Tunnelling works have geared up on the Seymour-Capilano water project in Vancouver, British Columbia, with the TBM back-up being installed. Shortly before the gantries were reconfigured from 11 decks to 35 for full operation, the two 3.8m diameter Robbins TBMs had advanced 500m and 430m, respectively.
To get the machines underway, contractor Bilfinger Berger Canada started the main beam TBMs from the same shaft using the partially constructed back-ups until each had bored 200m (T&TI, December 2006, p23-26) to create sufficient space for the complete train assemblies.
Driving at depths varying between 160m and 640m, the twin drives will predominantly cut through granodiorite. While the parallel bores will be 7.2km runs, about 100m apart, once complete the project will see them convey water in a contra-flow operation.
For Greater Vancouver Water District’s (GVWD) plan to boost water quality for the city, raw water will be drawn down one tube from Capilano reservoir and then treated at Seymour before being returned via the other tunnel for distribution.
The tunnels are the largest ever built for GVWD and will help overcome the problems of turbidity in water supplies recently suffered by thousands. Following landslides into the Capilano and Seymour reservoirs last November after heavy rainfalls, the city known for its quality of life was left issuing public health warnings to boil water.
Critics of the chaos claimed political fights over privatisation had delayed plans to boost water treatment capacity. The scheme should be mostly in place in early 2009.
