Work will begin in the New Year on the long-term solution to re-open State Highway 6 at Diana Falls (Haast Pass) to two lanes and a 24/7 operation.
"Early in the New Year we will begin work drilling and blasting the large 200 and 300-tonne rocks sitting at the head scarp of the slip into smaller two to three-tonne pieces to be removed from the slip face," says the NZ Transport Agency's Senior Network Manager Mark Pinner.
"We will aim to do this with minimal impact on motorists travelling through the area."
Following this work, Mr Pinner says attenuator fences will be installed. "These fences will be anchored either side of the slip face, draping across the slip and standing about 1.5 metres high to catch any rocks or material that may fall from above.
"These will be capable of catching and holding up to 2500 tonnes (about 1000 cubic metres) of rock and material, and once installed, a regular programme of clearing and checking the fences will begin."
He says before Christmas it is planned to create a mouth at the top of the channel on the slip's 30-metre vertical face to catch and then funnel any material off the slip face.
"After we have drilled the rocks at the top of the face and installed the attenuators, we plan by late February/early March to be in a position to drape mesh netting across the vertical face.
"It will be positioned two metres above the top of the slip's sheer rock face and it will follow the rock face down to act as a chute for any material that might move off the slip. The netting will also help limit rocks moving down the mountainside from bouncing onto the road."
Once all this work is completed, Mr Pinner says it is hoped to be able to reinstate two-lane access through the area from about April/May and to have the road open 24/7. Night-time closures, from 7pm to 8am, will remain until this time.