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Source: New Zealand Transport Agency

The first vehicles in five months have driven safely through the Mangamuka Gorge on State Highway 1, five months after it was closed by slips in a 1-in-500 year rain event.

The road opened just after midday today, and will be open for just over three weeks over Christmas to allow the local community and holidaymakers to take the shortest route to Kaitaia and the Far North. 

“Opening the road is a great achievement for our road repair crews. They’ve worked double shifts to a tight deadline in trying conditions to make this happen. Now they can take a rest while the people of the Far North and holidaymakers from further south take advantage of their work,” says Waka Kotahi Northland System Manager Jacqui Hori-Hoult. 

“We know how important this holiday period is to the local economy and we thank the local community for their understanding and patience while we worked as quickly as possible to fix the road. Now we can all enjoy Christmas.” 

The road is open to a single lane for motorcycles, private cars and other class 1 vehicles, with traffic lights controlling vehicles past the slip which has closed the gorge since July. Trucks and buses will continue using the detour route SH10.

 Class 1 vehicle information

There is also single lane access past another slip around 200m away from the main slip. This will be controlled with Give Way signs, as on a one-way bridge. There will be a 50 km/h speed limit through the gorge. 

Ms Hori-Hoult says there will be electronic signs before the gorge to remind drivers of vehicles that can travel through the gorge. 

“The road is narrow in some places with newly installed roadside barriers to stop vehicles getting too close to the edge where there have been slips. 

“Drivers are advised to plan ahead, keep to the temporary speed limit and allow extra time for the journey through the gorge. There may be delays getting past the slip site but that will depend on the amount of traffic. 

“Last Friday, the repair team celebrated the completion of 31 piles needed to support the road so it can safely open to traffic. They’ll be back in the New Year to complete the piling work and realign the road, restoring it to two lanes. 

On 11 January, the road will be closed again to complete the piling and start on Stage 2 of the repair, which is to cut into the hillside to realign the road and restore it to two lanes. 

The drilling rig and other equipment used on the big slip will move a few hundred metres up the road to fix our second slip where the road has dropped and is reduced to one lane. 

“The repair work at both slips takes up the full width of the road so we have to balance opening the road to let traffic through with just getting on and completing the repair as quickly as possible. We are asking our contractors if we can keep a lane open part-time as we finalise our building methodology to see what is achievable and practical,” says Jacqui Hori-Hoult. 

“At this stage we plan to have the road at both slips restored to two lanes by mid-2021, but it could be sooner depending on the weather and work progress. We’re committing all available resources to getting it done as soon as possible.” 

SH1 through the gorge road was closed by eight slips after heavy rain hit Northland in July causing extensive flooding and road closures. The big slip under the road on the northern side of the summit has kept the road closed since then.

SH1 Mangamuka Gorge slip repairs project website

Mangamuka Gorge repair works.

MIL OSI New Zealand News