The present work presents studies related to the simulation of transport and attenuation processes of gasoline spills in conditions normally encountered in petrol stations. These studies are carried out through the application of numerical methods for the analysis of transport of multicomponents in porous media. Computer programs for 3D analysis of flow and transport of contaminants were used as well as graphics routines for the visualization of results. A detailed study of the programs used was carried out. Validation tests were performed as well as an external implementation of a new routine to simulate a particular chemical reaction (reaction of BTEX with Fenton`s reagent) related to a special remediation technique. As application of the studied procedures, a case related to the gasoline spill in a petrol station located in the city of Rio de Janeiro-RJ was focused. In order to represent as close as possible the gasoline spill the simulation was divided into three stages. The first one, refers to an attempt to reproduce the flow and contamination conditions of BTEX compounds formed in situ until the removal of the underground tanks. The second stage corresponds to a period just after the replacement of the damaged tanks. Finally, the last stage consisted in the injection of oxygen used for bioremediation of the contaminated area. The present work describes the overall methodology used, the obtained results and pertinent comments.