SH23 Whatawhata to Raglan slip repairs

4 March 2023

An aerial view of the slip site and diversion road works taken on 28 February.

Road to Raglan now open

The main route to Raglan is back open to traffic.

Waka Kotahi NZ Transport Agency today opened a two-lane temporary diversion road skirting the serious under-slip that closed State Highway 23 on February 1.

“We are delighted to have restored road access for all traffic on this crucial link between Raglan and Hamilton, as we know how important it is to people in this community,” says Cara Lauder, Waka Kotahi System Manager for Waikato.

“It could not have been done without the generous co-operation of the landowners, nor without the herculean efforts of the work team, who put in many long hours to make this solution a reality.

“Within days of the initial slip, we were able to begin tree felling and the earthworks needed to construct the temporary diversion road.”

While SH23 was closed, Waka Kotahi contractors Fulton Hogan took the opportunity to bring forward some planned resurfacing work to a steep section of the highway further west. This was completed in time for the opening of the diversion road today, preventing further disruptions on the route.

The new temporary road is raised to protect fibre optic cable running under the site.

The diversion has a speed restriction of 60km/h but will add minimal extra time to the journey between Raglan and Whatawhata, compared to the lengthy detour needed via Ngāruawāhia while the road was closed.

Ms Lauder says the under-slip is still active. “It continues to move, and geotechnical testing, including drilling and core penetration, is ongoing.

“We have not yet got the full picture of how Cyclone Gabrielle has impacted the site, and the ground was already saturated due to the unprecedented rainfall over January.’’

The under-slip significantly worsened after Cyclone Gabrielle; a section of the highway nearly 30m long dropped around 2.5m, and the slip crossed over the centreline.

"The temporary diversion road allows us the time we need to thoroughly investigate and plan the long-term restoration of SH23,” Ms Lauder says.

For more details, background and photos go the project website