Pyramid Geophysical Services has utilized ground penetrating radar (GPR) to locate and delineate the extents of septic leach fields and septic drain lines at a variety of locations. Typically, these drain field systems are constructed by digging trenches in the ground where perforated drain lines are placed and then covered/surrounded by gravel. The drain line ultimately connects to the septic tank, with material exiting the tank and dispersing itself throughout the leach field via the piping system.
The contrast between the native soil and the gravel/drain lines is typically great enough to result in GPR anomalies that are distinct, discreet and easily identifiable. In the case presented in the figure below, Pyramid was contracted to locate the full extents of the drain field due to a proposed change in the adjacent roadway system. Pyramid utilized a GSSI UtilityScan DF radar unit to map the drainage piping, which was observed to be approximately 2 feet below the ground surface. A series of hand probes had been performed previously that had identified some areas containing gravel; however, the heavily compacted nature of the ground surface across most of the site prevented additional hand probes from being performed, leaving a large degree of uncertainty as to the locations and extents of the drainage lines.
The GPR survey clearly identified the septic drain lines and successfully delineated their locations across the site. The entire survey was performed in under 2 hours.