SH23 Whatawhata to Raglan slip repairs

2 June 2023

As good as new! The repaired highway has been sealed, with lane markings to soon be completed

Back on track to Raglan

The project to restore State Highway 23 between Whāingaroa/Raglan and Whatawhata, which was damaged by a serious underslip in February, is complete.

Waka Kotahi NZ Transport Agency and its contractors are over the next week (weather-permitting) finishing the final tasks, installing guardrail and lane markings, after which the temporary 30km/h speed restriction will be lifted.

The geosynthetic retaining wall which stablised the crumbling hillside was completed in early May, but paving and resealing the surface of the restored highway was tricky for our contractors to finish, due to the ongoing wet weather.

Traffic returned to the original highway in the middle of May, restricted at times to one lane under stop-go traffic management while the sealing work was done.

Meanwhile, the asphalt on the temporary diversion road, which was built on private property to skirt the underslip, was removed in preparation for it to be restored to the landowners. 

The project crew are now preparing to begin the remediation of the affected properties, including fencing, planting and landscaping.

The temporary diversion road opened on 4 March; this allowed geotechnical experts to thoroughly investigate the underslip, and for the best remedy to be decided.

Waka Kotahi is grateful for the generous co-operation of the landowners, which enabled work to begin on the temporary diversion road within days of the initial underslip.

The section of State Highway 23, known as the Raglan Deviation, began to crack in late January, when the ground was saturated following unprecedented rainfall. The cracks soon turned into an underslip, which significantly worsened after Cyclone Gabrielle, with a 30m long section of highway dropping around 2.5m.

The geosynthetic retaining wall has concrete piles drilled 12m deep into the hillside

Hon Nanaia Mahuta (second from right) attended the blessing with Ngaati Maahanga kaumātua, Waikato Regional Council chair Pamela Storey (third from right), and Waikato District Council Mayor Jacqui Church (fifth from right)

A blessing for the community

When the structural work on the project was complete, kaumātua from Ngaati Maahanga carried out a blessing on the work site. The event was attended by the Hon Nanaia Mahuta, Minister for Waikato Regional Cyclone Recovery Efforts, and local dignitaries including Waikato District Mayor Jacqui Church and Waikato Regional Council chair Pamela Storey.

Waka Kotahi Director Regional Relationships, David Speirs, praised the mahi of the many people whose efforts combined to achieve such a swift result for the community.

"We know how crucial the stretch of road between Hamilton and Raglan is, so sought a quick fix by building the temporary bypass on two neighbouring properties.

"We were very much in the hands of the landowners, and we are so grateful to them, as they’ve been hugely accommodating through this process, allowing us to create the diversion road at considerable disruption to themselves.

"The wider community owes them a huge debt of gratitude because their co-operation not only sped the process up, it made it a lot easier for us.

"It was the only reason we could reopen to the public so quickly."

You can see a short video about the blessing here

For more photographs, background and a full timeline, please visit the project website