PATAGONIA, Arizona—Deep in the Patagonia Mountains, puffs of cool air from a cavernous natural spring interrupt the desert heat. The water bubbles up from an underground aquifer and trickles into Alum Gulch, orange from minerals such as magnesium and calcium, left over from mining in the area.
Bob Proctor, a local resident, and Kerry Schwartz, a retired hydrogeology faculty member and water resources educator at the University of Arizona, unpacked a water sampling probe and sat to test the water quality of the spring and the creek.
The pair are part of Friends of Sonoita Creek, a volunteer organization working to monitor the health of the Patagonia watershed. While the spring water usually tests clean, the slow-moving stream regularly shows metals from old mines that dot the landscape.
“We see really compromised water in Flux Canyon and Alum Gulch,” Schwartz said. “Usually, it’s more acidic than it should be because of the mining.”
Friends of Sonoita Creek was founded in 2004. The group monitors the watershed’s quality and biodiversity as South32, an Australian mining company, pursues development of the Hermosa project, a vast zinc and manganese mine backed by the Biden administration.
Members are gathering baseline data on the health of both groundwater and the creeks in the Patagonia region, about 175 miles southwest of Phoenix, before the new mine starts operations. The mine benefits from multiple federal incentives because it would extract metals essential for the nation’s clean energy transition, but community members in Patagonia fear it will pollute and dry up the scarce water they rely on.
The organization hopes to use the data to hold the mine accountable if it violates its permits, or if its operations lead to degraded water quality or pollution.
“If you keep asking questions and keep getting the data, then … I mean, I think we’re going to be in this conversation a long time, as long as they’re going to try to have the mine,” Schwartz said.
Every week since 2018, volunteers have sampled surface water from points along Harshaw and Sonoita Creeks, as well as groundwater from 55 known seeps or springs in the area. Alum Gulch is an impaired waterway from legacy mining in the Patagonia Mountains and it trickles into Sonoita Creek, which flows through the town of Patagonia, according to the Arizona Department of Environmental Quality.
The main concerns of activists revolve around the mine’s plan to pump, treat and discharge up to 6.5 million gallons of groundwater a day from the mountain into Harshaw Creek, which flows toward Patagonia and into the larger Sonoita Creek.
The Hermosa Project
South32 acquired the project in 2018 from Arizona Mining Inc. and has been constructing the mine ever since. The company aims to mine two federally designated critical minerals, zinc and manganese.
The Biden administration deemed both minerals essential to mine and process domestically to aid in the country’s transition from fossil fuels to green energy. Zinc is an important material for wind turbines and solar panels, and South32 hopes to sell manganese to electric car battery producers after it begins production in 2027.
“Ultimately, the goal is to create two domestic supply chains for two federally designated critical minerals for which, right now, we are either 100 percent or highly reliant on foreign sources,” said Pat Risner, president of the Hermosa project.
The Hermosa mine would be the only mine in the United States able to produce battery grade manganese. In February, South32 invested an additional $2.1 billion to begin mining a zinc deposit by 2027.
On Sept. 20, the Hermosa project received a $166 million grant from the U.S. Department of Energy to provide up to 30 percent of the cost of building its manganese production facility. That award followed a May 17 announcement that South32 would receive a $20 million grant from the Department of Defense under the Defense Production Act battery grant program to accelerate the production of battery grade manganese.
Risner told Inside Climate News that the Hermosa project is in communication with multiple major battery manufacturers in the United States. In a news release announcing the September grant, the company said “the development of the facility and manganese deposit at Hermosa is subject to further study.”
Three federal incentives allowed the project to advance, Risner said.
“The first was when President Biden invoked the Defense Production Act in March of 2022 for the five battery metals, of which one was manganese,” he said.
The second big boost came from the project’s inclusion in the Fast-41 process, which sped up the coordination of its environmental permitting. The third major incentive, Risner said, is the ability to access federal funding from the Inflation Reduction Act and Bipartisan Infrastructure Law.
But residents worry their community will be sacrificed as the country implements renewable energy systems.
“I essentially live in grief, grief for the reality of what is happening and the devastation that it will bring to this incredibly biologically diverse area,” Carolyn Shafer, a local advocate, said about the mine. “We will be a sacrifice zone in every sense of that term.”
