Consideration of Geochemical Issues in Groundwater Restoration at Uranium In-Situ Leach Mining Facilities

Uranium (Nuclear Minerals) / Recovery, Remediation and other Mining-Related Technology

Date posted: 06/02/14

Date Published - January 2007 by J.A. Davis, G.P. Curtis of the U.S. Geological Survey in Menlo Park, CA. Some mining processes use fluids to dissolve (or leach) a mineral from an ore deposit in the ground. Although these in-situ leach mining techniques are considered more environmentally benign then traditional mining and milling practices they still tend to contaminate the groundwater. For this reason, the U.S. Nuclear Regulatory Commission(NRC) requires licensees to ensure that sufficient funds are maintained by the licensee for restoration of the site to initial conditions following cessation of in-situ leach mining operations, that is assuming baseline groundwater survey was conducted prior to mining. Because groundwater restoration represents a substantial portion of these costs, a good estimate of the necessary volume of treatment water is important for approximating the overall cost of decommissioning. This report discusses the in-situ leach mining process, common restoration methods, historical information on in-situ leach mine restoration, and analytical techniques that may be used for estimating the future costs for restoring these sites. Groundwater restoration costs are a significant portion of the overall restoration costs at an in-situ leach mining facility. One method for estimating the groundwater restoration portion of the costs is to select a conservative dollar amount based on experiences with previous decommissioning activities at nonconventional uranium production facilities. A table of estimated costs from previously decommissioned sites is included in the report. A second approach discussed in this report is the use of analogous sites which have already undergone decommissioning. A detailed discussion of the geologic and hydrologic similarities and differences associated with uranium mining sites throughout the United States are also included in this report.