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Work on the Northland motorway corridor, Ara Tūhono Warkworth to Te Hana, has been focusing on investigations for the tunnel alignment in Mahurangi Forest.
This includes drilling boreholes as deep as 150 metres and at an angle to get a 3D view of the ground conditions to better understand fault lines in the area.
NZTA/Waka Kotahi has started moving machinery into some hard-to-access locations in the forest via helicopter. Equipment is being flown into each drilling site rather than cutting paths through the forest.
Helicopters are operating two days a week and will move machinery to 20 sites over the next couple of months for this current stage of geotechnical investigations.
In total, 49 boreholes have been sunk, representing 1385 metres in drilling in total.
Meanwhile, the emerging preferred corridor for the motorway north of Te Hana to Whangārei will be released in the first quarter of next year. This 100km stretch will be four-laned and will be constructed in two sections – Te Hana to Port Marsden Highway and Port Marsden Highway to Whangārei.
An emerging preferred corridor is typically 500 metres wide with the final design width of the highway likely to be between 60 metres and 100 metres, with additional width at interchanges and connections.
