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TREC Tairāwhiti recovery update

Issue 26

25 July 2025

Tēnā koe

In this edition we provide a closer look at planning for Mangahauini Gorge, share more about the final phase of recovery on State Highway 2 (SH2) Otoko Hill and work getting underway at Hakanui Straight as well as taking a trip up State Highway 35 (SH35) to Mata School and one of our Makarika recovery sites. There’s also a reminder about our crews working at Rotokautuku (Waiapu) Bridge.

Thanks for your patience as we continue our recovery mahi.


	SH35: Mangahauini Gorge – river management Imagine a world where engineering is like building with Lego blocks - each piece fitting perfectly to create a strong and resilient structure. This is exactly what we're doing as we prepare for extensive work in and near the Mangahauini River; a task that requires precision and creativity. Big storms, like Cyclones Bola and Gabrielle, have dramatically shifted the river, moving the riverbed several metres up, down, and sideways. Over past decades these changes have weakened the surrounding land, caused slips and undermined the road, leading to closures and delays for the community. To tackle this, we're constructing a 'roughened channel' in the river at the bottom of the gorge next to the sheet pile wall. It’s believed to be the first of its kind in a New Zealand river. Roughened channel – what’s it all about? Around half a kilometre of the riverbed will be shaped and lined with carefully placed rows of ‘hanbars’. These specially shaped concrete blocks will help contain the river at its steepest and more destructive section, with the new channel protecting the toe (bottom) of the sheet pile wall and keeping the river away from the road. The newly shaped riverbed will also support the rest of the river further up the gorge from ‘downcutting’ (eroding the channel) by holding back excessive sediment movements. This prevents erosion, reduces the river's energy, and keeps the riverbed stable over time. Starting mid-August, work in this area will ramp up. Stay tuned for more updates on this exciting project! 3D image of block design for the Mangahauini River.


	SH2: Final phase of Otoko Hill recovery to begin One year after recovery work started on SH2 Otoko Hill, the final 2 projects will get underway in early August. Site K overslip repairs will start first and take approximately 8 weeks to complete. We'll be installing or upgrading 48 drains to help reduce water pressure in the hill and subsequent movement in the road. Site M underlip repairs will take approximately 12 weeks to complete. These repairs include extensive drainage installation and construction of a buttress (supporting structure); similar to other recovery works undertaken in the area. To minimise disruption most work on these sites will take place off the road, under a shoulder closure. Stop/go traffic controls may be used at times, with expected delays of 5-10 minutes. Map showing completed and active recovery projects at Otoko Hill.


	Bridge building and…a dinosaur!? Ngā mihi nui Mata School for hosting some of our SH35 Hikuwai Bridge Replacement team recently. Mata School is one of the kura kaupapa that attended the project’s initial karakia hosted by tangata whenua in March this year. Located inland from Tokomaru Bay, the school was affected not only by the loss of Hikuwai Bridge No.1 but also by the damage to a vital connection on Mata Road, the route to Huiarua Station where the school is based. With main construction on the Hikuwai Bridge project starting soon, we shared updates on the enabling works completed so far. Afterwards, tamariki took on a fun 20-minute challenge to build a bridge using classroom materials. Teamwork, creativity, and plenty of enthusiasm led to the successful construction of 2 standing bridges, strong enough to hold the weight of a dinosaur! A big thank you to Mata School for the warm manaakitanga shown to our team. Read more about the Hikuwai bridge project here. Mata School students with their bridge creations (and dinosaur!).


