Arizona Takes Control Over Injection Wells, A Game Changer for Water Security

On September 10, 2025, the U.S. Environmental Protection Agency (EPA) announced a major regulatory shift, granting the State of Arizona primary enforcement authority, or "primacy," over all classes of underground injection wells within its borders. This decision transfers regulatory power for the federal Underground Injection Control (UIC) program from the EPA to the Arizona Department of Environmental Quality (ADEQ). While UIC primacy is usually focused on Class VI wells for carbon capture and storage (CCS), this ruling is most critical for Arizona’s long-term water management and resource protection.

The UIC program regulates six classes of wells, safeguarding underground drinking water sources by regulating everything from hazardous waste disposal (Class I) to industrial fluids and resource extraction. Unlike other states that have sought primacy for specific classes, Arizona did not previously hold primacy over any UIC well classes before this comprehensive grant. With its new authority, ADEQ will oversee all underground injection, including critical operations like the safe disposal of hazardous waste far below drinking water resources via Class I wells.