Brynderwyn Hills recovery and enabling works

18 March 2024

A rapid transformation on the bottom of Brynderwyn Hills, just north of Atlas Quarries. The dark section at the top of the hill shows where hydroseeding has started.

What's been happening this week

As you can see in this week’s newsletter, the earthworks and excavations are really starting to shape and contour the hillside in order to strengthen the banks and create space to address future weather events. 

In the image above, excavation is nearly at road level and we have started hydroseeding the slope. This is where grass seed is mixed with mulch and water and sprayed onto the bare earth to help with erosion control. We will provide progress pictures as the seed starts to germinate in the next month or so.

Update photos

You can see in this image the amount of excavated dirt covering where traffic would normally be, right up to the edge of the road. This shows why a full closure is necessary to do this vital work.

This second image show a different angle and gives you an idea of the terrain and the amount of dirt that will need to be removed to expose the road underneath.

Follow the NZTA Northland Facebook page to stay up to date with weekly progress photos and footage.

Piling and retaining walls

As part of our work to reinforce the road and help prevent large slips, we are installing multiple retaining walls. Within the closure there are two critical 25 metre long retaining walls, which will help stabilitse the road. Several additional retaining walls will be constructed after the closure of SH1. The retaining walls are strategically located in high-risk areas, with the majority on the downhill side of the road (to prevent the road eroding or slipping away) and a handful on the uphill side.

At this stage, 12 x 700mm holes at a depth of 10-15 metres and spaced one metre apart have been drilled and concreted.  

The piles are commonly described as H Beams, or steel universal columns, which weigh 2-3 tonne each and range from 10-18m long. They are encased in concrete and have lengths of timber installed between them to form the retaining wall, before being backfilled.

The piles are transported on heavy haulage trucks to site, before being placed into the drilled holes using an excavator. Due to the slope stability and pile locations, the downhill holes for the piles are created with the help of a piece of equipment called a pendulum auger. This is attached to an excavator, which works from the closed road.

Copper skink and velvet worms (peripatus) found in the Brynderwyn Hills

Ecology on the hill

Project ecologists have been busy scouring the hills for various native species, with a variety of creatures located and safely rehomed away from construction.

So far, no kiwi have been found but checks continue. The ecology team use a thermoscope to pick up heat signatures in the bush and the specially trained kiwi dog, Pearl, on the ground.

One native copper skink has been found in the southern section of the hills and relocated. Native skinks are identified by their colour and the scale pattern on their head. The skink is brown or grey-brown with a dark brown stripe down each side, and an iridescent rainbow or metallic sheen when seen in bright light. Plague skinks have one large scale on the top of their head, whereas New Zealand native skinks have two smaller scales. Any native skinks found must be relocated 100 metres away from construction in a similar habitat to where they were found. 

Four rhytid (native) snails have been salvaged and relocated. Rhytid are one of several species of carnivorous snails in New Zealand, they eat other invertebrates and worms. 

Some velvet worms have also been found in rotten logs and safely moved away. They are essentially a worm with legs, similar to a centipede. Part of the invertebrate family, they are a historic New Zealand species, with ancient lineage.

A new path created for heavy machinery to access Atlas Quarries

Making a path for the Moxy trucks

On this project we use Moxy trucks, a type of articulated dump truck, for transporting heavy loads. Filled with earth, the total weight of a Moxy can be up to 50 tonnes. To accommodate the frequent movements of these trucks and their heavy loads, a path has been constructed to avoid the bridge near the entrance to Atlas Quarries, as it is not designed to accomodate this amount of weight.

Meet the team- Cindy Hempsall

Our partnership with iwi is an essential element of our recovery works on the Brynderwyns Hills. Through this partnership we work together to ensure our works respect the ecological and cultural significance of this area. Cindy from Te Uri o Hau provides the team with guidance and direction.  

What is your role? My role is to represent hapu on behalf of Te Uri o Hau settlement trust and environs. We’re there to help ensure minimal impact to fauna, flora and biodiversity. People don’t often realise how earthworks will impact ecological habits. We also want to bring an understanding of how whakapapa (genealogy) connects us to the whenua (land) and make sure we aren’t disturbing any wāhi tapu (burial grounds) or other areas of significance.  

What is your connection to the area? I’m born and bred here and grew up at Otamatea marae, but I’m connected to all marae in the rohe (area).  I know this place like the back of my hand, I know the impacts change has had on the land over the years. Not just physical impacts on the whenua (land) but also to our waters. The Kaipara Harbour has whakapapa (genealogy) into all 14 marae under Te Uri o Hau.  

What will this project enable? The Brynderwyns have always played an important role connecting us to the Far North. It’s not just a scenic experience, there are rare flora and fauna in the area too so it’s important from an ecological aspect. Maintaining this connection to people, places and the whenua (land) will outlast all of us, so it is deeply spiritual. The Brynderwyns are a taonga (treasure). 

What is your favourite place in Northland? I can’t pick one, they are all my favourite. All ngahere (forest) and beaches I love!

Tell us something about yourself Most people don’t know how passionate I am about the whenua (land) and wai (water). It’s as important to me as a family member. We are blessed to be its kaitiaki and benefit from the kai (food) and rongoā (medicine) it provides. Because everything is connected and living, its succession is so important for the good health of current and future generations.

Key information at a glance

SH 1 Brynderwyn Hills closure status

Closed: 26 February (12:01 am) - 27 March (11:59pm)

Open: 28 March (12:01 am) - 2 April (11:59 am)

Closed: 3 April (12:01 am) - 12 May (11:59 pm)

Three scenic detour routes

Cove Road route: Turn off at Kaiwaka, use Kaiwaka Mangawhai Road, Garbolino Road, Tara Road, Cove Road, Nova Scotia Drive and connect back to State Highway 1. (Restrictions are in place for trucks with trailers on Cove Road between Mangawhai Heads Road and McLean Road).

Paparoa Oakleigh Road route:Trucks and trucks with trailers up to 50 tonnes can use this route.

SH12/SH14 route: HPMV (high productivity motor vehicles) must use this route.

Local routes contact: 

Whangarei District Council 0800 932 463

Kaipara District Council 0800 727 059

State Highway route contact:

NZTA 0800 444 449

More information

For more information on the SH1 Brynderwyn Hills project, contact us at northlandproject@nzta.govt.nz

Visit the project website www.nzta.govt.nz/brynderwyn-hills