When the lower South Island was battered by a destructive three-day storm last February, the iconic Routeburn and Milford Tracks bore the brunt. 

More than a metre of rain fell in the Fiordland National Park and Mount Aspiring National Parks, three times the monthly average, causing dozens of landslides on the tracks, washing out bridges and effectively destroying the Howden Hut.

But, implausibly, both tracks reopened from end-to-end last month, in time for the start of the tramping season.

The herculean task to repair and revitalise them, bringing some much-needed relief to the communities that earn a crust from them, was completed by an expert team of national and local Department of Conservation staff, hardy contractors and chopper firms.

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They were led by Tom Hopkins, DOC's strategic projects manager, who, along with his team, had in March completed a five-year project to build NZ's newest Great Walk, the Paparoa Track.

They faced a huge logistical challenge when they sat down after the storm to work out how to get the tracks reopen - working through winter and a cold spring on inaccessible sites, where practically all materials had to be chopped in and out.

"The Paparoa Track was relatively straightforward in that respect," Hopkins says, "we just had to get from A to B.

"But with this project, there was lots of damage all over the place, lots of bits and pieces.

"You've got to sort through it, find out what needs to be done at each site, prioritise the work, put a cost to it, work out how long it will take, then press the go button."

Hopkins says there was a similar amount of work needed on both tracks.

On the Routeburn, the damage was spread across the length of the 32km Great Walk, which winds through from Routeburn Shelter, on the Glenorchy-side, to the The Divide, on the Te Anau side.

The new Twin Bridge on the Routeburn. PHOTO: Abseil Access

Landslides

"On the western side of the Routeburn, we dealt with 12 separate sites," Hopkins says.

"They ranged from just a few metres through to 100-odd metres, in steep country. You're reinstating the track across the slips and trying to mitigate any rockfall issues that might have dropped out of that.

"We've had to put in three steel truss bridges between 10 and 14 metre spans on that western side of the Routeburn to bridge gaps that were left by landslides.

"In most of these instances the track has been completely destroyed.

"On the eastern side, there was a 130-metre realignment between Routeburn Flats suspension bridge and Twins suspension bridge."

On the Milford, by contrast, there were eight major slips and several smaller ones.

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Bridges

"The most significant work on the Routeburn were the two suspension bridges on the Routeburn Flats.

"The Twin Suspension Bridge was completely destroyed, so that needed to be replaced, and there was damage to the other bridge, lots of little bits of damage, including erosion upstream, so there's been some Gabion baskets put in there for flood protection."

Replacing the 27-metre Twin Suspension Bridge was one of the most technical projects on the Routeburn, while on the Milford the major job was the replacement of the 52m Giants Gate Suspension Bridge.

"The vast majority of our structures are designed and inspected by our own structural engineers. We've got a team of five around the country including one based in Invercargill.

"So, one of the first things that had to happen was inventory the damage and prioritise what we were going to address first and then get the engineer on to designing replacement structures.

"They've got that institutional knowledge, the details they use from other structures, and they just need to take into account local conditions, the length, the height of the flood clearance, ground conditions, and then stitch it all together."

Access to the Lake Sylvan Suspension Bridge was also cut off, so a new set of stairs had to be put in, while erosion damaged to the Sugar Loaf Bridge abutment was also fixed, along with several smaller bridges.

Lake Howden Hut, on the Routeburn, was irreparably damaged by a mudslide. PHOTO: DOC 

Howden Hut

Perhaps the most dramatic damage caused by the storm was to Lake Howden Hut, about 3.4km from the Divide.

It was hit by a mudslide in the middle of the night, while 30 people were inside. Some sustained minor cuts and bruises, but there were no serious injuries or fatalities caused by the storms. The trampers, along with scores of others on various tracks, 195 in total, were rescued by helicopter.

The hut, though, could not be saved and needed to be removed.

"The contract was awarded to Glacier Southern Lakes Helicopters and they had some builders in as sub-contractors. They smacked that out very quickly," Hopkins says.

"They were only on site for a week to 10 days. There was a bunch of stuff that needed retrieving, stuff that needed breaking down and flying out.

"Contractor West Reef was used to realign the track that comes down from Key Summit, across the hut, down towards the Greenstone and then back around the lake shore to a new steel truss bridge across the outlet creek."

DOC is, however, rebuilding the 40-bed Mintaro Hut on the Milford Track, at a cost of $3 million.

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The team

West Reef Services Ltd, the contractor that did all the repair work on the western side of the Routeburn, was one of three that had worked with the DOC team on the Paparoa Track.

The others were Wellington-based Abseil Access and Nelson local authority trading enterprise Nealmac Ltd. Abseil Access used eight staff on the projects, while West Reef used five and Nealmac four.

"They're really sharp, understand the work, are good at working in remote locations, establishing camps, working with helicopters, small plant, all that sort of thing," Hopkins says

They've completed various tasks, including removal of bits of fallen bridge and the removal of a 26m-long boardwalk from the Milford, while Nealmac completed much of the work on the Milford slips.

"Two or three of those were very messy, particularly between Boat Shed and Sandfly Point on the Milford Sound end.

"I wouldn't have wanted to be in there [during the storm], some of the stuff that happened was terrifying. Likewise, on the western side of the Routeburn too, between McKenzie and Howden Hut."

Glenorchy-based John Henderson Construction completed most of the work on the eastern side of the Routeburn.

"John's a very important contractor for us," Hopkins says.

"He's been working in this space for probably 30 years, primarily on the eastern side. He's repaired the Lake Sylvan Bridge, Sugar Loaf bridge, Routeburn Flats bridge, another at Junction Flats and the track realignment."

About 20 DOC staff have also worked on the project.

They include the three project managers working remotely from Hokitika, the structural engineers, the senior principal rangers - one in Glenorchy and one in Te Anau, their teams and the staff in the district offices.

There were also two helicopter firms, Glacier Southern Lakes and Glenorchy Helicopters ferrying people, materials and equipment, racking up hundreds of flights.

Hopkins says the workers have operated in challenging conditions including spring snow, particularly the contractors, chasing the goal of reopening in time for the tramping season.

"It's a different beast from working alongside the highway, or something like that. These guys are away from home for extended periods of time.

"They're in remote locations living in quite trying conditions, temporary camps, that sort of stuff." 

Their safety was paramount, particularly working with helicopters in poor weather and in steep terrain.

"Our gratitude goes to everyone involved; it's been a real collaborative effort."

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And they're not finished yet

"The first chunk is done, but this is a three-year project."

Work includes rerouting a kilometre of the Dart Track, various other repairs and replacing three suspension bridges, Lake Sylvan, Bedford on the Dart, and Poseidon Creek on Milford

Then the project will move towards more preventative work, especially in light of climate change and growing visitor numbers. Sites in the Hollyford Valley, Lake Marian, Key Summit, the Chasm will be the focus.

By Paul Taylor, Editor, Queenstown App

[email protected]

Republished by arrangement