First look at photos of the massive digging machine being built to tunnel Scarborough subway.

See the digging machine for the Scarborough Subway Extension

First look at photos of the massive digging machine being built to tunnel Scarborough subway.

Sep 2, 2021

In a small German town bordering France, situated along the Rhine River, work is well underway to bring more subway service to the east end of Canada’s largest city. Take a first look at the mighty machine – which you could, in the future, actually name.

While work continues here at home to prepare the launch shaft for the Scarborough Subway Extension’s tunnel boring machine, workers in Schwanau, Germany, are busy manufacturing the machine itself, commonly referred to as a TBM.

First look at photos of the massive digging machine being built to tunnel Scarborough subway.

The main drive unit of the tunnel boring machine that houses the main bearing and drive motors (Herrenknecht photo)

A big, single tunnel calls for a big tunnel boring machine – one that can build a tunnel with a 10.7 metre diameter, soon to be the biggest subway tunnel in Toronto. The 7.8-kilometre Scarborough Subway Extension will be the first subway project in Toronto to operate in both directions within a single tunnel, requiring only a single boring machine to create all the necessary space.

The TBM for the Scarborough Subway Extension is being manufactured by Herrenknecht, which has supplied tunnelling technology for underground infrastructure around the world, including major subway projects in the UK and around Europe.

The TBM Build

For the past few months, teams at Herrenknecht’s manufacturing facility in Schwanau have been busy preparing a custom-built TBM for the Scarborough Subway Extension. Today, Metrolinx is sharing an exclusive sneak peak of the TBM being brought to life half a world away.

a crewman working on a large half circle of steel.

Herrenknecht crews working on the lower half of the tunnel boring machine forward shield (Herrenknecht photo)

After teams complete quality control and testing at the Herrenknecht facility, at the end of September, they will dismantle the massive machine. Due to its size, the machine will travel in multiple shipments, all making their way to Canada by boat. Metrolinx News will be your one-stop shop for the latest updates as the TBM and its many parts travel across the Atlantic Ocean and make their way to Scarborough.

Arriving Next Year

The TBM shipments are set to arrive on Canadian shores in early 2022 and will then travel by truck to the launch shaft site at McCowan Road and Sheppard Avenue, where crews will re-assemble everything.

Later in the spring, they will lower the assembled machine into the ground so it can begin tunnelling its way south under McCowan Road, digging about 10 metres of tunnel daily.

After completing this leg of its journey, workers will remove the machine from the ground at an extraction shaft that will be built at Midland and Eglinton.

metal work.

The section of the stationary shell of the tunnel boring machine which contains the pushing rams. (Herrenknecht photo)

You Name It

Metrolinx will also be launching a TBM naming contest later this fall to crowdsource names for Scarborough’s new tunnel boring machine – much the same way the tunnel boring machines used on the Crosstown route were named by the public. Stay tuned for details about this contest, including how you can participate, in the coming weeks.

Images shows Crosstown boring machines

Crosstown tunnel boring machines being lowered at a launch shaft site (Metrolinx photo)

The three-stop Scarborough Subway Extension will bring seamless subway service to Scarborough, making it easier for riders to get around the region and choose transit first. Follow the project on Twitter (@ScarbSubwayExt) and stay up-to-date on the latest project news at

by Joshua Patel Metrolinx communications senior advisor, subway program