DELINEATION OF SHALLOW HYDROSTRATIGRAPHY USING GROUND PENETRATING RADAR AND ELECTRICAL RESISTIVITY METHODS AT THE P REACTOR AREA, SAVANNAH RIVER SITE, SOUTH CAROLINA

Surface and borehole ground penetrating radar (GPR) as well as electrical resistivity (ER) surveys were conducted at Savanna River Site (SRS), South Carolina, in order to investigate the shallow stratigraphy, hydrogeophysical zonation, and the applicability and performance of the radar and resitivity techniques for such targets. The study site is the P Reactor Area located within the Upper Atlantic Coastal Plain, with clastic sediments ranging from Late Cretaceous to Miocene age. Lithologies consist of sand, clayey sand, and clay with minor amounts of calcareous minerals. The target of this research is the delineation and prediction of migration pathways of a large contaminant plume including trichloroethylene (TCE) that originates from the northwest section of the reactor facility and discharges into the nearby Steel Creek. Here, we present the results from hydrogeophysical characterization using the GPR technique involving the PulseEKKO 100 GPR system with 50 and 100 MHz antennas and the 3D electrical resistivity tomography with the SuperSting R8 IP with 8 channel multi-electrode resistivity and IP imaging system. The simultaneous use of the 50 and 100 MHz antennas and the electrical resistivity method allows us to perform geostatistical analysis of the radar reflection data as a function of frequency to facilitate interpolation and extrapolation of the hydraulic properties such as hydraulic conductivity (K) and porosity of the study area. These data will complement a pseudo 3D seismic survey performed at the site and will fill in the gap between in-situ borehole measurements and seismic scales of resolution.