A science-based approach for selecting legacy mine sites for low-cost remediation efforts

Abstract:

Tens of thousands of abandoned mines and prospects are in mountain watersheds distributed throughout the western United States, some of which have continuing detrimental effects on stream water quality. Currently, prioritization of these sites for receiving the limited funds available for remediation is often based largely on geopolitical factors, with no systematic evaluation of the scientific factors dictating the probability of meeting cleanup goals. The U.S. Geological Survey’s Legacy Mines Lands Screening project is developing a science-based approach for selecting sites where relatively low-cost remediation efforts are most likely to substantially improve water quality and ecosystem health. The first phase of the project involved the construction of a comprehensive GIS model that could be used to screen a region to identify good candidate sites for more focused field study. The GIS compiles both standard regional datasets (all available water chemistry data, geology, etc.) and potentially valuable new USGS coverages, including the USMIN database (containing all known mine features in the western U.S.) and digital maps of hydrothermal alteration type derived from automated analysis of ASTER satellite data. The latter has considerable potential for more effectively evaluating one of the major confounding factors for mine site remediation - natural background metal contamination. The second and ongoing phase involves developing a set of field methods to apply at the candidate sites to efficiently identify metal contaminant levels, discern natural versus mining-related sources, and more thoroughly evaluate the probability of success of relatively simple remedial actions. This approach is currently being applied in central Colorado in cooperation with state and federal agencies, and project results to date will be presented.