New wall will make Ngaio route more resilient

31 March 2017

Work getting under way next week in Ngaio Gorge will make another section of this key transport route stronger and more resilient.

Strengthening work on Ngaio Gorge

Pile drilling on a Ngaio Gorge wall upgraded in 2010

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Over the next eight months, a new 42-metre-long retaining wall will be built below the road about half way up the gorge.

Wellington City Council’s Portfolio Leader for Transport Strategy and Operations, Councillor Chris Calvi-Freeman, says the $1.6 million reinforced concrete 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. 

“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,” he says.

“The work is part of the Council’s ongoing programme to strengthen key structures and transport routes and make the city more resilient.”

Two traffic lanes will be open as usual at peak times, but traffic will be reduced to one lane around the Ngaio Gorge Road work sites between 9am and 4pm, Monday to Friday, and on Saturdays between 8am and 4pm.  

Temporary traffic lights and traffic management will be in place, so people driving should expect short delays during the day. Safe access for pedestrians will be provided at all times.

Cr Calvi-Freeman says much of the work done in the gorge so far has involved replacing or significantly upgrading existing sections of retaining wall.

“In this latest project, a new wall will be installed in a spot where there is no existing reinforcing,” he says.

“About 23 concrete piles up to 19 metres deep will be drilled and constructed on site as part of the work. The wall will then be anchored to the hillside using long steel rods that will extend into the rock under the road.”

A narrow section of footpath at the top will be replaced and widened as part of the job, and new pedestrian safety barriers will also be installed.

The new wall is being constructed by contractor Juno Civil to a design by Opus International Consultants.

The contractors have been setting up and doing some preliminary work this week. Work is expected to be in full swing from Monday 3 April and is expected to be complete by the end of November.

The new wall won’t be the last in the gorge. Two more walls are planned further up the hill and are expected to be built over the next few years.