Urgent work after more movement at slip site
Urgent work is planned for the State Highway 4 (Parapara) Te Oreore slip site between Whanganui and Raetihi after heavy rain caused ground movement in the area.
In October 2019, a major slip on SH4 about 18km south of Raetihi destroyed a large section of the road, completely closing the highway until a temporary road was constructed through the middle of the slip area. Dewatering works began in 2020 to stabilise the landslip and undertake critical testing.
On Wednesday, December 21, Horizons Regional Council granted Waka Kotahi NZ Transport Agency resource consent to build three retaining walls north of the main slip area and the drilling and construction of two new dewatering wells.
Waka Kotahi project sponsor Wayne Oldfield said the need for the works became evident after the heavy rain this winter that caused ground movement at the slip site.
“There was movement in a number of locations at the site and the temporary road was reduced to one lane to prevent heavy loading on the outside edge of the lane,” Oldfield said.
“We now need to undertake works to prevent further movement and safeguard the area so we can keep moving forward with the slip replacement project.”
As well as providing a link between Whanganui and the Central North Island, the Parapara is also the backup link if SH1 is closed between Bulls and Turangi.
Waka Kotahi said the work required to reinstate the route was complex and significant and the
agency was working with local iwi to ensure the plans for the new permanent road supported the objectives of Te Waiū -o-te-ika — the legal framework for the Whangaehu River Catchment as part of the Ngā ti Rangi Treaty Settlement.
The wider area is of cultural significance and is located within an area of interest to local iwi. The Mangawhero River is just below the proposed work site. It is identified as a site for mahinga kai (food gathering) and is a tributary to the Whangaehu River.
Tuhiariki Marae spokesman
Troy Brown said they supported the enabling works “as the Parapara road is an essential route for the health and wellbeing of our people”.
“However, while we support this work, it is significant that the dewatered wai stays in its most pure form before entering the awa.”
Ngā ti Rangi Pou Ā rahi Helen Leahy said the protection of the taiao (natural environment) was paramount to Ngā ti Rangi.
“This is underpinned by our cultural principles and high environmental values. However, the learnings from whakapapa serve to remind us that it is also important to keep the people connected; this includes our communities that rely on the Parapara Rd. Therefore, our engagement with this process is future-focused.”
Ā tihau-whanganui Incorporation culture and legacy manager Whetu Moataane said they had been working closely with NZTA, Ngā ti Rangi and Ngā i Tuhiariki for the past two years on the cultural impact assessment “to ensure the voice and aspirations of hapū and iwi are heard and paramount”.
“Even though we are the landowners, it is very important to Ā tihau that hapū and iwi are proactive and collaboratively lead the upcoming Te Oreore works,” Moataane said.
The works, which will be done within the existing road reserve, are expected to start in February.
Resource consent was also granted recently for continued dewatering activities from the five existing groundwater bores on-site.
It’s not the only work planned for the Parapara, with a range of projects due to start in January.
On Tuesday, January 10, a full rebuild and sealing of nearly 300m of SH4 south of Kakatahi, near Macintoshs Rd, will get under way. Stop/go traffic management will be in place between 6am and 6pm Monday to Friday for three weeks and there will be delays of up to 10 minutes during this time.
From January 16, weatherdependent, resealing will start at multiple sites along the road and is expected to take four days.
Waka Kotahi NZ Transport Agency maintenance and operations manager Rob Service said work would resume in January to progress slip repairs on the road.
“We’ll begin ground investigations on January 10 at the site north of Hawken Rd where the road is down to one lane due to a recent washout. This testing will help us to complete a design for a permanent solution there.
“At the end of January, construction of a retaining wall will begin at the site of the underslip near Burrell Rd. Local company Loaders Whanganui will carry out this work and it is expected to be complete by the end of May.”