Shafer leads the environmental group Patagonia Area Resource Alliance (PARA), which, like Friends of Sonoita Creek, is working to mitigate the potential environmental impacts of the Hermosa project.
The Hermosa project began discharging smaller amounts of treated water into Harshaw Creek in 2021 after the approval of its Aquifer Protection Permit.
PARA sued the Arizona Department of Environmental Quality immediately after the agency issued that permit, according to Shafer.
“We have been very actively involved with state and federal agencies, who are not following the letter of the existing law, and the existing law does not even do enough to protect this highly biologically diverse area,” said Shafer.
PARA also sued the Arizona Department of Environmental Quality this year over South32’s application to renew its Arizona Pollutant Discharge Elimination System Permit.
In its defense, the company argued that the mine aims to operate as sustainably as possible concerning its water usage, projecting that operations will use 75 percent less water than comparable mines.
“Water is a precious resource everywhere and it’s especially precious in the desert Southwest,” said Risner. “So minimizing the amount of freshwater use is important.”
PARA, though, sees South32 as posing one of the biggest risks to water resources in the area.
Shafer and her group would prefer no mining in the Patagonia Mountains. The group intends to continue challenging the mine in court and through the permitting process.
Eco-Tourism and Worsening Drought
The historic town of Patagonia, in Santa Cruz County, had a population of around 800 residents in 2022, according to the town’s website. Despite a legacy of mining in the Patagonia Mountains, the town has become an international destination for eco-tourism.
Nature-based tourism contributed $23 million to the county’s economy in 2019, including directly supporting 320 jobs, according to a 2021 University of Arizona study. The county is home to the Coronado National Forest, where tourists frequently birdwatch, mountain bike and hike.
The county’s long-term drought conditions worsened between April and June, according to the Arizona Department of Water Resources. The ongoing drought coupled with the lack of regulations on groundwater usage in Patagonia’s watershed—the area is not an Active Management Area—underpin residents’ concerns about what an industrial project like Hermosa could mean for the water supply.
Exceptional long-term drought persists throughout the state and is prominent in the southeast and southwest, according to Arizona’s Quarterly Drought Status Update published in June 2024. The drought status is calculated using years of data precipitation levels. Long-term drought refers to the status of aquifer recharge, streamflow and water supply, according to the state’s Climate Office.
The work of activists to collect data increased in urgency this spring as South32 and the federal government plowed ahead with an environmental review under the National Environmental Policy Act. Residents had 30 days, starting May 10, to provide comments during a scoping period to determine which environmental issues would be studied by the Forest Service, the federal agency that manages part of the land that South32 would mine.
South32 cannot begin full operation and production until the environmental review is complete. Officials from Santa Cruz County and Patagonia sent a letter requesting a longer comment period and more active engagement with the county’s Spanish-speaking residents, to no avail.
What Will Happen to the Aquifer?
Enormous underground pools of ancient water are contained within the Patagonia Mountains. No one knows how much water the aquifer contains, according to Chris Gardner, a retired hydrogeologist volunteering with Friends of Sonoita Creek. Local environmental activists are concerned the mine’s operations will do irreparable harm to the aquifer.
In order for South32 to access the zinc deposit, it plans to dig channels 2,900 feet deep into the mountain. To do so, and to protect employees and equipment, South32 must pump water out of the aquifer and keep pumping as it mines to prevent leaks into the mining channel, according to Risner.
As stated in the Hermosa Project plan of operation, the company intends to treat the water pumped out of the mountain in a nearby treatment plant, and then discharge up to 6.5 million gallons of treated groundwater a day into Harshaw Creek, a waterway in the Sonoita Creek watershed that flows into Patagonia.
“We’ve been collecting surface and groundwater samples for more than five years for baseline, and the additional studies we’ve done, which were not necessarily all required for permits, give us a good understanding of what would and wouldn’t happen there long-term,” Risner said.
But Schwartz, the other retired hydrogeologist volunteering with Friends of Sonoita Creek, said that because the mountains contain so many fractures, pumping large quantities of water out could deplete the groundwater levels and change the pressure underground. Natural water flows, like springs and seeps, could be reduced if the groundwater levels throughout the mountain are depleted by pumping water out, according to research on mountain aquifers by the Utah Geological Survey.
