When oil is brought up from beneath the surface of the earth, saltwater is mixed in with the oil. The saltwater must be removed and properly disposed. This is done by placing the saltwater into another type of well called a "Class II injection well" that puts the saltwater back beneath the surface of the earth into an appropriate geologic formation.

In order to protect the environment and our drinking water, it is very important that Class II injection wells be properly constructed and operated. The Division of Oil & Gas requires that anyone who wants to construct and operate a Class II injection well must first meet rigorous technical requirements and obtain a permit for that activity from the Division. This program is called the Underground Injection Control Program ("UIC Program"). The Division of Oil & Gas is authorized by the United States Environmental Protection Agency to implement the UIC Program for Class II injection wells in Illinois.