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TREC Tairāwhiti recovery update

Issue 16

7 March 2025

Tēnā koe

In this edition we share updates about work getting back underway at Rotokautuku (Waiapu) Bridge in Ruatoria and progress at Kopuaroa and Otoko Hill.

We’re also back on the coast as part of Gisborne District Council’s (GDC) Rural Roadshow next Tuesday 11 March, if you’d like a face-to-face chat about the work we’re doing.

27 Pakiakanui Road, Te Araroa from 10am to 12pm
Hekiera Road, Ruatorea (Heartlands Centre) from 1pm to 3pm

Thanks again for your ongoing patience as we carry out this important mahi.


	Strengthening Rotokautuku (Waiapu) Bridge The next stage of work will start soon at the Rotokautuku (Waiapu) Bridge. This involves strengthening the bridge bearings (supports) damaged during Cyclone Gabrielle. While most of this will happen out of sight under the bridge, there will be temporary speed restrictions on the bridge to keep crew and road users safe while work is being done. So please drive with care. Rock revetment work down at the base of the bridge to protect it from scouring (erosion) is also being planned. We’ll keep you up to date as details are confirmed. The team undertaking assessments of the early strengthening work.


	Final Hikuwai investigations underway an important step forward We mentioned in our last update the team has hit 50% design for a single, two-laned bridge to replace the original washed away in Cyclone Gabrielle. To help with the next stage of design, the construction team is doing more checks under the ground to: Confirm the exact size and location of the old bridge piles to minimise potential issues during construction Confirm the ground conditions at the location of each of the new piles that will support the new bridge. Once enabling (early) works get underway they will include three stages: Site set-up Construction of a 250m long temporary road parallel to SH35 that will connect to the existing Bailey bridge to provide a safer working space for the team and to reduce impact on road users Demolition of the remaining parts of the old bridge Procurement for the three stages of the enabling works has been underway for a few months and is nearing completion. Further details of the project start date will be shared here and on our project web page. Ground investigations underway at Hikuwai Bridge.


	Out of sight on Otoko Hill This image shows progress at Allen’s Existing Wall (named after a local farmer in the area) on Otoko Hill. This is one of two active sites in the area. Most of the work here is happening below the road and out of sight of motorists. Repairs include new drainage, installing soil anchors (long metal rods) under the road and then adding shotcrete (sprayed on flowable concrete) to the retaining wall. These images show the shotcreting in progress, and then the finished result. Work is expected to be finished here in April. Thank you for your support while we’ve made great progress repairing the extensive cyclone damage in the Otoko Hill area. Of the nine sites, six are complete, two are underway and the final one is due to start next week. Recovery work at Rakauroa and Matawai Road, both sites are further along from Otoko Hill will be underway soon. 'During' and 'after' shotcreting progress to help stabilise the retaining wall.


	Sites humming at Kopuaroa Kopuaroa Stream Bridge 2: Heavy rain set our scour protection work back here. However the team has returned and re-installed our environmental protection measures so work can restart. This included the environmental team ‘de-fishing’ the area last week to safely relocate fish (which included six eels) away from the work to another part of the stream. Work is back underway at Kopuaroa Stream Bridge 2.


	Kopuaroa Slip 1: The team is making good progress here. Soil nails (long metal rods) are now being inserted into the slip face under the road to help with stability. Contractors have two crews onsite helping to complete the work faster. This site is expected to finish by mid-2025. This drone footage of work underway at Kopuaroa Slip 1 shows the scale of the slip the team is repairing.


	Kopuaroa Slip 2: The slipface has been ‘undercut’ and geo-textile (shown in the image below) is currently being placed over it to help stabilise it. A buttress (supporting wall) will then be built up to road level. This work is expected to finish by mid-2025. One of the three sites underway at Kopuaroa in a 5km radius.


	Drainage work complete at Morere TREC has finished putting in extensive new drainage at Morere, south of Gisborne, six weeks ahead of schedule. This work will help move water away, which will reduce water pressure building up in the hills. This will also help reduce movement in the road. 'During' and 'after' photo of drainage work at Morere.


	Tairāwhiti Rivers Recovery field trip TREC helped host council staff from around New Zealand at a Gisborne District Council event last week that explored the impact of Cyclone Gabrielle and the approaches being taken for future resilience. TREC’s Project Manager, Richard Bayley, and hydrology lead, Mark Groves, shared insights into the severe damage caused to Gisborne’s rivers and waterways and the impact on state highway infrastructure, particularly on the SH35 Hikuwai Bridge No.1 and through the Mangahauini Gorge. The event included a site visit to Mangahauini Gorge to see progress and discuss potential future solutions. Work stopped for a short period during the planned visit so attendees could safely view the project with help from the TREC team.

State highway snapshot

Below is a snapshot of construction works either underway or coming soon. You can also view sites on our interactive map.

Here are some of the construction terms we use below:

Buttress – supporting structure
Counterfort drain – drain that improves slope stability by controlling groundwater
Dolosse – interlocking concrete blocks
Gabion wall – baskets filled with rocks
MSE - (Mechanically Stabilized Earth) – a retaining wall construction technique used to stabilise slopes
Rip rap – large rocks
Rock revetment – protection
Scour – erosion
Shotcrete – sprayed liquid concrete

SH2 underway

Otoko Hill Slip #2 (site G) - Hill stabilisation using soil anchors, shotcrete, and rip rap
Allen’s Existing Wall (site J) – Reinstate underslip under existing wall using soil anchors and shotcrete
Morere – Counterfort drain installation

SH2 coming soon

Rakauroa – Reinstate underslip using soil anchors and shotcrete
Otoko Hill – Tree removal and major drainage to stabilise slopes
Matawai Road – Willow wall to stabilise slip

SH35 underway

Makatote dropout #2 – Buttress support and rip rap to prevent future river erosion
Makatote dropout #3 – Reinstating state highway to two lanes, buttress support and rip rap to prevent future river erosion
Kopuaroa Stream Bridge – Scour protection beneath bridge using soil nails and shotcrete
Mangahauini Gorge early investigations - Drilling for soil samples to help with the design of this major project
Mangahauini Gorge early works - River training and sheet pile wall strengthening
Awatere Gully – Buttress wall with gabion baskets to repair the underslip
Mangahauini Gabion Wall – Stage 2 – Soil nails, buttress and rip rap at the bottom of the existing gabion wall
Kopuaroa Slip 1 – Reinstate SH35 to two lanes by installing a soil anchor and shotcrete wall
Kopuaroa Slip 2 – Build a 250m long buttress to support SH35 and provide additional drainage
Opape underslip – Buttress with gabion wall
Hikuwai Bridge – ground investigations

SH35 coming soon

Kemps Hill Subsidence – Buttress repair using a willow wall. Three faults to be repaired to reinstate state highway to two lanes
D9 Gully Site – Buttress wall with MSE. Two faults to be repaired to reinstate highway to two lanes
Waiapu revetment – Repair the scour at the south end of the bridge and construct a major revetment with dolosse for futureproofing
Hikuwai Bridge No.1 Replacement – Enabling works
Rotokautuku (Waiapu) Bridge repairs – Strengthening works