Three Mains, Two Reservoirs, One Goal: Vancouver’s Water Mains Are Ready to Shake Things Up

The resiliency of water supply systems in seismic regions is crucial for maintaining uninterrupted service during and after earthquakes, especially in areas with growing populations and aging infrastructure. This paper reviews the design and construction of the Second Narrows Water Supply Tunnel project in Metro Vancouver, a high-pressure, large-diameter, three-main marine crossing. To meet modern seismic design standards, three existing water supply pipes crossing Burrard Inlet are being replaced with a single Ø 6.3 m, 1.1 km long carrier tunnel, housing one Ø 1,524 mm and two Ø 2,438 mm pipes. Valve chambers will control water flow at each end. The paper discusses project justification, system requirements, and engineering strategies. It also examines construction implementation from the perspectives of resident and field engineers, highlighting opportunities to accelerate construction and improve functionality. Lessons learned from constructing the shafts and valve chambers are shared, focusing on enhancing seismic resilience.