Looking for Communal, Low-impact Ways to Manage Stormwater in Mississauga’s Southdown District

The Credit Valley Conservation Foundation (CVC) will partner with the Region of Peel and the City of Mississauga to study the feasibility of a collaborative, decentralized approach to low-impact development (LID) stormwater management in an industrial/commercial neighbourhood in Mississauga’s Southdown district. The project will focus on 13 properties that share an area of 37.4 hectares. Aggregating multiple properties in this way will allow the study to locate LID features where the highest impact is unrestricted by the confines of single properties and public rights of way. The aim is to eliminate at least 60% of total suspended solids from the runoff leaving the study area while reducing peak flow and controlling erosion. The study will evaluate different types of stormwater management design scenarios, looking for the one that best optimizes cost and performance efficiencies in communal systems. The design scenarios will include the following: existing conditions; 100% private; combined private and public; and 100% public. In line with the Region of Peel’s Water Use Efficiency Program and Climate Change Strategy, the study will also target the reduction of potable water use through rainwater harvesting and blue roof design approaches, resulting in more non-potable water becoming available for activities such as washing vehicles and watering lawns. The CVC will also quantify the potential for mitigating sanitary sewer infiltration, with the end goal of reducing wastewater treatment and its associated energy consumption and greenhouse gas emissions. This initiative is directly linked to the City of Mississauga’s Southdown Master Drainage Plan. Innovative aspects: • Multi-property LID designs mean accessing stormwater management where it makes the most sense • Aggregating properties helps overcome the up-front costs of urban stormwater management through economies of scale—multiple properties can share the total project costs (engineering design, construction, maintenance, etc.), making implementation more affordable on a per-property basis, including shared stormwater credits where applicable • Sharing stormwater management among private and public properties may means fewer land acquisition costs for municipalities as well as fewer conflicts with other public utilities Replicability: The study area is typical of many industrial/commercial neighbourhoods around Canada that are dominated by small and medium businesses with largely impervious surface areas and large building footprints. Replicability and lessons learned can be found in the following: • Demonstrating the business and technical case for communal stormwater management • Defining an implementation framework that could lead to the wide scale adoption of public–private partnerships using existing legislation and policy mechanisms, such as Ontario’s Drainage Act (Project description based on original funding application)