	SH2: Hakanui Straight construction team ready for action Last week the TREC construction team working near Te Karaka was warmly welcomed by Te-Aitanga-a-Mahaki for a pohiri at the Tapuihikitia Marae. The team (including representatives from Jesse James Contracting Gisborne Ltd and Earthwork Solutions Gisborne Ltd) learned about the rich history and culture of the Te Karaka area. The cultural induction included powerful videos that recounted the community’s experiences during Cyclone Gabrielle, highlighting the significance of the Hakanui Straight project to reduce the risk of future flooding, and its importance to the hapū. Work on SH2 for the Hakanui Straight project (formerly known as the Nesbitt’s Dip project) started this week. We’re raising the highway by 3 metres and upgrading drainage, making it stronger, safer, and more reliable for everyday travel and emergency response. During the works, lane changes and stop/go traffic management will be in place; expect short delays (5–10 minutes) when travelling through the site. We’ll keep providing regular updates in this newsletter. Te-Aitanga-a-Mahaki welcomed TREC and local contractors with a pohiri at the Tapuihikitia Marae.


	Crews keep it rolling at SH35 Makarika Crews have almost finished work at 2 of 3 dropouts at Makarika on SH35 around 15km south of Ruatoria. The first dropout repair was completed last year, with the second (pictured below) almost complete and the third next in line. This section of road was damaged during Cyclone Gabrielle with both lanes closed due to scouring from Makatote Stream. The solution has been to use a geogrid reinforced fill with a buttress (supporting structure) to replace the road shoulder, which was eroded away. As you can see from the photo, rip rap (rock) armouring now sits alongside the river to stop it scouring (eroding) the buttress supporting the road above. Tying into this buttress is a culvert (large pipe), also visible in the photo. This has been extended to help water more freely drain from any road surface runoff. Waterways can cause significant damage to roads during weather events and these improvements will reduce future impacts.


	Under the bridge, on the job - keep an eye out As we near the final stages of the Rotokautuku (Waiapu) Bridge (SH35) strengthening project, we’d like to remind all road users that our crews are still actively working on the bridge structure. Workers may be in low-visibility areas such as under or nearby the bridge and work zones, and you might not see them right away. Thank you for slowing down and staying alert while driving near the bridge and expect a lane closure on the bridge with stop/go in place from late July for approximately 5 days. Further recovery work to protect the bridge base from scouring effects is planned and the team is working with local hapū in this space. We’ll keep you up to date with progress and start dates as we have them. Following strengthening work on the bridge, scour protection work beneath the bridge structure is planned.

State highway snapshot

Below is a snapshot of construction works either underway or coming soon. You can also view completed, current and future work sites on our interactive map.

Here are some of the construction terms we use:

Bund – embankment that creates a barrier
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 Stabilised Earth) – a retaining wall construction technique used to stabilise slopes
Rip rap - large rocks
Rock revetment – protection
Scour - erosion
Shotcrete – sprayed liquid concrete
Soil anchors/soil nails – a device used to hold, restrain and support structures
Willow wall – using willows as ‘living walls’ to stabilise slips

SH2 underway

Matawai Road – willow wall to stabilise slip.

SH2 coming soon (see Otoko map above)

Otoko Hill (site K) - overslip repairs.
Otoko Hill (site M) - underslip repairs.
Hakanui Straight (formerly called Nesbitt’s Dip) project.

SH35 underway

Hikuwai Bridge No.1 replacement – enabling (early) works.
Mangahauini Gorge - investigations to support future recovery work.
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 2 lanes by installing a soil anchor and shotcrete wall.
Kopuaroa Slip 2 – build a 250m long buttress to support SH35 and provide additional drainage.
Tōrere – underslip and overslip repairs.
Paronga - D9 Gully Site – buttress wall with MSE. Two faults to be repaired to reinstate state highway to 2 lanes.
Kemps Hill subsidence – buttress repair using a willow wall. Three faults to be repaired to reinstate state highway to 2 lanes.
Makatote dropout #3 – reinstating state highway to 2 lanes, buttress support and rip rap to prevent future river erosion.
Rotokautuku (Waiapu) Bridge repairs – strengthening works.

SH35 coming soon

Rotokautuku (Waiapu) Bridge revetment – repair the scour at the south end of the bridge and construct a major revetment with dolosse for future-proofing.
Makatote dropout #2 – buttress support and rip rap to prevent future river erosion.