Cyclone Gabrielle: Transport Agency closely monitoring Coromandel roads including unstable State Highway 25a slip

Cyclone Gabrielle is expected to further damage SH25A. Photo / Philip Hart

Due to Tropical Cyclone Gabrielle, Waka Kotahi NZ Transport Agency will closely monitor the Coromandel Peninsula, including the slip site on State Highway 25A (SH25A).

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

With 400mm of rain within a 24-hour period in the Coromandel region, contractors are bracing themselves for the impact on the roading network.

Crews have spent the past week clearing drainage lines, moving material out of stockpiles and organising resources for next week. This work all helps mitigate the impact of the weather and ensures a quick response to any issues on the network.

NZTA asks that during weather events members of the public only travel when it is essential to do so. If you are heading out, check the Journey Planner on the Waka Kotahi website for the latest information on the state highway network.

Work continues on finding the best option to reinstate the highway on SH25A, with the use of technology such as drones carrying out early investigations.

A full geotechnical assessment is still required but cannot be undertaken until the site has dried out. This work will involve 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 NZTA says it is exploring remote options for its workers’ safety.

The findings from this will help to inform how the agency moves forward, it said.

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

The agency says it appreciates SH25a is a critical thoroughfare for Coromandel residents and visitors, and it is conscious that any fix will be complex and take considerable time. It says it is committed to restoring the road in a way that ensures resilience and long-term confidence for the peninsula.

Waka Kotahi said the community can be assured it is readying the right expertise, from specialist roading and geotechnical engineers to its local maintenance crew who will establish safe access to allow contractors and machinery in.

Waka Kotahi is also working to mitigate the impact the closure of SH25A has on the rest of the Coromandel state highway network. This ranges 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 says it expects to be able to share more information about potential solutions with the public and stakeholders in the next fortnight.