Hydraulic Modeling of a Large Collection System: Challenges Faced Regarding Design Storm and Unexpected Conditions

The Sanitary Sewer Overflow Initiative (SSOI) began to address overflows or unauthorized discharges of untreated or partially treated wastewater from the City's sanitary sewer collection system. In conjunction with regular maintenance and repair, and a recent manhole inventory the City collected updated system flow data and initiated the hydraulic model build of the sanitary sewer collection system. The flow monitoring and hydraulic model were completed for half of the City in Phase 2. Splitting the project into phases minimized data collection delays and allowed for a targeted analysis of the sanitary sewer collection system. The hydraulic model was built using operational data and record drawings provided by the City and calibrated with survey and flow data obtained in the field. The project team is building on the experience gained during Phase 2 and applying solutions in Phase 3 to refine the hydraulic model and improve calibration.