Wet weather flows can cause sanitary sewer overflows, combined sewer overflows, and basement flooding in sewer systems with insufficient flow capacities. The City of Winnipeg required input into locating and potentially reducing large sources of infiltration and inflow (I/I) in order to reduce the expansion requirements of the South End Water Pollution Control Center (SEWPCC) and to minimize the corresponding public fund expenditures.
The project involved a 2-year flow monitoring program that included the installation of temporary monitoring at 40 sites in collectors and interceptors (ranging from 450 mm to 1,950 mm), as well as site investigations to augment existing data sources for modeling and analysis.
Tetra Tech (formerly Wardrop and BPR CSO) provided the following engineering services:
- Review and selection of modeling software packages;
- Analysis and verification of the existing collection system model;
- Detailed hydrological and hydraulic model updates and enhancements (XPSWMM to InfoWorks);
- Detailed analysis of I/I characterization and weeping tile flow assessment;
- Calibration of the collection system model using monitoring program data;
- Assessment of the level of service and development of 5-year requirements;
- Definition of the frequency/volume of overflows and basement flood relief issues;
- I/I scenario modeling for the evaluation of the impact of I/I and remediation methods;
- Development of recommendations for the implementation of cost-effective remedial measures to address I/I sources.