The US Environmental Protection Agency (EPA) has finalized a rule granting Arizona the authority to oversee all classes of underground injection wells under the Safe Drinking Water Act (SDWA). The decision makes Arizona the fifth state to receive “primacy” for Class VI wells, which are critical for storing carbon dioxide deep underground as part of carbon capture and storage (CCS) projects.
By transferring permitting responsibilities to the Arizona Department of Environmental Quality (ADEQ), the EPA recognizes the state’s capacity to manage its underground water resources while advancing carbon management opportunities and economic growth.
The move also aligns with the agency’s broader initiative to strengthen US energy leadership while safeguarding drinking water supplies.
EPA Administrator Lee Zeldin underscored the importance of efficient permitting, noting that states are well-positioned to balance resource protection with business needs.
“States know their water resources best,” he said, adding that granting Arizona primacy will streamline regulatory processes while encouraging investment.
Class VI Wells: A Cornerstone of Carbon Capture
Among the various well classes under the SDWA, Class VI wells stand out for their role in enabling the permanent underground storage of carbon dioxide.
These wells are designed to inject CO2 into deep geological formations, preventing it from entering the atmosphere and contributing to climate change.
Arizona’s new authority to regulate Class VI wells is particularly significant as the US seeks to scale up carbon capture and storage infrastructure.
Relevant: EPA Proposes To Grant Arizona Authority Over Class VI Injection Wells
With this approval, ADEQ can now directly issue permits for CO2 storage projects, ensuring both regulatory oversight and alignment with local conditions. This shift is expected to attract private sector investment and accelerate the deployment of CCS technologies across the region.
EPA will continue to oversee implementation of the Underground Injection Control program in Arizona and will remain the permitting authority on tribal lands, except for Class II wells on Navajo Nation lands, where primacy has already been established.
By granting Arizona primacy over Class VI wells, the federal government is signaling strong support for states that are prepared to take on a leadership role in advancing carbon storage, a key element of US climate and energy strategy.
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