A new 1.5-kilometre elevated guideway will be part of the Eglinton Crosstown West Extension, which will extend the Eglinton Crosstown LRT another 9.2 kilometres farther west and bring much needed rapid transit to Etobicoke and Mississauga.  

As part of the guideway’s construction, we’re designing a bridge across the Humber River. Given the area’s sensitive ecosystem, we’ve got a plan to build it that minimizes impacts on the river and its surroundings.  

A delicate balance

To build a bridge over water, a typical construction method would be to sink supporting columns called piers deep into the ground under the lake or river bottom. Doing so in the Humber could disrupt the river’s natural flow, leading to erosion and sedimentation. This could damage the ecosystem and create flood risks downstream.  

To avoid this, Metrolinx is building what’s called a cantilever bridge construction. This involves anchoring the bridge on either side of the river, using strong supports that remove the need to drill into the river and its banks. In fact, the piers anchoring the bridge will be set back from the banks by 10 to 12 metres. In the case of the Eglinton Crosstown West Extension, the piers will need to be 17 metres high and measure 2.35 metres wide at their maximum to support the weight of the bridge. 

The balanced cantilever method

We’ll build the bridge using a technology called a cantilever form traveller. Although our bridge will be much smaller, you may have seen a similar method being used to build the new Gordie Howe International Bridge connecting Windsor and Detroit. (Aecon, the company building the Humber guideway and bridge for the Eglinton Crosstown West Extension, is also building the Gordie Howe bridge.)  

The form traveller uses a mould to pour one deck section at a time. After pouring one, we’ll wait for it to dry, and then move the mould forward to pour the next section, creating a single, continuous deck. Two forms are used, one starting on either end and meeting in the middle, where a final pour will connect them. This means some very precise engineering, using lasers, GPS and other surveying and alignment tools. Although the forms can be adjusted as work progresses, crews accept little room for error when determining the exact dimensions of the final section that connects the two sides of the bridge.  

Using a form traveller saves time, money and disruption, because it eliminates the need to construct a temporary bridge across the river to help build the permanent one. That means we won’t need to install any scaffolding or other structures in the river or its banks, which further minimizes the impact on the ecosystem. 

In the end, residents get the best of both worlds: a key transit connection that will bring 37,500 people and 23,600 more jobs closer to transit, with minimal impact on the environment. That’s a goal even Gordie Howe would be proud of. 

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