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geotechnical tests on Yonge > Jul-Aug 2009

What is a geotechnical investigation?

A geotechnical investigation involves the collection and testing of soil samples. As part of the Conceptual Design Study for the proposed Yonge Subway extension, we need to determine what the ground conditions are along the proposed subway alignment. When the project receives funding, this will inform future design and costing decisions associated with materials, construction methodology, and tunnel depth.

Drilling will occur at predetermined locations along the alignment and will take soil samples at varying depths. Two borehole drilling machines will be working in parallel to expedite the schedule. Samples collected from the boreholes will be tested to determine their physical properties.

Where will this work be done?

The work is being done along Yonge Street from Steeles Avenue to High Tech Road. The majority of the boreholes are off the travelled portion of the road. However, there are two locations where the work will be located in the roadway and will require lane restrictions on Yonge Street. Additionally, there are three locations which are in close proximity to the road and may impact traffic flow.

When will this work be done?

Working from the south end to the north end, soil samples will be taken from 12 locations along Yonge Street over five weeks (see chart below), from 9:30 am – 3:30 pm.

Who is doing this work?

SPL Consultants Limited is conducting the investigations.

spadina subway

Yonge Subway Extension

Yonge Subway Extension

The planned Yonge subway extension will extend 7.4 kilometres north from Finch Station to Highway 7. This critical rapid transit link will include five stations at Cummer/Drewry, Steeles, Clark, Langstaff/Longbridge and Richmond Hill Centre. Intermodal terminals will be located at Steeles and at Richmond Hill Centre and 2,000 commuter parking spaces will be at Highway 407.


  • The Yonge Subway Extension is ready to move to full engineering and construction.
  • In April 2009, the Ontario Ministry of the Environment unconditionally approved the Environmental Project Report [and addendum] for the Yonge subway extension.
  • In 2012, the Conceptual Design Study that looked at specific engineering elements was completed and approved by the Toronto Transit Commission and The Regional Municipality of York.
  • In 2015, Metrolinx released the findings of a Yonge Relief Network Study, and recommended advancing the Yonge Subway Extension with preliminary engineering.
  • In June 2016, the Province of Ontario committed over $55 million to advance design work to 15%.
  • Engineering and construction will take approximately 10 years, and during preliminary engineering a more detailed schedule will be confirmed.

ridership & capacity

Metrolinx’s Yonge Relief Network Study analyzed options for crowding relief to the existing Yonge Subway line by examining new local and regional travel opportunities and improving mobility across the GTHA.

Key findings include:

  • Today, the Yonge Subway line is operating at +11% over capacity.
  • Significant relief to the Yonge Subway line will be achieved through already committed transit improvements, including the TTC’s automatic train controls [adds 36% capacity], new signals [adds 10% capacity], six-car trains [adds 10% capacity], the Toronto-York Spadina Subway Extension [adds 8% capacity] and Regional Express Rail/SmartTrack.
  • The Yonge Subway Extension can be built – with the capacity improvements noted above added during the 10 years of engineering and construction, the Yonge Subway line will be running under capacity by 2031.
  • The Downtown Relief Line has become a long-term project that will not be needed until after 2031.
  • A recommendation to “Direct staff to work in consultation with York Region, City of Toronto and the TTC to advance the project development of the Yonge North Subway Extension to 15% preliminary design and engineering.”
  • Only a subway can service the potential future daily ridership of 165,000 [two people per second] – even today, over 2,500 bus trips per workday are needed to serve the current demand.


  • Completes a critical missing link in the regional rapid transit system of the GTHA, making an easy and seamless connection between regions. To read about why the Yonge Subway extension to Highway 7 is considered a top priority, see The Missing Link.
  • Fuels a proposed 48,000 residents and 31,000 jobs at the Richmond Hill/Langstaff Urban Growth Centre at Highway 7 and Yonge Street.
  • Saves over 28 tonnes of greenhouse gas (GHG) per workday by replacing the 2,500 bus trips currently servicing this segment of Yonge Street.
  • Produces a lasting economic stimulus and creates jobs.
  • Aligns with plans for growth and rapid transit in the GTHA, integrating with Regional Express Rail, building on the existing investment of more than $3 billion in York Region’s rapid transit, and meeting the Province’s smart growth objective of a transportation hub at Yonge and Highway 7.
  • Almost eliminates the 2,500 bus trips per workday currently serving the demand between Finch and Highway 7.


Tunnelling Process

Subway Construction Techniques

Get the scoop on what goes on underground when building a subway.

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