Rising Antimony Levels at South32 Hermosa Mine: A Call for Transparency and Environmental Accountability

Alarming Water Quality Trends at Hermosa Mine

In the picturesque landscapes of Patagonia, Arizona, a concerning environmental narrative is unfolding. The South32 Hermosa Mine, a point of contention within the community, has reported water quality samples with the highest antimony concentration recorded to date. According to the latest data, a sample from October 31, 2025, showed 5.73 micrograms per liter (µg/L) of antimony, surpassing Arizona's Aquifer Protection Permit (APP) Alert Level of 4.8 µg/L and ominously close to the APP discharge limit of 6 µg/L. This revelation not only triggers a mandatory 30-day study but also highlights a disturbing upward trend in antimony concentrations as discharge flows increase.

Community members and environmental advocates are rightfully alarmed, fearing that the actual antimony concentrations could exceed the regulatory threshold due to the 30–60 days lag in public reporting. The urgency for accurate and timely information is palpable, as the potential risks to public health and the environment loom large.

Public Response and Scientific Analysis

In response to growing concerns, volunteer scientists have meticulously compiled and analyzed publicly reported discharge monitoring results. The resultant data paints a stark picture: higher flow rates, specifically above one million gallons per day, correlate with elevated metal concentrations. While adjustments to the treatment process have shown a reduction in arsenic levels, antimony remains a significant issue. This pattern raises questions about the efficiency of the mine's unique treatment plant, especially given the expected increase in discharge rates as the mine develops further.

The potential for groundwater contamination, particularly in the Harshaw Creek watershed and the Town of Patagonia aquifer, is a pressing concern. The area's reliance on groundwater for drinking and irrigation, coupled with the historical context of mineralized terrain and abandoned mines, underscores the critical need for comprehensive environmental monitoring and regulatory oversight.

Community Calls to Action

At the heart of this environmental challenge is a community's call for transparency, accountability, and proactive measures to safeguard their health and natural resources. Robin Lucky, President of the Calabasas Alliance, emphasizes the importance of water to the community's survival and the crucial role of trust-building during this pivotal moment. The alliance, formed by concerned residents of Santa Cruz County, stands at the forefront of advocating for a thorough analysis of the mine's long-term impact on water quantity and quality.

The implications of South32's operations extend beyond local water sources to the broader ecosystem, with antimony's toxicity posing severe risks to humans and wildlife alike. Chronic exposure to this toxic byproduct through drinking water can lead to a host of health issues, underscoring the urgency of addressing this environmental challenge head-on.

As the narrative unfolds, the role of environmental monitoring by the public becomes increasingly vital. It is through diligent oversight, informed community engagement, and a commitment to environmental stewardship that the residents of Patagonia and Santa Cruz County can navigate the complexities of this situation. Ensuring the integrity of their water sources, and by extension, their health and prosperity, hinges on a collective effort to hold mining operations and regulatory bodies accountable. In the face of such challenges, the community's resolve to protect their environment and demand transparency is both commendable and essential.