Vancouver, British Columbia – Port Mann Main Water Supply Tunnel

BRITISH COLUMBIA

Vancouver

Port Mann Main Water Supply Tunnel

McNally/Aecon JV

The $149.5 million project for the Greater Vancouver Water District was given NTP in May 2011 with final completion estimated for June 2015. The project involves constructing a new water supply main under the Fraser River, just downstream of the Port Mann Bridge. When complete, this new water main will help ensure the continued reliable delivery of clean safe drinking water to the municipalities south of the Fraser River, and will substantially increase the capacity of the existing main.

The water main will be constructed in a tunnel driven through soil, 35 m underneath the riverbed. The 1000-m (3,280-ft) long, 3.5-m (11.5-ft) diameter tunnel will be excavated under the Fraser River at pressures of up to 6 bar using an earth pressure balanced tunnel boring machine (EPB TBM). The tunnel will be lined with 2.8-m ID precast concrete segments. The next phase of project includes lining the tunnel with 2.1-m water supply carrier steel pipe and tunnel backfill concrete in the annulus. Finally, both shafts will be topped with a valve chamber.

The tunnel will be mined from the South Shaft and will mine the tunnel to the north at a downward gradient. Subsurface conditions range from sand and gravel to silty clays. Hydrogeological conditions at the project area are controlled by the combined influences of local topography and complex geological settings. Artesian piezometric levels were measured at the South Shaft are on the order of 5.1 m above ground surface.

The project is currently 50 percent complete, both shafts have primary ground support completed and base plug installed.  Final lining is under way in both shafts. Manufacturing of customized tunnel boring machine (TBM), precast concrete segments and specialized equipment for hyperbaric interventions is complete.

The design was completed by Fraser River Tunnel Group (Ausenco, Jacobs Accociates, Golder Associates), with Hatch Mott MacDonald as the project manager. Subcontractors included Bencor Corportation of America (Slurry Walls), Armtec (precast tunnel segments), Lovat/CAT (EPB TBM), Hytec (Hyperbaric Equipment); and Ballard Diving and Salvage (intervention support and equipment).