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Water: Underground Injection Control

Shallow Hazardous and Radioactive Injection Wells (Class IV)


This page describes Class IV wells and how their use protects drinking water resources, and presents the UIC Program requirements that protect underground sources of drinking water (USDWs).


Class IV Wells
Class IV Wells - Prevent ground water contamination by prohibiting the shallow injection of hazardous waste except as part of authorized cleanup activities.

Class IV Wells - Prevent ground water contamination by prohibiting the shallow injection of hazardous waste except as part of authorized cleanup activities.
Visit the Class IV Wells page to read more about these wells.

What is a Class IV well?
Class IV wells are shallow wells used to inject hazardous or radioactive wastes into or above a geologic formation that contains a USDW. In 1984, EPA banned the use of Class IV injection wells for disposal of hazardous or radioactive waste. Now, these wells may only be operated as part of an EPA- or state-authorized ground water clean-up action. There are about 32 waste clean-up sites with Class IV wells in the United States.

What is the difference between Class IV and Class V injection wells?
In general, both shallow Class IV and Class V wells inject fluids into or above the uppermost USDW and may be of similar construction, such as a septic system or dry well. The difference between Class IV and Class V wells is the quality of the fluid being injected. Class V wells may only inject non-hazardous fluids that will not endanger USDWs. However, if a Class V well is misused and receives hazardous waste (as defined by RCRA), the well would be considered a Class IV well and therefore be banned.

How do Class IV wells protect drinking water resources?
The only allowable Class IV wells are used to clean up ground water that has been contaminated with hazardous chemicals. A common method for cleaning contaminated ground water is the "pump and treat" process that operates as follows:

  • Contaminated ground water is brought to the surface
  • The water is treated to remove as much contaminant as possible.
  • The treated water is injected, through a well, back into the same formation.

This process is repeated until contaminant concentrations are reduced to the point where additional removal is no longer possible.

Pump and treat technology can greatly decrease, but may not completely remove, all contaminants in the water. If the water still contains hazardous waste components after treatment, the injection well used would be a Class IV well. Injection wells used in ground water clean-ups where there is no hazardous waste component are Class V aquifer remediation wells.  

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What are the requirements for Class IV wells?

Class IV wells are authorized by rule. Owners or operators must meet the following minimum federal UIC requirements.

  • Obtain approval for the project from:
    • UIC Program (federal or state) and
    • Resource Conservation and Recovery Act (RCRA) or Superfund (Comprehensive Environmental Response, Compensation, and Liability Act [CERCLA]) programs, or state equivalent programs;
  • Ensure that injection does not endanger USDWs; and,
  • Contact the permitting authority and submit UIC inventory information, with injection well-specific information including facility name and location, name and address of legal contact, ownership of facility, nature and type of injection wells, operating status of injection wells, and well class. Inventory information must be submitted prior to construction of the well(s).

EPA Regions and states may require operators of Class IV wells to obtain permits. In addition, some states with UIC primary enforcement authority may have more stringent requirements than the federal regulations and may ban all Class IV wells. In these states, the use of Class IV wells for groundwater remediation would not be allowed.

EPA does not allow for the use of Class IV wells at voluntary clean-up sites. A voluntary clean-up site is any site that is injecting fluid that has a hazardous component, but is not authorized by RCRA/CERCLA or state equivalent programs.

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