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It was announced today that tunnelling has begun for Ontario Line 3. With work now advancing along the full corridor across Toronto, the line will run from Exhibition Place in the west to the Eglinton Line 5 at Don Valley station. Adding 15 stations and making more than 40 transit route connections, the line will move people more quickly through much of central Toronto when it opens in the 2030s.
Tunnelling operations are beginning from the western terminus at Exhibition station, where a pair of tunnel boring machines (TBMs) will excavate parallel tubes beneath the downtown, reaching depths of up to 40m below the surface. The machines tunnelling this section of the line are named Libby and Corkie for Liberty Village and Corktown, the neighbourhoods at either end of these tunnels. The winners of a 2025 contest to find catchy and appropriate monikers for the TBMs, the names were suggested by one of UrbanToronto's longtime Forum contributors and a moderator, Jason Paris. Paris is possibly the only private citizen on the planet to have named four TBMs, as his entries for a similar contest in 2013 to name the Eglinton Line 5 TBMs, were also the winners of that contest. Those machines were named Dennis and Lea, for Mount Dennis at the west end of the tunnels, and Leaside at the east end. Those names also slyly referenced Toronto's first Poet Laureate Dennis Lee, a well know multidisciplinary author, editor, and teacher, particularly known as a children's writer.
The first TBM to launch here is advancing the eastbound tunnel, with a second to follow for the westbound tunnel, (but also proceeding from west to east), as work proceeds in stages along the route. These parallel tunnels will extend toward the Don Yard near the Don Valley Parkway and Lake Shore Boulevard East, where trains will transition to an elevated guideway crossing the Lower Don River.
“It’s been more than 60 years since we last tunnelled a subway in Toronto’s downtown core, so this is a very pivotal moment for the people of this great city,” said Michael Lindsay, President and CEO of Metrolinx.
At Exhibition station, already operating the Lakeshore West GO line, rebuilt platforms, a new concourse, and new entrances are being constructed on both sides of the active rail corridor. The station will serve as an interchange for GO Transit and Ontario Line 3. This month, an eastward-facing drone shot captures a steel structure that has been erected over the active GO rail corridor south of Jefferson Avenue, forming a deck to enable work above the tracks. The blue-painted framing will extended to bridge multiple tracks, creating a platform allowing crews to proceed with concourse-level construction while maintaining uninterrupted rail operations below.
From a temporary pedestrian bridge above the station approach's construction site, a westward view captures reinforced concrete retaining walls lining the excavation, with cross-bracing supporting the sides as crews work below grade.
“Today marks a major step forward as we begin tunnelling the Ontario Line through the heart of downtown Toronto,” said Mayor Olivia Chow. “This project is part of a historic investment in public transit to fight gridlock, cut commute times, and keep people moving across our city.” Elsewhere along the route, excavation work has reached advanced stages at several downtown stations (some with recent tentative name changes), with major digging completed at King West (at King and Bathurst), Moss Park, and the Distillery District sites, and nearing completion at Chinatown (at Queen and Spadina).
Seen below in a southeast-facing image from last month, the TBM support area is active beside the GO Lakeshore rail corridor. In the foreground, the launch shaft is fully formed with reinforced concrete retaining walls and internal steel bracing, housing the partially assembled TBM. A large yellow mobile crane and a red lattice boom crawler crane are positioned over the shaft and adjacent staging area.
In this top-down view, assembly of the second TBM is underway within the linear staging area running parallel to the GO rail corridor. The elongated TBM launch zone is framed by a series of steel and support beams spanning the excavation.
UrbanToronto will continue to follow progress on these developments, but in the meantime, you can learn more about them from our Database files, linked below. If you'd like, you can join in on the conversations in the associated Project Forum threads or leave a comment in the space provided on this page.
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