The milestone marks the end of Alice’s 10-month long, 2.4km underground journey from Owairaka to Waterview.
It also marks the completion of the first of the twin tunnels that will connect Auckland’s southwestern and northwestern motorways as part of the New Zealand Transport Agency’s (NZTA) Waterview Connection project.
The tunnel bored by Alice is the 10th largest in diameter in the world, and the longest road tunnel in New Zealand.
Once opened in early 2017, it will carry three lanes of southbound traffic up to 40m below Avondale and Waterview in west Auckland.
The tunnel – part of a 5km, six-lane motorway link from the Great North Rd interchange at Waterview to Maioro St in Mt Roskill – is a key part of the long-awaited Western Ring Route.
NZTA Auckland highways manager Brett Gliddon said the tunnel’s completion was a significant milestone for the $1.4 billion project.
“This is a fantastic achievement.”
Mr Gliddon said the breakthrough was completed safely and ahead of schedule.
“It is a huge engineering feat for New Zealand, one that is attracting worldwide attention.”
Alice will now be turned around to bore the northbound tunnel. However, turning around the 90m-long, 3100 tonne machine and reconnecting its cutting head and three trailing gantries was not expected to be completed until early next year, when tunnelling on the second tunnel could commence.
The machine’s second run, from Waterview to Owairaka, was expected to be completed in about October next year.
About a year of work would then be needed to complete the mechanical and electrical fit-out of the tunnels, including completing ventilation buildings at both ends and constructing 16 cross-passages to connect the tunnels.
The entire project – which also involves building surface connections to the existing motorways, 9km of new cycleways, new community amenities such as walkways, playgrounds and skateparks, and planting some 150,000 trees and shrubs – was due to be completed in early 2017.
The Waterview Connection was one of five projects to complete the Western Ring Route as an alternative to State Highway 1 through central Auckland and across the Auckland Harbour Bridge.
It has been prioritised by the Government as one of its roads of national significance.
But at a top speed of 8cm a minute, it would have taken us more than 5000 years to get there and back on a giant tunnel-boring machine called Alice.
Luckily, the 88m-long machine – which the Transport Agency imported from China for $55 million to dig twin tunnels to connect Auckland’s Southwestern and Northwestern motorways – has only 300m or so to go before emerging at Waterview early next month.
Although it is thrusting forward at a rate of 20m to 24m a day, engineers are reluctant to commit themselves to an exact date, given the sensitive pressure adjustments needed as the assemblage nears the surface. Despite the roar of 24 engines powered by 22,000 volts of electricity to turn the machine’s giant 14.46m cutting head with its almost 300 tungsten cutting tools at a rate of just under two rotations a minute, an almost total lack of vibration meant it would have been impossible for anyone on the surface to guess its exact position.
Behind us as we visit the 14.46m cutting face of the first tunnel yesterday, about 18m under Great North Rd, stretches a 2.1km cavern of lined concrete curving back to Alan Wood Reserve in Owairaka, from where the giant ground-eater pushed off in November last year.
Also reaching all the way back is a conveyor belt carrying about 3000cu m a day of soft rock liquidated to a toothpaste-like consistency to be loaded on trucks and dumped at an industrial development site over a disused Wiri quarry.
The air is fresh, courtesy of a massive 2.5m-diameter ceiling intake pipe, and the tunnel is well illuminated by fluorescent lights guiding us to the boring machine.
Not even diesel fumes from a shuttle carrying a 100-tonne payload of 10 concrete sections for the machine to line the tunnel as it goes can foul the air, although there is a dank alkaline smell reminding us to avoid contact with corrosive wash water under our feet.
After being driven most of the way in, we are electronically tagged through a gate to ensure there are no more than 40 people in the tunnel at a time. We are guided on foot the rest of the way on the flat surface of a concrete culvert being laid to carry power and other services before the $1.4 billion motorway link from Maioro St in New Windsor to the Northwestern Motorway at Waterview opens in 2017 with three traffic lanes each way.
Even the culvert – described as a “tunnel within a tunnel” – is a roomy 3.5m wide by 2.5m high. The 40-person limit is to ensure salvage chambers on the machine can provide at least three days of air to their occupants in an emergency.
