No roading short-cuts for Kaipara

 

Recently there have been some serious questions asked of council regarding the conditions of Kaipara roads, especially in the outer reaches, where both wet and dry weather can be the cause of considerable chagrin.

Sub-structure of the Kaipara is unlike most other parts of the country and though there are options for short-term relief nothing has yet proved more than just a band-aid. The New Zealand Transport Agency (NZTA) funded mainly southern local authorities in New Zealand, trialling a sealing technique from 2004 that promised short-term value in being, by reputation, more costly initially but offering longer term, low maintenance costs while also being environmentally friendly in regard to dust prevention or control.

Otta Seal was developed in Norway in the 1960s as a cheaper form of road sealing, named after the Otta Valley where it was first trialled. It creates a surface which stops dust and reduces potholes and corrugations, but uses much cheaper materials and involves very little preparation, engineering or safety improvements. The roads are still classed as being unsealed as they haven’t been engineered for the kind of speeds of a sealed road, but the cost is about 10 per cent of traditional sealing.

While it exceeded expectations in some areas, Whangarei trialled the method in three locations in 2011 and found it was not suited to the high rain volumes and clay soils of Northland. This view was endorsed by Henri van Zyl, Kaipara District Council roading manager who said “It works well for low traffic volumes with a good support layer under it. We have low volumes but not good support layers so is not really a viable option for our network and soil conditions.”

In the North, Gravel Lock has also been tried on a variety of surfaces and while it has been seen an advantage on some, its use on forestry roads with extreme dust problems has proved only short term, cancelled out by constant hammering from logging trucks or other heavy machinery.

Consequently given the number of metal roads in the Kaipara there is no immediate or simple, cost-effective solution.

By Rob Pooley