Environmental Health - Toxic Substances
Tools to Define Pre-Mining Water-Quality Restoration Targets
Mineral Creek watershed in southwestern Colorado has natural and mining-related sources of contamination. In the background of this photo is a large naturally occurring seep that discharges acidic, metal-rich water to a tributary of Mineral Creek. Natural sources of contamination like this one make it difficult to determine appropriate water-quality standards for cleanup actions. Photo Credit: David A. Nimick, USGS
U.S. Geological Survey scientists and their colleagues have developed a variety of tools to estimate the pre-mining water quality of streams in watersheds with a legacy of past mining activities. The scientists are applying these tools to help land managers faced with defining realistic water-quality restoration targets for watersheds that may have been affected by natural weathering of mineral deposits before mining ever began. Many streams in these watersheds are contaminated by both natural and mining-related sources of toxic metals and acidity. The lack of historic information on pre-mining water quality and the current contributions of contamination from both natural and mining-related sources make it difficult to establish appropriate water-quality standards for cleanup activities.
The scientists have developed and are applying the following set of tools:
Deposit of iron-cemented stream gravel (ferricrete) with embedded wood fragments that can be age dated using radiocarbon to determine the age of the ferricrete deposit. Knowing the age of the ferricretes helps scientists determine if the associated enrichment of metals in streams occurred before or after mining in the watershed started. Photo Credit: David A. Nimick, USGS
Combining the use of these tools brings multiple lines of evidence to defining pre-mining water-quality conditions in streams and increases confidence in the cleanup targets based on these analyses. These tools are being applied to watersheds in Montana and Colorado, where land managers and environmental regulators are developing cleanup standards for remediation activities in historic mining districts.
Kimball, B.A., Runkel, R.L., Wanty, R.B., Philip L. Verplanck, P.L., 2010, Reactive solute-transport simulation of pre-mining metal concentrations in mine-impacted catchments Redwell Basin, Colorado, USA: Chemical Geology, v. 269, p. 124-136, doi:10.1016/j.chemgeo.2009.05.024.
Nimick, D.A., Gurrieri, J.T., and Furniss, G., 2009, An empirical method for estimating instream pre-mining pH and dissolved Cu concentration in catchments with acidic drainage and ferricrete: Applied Geochemistry, v. 24, no. 1, p. 106-119, doi:10.1016/j.apgeochem.2008.11.007.
Verplanck, P.L., Nordstrom, D.K., Bove, D.J., Plumlee, G.S., and Runkel, R.L., 2009, Naturally acidic surface and ground waters draining porphyry-related mineralized areas of the Southern Rocky Mountains, Colorado and New Mexico: Applied Geochemistry, v. 24, no. 2, p. 255-267, doi:10.1016/j.apgeochem.2008.11.014.
Runkel, R.L., 2010, One-Dimensional Transport with Equilibrium Chemistry (OTEQ)--A reactive transport model for streams and rivers: U.S. Geological Survey Techniques and Methods Book 6, Chapter B6, 101 p.
Runkel, R.L., Kimball, B.A., Walton-Day, K., and Verplanck, P.L., 2007, A simulation-based approach for estimating pre-mining water quality--Red Mountain Creek, Colorado: Applied Geochemistry, v. 22, no. 9, p. 1899-1918, doi:10.1016/j.apgeochem.2007.03.054
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