Major piling finished on massive SH1/Mangamuka repair job in Far North

Piling work has finished on all 15 major slips on SH1 over the Mangamukas, with the road still on track to fully reopen before Christmas this year.

The last of the piling work on 15 major slips on State Highway 1 over the Mangamukas has finished, with the massive $160 million repair job still on track to be finished before Christmas.

Last week, the project reached another big milestone on the slip repairs on SH1 through Mangamuka Gorge with workers finishing the piling for all the 15 original critical slips.

NZ Transport Agency/Waka Kotahi (NZTA) said it’s a massive accomplishment as the team puts in the hard yards to get the road open before Christmas.

The work involves complex engineering solutions and large machinery working in narrow spaces to stabilise the road, with the goal to ensure safe travel by enhancing the road with advanced drainage systems and specific construction techniques, all while navigating the challenging landscape.

SH1 over the Mangamuka Gorge in the Far North has been closed twice in recent years. The 13km stretch of highway was wiped out by a series of 15 slips in a major storm in August 2022, a year after the highway reopened after a 12-month closure.

Repair work had been under way for less than six months when a storm in April 2023 resulted in another 20 slips - some massive - that covered 1.3km and required repairs.

Then heavy rain on June 19 and 20 that triggered a massive slip down the hill threatened to further delay the opening.

The two-year job to fully fix SH1 over the gorge has been so extensive and complex that an extra $60 million to finish it was allocated in May’s Budget, taking the total cost to $160m.

In total, 559 permanent piles have been installed. The only piling left to complete is on the slip from the bad weather in June, which is on track to be finished by mid-October.

’’We’re on schedule to reopen SH1 by Christmas this year. Keep up to date with our work on SH1 through Mangamuka Gorge by signing up to our email newsletter. Visit our website to sign up, and to find out more about the project: https://www.nzta.govt.nz/sh1-mangamuka-gorge-slip-repairs/.’’

Protecting the environment while repairs are carried out is important to NZTA and its partners, and this is especially crucial as the Maungataniwha Range is home to a diverse range of native and endangered species.

Some of the special creatures found as work progresses include the pupurangi (kauri snails), copper skinks and the frequently seen tusked weta. All native species found are moved deeper into the forest where they will continue to thrive.