Slips A12 and A27 - these slips present unique challenges, as work on both needs to be undertaken at the same time

SH1 Mangamuka Gorge slip repairs – December update

Kia ora koutou,

With end of the year fast approaching we would like to send a massive thank you to everyone involved in the project for the huge amount of mahi over the year.

We would also like to thank the community for your continued understanding, patience, and support.

From the whole team up in the Mangamuka Gorge, we wish you all a happy and safe holiday season and a happy New Year.

Detour routes. SH10 is suitable for all vehicles including trucks. The Twin Coast Discovery Highway is open and provides a scenic alternative. This route is only suitable for light vehicles and campervans.

Detours Remain in Place

Recently we have seen an increase of visitors to our gates who have been following directions through their in-car GPS.

Services such as Google Maps and Apple Maps have been updated to reflect the road closure, however some in-built GPS services have not been updated.

If you have friends or whānau visiting, please remind them that the official detour route is via SH10 and may add up to 40 minutes to their journey. This route is safe for all vehicles, including heavy and freight vehicles.

The Twin Coast Discovery Highway route is also open and provides a scenic alternative. This route is only suitable for light vehicles and campervans.

Local hapū and iwi partners visiting the Mangamuka Gorge project site and sharing kai with the workers.

Hapū and Iwi Visit Mangamuka Gorge to View Progress

Recently we were privileged to show our hapū and iwi partners from both sides of the Maungataniwha ranges a first-hand look at the work being undertaken as part of the SH1 Mangamuka Gorge slip repairs project, and to share delicious kai with the team on site.

Hapū representatives are part of our project team, with important roles within the project as well as alongside Waka Kotahi on cultural design outcomes and providing guidance to resource the project with locals.

Our workers have been putting in some huge mahi, with over 630 individuals inducted onsite and close to 200,000 hours worked since works started in March. Close to 75% of these workers are locals.

The benefits and positive culture created by involving passionate locals aligns with our broader outcomes initiative which seeks to achieve wider social, economic, cultural and environmental benefits. By working together with our communities, we can achieve great outcomes, not just for our projects but by providing jobs, upskilling future generations, and minimising our environmental impact.

“It was a huge privilege to host and show the local hapū, as our project partners, what the project team has achieved on the project since the last hapū site visit back in early August.  I’m sure everyone can appreciate the amount of mahi that has gone in from everyone involved on the project, on and off site, to get to where we are currently.  The local involvement on the project has an enormous impact on the positive culture and progress on site” says Hendrik Postma, Senior Project Manager.

Mangamuka Gorge Slip Repairs Finalist for Site Safe Award

Last month we announced that the innovative stormwater controls for the project was recognised with a Highly Commended award at this year’s International Erosion Control Association (IECA) Australasian Environmental Excellence Awards.

This month, we are pleased to say that our TARP (Trigger Action Response Plan) Sensor system has been recognised as a finalist for the 2024 Site Safe Health, Safety, and Wellbeing Awards in the Safety Innovation Award (large organisations) category.

The TARP sensors protect the site teams from the risk of further slips by detecting ground movement and monitoring soil moisture and rainfall levels.

The nomination recognises the innovative thinking and technology that has been put into place, making sure that the teams up in the gorge stay safe.

As Waka Kotahi Senior Project Manager, Hendrik Postma explained; “The implementation of the TARP system on the Mangamuka Gorge slip repair project was a game changer. The system gives us the assurance that crews working on the project are working in safe conditions in a high-risk environment on a slip prone section of State Highway 1.”

The winner will be announced at a ceremony in March 2024.

For more information on the TARP sensors and what they do, check out our article in the September update here.

News and Media

Check out the links below to hear our Project Director Norman Collier provide a project update and read about the progress and recent visit with our hapū and iwi partners through Te Hiku media.

Listen: Te Hiku Media - Mangamuka Gorge Update

Read: Te Hiku Media - Mangamuka Gorge Remains Closed For Christmas

Need more information for your local community group?

Our latest flyer ensures you and your community are kept up to date.

If you would like some printed copies to hand out to your whānau or community group, send us an email at northlandproject@nzta.govt.nz with your name, mailing address and the number of copies you need. We’ll then pop them in the post directly to you.

To view the electronic version of the flyer, click here.

For more information on the project, please click here for the website.

