Seepage is one of the main reasons for a catastrophic accident in a tailing pond. Damages resulting from internal erosion can lead to expensive remediation. Typical dam safety surveillance consists of visual inspections supported by limited instrumentation. However, internal erosion can become quite advanced before the problem is detected via these means.
Seepage causes water pollution downstream, but it also affects the pond itself increasing the pore water stresses in the saturated zone. Thus, the effective stresses are reduced, which could lead to slope instability. Internal erosion and the development of sinkholes and other piping features is one of the major reasons for embankment dam failures. Geophysical methods have the potential of detecting internal erosion and anomalous seepage at an early stage before the safety and integrity of the dam is at stake.
The recommended geophysical methods in seepage monitoring are mostly SP and ERT. In some cases, Ground Penetrating Radar could also be included for shallow investigations.
Zones of relatively low resistivity within the dam are interpreted to represent eroded and preferential flow pathways. Locations of these zones can be easily defined due to the large contrast in electrical resistivity. Usually, these conductive areas show large negative Self Potential anomalies.