Giant tunnelling machine begins first stage of Auckland journey

The tunnel boring machine, made in China by a German company, has been custom-built for the Waterview project. Photo / Supplied

A tunnelling machine dwarfing the world's largest airliner is bound for Auckland, where it will spend more than two years digging an underground motorway from Owairaka to Waterview.

The $54 million machine - the 10th largest borer of its kind - has been formally accepted from its German manufacturer's Chinese factory by contractors building the Transport Agency's 4.8km Waterview motorway connection for $1.4 billion.

With a 2300-tonne circular cutting head 14.5m in diameter, making it as high as a three-storey building, the 97m-long machine could easily swallow the body of an Airbus A380 and most of a rugby field.

The behemoth's handover this week to a Fletcher-led motorway construction alliance at the factory in Guangzhou follows a 14-month design, build and testing programme. It will now have to be dismantled for shipment to Auckland, where it is due to arrive in July.

The alliance has since last winter been digging a huge trench in Alan Wood Reserve, Owairaka, ready to re-assemble the machine in situ, for tunnelling to start in October.

Just lowering it section-by-section into the ground will require a 600-tonne gantry crane straddling the pit, which will be at the western end of 2km of surface motorway from Maioro St in New Windsor.

The machine will spend a year digging the first of two 2.4km tunnels, slotting in pre-cast concrete rings as it works its way through the ground, before being turned at Waterview to dig the second tunnel, burrowing back to where it started.

At a top speed of 8cm a minute, it will chew through up to 10m of ground a day at depths varying from 10m to 47m, beneath a thick layer of basalt rock and Oakley Creek, to complete the final link of the 47km western ring route by 2017.

Transport Agency northern highways manager Tommy Parker said the machine's size reflected that of the overall project, both being "on a scale the likes of which we have never seen before in New Zealand".

He said the machine's maker, Herrenknecht, had agreed to buy it back at the end of the project for about 20 per cent of its original price.

The machine would not be suitable for digging other tunnels but some of the components might be.

Big digger

Waterview tunnel boring machine

* Length: 97 metres

* Diameter of cutting head: 14.5 metres

* Cost: $54 million

* Top speed: 8cm a minute

* Mission: Dig out 800,000 cubic metres of earth (enough to fill 320 Olympic-sized swimming pools) for two 2.4km tunnels.