An $11m project to strengthen and stabilise the Ngaio Gorge slip starts on Monday 12 October.

The work will see a permanent solution for stabilising and reinforcing the slip areas in Ngaio Gorge following the July 2017 landslides. The two-lane road will revert to one lane at the slip site, which will be controlled by traffic signals.

Wellington Mayor Andy Foster says the work is expected to take up to two years to remove loose material and stabilise the latest slip to make the key transport route between Ngaio and Wellington city more resilient.

“I know this work, will at times, be inconvenient for drivers, cyclists and pedestrians, who need to travel on Ngaio Gorge Road. But I ask people to be patient, and if possible to use Ngauranga Gorge or Onslow Road or public transport to help ease congestion, while we deliver this long-term solution for this vital arterial road.

“Construction will initially involve building three retaining walls to widen and realign the road, this is expected to take about a year to complete.

“Once that is finished, stabilisation (securing the area’s rock bluffs) of the lower and upper slip sites will be completed and the concrete barriers and shipping containers will be removed.”

In addition to being a primary access road, Ngaio Gorge is also a critical route for the city if Ngauranga Gorge ever becomes blocked to traffic.

“Like any city roading project, 51% of the $11m comes from the NZTA and 49% from Wellington City Council. This is another significant investment in our city’s resilience and core infrastructure,” says Mayor Foster.

Council Transport Infrastructure portfolio leader, Councillor Jenny Condie, says the first job the construction team will tackle is removing lizards along the banks of Ngaio Gorge and rehoming them in Trelissick Park.

“We’ve been waiting for lizards to come out of hibernation, now that they are awake we can start moving them out of harm’s way before we start on this critical project.

“Working with the Department of Conservation, we’ve implemented a Lizard Management Plan that will involve checking all the vegetation on the work site for lizards. Each lizard will be captured individually in breathable cloth bags and transferred across the road to their new home in Trelissick Park.

“It will take 3-4 days to complete this inspection and relocate any lizards found.”

Construction crews will be working in Ngaio Gorge between 7am and 6pm, Monday to Saturday, from Monday 12 October until October 2022.

For more information about the Ngaio Gorge stabilisation work, please visit wellington.govt.nz/ngaio-gorge.

Ngaio Gorge Project of Works Since July 2017 to September 2020

• Slips happened in July 2017
• Road closed for traffic
• Inspection of all slope areas in Ngaio Gorge Road and condition assessment carried out
• Abseil Access used to bring down the loose soil and stones
• Installed survey points in two major slip areas and slope stability monitoring work continued
• Removal of debris and stones commenced
• Installed container wall at upper slip and concrete block wall at lower slip installed to secure and maintain slip area
• Road opened for traffic with speed restrictions, lane diversion, and temporary traffic management plan implemented and continued
• Engineering consultants undertake preliminary investigation
• Concept designs for 3 options developed
• Peer review undertaken against costs
• Peer review presented a more economic and environmentally acceptable option
• Final analysis completed, option and budget approved
• Road safety audit, wildlife, building, and resource consents approved
• Tender published, evaluations completed and tender awarded
• Work scheduled to commence March 2020 but delayed due to COVID-19 lockdown
• Rescheduled the project commencement to 12 October so as to manage lizard relocation that must be carried out in a dry season.

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