It's taken more than $21million and 13 months of hard slog, but for the crews working in the Manawatu Gorge, there's satisfaction in seeing life return to normal for those who rely on the gorge road.

As the major route between the Tararua and Manawatu districts, the closure of the highway has had a significant impact on the surrounding communities.

Early on the New Zealand Transport Agency (NZTA) mobilised a team to clear the debris and stabilise the slope in the fastest possible time.

Quickly the decision was made to clear the slope from the top down instead of using the traditional bottom-up approach.


The vastness of the slip meant staff working at the top were 155m above the road and 231m from the river.

"It was pretty nerve wracking but we did it safely and effectively," said Higgins regional manager, Shane Higgins, a third-generation member of the roading and infrastructure company.

As motorists now travel through the gorge without the lengthy detours some have endured over the last 13 months, NZTA officials have been adding up the cost of the huge reconstruction. With $5.4million spent maintaining alternative routes, the Saddle Rd and the Pahiatua Track, the total bill for the project has reached $21.4million, NZTA Palmerston North state highways manager, David McGonigal, said.

"Our previous $20million figure was the estimate produced when the damage to the bridges and structures was first identified. And the $21.4million reflects actual costs now that the work is largely complete and includes additional drainage works and rock bolting that was not part of the $20million figure. This additional work will provide further stability and security of the slope to protect drivers."

The highway through the gorge was closed by a succession of slips, the first in August last year, followed by a massive slip on October 18, thought to be the largest slip to close a state highway in New Zealand.

Now a final completion date for all the work is coming closer after some of the most challenging conditions head contractor, Higgins, has ever encountered.

The whole project has been characterised by a strong level of collaboration and teamwork among NZTA, consultants and contractors and Mr McGonigal has praised Higgins. "This was a complex project with many challenges. I was impressed with their professionalism, dedication and can-do attitude in all kinds of inhospitable weather," he said. "The last 13 months has been one of the most difficult times in living memory.

"Higgins supplied us with accurate and timely information because it has been very important to keep the public informed about progress on re-opening the gorge.

"This section of highway has seen so much drama in the last year. It was host to the largest pile of dirt that's ever landed on a New Zealand road. Then it became a hive of reconstruction, and now, it's back to being a two-lane highway.

"The closure of the gorge has affected lives and livelihoods throughout the Tararua and Manawatu and beyond and we've been battling for more than a year to get to this point - having the road open again."

However, before work could begin on reconstruction of the road and bridges, the slope above had to be stabilised. "This required five 'benches' being cut into the hillside to create platforms to catch further debris," Mr Higgins said.

"Loose material from the cuttings was pushed down the sides to a waiting stream of trucks at road level. Grass hydroseeding of the benches was another smart technique used to encourage vegetation growth and further stabilise the slope.

"In May the last load of slip material was removed from the road and work on stage two, fixing the damaged road, began. However, it quickly became apparent the bridgework which forms the base of the road, needed to be completely written off and totally rebuilt."

Mr McGonigal concluded that building a new bridge spanning the area in such a challenging location would normally take up to 12 months. But NZTA wasn't prepared to keep motorists waiting that long and an accelerated programme was put in place to build the road in four months.

"This meant shoehorning a mind-bogglingly complex operation into a few months, on a tricky, constrained work site, with traffic passing through for weeks at a time," he said. "It's the kind of operation that normally would have taken a couple of years to plan and build. But we were conscious that every day was costing businesses and families, and we had to find a way to get it done quickly."

A 60-metre-long bridge was constructed involving a team of consultants and contractors working extended hours.

"But 13 months has been a long wait for the people of the region," Mr McGonigal said. "We appreciate that travelling over the alternative routes hasn't been a picnic and that every journey cost fuel, money and precious time.

"Thank you to the businesses in Woodville and beyond for being so understanding. Our crews have often popped in for a slice of cheesecake, a pie, or a piece of fish and we've been frankly humbled by the warmth, resilience and good humour of the business owners who have been up against it for more than a year.

"And the teams at the coalface deserve a standing ovation. These crews have defied superlatives and Mother Nature. I've never seen such a hungry, dedicated bunch of people. Their utterly dogged and heroic drive to get the gorge re-opened never faltered. They were in a race against time every step of the way. They were up against some of the most hostile conditions imaginable, howling winds, raging rain and floods and heights that would give most of us a serious case of vertigo. They knew the region depended on them. And, boy, they delivered."

Gorge facts:

  • The slip which closed State Highway Three through the Manawatu Gorge in 2011 was the biggest in New Zealand's history.

  • The road was closed for 13 months.

  • 370,000cu m of earth, stone and other debris were removed from the site - the equivalent to filling Wellington's Westpac Stadium or a bath in every New Zealand household.

  • Carting that material has taken 53,000 truck movements.

  • At the peak of reconstruction crews worked 70-85 hours a week, seven days a week.

  • Original estimates to repair the road were $11.5million but after crews finished clearing the slip material from the road, the bridges that had been buried for nine months were found to be beyond repair.