All tunnelling completed for Toronto's Eglinton Crosstown West Extension

Tunnelling has been completed for the Eglinton Crosstown West Extension in Toronto following breakthrough of the final 500 m twin tunnels between Jane Street and Mount Dennis Station.

The latest section connects the western extension directly into Line 5 Eglinton at Mount Dennis and marks the completion of all tunnel excavation for the 9.2 km project. Construction of the final tunnels began in February and was carried out using the sequential excavation method rather than a tunnel boring machine.

With underground excavation now complete, work is continuing on four new underground stations and a 1.5 km elevated guideway as the project moves into its next construction phases.

The final twin tunnels between Jane Street and Mount Dennis were constructed using the sequential excavation method, which divides the tunnel face into smaller sections that are excavated progressively.

As each section is opened, sprayed concrete is applied to the exposed ground to provide immediate support and maintain stability. Progress is typically around 1 m to 2 m per day, considerably slower than a tunnel boring machine but well suited to shorter or geometrically constrained underground sections.

The method also gives engineers greater flexibility to adjust the excavation and support sequence to local ground behaviour. This is especially useful near existing stations, structures or complex interfaces where the tunnel geometry may not justify mobilisation of a large TBM.

The breakthrough at Mount Dennis completes the underground connection into the existing Line 5 Eglinton infrastructure.

The latest tunnels form only a small part of the underground works delivered for the extension. In 2024, twin TBMs named Renny and Rexy completed approximately 6.3 km of parallel tunnels between Renforth Drive and Scarlett Road. The machines spent around two years excavating the western underground section before reaching the point where the future line transitions toward the surface.

The combination of TBM excavation for the long uniform section and sequential excavation for the shorter connection near Mount Dennis illustrates how different tunnelling methods can be used within the same rail project depending on geometry, ground conditions, access and construction constraints.

Although tunnelling is now finished, major civil works remain under way. Excavation has started for underground stations at Martin Grove, Kipling, Islington and Royal York, while construction of the elevated guideway is progressing. Once complete, the Eglinton Crosstown West Extension will add seven new stations to Line 5 Eglinton and extend rapid transit west toward Mississauga. The project is expected to bring improved transit access to around 37,500 additional residents and 23,600 jobs.

Completion of the tunnels removes one of the major underground construction risks from the programme. The focus now shifts toward stations, structures, systems installation and integration of the new infrastructure with the wider Line 5 network.