Port Mann Water Supply Tunnel Project Team Wins Prestigious Award

The Port Mann Water Supply Tunnel project was recognized by the Tunnelling Association of Canada on Monday, October 17 with their prestigious Canadian Innovation Project of the Year award. The award recognizes tunnelling projects that exhibit exceptional engineering skill, insight and innovation in the face of challenges. Several "firsts in Canada" were employed to achieve the final design.

The Port Mann Water Supply Tunnel project is a key component of Metro Vancouver’s critical infrastructure network upgrade program; this project replaces the existing pipeline constructed in the early 1970’s from Coquitlam to Surrey beneath the Fraser River, significantly increasing its’ seismic capability. This new tunnel ensures the continued delivery of safe drinking water south of the Fraser River, with the additional benefit of doubling the capacity of the existing main.

The Ausenco-led design team was charged with designing a water supply tunnel/pipe configuration capable of withstanding the expected 6m horizontal movement of liquefied soil due to a 1 in 10,000 year seismic event. To accommodate this, the 60m deep vertical concrete shafts (on either end of the 1km tunnel) and the water pipe within, are designed to yield and be permanently deformed and still maintain service in the event of a significant earthquake.

“In order to succeed with the design, the project team employed a number of firsts in Canada, including the first use of limit-state design for a shaft pipe and the first use of limit-state design for concrete shafts,” said John Sherstobitoff, Principal, Seismic and Structures, at Ausenco. “We used a complex set of computer models and iterative analyses to determine the soil-structure-pipe interaction so that the design can accommodate the very significant movement in the surrounding soils. The 50 m vertical pipe runs in the system are unrestrained except at the endpoints at the shaft base and valve chamber outlets allowing the pipe to bend and yield while remaining functional.”

In addition to this, the Project incorporates a number of other leading edge aspects:

  • Management of the highest ground water pressure of any tunnel to-date in Canada
  • Use of unreinforced shoring walls (slurry walls) up to 80m deep for the shaft excavation
  • The contractor, McNally-Aecon Joint Venture, utilized ground freezing underneath the Fraser River to allow repairs to a severely damaged TBM cutterhead.

The Ausenco-led design team provided detailed engineering and construction support and includes subconsultants McMillan Jacobs Associates (tunnel and slurry wall design); Golder Associates (geotechnical, environmental and permitting services).

Ausenco shares the Canadian Innovation Project of the Year award with these sub consultants and with Metro Vancouver, the contractor and key sub-contractors, and the construction manager, who worked collaboratively to complete the project.

For more information, please contact John Sherstobitoff, Principal, Seismic and Structures (john.sherstobitoff@ausenco.com)

The Port Mann Water Supply Tunnel case study can be found here