Montreal CSO Planning, Design and Implementation of Integrated Control of City Interceptors

The City of Montreal was one of the pioneers in the implementation of real time control (RTC) in the mid-1990s in order to operate its 36 regulation structures along the 45 km long interception tunnels. In 2000, the City investigated options to improve the RTC system, particularly to mitigate surcharge and overflow conditions due to the length of the interceptors and multiple inflows.

Based on study results, the City opted to evolve its RTC system from a simple local reactive control to a system-wide and centralized decision-making system using Tetra Tech CSO’s innovative intelligent control solution.

The main additions are the use of rainfall forecasting, the improved monitoring of flow conditions, and online model calculations and optimization processes to coordinate the management of all of the flow control structures. The approach consisted of an evolved operation strategy for the better use and maximization of the available conveyance and storage capacities. The new system was implemented completely in 2004 and is now in successful operation.

Tetra Tech CSO's study and implementation project consisted in:

  • Developing and implementing an integrated control system (CIDI) for the interceptors, including a real-time global, optimal and predictive real time control system, and a data and interface manager to be used by operation and supervision personnel;
  • Conducting engineering and supervision activities (construction and commissioning) for the replacement of a limited number of instruments and pieces of equipment;
  • Conducting a preliminary study on intervention solutions, including the facilities required to meet various environmental reject requirements for 68 overflow sites during wet weather.

Since the implementation of the CIDI system, Tetra Tech CSO has been providing the City's system managers with technical assistance, including Csoft® updates and the maintenance and follow-up for the CIDI system. Tetra Tech CSO has also been involved in a new project to integrate improvements into the RTC system as a result of monitoring activities regarding CIDI maintenance and operation since 2006. This project also includes the integration of recent retention and diversion structures into the intelligent RTC system for a total of 39 regulation gate chambers and three retention basins.


Average % of CSO reduction:      21% (volume)    26% (frequency)

Capital investment savings:         $430M


Key Contact

Diana Tao

Director of Business Development
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514-257-2427 Ext: 3306
Toll Free: 877-292-5100