Leaking expressway requires repairs
Water is seeping through the seal on the $630 million Kapiti expressway, meaning it will have to be repaired within months of opening.
The New Zealand Transport Agency confirmed in June that remedial work would be needed to address ‘‘pavement issues’’ on the 18-kilometre expressway north of Wellington, but at the time was unable to say why.
On Tuesday it said tests on road samples had shown the problem appeared to be caused by water seeping through the membrane seal, which is meant to act as a waterproofing layer below the asphalt.
The problem has occurred along just over one kilometre in the southbound lane, and about 260 metres in the northbound lane, in the vicinity of the Kapiti Rd junction.
Agency highway manager Chris Hunt said repair work would be done later this year or early next year, though it was unclear what the work would involve, or what it would cost.
‘‘Until we are able to identify what the remedial work will be, we cannot confirm how long it will take. But it is likely that the work will be carried out off-peak and staged to minimise the disruption to motorists.’’
The failure of the road’s waterproofing materials at the problem areas had led to discoloration and the loosening of fine particles, Hunt said.
While the road would continue to be closely monitored, the issues did not pose any risk to motorists.
The agency used a porous asphalt to cover the road surface, which was considered the most appropriate for the conditions.
‘‘We are still working with our technical experts to find out how water managed to penetrate the seal.’’
It was not uncommon for remedial work to be needed on newly-opened highways, but the issues on the expressway were unexpected, Hunt said.
The first section of the expressway was officially opened on February 24.
AA road safety spokesman Dylan Thomsen said the issue was affecting only a small part of the expressway and was not having any impact on motorists.
‘‘Ideally, in any major project, you want to everything to go absolutely perfectly, but that almost never happens.’’
Kapiti Mayor K Gurunathan said while the issue was unexpected, he welcomed the NZTA’s proactive response.