Oil will no longer be used by the Central Otago District
Council to suppress dust from gravel roads.
An international method of sealing will instead be
implemented throughout the district over the next three
Central Otago residents have previously raised concerns about
the safety, cost and effectiveness of oiling.
A resolution to implement Otta sealing to replace oiling was
passed at a CODC roading subcommittee meeting in Alexandra
The CODC resolved to phase out oiling of gravel roads over
three years, and instead use the Otta method, which
originated in Norway after it was first used on gravel roads
in the Otta Valley. Otta sealing is a 16-30mm-thick mixture
of bitumen and crushed rock.
In a report to the group, CODC roading manager Julie Muir
recommended Otta sealing be funded as part of the council's
New Zealand Transport Agency-subsidised district roading
programme, with the local share of funding being provided
from an existing unsubsidised seal extension budget.
Otta sealing would cost an estimated $3500 per 100m of road,
although costs varied depending on the amount done at once,
Otta was deemed safer, more environmentally acceptable, and
of better long-term quality than oiling.
In 2008, the council received 41 requests to oil roads and
four requests to seal short sections of road.
Just over 20 complaints resulting from oiling were received
by the council and Fulton Hogan Central during the year.
Trials throughout Central Otago proved Otta seal lasted five
years, making it more cost-effective than oil in the long
In her report, Ms Muir said Otta seal would have to be
replaced after less than three years to make it more
expensive than oiling, which was a worst-case scenario.
This week's meeting adjourned for a site visit to roads on
which Otta seal could be used, and had been trialled,
throughout the district. Ms Muir showed subcommittee members
gravel roads around Galloway and the Ida Valley, where issues
of dust suppression were apparent, and trial Otta-sealed
roads of the area in comparison.
When the meeting resumed, subcommittee members approved Ms
Muir's recommendations to phase out oiling in favour of Otta
Otta sealing will be undertaken when it can coincide with
metalling programmes and other roading upgrades in the area.