Hot weather creates ‘bitumen bleed’ in city

Roading authorities have been left with a sticky mess, and a bill for repairs, after two days of soaring temperatures in Dunedin.

Dunedin City Council staff yesterday confirmed contractors had spread 50 tonnes of grit on city streets after roads began melting earlier this week, as temperatures topped 28degC on Monday and 32degC on Tuesday.

Council transport delivery manager Josh von Pein said nine roads were treated for "bitumen bleeding" — where heat caused the bitumen to melt — over the two days.

Two of them, George King Memorial Dr near Outram and a section of the recently resealed George St, near the Duke St intersection, would need further repairs, Mr von Pein said.

George King Memorial Dr had been damaged by heavy vehicles riding over the melting surface, while vehicle movements "may have" also damaged the melting section of George St, he said.

The extra grit cost about $5000 but the cost of more extensive repairs, to be covered by the council’s road maintenance budget, was not yet known. The council’s contractors had been inspecting roads for bitumen bleeding, and responding to reports from the public, as the hot weather set in.

Mr von Pein said some issues were "normal" at this time of year.

"The type of bitumen used on Dunedin roads is chosen because it performs well in colder temperatures. This means when it is very hot we may start to get bleeding," he said.

NZ Transport Agency network manager Chris Harris said State Highway 1 was affected in five locations around Dunedin, including on the Northern Motorway, while sections of SH87 melted in Mosgiel and near Outram.

Maintenance crews spread grit and used water carts to cool roads around the city, and recent rain  had helped reduce road temperatures across Dunedin and Otago, he said.

chris.morris@odt.co.nz

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