Underground Injection Control (UIC)

Class I Industrial and Municipal Waste Disposal Wells

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Use of Class I wells

Class I wells are used to inject hazardous and non-hazardous wastes into deep, confined rock formations.  Class I wells are typically drilled thousands of feet below the lowermost underground source of drinking water (USDW). Approximately 800 operational Class I wells exist in the United States. The geologies of the Gulf Coast and the Great Lakes areas are best suited for these types of wells. Most Class I wells are found in there.

Examples of industries that use Class I wells include:

  • Petroleum refining
  • Metal production
  • Chemical production
  • Pharmaceutical production
  • Commercial disposal
  • Food production
  • Municipal wastewater treatment

Based upon the characteristics of the fluids injected, Class I wells fall into one of four subcategories.

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Hazardous waste disposal wells

Industry injects hazardous waste through Class I wells, as defined by the Resource Conservation and Recovery Act (RCRA). Class I wells are strictly regulated under RCRA and the Safe Drinking Water Act (SDWA). Construction, permitting, operating, and monitoring requirements are more stringent for Class I hazardous waste disposal wells than for other Class I injection well categories.

Approximately 17 percent of Class I wells are hazardous waste disposal wells. Most Class I hazardous waste wells are located at industrial facilities and dispose of waste generated onsite. These wells are operated in 10 states with the majority in Texas and Louisiana. Only a few commercial Class I wells accept hazardous waste generated offsite.  

The Hazardous and Solid Waste Amendments (HSWA) to the RCRA added significant restrictions on the disposal of hazardous waste. Under these amendments, land disposal of hazardous wastes, which includes Class I hazardous waste injection wells, is prohibited unless the:

  • Waste has been treated to become non-hazardous or;
  • Disposer can demonstrate that the waste will remain where it has been placed for as long as it remains hazardous, which has been defined as 10,000 years by regulation.

Learn more about the impact of the RCRA land disposal restrictions on Class I hazardous waste injection wells.

In 2001, EPA published “Class I Underground Injection Control Program: Study of the Risks Associated with Class I Underground Injection Wells.”  The report:

  • Synthesizes existing information on the Class I program 
  • Documents studies of the risks to human health or the environment posed by Class I injection wells

Review EPA's study, Class I Underground Injection Control Program: Study of the Risks Associated with Class I Underground Injection Wells.

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Non-hazardous industrial waste disposal wells

Approximately 53 percent of Class I wells provide for injection of non-hazardous industrial waste.

Disposal of non-hazardous industrial waste occurs at injection wells operating in 19 states. The majority of these wells are in Texas, California, Louisiana, Kansas, and Wyoming.

Municipal wastewater disposal wells

Approximately 30 percent of Class I wells are municipal wastewater disposal wells. These wells are located exclusively in Florida. 

Radioactive waste disposal wells

This sub-class of well may be used to inject waste that contains radioactive material.  No known radioactive waste disposal wells operating in the United States.

Protecting drinking water resources

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

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.

Additional information

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