Crews installing temporary piles at slip 13 on the southern end of the gorge. They have installed 10 piles at this site in the past week.

SH1 Mangamuka Gorge slip repair work in full swing

Kia ora koutou,

Slip repair work is in full swing in the Mangamuka Gorge with crews working across multiple work sites along the length of the gorge.

The team are working in a very constrained environment, within an already tight road corridor which is made even tighter with the slips impacting the road, large machinery and multiple work sites with crew members buzzing around. This means the movement of equipment and materials onto and around site can be slow and needs to be carefully planned to ensure the safety of our people and to maintain the integrity of the road.

Drainage work being carried out in a constrained environment at slip 12 on the southern end of the gorge.

What we’ve been up to

Over the past few weeks, we’ve started work on strengthening eight of the 13 different slip sites to prepare them for the large machinery which will be required for seven of the critical slip repairs. This has included:

• Installing temporary piles at one of the slips to strengthen the road and create a sturdy base for the heavy drill rigs, excavation equipment and our crews to work on. This is a big piece of work with approximately 700 piles to be installed across all 13 slip sites.
• It’s important we look after the environment while we undertake this work so we’ve been implementing environmental and sediment controls on site. This includes silt fencing, rainwater capture drains and sediment tanks to ensure any stormwater runoff is correctly collected, diverted and treated.

We’ll also be making the ground less susceptible to slips by improving the drainage through the gorge so it’s more suitably equipped to handle the increase in severity and frequency of weather events. . Drainage and stormwater management are critical parts of this project and will play a major role in improving the resilience of the road.

Successful relocation of Kauri Snails and Land Snails

Protecting and enhancing the environment we’re working in is critical to us and our partners. This is especially important in the Mangamuka Gorge as the surrounding Maungataniwha Ranges are home to a diverse range of native and endangered flora and fauna. Over the past few weeks, we’ve been working closely with New Zealand Environmental Management and hapū to locate these species and safely relocate them away from our construction sites so they are out of harm’s way.

The team have found several pupurangi (Kauri Snails) and Amborhytida dunniae (Land Snails) and have relocated them deeper into the forest. We’ll continue to carry out regular biodiversity walkovers to ensure we identify and relocate any other species that appear.

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