This master thesis work is a part of the development of a GIS-based model for simulation of contaminant transport in soils and groundwater, following a discharge of chemicals. The model is to be used togehter with the already developed Environmental Sensitivity Map. The work is done by order of FOI, the Swedish Defence Research AGency, Division of NBC Defence, in Umeå, in cooperation with Umeå municipality (the Rescue Service, the Environmental Office and the Town Planning Office). The purpose is to examine the possibility to integrate the groundwater flow model MODFLOW and the transport model MT3D into a GIS interface, for simulation of a chemical discharge. This examination has led to the development of a software running under Windows, for users within municipalities. The name of the software is SKUM, a Swedish acronym (Simulation of Chemical Discharge with the Environmental Sensitivity Map). The applications is written in Visual Basic and its GIS functionality comes from MapInfo. Further development should focus on the way to implement the chemical source into the models, the choice of development and user environment (programming language and GIS platform), the visualisation and other presentation of the simulation results, and finally the user-friendliness.