oa Using imcomplete geophysical datasets to monitor a conductive groundwater tracer experiment

The tedious and repetative nature of groundwater tracer experiment monitoring using geophysics can result in an incomplete dataset for subsequent interpretation. A fundamental cause is due to the inherent unpredictability of the rate and direction of movement of, and initial geometry of the tracer slug after injection. This problem is inherent to the experiment since if these parameters were accurately known, there would be no need to perform the tracer study. The incompleteness of the geophysical dataset is also directly affected by the balance between collecting enough data to solve the flow problem, and not wanting to collect redundant data due to the high cost of field data acquisition. This paper presents the results of interpreting incomplete geophysical datasets which were obtained to monitor the migration of a conductive saline groundwater tracer through a deltaic sand aquifer in Gray, Maine. In addition to providing a non-intrusive means for monitoring the temporal movement of the conductive tracer, interpretation of these geophysical data has also yielded a more detailed picture of the geologie and hydrogeologic setting explaining observed anisotropy in flow.