scarborough subway extension

Giant machine named after David Bowie is about to break all kinds of Toronto records

The TTC's Line 2 subway is about to see some major changes, or maybe I should say "chu-chaaayn-ges," as an enormous machine named after one of David Bowie's many distinct eras has begun carving out the new Scarborough Subway Extension.

The massive tunnel boring machine (TBM), dubbed Diggy Scardust through a public naming competition, pays homage to Bowie's glam-rock-defining Ziggy Stardust era with a playful twist referencing its coming dig through Scarborough.

Diggy began its nearly eight-kilometre trek on Tuesday, getting underway from its launch site at Sheppard Avenue and McCowan Road.

It will move roughly 10 to 15 metres per day on a 6.9-kilometre path southbound, using a huge circular cutting head to forge through the earth and rock, and placing liner segments along the excavated tunnel as it crawls along.

Diggy will meticulously push through on its subterranean voyage towards Eglinton Avenue East and Midland Avenue, where it will be extracted from the ground after a job well done.

But this isn't going to be just any average tunnel.

At a staggering width of 10.7 metres — equivalent to about a three-storey building — this will be the largest subway tunnel ever constructed in Toronto. In fact, it will stand as the widest-diameter subway tunnel in all of Canada.

It will also mark the first local instance of a single subway tunnel containing two sets of tracks operating in different directions, a departure from the twin-tunnel construction used for most modern rapid transit lines in Toronto.

This record-breaking giant may have only officially begun its journey this week, but its 7.8-kilometre tunnelling mission is really just the final home stretch on an epic voyage that saw the TBM travel from its manufacturing point in Schwanau, Germany, all the way to Toronto.

After being constructed and then disassembled by its manufacturer near the French-German border, the TBM was loaded into containers and shipped via barges along the Rhine River to the Dutch port of Westdorpe, where it embarked on a 6,300-kilometre trans-Atlantic trip towards its destination in Toronto.

The three-stop, $5.5 billion Scarborough Subway Extension is expected to complete in 2029-2030, which is just a bit longer than the Five Years promise David Bowie gave the world in the 1972 rock opera that inspired the TBM's name.

Lead photo by


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