The new Pūhoi to Warkworth motorway is a dramatic kaleidoscope of scenes that will wow motorists when it opens.
The 18.5km route north is in a different league to the stretch of State Highway 1 it is replacing - like getting off a goat track on to a world-class motorway.
“The experience driving through will be awesome, it is such beautiful country and the road is striking,” says Waka Kotahi national manager of commercial delivery Andrew Robertson.
Robertson and other staff from the transport agency gave the Herald an exclusive drive on the new motorway this week, from north to south and back again in utes driving within the speed limit of 50km/h.
The speed limit is there because, despite appearances, the motorway is still a work site undergoing rigorous quality and safety checks that require last-minute fixes before final sign-off by an independent reviewer
After two Covid-impacted delays - it was due to open in the summer of 2021/22 and then at Queen’s Birthday Weekend last year - the motorway, named Ara Tūhono, or “connecting path”, is due to open in the coming months, chopping 11 minutes off the drive north.
Last June, motorists got their first experience of the motorway when Waka Kotahi opened the impressive Arawhiti ki Ōkahu viaduct at the southern end for a short drive before getting off and back on to SH1.
A couple of kilometres up the road at the Pūhoi turnoff spans a second viaduct before the four-lane motorway begins an undulating and curved path following the natural contours of the land as much as possible with low plantings of flax, toetoe, and native shrubs adding to the scenery.
Halfway along the route are a spectacular series of steep cuts of Pākiri sedimentary sandstone and siltstone up to 65m high in thin horizontal layers and brick-like patterns laid over with wire mesh.
The steep cuts stabilise vegetation on top of the hills and give a sense of penetrating through the rock face.
“It was literally moving mountains,” said Robertson, referring to three summer seasons of cutting more than 10 million cubic metres of earth and rock and filling another 5 million cubic metres to level the valley floors for a relatively flat road surface.
At the halfway point sits the steel Moir Hill bridge spanning two of the giant cuts at the steepest stretch of the road with a third, crawler lane each way for trucks and other slow vehicles.
Driving on from the dramatic cuts in the hillsides comes farmland and a large forestry block scared by numerous slips from the recent storms and piles of slash in areas that have been harvested.
A prettier picture emerges towards Warkworth at the 75m long Arawhiti Pua Ngahere (Kauri Eco Viaduct) crossing a stream to a kauri forest and other significant native trees, almost within touching distance of vehicles.
As the motorway approaches a new roundabout joining up with the existing SH1, north of Warkworth, there’s grassed knoll on the left, and fluttering in the breeze are four blue and yellow Ukranian flags. Nothing to do with Waka Kotahi or the NX2 private consortium responsible for designing, building, and operating the motorway for 25 years, but a nice sight all the same.
South of the roundabout, Auckland Transport is putting the finishing touches on the 1.3km Matakana link road costing $62 million that avoids Warkworth’s infamous Hill St intersection and is due to open around the same time as the motorway.
The motorway is expected to be a boon for the town of Warkworth, which is forecast to grow from a population of 6600 to more than 25,000 over the next 25 years. The town is already growing faster than the Auckland average and had 456 new homes consented in the past five years.
Motorway designed and built to handle storms
When the summer storms battered Auckland, the new Pūhoi to Warkworth motorway coped well but the existing state highway suffered significant slip damage.
At Pūhoi and Dome Valley, the floods on January 27 closed SH1 in both directions that night and the new Pūhoi to Warkworth motorway was opened to escort stranded motorists under health and safety protocols for two hours between 2am and 4am.
When Cyclone Gabrielle pounded the region there were slips at Schedewys Hill, flooding in Pūhoi and multiple trees down. These events required lane closures.
By comparison, said Waka Kotahi’s Andrew Robertson, the new motorway was relatively unscathed by the double punch, with a “few bits and pieces” on the new motorway requiring tidying up. On a drive along the motorway this week, the Herald saw the scars from a few small slips, but nothing major.
Robertson said this is a reflection of modern design stands for building roads, a far cry from how roads were built 30 to 40 years ago.
“Minor pieces of damage were easily rectified, but there was significant slip damage on the existing state highway network,” he said.
The new motorway has a stormwater system engineered and built to handle the terrain and a 1-in-100-year flood. It has 46 culverts, including the 11-barrel culvert structure for flood relief at the northern end; extensive swale drainage, and numerous stormwater ponds.
There’s also a porous asphalt surface to help with water run-off and about 1 million native plants have been planted to soak up water.
When the motorway is finished, says Robertson, it will be a safer, more resilient and reliable route between Auckland and Northland.
Major connections between the provinces have been severed during the storms with SH1 through the Brynderwyns closed due to slips and a massive slip closing the main railway freight line between Auckland and Northland for months.
Pūhoi to Warkworth motorway project by numbers
• $878 million - cost
• 18.5km - length
• 4 - number of lanes
. 100km - speed limit
• 7 - number of new bridges
• 10 million cubic metres - amount of rock and soil cut
• 7km - culvert pipe system
• 750 plus - number of workers at the peak
• 35,000 - number of vehicles per day on the new motorway and existing SH1 route by 2026
• April-June 2023 - fully opens to traffic
