Natural versus mining-caused water-quality degradation to tributaries draining Mount Moly, Silverton, Colorado
Citation
Yager, Douglas B, Wright, Winfield G, Mast, M Alisa, Verplanck, Philip L, Bove, Dana J, and Hageman, Philip L, Natural versus mining-caused water-quality degradation to tributaries draining Mount Moly, Silverton, Colorado: .
Summary
Geological, hydrological, and geochemical information synthesized in a Geographic Information System (GIS) for water and rock surrounding South and Middle Forks of Mineral Creek, northwest of Silverton, Colorado, was analyzed to distinguish between the natural and the mining-related sources of metals to surface waters in the watershed. An important natural source of metals to surface water emanates from a porphyry molybdenum deposit south and upslope from the Middle Fork of Mineral Creek. Interaction of surface and ground water with fractured, altered rocks and permeable, Quaternary-age surficial deposits produces downstream water quality that does not meet current State of Colorado water quality standards for metals and pH. GIS site [...]
Summary
Geological, hydrological, and geochemical information synthesized in a Geographic Information System (GIS) for water and rock surrounding South and Middle Forks of Mineral Creek, northwest of Silverton, Colorado, was analyzed to distinguish between the natural and the mining-related sources of metals to surface waters in the watershed. An important natural source of metals to surface water emanates from a porphyry molybdenum deposit south and upslope from the Middle Fork of Mineral Creek. Interaction of surface and ground water with fractured, altered rocks and permeable, Quaternary-age surficial deposits produces downstream water quality that does not meet current State of Colorado water quality standards for metals and pH. GIS site characterization and three-dimensional modeling distinguish surficial deposits as volumetrically substantial, significant sources of naturally occurring metals that strongly influence water quality and complicate ongoing mine-site mitigation efforts. Our findings indicate that regional hydrologic and geologic information needs to be evaluated before realistic water-quality guidelines are established and mitigation recommendations are confidently implemented.
Published in ICARD 2000, Conference on Acid Rock Drainage, 5th, Denver Colo., 2000, Proceedings, in 2000.
