Abstract Remediation of uranium mine overburden and an acidic mine pond at the White King–Lucky Lass mines near Lakeview, Oregon was completed in November 2006. The site was remediated under Superfund due to risk from arsenic and radium-226 in overburden soils. Separate clean-up standards were developed for each mine site for arsenic and radium-226 due to differing ore-body geochemistry. Gamma surveys were used to identify overburden with elevated radium-226 activities and to provide confirmation of visual clean-up of materials. Because arsenic is collocated with radium-226 at the White King mine, gamma surveys reduced the number of arsenic confirmation samples. Secularequilibrium in the uranium-238 decay series was used to determine the extent of leaching of uranium-238 and daughter products from overburden to groundwater. Trilinear geochemical analysis distinguished mineralized groundwater within the ore bodies from regional groundwater and detected any influence from seepage from overburden piles. Remedial actions include neutralization of an acidic mine pond and consolidation of elevated-activity overburden into a pile with a soil/rock cover at White King mine. Ecological toxicity studies determined that neutralization of the pond would provide a benthic community supportive of aquatic wildlife. An overburden pile at the Lucky Lass mine and disturbed areas were covered with clean soil. The remedial actions comply with State of Oregon siting regulations, which required removal of radioactive overburden from the 500-year flood plain. Protection of human health is assured by institutional controls to prevent use of mineralized groundwater and by fencing to prevent site access.

Abstract Modern large-scale gold mining by cyanide leaching of low-grade ore generates a large volume of process fluids. Reduction and disposal of these fluids presents unique challenges. Leaching solutions, tailings dewatering, and even postmining pit lakes must be managed both in the immediate short term and over decades or longer. Methods for reducing influx to these sources with covers and capillary breaks as well as attenuating, reducing, and disposing of them via above and subsurface land application, evaporation, and vegetation, both xeric and in engineered wetlands, among other techniques, are an evolving art still requiring an adequate base of data and observable experience. Predictive modeling of fluid volume and behavior has proved very inaccurate over both shorter and longer time intervals. Climatic extremes and intensity of precipitation events compound the problem in arid areas. Ecological risk assessment is used to estimate exposure to contaminants of concern. Experience has demonstrated the inadequacy of predictions about process fluid management postclosure, and the need for comprehensive fluids bonding both for short-term contingencies such as bankruptcy and for long-term effluent disposal maintenance and monitoring.