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TREC Tairāwhiti recovery update

Issue 19

17 April 2025

Tēnā koe

In this edition, we bring you an update on Hikuwai Bridge early works and reveal how fish scales play a surprising role in protecting aquatic species as we work.

Plus, get the details on the upcoming roadworks ‘pause’ over the Easter and Anzac holiday break to help you get around easier and information about how work on State Highway 2 (SH2) is progressing.

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


	Pause on roadworks coming up The NZ Transport Agency Waka Kotahi (NZTA) often put roadworks on hold during busy holiday periods to help keep traffic moving and avoid delays for travellers. Aside from the odd site – for example, emergency repairs – most roadworks will stop during the following times for Easter and Anzac holiday periods: Over Easter, from 12pm Thursday 17 April until 23.59pm Monday 21 April From 12pm Thursday 24 April until 23.59pm Sunday 27 April for Anzac Day The days between Easter and Anzac Day are working days for crews. Traffic management will remain at some sites on non-workdays to keep everyone safe.


	SH35: Hikuwai humming Crews are getting stuck into the enabling works for the permanent replacement bridge at Hikuwai. Over the past week, work has included flattening and grading the ground for the site office and laydown areas, along with vegetation clearance. Contractors are also focused on building a temporary road on the southern side of the bridge. This will realign the existing State Highway 35 (SH35) to enable construction of the southern bridge abutment (bridge support) and provide a safer, more spacious workspace for bridge construction. The road will connect to the Bailey bridge on the southern side and will be operational when the main bridge construction begins. Local contractors have been appointed to the enabling works packages with Parata Ltd undertaking site set-up and the temporary road construction and Currie Construction set to demolish the old bridge. 3D drone footage showing extensive clearing and levelling work at the northern end of the Bailey bridge.


	SH35: Mangahauini Gorge work progressing well Crews have finished restoring the Mangahauini River back to its pre-cyclone flow path, removing enough soil, rock and other landslide debris to fill 4 Olympic-sized swimming pools (10,000 cubic metres) in the process. During Cyclone Gabrielle, a major landslide near the lower end of the gorge sent a massive flow of debris into the river, blocking its usual path. The river overflowed and washed away parts of SH35, carving a new channel. Eventually, the river ended up flowing between the highway and the sheet pile wall designed to manage water and keep it away from the road. TREC crews got to work and our ecologists started relocating eels and fish to another part of the river. Local crews from Blackbee Contractors and Kuru Contracting worked to excavate slip debris from the side of the sheet pile wall, restoring the river to its pre-cyclone flow path. Preserving water quality and protecting aquatic species, as well as the local bat population, were central to this work. The team implemented stringent environmental controls, supported by local kaitiaki. Other work that finished this month included emergency works to protect the sheetpile wall downstream. There’s still a lot more work to do in the Mangahauini Gorge - keep an eye out for updates about future work in the coming months. A before and after showing the Mangahauini Gorge river flow restoration.


	What the tech? You've heard of DNA—the unique code that makes us who we are. How about eDNA? Environmental DNA or eDNA is one of the tools that helps the TREC environmental team keep aquatic wildlife safe as we carry out recovery work. Every fish, eel, or small critter in the water leaves behind tiny traces of DNA—scales, mucus, or even poo. By collecting and sending water samples to a lab for analysis, our ecologists can read these eDNA clues to figure out what species are around. TREC uses eDNA testing to check for various species before starting certain projects, especially those involving river diversions, such as in the Mangahauini Gorge. If the eDNA results tell the ecologists something is in the water, they know it’s time to bring in the nets and carefully relocate them to a safer spot before work begins. While it’s used more in aquatic environments, eDNA can also be collected from soil, sediment, or even the air to detect traces of plants, animals, or microorganisms in those ecosystems.


	All go on SH2 From Tuesday 24 April, crews will begin work to repair an overslip site on Matawai Road, where loose debris above SH2 needs to be removed to prevent it falling onto the highway. Stop/go traffic management and a lane closure will be in place for the duration of works, which is expected to take 3 weeks, weather permitting. Two days of tree removal will take place before main works begin. Crews will work between 7am and 5pm, Monday to Friday. Find out about other SH2 work by reading this traffic bulletin.


	SH35: Karakia ahead of Tōrere slip repair work starting Our work in the Eastern Bay of Plenty continues. Crews are repairing an underslip at Ōpape with gabion baskets, with work expected to be complete in May. Later this month we will start to repair 2 slips by Te Kura O Tōrere in Tōrere. In preparation, a karakia was held by tangata whenua and locals earlier this month at Te Kura O Tōrere. Locals Papa Rangi and Carlos Ahlers led the karakia and tamariki from Te Kura O Tōrere were involved in the day, singing waiata. TREC Pou Ārahi Tairāwhiti Nancy Tawara said it was very humbling for the TREC team. “The Kura tamariki were such a highlight. Hearing our reo, practices and customs was fantastic - they are an absolute credit to the Kura, Iwi and community who grow and nurture them.” Te Kura O Tōrere tamariki sung waiata at a karakia on 8 April, held ahead of the Tōrere slip repairs project starting.

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:

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 (see Otoko map)

Otoko Hill Slip #2 (site G) - hill stabilisation using soil anchors, shotcrete, and rip rap
Otoko Hill (site B) – tree removal and major drainage to stabilise slopes
Otoko Hill (site J) – retaining wall repairs and drainage installation
Rakauroa – repair underslip using soil anchors and shotcrete.
SH2 coming soon
Matawai Road – willow wall to stabilise slip.

SH35 underway

Hikuwai Bridge No.1 replacement – enabling (early) works
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 programme of work
Mangahauini Gorge early works - river training and sheet pile wall strengthening
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
Opape underslip – buttress repair with gabion wall.

SH35 coming soon

Kemps Hill subsidence – buttress repair using a willow wall. Three faults to be repaired to reinstate state highway to 2 lanes
Tōrere – underslip and overslip repairs
D9 Gully Site – buttress wall with MSE. Two faults to be repaired to reinstate state highway to 2 lanes
Waiapu revetment – repair the scour at the south end of the bridge and construct a major revetment with dolosse for future-proofing
Rotokautuku (Waiapu) Bridge repairs – strengthening works
Makatote dropout #2 – buttress support and rip rap to prevent future river erosion
Makatote dropout #3 – reinstating state highway to 2 lanes, buttress support and rip rap to prevent future river erosion.