In order to reduce combined sewer overflows to the Ottawa River and meet environmental requirements, the City of Ottawa commissioned a real time control (RTC) feasibility study and proceeded with its recommendations to upgrade existing regulators and implement a RTC system.
The real time control operation of wastewater collection systems is a relatively new field for the City, and involves the automated control of operations in response to observed and/or predicted conditions. Tetra Tech CSO and its partner Stantec assessed various control strategies and recommended local reactive control as the preferred solution to meet the CSO control objectives at a fraction of the cost of traditional approaches with large storage. RTC implementation was also identified as providing significant benefits with regards to improved system-wide operational control and flow management capabilities under critical event conditions.
The team proceeded with the subsequent regulator upgrades preliminary and detailed design projects, including tender documents. Tetra Tech CSO provided hydraulic assessment, control strategy definition, civil, mechanical, and electrical engineering services, as well as I&C design services that included the selection of monitoring technologies. The implementation of the RTC system involved:
- Upgrades to four regulator chambers to improve access and ensure more efficient flow capture in the IOS;
- Expansion of one gate chamber;
- Modifications to the operational protocols and electrical systems at the raw sewage pumping station (RSPS);
- Integration of a local reactive RTC system at each site and at existing remote SCADA system facilities;
- Maximization of the use of available storage in the West Nepean Collector and the conveyance capacity in the IOS, including the integration of RSPS operation, selected rain gauges, and West Nepean diversion structures;
- Implementation of a flow monitoring program and equipment installation at each of the flow control sites, in order to monitor overflow performance.
The system has been operating successfully since 2010. Tetra Tech CSO provided operator training, post-construction performance evaluation and operational support.
This project has received two awards. The Consulting Engineers of Ontario presented their 2012 Environment Award for the major pollution control project undertaken by the City and its partners, Stantec and Tetra Tech CSO. The City of Ottawa also received an environmental award from the Ontario Public Works Association (OPWA), which recognized the RTC improvements made to the City's combined sewer system.
Average % of CSO reduction: 69%
Capital investment savings: $100M