Permanent fix of of underslip on SH31 - Kawhia about to begin


Work to fix an underslip on SH31-Kawhia Road will begin from Tuesday April 11 and require lengthy day-time closures.

11 April 2023

REMINDER: Work to fix the under-slip on SH31 – Kawhia Road is underway and involves lengthy day-time closures for five weeks.

Note SH31 will not be closed on Anzac Day or on weekends. One lane will be open under one lane open stop/go traffic management on these days.

Closure hours in media release below.

29 March 2023

Waka Kotahi NZ Transport Agency and contractors have been working on a solution since the slip reduced the only sealed road to Kawhia to a single lane in mid-February.\

 An engineering technique called soil nailing will strengthen the site but because it is very narrow, with a steep drop-off, the road will need to be closed to traffic while work is happening.

“The plan is to close the road each week-day at 8am, we will work until 12.30pm then open it for one hour, closing it again from 1.30pm to 5.30pm,” says Waka Kotahi System Manager for Waikato, Cara Lauder.

“There will be no weekend work,  with the road remaining open at single lane, but these day-time works and closures will be needed for about five weeks.”

In an emergency situation the site can be cleared to allow emergency vehicles through.

Access in and out of Kawhia during the closure periods will be via SH39 to Ngutunui Rd, Pekanui Road, Okupata Road and Oparau Road back on to SH31. This is a collection of local roads with some unsealed stretches and takes about 10 minutes longer than SH31.

“I hope most people can get through our worksite while it is open but for those who can’t this alternative route is available for light vehicles and we advise drivers to take care,” Ms Lauder says.

The underslip is about 20km west of the corner of SH31 and SH39 at Tihiroa, and west of the Kawhia lookout.

Since the underslip developed there has been extensive geotechnical work to understand the cause of the problem and design a solution.

“The slip site is between two retaining walls and the piling under those walls we found was in good condition and provides stability for the work ahead,” Ms Lauder says.

Soil nailing strengthens weak and unstable ground. At the underslip site, a number of 12 metre-long steel bars will be driven in to strengthen and stabilise the ground.

The site has been operating at one lane with traffic lights and a speed restriction in place since cracking developed in mid-February.

“With reasonable weather in the past month and some initial work the slip has stabilised and we have been able to keep the road open,” Ms Lauder says.

“That has been a good result as this is a vital route for the Kawhia community, farms and other businesses.”

About 800 vehicles a day use Kawhia Road and around 13 per cent are trucks.