Yonge North Subway Extension
Extending Line 1 subway service nearly 8 km north from Finch Station to Richmond Hill.- Projects & Programs
- Yonge North Subway Extension
- What We're Building
- Tunnel launch shaft and portal
Tunnel launch shaft
The launch shaft will be temporary construction infrastructure that will serve as the starting point for the 6.3-kilometre journey of the future tunnel boring machines (TBMs).
It is a deep, reinforced excavation where the two TBMs will be assembled and lowered into the ground to start tunnelling.
Located south of the future Bridge Station, the launch shaft will allow the TBMs to begin their journey south to Finch Station, where they will be lifted out of the ground and retired once tunnelling is complete.
The shaded area indicates the approximate TBM launch shaft site in Markham, off Langstaff Road.
An aerial view of work at the TBM launch shaft site.
Building the shaft involves installing strong concrete support walls to keep the excavation stable before removing soil in stages. After that, reinforced concrete is poured to form a sturdy slab that will support the TBMs.
An excavator loads a dump truck with soil during work to prepare for excavation.
The launch shaft site will be used to store construction equipment and materials needed for tunnelling, including the concrete segments that will be used to build the tunnel walls. Excavated soil and debris from the tunnel boring machines will travel along a conveyor system back to the shaft, where it will be collected and hauled away to be safely disposed.
From above: the launch shaft site for the Eglinton Crosstown West Extension served as a hub for tunnelling. The Yonge North Subway Extension will use a similar approach.
Tunnel portal
After tunnelling is complete, the launch shaft site will be converted into the tunnel portal — the permanent structure where Line 1 subway trains will enter and exit the underground tunnels.
The portal will be built on the same footprint as the launch shaft but is finished in a very different way. The temporary shaft infrastructure will be removed before permanent reinforced concrete foundations and walls are installed, followed by waterproofing and drainage systems. These will keep the tunnels dry and stable, and make sure subway trains move safely between the surface and tunnels.
A tunnel portal under construction for the Eglinton Crosstown West Extension.
Managing construction impacts
Metrolinx works closely with our contractors to minimize disruptions while we deliver new transit. We engage with communities to address potential issues and we strive to reduce and manage impacts whenever possible through a wide array of measures, including:
We also keep communities informed about what to expect during construction. You’ll hear from us well before work starts, and we’ll continue to share timely updates as work moves forward to make sure you have the latest information about progress and next steps.
To stay connected, you can sign up to our Yonge North Subway Extension e-newsletter.
Piling rigs are used to create foundations for the tunnel boring machine launch shaft.
Get in touch
We're committed to keeping you informed and engaged every step of the way as we build important transit projects like the Yonge North Subway Extension.
Our team is here to answer your questions, address issues, and provide the information you need. Reach out to us any time at YongeSubwayExt@metrolinx.com or 416-202-7000.
You can also book a meeting with us online or at our community office in York Region.
