A monitoring well at the site of a uranium mine operating in a national monument nine miles from the Grand Canyon’s south rim has been detecting rising arsenic levels since 2025. Four times, those arsenic levels exceeded the Arizona well’s permitted alert levels.
Now, the Arizona Department of Environmental Quality (ADEQ) is approving an application from the company, Energy Fuels Resources Inc., to raise both the well’s alert levels for arsenic and the limit of the toxic metal in the aquifer detected at the well by 10 percent in a modification to the mine’s Aquifer Protection Program permit. The approved changes would raise the alert level from 0.04 milligrams per liter (mg/L) to 0.05 mg/L and increase the allowable arsenic concentration from 0.05 mg/L to 0.055 mg/L.
Local tribes and environmentalists say the decision threatens the region’s water quality and the public’s ability to be alerted to groundwater issues at the mine. Independent hydrogeologists who spoke to Inside Climate News say the approval ignores scientific evidence the contamination could spread across the regional aquifer around the Grand Canyon, a possibility that needs more study before a decision is made to raise the permissible levels of arsenic.