Construction work will shortly begin on a new water supply tunnel in Vancouver, Canada, but the joint venture team responsible for the project will have to ensure that the tunnel is capable of withstanding the effects of a major earthquake in the area.
According to Metro Vancouver, the water tunnel will need to be able to withstand a mega quake in the region of a magnitude of around 8 or 9 on the Richter scale. This is because the water pipeline is a primary supply link to several areas south of the Fraser River, and in 1997 an earthquake caused significant problems with the local water supply to several municipalities.
It took over a year to repair the damage and replace the damaged section of water main and the authorities are determined that this time around, the new water supply tunnel will be constructed to an earthquake proof standard to prevent any potential problems in the future.
The contract is worth $150 million and has been awarded to a joint venture team that includes Aecon JV partnership. The JV will be digging two excavation shafts and excavating a water tunnel 1km long and 3.2 metres in diameter.
A specialist piece of equipment known as a Hydrofraise will cut out the perimeter of the tunnel shaft using tungsten carbide cutting blades to break the soil down. A pump inside the machine sucks the soil out and carries it back to the surface. Once the perimeter panels have been cut out, concrete is poured in to form a solid wall. When the concrete has set, the inside of the tunnel can be dug out.
Work on the south shaft should be completed by next summer and tunnel boring is expected to begin shortly after. Contractors hope to have completed the water tunnel by the summer of 2014.
Following an underground explosion in a New Zealand tunnel, one man has tragically been killed and a further six were injured. The accident in Onehunga in South Auckland happened on Saturday 4 June as contractors were working to connect a new water main to an existing water main.
The team of contractors had already removed one large section of pipe from the site without incident, but as they moved down into the tunnel to inspect the work, a large explosion occured.
Mark Ford, chief executive of Watercare Services, made the following statement in the aftermath of the blast: “It is with deep sadness that I confirm there was a serious incident at the site. This is a very dark hour for us – many of the crew on site are like family to us, and my heart goes out to all of those affected by what has happened.”
“We are not in a position to say at this stage what caused the explosion, however, we are working closely with the contractors and all the authorities, including the police, fire service and the Department of Labour,” he added.
By the end of Saturday afternoon, one of the injured men was still in a critical condition, but two more were reported to be stable and the other three had been discharged from hospital.
The fire service had spent the day making the site safe, although they had been unable to enter the tunnel due after dangerous levels of explosive gases were detected by specialist equipment. Technicians working on site said that although the gases were not toxic, they were extremely flammable, and until the gases had been identified it was not safe to enter the tunnel. In the meantime, emergency crews had isolated electricity and gas supplies to the area.
The tunnelling component of a water filtration project in British Columbia has finally come to an end, despite cost overruns and a change in tunnelling contractor part way through the job.
The previous contractor, Bilfinger-Berger Canada, was hired in 2004 by Metro Vancouver on a $100 million contract to build two twin tunnels, starting near the water filtration plant in the Lower Seymour Conservation Reserve and ending near the Capilano Reservoir in British Columbia.
By 2008, work had been halted on the $100 million project by the contractor due to concerns about safety underground and following a two year delay, Metro Vancouver decided to terminate Bilfinger-Berger’s contract on the job.
Another tunnelling contract for the completion of the twin tunnels was then awarded to a joint venture consortium of Aecon, Frontier-Kemper and J.F Shea to the tune of another £181 million. Thankfully, once the new contractor started work on the project in July 2009, there were no more problems. The new contractor still had approximately 6.3 km of tunnel left to excavate, but they were able to use all plant and equipment discarded by the previous contractor.
The remaining excavation work on the treated water tunnel had been completed by November 2010 and excavation work on the raw water tunnel was completed by October 2010.
The original termination of contract with Bilfinger-Berger is now the subject of a law suit filed in June 2008 alleging improper termination of the contract. Bilfinger-Berger is seeking $22.5 million in costs and a further $35 million for the return of site equipment and it alleges that an increase in budget indicates tunnelling conditions were more complex that originally believed. A ruling has yet to be agreed on the claim, but in the meantime, Bilfinger-Berger has placed a lien against the title to the lands in an attempt to secure their claim.