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| Scientific Investigations Report 2006-5006 |
Although remedial actions have taken place at the Gilt Edge mine in the Black Hills of South Dakota, questions remain about a possible hydrologic connection along shear zones between some of the pit lakes at the mine site and Strawberry Creek. Spatially detailed chemical sampling of stream and inflow sites occurred during low-flow conditions in June 2003 as part of a mass-loading study by the U.S. Geological Survey to investigate the possible connection of shear zones to the stream. Stream discharge was calculated by tracer dilution; discharge increased by 25.3 liters per second along the study reach, with 9.73 liters per second coming from three tributaries and the remaining increase coming from small springs and dispersed, subsurface inflow. Chemical differences among inflow samples were distinguished by cluster analysis and indicated that inflows ranged from those unaffected by interaction with mine wastes to those that could have been affected by drainage from pit lakes. Mass loading to the stream from several inflows resulted in distinct chemical changes in stream water along the study reach. Mass loading of the mine-related metals, including cadmium, copper, nickel, and zinc, principally occurred from the discharge from the Gilt Edge mine, and those metals were substantially attenuated downstream. Secondary loadings of metals occurred in the vicinity of the Oro Fino shaft and from two more inflows about 200 m downstream from there. These are both locations where shear zones intersect the stream and may indicate loading associatedwith these zones. Loading downstream from the Oro Fino shaft had a unique chemical character, high in base-metal concentrations, that could indicate an association with water in the pit lakes. The loading from these downstream sources, however, is small in comparison to that from the initial mine discharge and does not appear to have a substantial impact on Strawberry Creek.
This report is contained in the following file:
Abstract
Introduction
Methods and Approach
Tracer Injections and Stream Discharge
Synoptic Sampling and Analytical Methods
Constituent Loads
Cluster Analysis
Field-Scale Experiment
Discharge
Chemical Characterization of Synoptic Samples
Inflows
Stream
Quantification of Mass Loading
Loading of Sulfate and Other Major Constituents
Loading of Iron
Loading of Mine-Related Metals
Summary and Conclusions
References Cited
U.S. Department of the Interior
U.S. Geological Survey
2329 Orton Circle, West Valley City, Ut, 84119
Maintainer: GS-W-UT_Web_Requests@usgs.gov
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