Two thirds of the roads in Kaipara District are unsealed. Pictured, senior asset manager Andy Brown.
Work has begun on Settlement Road.
Kaipara District Council has begun a pioneering unsealed road maintenance programme, which could provide lessons to Auckland Transport on how it treats Rodney roads.
Senior asset manager Andy Brown has spent his whole life working on roads from Cape Reinga to Invercargill and says the new programme will be a game-changer.
Traditional “blue metal” used on roads has been dispensed with in favour of an aggregate with a higher blend of clay and sand, which has superior binding properties.
Andy says the problem with blue metal is that it washes away and is susceptible to corrugation and pot holes.
“In the past, we would blanket spread aggregate onto the road, but when it rained it just washed away into paddocks,” Andy says.
The new blend is based on the findings of Dr Paige-Green, in South Africa, whose study of the strength of various aggregate blends has been making waves around the world.
Andy says Kaipara is fortunate to have four quarries with the right blend of material, which is yet another advantage over blue metal, which had to be carted from further afield, increasing costs.
The new blend was first tested in Arapahoe and was found to last three seasons before it deteriorated.
It will now be rolled out to the rest of the district with Settlement Road, between Mangawhai and Kaiwaka, being one of the first.
Andy says that in the dry summer months, some deterioration does occur, but it can be fixed with a grader without additional metal. He says the aggregate accumulates at the edge of the road and is recovered rather than being washed away, significantly reducing costs.
The aggregate also produces drastically less dust compared to Auckland roads. Andy says this is illustrated by the two ends of Cames Road, which crosses the regional boundary.
Despite the advantages, the new blend has suffered from a perception problem as the brown clay colour is often associated with a deteriorated road.
Kaipara maintenance and operation manager Aram Goes says blue metal may “look flash”, but the brown roads last longer and provide a smoother ride.
Kaipara’s unsealed road programme has been designed in conjunction with the Northland Transport Alliance (NTA) through an initiative named the “Unsealed Roads Centre of Excellence”. The Centre has taken a scientific approach to road maintenance.
Kaipara roads will be divided into 100-metre segments for the purpose of taking samples and modelling the lifespan of the road and necessary maintenance.
A hole is dug and the strata of the earth and road is investigated. Samples are sent to a lab to understand the road’s load bearing capability and how much pavement is needed.
“It may be that we need another 100mms of material for it to be strong enough. Metalling used to be done by gut feel, but now it is a structured process,” Andy says.
The modelling is also used to predict when the road will need maintaining, with the aim of undertaking works before it deteriorates and residents start complaining to Council.
Kaipara District has become the focal point for the new method of maintaining unsealed roads, thanks to an $8 million cash injection from the Government’s Provincial Growth Fund (PGF) in 2018, which enabled trials to begin.
The PGF funding required that 40 per cent would be spent on hiring local businesses.
As a result, local firms such as Huband Contractors, in Paparoa, and Kevin Reid Contracting, in Ruawai, have been able to upskill their staff in new areas of road maintenance.
“Local contractors have sometimes missed out on contracts because of Council requirements, but now they have a track record with us.”
In September, Andy and his colleagues will present the Council’s findings to the Road Engineering Association of Asia and Australasia conference. The NTA will also be assisting other local councils with its findings, including Auckland Transport, through the Road Efficiency Group (REG).