Exploration of a Buried Building Foundation and a Septic Tank Plume Dispersion Using a Laboratory-fabricated Resistivity Apparatus

In the following study, an electrical resistivity device was built and used in both a laboratory setup and in the field to accurately identify the location of a septic tank and the foundation of Gustavus Adolphus (GA); a building that was burned at Susquehanna University in 1964. The entire apparatus, which costs a fraction of the price of a typical electrical resistivity device, was tested for accuracy in the laboratory prior to its use in the field. The electrical resistivity apparatus consists of a deep-cycle twelve volt battery, an AC to DC inverter and two multimeters to measure the potential and the current intensity from four linear electrodes via a wireless data transmission system. This apparatus was constructed by using basic inexpensive electrical and electronic equipments. The recorded potential and current values were used to calculate the apparent resistivity of different materials adopting the Wenner array for both investigations. Several tests were performed on the tabletop bench, producing consistent results when applied to find small bricks structures with different geometrical arrangement buried under a mixed sand-soil formation. The apparatus was also used to investigate a subsurface salty water plume in the same formation. The horizontal resistivity profile obtained over the vertical small brick wall matched the theoretical apparent resistivity of resistivity versus displacement on a vertical dike in a homogeneous material. In addition, the two-dimensional resistivity profile replicate the salty plume size conformably. Following the success on the small-scale laboratory tabletop bench, the electrical resistivity apparatus was implemented in the field to explore the foundation of GA in one location and the septic tank in another. An array of transects were performed, analyzed and plotted using MATLAB. The three dimensional contours of apparent resistivity depicted exactly the locations of the buried foundation walls, the septic tank and the leaking plume.