The objective of this remedial investigation (RI) is to evaluate, as part of the first operable unit for site remediation, the nature and extent of contamination as it relates to the existing public water supply wells operated by the South Adams County Water and Sanitation District. A public health endangerment assessment was conducted to identify compounds which could pose a significant health threat. These investigations have identified ground water as the major migration pathway. The six volatile organic chemicals of primary concern are 11DCE,11DCLE, T12DCE, 111TCE, TRCLE, and TCLEE. A comprehensive investigation analysis was conducted to (1) characterize the hydrogeologic system and (2) quantify the ground water flow and containment transport processes. A three dimensional ground water flow and containment transfer model was developed and calibrated on a preliminary basis to aid in projection of future TRCLE concentrations. This first operable unit RI report is not in intended to address the identity of contributing sources or their relative contributions to the contamination.

Field investigations conducted over the last several years in the area offpost of RMA have examined various media to evaluate the nature and extent of contamination that may have resulted from contaminant migration from Rocky Mountain Arsenal (RMA). Consumptive Use Assessments and Contamination Assessments conducted since 1984 have indicated that ground water was the primary pathway for contaminant migration to the offpost area. Thus, much of the Remedial Investigation (RI) efforts focused on evaluating ground-water pathways and the nature and extent of ground-water contamination. However, surface water, sediments, air, and biota were also examined to evaluate potential contamination in these media and the extent to which these media may be contaminant pathways from RMA to the Offpost Operable Unit.