• Railroad / Transit Tunnels
  • Waterproofing
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Toronto Transit Commission Relief Line South

Toronto Transit Commission

The Toronto Transit Commission has approved the Preliminary Engineering Design of the Relief Line South Project, which is a planned new 7.5 km long subway line that runs through the center of downtown Toronto. It will connect the Yonge-University-Spadina Subway (Line 1) to the Bloor-Danforth Subway (Line 2) in the downtown area. The Relief Line South will help to relieve crowding on Line 1 south of Bloor, at the Bloor-Yonge Station, and on the surface transit routes coming in and out of downtown. Construction of the Relief Line South includes construction of twin running tunnels by means of tunnel boring machines, five new stations, and modifications to three existing stations, which will be converted to interchange stations.

Preliminary SEM Station Design:

Gall Zeidler Consultants (GZ) is providing preliminary engineering services for the design of the Sherbourne and Sumach stations. It is planned for the stations to be mined in hard rock. As such, the engineering support services provided by GZ include preliminary design of the temporary and permanent support measures for the SEM caverns as well design of the waterproofing system. In addition, GZ is aiding in constructability reviews and value engineering studies for the planned stations, as well as for the planned alignment.


Toronto, Canada


2017 – Present


Underground Station caverns


4.66 mi (7.5 km)


Georgian Bay Shale, glacial tills




Toronto Transit Commission