Owner
City of Ottawa
Client
OLRT Constructors - Dragados, SNC-Lavalin and EllisDon
Cost
$2.1 billion CAD
Timeframe
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.
Description
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.
Geology
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.
Location
Ottawa, Canada
Highlights
- 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
Cavern construction under way
Excavation of station cavern complete with tension ties visible