Ngaio Gorge Road strengthening work

More major strengthening work is being done in Ngaio Gorge Road from late March to late November 2017 to make this key transport route stronger and more resilient.

Strengthening work on Ngaio Gorge

Strengthening work in Ngaio Gorge

Resize

A new 42-metre-long retaining wall is being built below the road about half way up the gorge.

The wall is the latest in a series of projects designed to protect the road and reduce the likelihood of slips occurring in major earthquakes and storms.

Why we are doing this work

The gorge road is an essential access route linking Wellington City to the north which is why we have been progressively strengthening vulnerable sections of it in stages since 2001.

It is part of our ongoing programme to strengthen key structures and transport routes and make the city more resilient.

What to expect

The road will operate as usual at peak times, but people driving should expect short delays during the day.

Between 9am and 4pm, Monday to Friday, traffic will be reduced to one lane around the Ngaio Gorge Road work site. This section of road will also be down to one lane most Saturdays between 8am and 4pm.

Temporary traffic lights and traffic management will be in place.

Safe access for pedestrians will be provided at all times.

What we are doing

  • Constructing a new retaining wall
  • Replacing and widening a narrow section of footpath at the top
  • Installing new pedestrian safety barriers
  • Repositioning two street light poles

The new wall will have 23 long concrete piles up to 19 metres deep. A drilling rig on a truck will be used to drill the holes for the piles. The piles will be poured and constructed on site.

The wall will then be anchored to the hillside using long steel rods that will extend into the rock under the road.

The previous eight road strengthening projects in the gorge have involved upgrading or replacing old retaining walls in vulnerable spots. This latest one is being built to support a section of road that has not previously been reinforced. Two more new sections of wall are planned further up the hill and expected to be built over the next few years.

Timeframes

  • Preliminary work began in late March
  • Work in full swing from 3 April
  • Work expected to be complete by late November 2017

Cost

The planning and construction of the wall is costing about $1.6 million.