Te Ahu a Turanga; Manawatu-Tararua highway: While Parahaki Bridge is structurally complete, the teams still have plenty of work to do until it’s finished, such as installing barriers and placing the asphalt surface.
Te Ahu a Turanga; Manawatu-Tararua highway: While Parahaki Bridge is structurally complete, the teams still have plenty of work to do until it’s finished, such as installing barriers and placing the asphalt surface.
Opinion
By Grant Kauri, Project Spokesperson, NZ Transport Agency Waka Kotahi
Nearly four years after teams started working on a new Manawatū River crossing, the final concrete section of the bridge deck has been poured, which means the entire highway is now fully connected.
The Parahaki Bridge – named after Parahaki Island on which the bridge’s central pier sits – is a 300-metre-long structure that stands as one of the key features of Te Ahu a Turanga: Manawatū Tararua Highway.
The bridge is about 100 metres south of another major structure, the 305-metre-long Eco-Viaduct, which was also recently completed.
Both bridges are structurally complete but there is still plenty of work to do before they are ready for traffic. They both still need their barriers installed and asphalt placed on the bridge deck. On Parahaki Bridge, the viewing platform, which will provide stunning views of the Te Āpiti – Manawatū Gorge, also needs to be attached.
A viewing platform on the eastern side of Parahaki Bridge will offer spectacular views of the river and the Manawatū Gorge from Te Ahu a Turanga: Manawatū-Tararua Highway.
Construction teams celebrated these huge milestones in November by doing a walkover of both bridges before stopping at the centre of Eco-Viaduct to reflect on their incredible achievements.
Building Parahaki Bridge was never going to be easy due to the challenges presented by flooding, high winds and the risk of earthquakes. Added to that are the engineering complexities of having to build a bridge that has a curve and camber rather than a straight line. Rising 30 metres above the river, work started on drilling the 55-metre-deep piles into the ground in July 2021.
Since then, a total of 300,000 hours have gone into this bridge, with up to 110 people working on it at any one time.
The 305-metre-long Eco-Viaduct (foreground) lies about a hundred metres north of Parahaki Bridge, which crosses the Manawatū River.
Like Parahaki Bridge, the Eco-Viaduct also had its complexities, particularly when it came to constructing the piles. When engineers started drilling the holes in the ground to pour the 16 piles, they encountered unprecedented groundwater pressure.
This meant that the holes would collapse under the pressure, making it impossible to construct the piles. This delayed their construction by 14 months while they came up with a solution that involved diverting the groundwater to relieve the pressure.
However, they soon got back on track and by March 2023 most of the 12 columns – concrete poles that support the bridge deck – were finished and ready for the placement of the steel girders.
All the beams were in place by November 2023, and the bridge deck – comprised of 750 concrete panels with an extra layer of concrete on top – was completed in August 2024.
The team has put 80,000 hours into this bridge, completing it on time despite those early delays.
While work continues on the bridges, the pavement crews continue to make good progress in constructing the road surface.
About 6km of the 11.5km main alignment is now covered with asphalt, with the team expecting to complete this by early 2025.
Installation of the wire rope barriers is also underway in parts of the highway where the road surface is completed.
If you want to learn more about the project, head to www.nzta.govt.nz/projects/te-ahu-a-turanga/ or visit the Woodville Community Library and Information Centre for the latest flyover, project updates and the Drive the Highway simulator.
