"[...]it was necessary to ensure that the ground conditions could support bringing such a large piece of equipment through the slip site before moving the machinery in," Hori-Hoult said.
"Conditions in many parts of the gorge remain highly unstable, and the ground is still moving."
She said a further slip had developed under the road, bringing the total number of underslips to 15 in addition to the three overslips that crews are working to clear.
The increasing frequency and intensity of severe weather events as a result of climate change meant slips and closures were becoming more common across New Zealand's monitored road networks, Hori-Hoult explained.
Fortunately, the transport agency's contractors had successfully cut a temporary track through the largest slip covering the road at the southern end of the gorge.
The gap meant construction vehicles were able to pass through allowing crews to begin work on clearing slips further south.
"Under the direction of the specialist geotechnical engineer, crews are working to prevent any further damage to the current underslips, with bunds constructed to divert any further rainfall away from the slips," Hori-Hoult said.
She acknowledged the importance of the route through the Mangamuka Gorge for the Northland community by saying as soon as their damage assessments were complete they would provide more information to the public.
Waka Kotahi has reinstated temporary access for over-dimension vehicles via the SH10 Waitangi River Bridge to ensure the continued movement of vital goods.
Hori-Hoult said restrictions on the use of the bridge were put in place earlier this year, following the detection of deterioration during a routine inspection.
The condition of the bridge is being very closely monitored, with a structural engineer checking the bridge daily.
