Electrical imaging of tracer migration at the Massachusetts Military Reservation, Cape Cod

Electrical resistivity tomography (ERT) is examined as a method to provide spatially continuous information about aquifer properties through imaging of tracer flow and transport in an unconfined aquifer. Field data were collected at the Massachusetts Military Reservation, Cape Cod, Massachusetts, during the summer of 2002. High resolution images in both space and time of the movement of an electrically conductive sodium-chloride tracer in three dimensions (3-D) help delineate aquifer heterogeneity. Sixty 3-D data sets were collected between four corner-point wells for 20 days following the 9-hour injection. Concentrations were measured at a 15-point multilevel sampler centrally located within the ERT array, at the production well, and at two wells external to the central array.

The tomograms indicate movement of the saline tracer consistent with measured concentration data. The resistivity tomograms serve as an appropriate surrogate for concentration maps that are otherwise impossible to obtain. Under reasonable assumptions, estimates of groundwater.