A digger with a ‘thumb’ attachment placing rocks – the construction team used harder rock washed down in the slips and other storm-generated debris to repair and rebuild the rock protection walls
Precise balancing act on Takaka Hill – By Iain MacIntyre
A complete rebuild of sections of weather-devastated State Highway 60 between Riwaka and Takaka at the top of the South Island has been advanced by the New Zealand Transport Agency (NZTA) while simultaneously balancing the need to re-establish access across the vital route.
Viewing the scene via helicopter in the immediate wake of ex-Cyclone Gita, NZTA system manager Frank Porter reported there had been 16 slips between Riwaka Valley and the summit of Takaka Hill, with “two sections of road completely washed away”. The hillside had completely collapsed at a site about 1.5 km west of Riwaka, taking most of the road with it.
Electronic signs have been installed on either side of the hill that update motorists of any delays or significant issues
“We’ve lost both lanes of some parts of the highway at this site, and the road will need to be completely rebuilt from the ground up,” he stated in late
February. “This is a narrow and confined site, and much of the work needed to rebuild the road won’t be able to be carried out while traffic is flowing
“We’ll need to balance the need to keep the road open as much as possible with the need to fully rebuild it as quickly as possible. It’s a big job which is likely to take several months to complete.”
As the only road route in and out of Golden Bay in the Tasman District, the state highway had been averaging 1300 vehicles per day prior to the storm, with this figure increasing in weekends and key tourist/holiday seasons.
“With no detour or alternative route, it was critical that we restored access into and out of the area as we have done in the past year through Kaikoura,” Mr Porter tells NZCN in late March. “There is work also underway to develop designs, go through the consenting process and plan construction works for those sections of highway which require major rebuild works.
“Similarly, the Manawatu and Taranaki floods of 2015 required an initial response to restore access for communities, while developing a longer-term plan to rebuild sections of the highway severely damaged by the floods.”
The Fulton Hogan team managed hill access while working to reinstate the road surface
To best facilitate access – which was restored in limited form within days of the storm – around the needs of construction works, a permitting scenario was introduced which initially entailed only essential vehicles being able to travel during specified times in guided convoy. Restrictions have progressively loosened and the travelling windows widened as the works have advanced.
“We have implemented similar processes in other areas where highway access is affected by storms, slips and earthquakes. Managed convoys also operated in Kaikoura, restoring access via the inland road via Waiau within days of the earthquake in November 2016,” Mr Porter says.
“First and foremost our focus is safety – for customers/road users and our crews. We are happy with the speed with which it was implemented and the way it developed to meet the needs of the people of Golden Bay,” he notes.
“We are now averaging more than 1000 vehicles per day during the week and 1900 on Sundays when the road is open all day.”
In addition to enterprisingly utilising harder rock washed down in the slips and other storm-generated debris in the repair and rebuild of rock protection walls, Mr Porter says the restoration has also provided the opportunity to improve and build greater resilience into the route.
“We construct to current design standards for all highway works, which means that events like this provide some opportunity to slightly improve highway alignment and lane width based on changing and more safety-conscious standards. We will also be designing in resilience for any future events, as we understand the importance of this route for the Golden Bay community.”
In this vein, Mr Porter notes there has very much been a human story behind the restoration, with people in the area undergoing considerable disruption and the wider community/organisations coming together to make best of the situation.
“Yes, the storm and the work to repair the road has been disruptive for people trying to get into and out of Golden Bay – not just tourists and holiday-makers, but people used to making regular visits to relations or friends living on the other side of the hill, or in hospital in Nelson, and people who have to make urgent medical visits to the hospital. We have been bowled over by the level of community engagement, understanding and goodwill from the community,” he says.
“In return, the Fulton Hogan team managing hill access has worked to ensure urgent requests were able to be fitted in wherever possible, and that urgent freight and other trips could be fitted into a midday permit-only convoy outside the morning and evening public convoys on weekdays and Saturdays.”
Access for truck-and-trailer units
Mr Porter also praises the work of the NZTA’s construction team throughout the project, which commenced with the clearing of debris from slip sites within days of the storm, and has notably led to the reintroduction of truck-and-trailer units to the route on 20 March.
“The crews have worked incredibly hard to reach this milestone,” Mr Porter states. “We’ve tested the route to make sure that a range of truck configurations can safely navigate their way through. Drivers will still need to take extra care around tight corners.
Drivers of truck-and-trailer units need to take extra care around tight corners
“We know that the restriction of no truck-and-trailer units has had an impact on Golden Bay businesses and the community, and we know the news that the
road was opened to them from midday on the 20th as part of the freight convoys and the normal morning and evening convoys came as a welcome relief.”
Rising to the challenge
Despite Cyclone Gita having wrought widespread impacts on the nation’s roading network hot on the heels of the Kaikoura earthquake, Mr Porter remains stoic about the NZTA team’s capabilities to continually rise to the challenges being presented.
“We have robust processes to manage these events. They are always a challenge and each site presents its unique challenges,” he says.
“The Takaka Hill site was extremely constrained. However, we have managed to at least reinstate a reasonable level of access which, whilst tested over the weekend of 24/25 March with more than 90 mm of rainfall, is proving to be reasonably reliable.
“It was great to see so many people visiting Golden Bay for Easter, with between 1800 and 2000 vehicles making the trip safely each day in both directions. On Good Friday, 2161 vehicles went over and back,” Mr Porter adds.
The NZTA opened the route for 24/7 access on Saturday 7 April, and all drivers can now safely use the one-way sections with the aid of manual traffic management (stop/go) and/or traffic lights.
“Winter is fast approaching and throughout this time we will maintain and care for the route to keep it open 24/7 to all vehicles. We will use this time to develop designs and gain consent and planning approvals for major construction work to start in time for the next summer construction period,” Mr Porter concludes.
Iain MacIntyre is an award-winning journalist who specialises in transport and infrastructure issues within New Zealand