Measurement of soil water content below a wastewater trench using ground-penetrating radar

Ground-penetrating radar (GPR) was used to measure the distribution of soil water content below a wastewater trench. Two household septic system trenc hes were installed in a sandy soil. Vertical time domain reflectometry (TDR ) probes were installed through the bottom of one of the trenches. The TDR probes were used to measure soil water content for comparison to the GPR da ta. The GPR measurements were performed in zero-offset gather (ZOG) and mul tiple-offset gather (MOG) survey modes with the antennas in horizontal bore holes located on opposite sides and below the wastewater trench. The ZOG su rvey mode gave an estimate of the average water content in the horizontal p lane below the trench at a prescribed interval along the trench. The MOG su rvey mode produced a tomographic image of the distribution of soil water co ntent in the same horizontal plane below the trench. A similar range of val ues of water contents was measured by TDR and GPR methods.