Here's what it looks like inside Toronto's new record-breaking mega-tunnel
The largest subway tunnel in Canada is now three-quarters of the way to completion, and Metrolinx is sharing a rare glimpse inside the cavernous void being carved for the Scarborough Subway Extension (SSE) project.
Under construction since 2021, the long-awaited 7.8-kilometre, three-stop extension of the TTC's Line 2 Bloor-Danforth will functionally replace the closed Scarborough RT, carrying the line between the current terminus at Kennedy and a new end-of-the-line stop at Sheppard Avenue and McCowan Road.
While riders won't get to zoom through this enormous new tunnel until around 2030, the latest Metrolinx update is offering up a taste of what's to come.
The transit agency shared that the SSE tunnel is now 75 per cent complete, and work continues to extend the cylindrical void.
With an almost 11-metre-diameter tunnel — the widest of any subway tunnel in Canada — the SSE will feature a unique configuration with both directions of track running in a single-bore tunnel, versus the more common twin-tunnel method used on the majority of modern transit lines in the city.
For a sense of just how spacious this tunnel will be, you'd be able to comfortably house a three-storey building within the tunnel.
But even with its vast width, the SSE tunnel requires some specialized infrastructure for construction trains to pass one another. Metrolinx recently installed a 108-metre-long 'California Switch' within the tunnel worksite — a temporary, movable turnout that allows trains to pass using a single track.
According to Metrolinx, this temporary infrastructure will help "keep materials moving efficiently to the tunnel boring machine as excavation continues."
Metrolinx
