How Toronto is getting a new subway station below existing TTC platform

Building an underground subway station is already a complex operation, but constructing one beneath an active Toronto transit platform brings its own unique set of challenges. 

That's precisely the engineering headache playing out right now at multiple sites along the future Ontario Line, a 15.6-kilometre subway route through Toronto that will add 15 stations to the city's rapid transit network — including three with direct underground connections to existing TTC subway lines.

The Ontario Line's future interchange with Pape Station on the TTC's Line 2 Bloor-Danforth requires the construction of a new station below the active subway platform without disrupting critical eastbound and westbound train service. 

Pape Station's Ontario Line excavation flanks the existing subway tunnel, and crews have begun the preparatory process ahead of underpinning the existing station to allow excavation below in what Metrolinx describes underpinning as a "sensitive" operation.

During the underpinning stage, load transfer beams will be installed below the existing Pape station, structurally supporting the platforms and allowing excavation below to connect the site's north and south shafts.

Work on underpinning prep began in July, and Metrolinx expects the structural bracing of the station to continue until the spring.

This same method was used during the construction of the Eglinton Crosstown LRT, where Cedarvale Station (formerly Eglinton West) was among the stops that required underpinning to allow excavation beneath active platforms.

The Ontario Line will eventually connect Exhibition Place with the Line 5 Eglinton when it opens in the early 2030s, bumped back from an initial estimate that the route would be operational as early as 2027.

While an opening date remains elusive, the line's cost has ballooned to a staggering $34 billion, more than triple the initial estimate of $10.9 billion.