U.S. EPA Hard Rock Mining 2006 Conference, Tucson, Arizona, November 14-16, 2006 RECONNAISSANCE SAMPLING AND CHARACTERIZATION OF MINE-WASTE MATERIAL Kathleen S. Smith 1 , Philip L. Hageman 2 , Charles A. Ramsey 3 , Thomas R. Wildeman 4 , and James F. Ranville 5 1 U.S. Geological Survey, Box 25046, M.S. 964D, Denver Federal Center, Denver, CO 80225-0046 ksmith@usgs.gov 303-236-5788 2 U.S. Geological Survey, Box 25046, M.S. 964D, Denver Federal Center, Denver, CO 80225-0046 phageman@usgs.gov 303-236-2494 3 EnviroStat, Inc., P.O. Box 636, Fort Collins, CO 80522 chuck@envirostat.org 970- 689-5700 4 Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401 twildema@mines.edu 303-273-3642 5 Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO 80401 jranvill@mines.edu 303-273-3004 Abstract The rapid assessment of potential acid and metal mobility from mine-waste materials is an area of growing need as the effects of inactive mining sites are evaluated and mitigated across the country and globally. We developed a statistically based, cost-effective sampling strategy to provide a foundation for screening and prioritizing mine-waste piles on a regional or watershed scale. The sampling strategy entails collection from each waste pile of a multi-increment sample (consisting of at least 30 increments (i.e., subsamples)) of the less than 2 mm (minus 10 mesh) fraction of surficial material. One waste-pile sample collected using this sampling strategy contains as much information about average properties as do 30 individual grab samples at 1 / 30 of the analytical cost. Issues of heterogeneity and sampling errors are addressed by this sampling strategy. The USGS Field Leach Test (FLT) is a simple and fast (15-minute) leaching procedure for the screening of mine-waste materials and serves as an effective indicator of waste-material geochemistry and leachability due to rainfall and snowmelt runoff. When used in conjunction with the sampling strategy described above, the FLT can be performed easily in the field, can provide on-site pH and electrical conductivity information (for field prioritization), and can furnish adequate samples for desired elemental analyses. This test is based on the premise that the most chemically reactive material in weathered mining waste consists of relatively soluble components in the fine-grained fraction of the mine-waste material. Mineralogical examination of the mine- waste material to determine its influence on acid generation and metal release is an additional important characterization tool. Colleagues at the U.S. Geological Survey and the Colorado School of Mines have developed a simple decision tree (Mining Waste Decision Tree, MWDT) to 1