Integrating Seismic Reflection and Ground Penetrating Radar Data at the Marine Corps Air Station, Beaufort, South Carolina

Extensive work has been performed at the Marine Corps Air Station (MCAS) in Beaufort South Carolina to characterize the subsurface and generate a groundwater flow model for an assessment of MCAS aquifer vulnerability and contamination potential using various hydrogeological and geophysical techniques such as slug tests, vertical seismic profiling (VSP), borehole geophysics, vertical electrical soundings, and seismic reflection surveys. The goal of the additional research is to integrate the existing seismic reflection data with newly acquired GPR data in order to: (1) demonstrate the effectiveness of the GPR as a tool for site characterization and (2) obtain hydrogeophysical parameters in a heterogeneous environment. The primary focus of the MCAS Beaufort groundwater flow model is to understand the interaction between the unconsolidated clastic Pleistocene sediments and the underlying Eocene Ocala Limestone, which is the primary aquifer. GPR data were collected along the transect of seismic reflection line MCAS-2 which is a total length of approximately 1700 m with a recording length of 500 ms. There are several wells along the profile that were utilized for hydrogeological and geophysical calibration. Preliminary GPR data were collected adjacent to ground water monitor well BFT-2368, using the 50 and 100 MHz frequency antennas, and consisted of three reflection profiles that vary in length from approximately 210 to 240 m. Comparison of the GPR and seismic data illustrate that the two applications complement one another with respect to resolution. Where GPR data contain better detail (more continuous reflectors) in the shallow subsurface, the seismic data contain less detail but deeper reflections. We are using the seismic attributes such as acoustic impedance, and the dielectric properties estimated from the GPR data in order to make assessments on hydrogeological parameters such as porosity and further, hydraulic conductivity.