Bad asphalt slows wheels of progress
Air pockets force four-lane expressway to be ripped up
The opening date for a longawaited expressway north of Wellington is getting “uncomfortably close to the holiday season” because of faulty asphalt, the NZ Herald can reveal.
Thousands of tonnes of asphalt has already been ripped up after problematic pockets of air were discovered in the four-lane Peka Peka to Ō taki motorway, documents released under the Official Information Act show.
One option under consideration to get the road open before Christmas is to allow traffic on the paving base layers, with a temporary speed limit and increased police monitoring.
The road’s opening has already been on a knife-edge this year between Covid-19, supply chain issues, and wet weather.
A bypass of Ō taki, the road will join up with the existing Kāpiti expressway to the south and eventually the planned Ō taki to north of Levin expressway.
The roads, along with the newly opened Transmission Gully motorway, form Wellington’s northern corridor.
A Waka Kotahi NZ Transport Agency memo from August 2, released to National’s transport spokesman Simeon Brown, outlined “a number of quality issues” facing the Peka Peka to Ō taki stretch.
Brown said the Government needed to be upfront about whether the road will be able to open before Christmas.
“The Government spent months trying to blame pavement issues on the former National Government when it came to delays in opening Transmission Gully, but is now facing similar issues of its own with thousands of tonnes of faulty pavement needing to be replaced.”
Fletcher Construction, the company building the road, identified problems with almost 13,000 tonnes of asphalt during quality testing.
Air voids outside of the design range were found in about 7900 tonnes. This problem can damage the asphalt under traffic, leading to early failure of the road.
Fletcher Construction proposed a fix which would allow the asphalt to be retained instead of ripping it up and starting again, but this was not approved.
“While Waka Kotahi’s SME’s concur that any decision to remove and replace the non-compliant material should not be taken lightly for reasons of wastage, consumption of non-renewable materials, extra carbon emissions etc., they also agree that the potential risks are tangible and should not simply be overlooked”, the memo said.
Waka Kotahi regional infrastructure delivery manager Jetesh Bhula told the NZ Herald they expected all of this material to be removed and replaced by the end of this week, depending on the weather.
“The material is likely to be used in the production of asphalt paving for future works outside of the PP2Ō Expressway.”
The remaining 5000 tonnes of asphalt wasn’t the correct thickness.
But Bhula believed this problem could be resolved without removing the material.
“The designers are investigating deepening the top layer of asphalt to account for the slightly reduced thickness in the bottom two asphalt layers.”
A Fletcher Building spokesperson said their priority was to construct the highest quality and safest roads possible, which involved regular quality assurance testing.
“Our process of testing picked up that the pavement quality wasn’t at the standard we expect. We shared this with our client and have been working together to remediate the issue.”
A key risk identified in the memo was the expressway not opening before the end of the year due to the disruption caused by the remedial work.
“The current programme (including remedials) is showing an early December ‘22 opening which is getting uncomfortably close to the holiday season.”
Bhula said the contractor’s programme was currently showing a mid-December opening, which was dependent on weather, staff absenteeism due to Covid-19 and winter illness, and any unforeseen circumstances. Should the programme slip further, one option to consider was opening the expressway on the base layers of the road paving, the memo said. Bhula said if this were to happen, they would need to carefully assess the condition of the surface from a health and safety perspective.
“In particular, we’d need to ensure the texture and skid resistance of the road surface provide an effective ‘braking surface’ for vehicles, particularly in heavy rain.”
If not, Waka Kotahi would need to look at temporary reduced speed limits for the road and work closely with police to make sure they were followed, Bhula said.
A spokesperson for Transport Minister Michael Wood’s office said the Minister has been advised Waka Kotahi was still working towards the road opening before the end of this year.
“We are confident the construction team appreciate how much the road is valued by local communities and broader Wellington residents and are doing all they can to complete construction.”
The 13km, four-lane expressway, which started construction in 2017, was meant to open in 2020.