Proctor, one of the local residents assisting with water testing, said areas like Temporal and Madera Canyon in Arizona, where he used to play in the water as a boy, have dried up.
“I’m 72, so in my lifetime, that water has disappeared, and it’s going to continue to do so,” Proctor said.
If pumping water out of the mountain for mining operations reduces the amount or deteriorates the quality of groundwater, PARA’s Shafer and other local activists believe there could be disastrous repercussions to the area’s biodiversity.
“It is the availability of that water that is a large reason for the biodiversity hotspot that this is, because the plants and the animals that are here have the water that they need to be here,” Shafer said. “Drying out this mountain will destroy the biodiversity, it will kill the plant life, the animal life. It will horribly impact the people who are here.”
Aaron Mrotek manages the Patagonia-Sonoita Creek Preserve, a Nature Conservancy property. Mrotek said the critical hydrogeology of the Patagonia and Santa Rita mountains attracts domestic and migratory animals alike and provides essential habitats, food sources and rest locations during migration.
“These mountain ranges within the desert contain a ton of water, whether that’s surface water or groundwater, groundwater that comes up in springs and seeps and stuff like that, and in the desert, water is life,” Mrotek said.
In its initial plan of operation, South32 envisioned that the treated water discharged down Harshaw would be reabsorbed in groundwater downstream. Residents objected, and South32 agreed to install two rapid infiltration basins to the mountain aquifer, according to Risner.
Rapid infiltration basins are permeable, earthen ponds used to increase the water supply of an underground aquifer at a faster pace than natural absorption. The technology is intended to refill the aquifer deep beneath the Patagonia Mountains by quickly infiltrating treated water from the mine.
According to the updated mine plan of operation, South32 plans to eventually discharge about two-thirds of its treated groundwater into each of the basin systems that it plans to dig on site. This water would seep back into the Patagonia Mountains’ aquifer from the basins, according to the company.
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The company does not plan to construct these basins until at least 2026, but it is already pumping groundwater out of the mountain and into the stream based on two state-issued permits.
Another way the Hermosa project says it will save water is by filtering the water out of mine wastes, known as tailings, before storing them onsite, according to Risner. Tailings are waste rock with small amounts of metals left behind after the majority of the ore has been extracted. The company intends to clean and reuse the water separated from tailings in mine operations.
“The ability to reuse water as part of dry stack tailings minimizes our impact on freshwater resources, as well as our underground mining method, because it minimizes the amount of water you would use in a surface mine for dust control,” said Risner.
However, when South32 calculates its water savings, it does not include its discharge of up to millions of gallons of groundwater down Harshaw Creek per day in its estimated water usage, according to Risner.
Proctor said he doubts that the company’s basin system will ever fully refill the aquifer.
His concerns stem from a 2020 study from a University of Arizona graduate student that noted the groundwater in the mountains where the mine is located comes from a different source than the groundwater further downstream that supplies Patagonia.
“If they’re going to be pulling water out that far deep down, then the portion above is going to subside and it’s never going to be able to fill back in, you’ll never be able to recharge it,” Proctor said. “The water they’re taking out of there [is] tens of thousands of years old, and that water will take tens of thousands of years to be replaced.”
Groundwater Contamination Concerns
Activists were initially worried about the potential for the water discharged into Harshaw to increase the likelihood of flooding in town.
In 2021, the Town of Patagonia and South32 retained Clear Creek & Associates to conduct an evaluation of the amount of groundwater the mine intends to discharge into Harshaw Creek. The study found that flooding was not a big risk, but projected that the discharged water would filter into the groundwater beneath Harshaw, raising the groundwater level as high as 4.5 feet after five years of the additional flow.
With some concerns over flooding alleviated, activists now have unanswered questions about how the discharge may affect the quality of Patagonia’s drinking water.
Patagonia’s small population is fully dependent on groundwater for its consumable water. According to the state’s 2023 Consumer Confidence Report, Patagonia receives its water from two groundwater wells in the Sonoita Creek watershed. As recently as the 2023 report, the Arizona Department of Environmental Quality rated Patagonia’s water quality as “low risk,” meaning residents should not be concerned about the quality of their drinking water.
