Ottawa Light Rail Transit - Execution

City of Ottawa
OLRT Constructors - Dragados, SNC-Lavalin and EllisDon
$2.1 billion CAD
March 2012 — December 2019
Services performed
Sire supervisions services, engineering support and monitoring assessment. 24/7 presence on site to facilitate RES process and implement design requirements on site.
Ottawa's Confederation Line runs from Tunney's Pasture station in the west to Blair station in the east, is 12.5 km long and includes 15 stations. The central piece is a 2.5 km long tunnel, running under the central business district of the city and including three underground stations. The twin track running tunnel and the three underground stations were constructed using the mined construction method in order to minimise surface disruption. The underground stations are located directly adjacent to existing, sensitive and historic buildings and required strict adherence to design and risk mitigation processing during construction. The Dr. G. Sauer & Partners on site team supported the contractor to meet these requirements.
The geology varied between competent limestone and fractured shale. A soft ground section included variable glacial till deposits of sand, silt and clay layers and a groundwater table close to ground surface.
Ottawa, Canada


  • 3 large mined caverns & twin track running tunnel located mainly in limestone rock mass
  • Sensitive urban environment in close proximity to existing buildings and infrastructure
  • Minimum surface impact during construction by tailored excavation sequence
Station cavern and running tunnel construction under way

Cavern construction under way

Excavation of station cavern complete with tension ties visible