METAL LOADING IN SODA BUTTE CREEK UPSTREAM OF YELLOWSTONE NATIONAL PARK, PARK COUNTY, MONTANA


Gregory K. Boughton¹


Abstract: Acid drainage from historic mining activities affects the water quality of Soda Butte Creek upstream of Yellowstone National Park. Numerous investigations focusing on metals contamination have been conducted in the Soda Butte Creek basin but conclusions on how metals contamination is currently impacting Soda Butte Creek differ greatly. Information needed to identify and quantify the sources of metal loading was missing.

A tracer-dilution study was conducted on an 8,511-meter reach of Soda Butte Creek in August 1999. The test started upstream of the McLaren mine tailings impoundment and mill site and continued downstream to the Yellowstone National Park boundary. Synoptic sampling sites were selected to divide the creek into discrete segments. A lithium bromide tracer was continuously injected into the stream for 24.5 hours. Downstream dilution of the tracer was used to calculate the stream discharge. Stream discharge values, combined with metal concentrations obtained by synoptic sampling, were used to quantify metal loading in each segment of Soda Butte Creek. 

Most of the metal load that entered Soda Butte Creek was contributed by the visible groundwater inflows from the McLaren tailings impoundment and by Republic Creek. The sources of metal loading in Republic Creek merit further investigation.

¹Gregory K. Boughton, Hydrologist, U.S. Geological Survey, Water Resources Division, Cheyenne, WY 82001

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