The Client:
U.S. Army Corps of Engineers, Omaha District
The Challenge:
Readiness activities at the former Department of Defense Atlas D Missile Site 4, near Cheyenne, Wyoming, resulted in tricholorethene (TCE) contamination in the soil and groundwater on site and downgradient. The U.S. Army Corps of Engineers (USACE) required environmental expertise to evaluate the nature and extent of contamination in the source area and define the groundwater plume migrating from the source area. The plume had reached the well field that supplies drinking water to the City of Cheyenne, and the USACE has been treating the water at the well field before distribution.
The Approach:
Nakupuna Companies staff (formerly with RMC Consultants, Inc.) have been working with the USACE, Omaha District, at Site 4 for more than 15 years to evaluate the complex site geology and hydrogeology, define the nature and extent of contamination in soil and water, and evaluate remediation technologies. Our staff performed an initial Focused Feasibility Study as well as follow-on investigations, long-term monitoring of more than 200 wells potentially affected by the plume, and community relations support. We designed and recently completed an extensive area-wide Remedial Investigation covering 92 square miles. Our work also involved installing nested monitoring well clusters at 15 locations to monitor three water-bearing zones, as well as conducting surface seismic and aerial electromagnetic surveys to refine the conceptual site model.
The Results:
Our expertise resulted in a greater understanding of the complex hydrogeology of the site, as well as the nature and extent of soil and groundwater contamination in the source area and downgradient groundwater contamination. The information the Nakupuna Companies provided to the USACE allowed them to move forward with evaluating potential remedial alternatives for the site, as well as helped with gaining positive feedback from the local community and the State of Wyoming. Remediation technologies currently being evaluated include injecting oxidants into the fine-grained formation in the source area and a pump-and-treat system for the downgradient groundwater contamination.