Class VI permit applicants must provide extensive information about the local and regional geology and hydrogeology of the proposed site [40 CFR 146.82(a)(2),(3),(5),(6)]. 

The purpose of the UIC Program’s evaluation of this information is to inform a determination that the Class VI well will be sited in an area with a suitable geologic system, consisting of an injection zone with sufficient capacity to receive the carbon dioxide to be injected and a confining zone that is free of transmissive faults or fractures per 40 CFR 146.83. The EPA recommends a two-phase approach to reviewing site characterization information (i.e., a review of the geologic information submitted per 40 CFR 146.82(a) and a comprehensive evaluation of that geologic information to confirm site-suitability, per 40 CFR 146.83), as described in the UIC Program Class VI Well Site Characterization Guidance and outlined below. The purpose of the UIC Program’s review of the geologic information is to verify that the information submitted is accurate and that it provides appropriate and accurate inputs and considerations for AoR delineation modeling, well construction, and planned operation. Figure 4-1 provides an overview of the site characterization review process. 

Source: Environmental Protection Agency. (2018, January). Geologic Sequestration of Carbon Dioxide Underground Injection Control (UIC) Program Class VI Implementation Manual for UIC Program Directors. Page 56. Retrieved from