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Underground Injection Control (UIC)

Class V Underground Injection Control Study

The Class V Underground Injection Control Study is a comprehensive look nationwide at 22 types of Class V wells. The 23-volume study summarizes the occurrence and numbers of Class V wells of each type. It also covers what is being injected into these wells and how states regulate them.

The study was required under a 1997 consent decree with the Sierra Club (Sierra Club v. Browner, D.D.C., Civil Action No. 93-2644 NHJ). The consent decree required EPA to evaluate the risk to underground sources of drinking water (USDWs) associated with Class V wells. EPA was also required to determine:

  • If existing federal UIC regulations were adequate to prevent these wells from endangering USDWs
  • If additional federal regulations for any of the well types were warranted
  • How each well type should be regulated

Study Volumes

Each volume of the study addresses a particular well type. The volumes can be accessed below. All files are in Adobe PDF format.

  • Volume 1: Executive Summary for the study.
  • Volume 2: Agricultural Drainage Wells receive agricultural runoff. This well type includes improved sinkholes and abandoned drinking water wells that receive agricultural runoff, wells that recharge aquifers with agricultural tail waters, and wells that drain flood irrigation.
  • Volume 3: Stormwater Drainage Wells are shallow injection wells designed for the disposal of rain water and melted snow. These wells typically drain paved areas such as streets and parking lots as well as roofs. Improved sinkholes and abandoned drinking water wells that receive storm water runoff are considered storm water drainage wells.
  • Volume 4: Carwashes Without Undercarriage Washing or Engine Cleaning use Class V wells to dispose of wash water. These facilities wash only the exterior of vehicles.
  • Volume 5: Large-Capacity Septic Systems dispose of sanitary waste through a septic tank and are used by multiple dwellings, business establishments, communities, and regional business establishments for the injection of wastes. Systems serving single families and non-residential systems serving less than 20 persons are not included.
  • Volume 6: Food Processing Disposal Wells receive wastewater related to the preparation of food and water used to wash food-processing equipment or facilities.
  • Volume 7: Sewage Treatment Effluent Wells are used by privately or publicly owned treatment works (POTWs) to inject treated or untreated domestic sewage through a vertical well or a leachfield.
  • Volume 8: Laundromats Without Dry Cleaning Facilities receive fluids from laundromats where no on-site dry cleaning is performed or where no organic solvents are used for laundering.
  • Volume 9: Spent Brine Return Flow Wells dispose of the spent brine that results from the extraction of minerals, halogens, and other compounds from fluids. These wells are commonly associated with manufacturing facilities that produce specialty chemicals such as boron, bromine, magnesia, or their derivatives.
  • Volume 10: Mine Backfill Wells inject water, sand, mill tailings, or other mining byproducts in order to control subsidence caused by mining, to dispose of mining byproducts, or to fill sections of a mine.
  • Volume 11: Aquaculture Wells dispose of water used for the cultivation of marine and freshwater animals and plants.
  • Volume 12: Solution Mining Wells inject leaching solutions (lixiviants) to remove mineral ores from their original geological settings.
  • Volume 13: In-Situ Fossil Fuel Recovery Wells are used to recover lignite, coal, tar sands, and oil shale. The wells inject water, air, oxygen, solvents, combustibles, or explosives into underground or oil shale beds to free fossil fuels so they can be extracted.
  • Volume 14: Special Drainage Wells include potable water tank overflow, construction dewatering, swimming pool drainage, and mine dewatering wells.
  • Volume 15: Experimental Wells are used to test new technologies. Wells will not be classified as experimental if the technology can be considered under an established well subclass.
  • Volume 16: Aquifer Remediation Wells are used to clean up, treat, or prevent contamination of underground sources of drinking water (USDWs). Treated ground water (pump and treat), bioremediation agents, or other recovery enhancement materials may be injected into the subsurface via Class V wells.
  • Volume 17: Geothermal Electric Power Wells dispose of spent geothermal fluids following the extraction of heat for the production of electricity.
  • Volume 18: Geothermal Direct Heat Return Flow Wells dispose of spent geothermal fluids following the extraction of heat used directly (without conversion to electricity or passage through a heat exchanger) to heat homes, swimming pools, etc.
  • Volume 19: Heat Pump/Air Conditioning Return Flow Wells re-inject ground water that has been passed through a heat exchanger to heat or cool buildings. A heat pump takes thermal energy from the ground water and transfers it to the space being heated. When cooling is required, the heat pump removes heat from a building and transfers it to the ground water.
  • Volume 20: Saline Intrusion Barrier Wells are used to inject fluids to prevent the intrusion of salt water into an aquifer. These wells may have secondary purposes such as aquifer recharge.
  • Volume 21: Aquifer Recharge/Recovery Wells are used to inject fluids to recharge an aquifer. These wells may have secondary purposes such as saline intrusion prevention, subsidence control, or aquifer storage and recovery (ASR).
  • Volume 22: Noncontact Cooling Water Wells are used to inject noncontact cooling water that contains no additives and has not been chemically altered.
  • Volume 23: Subsidence Control Wells are used to control land subsidence caused by ground water withdrawal or over pumping of oil and gas. These wells may have secondary purposes such as aquifer recharge.

Read fact sheets for each of the well types.

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