SH1 Mangamuka Gorge slip repairs

Project Update

28 May 2024

Slip A4 – Pile casings being spliced and screwed in place.

SH1 Mangamuka Gorge Slip Repairs – May 2024 update

Kia ora koutou,

As the dry autumn rolls into winter, we are making the most of it by running 3 shifts day and night.

While all of the work across the gorge is continuing at pace, a large part of the focus this month has been around the realignment of State Highway 1 (SH1) at slip A11.

With 3 critical slip repairs now complete, we are working at pace to repair the remaining 12 critical sites. In addition, throughout the gorge we’re upgrading the damaged or existing drainage, so it’s better equipped to handle future weather events.

Mangamuka Gorge project wins at the Āpōpō Asset Management Excellence Awards

The project has been recognised in the sustainability category at the Āpōpō – Infrastructure Asset Management Professionals Incorporated Awards.

The awards recognise the work the project has undertaken around sustainability, for both the environment and communities we are working in.

Community engagement is crucial, ensuring alignment with local needs and concerns through updates, meetings, and transparent communication.

Environmental preservation is key, given the area’s biodiversity and it being classified as an area of outstanding natural landscapes. Beyond construction, the project aims to leave a lasting positive impact on the community and environment.

It was a night of recognition for Te Tai Tokerau with the SH10 Kāeo Bridge upgrade project also recognised in the community category.

Congratulations to both teams and everyone involved with the projects.

Part of the project team with the sustainability award at the Āpōpō awards ceremony last week. From the left: Jeremy McIntyre, Mandeep Ghadiya, Tina Mackay, Kullum McIntyre, Kylie Harris, Paul Nicoll, Kent Thompson.

Slip A11 Excavation Underway

These works are progressing at pace. Material is being transferred between the southern access gate of the gorge to a local fill site.

If you are in the Mangamuka area, you will have seen an increase in truck movements while we undertake these works, which are expected to be completed in mid-June.

These truck movements cover a 7km section of SH1 from the southern gate to the fill site access. There is a traffic management plan in place to minimise disruption.

Progress with the clearing of vegetation and beginning of excavations on A11 (left photo taken 30 April 2024, right photo taken 14 May 2024). All land and vegetation is carefully checked and wildlife relocated prior to any vegetation being removed.

Progress Update

Slips A1 and A2

All enabling works and permanent casings for the 1050mm diameter piles are complete. Now the piling on A6 is finished, the piling crews will move down to start work on this slip. These are the last slip repairs that require the installation of the larger piles.

Slip A3

Rehabilitation works – complete!

Anchors installed waiting for testing. This will be fully complete at the end of the month.

Slip A4

Rehabilitation works – 6/36 permanent piles complete.

The piling team is maintaining an impressive pace on permanent piling - drilling a pile to the required depth one day, and then installing reinforcing cages and concrete the following.

By coordinating activity like drilling, installing reinforcing cages and concrete deliveries, we are able to meet the demands of the entire site, ensuring there are no interruptions. 

With a similar approach to slip A9, bentonite (a special type of clay mix) has been introduced to help stabilise the piles to prevent them from collapsing until the reinforcing cage and concrete has been poured.

As mentioned in a previous newsletter, bentonite works by suspending the particles being drilled to strengthen and stabilise them. It helps stop water getting into a drilled pile by forming a filter on the side of the hole. The product is reusable so once it's been used, it can be taken out, treated and reused.

Pile cages being installed.

Slip A5

Complete!

Slip A6

Rehabilitation works – 50/54 permanent piles complete.

We are continuing to run night and day shifts on A6.

Once the final 4 piles are installed, the crew will mobilise all their machinery, tools, and equipment to slips A1 and A2.

Pile cages being installed.

Slip A7 and Slip A8

Site preparation has been completed on slip A7 with the main works programmed once piling on slip A26 is complete at the end of the month.

Vegetation clearance and site preparation started on 20 May. This included cutting an access track down-slope for the drill to access under the road on slip A8.

Slip A9

Rehabilitation works – 53/53 permanent piles complete.

The steelfixers and capping beam team are at the halfway mark. The capping beam is expected to be complete in mid-June.

First half of the capping beam has been completed. The second stage cages with the anchor portals can be seen at the top of the photo, ready to be poured.

Slip A26

Rehabilitation works – 52/72 permanent piles complete.

Progress is going well as the crew has moved to the northern (lower) end of the site, where they are in the process of installing the final 20 beams. Following this, the reinforced concrete panels will be installed and secured for the wall to be completed.

UC piling is continuing.

Slip A10

Test anchors have been installed and tested. Site mobilisation is underway with physical work scheduled to start in early June.

Slip A11

Despite the challenging ground conditions, the team has moved over 12,500 cubic metres of material to date.

With several minor weather events over the last month, sediment and erosion controls have been highly effective at both A11 and at the fill site, to prevent any sediment and material from entering waterways.

Despite hold ups from the wet weather, progress remains on programme.

Excavation is well underway.

Slip A12

Enabling works – complete.

Rehabilitation works – 38/38 permanent piles complete.

The anchor drilling team is progressing with their work with 2 drill rigs onsite for the anchors to be installed on this slip.

Anchors being installed.

Slip A13

Rehabilitation works – 43/43 permanent piles complete.

Piling is complete. The capping beam is currently being installed with the first of 3 sections being completed.

Once the capping beam is installed, the anchor team will continue from A12 onto A13 to complete all the works in this immediate area.

Completed capping beam at the bottom, installed cage in the middle and the final stage to be completed at the top of the picture.

Slip A27

Complete!

Worker of the Month

We are thrilled to announce Mike Fox as our Worker of the Month!

Mike is a dedicated Civil Engineer who brings over 30 years of industry experience to our project. A local of Ōkaihau, he has been a valuable addition to the project, contributing his expertise across the wide range of tasks WSP carry out.

Mike is responsible for inspecting reinforcement cages, overseeing concrete testing, and the development and design of our upgraded drainage assets. His attention to detail and commitment to quality ensure that each project meets the highest standards.

Outside of his professional life, Mike spends much of his free time driving his sons to their football practices and games, actively supporting their sporting endeavours. Additionally, Mike is an enthusiastic member of a home brewing group. Together with his friends, he delves into the science and art of crafting unique beers, finding joy in both the process and the camaraderie it fosters.

Mike's dedication, expertise, and enthusiasm make him an indispensable member of the team. Congratulations, Mike!

A controlled spread test is being inspected by Mike to check the concrete for the permanent works. This involves pouring a sample of concrete (for piles) and watching how it spreads out to make sure it is strong enough and won't get stuck in the tremie pipe.

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.

Electronic version of the May 2024 flyer

For more information about the project, visit the website:
SH1 Mangamuka Gorge slip repairs

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