Coromandel state highway continues to slip as Cyclone Gabrielle approaches

Friday, 10 February 2023

The slip on SH25A has increased to 110 metres and remains unstable on Friday.

The slip which has closed one of the main thoroughfares to the Coromandel has moved to more than 100 metres wide and could face further subsidence with Cyclone Gabrielle approaching.

Waka Kotahi will closely monitor the slip site on State Highway 25A between Kōpū and Hikuai for further damage with bad weather forecast to hit the region once again next week.

The slip began with cracks in the road after Cyclone Hale last month and then worsened with the storm that hit Auckland, Coromandel and Bay of Plenty.

Associate Transport Minister Kiri Allan visited the Coromandel and SH25A on Friday to better understand the size of the job ahead.

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Associate Transport Minister Kiri Allan receives an update from Waka Kotahi.

Waka Kotahi said the slip now measures around 110 metres across and is highly unstable, and the coming weather event will potentially bring new challenges.

A full geotechnical assessment cannot be done until the site has dried out. However, with the use of drones, early investigations are underway.

It could be a long time before State Highway 25A over the Coromandel range reopens after the slip worsened.

Regional Manager of Infrastructure Delivery, Jo Wilton said they’ve begun to get the full picture of the damage, but a solution cannot be established until preliminary work is completed.

“The geotechnical investigations will help inform the best option to reinstate the highway. We are exploring a range of options for this site – but we won’t know more until the experts can share their findings.”

Allan said she was aware that it’s a critical thoroughfare for residents and visitors and any fix will be complex and take considerable time.

“It’s imperative it’s restored in a way that ensures resilience and long-term confidence for the peninsula,”

Waka Kotahi continues to monitor the site on a daily basis to look for further movement and any changes in geotechnical conditions.

Geotech work still to be done includes drilling boreholes and excavating test pits to assess the stability of the underlying foundation at the site and surrounding area. This needs to be done from the bottom of the slip, and the road agency was exploring remote options for our worker safety.

The transport agency is also working through the impact the closure of the road has on the rest of the Coromandel state highway network. From assessing how traffic and truck volumes are changing around the peninsula to clearing drains and culverts in readiness for the next weather event.

Waka Kotahi expects to be able to share more information about potential solutions with the public and stakeholders in the next fortnight.