In this study, continuous flow rate measurements were collected in storm sewers downstream of two separate Etobicoke Exfiltration Systems (EES) installed in the City of London, in conjunction with rainfall data collected by a rooftop-mounted tipping bucket rain gauge installed within 1 km of the stormwater management system. A rainfall–runoff model for each of the EES units and their associated catchment areas was created using a proprietary version of the U.S. Environmental Protection Agency’s Storm Water Management Model, PCSWMM, to simulate the peak flow and volume reduction benefits provided by the recently implemented Low Impact Development (LID) stormwater retrofit measures. The rainfall data collected by the rain gauge was input into the model, and the continuous flow rate data was utilized to calibrate model parameters over several storm events of varying size. The LID elements within the calibrated model were then removed to derive a comparison of the flow reduction benefits provided by each of the EES units. In addition to demonstrating the as-built field performance of the SWM retrofits, the calibrated PCSWMM model was used to provide an enhanced understanding of LID feature functionality, with the end goal of optimizing the design and performance of future EES installations.
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