Using direct-push methods for aquifer characterization in dune-lake environments of the Nebraska Sand Hills

The direct-push (DP) approach for characterization of the shallow unconsolidated sub-surface is a rapidly developing methodology that deploys hydrogeological, geotechnical, and geophysical tools in the sub-surface. It offers significant advantages as compared to techniques using traditional drilling and permanent piezometers, but requires real-time on-site decisions. Selection of the number of tests, sequence, location, and depth makes the planning stage crucial for successful and effective field studies. Whereas the analysis of various DP-based hydrogeological, geotechnical, and geophysical methods is well presented in the literature, recommendations for planning DP field applications are scarce. We illustrate applications of DP-based techniques (electrical conductivity profiling of the aquifer, groundwater sampling, slug testing, and soil core extraction) for evaluation of aquifer-lake interactions in a remote and poorly accessible area of the Nebraska Sand Hills with numerous saline lakes. In addition to the background data on hydrostratigraphy and groundwater salinity, we report an approach to combining and optimizing the DP techniques, including the work sequence, depth limitations, data quantity, and scheduling. The data and insights gained will be useful in designing characterization programs in other sand dune-lake environments.