2D Electrical Imaging of an LNAPL Contamination, Al Amiriyya Fuel Station, Jordan

Abstract

The detection of organic contaminants such as light non-aqueous phase liquid (LNAPL) in the subsurface using geophysical methods, particularly electrical resistivity methods has been the subject of considerable interest in recent years. Their detection is based principally upon the electrical properties of the hydrocarbons. During 2002, direct current resistivity data were collected with the Iris Syscal R2 resistivity instrument at the location of Al Amiriyya fuel station site, Jordan. The objective of this study was to evaluate the resolution of resistivity techniques in detecting and locating anomalies of organic contamination. Resistivity measurements were carried out utilizing the Wenner and dipole-dipole array configurations in order to achieve good vertical and lateral resistivity distributions for the investigated site. The interpretations obtained from 2D-modelling of the field data show a highly conductive region in areas with LNAPL contamination. This explanation was supported by the presence of hydrocarbon sheens floated on the surface of water filling the subsidence feature and by excavation works. Correlation between field results obtained shows that the dipole-dipole array is the most reliable since it showed details over the fuel station site that were poorly indicated by the Wenner array.