Toronto’s Don and Waterfront Trunk Sewers and CSO Control Strategy Class Environmental Assessment Project

Tetra Tech CSO provided a comprehensive systems integration approach and completion of the environmental assessment process. This incorporated the stormwater and CSO control and treatment projects identified in Study Area 1 of the Citywide Wet Weather Flow Master Plan in order to address discharges in the Don River and the Inner Harbour.

The water quality based integrated planning involved the monitoring and modeling of the collection system, the treatment plants, the Don River and the waterfront bodies of water, as well as the evaluation of various treatment options and wet weather flow control measures to balance storage, source control, treatment, and O&M costs.

Tetra Tech CSO, in partnership with the MMM Group, provided engineering services in the following areas:

  • Incorporation, update, and calibration of a detailed 16,000-node hydrological and hydraulic (H&H) model of the study area covering both combined and separated sewer systems using specialized GIS processes and InfoWorks CS;
  • Capacity analysis of the sanitary and combined trunks and interceptors covering both existing and future conditions (25-year horizon);
  • Development and evaluation of system optimization solutions, including the mitigation of I/I induced capacity issues, SSOs and back-ups in the Don Sanitary Trunk Sewer System, the addition of redundancy and flexibility to the operation of the Coxwell Sanitary Trunk Sewer, and immediate and long-term CSO volume and frequency reductions;
  • Development and evaluation of several wet-weather flow scenarios in conjunction with required wastewater treatment options through integrated systems analysis approach, including facility sizing analysis and hydraulic modeling of wet weather flow facilities, a sensitivity analysis taking into consideration climate change, and extensive trade-off and cost-benefit analyses during scenario evaluation phases.


Significant improvement of water quality in the Inner Harbour, allowing for recreational water activities.


Key Contact

Diana Tao

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