Tunnel of the taniwha

Construction work at the Waterview Road Connection. Photo / Doug Sherring

At 14 metres in diameter, the twin tunnels of the Waterview Connection will be the biggest in Australasia. Yet the new motorway will burrow quietly beneath the parks and suburbs of the Auckland isthmus, not even emitting a gentle hum to tell those above of its existence. It will be a latter-day taniwha.

Goggles shield Kapeliele Vatuvei's eyes from the wintry glare and the welding spatter, as the scaffolder works at the southern entrance to New Zealand's newest and biggest tunnel project.

Deep in the pit, dwarfed by tunnel faces 10 storeys high, workers on the Waterview Connection scurry about looking like tiny orange-coloured ants.

Some drive diggers, scooping out some of the 800,000c um of dirt that will be removed to create two, three-lane tunnels as part of the $1.4 billion project to link west-bound State Highway 16 and the dead-end SH20.

Others simply whack at the face, handily marked "north bound" in bright blue spraypaint, with handheld tools as they prepare the site for when a $54 million tunnel boring machine is switched on in October.

Vatuvei (a distant cousin to Warriors star Manu Vatuvei) is enthralled by the massive job.

"I love starting things off and helping see them through to the end," he says.

"There's plenty of action around here and everything's changing so quickly as we get ready to bore those tunnels."

Tommy Parker, Auckland and Northland state highways manager for the New Zealand Transport Agency, says 24,000 pre-cast segments are being prepared in an East Tamaki factory for the German-built boring machine, which will install the tunnel walls as it bores.

Its 4.8km return journey will take two years, but the portion of the motorway dipping underground only accounts for half the distance the connection will cover. It will total 5km when finished.

North of the tunnel face, workers are preparing the Waterview side for a cut and cover tunnel entrance and Spaghetti Junction-style interchange with SH16, the Northwestern Motorway.

Watching the workers below, part of a force of 350 that will eventually rise to 750, Parker shares the awe many feel when reflecting on the scale of the project, the biggest transport-related public works project since the Auckland Harbour Bridge was built in the 1950s.

"It's a different scale from anything we've done in New Zealand. You see this kind of thing in London," he says. "Everything about this project is big.

TBM drill
The Tunnel Boring Machine (TBM), built in China by German company Herrenknecht, is an Earth Pressure Balance Machine. This means the drill can tunnel under the surface at shallow depths, maintaining the pressure in the ground and preventing subsidence - essential when working under residential and commercial areas