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Water: Underground Injection Control

Industrial & Municipal Waste Disposal Wells (Class I)

This page describes Class I injection wells and their uses. It also describes the various types of Class I injection wells, explains how their use protects drinking water resources, and presents the UIC program requirements to ensure the protection of underground sources of drinking water (USDWs).

New Class I Well Animation

Class 1 Well Animation Snapshot
Watch a narrative video that explains the protective measures taken during the construction of a Hazardous Waste Disposal Well.

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What is a Class I well?
Class I wells inject hazardous and non-hazardous wastes into deep, isolated rock formations that are thousands of feet below the lowermost USDW.

Class I Wells
Class 1 Wells

Class I Injection Wells - Isolate hazardous, industrial and municipal wastes through deep injection.

Class I wells are used mainly by the following industries:

  • Petroleum Refining
  • Metal Production
  • Chemical Production
  • Pharmaceutical Production
  • Commercial Disposal
  • Food Production
  • Municipal Wastewater Treatment

There are approximately 550 Class I wells in the United States. The geology of the Gulf Coast and the Great Lakes area is best suited for these types of wells, and most Class I wells are found in these regions.

What are the types of Class I wells?
Class I wells are classified as either hazardous, non-hazardous industrial, municipal, or radioactive depending on the characteristics of the fluid injected. The construction, permitting, operating, and monitoring requirements are more stringent for Class I hazardous wells than for the other types of injection wells.

The four types of Class I wells are:

  1. Hazardous Waste Disposal Wells.
    These wells inject hazardous waste, as defined by the Resource Conservation and Recovery Act ( RCRA). Hazardous waste disposal wells are stringently regulated by the Safe Drinking Water Act and RCRA. Most Class I hazardous wells are located at industrial facilities. Only a few Class I wells are at commercial operations that can accept hazardous waste generated offsite. Class I hazardous waste wells operate in 10 states with the majority in Texas and Louisiana. Approximately 22 percent of Class I wells are hazardous waste disposal wells.
  2. Non-Hazardous Industrial Waste Disposal Wells. These wells, which inject non-hazardous industrial waste, operate in 19 states. The majority of these wells are in Texas, Louisiana, Kansas, and Wyoming. Approximately 48 percent of Class I wells inject non-hazardous industrial waste.
  3. Municipal Wastewater Disposal Wells. These wells are used to inject municipal wastewater in Florida. These injection wells have a large diameter (up to 36 inches) casing and rely on gravity to place fluids underground. Approximately 30 percent of Class I wells are municipal wastewater disposal wells.
  4. Radioactive Waste Disposal Wells. This sub-class of well may be used to inject waste which contains radioactive material below the lowermost formation containing a USDW within one quarter mile of the well bore. There are no known radioactive waste disposal wells operating in the U.S.

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How do Class I wells protect drinking water resources?
Each year, industrial facilities and municipal wastewater treatment plants generate billions of gallons of hazardous and non-hazardous waste.  Class I injection wells provide a safe means to remove these wastes from the surface environment by isolating them deep below the land surface, away from drinking water resources.

Class I injection wells inject far below the lowermost USDW. Injection zones typically range from 1,700 to more than 10,000 feet in depth. The injection zone is separated from USDWs by an impermeable “cap” rock called the confining layer, along with additional layers of permeable and impermeable rock and sediment that separate the injection layer from the USDW.

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What are the requirements for Class I wells?
Every Class I well operates under a permit. Each permit is valid for up to 10 years. Owners and operators of Class I wells must meet specific requirements to obtain a permit. These requirements address the siting, construction, operation, monitoring and testing, reporting and record keeping, and closure of Class I wells.

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Additional Information

  • Visit the Regulations page to read more about the requirements for owners and operators of Class I wells.
  • Visit the Guidance page to read UIC Program guidances.
  • The Reporting Forms page provides links to the forms used by Class I well operators and primacy programs to report and demonstrate that injection operations are protecting USDWs.

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