Scientific Investigations Report 2004-5143
By B.A. Kimball, R.L. Runkel, K. Walton-Day, and B.K. Stover
ONLINE ONLY
Decisions about remediation of mine drainage on the watershed scale require an understanding of metal contributions from all sources to be able to choose the best sites for remediation. A hydrologic framework to study metal loading in the Willow Creek watershed, a tributary to the Rio Grande River, was established by conducting a series of tracer-injection studies. Each study used the tracer-dilution method in conjunction with synoptic sampling to determine the spatial distribution of discharge and concentration. Discharge and concentration data were then used to develop mass-loading curves for the metals of interest. The discharge and load profiles (1) identify the principal sources of load to the streams; (2) demonstrate the scale of unsampled, dispersed subsurface inflows; and (3) estimate the amount of natural attenuation. The greatest source of metal loads was from the Nelson Tunnel on West Willow Creek, which contributed 158 kilograms per day of zinc to the stream. Additional loading from other dispersed, subsurface inflows along West Willow Creek added substantial loads, but these were small in comparison to the loads from the Nelson Tunnel. No significant contributions of metal load from potential sources occurred along East Willow Creek. The lack of measurable loading may be a result of previous remedial actions along that stream. The lower Willow Creek section had relatively small contributions of load compared to what had been contributed upstream. This watershed approach provides a detailed snapshot of metal load for the watershed to support remediation decisions and quantifies processes that affect metal transport.
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Abstract
Introduction
Purpose and Scope
Methods
Approach
Tracer Injections and Stream Discharge
Synoptic Sampling and Analytical Methods
Mass-Loading Analysis
Principal Components Analysis
Evaluation of Metal Loading
West Willow Creek
Discharge
Chemical Characterization of Synoptic Samples
Load Profiles
Principal Locations of Mass Loading
Unsampled Inflow
Attenuation of Load
East Willow Creek
Discharge
Chemical Characterization of Synoptic Samples
Load Profiles
Principal Locations of Mass Loading
Unsampled Inflow
Attenuation of Metals
Lower Willow Creek
Discharge
Chemical Characterization of Synoptic Samples
Load Profiles
Summary—Implications for Remediation
References Cited
Appendix—Results of Chemical Analyses for Synoptic Samples Collected near Creede, Colorado
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