Major milestones reached for New Zealand’s Manawatū Tararua Highway project

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Construction crews building New Zealand’s 11.5km Manawatū Tararua Highway achieve major milestones across its earthworks, landscaping, and structures programmes.   

Te Ahu a Turanga: Manawatū Tararua Highway continues to achieve major milestones as the third year of construction draws to a close.

Since starting construction in January 2021, the team constructing the new 11.5 kilometre-long highway between Ashhurst and Woodville, which will replace the old road through the Manawatū Gorge, has made excellent progress across its earthworks, landscaping, and structures programmes.   

Digging deep

In August this year, earthworks teams hit the target of six million cubic metres of earth moved, which included the completion of Cut 13, the biggest cut on the project with 2.2 million cubic metres of earth being shifted.

Project spokesperson Grant Kauri says the teams are focused on finishing the remaining bulk earthworks by the end of the year. 

“The bulk earthworks is the movement of large volumes of earth before the final layer is trimmed and made ready for the road surface, or pavement, layers to go down,” says Mr Kauri. 

“The earthworks teams worked hard this year and, despite facing a particularly wet winter, we expect the final 400,000 cubic metres of earth to be moved by the end of this month.” 

Working alongside the earthworks teams are the drainage crews, who have completed about 4.5 kilometres of about 9 kilometres of network drainage and 5.5 kilometres of 35 kilometres of pavement drainage. 

With earthworks finished in parts of the project, the pavements teams started work at the Ashhurst end of the road in June.  

The pavement for Te Ahu a Turanga is about 70-centimetres thick, made up of layers of aggregate before being sealed with asphalt. In total, 450,000 tonnes of aggregate – about 16,000 truck and trailer loads – will be used to build the highway. 

Tree-mendous landscaping

Another major milestone was the planting of the one millionth plant– a manoao (silver pine) – which was planted alongside the highway in September.  

This year the landscaping teams planted 300,000 plants. Most of these were planted in areas next to the highway, a change from previous years, where most of the planting happened at sites away from the road. By the end of construction, the landscaping teams aim to have about 1.8 million native plants in the ground.

Bridging the gap

The structures teams made huge progress in 2023, with all three piers at Parahaki Bridge over the Manawatū River being completed, and the first form traveller being installed on Pier 1. 

The form traveller allows the concrete bridge deck to be constructed in sections, with a section being poured on both sides at the same time so it balances.

Eight segments are due to be completed by the end of this year, and all 27 segments are expected to be completed by late 2024. 

Over the river at the Eco-Viaduct – a 305-metre-long bridge crossing an ecologically sensitive wetland – all 42 of the steel girders are now in place on the piers.  

Mr Kauri says completion of the beam installation is a remarkable achievement.  

“Getting these beams – which are up to 47-metres long – onto the site and up on the piers is a complex operation. On top of that, the team has overcome massive challenges to get this bridge to this point, including facing unprecedented artesian water pressure issues, which delayed construction of the piles by 14 months. Despite those challenges, they have managed to get the Eco-Viaduct back on schedule.”

With the girders in place at the Eco-Viaduct, attention moves to construction of the bridge deck, which has begun from the northern approach.

Project milestones

Mr Kauri says while the construction achievements are impressive, there are other aspects to the project that are equally as important. 

“I’m particularly proud of how the project continues to set new standards for iwi partnership, health and wellbeing, and broader outcomes. These are the things that ensure we leave a legacy that lasts long after the highway opens in mid-2025.

“I’d like to thank the Te Ahu a Turanga Alliance partners and their teams for all their hard mahi throughout 2023,” says Mr Kauri.

“I’d also like to thank the public for their support and continued interest in this project. We look forward to sharing more about the progress of this vital North Island connection with the public throughout 2024.”

Source: © 2023 Waka Kotahi NZ Transport Agency

Image Source: © 2023 Waka Kotahi NZ Transport Agency

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