Waka Kotahi claims the multi-million dollar Pūhoi to Warkworth motorway is resilient and safe despite needing a major patch-up just a month after opening due to a landslide that is still moving.
It is a problem the Transport Agency knew about before the ribbon was even cut on the $880 million project.
Cracks have appeared in concrete barriers after recent storms reactivated a known slip. Reports obtained by RNZ show the earth is moving towards the carriageway at a stop-start rate at times exceeding 30cm a week.
Yet Waka Kotahi general manager of transport services Brett Gliddon said it was not a major problem.
"I've got full confidence that the road is resilient and safe."
One site where there was deep-seated movement happening was currently being fixed and that was due to be completed by October, he said. Once that was completed all the work on the road would be done, Gliddon said.
The builder commissioned a 300 page report which investigated all the slip sites across the whole project to understand the risk profile and to be confident the road would be resilient, he said.
The report picked up two areas of concern and this was one of them, he said.
The landslide area shown in a Waka Kotahi report, marked onto a drone image of the Pūhoi to Warkworth highway, which was captured in January 2023 by NX2. Photo: Supplied/ Waka Kotahi/ NX2
"Another one was another site where there was a drain that had been cut, that site got fixed."
The builder told Waka Kotahi that there was a fix available and there was no risk to the road which could be reopened while the work was done, he said. It was a very unstable part of the country, Gliddon added.
"So it's not a matter of picking the road up and moving it 50 metres to one side to avoid it because you just open up a whole lot more problems.
"That's proven by looking at the existing road, so the existing road has had numerous slips in the last 12 months because of the geology through this area. So it's not a simple matter of just avoiding it."
Gliddon rejected that Waka Kotahi had built an $800m motorway on land it knew to be unstable saying it was built in very challenging country, as occurred elsewhere in New Zealand.
"We built it to very high standards and we're confident it's incredibly resilient."
The land had to be treated to ensure it met the design standards and that was now being done. Piles were being put in to stop the movement on that part of the highway, which would make it a much more robust design, he said.
"We're confident that will hold it in place."
Gliddon said Waka Kotahi stood by the fact that it was a resilient road and the remedial work to repair it had started before it was open.
Meanwhile, Transport Minister David Parker said he was waiting to find out more from Waka Kotahi.
"I certainly have asked for an urgent briefing, but I've done that this morning and I haven't yet received it. If the transport authorities thought the road wasn't safe to drive on at the moment they would have closed it."
Waka Kotahi has said concrete barriers and a temporary traffic management plan were in place to ensure the landslide posed no risk to road users.
Auckland mayor Wayne Brown said the $880m spent on the project could have been better spent.
"I'm very critical of that whole expenditure, it was a mistake in the first place for that money they could have three lanes all the way to Whangarei - now we find it's got a landslide."
MP for the area, Chris Penk, said the communication about the land instability had been lacking.
"I'm a bit surprised that this has now arisen following the grand opening in which it clearly wasn't communicated to the prime minister or myself as local MP or probably a lot of other people who would have been quite interested."
