DETECTION AND MAPPING OF AN LNAPL PLUME USING GPR: A CASE STUDY

Ground penetrating radar was used to delineate a gasoline (LNAPL) plume at the site of a former gasoline station. Monitoring wells indicated the approximate location of the plume and a free product thickness of up to 1.7 m above a water table typically 3-4 m below ground surface. Anomalous GPR responses were detected well above the expected depth of mobile LNAPL. The shallow depths of anomalous responses indicates that a residual or possibly vapour contaminant found in the non-saturated zone produces the characteristic GPR anomaly detected during this survey.