An integrated 3D constant offset GPR and resistivity survey on a sealed landfill — Ilhavo, NW Portugal

Owing to their nature landfills are challenging targets for high resolution Near Surface Geophysics.Herein it is described an integrated high resolution geophysical survey over the Ilhavo landfill sealed about a decade ago.The first aim of the survey is to investigate the time evolution of the contamination plume of the landfill since operations stopped and sealing took place.The second, and main objective, is the study of the landfill itself, that is, to carry out a high resolution 3D geophysical survey over it in order to investigate the thickness and effectiveness of the top cover, the thickness and sealing conditions of the landfill bottom and, finally, to investigate its internal structure.To fulfill these objectives an integrated 3D constant offset GPR and resistivity survey was designed. The interpretation of the geophysical data was carried out together with local borehole and hydrogeological information, so that, the ambiguity and uncertainty of the interpretation was reduced considerably and the usefulness of the methods were assessed.