Delineation of leachate pathways using electrical methods: case history on a waste plaster landfill in South Korea

A waste plaster landfill site, established as a high-density polyethylene (HDPE) sheet pile surrounded by a slurry wall to isolate possible contaminants within the landfill, was investigated using electric survey techniques. A sheet pile is an effective barrier wall for contaminated leachate containment, unless there are damaged zones within the pile. However, the perfect insulating properties of the pile make it difficult to apply the electrical resistivity method to measure the containment ability of the pile. To locate damaged zones in the sheet pile, which can act as pathways for the contaminated leachate, a potential difference (PD) profiling technique was applied. Through three-dimensional (3D) modelling, PD profiling demonstrated efficacy in locating damaged zones in the sheet pile. Moreover, a 3D survey was conducted to delineate the leakage pathways through the sheet pile, as well as the leachate distribution throughout the landfill. Before the 3D inversion of measured resistivity data, erroneous data caused by the sheet pile were rejected to minimise distortion of the inversion results. 3D inversion showed the sheet pile to be highly resistive overall, especially at shallow depths; however, further inspection via PD profiling identified several areas of damage in the pile. These damaged zones from PD profiling coincided well with the low resistivity zones present near the surface in the 3D inverted image. Furthermore, major leaks were found below the burial depth of the sheet pile. Thus, it was demonstrated the PD profiling and 3D resistivity survey can locate damaged zones in the sheet pile and delineate leakage pathways over the landfill site.