The NZ Transport Agency has announced the next phase of its plan of attack to secure the unstable hillside that has closed State Highway 3 through the Manawatu Gorge for more than 80 days.
NZTA Palmerston North State Highways Manager David McGonigal says that some of the unstable material further up the hillside has remained intact despite rain and dowsing with monsoon buckets, and the NZTA had developed a new approach to bring it down.
“The massive slip of 17 October was a game changer. It nearly tripled the size of the exposed hillside and we have to tackle the slip on these new terms.
“We can’t reopen the gorge safely until all the unstable material at the top of the slip has been dealt with, and we’ve had to develop more innovative techniques to expedite this.”
“Waiting for the unstable section to come down on its own was clearly not an option—we’re getting up there to deal with it directly.”
Mr McGonigal says that a track is being created behind the slope through farmland and bush to enable heavy machinery to be taken to the top of the slope. Machinery would then clear the unstable material from the top down and ‘bench’ the upper hillside by creating terraces, while being anchored securely to the top.
Mr McGonigal says that heavy machinery will be operating at the top of the slope within two weeks, once the access track is complete.
“We recognise that the gorge closure is frustrating. We know that every day this vital link is closed has significant impacts on the region, and we are doing everything possible to get the road open."
Mr McGonigal says the NZTA’s approach is the most effective solution to getting the hill stabilised as quickly as possible.
“When material comes down, it tends to relax the hillside and this can result in further slips so we’ll be keeping a close eye on the surrounding hillside and how it behaves in coming weeks.”
Mr McGonigal said that given the nature of the terrain and the changeable conditions, the NZTA may need to adjust its approach as things develop.
Mr McGonigal says the operation is likely to take around two months, but this is dependent on how the situation unfolds and the NZTA will continue to look for opportunities to accelerate progress wherever possible.
Further information about the plan will be communicated next week once plans are finalised.
In regards to the detour routes, NZTA road crews this morning cleaned up a minor slip on the Pahiatua Track. The slip occurred in the early morning, and effects on traffic flow were minimal, The NZTA is also continuing construction on three slow vehicle bays on the Saddle Road, and is investigating a fourth.