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Last month marked a major milestone in the construction of the Yonge Line 1 North Subway Extension (YNSE). On October 26, Metrolinx announced the arrival of the first of two tunnel boring machines (TBMs) that will excavate twin 6.3-kilometre subway tunnels between the launch site near Highway 407 and Finch Station following their assembly.
The announcement follows the completion of the tunnel launch shaft in July, located just south of Langstaff GO Station, east of Yonge Street. With nearly 70,000 cubic metres of soil removed to construct it, the shaft will serve as the launch point for TBMs, which, once lowered underground and assembled piece by piece, will begin their southward tunnelling in the direction of Finch Station. Towards the project’s completion, the shaft will be converted into a tunnel portal for the above-ground section of the extension.
YNSE is a major project to extend Yonge Line 1 northward along Yonge Street, passing from Toronto into York Region, curving east beneath Markham's Royal Orchard neighbourhood, and eventually turning back north and emerging at-grade along the existing Canadian National/GO rail corridor, where it will terminate directly east of the Richmond Hill Centre. It will add five stations at Steeles, Clark, Royal Orchard, Bridge, and High Tech, and add approximately eight kilometres of subway route.
The expansion follows in the footsteps of the Toronto-York Spadina Extension – the first instance of the TTC subway system extending into another regional municipality – completed almost a decade ago. The success of the extension, manifested in enhanced regional connectivity as well as major investments into transit-oriented community projects around new subway stations, prompted renewed advocacy efforts by Markham and Richmond Hill for a similar transit investment.
Planning for the YNSE has undergone several significant challenges. The original proposal of a six-station, fully underground extension running underneath Yonge Street was scaled back in 2021 by the provincial government in an effort to reduce increasing costs.
The updated plan introduced a revised alignment that would shift the northern part of the extension to the surface along the existing Canadian National/GO rail corridor, lowering the costs associated with underground construction. The decision also brought the number of stations down to five, with a further, deeper, tunnel realignment in Royal Orchard approved in order to reduce the amount of residential properties directly above the subway route.
The first TBM, prepared in Germany and decorated with a big red maple leaf at its cutterhead, is currently being lowered into the launch shaft, where its assembly is underway. The equipment and support systems needed for tunnelling are also being loaded, with the arrival of the second TBM expected. This brings the YNSE another step closer to tunnelling.
Along the future subway route, construction preparations are progressing at several locations, with demolitions and site clearings currently underway near the future Steeles, Clark and Royal Orchard stations. The intersection near Yonge Street and John Street is undergoing road widening and piling operations to prepare the site for an emergency exit building. The monitoring equipment has been installed throughout the extension route to track potential construction impacts.
Substantial work remains to be started. While the tunnelling contract has been awarded and the construction is well underway, a separate contract for the building of stations, rail, and systems has not yet been awarded, with a selection expected in 2027. This, coupled with the fact that Metrolinx still has not confirmed an opening date for the start of the TBM excavation, casts uncertainty over the project’s delivery schedule.
UrbanToronto will continue to follow progress on this development, but in the meantime, you can learn more about it from our Database file, linked below. If you'd like, you can join in on the conversation in the associated Project Forum thread or leave a comment in the space provided on this page.
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| Related Companies: | Arcadis, LRi Engineering |
