The crucial Coromandel link State Highway 25A will reopen on 20 December - three months ahead of schedule.
The construction project includes a new 124 metre bridge to span a large washed out section of the severed highway.
The road, a crucial route across the Coromandel Peninsula to towns like Whangamatā, Tairua and Pauanui, was damaged earlier this year when a large chunk was washed away in storms.
The eastern side is a popular summer holiday area, and in October, Thames-Coromandel Mayor Len Salt said the local economy had already lost $30m since its closure.
A before (above) and after composite picture of the damaged section of State Highway 25a and the new 124m bridge. Photo: Waka Kotahi
Waka Kotahi regional infrastructure manager Jo Wilton told Checkpoint they were thrilled the road would open in time for the peak of summer holidays.
Three months early & under budget: SH 25A to be ready for Xmas
The team had taken a hard look at strategically speeding up the construction process, she said.
"That was building as much as we could at the same time off-site, so when we brought it to the site it was like a giant Meccano set and literally you're just assembling it."
Wilton said between 70 and 100 people worked on-site during most of the construction process, with about the same number of people working on pieces off-site.
"A lot of planning and a lot of very very hard work, and some incredible hours worked by the team. It's things like working 24/7 at the Eastbridge [Steel] factory building those beams so that they didn't hold us up on site. Working seven days a week to get the piling done, and seven days a week to get those deck panels in."
At the moment the bridge was complete enough that someone could walk across it, but "you can't put a car on it, yet," Wilton said.
The cost of the completed project is now expected to be about $43 million, less than earlier estimates of up to $50m.
"Because it has taken us less time than what we envisaged - that's what's brought it under budget," Wilton said.
The project included work to strengthen and future-safe the entire route from big storms in the future, with about 24 new culverts built along its length.
"Our team has done an amazing job, not only constructing the new bridge in record time, but at the same time we've invested an additional $25m to enable multiple crews to clear slips, replace the original undersized culvert, and undertake crucial road maintenance work along the rest of the length of SH25a to ensure the whole corridor is up to scratch, safe and more resilient," she said in a statement earlier.
A large chunk of SH25a was washed away in severe weather. Photo: Tom Taylor / RNZ
Usually this type of bridge would take 12 to 14 months to construct, and it was a huge achievement to get it open in less than seven months, Wilton said.
"We are so stoked to be able to advise the public of [the opening date], because the biggest driver of this project was to get it open as quickly and obviously as safely as we could."
The entire project may not be fully complete by 20 December, she said. But after the road opens in both directions on 20 December it was not expected to be closed again for more work, with the final finishing touches including less disruptive things like re-planting along the highway in the new year.