Our client experienced poor surface drainage and subsidence along a roadway in central Pennsylvania. These occurrences made road conditions dangerous. RETTEW/Enviroscan’s geophysics team surveyed the terrain to locate the source of the problem. The unique site conditions of this project required a combination of geophysical techniques to determine the proper solution. We performed four different surveys — microgravity, spontaneous potential, seismic refraction, and ground penetrating radar — that together identified the locations of voids and active water pathways in the ground below.

Our comprehensive approach identified the primary factor causing the sinkholes and flooding: two mass-deficient zones. With this detailed survey data and subsurface view, we recommended installing a larger drain pipe to keep water from infiltrating the area and grouting the existing sinkholes beneath the roadway to remove the places where water can concentrate. Our surveys also showed the identified anomalies appeared to extend beyond the immediate survey area. Subsequently, the local municipality asked RETTEW/Enviroscan to expand our scope and help them prevent other sinkholes in the surrounding area.