Geoelectrical Monitoring at the Reclaimed Landfill of Derveni, Thessaloniki (Greece)

Infiltration of rainwater is of major importance for old waste disposal sites where production of leakage is taking place even after reclamation. In this work we present an ERT monitoring case study in a reclaimed Derveni Landfill. Previous studies in the area showed that important amount of water flows within the waste volume or by lateral groundwater flow or by direct infiltration of rainwater. Maag permeability measurements showed differential behavior of the top soil. Thus, geophysical monitoring of resistivity changes during injection of known conductivity water in high resolution 2D and 3D tomographies has been applied in two selected sites according permeability distribution map. 4D inversion of 2D and 3D data sets showed the flow paths of the injected salty water within the top soil up to the depth of almost one meter. At the same time increase of the resistivity has been observed deeper than one meter that cannot be easily explained. A possible explanation, except the case of disturbed current flow which could lead to artefacts, could be the biogas flow that is interrupted by the water cap of the injection. Both explanation are to be examined as a next step to the integration of the geoelectrical monitoring.