Geologists assessing the slip face at the Waioeka Gorge say the site is still too unstable for workers to safely begin the task of removing slip material.
NZTA's acting Bay of Plenty state highway manager Andrew Scott said the geological assessment means it could be a week before diggers or machinery are able to safely begin.
While the NZTA has used helicopters with monsoon buckets to move some loose material on the rockface, Mr Scott says there remains a large area containing an estimated 10,000 cubic metres that has been difficult to get to.
Mr Scott says a larger monsoon bucket will be brought in tomorrow to help dislodge the large block of unstable material quickly.
The NZTA are also bringing in specialists to assess whether explosives can be used to blast this large unstable block if the larger monsoon bucket option does not wash the material down slope quickly.
"We're looking at all the options available. This material is large and overhangs the area below, which means our diggers are unable to get in there and safely work at the toe of the rockface. If we can't get the material dislodged with monsoon buckets we'll be bringing in experts to blast this area with explosives," says Mr Scott.
Mr Scott said contractors estimate that it will take at least two weeks to remove the 100,000 cubic meters of slip material which came down on Saturday 3 March, but the worksite must be made safe from any further slips before that clearance can get underway.
"We are eager to get in there and get stuck in to the job, but the safety of the men and women who will be doing this work is a top priority and we need to be confident that the site is safe before we send them in."
At this stage the Gorge could remain closed for at least a month possibly longer, says Mr Scott.
"Our assessment based on our discussions with our geotechnical advisors and contractors so far is that the Gorge will take four weeks or longer to re-open".
Mr Scott says that once slip material has been removed by workers, the NZTA and their geotechnical advisors will need to monitor the rockface to ensure no further slips will occur before it is re-opened to motorists.
"The safety of motorists is our top priority. We appreciate the closure is having a big impact on travellers and businesses and we are focussed on getting the road re-opened as quickly and as safely as possible.
Road blocks and VMS signage have been erected to close off the Gorge and also to remind travellers driving from Rotorua to use alternative routes such as State Highway 35 until the Gorge is safe to re-open, says Mr Scott.
For up to date information on the Waioeka Gorge visit www.nzta.govt.nz(external link) or call (0800 44 44).