VANCOUVER—A historic tunnel excavation has been completed on the Second Narrows Water Supply Tunnel in Vancouver.
The infrastructure project aims to make the region’s drinking water system more earthquake resilient and help meet growing demand for safe drinking water.
“The tunnel underneath the Burrard Inlet was excavated with the first slurry tunnel boring machine to be used in Canada, and the work was being done up to 100 metres underground,” said Sav Dhaliwal, chair of Metro Vancouver’s board of directors, in a statement. “Completing this tunnel is an important milestone in this project and a remarkable testament to the innovation that is being used in Metro Vancouver to bring clean drinking water from the North Shore to the rest of the region.”
The work required crews to first dig a 50-metre-deep vertical entry shaft on the north side of the inlet as well as a vertical exit shaft more than 100 metres deep on the south side. The tunnel boring machine — 135 metres long, with a 6.69-metre cutting diameter and nicknamed Lynn Marie — launched from the north shaft in August 2020.
The 6.3-metre-diameter, 1.1-kilometre-long tunnel was excavated 30 metres below the bottom of Burrard Inlet, east of the Ironworkers Memorial Bridge. With an internal diameter of 5.8 metres, the Second Narrows Water Supply Tunnel is one of the largest tunnels ever built by Metro Vancouver. It runs between a Metro Vancouver works yard in the District of North Vancouver and Second Narrows Park (also known as Montrose Park) in Burnaby.
Crews now must place three steel watermains, one 1.5 metres in diameter and two 2.4 metres, inside. The mains will then be connected to the existing water system with new valve chambers.
“The new tunnel and watermains will replace three existing shallow buried watermains that went into service between the 1940s and 1970s, which are vulnerable to damage during an earthquake and are nearing the end of their service lives,” said Malcolm Brodie, chair of Metro Vancouver’s water committee. “Metro Vancouver is constantly upgrading its water supply system to maintain the quality and reliability of the region’s excellent drinking water, and to make the system more resilient.”
Metro Vancouver supplies nearly 2.7 million people with drinking water each day. This project is one of five new regional water supply tunnel projects that are being constructed to meet current seismic standards and increase capacity. The Port Mann Water Supply Tunnel went into service in 2017 and preparation is underway for construction of the Annacis Water Supply Tunnel.
Construction on the Second Narrows Water Supply Tunnel began in 2019 and the project is expected to be complete in 2025. The construction budget is $445 million.