Stormwater Pond Sediment Loading and Accumulation Analysis Using Continuous Simulation

The permanent pool in stormwater detention facilities is designed for water quality treatment by providing an appropriate storage volume for the settling of suspended solids and particulate matter that is carried in stormwater runoff. Sizing of the permanent pool volume is often based on local regulatory requirements that dictate a prescribed Total Suspended Solids (TSS) removal rate, expressed as a percentage removal on an average annual basis. The volume requirement is typically given as a function of the imperviousness and area of the tributary catchment and it is presumed that a pond that meets or exceeds the required volume will achieve its TSS removal target. Sizing facilities in this manner does not account for site-specific characteristics that affect the actual treatment efficiency of a pond. To overcome the limitations inherent in presumptive design criteria, a modeling and design methodology using SWMM5 was developed to estimate the sediment loading and accumulation rate for a facility in Ontario, Canada.