Geophysical characterization of an industrial landfill to quantify raw materials and detect possible leakages

Geophysical electrical methods are standard tools to investigate landfills. However, those methods require galvanic contact between electrodes and the ground, impeding their application in landfills covered by a non-permeable liner that does not allow current injection. To overcome this limitation, we propose the use of transient electromagnetic (TEM) soundings as virtual boreholes, resolving for the vertical changes of electrical conductivity, to quantify variations in porosity, saturation, waste composition and fluid electrical conductivity. TEM soundings can be collected in a few minutes and permit us to explore large areas in a few hours. We present investigations in an industrial landfill (ca. 500 m x 200 m and 20 m deep) sealed by a non-permeable liner, where 100 soundings were collected in one day. Our results demonstrate the capability of the TEM method to efficiently delineate the landfill geometry, internal structure, waste composition and the geometry of the aquifer located ca. 20 m below the waste unit. Moreover, our results identified damage in the non-permeable liner below the landfill, which may act as a pathway for the migration of leachate.