The choice of BMPs in urban stormwater drainage is most often made with a poor understanding of site constraints, and of the possibilities afforded by these techniques. This leads to extra costs and malfunctioning. To reach feasible choices, we have formalised a decision-making process, taking into account multiple criteria and the large number of partners involved in that kind of process. We have then developed a decision-aiding procedure split up into two phases: an elimination phase permits us to exclude solutions which are identified as unworkable according to site considerations and a decision phase which allows the decision makers to compare and at least to choose a scenario built up with feasible solutions. This paper more particularly deals with the first phase. This elimination phase, which is suitable for an expert system type of representation, has been implemented using a software called DELTANOE constructed for operational design issues but also for pedagogic purposes including conception, realisation, maintenance and management recommendations as well as sketches and photo examples. After presenting the context and basic principles of the elimination phase, we present the way the associated tool has been constructed and validated.