UIC Injection Well Classes
The Underground Injection Control (UIC) program , which exists to protect underground sources of drinking water in the United States, categorizes injection wells into “classes.” A well’s designation into a particular class depends on several factors, including type of fluid or material, purpose of injection, and proximity to underground drinking water sources.
The 6 Classes of Injection Wells in the United States
According to the EPA, there are six classes of injection wells in the United States. Here’s a quick explanation of each injection well class.
Class I: Both hazardous and non-hazardous waste are injected into confined rock formations through Class I wells. Given the sensitive nature of such material, Class I wells are usually very deep—thousands of feet below the drinking water supply. Treated municipal waste water and industrial waste are injected into Class I wells.
Class II: Brines and other fluids related to oil and gas production are injected via Class II wells. The United States’ strong position in the petroleum industry has contributed to a large number of Class II wells (approximately 180,000 per the EPA). The UIC program further categorizes Class II wells as disposal wells, enhanced recovery wells, and hydrocarbon storage wells.
Class III: Injecting fluids to support mining involves Class III wells. Salt, uranium, copper, and other minerals are commonly extracted from the ground with Class III wells. In fact, the EPA estimates that “80 percent of the uranium extraction in the United States involve the use of Class III injection wells.”
Class IV: Less than a few dozen Class IV injection wells exist in the United States. That’s because they were banned by the EPA in 1984. The UIC program indicates that Class IV wells may “only operate as part of an EPA- or state-authorized ground water clean-up action.”
Class V: According to the UIC Fact Sheet, Class V wells account for approximately 70% of injection wells in the United States. The Class V designation includes all injection wells not included in other classes, including simple stormwater drainage wells. That said, some Class V wells are complex, such as geothermal electric power wells.
Class VI: Wells used to inject carbon dioxide into deep rock formations are Class VI wells. Class VI was established with the EPA’s issuance of a ruling in 2010 (which ultimately became effective in 2011). Gaining approval for and operating a Class VI well is complex, as illustrated by the EPA’s 212-page implementation manual.
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