A unique application of Diaphragm Wall to facilitate the excavation of New River Channel on The Port Lands Flood Protection and Enabling Infrastructure Project in Toronto, Ontario-DFI49 Published Technical Paper

DFI49 Published Technical Paper

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The paper describes a unique use of diaphragm walls on Toronto’s Port Lands Flood Protection and Enabling Infrastructure Project, where a new river channel is being excavated through a heavily contaminated former industrial waterfront. The project must both redirect floodwaters safely and prevent legacy contamination from entering the future waterway.<br /><br />A key feature is the west plug wall, located beside Lake Ontario. Unlike a typical retaining wall, it had to perform multiple roles at different construction stages: dock wall for bridge delivery, temporary dam to hold back lake water during dry excavation, structural support for the excavation, permanent hydraulic cutoff wall, and later a removable plug once the river channel is flooded and connected to the lake.<br /><br />The site presented major challenges, including contaminated fill, variable native soils, high groundwater influenced by Lake Ontario, and deep shale bedrock. The original design used secant piles plus a separate sheet-pile deadman system, but the contractor proposed a diaphragm wall alternative. This solution used thicker panels and T-shaped panels for higher stiffness, better watertightness, faster installation, lower cost, and a shorter schedule.<br /><br />Construction used a Hydromill excavation process with slurry support, reinforcement cages, tremie concrete, and overcut panel joints to create a very watertight connection between panels. Automated inclinometer monitoring was also adopted to improve safety and provide real-time movement data.<br /><br />Performance was excellent: the wall experienced minimal deflection, no significant leakage, and maintained integrity through multiple load reversals and years of exposure to harsh weather. The project demonstrates how diaphragm walls can successfully solve complex urban flood protection, excavation support, and environmental containment problems.

Keywords

diaphragm wall

Port Lands Flood Protection

Toronto waterfront

flood protection

contaminated soil

hydromill excavation

hydraulic cutoff wall

temporary dam

watertight excavation

urban infrastructure