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Preliminary assessments have concluded that a tunnel under Sparks street would be technically feasible.  The intent of these preliminary assessments was not to finalize an exact alignment (both horizontal and verticab| but rather to consider the implications of this option in terms of feasibility, potential constraints and impacts on transit customers.

Sparks Street was chosen because:

• proximity to the downtown core;
• can accommodate the alignment of a tram to/from Portage Bridge; and
• proximity to the O-Train stations to facilitate underground transfers between the two systems.

Key findings of these preliminary assessments include:

• several constraints exist under Sparks Street, but none that would prevent the construction of a tunnel.  Some of these issues include:
  • the right-of-way width of Sparks Street will limit the width of the tunnel and stations;
  • existing underground infrastructure and utilities will have to be avoided or relocated;
  • access to stations will have to be added at surface level, possibly incorporated into existing buildings; and
  • special attention will be paid to heritage and security issues for certain buildings.
• the elevation difference between the Portage Bridge and downtown Ottawa should facilitate tunnelling through the existing bedrock;
• major underground infrastructure at Kent Street would have to be relocated to accommodate the construction of the tunnel. This will require more detailed analysis;
• a 3 station option would not be viable, based on the space limitations for the design of the underground stations and their proximity to each other in the downtown core.
• the approach to the tunnel portal will have impact on the open space west of Commissioner Street, which this project will have to mitigate.

The following is the concept plan for a tram tunnel under Sparks Street: