Tunnel Boring Machines: A Recap

The Crosstown tunnel boring machines (TBMs) completed their underground journeys from the east and west in 2016!

See Tunnelling 101 Fact Sheet and the TBM Fact Sheet.

Watch the milestones for Dennis, Lea, Don and Humber along the way:

September 2012: The west tunnels contract was awarded.

February 2013: West TBM parts arrive at the west launch site, at Black Creek Drive.

February 2013: The west TBMs are assembled on site. See timelapse photos.

TBM assembly

June 2013: The winning names of the TBMs were announced: Dennis and Lea for the west, representing the Mount Dennis and Leaside neighbourhoods; and Don and Humber for the east, representing the rivers. It is a tradition to name TBMs that are constructed for a specific project. Metrolinx ran a naming contest and received more than 500 entries. 

September 2013: Metrolinx CEO and Minister of Transportation announce the start of tunnelling! See video. 

November 2013: The east tunnels contract was awarded.

Spring 2015: East TBM parts arrive at the east launch site, at Brentcliffe Road.  See video.

January 2015: West TBMs break through the extraction shaft at Allen Road. See video.

April 2015: The west TBMs make their big move at surface level across Allen Road so TTC operations are not disrupted. See photo gallery.

TBM move photo

January 2015: The west TBMs arrive at their destination at Yonge Street! See video.

August 2016: The east TBMs arrive at their destination at Yonge Street!  See video. 


The Crosstown is a 19-kilometre corridor that includes a 10-kilometre underground portion, between Keele Street and Laird Drive. The underground potion is tunnelled by two pairs of tunnel boring machines, a.k.a. “TBMs.”

The project is split into three contracts: the west tunnels, the east tunnels, and the stations (including track and everything else) contracts.

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