Case Studies: Current Projects
Twin TBMs bore Vancouver's water filtration tunnels
- Machine Type: Main Beam TBM
- Number of TBMs: 2
- Diameter: 3.8 m (12.5 ft)
- Project Type: Water Transfer
- Tunnel Length: 2 x 7.2km (4.5 mi)
- Owner: Greater Vancouver Regional District
- Contractor: Bilfinger Berger (Canada)
- Location: North Vancouver, British Columbia, Canada
Project Overview
The Seymour-Capilano Water Filtration Project seeks to improve the filtration of drinking water in Vancouver, British Columbia. The completed filtration system will clean 1.8 billion liters (475.5 million gallons) of water a day and will lower the water turbidity (cloudiness) and micro-organism levels to meet federal standards for drinking water.
The project calls for twin tunnels, each 7.2 km (4.5 mi) long. The tunnels will transport untreated water from the Capilano reservoir to a filtration plant in the Lower Seymour Conservation Reserve and will return treated water to the Capilano reservoir for public consumption.
In 2004, the project owner, Greater Vancouver Regional District, awarded the construction contract to Germany-based Bilfinger Berger. The contractor chose two 3.8 m (12.5 ft) diameter Main Beam Robbins TBMs to bore the tunnels in intrusive granitic rock with strengths of 200 – 265 MPa (29 – 38 ksi).
Each TBM is outfitted with probe drills that will be used for the entire length of the tunnels. The probe drills will probe ahead 40 m to check for pockets of underground water and verify the geology. The tunnel will be unlined during excavation, but each machine is equipped with a ring beam erector to install full or partial beams if difficult geology is encountered.
The first of the two TBMs were delivered on May 18, 2006 and began boring on July 1, 2006. The second Robbins TBM is boring from the same launch shaft. Both machines were assembled in very short (60.5m/200ft and 70.5 m/230 ft) starter tunnels at the bottom of the 180 m (591 ft) shaft. Because of the short tunnel lengths, both TBMs are excavating with their back-up systems partially constructed until they bore ahead 200 m (650 ft). The TBMs were assembled with only 11 decks of their respective 35 deck back-up systems. Updates of this project will be posted as boring continues.
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