Study to Examine Water-Quality Concerns within Mount Rushmore National Memorial

Science Center Objects

Project Period: 2011-2016
Cooperators: Mount Rushmore National Memorial
Project Chief: Galen Hoogestraat

Executive Summary

Mount Rushmore National Memorial (NMEM) showcases four of the Nation’s most venerated presidents carved in a granitic display. The sculpture is located within 1,280 acres of National Park Service (NPS) land in the Black Hills of South Dakota. A safe drinking-water supply is a vital resource for the park, which accommodates about 2.5 million visitors per year. A preliminary 2011 U.S. Geological Survey (USGS) study of water resources indicated that perchlorate is a compound of concern within the park unit. Scientific research indicates that this contaminant can disrupt the thyroid’s ability to produce hormones needed for normal growth and development; the U.S. Environmental Protection Agency has decided to regulate perchlorate under the Safe Drinking Water Act; however, a national primary drinking water standard has not yet been established as of 2014. A potential source for perchlorate in water resources at Mount Rushmore NMEM is the annual July 4th firework displays during 1998 to 2009. Perchlorate is an oxygenate of choice for fireworks; however, it also is a potential contaminant to the environment through atmospheric fallout from aerial shells, duds, shell fragments, paper debris, and aerial bursts that do not launch from the mortar. The geologic setting in Mount Rushmore NMEM is composed of granites and schists that are conducive to the transport and stability of perchlorate in water resources and has no facultative anaerobic environment for natural attenuation of the compound, which is highly mobilized in groundwater. This study will aid in determining if perchlorate concentrations at sampled sites reduce with time, stay the same, or increase. The data collected from this study are paramount for immediate managerial decisions regarding future Independence Day firework displays at the Monument. In addition, findings from this study may contribute to ongoing national and international research.

 

Objectives

The study by the USGS will assess the occurrence of perchlorate and select associated pyrotechnic metals in groundwater, surface water, and soil samples collected within and adjacent to Mount Rushmore NMEM. The objectives of this study are to (1) investigate the hypothesis that fireworks are the source of perchlorate in groundwater, surface water, and soil; (2) measure concentrations of perchlorate and select metals in groundwater, surface water, and soil samples; (3) compare measured concentrations of perchlorate in water samples to proposed regulatory standards; (4) increase understanding of the aquifer system and groundwater flowpaths by age dating isotopes; and (5) provide relevant data that will aid park managerial decisions regarding the potential threat of contamination of water resources and mitigation, if needed, to offset known impacts.

Figure 1
Map showing major drainage basins and sampling locations within the study area, Mount Rushmore National Memorial.