Waka Kotahi NZ Transport Agency maintenance contract manager Jennifer McLean said a team would be installing three drainage trenches under an area of highway between Morrisons and Kyeburn which had been prone to slips for many decades.
"In order to install the drains, the highway has to be excavated and the safety barrier removed temporarily.
"These drains will discharge into a trench in the nearby gully to stop the groundwater undermining the highway at this spot."
The work was expected to close the road from August 29 until September 26, but the dates were subject to weather and could change, she said.
Residents, landowners and businesses in the closure site would retain access to their properties from either end of the closure, up to the work site.
A detour would be in place for light vehicles (cars and vans) from SH85 at Waynes, near Dunback, via Macraes Rd, Hyde-Macraes Rd and SH87 to Kyeburn, and the reverse.
This detour was expected to add about 30 minutes to the journey.
It would not be suitable for high-productivity motor vehicles (HPMVs) — trucks weighing more than 48 tonnes — because of weight restrictions on the Hyde-Macraes Rd Bridge.
HPMVs would need to detour via State Highway 1 and State Highway 87 through Dunedin and Mosgiel.
Ranfurly Transport owner Richard Duffy said it would have an impact on his business, but Waka Kotahi had consulted with him and other transport businesses in the region.
"There’s really no good time to do it. It’s got to be done.
"You’ve just got to go along with it."
