Major repair work on State Highway 4 Parapara Rd almost finished

Members of the local community on their way to the latest round of planting at the site. Photo / Finn Williams

A State Highway 4 Parapara Rd repair job that began at the start of last year is nearing completion.

Contractors on the Auraki Stream road retreat project are relocating 400 metres of highway away from the Mangawhero River slip site.

It is the largest of 40 different slip sites caused by major flooding in 2015 and it is the last of the initial sites to be fully repaired.

Project manager Malcolm Chiles, from Waka Kotahi NZ Transport Agency, said workers had to dig away at the hillside to make way for the road.

One of the major difficulties was geotechnical engineering to ensure it wouldn’t collapse again, he said.

The hill that was dug out measured 55m in height, with a lot of variation in its soil types.

Chiles said one of the most surprising discoveries was river gravel at the top of the hill.

“So, the river or the stream was way up at that level at one point in time,” he said.

“We put in some big rock bolts and mesh just to stabilise that ground.”

Another major obstacle they faced was rainfall, as the unstable ground meant any rain forced work to a stop and the focus shifted to maintaining the site and making sure no dirty water went into the river.

“It’s been a hard slog over the last 20 months with all this rain and when you’re in the thick of all that, it can get you down a bit.”

Chiles said he was proud and relieved to have the project to the point where it was nearing its conclusion, despite the setbacks.

It will be sealed, marked and fully operational for road users in the next six weeks, depending on the weather.

“We just need the weather to dry things out a bit and then we’ll be into the sealing,” he said.

Chiles said he was also proud of the joint work done by Waka Kotahi, designers Beca Group, contractors Higgins and Mills Albert, and Māori partners Ngāti Rangi, Uenuku and Te Korowai o te Awaiti.

“For me what was really special about this was that we came together and we used this philosophy of co-design,” Chiles said.

“Co-design was all about us sitting in a room and discussing concepts, coming up with ideas.”

Those relationships led to Waka Kotahi organising a planting day around the road for members of each group and children from area schools.

Aberfeldy School, Kakatahi School and Te Kura Kaupapa Māori o Ngāti Rangi helped with the first of the plantings, along the banks of the stream near the road.

Planting had been required to fulfil the project’s environmental obligations but what they were doing went above and beyond that, Chiles said.

Waka Kotahi planned on 11,000 plants for the project.

“It felt right in the area we were working in to extend the area of the planting,” he said.

He was told kererū were watching over the workers at the start of the project so they planned on planting fruit trees near the road to attract the birds back to the area, Chiles said.

The plants would also help stabilise the land around the road, preventing slips from happening again in the future, he said.

Work in the areas surrounding the road will continue for a while longer.

“This is the road that keeps on giving, we’re getting slips all the time and it is a challenge to keep up with it all.”

Repairs have already been completed at Hapokopoko Curve Rock, Whiskey Corner, South Raupio Retreat, Otoko Pā overslip and north of Kukuta Rd.

Finn Williams is a multimedia journalist for the Whanganui Chronicle. He joined the Chronicle in early 2022 and regularly covers stories about business, events and emergencies. He also enjoys writing opinion columns on whatever interests him.