The Pointe-aux-Trembles area is located in the eastern part of the City of Montreal and includes sanitary sewer, storm sewer, and combined sewer networks. Lasalle|NHC was contracted by the City to develop a stormwater management master plan for the area as well as a combined sewer overflow (CSO) control plan to ensure compliance with provincial regulations. A large-scale PCSWMM model was calibrated to a major flow measurement campaign and a detailed discretization of subwatersheds enabled site inspections to accurately define directly connected (or effective) impervious area, indirectly connected impervious area, and pervious areas. A 5-year continuous simulation was used to select average years, for which interventions to increase the level of service of the drainage networks and reduce CSOs were defined. The impact of the CSOs on water quality in the Saint Lawrence River was also evaluated using a dispersion model to assess the feasibility of a proposed beach on the waterfront.