Underground Injection Control Program

The Underground Injection Control (UIC) regulations mandate the consideration of a variety of measures to assure that injection activities will not endanger underground source of drinking water (USDWs). The program consists of six classes of injection wells. Each well class is based on the type and depth of the injection activity, and the potential for that injection activity to result in endangerment of a underground source of drinking water.

Class I wells are used to inject hazardous and non-hazardous wastes into deep, isolated rock formations.
Class II wells are used exclusively to inject fluids associated with oil and natural gas production.
Class III wells are used to inject fluids to dissolve and extract minerals.
Class IV wells are shallow wells used to inject hazardous or radioactive wastes into or above a geologic formation that contains a USDW.
Class V wells are used to inject non-hazardous fluids underground. Most Class V wells are used to dispose of wastes into or above underground sources of drinking water.
Class VI wells are wells used for injection of carbon dioxide (CO2) into underground subsurface rock formations for long-term storage, or geologic sequestration.

The UIC program may be implemented by the United States Environmental Protection Agency (EPA) or by states, territories, or tribes with EPA-approved primary permitting and enforcement authority. Activities performed by the UIC program include maintaining well inventory, permitting injection wells, performing inspections, and ensuring compliance with permit requirements. When  operators manage wells in a way that does not meet the applicable UIC requirements, the program alerts operators to issues and may assist operators in returning the wells to compliance or take enforcement action.

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