The U.S. Environmental Protection Agency’s Office of Ground Water and Drinking Water recently added 2785 aquifer exemption records to its Aquifer Exemptions Map that displays basic information on all known aquifer exemptions in the United States.
The map, which was developed in 2017, is updated on an annual basis by working with states and regions. The most recent update increases the total number of aquifer exemption records in the map from 3356 to 6092.
The majority are in Montana, Wyoming, Colorado, Utah, Texas, and Indian country. Aquifer exemptions also exist in California, which are not shown in the map. California is engaged in a process to digitize existing exemption locations and is also currently reviewing numerous requests for new or expanded aquifer exemptions that they expect to submit to the EPA for review. As this work progresses, the aquifer exemptions in California will be added to the national dataset.
About 97 percent of aquifer exemptions are associated with Class II wells for injection of fluids related to oil and gas production. One-third of aquifer exemptions associated with Class II wells are for enhanced oil or gas recovery (Class IIR) and one-fourth are for disposal of wastewater (Class IID). About one percent of aquifer exemptions are associated with Class III wells, which assist in recovering minerals such as uranium and salts. The remainder are associated with Class I wells used to inject nonhazardous industrial wastes and others.
The depth of the exempted aquifers ranges from hundreds to thousands of feet below ground surface. About four percent of aquifer exemptions are 500 feet or less below the surface. Most depths are between 1000 and 9000 feet deep although a few are more than 10,000 feet deep. In some cases, there is more than one exempted aquifer at the same location, but at different depths and in different bodies of rock.
Click here to access the interactive aquifer exemptions map.