The first piece of road has been laid on the new motorway replacing the narrow, windy and dangerous section of State Highway 1 between Puhoi and Warkworth.
Officially named Ara Tūhono, or "connecting path", the motorway has faced delays and cost overruns from the impact of Covid-19.
The motorway has also been dubbed by critics as a "holiday highway" for Aucklanders driving to beach homes at Omaha.
Before Covid hit, the NZ Transport Agency paid a joint venture of Fletcher and Spanish construction firm Acciona $83 million to cover delays at the northern end.
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A five-week shutdown at the tail-end of the earthmoving season when the sun was shining and the soil was dry cost a further $85m and pushed back the completion date by six months to May 2022.
The motorway will now cost $878 million, up from the original price of $710m.
NZTA senior project manager Andy Thackwray said the Covid-19 delays meant the contractors were not able to complete the final earthwork season over summer and autumn, which had a knock-on effect on the overall work programme.
"The project is now back up and running at full speed with about 500 staff on site."
Thackwray said the delays and cost overruns with Ara Tūhono are different to a similar-size project on Auckland's Northern Motorway, which faces a four-month delay after the five-week Covid lockdown.
He said the Northern Motorway works, which include a motorway link to the State Highway 16 western ring route, are in a different environment and were able to get up and running a lot quicker.
There would be extra costs for the $700m project, but they are still being worked on, Thackwray said
The Puhoi to Warkworth project is a public-private partnership (PPP) between the Government through NZTA and the Northern Express Group(NX2) to design, build and maintain the motorway for 25 years. NX2 has sub-contracted construction of the motorway to a joint venture between Fletcher and Spanish construction firm Acciona.
Project director Robert Jones said work is progressing well on two major viaducts just north of the Johnstones Hill tunnels and Puhoi at the southern end of the 18.5km motorway.
Currently, huge concrete girders weighing up to 50 tonnes each are being trucked to site from Napier and lifted on to the Puhoi viaduct using massive crawler cranes.
Four girders are lifted at a time - a total of 200 tonnes. Of the 52 girders, 26 have been installed on the 316m long viaduct, which is up to 21m high.
Jones said the two viaducts and seven bridges are due to be completed by about February next year for work to start connecting all the sections of the project and pave the road.
Just north of the viaduct, the first piece of road has been laid at a major cut in a hillside where 466,000 cubic metres of rock has been removed to create a 20m high rock face on the western side.
The first layer of the road consists of 300mm of graded and compacted rock. This will be followed by two layers of asphalt 180mm thick and a third, 50mm layer of porous asphalt.
The final asphalt surface is a low-noise surface, which allows water to escape, avoids wheel-spray and helps water run-off.
When the highway is completed, said Jones, it will be a spectacular drive through the countryside.
The drive north to Warkworth will feature natural forms, a kauri reserve at bridge level looking down on the Puhoi River, 50m-high cut slopes with layers of rock forms breaking out to valley views - all following a curved pathway.
Thackwray said it will chop 11 minutes off the current route and be a much safer and resilient drive for the 24,000 vehicles who use the road every day.
The motorway was consented in 2014 with flexible environmental and design thresholds. Work on the motorway, which runs west of the existing SH1, started in December 2016. By 2026, it is projected the new road and the existing SH1 route will cater for 35,000 vehicles a day.
The NZ Transport Agency has proposed a toll on the new motorway of $2.40 for cars and $4.80 for heavy vehicles.
This is the same amount charged for the Northern Gateway section of State Highway 1 from Orewa to the Johnstones Hill tunnels where the Pūhoi to Warkworth highway begins.
There will be a separate toll for each section of SH1 motorway, taking the cost of driving from Orewa to Warkworth to $4.80 for cars and $9.60 for heavy vehicles.
Pūhoi to Warkworth motorway project by the numbers
• $878m - cost
• 18.5km - length
• 4 - number of lanes
• 7- number of new bridges
• 7m cu m - amount of rock and soil to be cut
• 7km - culvert pipe system
• 750 plus - number of workers at the peak
• 35,000 - number of vehicles per day on new motorway and existing SH1 route by 2026
• May 2022 - opens to traffic