Stabilising the cliff face on State Highway 30 at Ruato Bay is not going to be an easy fix but it is hoped work will be completed by the middle of this year, transport authorities say.
Local iwi are being consulted throughout the process.
A large slip last July brought down a significant amount of large rock material on to the state highway between Rotorua and Whakatane. The New Zealand Transport Agency and the Rotorua District Council have been working to stabilise the cliff face from any further rock falls and traffic lights have been in place to control the movement of vehicles at the site.
NZTA Bay of Plenty state highways manager Brett Gliddon said its project manager had been consulting locals who had been very supportive.
"In terms of managing material from the cliff face - rocks - this has been stockpiled in agreement with local iwi, it will not be removed until the preferred option is identified and we have consulted further with them.
"This cliff face is of cultural significance."
Asked if there had been any talk of compensation for the rocks, Mr Gliddon said the organisation had not been approached by locals about that and it had not been raised during discussions.
However, the authorities have agreed to continue to consult with local iwi in managing the material from this area.
Remains of a World War II tank trap were also found at the site.
There were a number of them built during that war to prevent an invasion.
"Any solution to stabilise the cliff face will take account of this tank trap."
Mr Gliddon said the rock falls were continuing on a regular basis as the face settles and the pressures on the rock from trees and adjacent rock columns change.
"These boulders are fairly large and ensuring that workers and drivers using the road are safe is our main priority. Since the slip we have secured the area for safety purposes from ongoing rock falls by closing one lane - the one closest to the cliff face - and erecting barriers around this area.
"We are advised that the rock face is somewhat unique and makes stabilising it a more challenging job."
Over a week ago, the agency successfully undertook some geotechnical investigations at the cliff face, requiring the road to be closed at night over two nights to allow a drilling rig to come in and drill into the face so that specimen material deep into the core of the cliff could be extracted.
The investigation would refine the options for the permanent solution to stabilise the cliff.
"Some of the options considered include moving the road over away from the face to create a safety space [or zone], cutting more of the cliff face back, meshing and bolting the face and variations of all of these."
Mr Gliddon said the next process would be to design the preferred solution once it had been established and consult key stakeholders on this option before the necessary resource consents were obtained and the work is tendered to a contractor.
It was hoped the work would be completed by the middle of this year.
