Seymour Capilano Twin Tunnels

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Two 7.1 km long tunnels have been constructed beneath Grouse Mountain and Mount Fromme so that water from the Capilano Reservoir can be treated at the Seymour-Capilano Filtration Plant. After over 10 years of underground and surface construction the Twin Tunnels project on the North Shore is now completed.

January 2005

The project began with the preparation of the site for the Seymour-Capilano Filtration Plant in the Lower Seymour Conservation Reserve and the sinking of a shaft 185 metres deep where a chamber was excavated and the tunnelling began.

Tunnel boring machines are lowered and assembled in the Seymour Chamber.

Trains are used to remove excavated granite rock.

Excavated rock is disposed in designated areas within the Lower Seymour Conservation Reserve

November 2010

An important moment in the project was the ‘breakthrough’ at the Capilano end of the tunnels. The tunnel boring machine broke through the rock separating the raw water tunnel from the treated water tunnel. At this point the tunnel boring was finished and work began excavating a large chamber in order to excavate a 270 metre shaft up to the surface connecting the tunnels to the Capilano Pump Station and the Break Head Tank/Energy Recovery Facility.

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May 2010

Raise bore machines excavated two shafts to the surface at the Capilano site.

Raised bore machine breakthrough the Capilano shaft.


Next steps in completing the tunnels involved removing the rail tracks, coating the walls with concrete where required and placing steel liners along a portion of the tunnel at each end. Each liner weighs 70,000 pounds or 35 tonnes.

Shotcreting is a process where concrete is sprayed onto the tunnel surface to hold loose rock in place.

70,000 pound tunnel liners are lowered into the Seymour Chamber Area.

The liners are loaded onto trains and readied for final placement.


Final work

Welding and grouting of liners.

Grout was used to fill in gaps between the liners and the rock face of the tunnel. Infrared photos identified where gaps were located.

Tunnels thoroughly cleaned. Treated water tunnel is disinfected.

The tunnels were connected to the shafts running from the Capilano Chamber up to the pump station.

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April 2015

The final commissioning of the system saw water from Capilano pumped to the Seymour Capilano Filtration Plant where it was treated and returned by gravity to Capilano for distribution to municipalities on the west side of the region.

The water from the filtration plant passes through turbine in order to generate electricity.

Pump station.

Seymour Capilano Filtration Plant.

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The Seymour Capilano Filtration Plant, the largest of its kind in Canada, now treats up to 1.8 billion litres of water per day from both the Seymour and Capilano Sources. The Plant is located in the Lower Seymour Conservation Reserve.

After passing through the Seymour Capilano Filtration Plant the Capilano reservoir water is returned to Capilano through the filtered water tunnel and distributed to homes across the west side of Metro Vancouver. Commissioned in spring 2015 these Twin Tunnels will ensure our supply of safe high-quality drinking water for future generations.

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