In a media statement, senior network manager Central Otago Robert Choveaux said a hydraulic press similar to the "jaws of life" used by firefighters was being used to pry open rock before airbags were slipped in.
The airbags were then inflated to dislodge the rocks.
The alternative method of blasting would have meant the busy State Highway 6 running under the bluff would have to have been closed for up to an hour at a time for safety reasons.
The new technique, which was used along the Kaikoura coast after the 2016 earthquake, meant the road was only closed for 10-minute periods to limit traffic disruption.
The work, which is part of the agency’s routine autumn maintenance programme along the highway, is timed to allow crews to address known geotechnical hazards before freeze-thaw conditions set in that can affect the slope and possibly create instabilities.
The bluff, which is about 800m long and up to 160m high, had major slips in 1975 and 2000.
