One-off geophysical detection of chlorinated DNAPL during remediation of an industrial site: a case study

: The remediation of a polluted site relies, as a first stage, on the proper delineation of the contamination sources. In classical investigations, soil and water samples are collected throughout the field. These measurements allow a quantitative characterization of the gathered materials but only provide information about the medium in the vicinity of the points where they were collected. On the other hand, geophysical techniques can provide a quasi-continuous coverage of the investigated field. This paper describes a geophysical survey that was performed on an industrial site impacted by a chlorinated DNAPL. The precise location of the contamination was needed for the treatment of the saturated zone, while the unsaturated zone was remediated by general excavation of the sediments, followed by separate treatment. As this excavation allowed to get closer to the saturated zone, geophysical measurements were conducted at the bottom of the pit. Whereas Electrical Resistivity Tomography measurements only brought little information, Ground Penetrating Radar drew the remediation operations towards an area that preliminary point measurements had not identified as a possible source location.