Once on board the three-decked machine, the roar of 24 motors turning the mining head with its almost 300 tungsten cutting tools at almost two rotations a minute makes conversation difficult. A giant screw rising at 45 degrees from an earth-holding chamber behind the cutting head is dropping grey slurry looking like a bubbling geothermal mud pool on a conveyor belt as the machine’s operator, cocooned in a control room, adjusts balancing pressures to keep the tunnel face stable.
Tunnel construction manager Iain Simmons says the machine has a pushing force of 30,000 tonnes, yet only about 5000 tonnes is typically needed “so he [the operator] has to be really careful”.
But despite the din and massive power, there is no vibration, which is just as well given that the machine has tunnelled directly below the Mt Albert Pak’n Save supermarket and Oakley Creek at depths of up to 45m.
Mr Simmons says pressure will have to be eased off as the machine edges its way to the surface. He is blase about the prospect soon of breaking through a portal built in a trench next to Waterview Primary School and an embankment which will lift traffic to a three-level interchange for which support structures are already towering 20m above the Northwestern Motorway.
For him, that will simply signal the start of four months of maneuvering the tunnel-boring machine around in a tight trench so it can start digging its way back to Owairaka to complete the second of a pair of 2.4-kilometre tunnels needed to link the Southwestern and Northwestern motorways, and complete the region’s 47-kilometre western ring route alternative to State Highway One.
Once the machine is fully under way on its return journey, after a two-phase turnaround operation, the Transport Agency’s Well-Connected contracting alliance will begin drilling 16 cross passages between the main tunnels to provide motorists with escape routes in emergencies.
Although the second tunnel is expected to take only until about next September to dig, there is plenty to be done – including building venting towers at both ends – before the full 4.8km Waterview Connection – half of which will be surface motorway – opens in 2017.
Roads near Auckland’s $1.4 billion Waterview motorway project had to close to enable delivery of part of a giant tunnelling machine that has arrived from China.
The New Windsor entry point to the Southwestern Motorway and a section of Sandringham Rd Extension were closed for five hours from midnight as the part is trucked from the waterfront, where 97 containers into which the $54 million tunnel-boring machine was packed for its voyage from China are being unloaded.
Transport Agency contractors will spend three months reassembling the 2300-tonne machine with its 14.46m-diameter drilling head in a deep trench at Alan Wood Reserve, before the first of two 2.4km motorway tunnels are drilled.
Sandringham Rd had to close so a culvert can be reinforced to take the extra heavy load.
A second two-lane tunnel through Mt Victoria could be open to traffic within a decade.
The NZ Transport Agency has today revealed plans for a second Mt Victoria Tunnel and widening of Ruahine St and Wellington Rd to connect to the new $90 million Basin flyover.
The projects are all part of a $800 million traffic improvement project from Ngauranga to the airport, and today’s announcement sits alongside new details about the flyover project and a the reveal of a major public transport study for Wellington.
The plans for the second tunnel show it would sit directly along the northern side of the existing tunnel.
It would provide two lanes for east-bound traffic, along with a separate pedestrian and cycle facility linking to the flyover. On the Hataitai side of the tunnel, Ruahine St will become four lanes, and will also sport a pedestrian and cycling path.
Heading towards the airport Wellington Rd will be widened to six lanes and traffic lights will be installed at the intersection with Ruahine St.
The transport agency plans to seek resource consent late next year, with an aim to building the roading projects between 2018 and 2022.
The agency’s regional director Jenny Chetwynd said the proposals were all ”future proofed” so that they would be compatible with projects identified through the public transport study, also released today.
Key changes to the proposals had been made since the project was first looked at in 2011, she said.
”The big changes occur along Ruahine St where the width of the road has been reduced and therefore, the amount of land required from the Town Belt also reduces. This is a positive result as this was a concern raised through our consultation.”
The projects, in conjunction with the flyover, would be a big step forward for Wellington transport, she said.
Greater Wellington regional council chairwoman Fran Wilde said the projects were essential to connect the central city to the airport.
”Easy access to and through the central city, together with enhanced connections to Wellington Airport and the eastern suburbs, is increasingly important for the region’s growth”.
SECOND MT VICTORIA TUNNEL
RUAHINE ST AND THE TOWN BELT