Ngaio Gorge stabilisation

Major strengthening is happening in Ngaio Gorge to make this key transport route stronger and more resilient.

Updates

December 2019

The registration of interest for the physical works tender is now complete. Fourteen contractors registered their interest. Tenders close January 14th 2020 with physical works on site expected to start in March 2020.

Physical works include building retaining walls, widening and realigning the road, drainage and slope stabilisation. This work is expected to take two years.

This work will require temporary traffic management measures. Ngaio Gorge Road can remain open throughout the project, but at times will be down to one lane, controlled by traffic signals and manual stop go traffic management as required. This is a key resilience route so the project has been designed to keep the road open and minimise the impact on peoples' journeys, while maintaining a safe work environment for crews to work.

The container wall will remain on site until the slope stabilisation work begins.

October 2019

The project team are making good progress on the preparation work:

  • Preliminary designs complete.
  • Consents for planned works obtained from Greater Wellington Regional Council and Wellington City Council.
  • A wildlife permit has been received from the Department Of Conservation.
  • The Road Safety Audit for preliminary designs is complete and addresses all auditor and safety engineer's queries.
  • The Request of Interest (ROI) has been advertised on the Government Electronic Tenders Service (GETS) website inviting contractors to register for this construction work.
  • Stormwater investigations continue and we are liaising with Wellington Water for a stormwater discharge global consent.
  • Preliminary designs have been submitted to GNS Science for peer review and waiting for their report.
  • Final designs and preparation of the Request for Tender (RFT) continue.

August 2019 

With the geotechnical investigations, topographical survey and stabilisation works complete, the project team is currently working through the consenting process and developing final designs. We expect to be able to start construction work in November 2019, subject to receiving consent. 

April 2019 

From late April to the end of May 2019, specialist crews will be carrying out slope stabilising works (removal of loose rocks), surveying the slip zones and subsurface geotechnical investigations to develop geological & survey maps. A topographical survey of the road below will also be completed. 

Work hours

7am–6pm Monday to Saturday. 

Impact on traffic and residents 

There will be delays for traffic passing through the investigation area during the working hours and traffic management will be in place throughout this period. Buses will have access through the route.

Road closures 

It is anticipated there will be 5-7 days of road closures during off peak travel times (9am–4pm), starting 29th April. The walking tracks will also be closed during this time. In the event of unsuitable weather or other unforeseen circumstances, the start date may be delayed.

About the project

The Council plans stabilisation and reinforcement work in Ngaio Gorge to improve the safety and accessibility of the area following the landslides of July 2017. 

This work is part of the Council’s ongoing programme to strengthen important transport routes, and improve the safety and accessibility of Wellington’s wider transport infrastructure. 

Construction work is scheduled to get underway later in 2019 and will run through until October 2020. There will be impacts on traffic while the work is underway, but these will be communicated well in advance with necessary diversions put in place. 

What's being done

After careful consideration of multiple options the Council has decided on the following actions: 

  • Erecting three retaining walls along the edge of the new road alignment
  • realigning the road on both sites to provide space for the slope hazard mitigation work
  • implementing targeted slope hazard mitigation with scaling, anchors and mesh reinforcement as well as catch fences
  • removal of temporary shipping container wall.

Next steps

  • April–May 2019: Geotechnical ground investigation works
  • Mid-2019: The Council aims to select a main construction contractor