Prime Minister, Rt Hon Chris Hipkins and Associate Minister of Transport, Hon Kiri Allan, to mark the completion of the Pūhoi to Warkworth section of Ara Tūhono, and Te Honohono ki Tai Road in Warkworth.
Transport Minister David Parker has received assurance from officials that the new $880 million Ara-Tūhono Pūhoi to Warkworth motorway north of Auckland is safe.
This followed revelations the Auckland Anniversary floods had reactivated a landslide on the motorway that was only opened to motorists last month.
Parker’s office issued a statement to the Herald this morning saying the minister had received a briefing from Waka Kotahi/NZ Transport on the matter.
“It provides assurance that the road is safe and that remediation work is ongoing,” the statement said.
Work on the landslide along Ara-Tūhono - Pūhoi to Warkworth motorway. Photo / Waka Kotahi
Yesterday, Parker said the landslide “could potentially be a safety risk for motorists”.
Cracks have now appeared in concrete barriers, and an entire section may be moving under the Pūhoi-to-Warkworth motorway.
Waka Kotahi group general manager transport services Brett Gliddon yesterday said significant work has been done on a long-term design solution for the slip at the northern end of the 18.5km motorway and is expected to be completed by October.
“In the interim, while works at this location are ongoing, concrete barriers are in place and a temporary traffic management plan has been instituted. These measures are in place to provide added assurance that these works will not pose any risk to people using the motorway,” he said.
Since the motorway opened on June 19 and until work is completed on the landslide, there is a 70km/h speed limit through a short section of the motorway around the landslide.
Transport Minister David Parker. Photo / NZME
Gliddon said the road had been built through an area with challenging geology, and had a history of slips and land movements, which meant it had been designed and built taking these issues into account. It was also the reason detailed reports had been commissioned to identify potential risks, he said.
Waka Kotahi said the unstable material at the face of the slope of the landslide has been removed and replaced with engineered material and drainage, subject to stringent and detailed design, engineering, and approval processes.
The landslide comes as documents have surfaced showing Waka Kotahi has known for years the land in the area is unstable but thought the motorway would bypass it.
Instead, till-now undisclosed reports reveal the entire 18.5km-long project was beset by landslides for years, and the recent storms have made it worse, especially at one spot - an unstable slope above a stretch of about 200m of motorway by Mahurangi Bridge, near Warkworth.
It appeared “a pre-historical and deep-seated landslide has been reactivated” by January’s massive rainfall, said a report released to RNZ on Monday under the Official Information Act (OIA).
The “slope has experienced another landslide and is moving towards the carriageway” at a stop-start rate of sometimes more than 30cm a week, the 20-page external engineer’s report to the agency said.
Ara Tuhono Puhoi to Warkworth motorway. Photo / Supplied
“Cracks have been reported in concrete barriers in two separate places on the western side of the carriageway.
“There is the potential that some landslide movement is occurring across the full width of the carriageway.”
This - and a second, 300-page report that revealed a risk from rockfalls - had forced emergency repairs at a road touted at its June opening by Prime Minister Chris Hipkins (from under a large umbrella) as a key to unlock the north, and by Waka Kotahi as a “safer, more resilient and reliable route”.
The 300-page investigation in April, also newly released under the OIA, said the motorway construction project had been dealing with 19 landslides by late 2019.
“Slope failures continued to occur into late 2022, some of which are either under repair, or remedial work designs are yet to be confirmed,” it said.
A second slope, 30m long by 4m wide, had also been cut too steep, and landslips hit this section during heavy rain in July 2022 and January 2023. The cut had to be flattened out, the transport agency said.
Waka Kotahi said an independent reviewer, Aurecon, who has been appointed to ensure more than 100 safety and quality tests are met, has been monitoring the movement of the cut slope and this element of the project will not be certified until the slope has been stabilised.
