Low Cost Overflow Monitoring Techniques and Hydraulic Modeling of A Complex Sewer Network

This paper presents a low-cost way of collecting data for sewer overflows, which provided valuable data which was incorporated into a hydrologic and hydraulic model of the sewer system. Rather than monitoring overflow pipes using a traditional level-velocity sensor, a low-cost motion detector was used. This allowed CSO frequency monitoring data to be collected over a multi-year period at many locations at a fraction of the cost of traditional monitoring instrumentation, while still providing critical information: whether an overflow occurred and the overflow duration. The hydrologic and hydraulic model was calibrated using both traditional flow monitoring and CSO frequency monitoring data. The model was then used to assist the City in making decisions by determining which proposed rehabilitation projects and CSO controls could have the greatest impact in maximizing the combined sewage flow receiving treatment, thus addressing overflows and reducing water quality impacts to the receiving waters.