First publishedon www.WorldHighways.com
New Zealand prime minister John Key led an official ground-breaking ceremony this week to allow the start of excavation work for two new 2.4km-long motorway tunnels beneath suburban Auckland. The Waterview Connection project is on schedule to begin its main construction phase next year, and the prime minister was on hand to turn the first soil for a 30m-deep trench which is needed to allow access for the tunnels’ southern approach trench in the west Auckland suburb of Owairaka.
The trench will be used to assemble an 85m-long tunnel boring machine in readiness for the start of proper excavation work next year. The New Zealand Transport Agency
’s (NZTA) highways manager for Auckland and Northland, Tommy Parker, told the opening ceremony that a range of preparatory works and environmental controls have already been put in place to allow building work to start, such as the realignment and rehabilitation of parts of Oakley Creek and the relocation of local wildlife and plant life to new habitats.
According to Parker, when the southern approach trench is complete, the tbm will descend to a depth of 45m and pass below a layer of hard volcanic rock. “To create the launch pad for the machine, we first have to excavate through a significant chunk of this basalt to reach the softer soil conditions below, and that is the process we have now officially begun today,” he said.
Excavation of the trench will involve a series of controlled explosions to fragment the hard igneous rock. “This not only allows the excavation to be carried out faster, it also significantly decreases the impact felt by local residents as it reduces the amount of traditional rock-breaking activity required. Basalt retrieved through this process will be re-used throughout the project, and for landscaping,” Parker added.
The 5km-long Waterview Connection tunnels will run between Owairaka and Waterview, offering drivers a new six-lane motorway link between SH16 (the “Southwestern Motorway”) and SH20 (the “Northwestern Motorway”) and the NZTA hopes that the scheme will complete Auckland’s Western Ring Route. Waterview Connection is New Zealand’s biggest and most complex road construction project to date, says the agency.
The two new tunnels are part of a wider national plan and they are one of the seven “Roads of National Significance” that NZTA and the New Zealand government has outlined as vital the country’s economic outlook.
To see how World Highways covered the launch of the Waterview Connection scheme in detail, and to view a map of the project, please take a look at our story “Building New Zealand's landmark tunnel
,” written by Kristina Smith and first published on October 31 2011.