Cure for holes, dust may get road seal of approval

A Waipu invention could cure the summer dust nuisance and shuddering corrugations on Northland's 3036km of unsealed roads.

Gravel Lock NZ director Grant Lewis said the binding process his firm used to produce a hard-wearing unsealed road surface was under patent and the firm, set up two years ago, was expanding to fill orders from throughout New Zealand, the Pacific Islands, Australia, Peru and Iraq.

The process involves watering the road, spreading the binding additive on the surface and mixing it into the road to a depth of 150mm, then compacting it.

"We've done roads carrying 300 trucks a day and they have lasted 11 months without maintenance," Mr Lewis said.

The Far North District Council has tried Gravel Lock on Spains Rd at Awanui, and the company website quotes former council engineer Richard Green as saying it was the best dust-suppression product he had seen, with potential to remedy corrugations and potholing.

It's being tested by the Kaipara District Council on a 650m unsealed section of Tangowahine Valley Rd, which logging trucks and other heavy forestry vehicles substantially damaged in the past. Dust has been a nuisance on the road, with forest companies paying for a tanker to wet the road outside houses where the dust could be a potential health hazard.

The trial started in late October and the test strip is showing little wear despite constant use by logging trucks.

Kaipara roading manager Henri van Zyl said the focus of the trial was dust suppression, but the road would be monitored to compare the cost benefits between normal road maintenance and using the "relatively expensive" new process. If Gravel Lock proved viable it was likely to be be used to help residents with road dust problems.

"In most cases the residents would be expected to pay the council's share of the cost," Mr van Zyl said.

Using petroleum products, such as waste oil, to suppress dust was now discouraged.