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Underground Injection Control (UIC)

More Information about Class V Well Types

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Class V wells use injection techniques different from those used by wells in other classes. Although some Class V wells are technologically advanced disposal systems, most are “low-tech” holes in the ground. The typical Class V well is shallow and relies on gravity to drain or inject liquid waste into the ground which is often directly into, or above, an underground source of drinking water (USDW). 

Estimates of the number of Class V wells In the United States

To better understand Class V wells, EPA conducted a study in 1999. The "Class V Underground Injection Control Study" includes national and state estimates on the number, type, and contamination potential of Class V wells in the United States. The study also presents information on where these wells are located, what is injected into them, and how states regulate them. 

In 1999 EPA estimated that more than 686,000 Class V wells within 23 different categories were in operation throughout the U.S. The two largest categories were storm water drainage wells (approximately 248,000) and large-capacity septic systems (approximately 353,000). Combined the two well types made up almost 88 percent of the national total.

In contrast, some categories numbered about 100 or less each, including:

  • Spent brine return flow wells
  • Aquaculture waste disposal wells
  • Geothermal direct heat wells
  • Subsidence control wells

Highlighted Class V wells

Four Class V well types warrant additional discussion. These include: 

  • Motor vehicle waste disposal wells 
  • Large-capacity cesspools

Motor vehicle waste disposal wells and large-capacity septic systems are included because they pose increased threats to USDWs. Additional discussion is also provided for: 

  • Large-capacity septic systems 
  • Stormwater drainage wells

Together, large-capacity septic systems and stormwater drainage wells comprise almost 80 percent of the total number of Class V wells nationwide.

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