Underground Injection Control | Colorado Energy & Carbon Management Commission

About

Wells regulated through EPA’s Underground Injection Control (UIC) program are classified based on the type of fluid injected and the depth of the injection zone relative to the deepest Underground Source of Drinking Water (USDW). There are six “classes” of injection wells, with each class subject to specific regulatory requirements:

Class I wells inject hazardous and non-hazardous wastes into deep, isolated rock formations below the lowermost USDW.
Class II wells are used to inject fluids associated with oil and natural gas production.
Class III wells are used for solution mining, whereby fluid is injected to dissolve and extract minerals.
Class IV wells are used to inject hazardous or radioactive waste into or above a formation containing a USDW. They are generally banned but can be used for cleanup actions under RCRA/CERCLA.
Class V wells are used to inject non-hazardous fluids underground.
Class VI wells are used to inject carbon dioxide (CO2) into deep rock formations for permanent storage.

UIC wells are regulated at the federal level unless a state, territory, or tribe is awarded primary enforcement authority (primacy). ECMC currently regulates Class II wells related to oil and gas operations and is in the process of seeking primacy for Class VI wells associated with carbon sequestration. EPA currently regulates the remainder of the classes (I, III, IV, V), and all UIC classes on Indian lands, through its direct implementation program in Region 8.