The U.S. Geological Survey, in cooperation with the U.S. Air Force Civil Engineering Center, collected borehole geophysical data and performed simple aquifer tests to estimate the thickness and hydraulic properties of surficial deposits. The purpose of data collection was to create generalized contour maps of Pierre Shale elevation and surficial deposit thickness within and near Ellsworth Air Force Base. Natural gamma and electromagnetic induction (EMI) data were collected to refine or determine surficial deposit thickness at selected wells. Additionally, data from previous geophysical studies and drillers logs were compiled and combined with results from natural gamma and electromagnetic induction data to provide a more spatially complete image of the subsurface. Borehole nuclear magnetic (bNMR) resonance data were collected to estimate hydraulic conductivity and water content of surficial deposits overlying Pierre Shale. Simple aquifer tests using water slugs (slug tests) were performed to estimate hydraulic conductivity of surficial deposits and results were compared to hydraulic conductivity estimates from borehole nuclear magnetic resonance data. The U.S. Geological Survey also tested the usefulness of colloidal borescope flowmeter (CBFM) logging for determining the horizontal flow direction and velocity of groundwater in the study area.