Quantification of metal loading in French Gulch, Summit County, Colorado, using a tracer-injection study, July 1996
by
Kimball, B.A., Runkel, R.L., and Gerner, L.J., 1999
U. S. Geological Survey Water-Resources Investigations Report 98-4078
Abstract
Acid mine drainage degrades the water quality and affects the health of aquatic organisms, including fish, in French Gulch, Colorado, a stream that drains to the Blue and Colorado Rivers. Metals in the water originate from drainage of abandoned and inactive mines in the watershed. Mine drainage enters the stream in a complex pattern. Three tracer injections were used to define hydrologic flowpaths from the mines to the stream and to define hydrologic properties of French Gulch. A lithium chloride tracer added to the Oro Mine Shaft of the Wellington-Oro Mine was diluted by the mine pool but did not move from the shaft. This showed that there was no hydrologic connection of the upper mine-shaft water with the downgradient alluvium or with the stream. A sodium bromide tracer added to water in an alluvial well located next to the stream did not cause any detectable bromide concentration in a downgradient alluvial well or in the stream. A sodium chloride tracer added to the stream during a period of 4 days helped indicate those subreaches of French Gulch where the majority of metal loading occurs. There is substantial inflow of metals where the 11-10 and Bullhide Faults cross the stream, and where surface drainage, originating from the Bullhide Fault, enters the stream. The loading analysis indicates that the metals affecting aquatic life in the stream originate from ground and surface water that drain from the mine pool, except during storm runoff when additional sources may contribute metals.
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