout the life of the mine. Ramboll will advise us on how to bring in the right partners to do that—credible third parties and independent entities that are external to South32—and how to design it to be most effective, and make sure it’s credible, make sure it’s done properly, in a way in which the community can accept the outcomes.
“We will most likely be the first manganese operation in the world that has done a community health baseline assessment before it started operations. Most of the other manganese districts in the world, whether it’s in the Kalahari in South Africa or northern Australia or Gabon or other places, those industries started in the ‘60s and ‘70s. The practice of baseline community health assessments like we can do today, obviously much of that was not done then.”
Three Ramboll consultants outlined their role in this project. Dr. Rosalind Schoof, PhD., a board-certified toxicologist, with 35 years’ experience in community exposure assessment around mining and smelting sites, Alma Feldpausch, a board-certified toxicologist and risk assessor, were in person from Ramboll’s Seattle office, and Dr. Robinan Gentry PhD., a board-certified toxicologist with 35 years’ experience presented remotely from Baton Rouge. Ramboll consultants will help South32 develop a scope of work for assessing and measuring the potential impacts of the Hermosa project on health and the environment. Ramboll will then identify and engage with researchers in the region to work on the project.
“We are here to help, but certainly not to replace independent experts and academic partners,” Feldpausch said.
The immediate next step is to start on a process called a Health Impact Assessment, which will help researchers to anticipate future issues. The HIA will look at all five minerals that will be mined at Hermosa: manganese, lead, zinc, silver and copper.
“This is a great way to troubleshoot before troubles come our way,” Feldpausch said. Researchers will be looking for ‘pathways’ where exposure could be high enough to carry a health risk.
South32 is trying to finalize the scope of the project before the end of the year. The timeline for the HIA will depend partly on the availability of the scientists who will be brought into the project, as well as other factors. The goal is to complete HIA work before digging starts at Hermosa in 2025.
Dr. Schoof encouraged the public to consult a ‘ToxFAQ’ produced by the CDC regarding health issues related to manganese, available online at www.atsdr.cdc.gov/toxfaqs/tfacts151.pdf
More Updates From South32
Also discussed at the Nov. 15 Advisory Panel meeting:
South32’s Funding Decision on Hermosa Nears
Risner said South32’s internal ‘pre-feasibility study’ to determine if the Hermosa project would be financially viable for the company was “essentially done. An independent review is going on now. And that’s going to carry on through the end of the year. The actual decision on the funding will probably be at the end of January or early February.”
Cross Creek Connector and 9001 Bridge Work Progress
Risner said Hermosa was finalizing ‘phase 1’ of the Cross Creek Connector road, with a target completion date of June 2024.
He said the so-called ‘9001 Bridge’ project on Harshaw Road is proceeding—a detour is in place, and concrete is being poured. The projected completion date is March 2024.
IROC Site Decision Near
South32 hopes to reach a decision on the site for its ‘Integrated Remote Operating Center’ (IROC) before the end of the year.
South32 describes the IROC in its promotional literature as a commercial building on a five-acre site housing a command center where employees will “remotely monitor and operate some of the mining equipment” at the mine site.
“We’ve committed to it being somewhere in the I-19 corridor, in the Nogales-Rio Rico area,” Risner said. “We want to co-locate it in areas where there’s job training, where there’s development opportunities, and where it makes it easy for anyone in the community who wants to work there to show up. Forty percent of our workforce will work at the IROC.”
Fast-41 Process Approaching New Milestone
As part of the ongoing Fast-41 federal permitting process, the Forest Service has a Dec. 17 deadline to render a ‘completeness determination’ of the ‘Mine Plan of Operations’ for the Hermosa project that South32 submitted in August. Risner said he was not sure when the complete Plan of Operations document would become public.
The Fast-41 process can be monitored at: permits.performance.gov/permitting-project/fast-41-covered-projects/south32-hermosa-critical-minerals-project