Client: U.S. Army Corps of Engineers (USACE)
Contract Value: $1,305,000
The former Atlas D Missile Site 4 is a nationally recognized project being monitored by USACE Headquarters, Wyoming congressional representatives, and the Assistant Secretary of the Army. Activities at this former Department of Defense facility resulted in soil vapor and groundwater contaminated with trichloro-ethylene (TCE), and the contaminated groundwater has reached a well field that supplies drinking water to the City of Cheyenne.
RMC personnel worked closely and cooperatively with the USACE, Wyoming Dept. of Environmental Quality (WDEQ), EPA Region 8, City/County of Cheyenne, and the Cheyenne Board of Public Utilities for more than five years on this complex and politically sensitive project. The Remedial Investigation report concluded that the hydrogeologic system at the site was very complex and required additional characterization before the conceptual site model (CSM) could be finalized. Therefore, the primary objectives of the Feasibility Study were to define the complex hydrogeologic flow system over an approximate 20 square-mile area, refine the CSM, and develop remedial options for addressing the chemicals in the media of concern.
Feasibility Study Tasks
- Potential remedial technologies were selected/screened to address VOCs in soil vapor and groundwater at the source areas and groundwater downgradient of the source areas
- Designed/conducted two 48-hour soil vapor extraction (SVE) studies to assess the efficiency of SVE in removing VOCs from the unsaturated zone in source areas 1 and 2
- Based on the short-term test results, conducted a 90-day SVE test at source area 2
- Tests indicated that SVE could not remove enough of the VOCs from the low permeability formations to clean up the source areas
- Drilled/installed 5 nested monitoring wells, each consisting of three wells, using sonic drilling
- Collected continuous rock cores to evaluate horizontal and vertical extent of volatile organic compounds (VOCs) in the Ogallala aquifer and bedrock and identify potential fracture zones in the bedrock
- Conducted downhole geophysical and hydrophysical logging to estimate aquifer hydraulic properties
- Performed long-term monitoring of water levels and contaminan t concentrations in 40 monitoring, domestic, and municipal supply wells
- Collected discrete groundwater samples in wells that were screened across multiple water- bearing zones using well packer systems