Job properly done saves millions in airport repairs

Tenders will soon be called to upgrade the runway surfaces at Whanganui's airport. Photo/Bevan Conley.

Getting the job done properly eight years ago has saved the Whanganui District Council several million dollars keeping the city's airport runway up to scratch.

The council will soon go to tender for some resealing work but, because the 2008 sealing has been so successful, major work to that scale probably won't be needed for another six to 10 years.

The scope of the upgrade includes applying a binder coat to the seal on the main runway, the taxiway and the apron in front of the terminal.

Airport manager Alan MacGibbon said the job was estimated to cost between $200,000-$250,000.

He said the council had $260,000 included in its Annual Plan for the job while the Ministry of Transport, a joint venture partner in the airport, had already approved its 50 per cent contribution for the job.

The work is a one-day operation involving application of a very thin binder coating followed by remarking all the important marking.

"Before the work is done we'll remove lichen, repair some cracks and repair an area where we have some surface bitumen bleed occurring. We'll also do friction tests to ensure the coat doesn't reduce the braking effect. All of this will be included in the total project."

Mr MacGibbon said a complete reseal was done in 2008 and that involved a triple coating of chip seal on the runway.

"That was expected to give us at least 10 years' service with a rejuvenation after five years but that triple seal was so successful we didn't need the rejuvenation in 2013," he said.

However, he said annual inspections indicated an upgrade should happen about now.
The reseal will involve that binder coat, which binds in the top surface and provides extended UV protection.

"UV is a major killer of bitumen, and that's why we used a sand coat as the third coat of that triple seal done in 2008. The binding effect reduces debris and also waterproofs the surface."

Mr MacGibbon said the new seal should extend the life of the runway surface for up to 10 years, which moves the need and cost of a full reseal out to around 2022-27.
"This is a very good result. It may even be an option again down the track, as the upper layers of the seal are where the decay occurs. The lower surfaces are showing no sign of collapse at this time."

A full triple-coat reseal is estimated to cost between $1million and $1.5m and well over $2m for an asphaltic concrete treatment.

"So, for around $1.2 million from the 2008 sealing, we will have got well over 15 years of service using the methodologies we have compared to the more traditional approach, which would likely have cost $2.5 million to $3 million over the same period," he said.
Expressions of interest in the work close on December 1.