Ngaio Gorge stabilisation

We are strengthening and stabilising the Ngaio Gorge slip to make this key transport route stronger and more resilient. The road will be down to one lane during construction, controlled by traffic signals.


About the project

As part of the Council’s programme of work to improve safety and accessibility of major transport routes we are committed to fixing the Ngaio Gorge slip.

Construction work is scheduled to get underway from 12 October 2020 and will give priority to the construction of three retaining walls to realign the road. Once that is completed the Council is to continue stabilising the lower and upper slip sites and remove the concrete barriers and shipping containers.

The project cost is $11m including professional fees.

Impact on traffic and residents

The road will be down to one lane for the duration of the construction and will be controlled by traffic signals.

There will be impacts on traffic while the work is underway. We will monitor traffic flows, particularly during the morning and evening commuter peaks to minimise the impact on people’s journey times.

Work hours

Crews will be working between 7am to 6pm, Monday to Saturday from 12 October 2020 until October 2022.

Alternative routes

We encourage people to use alternative routes such as the Ngauranga Gorge or Onslow Road to help ease congestion during busy times.

There are good options for public transport in this area. Please check Metlink timetable for options.


Cyclists will be most affected in the early stage of the project when they are travelling uphill. Safety has to be the number one priority so we will need cyclists to dismount and push their bike through the pedestrian areas of the site, particularly when travelling uphill.

Trelissick Park users

Trelissick Park will remain open during this time. The upper entrance at Trelissick Park will remain open during the project. Later on - the lower site entrance will open.

Parking for people going for a walk in the area will not be available closer to the site to ensure safe passage for pedestrians and vehicles passing through.


Pedestrian access will be provided throughout the project period.

Environmental considerations

An Environmental management plan has been developed to avoid contaminant into the stream below.

Also we have a Lizard Management Plan in place with the Department of Conservation to ensure safe relocation of all lizards in the area.

More information

If you have any questions about the Ngaio Gorge Slope Stabilisation Project please call 04 499 4444 or email us at