By rosebell
A major tunnelling milestone has been reached on Toronto’s Eglinton Crosstown West Extension with the successful completion of excavation and initial support works for Advance Tunnel 2 between the Jane Portal and Mount Dennis.
The breakthrough follows nearly 18 months of continuous tunnelling operations, with construction teams working around the clock to deliver the eastern underground connection that will ultimately link the new extension with the existing Eglinton Crosstown LRT infrastructure at Mount Dennis.
STRABAG is delivering the Advance Tunnel 2 works, supported by an engineering joint venture comprising Dr. Sauer & Partners and WSP Canada, which is responsible for the design work associated with this technically important section of the project. The breakthrough represents a significant achievement for the combined construction and engineering teams and moves the project into its next phase of delivery.
Unlike the longer western tunnels of the Eglinton Crosstown West Extension, which were excavated using tunnel boring machines, Advance Tunnel 2 has been constructed using the Sequential Excavation Method (SEM). The technique divides the tunnel face into smaller excavation stages, with excavation and ground support undertaken progressively to maintain stability and control ground movement.
The approximately 500 m twin-tunnel section extends from the portal east of Jane Street towards Mount Dennis Station. Excavation began through clayey fill before progressing predominantly through sands, requiring careful management of ground conditions and close monitoring of nearby structures and utilities. During tunnelling, instrumentation was used to provide information on ground behaviour, allowing the contractor and engineering team to review conditions and adapt the excavation and support sequence where required.
Dr. Sauer & Partners has played an important engineering role in the delivery of Advance Tunnel 2, working in joint venture with WSP Canada alongside STRABAG. The specialist tunnelling consultancy’s involvement encompasses the engineering design associated with the underground works, bringing its experience in SEM and mined tunnel construction to one of the final major underground elements of the extension. The company has described the completion of excavation and support as a major milestone achieved through close collaboration between STRABAG and the Dr. Sauer & Partners/WSP engineering joint venture.
STRABAG was awarded the Advance Tunnel 2 contract by Infrastructure Ontario and Metrolinx in February 2024. The C$255 million design-build-finance contract covers the underground connection between the Jane Portal and Mount Dennis as well as the supply of mining and tunnelling equipment, construction of shafts and the portal, modifications at Mount Dennis Station and associated utility and road works.
Advance Tunnel 2 forms part of the wider 9.2 km Eglinton Crosstown West Extension, which will extend the Eglinton Crosstown LRT westwards from Mount Dennis towards Renforth Drive. The programme is being delivered through a series of major contracts covering Advance Tunnel 1, Advance Tunnel 2, the elevated guideway between Scarlett Road and Jane Street, and the stations, rail and systems package.
The main western underground section was delivered under Advance Tunnel 1 by West End Connectors, comprising Aecon, Dragados and Ghella. Two TBMs, Renny and Rexy, excavated the approximately 6 km underground alignment between Renforth Drive and Scarlett Road, completing their drives in 2024. Interestingly, Dr. Sauer & Partners was also involved in that earlier tunnelling package as a design subconsultant, giving the company involvement across both major underground construction stages of the extension.
Between Scarlett Road and Jane Street the route transitions to an approximately 1.5 km elevated guideway crossing the Humber River valley before returning underground for the Advance Tunnel 2 connection into Mount Dennis. When the complete extension enters service, it will add seven new stations and extend rapid transit westwards towards Mississauga, creating a much longer east-west transit corridor across the Greater Toronto Area.
With excavation and support on Advance Tunnel 2 now successfully completed, attention will move to the remaining structural, fit-out and interface works required to integrate the new tunnels with Mount Dennis Station and the wider Eglinton Crosstown West Extension.
