Second Narrows Water Supply Tunnel
project details
Client Name
Metro Vancouver
Location
Burrard Inlet
Completion Date
December 2023
Services Provided
Materials testing: soils, concrete and shotcrete used to construct the tunnel.
the scope
The Second Narrows Water Supply Tunnel is one of five new tunnel crossings being built in the region. It will house three new steel water mains connecting the North Shore watersheds to Vancouver, Burnaby, New Westminster and other parts of the region, replacing two aging mains — installed in 1948 and 1978 — that are at risk of collapse even in a moderate earthquake. Built to current seismic standards to withstand a major earthquake, the tunnel will help ensure reliable delivery of clean drinking water should a catastrophic event occur. Construction spans east of the Ironworkers Memorial Bridge between the District of North Vancouver and the City of Burnaby and includes two shafts, one on each side of Burrard Inlet.
the solution
The tunnel is being excavated deep underground by a tunnel boring machine launched from a 68 m deep vertical entry shaft on the North Vancouver side, progressing south beneath Burrard Inlet through 1.1 km of sedimentary rock and soil before crews grind upward through more than 110 m of rock to the vertical exit shaft on the Burnaby side. Construction activities include shaft excavation and shoring, valve chamber and pipe installation, welding, backfilling and restoration. Once excavated, three steel water mains are installed inside the tunnel and connected to new valve chambers at each shaft and into the regional drinking-water system. Metro Testing + Engineering’s role is materials testing of the soils, concrete and shotcrete used to create the tunnel — a vital check on how those materials will perform.
the outcome
With pipe deliveries anticipated from 2020 and completion expected by the end of 2023, the new tunnel will provide a seismically resilient connection between the North Shore watersheds and the regional drinking-water system, safeguarding the supply of clean drinking water to Vancouver and the Tri-Cities in the event of a major earthquake.
