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Classes and Numbers of Underground Injection Wells
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In the mid-Atlantic region, Underground Injection Control (UIC) wells are located in all the states: the District of Columbia, Delaware, Maryland, Pennsylvania, Virginia, and West Virginia.
Injection wells are regulated within the framework of five classes of wells, dependent primarily upon the nature of the injected fluid. Generally speaking, injection wells are either deep (discharge below the lowermost underground source of drinking water (USDW) or shallow (discharge into or above the USDW). This distinction is important. Deep wells isolate the injected fluids from USDWs requiring strict adherence to well construction and operating requirements. Shallow wells discharge directly into or above the resource requiring protection demanding a thorough evaluation of the chemical nature of the injected fluid.
There five classes of wells are:
Class I wells are deep wells that inject hazardous and non-hazardous wastes below the lowermost underground source of drinking water.
Class II wells are related to oil and gas, and inject fluids to improve production or to dispose of brine and other related oil and gas fluids.
Class III wells are wells that inject super-heated steam, water, or other fluids into formations in order to extract minerals. The injected fluids are then pumped to the surface and the minerals in solution are extracted. Generally, the fluid is treated and re-injected into the same formation.
Class IV wells inject hazardous or radioactive wastes into or above underground sources of drinking water. These wells are banned under the UIC program because they directly threaten public health.
Class V wells are injection wells that are not included in the other classes. Some Class V wells are technologically advanced wastewater disposal systems used by industry, but most are "low-tech" wells, such as septic systems and cesspools. Generally, they are shallow and depend upon gravity to drain or "inject" liquid waste into the ground above or into underground sources of drinking water. Their simple construction provides little or no protection against possible ground water contamination, so it is important to control what goes into them.
In the mid-Atlantic region, most are Class V wells, as shown in the table below.
