Workers need to install new culverts and repair others. Photo: RNZ / Cole Eastham-Farrelly
State Highway 4 between Whanganui and Raetihi will close for five days later this month as crews carry out drainage works at Te Oreore.
In June 2015, major flooding in and around Whanganui caused substantial damage to parts of SH4 Parapara Road.
Since then NZ Transport Agency Waka Kotahi has completed work on several sites along SH4, including at Te Oreore which was the site of a major slip in 2019.
This month's drainage work will involve a number of drainage culverts, which currently run below the road, being repaired and replaced.
The road will be closed from Monday 18 March to Friday 22 March between 9am and 3pm daily.
The closure points will be at the intersection with Alexandra Road at Raetihi and Whanganui River Road in Whanganui.
A massive slip on washed out the road to Raetihi in June 2015. Photo: SUPPLIED / Ruapehu District Council
Project manager Gareth Howie said installing new culverts and repairing others was essential to the success of the project.
"To keep the road performing well and reduce the likelihood of future potholes we need to make sure water can easily drain away from the hillside and the road and into the Mangawhero River. It's also vital to have good drainage in the event of future flooding.
"We looked at options other than daytime closures during this period, but the road is too narrow at this point to safely carry out the work under stop/go traffic management. In this case, a short term closure is more efficient and less disruptive for road users."
Howie said during the road closure residents and emergency vehicles would continue to have access.
"We appreciate these closures aren't ideal and people travelling this section of SH4 have seen a lot of work in recent years, but we've worked closely with nearby schools, iwi and hapū around the closures to ensure disruption is minimal, by making the daily closure period as short as possible.
"Without this closure, the installation of the culverts would take a lot longer, delaying the overall project."
Smaller works would be carried out on the closed section of road at the same time, including felling unsafe trees.
Howie said display boards would be in place in Raetihi and Whanganui informing drivers of the daytime closure.
"Please plan your journey around these closure times and keep an eye on our Journey Planner for up to date information."
The work was weather dependent and might be postponed until the following week.
Te Oreore slip replacement
Howie said work crews were making good progress at the site and were hopeful of opening the road at this site to two lanes in April.
As part of the project, new retaining walls, road base and drainage works are being built to provide for improved performance of the temporary road.
The three new culverts would be laid across the road, and two existing culverts would be relined, to prevent surface water from eroding the rebuilt road or surroundings.
The project is a part of the same wider work to restore full connection on SH4 between Whanganui and Raetihi, following major flooding, causing substantial damage to parts of the state highway in June 2015.
The flooding left silt and debris, slips and dropouts.
This was followed by a major slip in October 2019, which destroyed a large section of road south of Raetihi and forced its closure.