Northland storm: State highway repair bill $5.9m, excluding clearing slips on Mangamukas

The biggest slip on the Mangamukas is near the bottom of the gorge on the northern side. The hillside under the road has fallen away.

A decision on when to re-open State Highway 1 through the Mangamuka Gorge to light vehicles will be worked on through this week as efforts continue to clear two slips that blocked the road during the recent storm.

However, it will be while before the road is open to trucks and buses, with the repair bill to be on top of the $5.9 million it is expected to cost to repair other state highways after the storm.

Waka Kotahi NZ Transport Agency Northland System Manager Jacqui Hori-Hoult said there are two slips on the northern side of the gorge that are causing concern and the organisation wants to take a bit more time assessing them and its next steps as to the final repairs required.

"The weather has been good over the weekend and we're pleased to see these slips have stopped moving, so that's good progress," Hori-Hoult said.

"Most of the slips over the road have been cleared, although there are places where the road will be reduced to one lane. We are looking at when we can open the road to light vehicles from local communities so they can make essential journeys without having to go via a long detour."

She said once it's safe to do so, it could let locals through in convoys at set times of day, but the road won't be open to trucks and buses for a while.

For now, SH1 through the Mangamuka Gorge is closed between Victoria Valley Rd and Makene Rd. SH10 is the detour with motorists advised to allow an extra 20-30 minutes for their journey.

Hori-Hoult said the biggest slip was near the bottom of the gorge on the northern side.

The hillside under the road has fallen away. The second slip hasn't fallen away, but it's caused the road to slump significantly. Trees close to the roadside appear to be holding the slip in place for now.

"Both slips are challenging repair jobs so we can't just rush into it. We need to have enough safe room for vehicles away from the slip face to be able to travel past the slip," she said.

An aerial views of one of the slips keeping SH1 through the Mangamuka Gorge closed for further inspection and assessment.

Elsewhere in Northland, road maintenance crews have been tidying up after heavy rain last weekend caused slips and flooding that closed many state highways in the region.

The estimated cost of storm response and repairs to date is $5.9 million. This does not include the final repair costs for the Mangamuka Gorge that we are working on, Hori-Hoult said.

Repairs are under way on SH14 at Tangiteroria, where a slip under the road has reduced it to one lane. Stop/go traffic lights will likely remain in place until the weekend while road crews build up and reseal the road.