Te Ahu a Turanga: Exciting final 12 months for highway build

Wednesday, 8 May 2024

Owner Interface Manager at Te Ahu a Turanga Alliance Grant Kauri talks about progress on Te Ahu a Turanga – Manawatū Tararua Highway between Ashhurst and Woodville.

Excitement is building in step with the road, as the massive highway project in the hills between Manawatū and Tararua enters its final 12 months of construction.

Weather looms as the most formidable challenge remaining for the 11.5 kilometre Te Ahu a Turanga highway as the focus shifts from earthworks to paving and the completion of a bridge and viaduct.

Crews were busy stabilising the subbase of the highway alignment, laying chipseal and running asphalt trials, when the Manawatū Standard visited the site on Tuesday.

The four-lane highway was being built after slips permanently closed State Highway 3 through the Manawatū Gorge in 2017 and forced motorists onto the Saddle Rd.

The shared pathway, for walkers and cyclists, is pictured on the right, above the highway route. Like the road, the path runs for 11.5 kilometres.

Project spokesman Grant Kauri said this work would continue through winter but they would adapt to conditions when required.

“The main thing is around having that good weather. And the [asphalt] trial here is testament to making sure we have the product right and the process all ironed out before we run the main production.

Project spokesman Grant Kauri with the under construction Parahaki Bridge in the background. It spans the Manawatū River near the old gorge road route.

“We get continuous wet days, that has an effect on when we can pour. We just need to maximise the good weather that we have.”

December 2023 NZTA Waka Kotahi progress update video on Te Ahu a Turanga: Manawatū-Tararua Highway

Given some of the obstacles encountered during the previous three years, a few wet patches would be a welcome minor adversary.

Covid, Cyclone Gabrielle and a much higher than expected water flow beneath the viaduct had provided enough obstacles to push back the project’s scheduled completion by six months to mid-2025.

Kauri, the owner interface manager for Te Ahu a Turanga Alliance and Waka Kotahi, said it was a relief to have the bulk of the earthworks in the rear-view, and he was excited at the thought of the highway really taking shape over the next six months.

When the public again had the chance to walk the highway in January, he said they would get a real appreciation for what the completed highway would look like.

A crew working on the subbase at a section known as Cut 13, where 2.2 million cubic metres of earth was removed from the hillside.

“We’ll have a lot of our asphalt down, finished surface and line marking. They’ll really get that almost-completed feel for what the alignment looks like and what we’ve been working towards over the last four years.”

A wire rope median barrier would run the length of the highway except for the bridges, where there would be solid concrete barriers.

Covid and increasing costs, particularly the surging fuel price, had provided financial pressure, but the project was still working to a $620 million budget.

Asphalt being trialled on a section of the alignment.

“The main driving force for construction is the price of diesel, and you would have seen how that’s doubled in price. So those are the kind of effects,” Kauri said.

“We’re a big project, we’re not immune to those sort of costs. But we are still reviewing what that looks like.”

The Eco Viaduct is expected to be completed by the end of 2024. Parahaki Bridge, in the distance, should be finished a few months later.

Between 300 to 350 people were working on site each day, 80 dedicated to Parahaki bridge, while more than 2 million worker hours had been logged since 2021.

Two teams were working concurrently on the Eco Viaduct and Parahaki Bridge, the latter a balanced cantilever spanning the Manawatū River, where concrete segments were being poured.

All beams for the viaduct were now in place and it was on track for completion by the end of this year, and Parahaki Bridge a few months later.

Just as the highway takes shape, so too does the shared pathway for walkers and cyclists that will run the full length of the highway, though weaving its own route.

Sections we viewed, about 3km from the Ashhurst end, snaked around ponds and ridges, not far from towering wind turbines. Its recreational appeal was plainly apparent.

Though there would be quite steep climbs at both ends of the 3m-wide path, Kauri said it was designed to be suitable for a range of fitness levels. 90% would be chip-sealed, and the remainder, at the Ashhurst end, asphalt.

For motorists, the 10% gradient on the Ashhurst side of the highway, and 8% on the Woodville side, are comparable to the climb and descent on Transmission Gully (8%).