The most typical well for storm water drainage is the Class V injection well. They are used to inject non-hazardous fluids underground. Most Class V wells are used to dispose of wastes into or above underground sources of drinking water and can pose a threat to ground water quality, if not managed properly.
"Most Class V wells are shallow disposal systems that depend on gravity to drain fluids directly in the ground. There are over 20 well subtypes that fall into the Class V category and these wells are used by individuals and businesses to inject a variety of non-hazardous fluids underground. EPA estimates that there are more than 650,000 Class V wells in operation nationwide. Most of these Class V wells are unsophisticated shallow disposal systems that include storm water drainage wells, cesspools, and septic system leach fields. However, the Class V well category also includes more complex wells that are typically deeper and often used at commercial or industrial facilities.
Other more sophisticated Class V well types could include aquifer storage and recovery wells or geothermal electric power wells that are used to inject geothermal fluids extracted from subsurface hydrothermal systems. Complex Class V wells also include wells that are used to inject carbon dioxide (CO2) for long-term geologic sequestration. The CO2 geologic sequestration link below will provide background, and other information, including Class V Experimental Technology Well Guidance for Pilot Geologic Sequestration Projects."
Source: Enivornmental Protection Agency