State Highway 6 was extensively damaged in the storm. Photo: Supplied/NZTA
Part of the main highway between Nelson and Blenheim will close for seven weeks so emergency repairs can be carried out after the August storm.
State Highway 6 between Hira and Ronga Road near Rai Valley, will close from 1 November to 18 December.
Waka Kotahi top of the south system manager Andrew James said it was a substantial amount of time, but the route is vulnerable and could be seriously damaged by another storm so the repair work needed to be done as soon as possible.
"Now that we have completed the repairs on State Highway 63, we need to get back onto State Highway 6 to fix five substantially damaged sites where there have been underslips. Three of these will require us to significantly cut back the road before it can be built back up again."
The closure is likely to cause inconvenience for many, particularly those living in or around the Rai Valley.
"This is the best option on the table, and we appreciate their patience while this crucial transport link is repaired. We are making every effort to get the route restored before the busy Christmas period."
After the August storm, Waka Kotahi opened State Highway 6 quickly to help keep people moving, while more permanent fixes were completed on State Highway 63, James said.
Contractors will work as quickly as possible to get the five sites repaired, and ongoing work will be needed after the closure ends, James said.
Waka Kotahi hopes to have two traffic lanes re-established in time for the holiday season.
Further work will be needed next year, but it's not expected the road will have to close for this.
Complex structural projects like this faced risks from unexpected geotechnical factors and potential weather delays but all efforts would be made to meet deadlines, James said.
Other planned maintenance work will be done during the closure, including pavement renewal and additional drainage work to improve network resilience, such as improving culvert inlets and outlets, increasing the size of some culverts, and strengthening drainage channels.
Motorists wanting to travel between Blenheim and Nelson will have to use the detour on State Highway 63 through the Kawatiri Junction - 175 kilometre journey that takes around two and a half hours.
