EPA Advances State Primacy for Underground Injection Control Class VI Well Programs: Key Updates for Carbon Sequestration Efforts

The U.S. Environmental Protection Agency (EPA) continues to take steps to expand state primacy for the Underground Injection Control (UIC) Class VI well program, established under the Safe Drinking Water Act (SDWA). Class VI wells, added as a distinct category in 2010, are used to inject carbon dioxide into deep rock formations for the purpose of long-term geologic carbon sequestration.

Initially, EPA retained exclusive authority to administer the Class VI program. However, since 2018, the agency has granted states the ability to assume primary enforcement responsibility — referred to as “primacy.” Wyoming became the first state to obtain primacy for Class VI wells in 2018, followed by North Dakota in 2020 and, most recently, Louisiana in 2024. This trend reflects growing federal support for state-led implementation of carbon capture and storage (CCS) infrastructure.

As of May 2025, three additional states — West Virginia, Texas, and Arizona — are in various stages of obtaining or finalizing Class VI primacy. Securing EPA approval could significantly accelerate the permitting process for CCS projects in those states, which to date have moved very slowly through EPA review.

West Virginia’s Successful Transition to Class VI Primacy

In a key regulatory milestone, West Virginia received full EPA approval for Class VI well primacy in February 2025. Following a public comment period and review process, the state’s Department of Environmental Protection can now issue permits for geologic carbon sequestration and ensure compliance within the state for Class VI wells. This decision enables West Virginia to take a leading role in issuing CCS project permits.

Texas Closer to Obtaining Full Primacy for Class VI Wells

Texas is moving forward with its bid to obtain full primacy for all UIC well classes, including Class VI wells. EPA has granted primacy for multiple well classes in Texas, and now the state is working through EPA’s process to obtain approval for Class VI wells. The state’s Railroad Commission (RRC) has been at the forefront of these efforts, as seen by a recent Memorandum of Agreement that the RRC has signed with EPA Region 6 on April 29, 2025. This agreement paves the way for Texas to assume responsibility for Class VI well permitting by laying out the RRC’s proposed implementation of the Class VI program. As the next step, EPA plans to solicit public comments on a proposed rule that would grant Class VI program authority to the RRC.

Arizona Moves Toward Full UIC Primacy for Class VI Wells

Arizona has likewise made significant progress toward obtaining primacy for all UIC well classes, including Class VI wells, under the UIC program. On May 19, 2025, EPA published a proposed rule to approve Arizona’s primacy application. EPA will hold a virtual public hearing on June 25, 2025, and accept comments on its proposal through July 3. Should Arizona’s application be finalized, the state will assume full responsibility for permitting and enforcing all UIC wells, including those used for carbon sequestration. This move represents a critical step for Arizona’s growing CCS industry, positioning the state to manage projects more efficiently.

Impact on CCS Projects and Stakeholders

For stakeholders in the CCS sector, the movement of these states toward primacy is a welcome development. Gaining state-level control over the permitting process for Class VI wells should streamline permitting processes and allow for more tailored regulatory approaches in approved states.

As these states advance through the final stages of the primacy process, companies involved in CCS projects should remain engaged and prepared to navigate the shifting regulatory landscape. The public comment periods for Arizona and Texas provide important opportunities for industry feedback.

This post is as of the posting date stated above. Sidley Austin LLP assumes no duty to update this post or post about any subsequent developments having a bearing on this post.