The final bill for repairing SH1 through Mangamuka Gorge, south of Kaitāia, is just over $200m. Photo: Supplied/Waka Kotahi
The final cost of rebuilding State Highway 1 through Northland's slip-plagued Mangamuka Gorge has ballooned to more than $200 million.
The crucial transport link south of Kaitāia was destroyed by dozens of slips during a storm in August 2022, just 13 months after a previous year-long closure.
The original 26 slips increased to 38 following another storm in 2023, which bumped up the repair cost and delayed the reopening from the original target date of May 2024.
Originally the government committed $100 million to the project.
An NZTA spokeswoman told RNZ the final cost of reopening the gorge was $204 million.
That included "completion works" that would continue in the New Year, after the road had reopened to traffic.
The project's completion will be celebrated on 19 December, with Transport Minister Simeon Brown expected to travel to Mangamuka that day, and the road due to reopen to traffic the following day.
The rebuilding of SH1 through Mangamuka Gorge is believed to be biggest road repair project in Northland history, eclipsing the $84 million reconstruction of SH1 over the Brynderwyn Hills completed in June this year.
However, it is not New Zealand's single biggest road repair job.
That honour likely belongs to the North Canterbury Transport Infrastructure Recovery project after the 2016 Kaikoura earthquake.
Rebuilding SH1 and the main rail line between Christchurch and Blenheim cost about $1.3 billion.
Following the 2022 storm that destroyed SH1 through Mangamuka Gorge, there were fears the gorge might never reopen - as was the fate of some Northland roads after Cyclone Bola in 1988.
Northland MP Grant McCallum said he had quizzed NZTA earlier this year if the agency had considered finding a new route less vulnerable to storms and slips.
He had been assured alternative routes had been considered, but building a new road from scratch would also be expensive and could take much longer.
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