Road Sealing this Summer

17 November 2009

If you've ever wondered why summer seems to be the signal for street resurfacing to start in Wellington, there's a simple answer. "The reason for the timing is that summer means warm air and ground temperatures," says Infrastructure Customer Services and Communications Manager Trish Ubels.

Contractors working at Ngauranga Gorge

Contractors working at Ngauranga Gorge

"It's important we don't let the street foundations get wet to maintain the strength of the roads. We use asphalt and chipseal to resurface streets and we need dry and warm weather so the treatment adheres to the street surface. If roads are laid when the ground is cold, the treatment will harden and crack, and also result in severe chip loss following chipseal. This would allow water to penetrate the foundations and undermine the smoothness of the streets."

The need for warm temperatures means we only have a narrow window of opportunity and we are restricted to resurfacing streets from November to March.

Trish says she understands this timing is often not convenient for residents, so "we do our best to make sure people know of resurfacing work coming up in their area". A letter is sent out to residents a month before work starts, followed by another letter 48 hours before work is due to start. On major routes, work is advertised in newspapers and on the radio.

Our infrastructure team is responsible for maintaining streets, footpaths, kerbs and channels, among other things. Each year the team starts with an annual survey of every footpath and street in the city. The streets that have reached a certain level of condition are prioritised for treatment. This list is then sent to utility companies to see if they have any work planned on the same location for the next three years, and if none is planned, the street is entered into the final programme.

"Resurfacing the street is a bit like maintaining a house - it needs regular maintenance and is cyclic," says Trish. "A street surface normally lasts 10 years. If left untreated, the street surface will start to fail and in the long term cause major structural damage that is very expensive to rectify. Wellington has a total of 670 kilometres of street, and 60 to 70 kilometres of street need attention every year."

Before resurfacing, our staff visit the sites and carry out any structural repairs, including footpath and kerb and channels, in preparation, normally two to three months before resurfacing.

"If a patch in the street is in really bad shape, we dig it out, fill it with base material, compact it for strength, then cover it with asphaltic concrete," says Trish.

The type of resurfacing selected is quite a complex process. It takes into account traffic volumes, previous treatments, age, and the behaviour of the existing surface and location. Asphaltic concrete is generally used in the central business district, shopping centres, tight corners, cul-de-sacs and highly-stressed areas. The best-value engineering practice is always selected, balancing costs with benefits.

The resurfacing programme for 2009/10 will be finalised shortly and will be available on our website. You can also phone (04) 499 4444 to see if your road is due to be resealed. We do our best to keep to the programme, but the timing may change due to emergency repair work or other urgent jobs.