Abstract Abandoned or inactive mercury mines are found throughout the western United States. Mercury contamination from these mines has migrated into a variety of different media in varying forms. Cleanups and mitigation projects have been undertaken by various agencies and private entities at a number of these mines, although many remain to be addressed. Although each cleanup has similar objectives, such as source control, the methods employed in each area of the site may differ. By having an understanding of mercury and its effects and assessing different methods used at mercury-mine cleanups, future actions can be more effective at addressing the variety of issues posed by mercury contamination at former extraction and processing sites. This paper provides background on mercury, its occurrences, its health effects, and the mercury mining process. Four cleanup sites that utilized different methods for addressing mercury contamination illustrate how different sources at abandoned mercury mill sites may be addressed to mitigate impacts.

Abstract Acidic metal-contaminated drainages are a critical problem facing many areas of the world. Acid rock drainage results when metal sulfide minerals, particularly pyrite, are oxidized by exposure to oxygen and water. The deleterious effects of these drainages on receiving streams are well known. To address this problem, efforts are being made to use biological processes as an innovative, cost-effective means for treating acidic metal-contaminated drainage. Biological sulfate reduction (BSR) technology can be adapted to diverse site conditions and water chemistry. The Lilly mine near the community of Elliston, Montana, illustrates some of the specific conditions that can challenge effective application of BSR technology.

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.