Work to repair the State Highway 4 slip near Upokongaro will begin in March, Waka Kotahi/NZTA regional transport systems manager Ross l'Anson says.
A section of the state highway at Kukuta slipped into the Whanganui River after flooding in 2015, l'Anson said. That stretch of road became single lane and controlled by lights.
To enable repairs to be made the agency needed to purchase an adjoining property, and that was completed in January.
The news has thrilled Whanganui district councillor Helen Craig, who has been vocal about repairs to the highway.
"I'm thrilled they have finalised the purchase at long last. It did take far too long," she said.
An initial repair to the section at Kukuta failed and sank in 2017, l'Anson said, "due to unforeseen ground conditions".
At that time local man Donald Wickham told the Chronicle the ground there is a soft pumice, with underground streams joining the river at a place where current is fast and the water is deep.
The highway will now be diverted away from the slip which will provide a long-term solution, I'Anson said. The work will be finished in October.
I'Anson did not respond to the Chronicle's questions about how much land has been purchased or how much the repair will cost. He did not provide any information about the property owners, but Craig believes the family were willing sellers.
Craig emailed Waka Kotahi about the state of SH4 through the Parapara in November 2019. Early the following year she and Annemarie Horrocks organised the agency to front up to a meeting of Parapara farmers.
At that meeting l'Anson admitted that a lack of maintenance had made issues on the Parapara worse, Craig said. He also made a commitment to have all the slips on that stretch of highway fixed by the end of this year.
"Fundamentally, I think they've got a funding issue, but also they had a change of method around maintenance," Craig said.
"They thought that the road would still be okay [with less maintenance] and they found that wasn't correct."