Three-Dimensional Plume Evaluation to Restore a Sole Source Glacial Aquifer in Western Cape Cod

The Western Cape Cod groundwater system represents one of the most productive and utilized aquifers on the cape and is a primary source of drinking water. Due to the high permeability of glacial sediments that comprise this system, the susceptibility to and cleanup of environmental impacts is a primary concern. A widely studied source of impacts is the Central Impact Area (CIA) located on the Massachusetts Military Reservation (MMR) in Bourne and Sandwich, Massachusetts. In order to evaluate remedial strategies and assess overall impacts for the CIA, a combination of three-dimensional visualization and kriging analysis was performed in conjunction with groundwater fate and transport modeling to evaluate remedial design options. The remedial actions will be implemented to assist in restoring and protecting the downgradient water supply using a groundwater extraction-treatment-reinjection system.

The site-specific modeling framework encompasses a subregional model cut from the Western Cape Cod regional groundwater model developed by the U.S. Geological Survey. Evaluation of several historic groundwater flow models constructed for the CIA within the MMR showed that changes to the model domain size, domain orientation, and application of boundary conditions significantly affected simulated groundwater flow. Also, due to the hydrogeologic aquifer characteristics and resulting groundwater flow regime, mapping horizontal and vertical plume extents, even with the extensive monitoring well network that exists, has presented challenges.

This study focused on (1) evaluating groundwater model configurations to develop a comprehensive tool to design and evaluate the remedial action and to predict future plume characteristics during remediation, and (2) developing a process to better predict and interpolate contaminant plume extents with a greater level of certainty.