Water supply tunnel excavated under Burrard Inlet

Excavation is now complete at the Second Narrows Water Supply Tunnel.

The tunnel underneath the Burrard Inlet was excavated with the first slurry tunnel-boring machine to be used in Canada.

The work was being done up to 100 metres underground.

The excavation is an important infrastructure project that will make the region’s drinking water system more earthquake resilient and help meet growing demand for safe, high-quality drinking water.

“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.”

In order to complete the tunnel, first, a 50-metre-deep vertical entry shaft was excavated on the north side of the inlet, followed by 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 new 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.

Now that the tunnel is complete, three steel water mains will be installed inside and connected to the existing water system with new valve chambers.

Construction on the Second Narrows Water Supply Tunnel began in 2019 and the project is expected to be complete in 2025.