Work starts on first big tunnels for 30 years

Tunnel workers watch as the machine starts its journey through 300m of rock. Pictures / Kenny Rodger

Rock was broken yesterday in the first big road-tunnel project in 30 years - the $365 million tolled motorway extension north of Auckland.

A 50-tonne boring machine called a road-header raised a cloud of dust but little noise as it began drilling the first portal of a set of 340m twin tunnels through Johnstones Hill at the northern end of the 7.5km extension from Orewa to just before Puhoi.

Powered by electricity and high-tech guidance equipment, the imported machine will take a year to chew through 60,000cu m of rock, to be used as foundation material for an interchange between the motorway and the Hibiscus Coast highway.

The two tunnels, 15m apart but with emergency connection chambers, will eventually be linked to a sweeping 537m viaduct which Transit New Zealand and its construction partners are building above the Waiwera River.

Transit's initial plan was to carve 60m out of a bushclad saddle of Johnstones Hill, on the distinctive ridge between Waiwera and Puhoi, to the dismay of environmentalists concerned about the cutting of an important wildlife corridor.

But chief executive Rick van Barneveld said gaining Government approval to toll the motorway had allowed his agency to design a much better project, from engineering and environmental standpoints.

This would offer not only better protection to what was considered a critical ecosystem, but also a superior connection between the motorway and the existing State Highway 1.

"I think these twin tunnels will be a spectacular entrance to Auckland, they will be fit for purpose and will lead to a better fit to our Waiwera viaduct," Mr van Barneveld said.

He said the motorway extension was not only the country's largest single roading project, but it included the first serious tunnelling component since Wellington's Terrace Tunnel was built in the mid-1970s.

Unlike that tunnel, which was also supposed to have a twin but ended up as a single structure with traffic running in both directions, "we are certainly not going to leave this one half-finished".

But despite his confidence in completing the motorway extension without any more budget blowouts, Mr van Barneveld warned that there was no more money on the horizon to improve State Highway 1 further north to Wellsford.

There would be no provision in Transit's draft 10-year state highway forecast, which is due to be issued tomorrow for public submissions, to widen the road past Puhoi to four lanes.

"These are issues of not just local but regional and national significance as we tackle our highway network and the need for it to provide support for a country that wants to rank in the OECD in terms of our economic wellbeing."

Yesterday's tunnel launch was preceded by dawn blessings by Ngati Whatua elders, who lit fires on both sides of Johnstones Hill seeking spiritual protection for workers involved in the project.

Project director Robert Jones said the first 12 months of motorway construction had been completed without a single lost-time injury accident.