Quantification of mass loading to Strawberry Creek near the Gilt Edge mine, Lawrence County, South Dakota, June 2003

Abstract

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 minerelated 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 associated with 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.

Spatially Detailed Quantification of Metal Loading for Decision Making: Metal Mass Loading to American Fork and Mary Ellen Gulch, Utah

“…The approach has since been applied to meet various objectives. Examples of applications include a study of a heavily mined, hydrothermally altered catchment in Cement Creek, Colorado (Kimball et al 2002), studies to contrast mined and unmined areas along the Red River, New Mexico (Kimball et al 2006a) and Red Mountain Creek, Colorado , and on a much smaller scale, a study to identify particular hydrogeologic connections through shear zones between a stream and mine pit lakes near Strawberry Creek, South Dakota (Kimball et al 2006b). Detailed discussions of the equations used to calculate discharge and load are provided in a companion data report for American Fork and Mary Ellen Gulch (Kimball et al 2009; available at URL: http://pubs.usgs.gov/ds/443/).…”

Impacts of groundwater metal loads from bedrock fractures on water quality of a mountain stream

“…Flows were not measured at SW09 during the May 2001 sampling event. Kimball et al (2006) found that discharge increased in Strawberry Creek from 2.6 to 27.9 l/s in the USGS June 2003 survey. The greatest inflow was near this adit in the area where the downstream fracture intersects the stream.…”

“…These are locations where bedrock fracture zones are near the stream, and may indicate loads associated with these zones. The load from these downstream sources, however, is currently small in comparison to that from the initial mine discharge, and do not appear to have a substantial impact on Strawberry Creek (Kimball et al 2006). The results of the USGS study are generally applicable only to the flows and chemical concentrations observed on the day of the study.…”

“…It does not account for a mixing zone or potential reactive transport in Strawberry Creek that could result in changes in dissolved or bioavailable metals concentrations, especially with greater stream distances. Although the USGS synoptic tracer study during baseflow showed flow and load increases at specific locations, including downstream from the downstream fracture, both the EPA and USGS surveys indicated an overall loss of metals mass with distance along the stream under existing conditions (CDM 2002;Kimball et al 2006). This loss could be due to adsorption of metals onto sediment, organic carbon, colloidal particulates, and benthic material (Runkel et al 1999;Paulson 2001;Tonkin et al 2002;Caruso 2003).…”

“…The first objective was addressed in part by a USGS tracer study conducted in June 2003 (Kimball et al 2006). This study showed that at the time of sampling, approximately 60% of the increase in streamflow between the WTP discharge point and the confluence of Strawberry Creek with Bear Butte Creek was from dispersed, subsurface inflow (i.e., inflow from the alluvial or bedrock aquifers).…”