Chopper aids slip site works

More than a month after a slip sent tonnes of mud and rock crashing down on a section of State Highway 3 in north Taranaki, a helicopter dumped thousands of litres of water on the site to clear loose debris.

Yesterday’s operation at Urutı¯ was organised by Waka Kotahi NZ Transport Agency as part of the clean-up following the December 9 collapse, which cut off the region’s main route north and disrupted the travel plans of hundreds of motorists.

A car travelling along the road at the time was hit by the deluge of debris, but the two occupants escaped uninjured.

One lane of the highway was reopened the following day, but motorists have faced delays travelling through the area since the slip.

Pilot David Beck, of Beck Helicopters, said about 32 bucket loads, each containing 1500 litres of water, which could be emptied in 1.2 seconds, were dumped on the cliff face.

‘‘You are trying to create the effect of a lot of rain all at once and while the road is closed,’’ Beck said. ‘‘The volume of water going past will blow any loose stuff off the cliff face.’’

Beck, who has more than 25 years’ experience, said the water would also get in behind any cracks and soak into the ground, exposing any faults in the rock face.

‘‘Basically you are trying to speed up nature.’’

The heavy ‘whump’ sound of the Huey Iroquois helicopter echoed around the valley as it hovered above the site before dropping its watery load.

Every drenching of the cliff face brought down a cascade of mud, rocks and debris on to a barriered-off section of the highway.

Waka Kotahi NZTA Taranaki system manager, Ross I’Anson, said the work had been a success, bringing down 25 cubic metres of loose material.

‘‘The operation met expectations of geotechnical engineers,’’ I’Anson said. ‘‘The work today has removed all the loose debris on and at the top of the slip face.’’

However, I’Anson couldn’t guarantee there would be no further problems.

‘‘Due to the nature of the terrain and geology, this site may still experience issues in future weather events.’’

He said it was hoped both lanes of the highway would be reopened today.

MAIN PHOTO: ANDY JACKSON/STUFF Pilot David Beck, of Beck Helicopters, dumps water on a Urutı¯ cliff face yesterday to remove loose debris following the large slip at the site just before Christmas. Inset: A car was caught in the slip on December 9 but the two occupants managed to escape uninjured.