New Zealand Transport Agency (NZTA) acting regional manager Murray Clarke said large drilling machinery, accompanied by a concrete mixing plant and diggers, would carry out column stabilisation work on several slips on the motorway before Christmas.
It was the first time the machinery had been used in the South Island.
Drilling machinery, owned by Auckland-based contractor Highway Stabilisers, would bore into slip areas to a maximum depth of 19m to mix cement and soil and bind earth together below the slip plain.
The number of concrete "rows" drilled depended on the amount and weight of slip material, Mr Clarke said.
The machinery would also be used at sites on State Highway 1 at Church Slip just north of Church Rd, 500m north of there, and 400m north near Scott's Slip.
"This is new technology and we are pretty confident it will reduce risk of slips in future.
We are hoping the project will be completed by Christmas but it may be extended.
Work will be suspended over the busy traffic periods," he said.
Although tree planting and installation of gabion walls had slowed movement, subsidence at several sites combined with high winter rainfall, meant NZTA contractors had to resurface and repair roads every 12 to 24 months in some areas.
The NZTA was investigating using the machine on Pinehill Rd, Dunedin, to slow "gentle subsidence on SH1 opposite Banks St".
"It is a very large machine and the risk and disruption to traffic would have to be comprehensively assessed before it was used there.
But, given the importance of the road, we are mindful of the need to find solutions and will look at all possibilities."
