LEGAL, HYDROGEOLOGIC AND ENVIRONMENTAL ASPECTS OF THE UNDERGROUND INJECTION CONTROL PROGRAM

Injection of industrial fluids into deep geologic formations is regulated pursuant to the underground injection control (UIC) program authorized by the 1974 SDWA. Federal regulations were established to prevent contamination of underground sources of drinking water (USDW). USDW is defined as “an aquifer or its portion which will yield sufficient quantities of water to supply a public water supply, currently supplies drinking water for humans and contains less than 10,000 mg/l TDS”. Federal and State UIC programs are responsible for regulating construction, operation, permitting, and closure of injection wells, which are classified according to the type of fluid and injection purpose. Regarding deep aquifers, Class I, II and III UIC wells are most important. Class I wells are permitted to dispose of toxic and hazardous industrial waste fluids; Class II wells are permitted for disposal of oil /gas production fluids, storage of hydrocarbons and enhanced recovery of oil or natural gas and Class III wells are permitted for injection for extraction of minerals. As of 2010, there are an estimated 173,000 injection wells in the USA that are permitted as Class I, II or III (US EPA). An applicant for a UIC permit can request an aquifer exemption, which allows for injection into a USDW. Across the Nation thousands of aquifer exemptions have been approved. Hydrogeologic criteria are applied to help assure that the injected fluids are “contained” and do not migrate into a USDW which would result in non-compliance. However, these criteria are quite broad and not easily applicable in complex hydrogeologic settings. Required monitoring associated with UIC wells is limited to monitoring pressures in the injection well; there is rarely an analysis of fate and transport of the injected fluids to help determine if the injected fluid will stay within the permitted zone, which is generally an arbitrary ¼ mile radius from the injection well. With the recent increase in oil and gas production and uranium mining there has been a significant increase in the number of permitted UIC wells. There is an increasing concern regarding the potential for future legacy problems associated with the use of deep aquifers for disposal of waste fluids and the ability to contain the injected fluids in a known portion of receiving formation.