State Highway 10 north of Kaeo has reopened in both directions after a five-metre deep tomo that opened up in the road was repaired.

Waka Kotahi NZ Transport Agency said SH10 north of Kaeo was reopened to traffic over the weekend after temporary repairs to a large hole found under the road surface last week.

The hole in the southbound lane, just over a kilometre south of Totara North Rd, was found to be a tomo or cavity caused by a buildup of water underground, Waka Kotahi Northland System Manager Jacqui Hori-Hoult said.

"What looked like a small hole not much bigger than a pothole in the road was in fact a cavity about two metres wide and five metres deep.

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"Our crews have worked hard over the week to work out how to fix the problem while keeping disruption to road users to a minimum."

She said the cavity was over a broken culvert that ran across the road more than five metres below the surface. A complicating factor for the repair crew was a fibre optic cable running along the roadside and very close to the hole about three metres underground.

"We've decided against trying to repair the culvert, so we have filled in the tomo and reopened the road for now. We'll be back (this week) to install a new culvert about 50 metres long and five or six metres underground. We can do that by forcing the pipe through the ground rather than doing a major excavation," Hori-Hoult said.

"We estimate that it will take about five days, weather permitting, to complete the work with one lane closed while workers are on site with stop/go traffic management in place."
She said the tomo repair may settle a little in the road but maintenance crews will monitor and fill only if necessary.

Motorists should take care passing the site, keep to the temporary speed limit and watch out for workers on the roadside.