Modeling Performance of Sediment Control Wet Ponds at Two Construction Sites in Ontario, Canada

Abstract

One of the most uncertain hydraulic designs in urban stormwater management concerns sediment control wet ponds as the event mean total suspended sediment concentration that is discharged into a receiving watercourse depends on many complex factors. The primary factors that influence the performance of wet ponds include design storm event volume, sediment load, suspended sediment particle size distribution, pond permanent pool volume, pond drawdown time, pond length-to-width ratio, and number of berms. In this study we developed a new empirical equation using monitoring data from the Greensborough pond (21 events) and the Ballymore pond (16 events), both of which serviced active construction sites in the Greater Toronto Area, and the numerical simulation results using a calibrated hydrodynamic and sediment transport model. The new equation for both study areas predicts outflow event mean total suspended sediment concentration based on pond hydraulic, geometric characteristics, storm event size, and the influent event mean sediment concentration as input parameters. Sensitivity analysis is performed to investigate the effect of each input parameter on the performance of the pond. Based on the results of these case studies, a series of recommended guidelines for pond hydraulic characteristics are proposed. Moreover, this paper proposes a design methodology on pond design sediment control during the construction period to better ensure protection of the aquatic life in the receiving streams.