Highway closure put to good use
Waka Kotahi / NZ Transport Agency is making the most of the closure of State Highway 1 through the Mangamuka Gorge to carry out extensive maintenance and repairs.
The route has been closed between Victoria Valley Road and Makene Rd since heavy rain caused slips and widespread flooding across Northland in mid-July, with a single slip keeping the road closed to all traffic.
Waka Kotahi Northland system manager Jacqui Hori-Hoult said last week the road could be open to one lane for light vehicles by late October, depending on the weather
A contract had been awarded to Fulton Hogan, as lead contractor, to manage construction of a wall of concrete piles across the slip face on the road’s centre line. The piles would support the road where up to 7000 cubic metres of rock and soil had fallen away, undermining the road.
Construction of the supporting wall is the first phase of work to reopen the road to two lanes. That first phase will take at least six to eight weeks depending on the weather.
“We’re dealing with a very challenging and complex slip in a difficult environment,” Hori-Hoult said.
“As well as repairing the slip below the road, we have to consider the options for restoring the road to two lanes. We can rebuild all of the road that’s been lost, or cut into the hillside with a new alignment. Our team is in that process at the moment.”
In planning the repair and maintenance work, Waka Kotahi had the safety of road crews as its top priority.
“We’ve found the ground is unstable both under and above the road, and the concern remains that any repair work could reactivate old landslips,” she said.
“The instability of the slip area has even caused us to close the road at times to the maintenance crews. It just wasn’t safe to move vehicles and equipment past the slip.
“There has been a lot of rain this winter but as the weather improves and the days become longer, we’re looking to progress the slip repair so we can get the road open.”
Local hapu¯ and iwi have led karakia at the slip site for the safety of workers and contractors who were preparing to start work this week, Hori-Hoult saying Maungataniwha had great significance to many iwi/ hapu¯ in the North.
Meanwhile, SH1 through the gorge had been getting some special maintenance attention.
“While the road is closed maintenance crews have been hard at work, repairing the road, replacing roadside guard rails, drainage maintenance and generally tidying up the roadside,” Hori-Hoult added.
“Usually we would have to close the road or have stop/go traffic managers in place to do this work safely, or we would schedule it around resealing and other work.
“Waka Kotahi is very pleased to use this opportunity to make safety and resilience improvements. Motorists will certainly notice the difference when the road reopens.”
She acknowledged the disruption and the extra time and cost involved in having to travel on SH10 as a detour.
“We thank motorists for their patience and understanding,” she said. “We’re working as quickly as possible in difficult conditions to repair and reopen the road.”