Identifying and Monitoring Potential Seepage Pathways in Earth Dams using Geoelectrical Timelapse Imaging Technology

Summary Critical infrastructure assets, such as reservoir dams, are prone to failure due to age deterioration and internal erosion processes. Proactive monitoring methods are desirable to study the mechanisms of failure and catch potential faults before they escalate. Geoelectrical monitoring has emerged as a reliable, relatively non-invasive, method to identify and track potential seepage pathways in the subsurface due to its sensitivity to ground moisture content. To this end, we installed a PRIME geoelectrical monitoring instrument on the surface of an earth dam built in the UK in the 18th century. The system operated for five months acquiring a timelapse 3D sequence of the dam’s resistivity profile. The baseline resistivity profile of the dam indicates two distinct lithological areas. Furthermore, continuous timelapse geoelectrical monitoring revealed an area on the dam surface where we observed positive resistivity changes during the drawdown of reservoir levels. Such areas are more susceptible to internal erosion and consequently failure and their early identification represents a great advantage in reducing maintenance and potential damage costs.