Groundwater Modeling for the Southern Sector of A/M Area

Abstract

A plume of TCE contamination in the Southern Sector of A/M Area appears to have resulted from a former release at the A-014 outfall. A numerical groundwater flow and transport modeling analysis is described that addresses this plume, the existing remedial actions, and potential future remedial actions. The numerical flow and transport model is based on an understanding of the site that is formed in part by a recent analysis of hydrostratigraphic, head, and chemical data and by a recent groundwater flow modeling analysis that covers a wider area. The numerical model is calibrated to match observed water level measurements within acceptable criteria. The model is also qualitatively calibrated against the observed/inferred shape of the Southern Sector TCE plume. Though the calibration to the observed TCE plume is not perfect, the model is acceptable for comparing various remedial alternatives. Model simulations indicate that the existing remedial wells, which have been in operation near the A-014 outfall for over ten years, have been effective at removing much of the TCE plume mass. These wells should continue to be effective if operated. The model that is developed and used here can be used in the future to compare remedial alternatives and can be used as a tool to help optimize the operation of various remedial systems. The model may be improved in the future by recalibration following a revised interpretation of the source and/or the TCE plume.