Water Protection Program fact sheet
Division of Environmental Quality Director: Kyra Moore
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Under the Safe Drinking Water Act of 1974, the U.S. Environmental Protection Agency (EPA) sets minimum federal requirements for injection practices that protect public health by preventing injection wells from contaminating underground sources of drinking water (USDWs). The state of Missouri obtained primacy for its UIC program from the EPA and receives funding from EPA to administer the program. 

Classes of UIC Wells

Class I

Wells used to inject hazardous wastes, industrial non-hazardous liquids, or municipal wastewater beneath the lowermost USDW. Class I injection wells are banned in Missouri. 

Class II

Oil and Gas Injection Wells – These wells are regulated by the department’s Missouri Geological Survey through the State Oil and Gas Council per Chapter 259, RSMo.

Class III

Wells used to inject fluids associated with solution mining of minerals beneath the lowermost USDW. These wells are regulated through the Clean Water Commission under 10 CSR 20-6.090. To date, no permits have been issued in Missouri for this well class.

Class IV

Wells used to inject hazardous or radioactive wastes into or above USDWs. Class IV wells are banned in Missouri. 

Class V

In general, Class V wells inject non-hazardous fluids into or above USDWs and are typically shallow, onsite disposal systems. All Class V wells must be registered with the department's Missouri Geological Survey. Use Class V Well Inventory MO 780-1774 form for all new UIC Class V wells or for existing Class V wells not previously inventoried

  • On-site Waste Water Treatment Systems with Drainfield Disposal – These systems place fluid into the subsurface via a perforated pipe or similar conveyance, excluding single family residences and non-residential systems serving less than 20 persons a day. On-site systems with a discharge of 3,000 gallons per day or more are permitted by the department’s Water Protection Program, while systems with a discharge less than 3,000 gallons per day are permitted by the Department of Health and Senior Services or by county health departments that have adopted by ordinance minimum state standards. 
  • Groundwater Remediation Wells – These wells are used in the cleanup of contaminated sites. Remediation wells involving injection at hazardous waste sites are approved by either the department’s Waste Management or Environmental Remediation program. All other wells are approved by the department's Water Protection Program. Remediation well construction is regulated by the department's Missouri Geological Survey. 
  • Heat Pump and Air Conditioning Return Flow Wells – Groundwater used in an open loop heat pump system can be reinjected through this type of well. Heat pump systems used by more than eight single family residences or rated at greater than 600,000 BTUs per hour are permitted by the department's Water Protection Program. Return well construction is regulated by the department's Missouri Geological Survey.
  • The following Class V well types are permitted by the department's Water Protection Program
    • Mine Backfill Wells – These wells are used to place a mixture of liquid and solid material into subsurface mines.
    • Aquifer Recharge Wells – Aquifer recharge wells are used to maintain hydrostatic pressure around underground storage caverns and have been used to transfer water into the subsurface for storage.
    • Stormwater Drainage Wells – These wells dispose stormwater through infiltration galleries associated with stormwater detention basins.
    • Improved Sinkholes – These are sinkholes that have been improved in some way to control the flow of surface water into the subsurface.

Class VI

Wells used to inject carbon dioxide (CO2) for long-term storage, also known as Geologic Sequestration of CO2. EPA has primacy over these wells. Currently, there are no Class VI wells in Missouri. 

 Database and Additional Information

Nothing in this document may be used to implement any enforcement action or levy any penalty unless promulgated by rule under chapter 536 or authorized by statute.

For more information