Concerns over arsenic contamination have surfaced at a uranium mine located less than nine miles from the Grand Canyon's South Rim. A recent study by the Grand Canyon Trust reported that three monitoring wells at the Pinyon Plain mine exhibit average arsenic levels significantly exceeding the U.S. Environmental Protection Agency's (EPA) safe drinking water limit of 10 micrograms per liter. One well showed levels nearly six times higher, while the mining company's own reports indicate arsenic concentrations at the bottom of the mine shaft surpass the safe limit by over 3,000 times.
Since 2016, the Pinyon Plain mine, operated by Energy Fuels Resources Inc., has pumped tens of millions of gallons of underground water from its deep shaft. Scientists suggest this pumping may be exacerbating high arsenic levels by drawing oxygen into an aquifer and releasing naturally occurring arsenic locked in the rocks. This process, they warn, could potentially spread contamination into the Coconino Aquifer, which supplies groundwater to the region, including Havasu Creek, the sole water source for the Havasupai Tribe. Toxic levels reaching springs on the south rim could also impact ecosystems and water sources for park visitors and facilities.
Energy Fuels Resources Inc. has contested these claims, asserting that the high arsenic levels are a natural occurrence in the mineral-rich area and that the pumping simply draws in already arsenic-laden water. Misael Cabrera, the company's senior vice president of environment, safety and sustainability, stated that the company is "assumed to be guilty before proven innocent" despite regulatory approvals and court cases.
Arizona state officials at the Department of Environmental Quality (ADEQ) have accepted the company's explanation, allowing higher arsenic limits in the mine's monitoring wells than typically permitted by health standards. ADEQ maintains its decisions are "data-driven" and based on "extensive site-specific hydrogeological monitoring, updated modeling, and independent testing," concluding that the mine's activities are creating a "hydraulic sink" that draws nearby arsenic-rich groundwater but is kept in a closed system.
However, independent scientists, including hydrologist David Kreamer and retired researcher Brad Esser, have raised doubts about ADEQ's conclusions. Kreamer pointed out that arsenic levels outside the mine are significantly lower than inside, questioning how drawing in lower-concentration water could increase levels within the mine. Esser criticized the state for approving higher arsenic limits without thorough investigation, suggesting a failure in the monitoring and regulatory process.
In 2024, the Havasupai Tribe protested against the Pinyon Plain Mine, voicing concerns that its operations could contaminate their drinking water sources and harm sacred sites. The potential for contamination to reach springs on the Grand Canyon's south rim and Havasu Spring, which feeds Havasu Creek, poses a significant risk to the tribe's water security.