Seymour–Capilano Twin Tunnels Deliver Treated Water to Metro Vancouver Residents
Drinking water for Vancouver’s Lower Mainland communities comes from rain and snowmelt collected by three mountain watersheds. Metro Vancouver is responsible for storing and treating this vital resource and supplying clean, safe drinking water to over 2.4 million residents.
Twin tunnels deep beneath Grouse Mountain and Mount Fromme, both located just north of Vancouver, Canada, convey water from the Capilano Reservoir to a new Seymour-Capilano filtration plant, before being returned to the Capilano system for distribution. The tunnels measure 3.8 m in diameter and 7.1 km in length, with shafts up to 275 m deep. Mined westward using hard-rock tunnel boring machines, the tunnels were designed with steel-lined vertical shafts and end sections, and central sections in solid rock or lined with shotcrete.
Designing tunnels in British Columbia’s rock conditions required a leading, world-class tunnel designer. Hatch implemented innovative approaches that produced a resilient tunnel design and employed new technologies. Computational fluid dynamics aided the design of rock traps at the ends of unlined sections, and infrared technologies provided quality assurance for the grout backfill behind the steel liners. Hatch was also an integral part of the construction team, providing the resident engineering, inspection and supervision on the project.
Sustainability was a core value that helped guide design and construction decisions and future operations. The tunnels were connected to an energy recovery facility to offset energy used to pump water to the filtration plant. Optimizing the length of unlined tunnel reduced the amount of steel and backfill materials.
With a hydraulic capacity of up to 1,250 ML/day, this feat of deep-rock tunnel engineering went into operation in March 2015 and is a lasting contribution to the region’s water infrastructure.
The Seymour–Capilano twin tunnels project received an Award of Merit on April 9, 2016 from the Association of Consulting Engineering Companies—British Columbia.