About 70 m3 of gasoline were poured as the result of an intentíonal breakdown of a major pipeline along the Lower Llobregat Valley. The main groundwater aquifer of the Barcelona area was affected by the gasoline that was not held in the thick unsaturated zone. No immediate action was taken since it was assumed that all the leaked gasoline had burned out. After three months some dissolved gasoline was "found in water from supply wells. It seemed that the contaminant plume was expanding towards the main emergency reserve wells. As part of the action undertaken to know the extent oí the problem and to restare the ground and the aquifer, the gasoline plume in the saturated zone was modelled and calibrated with existing data. The model was then used to test the effect of pumping alternatives to try to stop the plume expansion, to clean up the aquifer and to resume normal functioning of affected wells.