While the water the mine discharges would be treated to the Arizona Department of Environmental Quality’s standard, activists expressed concerns that those millions of gallons of water could loosen metals in soils from legacy mining and push already contaminated water into Patagonia’s source of drinking water.
Unlike Alum Gulch, the Arizona Department of Environmental Quality does not consider lower Harshaw Creek an impaired waterway. Despite this, Friends of Sonoita Creek have collected data showing toxic metals and a diminished quality of water in lower Harshaw Creek, closer to the town of Patagonia. Most of the metals found in the water can be attributed to a history of legacy mining operations and tailings left behind, not the current mine.
“It’s supposed to be drinkable when it comes out of the water treatment plant, when they dump it into Harshaw—drinkable,” Proctor said about South32’s plan to discharge groundwater. “So it runs down the stream, and then if there is additional flooding … there’s a good possibility that it’ll pick up extra metals.”
Harshaw Creek babbles over rocks and lush vegetation on May 8. Harshaw, which flows into Sonoita Creek near the town of Patagonia, was home to decades of hard rock mining for gold and silver in the area, according to the U.S. Forest Service. Credit: Esther Frances/Inside Climate News
Friends of Sonoita Creek took three water samples from Harshaw Creek in late January during South32’s initial discharge of water. The organization took samples where Harshaw flows to the end of San Rafael Road, about 5.4 miles away from the town of Patagonia, and was tested by Eurofins Phoenix after the Arizona Department of Environmental Quality delivered it to the lab.
“The pH is high and there are lots of metals,” said Proctor. “Most of the tributaries of the Sonoita Creek watershed have been mined, and so they are all impaired with metals.”
The sample contained high levels of arsenic, boron and manganese. According to various studies and data from the National Institutes of Health, varying levels of arsenic, boron and manganese can all be toxic for human consumption.
Activists like Proctor think their samples show evidence that their fear is well-grounded: As the treated discharge water flows down the creek, the water could pick up toxic metals and carry them toward town.
But Risner told Inside Climate News that South32’s studies and modeling of the watershed show that the treated water discharged into Harshaw will not push metals into the town’s source of drinking water.
“We’ve done several years of hydrogeologic modeling … modeling the aquifer, modeling the discharge … over that period of time we’ve done the work to understand the transport mechanisms that could occur over that time, and those studies are showing that we don’t see that [contamination] occurring,” said Risner.
None of the studies or models Risner referred to have been made public by South32, and conservationists in the area are not convinced by those claims. From many activists’ perspective, even if South32’s studies and modeling show no risk of contamination, they don’t want to take a chance with their drinking water and their health.
“When we put 6 million gallons of water down Harshaw Creek, over here at Flux [Canyon] or Alum [Gulch] … it’s going to mobilize whatever minerals are there, and there’s no testing that needs to be done. There’s a lot of old mining here,” Schwartz said. “And so, is it going to activate some old acid mining? We don’t know, and so there’s just so many unknowns.”
While South32 has not made its models and studies publicly available, the company published data collected on springs and seeps around the mine. Through years of sampling water, South32 found amounts of lead in Harshaw Creek that exceed a healthy limit downstream from where the mine will be discharging water.
One of the conclusions from a University of Arizona study showed that Harshaw Creek and its tributaries “appear” to partially recharge Patagonia’s groundwater, though the study said further research was needed to be conclusive.
According to its operating permits, South32 is not legally responsible for the quality of the water after it has been cleaned by its water treatment plant and left the mine’s discharge point into Harshaw Creek.
The town of Patagonia does not have a water treatment facility with the ability to clean their drinking water of any metals that could harm residents’ health, according to Juan Urias, the supervisor of Patagonia’s water department.
Patagonia Area Resource Alliance and Friends of Sonoita Creek plan to continue their work to hold South32 accountable for as long as it takes.
“This is very much a David-versus-Goliath situation. I always remind people, though, don’t forget who won that one, and we are determined to get this as mitigated as we possibly can,” PARA’s Shafer said. “If you’re going to force us to do a mine under federal and state regulations, we intend to mitigate this to the highest level possible in order for this to remain a healthy, biologically diverse ecosystem.”
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