Slip A1 and A2 permanent piling. Night works are underway to install the pile sleeves in preparation for the main piling rig

SH1 Mangamuka Gorge slip repairs - August update

Kia ora koutou,

It’s now been a year since the August 18 weather event that caused the slips resulting in the closure of SH1 through the Mangamuka Gorge. Despite the hard mahi from the crews on site, the ongoing wet weather over the last couple of months has been challenging.

The earlier weather events over the last couple of months have caused two additional large slips within the site area, and adding complications to existing slip sites, and subsequently creating delays to the programme. These new slips are proving challenging above and below the ground.

With most of the enabling works complete, we are seeing less ground movement. However, our crews still have measures in place to keep everyone safe and at times we’ve needed to stop work when conditions become unsafe, or the numerous sensors positioned through the gorge have indicated ground movement.

As a result, we have reassessed our programme and the previously communicated timeframe of re-opening the road in May 2024 has now become unrealistic.

While we are still working through what this means for the programme, we are now anticipating the road to re-open late 2024. We acknowledge that this news will be disappointing for residents of Te Tai Tokerau, who have been looking forward to this vital link being reinstated.

We appreciate your understanding, patience, and support as we work through this.

Slip A12/A13 permanent piles. The piling rig and crane are now in place and underway with the works.

Progress update

We have completed the enabling works at the northern and southern ends of the gorge and are making good progress further up the gorge to ensure the area is safe and stable before the heavy machinery arrives on site to undertake the permanent works.

Permanent works have begun at both ends of the gorge with the large piling rigs and cranes in place at both ends of the gorge. Eighty-three piles need to be drilled up to 27m deep into the ground in some places.

In addition, we have completed the installation of all permanent pile casings on slip A3 and the permanent spawl walls on slip A8.

This is a huge moment for the project and the teams on site, as both ends are now working on the permanent works on the mission towards the summit. Due to the amount of space required to safely operate these machines, part of this work is being undertaken at night to ensure that access can be maintained for the remaining sites during the day.

In addition to this major milestone, we are nearing the completion of the enabling works on 4 of the other critical slips (A3/A5/A8/A9). The teams have also been undertaking preventative work on 8 other sites in the form of rock spall walls.

Back in May we were excited to identify the presence of long-tailed bats (pekapeka-tou-roa) in the gorge following a survey that was undertaken in April. Automatic Bat Monitors were set up to measure their high frequency signals through special bat software. The colder months mean that there is less activity for the bats while they conserve energy, meaning that they are at a greater risk with any work around their habitats.

The confirmation of this ‘Threatened’ (Nationally Critical) and protected species, means that we are now able to identify potential areas for bat roosting and foraging, and prioritise these areas for safe management by avoiding them until they can be safely managed using appropriate vegetation removal protocols.

Long tailed bat / pekapeka-tou-roa (chalinolobus tuberculatus) Image: Sabine Bernert (Department of Conservation)

Check out the bottom of this newsletter to see more images of what our teams have been up to.

News and Media

Check out the links below to find out more from Radio NZ’s recent visit to the gorge to see the work going on and meet some of the team up there.

RNZ Morning Report - Rebuilding Mangamuka Gorge

RNZ - Northland's Mangamuka Gorge road repair a massive job amid more slips, heavy rain

Upcoming Events

A big thank you to everyone who came to see us last weekend at the Kaitaia Market.

Keep an eye out on out social media channels over the next couple of weeks for our upcoming engagement pop-up in Mangamuka and other planned events.

These pop-ups are an opportunity to meet a few of the team working up here in the gorge to find answers about what we are doing, from those who are on the ground doing it.

Waka Kotahi NZ Transport Agency – Northland Facebook page

Slip A1 and A2. Permanent piles casings installed.

Slip A3. Permanent pile casings have been installed.

Slip A5. The capping beam for the enabling works is now complete.

Slip A8. Eight other rock spall walls are being installed along the site.

Slip A9. Enabling works piling is nearing completion.

Slip A12 enabling works. Enabling works continue as the permanent works commence further down the hill.

Slip A12. Permanent piling is underway.

Slip A12 Piling. Some piles are up to 27m deep.

Slip A12 and A13. Piling rig and crane for the permanent piles are now underway.

Slip A12. Piling rig and crane for the permanent piles are underway.

More information

For more information on the SH1 Mangamuka Gorge slip repairs, contact us at northlandproject@nzta.govt.nz

Visit our website www.nzta.govt.nz/mangamuka