However, the Dunedin City Council is first seeking detailed design plans for the work from the New Zealand Transport Agency, fearing the rush to secure the highway could leave an ugly scar through the bush-clad Town Belt.
A council report to this week's community development committee confirmed the agency was planning urgent work to halt the landslip, which was moving at an accelerating rate.
Monitoring over the past three years had detected a 97mm drop across a 100m-wide section of the steep bank near Bank St, leading from the highway down to the Water of Leith, beside Woodhaugh Gardens.
However, the same section of land had dropped a further 6mm in the past month, indicating the rate of descent was speeding up, the report by council reserves policy and planning officer Dolina Lee said.
That rate equated to 72mm a year, or 216mm in three years.
The report warned of "significant" damage to the state highway, and the section of Town Belt below, if the land was not secured.
"Urgent stabilisation work is required to prevent further subsidence of the section of road".
If further significant movement of this slip occurs, damage to both State Highway 1 and the section of Town Belt below the road is likely, involving potentially significant and long-term disruptions to traffic into and out of Dunedin."
NZTA Otago and Southland operations manager Murray Clarke said the slip was unlikely to lead to a sudden road failure, but could cause the road to gradually crack.
If that happened, it was likely the road would have to be reduced to one lane, with some traffic diversions in place while repairs were carried out.
"It's not panic stations by any means, but we definitely don't want to get anywhere near that."
However, council community and recreation services manager Mick Reece said he was "cautiously" scrutinising the agency's plans to repair the road.
The agency has applied for an easement over part of the Town Belt to allow up to 40 horizontal underground drains to be drilled to draw water from under the road.
The council's report said the ground in the area was "saturated" and needed to be drained before a long-term engineering solution could be carried out.
The drains - each 25m long and 70mm in diameter - would be spaced at 2m intervals along the slip zone and feed into an above-ground pipe or flume emptying into the Water of Leith.
As part of the work, a 4m by 100m "zone of disturbance" would be needed within the affected area of the Town Belt, allowing vegetation to be removed to provide working space for a drilling rig and engineers, the report said.
The work was expected to be carried out early next year, taking six to eight weeks and costing about $250,000, NZTA Otago and Southland state highway manager Niclas Johansson said.
The report will be discussed by councillors tomorrow.
