Modelling the retrofit of existing industrial/commercial lands with aggregated and communal green infrastructure LID practices in the Southdown District of Mississauga, Ontario

The Southdown Grid LID project will assess the technical and financial feasibility of implementing communal, integrated water management systems on private property. This will involve aggregating properties together to share communal systems designed to achieve stormwater management and water conservation objectives, and to realize reductions in infiltration and inflow (i.e. stormwater ingress) to the sanitary sewer system.

To evaluate existing conditions and potential SWM retrofit scenarios a PCSWMM model was developed to represent 37.4 ha (92 ac) of I/C lands, consisting of thirteen (13) separate property parcels.

This presentation will provide an overview of the approaches taken:

• Development of a realistic and integrated 1D-2D hydrologic, hydraulic, and water quality model of existing conditions (Scenario 1) within the study area. This model is intended to serve as the baseline scenario with which to optimize retrofit scenarios;
• Development of a parallel PCSWMM hydrologic/hydraulic model to reflect pre-development/ undeveloped conditions of the site;
• Development of Scenario 2 model based on scenario 1 for selected study site, representing a design where the maximum stormwater user fee credit to landowners is achieved per the City of Mississauga’s credit guidelines;
• Identification and quantification of sanitary sewer inflow within the study area, given that the Southdown Study Neighborhood lies within an I/I priority location;
• Evaluating the hydraulic impact on infrastructure performance under future climate change scenarios.

The overarching goal of the aggregated stormwater retrofit study is to support the development of an approach which advances the wide scale adoption of distributed and decentralized stormwater management practices on private property through public/private partnerships.