Runkel, Robert L 1
1 U.S. Geological Survey
Acid Mine Drainage (AMD) from abandoned mine lands contaminates streams and rivers throughout the Colorado Mineral Belt. Much of this contamination has persisted for decades and is likely to continue given the impediments to cleanup that are present at most sites. These impediments include a dearth of funding for cleanup, inflexibility within the Superfund program (Gustavson et al., 2007), the perpetual nature of AMD, antiquated mining laws, mixed and/or uncertain land ownership, and a lack of premining data for the development of cleanup goals. As such, AMD represents a wicked problem that is not amenable to clean, easy solutions (Lund, 2012).
The complexity of the problem is exemplified by three sites in Colorado that have been subject to remedial actions. Red Mountain Creek near Ouray, Colorado, for example, is acidic and metal rich (pH < 3.5) due to natural sources and historical mining activity. Remedial activities conducted to date include removal of mine waste and tailings, regrading and revegetation of mine wastes left in place, and installation of hydrologic controls that direct meteoric water away from contaminated areas. Despite these actions, low-flow water quality is virtually unchanged (Runkel et al., 2005).
Peru Creek, near Keystone, Colorado, is contaminated by the Pennsylvania Mine and other sources within the watershed (Runkel et al., 2013). Drainage from the Pennsylvania Mine has been greatly reduced following the emplacement of two concrete bulkheads in the primary mine tunnel, leading to improvements in water quality downstream. Establishment of a healthy fishery downstream may remain elusive, however, due to natural sources of metals and acidity that emanate from the mineralized bedrock.
The third and final site is the Animas River, near Silverton, Colorado. Extensive mining activities in the Silverton area have contaminated the Animas River for decades (Kimball et al., 2007), and this contamination was brought to national attention by the recent Gold King Mine release. As with Red Mountain Creek, cleanup activities to date have focused primarily on the removal of tailings and erosion controls on mine dumps, actions that are thought to improve water quality during rainfall/runoff events. Despite this progress, draining mine tunnels continue to result in elevated metal concentrations that persist for miles downstream. As such, additional, more expensive efforts may be needed for long-term, year-around improvement in water quality.
Gustavson, K.E., et al., 2007, Superfund and mining megasites: Environ. Sci. Tech., v. 41, p. 2667-2672.
Kimball, B.A., et al., 2007, Quantification of metal loading by tracer injection and synoptic sampling, 1996-2000: USGS Professional Paper 1651, p. 417–495.
Lund, J.R., 2012, Provoking more productive discussion of wicked problems: J. Water Resource Planning Management, v. 138, p. 193-195.
Runkel, R.L., et al., 2005, Geochemistry of Red Mountain Creek, Colorado, under low-flow conditions, August 2002: USGS SIR 2005-5101, 78 p.
Runkel, R.L., et al., 2013, Estimating instream constituent loads using replicate synoptic sampling, Peru Creek, Colorado: J. Hydrology, v. 489, p. 26-41.