Stantec appointed to design Toronto’s 600 million litres/day treatment facility
The City of Toronto selected Stantec for design and construction administration of its High Rate Treatment Facility at Ashbridges Bay. The planned facility provides primary treatment for excess combined sewage and stormwater flows captured during wet-weather events, with a design rate of 600 million litres/day. It forms part of the Don River and Central Waterfront wet-weather system. The announcement describes a construction-manager-at-risk delivery model and a design and engineering phase, with construction completion scheduled for 2036. Stantec’s appointment is engineering and administration, rather than sole turnkey construction of the entire city program.
- Publish date: 2026-08-19
- Category: EPC Contractors
- Original source: Stantec
- Reading time: 2 min
Official announcement and scope
The City of Toronto selected Stantec for design and construction administration of its High Rate Treatment Facility at Ashbridges Bay. The planned facility provides primary treatment for excess combined sewage and stormwater flows captured during wet-weather events, with a design rate of 600 million litres/day. It forms part of the Don River and Central Waterfront wet-weather system. The announcement describes a construction-manager-at-risk delivery model and a design and engineering phase, with construction completion scheduled for 2036. Stantec’s appointment is engineering and administration, rather than sole turnkey construction of the entire city program.
Engineering interpretation
Wet-weather treatment is an interface problem between storage tunnels, hydraulic controls and the treatment process. An engineering review should examine how intermittent peak flows enter the facility, how solids handling and bypass arrangements operate, and how the receiving water is protected during commissioning. Early construction-manager input can help align constructability, scheduling and cost assumptions with the design. The treatment rate is a hydraulic design measure, not drinking-water production or evidence of continuous operation. Acceptance of the individual facility also remains distinct from performance of the complete tunnel and collection network. The commissioning plan should record these system boundaries explicitly.