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The hill is holding up, for now

Snow on the Remutaka Hill Road. PHOTOS/FILE

With a large earthquake, access to Wairarapa over the Remutaka Hill Rd could be cut off for months on end. GRACE PRIOR investigates the stability of the hill.

In the past month, the hill road closed twice unexpectedly – first due to bad weather causing a slip, and the other due to a fatal motorcycle crash. Motorists were left stuck on either side of the hill or queuing for hours.

Waka Kotahi [NZTA] regional transport systems manager Mark Owen said the road closed unexpectedly 5.5 times a year on average.

The Remutaka Hill Rd has a reputation for incidents; in 2012, police urged caution after a truck spilt hollandaise sauce on the road near the summit.

NZTA said in a 2016 business case that the crash history for the hill road indicated “significant safety risks for vulnerable road users, particularly motorcyclists”. The report explained that there were no viable alternative road routes in and out of Wairarapa.

The report also said the long-term resilience of the hill road was of regional concern – mainly if the hill were to be affected by an earthquake at about 7.5 on the magnitude scale or experienced an extreme storm event.

Wellington Region Emergency Management Office regional manager Jeremy Holmes said if the Remutaka Hill Rd were closed due to a large local or regional earthquake, Wairarapa could be cut off from Wellington for an extended time.

“This is a good reminder for communities to have a household plan and have seven days of food, water and other essential items, such as medicines, at home.”

He said flooding across the region on June 25 was a good reminder for communities to get prepared for emergencies, particularly where there was a chance they could be cut off from the rest of the region.

Holmes said contingency plans would depend on the type and size of the emergency event.

“There is a possibility that the railway tunnel will remain open which would allow commuter access and some freight supply between Wairarapa and the Hutt Valley.

“Aside from the railway tunnel, access between Wairarapa and the remainder of the Wellington region in a large emergency event may have to be via the Manawatu.”

Holmes said food and other essential deliveries for Wairarapa would continue to come from further up the North Island, including groceries from Palmerston North.

“We have recently seen the impacts from common hazards like flooding and slips on our roading networks. It is important for communities that rely on these networks day-to-day, to be prepared and have emergency plans.”

Owen said the geology and topography of the Remutaka Hill Rd was different and more resilient when compared with the Manawatu Gorge, which had been estimated to cost $620 million to fix.

He said the gorge had experienced large scale slips, whereas the hill road usually only experienced smaller slips, often only blocking one lane.

Owen said the recovery response for the hill from NZTA would differ in the event of an earthquake when compared with a storm, because it was likely that many other roads across the region would also be closed.

“We would focus on getting transport up and running, as it’s vital for recovery in general. The most likely route for Wairarapa to be opened up first would be via Mt Bruce.”

When it came to the resilience of the hill in general, Owen said it was generally good, and the most significant risk was driver safety.

He said improvements had been undertaken over the past few years and were ongoing. The main focus of many improvements was to widen corners and prevent slips.

There had been an ongoing discussion about a tunnel through the hill. Previous mayoral candidate and architect Graham Farr had been pushing the community to get behind the development of a tunnel.

He was puzzled as to how we hadn’t built a road tunnel through to Wairarapa in the past 50 years.

“Sixty-five years ago, we could build a 9km tunnel for rail so why can’t we build one a third of the length now?” he said.

Farr said the tunnel would be two twin 12-metre dual-lane tunnels using the 1967 Ministry of Works route – and it would shorten the commute over the hill to just six minutes.

He said the tunnel would cost $800 millon to build and would be relatively simple to build with new technology.

“The tunnel would also be more resilient to earthquakes because it would be put out of the way of the fault.”

Farr said much of the problem when it came to earthquake damage was aftershocks – something that delayed the reopening of Christchurch’s Sumner Rd. Traffic was mostly diverted through the Lyttelton Tunnel.

Owen said it was very unlikely that a tunnel would be built through the hill in the short to medium term.

“It’s very expensive to build and operate, you have to build two not just one.”

He said the concept of a tunnel through the hill sounded easy to many, but it would be an incredibly large-scale project.

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