Underground Injection Control Program Revision; Aquifer Exemption Determination for Portions of the Lance Formation Aquifer in Wyoming

The State of Wyoming Department of Environmental Quality (WDEQ) has requested Environmental Protection Agency (EPA) approval of a revision to the State Underground Injection Control (UIC) Program, specifically that EPA approve an aquifer exemption from classification as an underground source of drinking water (USDW) for portions of the Lance Formation within the Powder River Basin in Johnson County, Wyoming. Until August 2000, COGEMA Minerals was mining uranium from the Wasatch Formation under a UIC Class III in-situ leaching permit, issued by WDEQ. A previous Lance Formation aquifer exemption, approved by EPA in the Federal Register on March 26, 1999, allowed COGEMA to inject mining and mineral processing waste fluids from the Wasatch into the Lance Formation through two Class I Non-Hazardous deep injection wells permitted in 1997. COGEMA, after closing its mining operations, is extending its large-scale ground water restoration throughout the entire mined portion of the Wasatch Formation. During the active mining process, the disposal capacity of the two existing Class I wells were adequate for the smaller scale restoration waste stream as COGEMA mined, then closed each Class III well field sequentially. However, now that COGEMA is restoring the entire mine site, large-scale restoration will produce a larger volume of waste fluid. WDEQ issued the final permit to COGEMA for the operation of two additional wells on November 3, 2000. However, COGEMA cannot inject any fluids into these wells until EPA approves this aquifer exemption. Today's approval of this new aquifer exemption will allow COGEMA to use the newly permitted Class I injection wells to inject ground water restoration waste fluids from the Wasatch Formation into the Lance Formation. As a result of this increased disposal capacity, COGEMA will be able to restore the Wasatch ground water more quickly and pump and treat less ground water. The rate of pumping out of the Wasatch will prevent any negative impa