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SH4 Update

20 July 2020

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Good headway made on Te Oreore dewatering

Waka Kotahi NZ Transport Agency is making good headway on stabilising the Te Oreore slip area on State Highway 4, where the temporary road replaces the section of highway damaged in the October 2019 slip.

Regional Transport Systems Manager Ross I’Anson says deep groundwater extraction wells and pumps are now set to remove groundwater from the slip area into the newly upgraded drains, to take water away from the site.

“This followed preparatory work which included creating access tracks, upgrading the drainage, drilling bore holes, taking samples deep below the road and putting in monitoring equipment. We are monitoring any land movement to check the impact of changes in groundwater levels or earthquakes.

“The measures are necessary to lower the groundwater levels. The steep hill slopes and weak underlying rocks in the region means it is more susceptible to landslips from earthquakes and prolonged periods of rain,” he says.

Last year’s slip was caused by water gradually building up in the soil and rock from groundwater seepage. This increased the water pressure at the base of the landslip, reducing the soil’s ability to resist the landslip movement to a point that the landslip was initiated.

“We would like to thank Ātihau-Whanganui and mana whenua Ngāti Rangi for their generosity and support throughout the process of building the temporary road and looking at options for the permanent route.

The work supports reconstructing the permanent road, planned to get underway in summer 2021.

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Damage to Otoko Pā embankments

You may have noticed there is damage to the Otoko Pā site, with a slip on the face of newly hydro-seeded embankments. This followed a period of heavy rain in the region. The movement on this site is minor but we’ll continue to monitor the situation to ensure the resilience of the corridor. We’re working on a plan to repair and mitigate any further damage.

The ongoing resilience of SH4 is very important to us, as it is for residents and travellers to the region. Late last year we developed a business case for a multi-million dollar, long-term resilience package for SH4 to give certainty about the resilience plan for the highway.  We hope to have an update for you toward the end of 2020.

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SH4 Site Update

1. Te Oreore Underslip

This section continues to operate with a 30km/h speed limit. Instrument monitoring and reporting for the site has continued.

Construction of dewatering wells is almost complete. See top story for more information on this.

2. Raukawa

Currently awaiting consent confirmation.

3. Whiskey’s Corner

The main physical work on this site has been completed.

We'll finish sealing the road in spring to avoid ‘pavement failures’, which means cracking, or potholes. This would be more likely if we did this work in winter.

4. South Raupiu Retreat

Most of the remaining work on this site is likely to be completed by August. Work on the surfacing will be completed in spring which is a much better time of year to do this than mid-winter.

5. Otoko Pā Overslip

All work on this site has been completed. See above story for more on recent damage.

6. Hapokopoko Curve Rock

Physical work has started on this site. Please anticipate delays on this site.

7. Kukuta Underslip

The site remains under one-way traffic lights.

The project’s design work has nearly been completed and consent is in place.

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Temporary traffic light safety

With repair work happening on State Highway 4, you’ll continue to see work crews across the various sites.

Many of these have been reduced to a single lane, with temporary traffic lights controlling the flow of traffic. Roads are reduced to a single lane to help work crews perform repairs  in a safe environment. 

Please continue to stop for red lights at temporary traffic lights for your own safety, as well as that of other road users, and our work crews.

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More information

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For more information on the State Highway 4 slip repairs project, visit our website 

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