Mangamuka Gorge State Highway 1 set to open after major slips closed the highway for nearly a year. Video / Michael Cunningham
State Highway 1 will be open from Cape Reinga to the Bluff today for the first time in just under a year after massive slips cut off an entire section in the Far North.
The Mangamuka Gorge, south of Kaitaia, will be open to all vehicles - including trucks -following the 1-in-500-year-storm that forced its closure in mid-July 2020.
On Tuesday the 'Northern Advocate' visited the 20km stretch of highway over the Maungataniwha Ranges south of Kaitaia, where entire hillsides had fallen on to the road and caused the earth beneath to drop away.
Eight slips had to be removed with extensive piling, road realignment, and retaining walls built to make it safe for vehicles to travel through.
It means motorists wanting to use the main route between Whangārei and Kaitaia no longer need detour along SH10, adding at least 30 minutes to their journeys and loading more traffic on to the smaller highway.
Waka Kotahi NZ Transport Agency Northland system manager Jacqui Hori-Hoult said the scale of the job and time needed to do it had tested the community's patience.
"We know the detour route has significantly impacted travel times, especially for the freight industry," she said.
"It's been a big thing for our community, but it's been a really complex job. I don't think you realise the magnitude of the work until you get in there."
Northland was devastated by the July 17-18 storm which dumped 220mm of rain in just a few hours. There was extensive flooding and damage to infrastructure.
Jesse King and Eliza Chapman-Kete from the Mangamuka Dairy are looking forward to the opening of SH1 through the gorge. Photo / Jenny Ling
The highway through Mangamuka Gorge had been closed since then, opening only as a single-lane passage for light vehicle convoys during some long weekends.
Repairs included building five retaining walls, installing dozens of concrete piles, realigning the highway, resealing sections of the road, and planting native shrubs on hillsides.
The cost of the project had increased from an estimated $13.8m to a total of $16.2m.
Hori-Hoult said the project has been "complex and time-consuming". "It was under tough conditions that our team took on the challenge to restore this important connection.
Waka Kotahi's Jacqui Hori-Hoult thanked the community for their patience. Photo / Michael Cunningham
"As they worked, they needed to continually monitor the hillside to ensure there was no new earth movement.
"The geology across Northland can be really unstable, and a 1-in-500-year event makes it really difficult."
At the largest slip, about 7000cu m of material - about 875 truckloads - fell away beneath the road, leaving its surface unsupported to the centre line.
Contractors were still working in this area, putting the finishing touches on a 135m retaining wall, which had to be cut into the bank to restore it to two lanes.
The 200m stretch of road would remain closed to one lane with a traffic light system in place for at least a month.
Hori-Hoult said road users should drive carefully as the road alignment had changed and road shoulders had been reshaped.
After the retaining wall was finished, a mural designed by Ngāti Kuhu will be stencilled on.
Hori-Hoult would not be drawn on details of the design, but she said: "It's going to be magnificent."
Massive slips closed State Highway 1 through Mangamuka Gorge. Photo / supplied
A karakia for the northern side of the site was held on Tuesday morning, and a similar blessing was to take place this morning.
The opening of the road couldn't come soon enough for Mangamuka Dairy owner Eliza Chapman-Kete, who had seen business takings drop by about a third over the last year.
Apart from the odd logging truck and roading contractors on their way to and from the site, customers had been scarce, she said.
"We've had less business because there's been no through traffic. We have depended on our local community and whānau, they have been keeping us going."
