Authorities hope to reopen State Highway 1 between Kaikōura and Christchurch before Christmas.
The main southern route into Kaikōura has been closed since last month's major earthquake.
New Zealand Transport Agency regional performance manager Peter Connors said there were 29 slips along the stretch of road.
They were fixing number 14, just north of Oaro.
Mr Connors said work was under way to make the route as safe as possible.
"It's just not clearing the debris away, it's about making these slopes stable."
The work depended on weather and aftershocks.
"We want to make sure, that when we do finally get this open, we've got some confidence about the slope stability."
In some places it would be single-lane, he said.
Mr Connors said it was still unclear when the highway north of Kaikōura would reopen.