As part of The City of Calgary’s ongoing Glenmore Dam Upgrade program, the existing bridge deck required replacement and new steel stop logs needed to be installed. After extensive conceptual investigations, the decision was made to relocate both the feedermain and gas line via a tunnel beneath the Elbow River, directly downstream of the Glenmore Dam.
Key Aspects and Challenges
- New 1500 mm C300 concrete feedermain and 300 mm gas line located within a 1650 mm concrete tunnel
- Five (5) vertical access shafts, varying in depth from 7 m to 31 m, required for installation of the tunnel components, for construction
- Almost 700 m of 1650 mm diameter tunnel
- Tunnel crossing 9 m below the Elbow River, and tie-ins between the new and existing feedermains on each side of the tunnel to mitigate construction risk and improve redundancy.
- Multiple high-rise utility crossings, which the tunnelling contractor elegantly resolved by proposing a revised methodology to his and the City’s benefit; revised methodology included a sloped tunnel and added in access shafts to be used for tunnel construction.
- Narrow shutdown windows; the feedermain is critical to South.