Modelling of Stormwater Ingress into Foulwater Sewers

The Sydney Water Board is studying the cost effectiveness of techniques to detect and correct the excessive entry of stormwater into the Board's sewers. This paper describes the theory and application of a simple two storage non-linear model which was developed to measure the ingress before and after inflow infiltration abatement. This model was initially used on data collected from five pilot areas with good results. It was then adopted for application on the estimation of inflow/infiltration in the Board's largest trunk sewer, the South Western Suburbs Ocean Outfall Sewer. The model proved to be both robust and reliable, offering a realistic simulation of an extremely complex process.