Etobicoke Exfiltration System (EES) as a LID Best Management Practice (BMP) was first demonstrated in 1993 and is increasingly being considered as a retrofit measure in a number of Ontario municipalities. The EES significantly reduces both the runoff volume and peak flows, resulting in an increased carrying capacity of the conventional minor drainage systems. To evaluate the EES through modelling, a methodology was developed in SWMM 5.1.012, validated using field measurements, and applied on a case study in the City of Barrie. The primary components of EES include maintenance hole inlets and void space storage of granular (i.e. bedding) material laid beneath the storm sewer. These components were modelled by orifices and a storage unit, respectively, to simulate the flow of captured stormwater into the EES and exfiltration from the stone trench into the surrounding native soil. The model was validated using monitored data from a flow test conducted on the original system installed at Princess Margaret Boulevard in Etobicoke. The resultant model was then applied in a case study of a 26-ha existing residential development serviced with a conventional storm sewer and an outlet to Kidd’s creek watercourse in the City of Barrie. The results indicated a significant reduction of runoff volume (2958 m3) and peak flow (40%) in the minor sewer system for a range of design storm loadings.
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