The Far North District Council has begun trialling five polymer compounds that it hopes will dramatically strengthen unsealed roads and suppress summer dust.

Trials began last week on nine of the district's busiest unsealed roads, with the emphasis on those heavily used by logging trucks.

The polymers, either in liquid or granule form, have been dug 200mm into the road gravel, where they will attract moisture, binding the loose gravel into a solid, resilient surface and locking in dust particles.

Each 2km stretch of road is testing four different polymers, involving about 22km in total. The testing regime ensures that each compound is trialled by the same traffic loads over the same road geology.


First to receive the treatment was Orakau Road, just south of Kaikohe. The others included Pipiwai and Diggers' Valley roads, both of which made headlines last summer because of choking road dust kicked up by logging trucks.

The council's general manager - infrastructure and asset management Jacqui Robson said the preference would be to seal the roads, but that could cost up to $300,000 per kilometre.

"Our 40,000 ratepayers simply can't afford to seal the district's 1600km of unsealed roads. That's why we are looking at cost-effective alternatives," she said.

The polymers had been used elsewhere in New Zealand and Australia to strengthen forestry roads, and had proven to reduce dust by as much as 80 per cent for up to three years.

"The Queensland and South Island environments are very different to ours. The Far North has a combination of heavy summer rains and comparatively soft road-building materials. This requires more road maintenance, and we also get more road dust," she said.

All five trial compounds had been confirmed as environmentally safe by both the Environment Protection Authority and the Northland Regional Council.

A decision on whether to deploy the technology across the district would be made when the trials were completed at the end of the coming summer.