Challenge. Obtain regulatory approval for using alternate concentration limits (ACLs) for metals and radionuclides to support a more cost-effective closure of mine operations while remaining protective of human health and the environment

Solution. The Smith Ranch-Highland mining and processing plant facility in eastern Wyoming includes the largest uranium mine in the United States. INTERA prepared an ACL application to the United States Nuclear Regulatory Commission (NRC) to amend the groundwater protection standards for arsenic, radium-226, selenium, and uranium. To prepare this first-of-its-kind application for an in-situ recovery (ISR) uranium mine in the United States, we completed detailed characterization of the source and extent of impact , used groundwater and geochemical models to evaluate contaminant transport, assessed exposure (both human health and ecological), and conducted an As Low As Reasonably Achievable (ALARA) demonstration. The ISR extractive method uses site groundwater that is unusable for drinking, agriculture, or livestock because of its proximity to the uranium orebody. Once ISR operations are complete, groundwater will be restored to meet federal and state regulatory standards preventing any contamination to adjacent aquifers. Amending the groundwater protection standards for these metals and radionuclides ensures that restoration is technically achievable, is more consistent with background levels of these constituents in groundwater near a uranium orebody, and is still protective of human health and the environment.