Progress Update

We are now mobilised on 12 of the 15 critical slip sites at various stages, including drilling, piling, capping beams, and up-slope retaining walls.

Where logistically possible we are continuing to undertake night works to ensure that we maintain this progress.

The teams onsite are making the most of the drier weather and are at times drilling up to 4 piles a day which is quite an achievement.

To minimise disruption to the overall programme, work will be continuing onsite during the holiday period.

Slips A1 and A2

All enabling works and casings for the 1050mm diameter piles are complete.

The scheduling for the permanent piling operations at this slip prioritises them as the final tasks among all the critical slips.

Since we have positioned the large rigs further up the site, this will be the last step when moving north and exiting the site with the big rigs and cranes.

Slip A3 – reinforcement cages being installed prior to concrete being poured.

Slip A3

Despite challenging ground conditions, the team have successfully installed a total of 17 out of the 42 planned permanent piles.

The project is on track, with the efforts of both the day shift and night shift teams ensuring steady progress.

Slip A4 – enabling works are underway. Due to the access constraints, work on A4 will continue over the Christmas break.

Slip A4

Enabling works are underway, including clearing shrub and excavation.

Work platforms have been completed and all the pile locations have been completed by the surveyor.

Bund and hand railing have been installed.

Due the access restrictions caused by these repairs, work will be carried out over the holiday break to minimise disruption to the rest of the site.

Slip A5 – the final level of the capping beam is now being installed.

Slip A5

The steelwork is now finished, and a specialised capping beam team is on-site to install the shutters (the formwork which the concrete is poured into).

The final segment of the capping beam has been completed and is currently undergoing the curing process. Progress is steady with 80% overall completion at this site.

Slip A6 – enabling works capping beam is complete. Spall walls and drainage upgrades are underway.

Slip A6

Recent efforts over the past month have been centred on the reinstatement of the road. This involved removing the slot drain work platforms, and the installation of stormwater manholes and rock spall walls.

Excavation of works platforms marks the beginning on the next phase of permanent works.

Slips A7 and A8

The design has been finalised and the team is currently scheduling the construction works.

Slip A9 – permanent works are underway with piling, cages and concrete being poured.

Slip A9

The permanent works are continuing with casings being welded and secured.

A constant and consistent supply of concrete has meant that 16 of the scheduled 53 permanent piles have been completed.

Slip A26 – stormwater and drainage upgrades are complete with the permanent work platform installation beginning.

Slip A26

Enabling works have been successfully completed and the permanent works have begun with construction involving going straight into permanent piles.

This slip has a total of 74 scheduled piles with the team beginning coring activities over the last couple of weeks.

Slip A10

The project team are working with a contractor to undertake test anchors to finalise the design to be able to anchor back the existing gabion wall.

Slip A11 – while it may not look like much, A11 is a sizable slip area over several hundred metres and 21m deep.

Slip A11

The design team is working with contractors, hapū and DoC to finalise the design for the proposed retreat on this slip site.

Approximately 24,000m3 of material needs to be removed and current road needs to be realigned away from the slip prone site.

This is a complex slip site with considerable challenges and considerable environmental controls around wildlife and habitat management.

Slip A12 – capping beam on the upper section is being installed.

Slip A12

Piling has been completed with 39 permanent piles poured and the formwork for the upper section of the capping beam now being installed and poured.

Slip A13 – permanent piles are being installed. The enabling works can be seen behind the permenent piles. The enabling works will support the heavy machinery required for the permenant works.

Slip A13

The team has encountered several challenges around collapsing ground within the piles. This requires remediation involving backfilling the hole with flowable fill (a low strength concrete), and allowing time for it to set before re-drilling

The team is continuing to make progress with the installation of the 1050mm diameter permanent piles, with 14 piles out of a total of 41 piles now poured.

Slip A27 – platforms and Universal Column (UC) beam installation is ongoing. UC beams are H shaped columns that the precast concrete retaining panels slot into to form the wall. This design was successfully used during the 2020 repairs

Slip A27

Efforts have been focused on widening works platforms and addressing problematic soil conditions with 6 out of the scheduled 32 Universal Column (UC) piles now installed.

The design approach for A27 is similar to the works undertaken for the 2020 repairs with UC beams and panels being installed to stabilise this section.

Tackling this slip presents unique challenges as it is located above A12 and needs to be coordinated around access and ensuring underground works, such as the installation of the UC beams and ground anchors, do not clash.

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