DDJC-Sharpe Defense Distribution Depot: FEMWATER 3D Transport Model of TCE Plume Migration with Natural Attenuation

摘要

PURPOSE: This Coastal and Hydraulics Engineering Technical Note summarizes results from a three-dimensional (3-D) groundwater numerical model of plume migration comparisons between a no-pumping scenario and a proposed pump-and-treat extraction configuration at the Defense Distribution Depot San Joaquin Sharpe (DDJC), in Lathrop, CA. The variably saturated 3-D numerical model FEMWATER was used to predict long-term (30 years beyond 3Q-2002) trichloroethylene (TCE) plume migration with natural attenuation. BACKGROUND: The DDJC-Sharpe army depot is located near Lathrop, CA (Figure 1). It has been active for many years and solvents used in degreasing operations have contaminated the groundwater. To address the contamination problem, the installation operates three pump-and-treat remediation systems, (north, central, and south shown in Figure 2) to contain the TCE plumes and to treat the contaminated groundwater. In 1997, the U.S. Army Engineer Research and Development Center (ERDC), Coastal and Hydraulics Laboratory (CHL) was asked by the Huntsville Engineering and Support Center to collaborate in the development of a comprehensive regional groundwater model to make predictions of flow and transport over a wide range of hydrologic conditions. The site contractor responsible for operation and monitoring of the existing pump-and-treat remediation system was URS Corporation, Sacramento, CA. Several scenarios have been investigated, including sitings of new municipal water wells, variations in the surface-water drainage and storm-water retention ponds, and guidelines for shutdown and placement of extraction wells to get better contaminant capture for less cost. These model investigations are described in Donnell et al. (2003). FEMWATER MODEL: FEMWATER is a general purpose, unstructured finite element 3-D flow and transport groundwater model for variably saturated mediums.