West Coast challenge – 50,000 cubic metres of it

It was a case of all hands to the pump – including the local fire brigades’ – as a massive slip closed SH6 north of Whataroa. Hugh de Lacy tells the story.

When 200,000 cubic metres of primeval rain-forest decided to decamp from the hills above the Whataroa River and relocate across the only road giving access to the tourist hotspots of the Franz Josef and Fox Glaciers, first-responders were the two local fire brigades.

A massive dumping of rain, such as only the West Coast can produce, had trapped two cars and five passengers in the middle of the slip, blocking 400 metres of the highway about five kilometres north of Whataroa.

The motorists had been heading south towards Whataroa and Franz Josef about 11pm on a late February Thursday when suddenly their way was blocked by a mountain of glutinous debris heavily studded with huge and ancient trees freshly swept from the adjacent mountainside.

Both cars managed to turn around, but before they could retrace their way a washed-out culvert blocked off their retreat.

A Whataroa-based Westroads employee who was out patrolling the highway for just such a development, as part of the company’s contractual arrangement with the NZ Transport Agency, came on the scene soon after one of the trapped motorists called the Police, and the local contracting organisation swung into action.

Whataroa Volunteer Fire Brigade chief Ian Philps was one of the first jolted out of his sleep by a text message that a monster slip had come down across the main road, and that there were motorists trapped.

The text message found Philps and his fire station in complete darkness because the slip had taken out the power lines, leaving Whataroa township and all points south without electricity until around midday the following day.

A similar text message had been received by the Harihari Volunteer Fire Brigade, about 25 kilometres to the north and unaffected by the power-cut, and appliances from both brigades and directions converged on the slip.

By the time Philps’ brigade got under way almost the entire five kilometres from Whataroa to the slip was under water, and the tender couldn’t travel any faster than 30kph.

When they got there the water was so deep across the road, and the massive slip was still moving so quickly that it was too dangerous to mess with.

Philps tells Contractor the firemen had to sit in the tender twiddling their thumbs for half an hour before the water level around the slip fell enough for them to safely go looking for the motorists, for whose safety they now held grave fears.

In fact neither the motorists nor their vehicles were in danger: the slip had split like the Red Sea around them, and though they could go neither forwards nor backwards, they were at least alive and safe where they were.

The Whataroa firemen were aware of the presence of their Harhari colleagues on the other side of the slip, but could not make contact across it, so after blocking the approaches to the slip with signage they took the bedraggled motorists back to Whataroa.

The weather bomb that caused the slip was a massive downfall of 180mm that hit Whataroa and all points immediately to the north.

Even for an area of the country that gets five metres of rain a year, the drenching that night was a monumental one, and followed a severe weather warning issued at 8pm that evening.

The localisation of the downpour was such that Harihari received a mere 30mm overnight, while to the south Franz Josef recorded 60mm between 8pm and 4am the following morning, a third of it between 2am and 4am.

Patrolling SH6 during severe weather is a standard precaution for NZTA’s highway maintenance on the West Coast – and for good reason: it was only five years ago that a Canadian couple were killed when their campervan was swept off Haast Pass by a rain-induced landslide, and last year 117 tourists were stranded during Cyclone Fehi by fallen trees and a slip on SH6 that forced many of them to spend the night in their cars.

Moira Whinham, NZTA’s West Coast maintenance contract manager, got the call about midnight, and by 1.30am the first of no fewer than seven local contractors had reached the site and were ready to go to work, though for safety’s sake work didn’t actually start until daylight.

Some remained there throughout the night on both sides of the slip.

The NZTA call-out was led by Fulton Hogan, and otherwise included Westroads, Henry Adams Contracting, Arnold Contracting, JJ Nolan, McKenzie Contracting and MG and EM Sullivan.

The problem with slips on SH6, and the urgency of the need to clear them, is that between Kumara Junction in the north and Wanaka 450 kilometres to the south there’s no possible detour, so while the road’s closed South Westland is effectively cut off.

It’s another 425 kilometres from Wanaka to Christchurch, and 290 kilometres from there to Kumara Junction, and with the Franz Josef and Fox Glaciers hosting 4000 visitors a day at that time of the year, the economic impact on South Westland was all the greater.

The 68th Whataroa Agricultural and Pastoral Show scheduled for the Saturday had to be cancelled as the contractors set to work.

“The strategy was to clear a single lane through the slip to get traffic moving again,” Whinham tells Contractor.

“It was a really horrible mix of large trees, vegetation, gravel, mud and slops, and a whole lot of water.”

Diggers and excavators ranging in size from 13t to 26t attacked the slip, some using grapples to wrestle the huge trees out of the way.

Even so it was not until 6pm on the Saturday, and after shifting 50,000 cubic metres of spoil, that the contractors were able to clear enough of the road to allow a single lane, controlled by traffic lights, to operate.

For two weeks after the event, the single lane was open throughout the night, but during the day was open for just 10 minutes per hour, on the hour.

Perhaps, surprisingly, there proved to be relatively little damage to the road surface itself: the carriageway and most of the seal were still in place, with the slip having gone over the top of the road rather than sweeping the lot away.

With the Whataroa slip finally cleared away, the local contractors are left to prepare for the next of the West Coast’s wild weather convulsions.

And they didn’t have to wait long. It was just a month later the Waiho bridge, just half an hour south of Whataroa, was washed away  – Ed.


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