Progress of work on SH4 slip detailed at Whanganui District Council meeting

L to R: NZTA representatives Wayne Oldfield, Mark Owen, Hannah Thompson and Emma Speight at the council meeting. Photo / Bevan Conley

Representatives from the NZ Transport Agency have fronted councillors with the latest on the State Highway 4 slip.

Installing a temporary road is the priority for the NZ Transport Agency (NZTA), and is included in phase two of the response to the slip.

State Highway 4 between Raetihi and Whanganui has been closed since early October when a massive slip took out hundreds of metres of the road.

Permanent reinstatement is part of phase three of the process, and is being planned while consenting work is also under way. A business case for long term resilience is being put together.

A group of six NZTA representatives were in Whanganui on Tuesday to attend a council meeting.

NZTA manger of systems management Mark Owen said weather permitting, an open date for the temporary road is just weeks away.

"We had some fairly wet weather on Sunday and things stood up reasonably well so we're feeling reasonably confident, but we've got more wet weather coming this weekend so we'll see how progress goes."

L to R: NZTA's Dan Tate, Wayne Oldfield, Mark Owen, Hannah Thompson, Robyn Fisher and Emma Speight. Photo / Bevan Conley

One of the phases NZTA is undergoing involves the management of other slips or damage on the highway.

"We're looking at this as a parameter of work along SH4 this summer," Owen said.

"While we will temporarily reconnect the site at Matahiwi, there is going to be a lot of other work along this corridor with about six other sites."

Owen said once the temporary road is open, it would probably take another 30 minutes to travel between Whanganui and Raetihi than it usually would, due to the work.

"It's sort of short term pain for long term gain."

He said he expected some level of "normality" to return to the sites within 12 to 18 months, but that work to repair at least one of the sites would go into 2021.

Mayor Hamish McDouall asked the NZTA representatives how the level of risk associated with the temporary road will be assessed and what the risk is to the public.

The temporary road is expected to open in the next few weeks if conditions stay fine. Photo / Bevan Conley

Owen said there's always some risk like any part of New Zealand's roading network, but said geotechnical experts are assessing the ground and advising the agency.

A trigger action response plan (TARP) will be in place and notify NZTA if there's any risk deemed too significant for the temporary road to stay open.

NZTA systems management senior manager Wayne Oldfield said two or three routes are being considered for a permanent route, and hoped to have "the most cost effective, resilient route" chosen soon.

A formal consenting process would follow once the route is selected, Oldfield said.

With the recommended detour being Whanganui River Road, Councillor Rob Vinsen asked if NZTA could do anything about changing directions supplied by Google Maps and GPS companies which advise motorists to use Fields Track.

Owen said the team had contacted Google, but told councillors it's hard to influence Google when Fields Track is a legal road that anyone can drive.

Contractors working to clear way for the temporary road around the slip face. Photo / Bevan Conley

Councillor Graeme Young asked whether the importance NZTA is placing on SH4 would continue in the future.

"I think there has been, in the last six or seven years, a noticeable lack of improvement," Young said.

"[Does] sitting in Wellington make it a little more difficult to appreciate the importance of SH4 to the people in Whanganui?"

Mark Owen said the agency is "absolutely focused" on the work but probably have dropped the ball in the past.

"I think we probably haven't responded as well as we could've along this corridor, but our general manager has inspected it and you've seen the effort we're putting into it.

"Subject to funding and priorities, we'll continue to keep focus on this highway knowing it's a key link through the central North Island."

Whanganui Rural Community Board chairman Grant Skilton, who has a seat at the council table, said some of the rural residents in the area feel like they're not being communicated with properly and asked if NZTA would engage with them.

"We were trying to use all of our channels at the moment and typically we'd work via a council," Owen responded.

"We just don't have the resource to go and deal with every little community everywhere and we rely on the council to be the voice of the community.

"But if you think there's a reason why we need to front up and do that, then absolutely.

"We're trying to be more customer and stakeholder focused and we'll be guided by council and what they want us to do."

McDouall suggested a meeting between NZTA and affected SH4 residents should take place early next year.

The NZTA representatives also met with councillors at Ruapehu District Council on Tuesday.