Rapid repairs kept highway open

SH94 to remote Milford Sound was severely damaged during a savage storm and, despite the various pandemic lockdowns, the Milford Road Alliance worked tirelessly to reopen the highway as quickly as possible. Richard Silcock reports.

During a massive, torrential rainstorm that hit Fiordland in February, the state highway from Te Anau to Milford Sound was severely impacted with flooding, washouts and significant structural damage to some bridges.

Forty millimetres of rain fell in little under an hour and over a metre fell during the three days of the storm.

The highway through the National Park was immediately closed due to the extent of the damage, with over 45 highway washouts, fallen rocks and other debris along the 120-kilometre scenic route.

Manager of the Milford Road Alliance (1) Kevin Thompson says they were able, within five days of the event, to form a 4WD access track to allow their assessment teams to inspect the extent of the damage and for several emergency vehicles to reach the small village at Milford Sound.

“Some 600 people became stranded at Milford Sound, these being mostly tourists, tourism operators and commercial fishermen,” he says.

“As the only other access is via boat or small aircraft, our first priority was to create a safe, albeit restricted temporary access road to get the tourists out, get food deliveries in and allow for any emergencies.

“Following our extensive inspections of the damage by helicopter and on foot we were able carry out urgent temporary remedial work.

“It was a case of building a temporary road as we progressed along the highway using bulldozers and excavators to clear the way.

“We were able to establish a rough single-lane road to allow essential services and commercial vehicles, travelling in convoy, to take in supplies and equipment.

“This was later extended to include coaches carrying tourists both in and out as it was equally important to get those stranded out and others in, as it was the height of the tourism season and the various tourism operators depend on the highway being open to maintain their operations and livelihoods. (2)

“Our focus then switched to the actual repair of the highway. To achieve this, the repair and design teams worked through the level four lockdown to plan and ensure resources and processes were in place to start work as soon as possible.”

By far the worst area hit was a 20-kilometre section of highway near the Hollyford Valley Road turn-off, about 10 kilometres east of the Homer Tunnel entrance at around 600-700 metres above sea level.

Kevin says in this section there was extensive damage in a number of places, the most complex being alongside the Hollyford River where two large gabion walls that support sections of the highway had collapsed and the Falls Creek Bridge approaches which had been severely compromised.

Other damage included 50 to 500 metre sections of the highway that were completely washed away (3) by the raging river and torrents of water sweeping over the road, removing both the pavement and base course. In the steeper terrain areas beyond the Homer Tunnel water also destroyed both the road and drainage infrastructure.

Other less critical damage extended along the entire length of the highway with blocked culverts, washouts and pavement deterioration.

Downer, as a member of the Milford Road Alliance, manages the day-to-day operation and maintenance of the highway, and led the repair project with the help of some local sub-contractors.

“Downer were engaged for this repair work due to the urgency, their intimate knowledge of the highway and experience of working in Fiordland National Park with its harsh climate and avalanche zones,” says Kevin.

“They are well set-up with resources, plant and equipment to work in this extreme environment from our base at Te Anau.”

The repair work entailed the reinstatement or repair of key highway infrastructure including culverts, walls and bridges.

“The work was staged and planned around access to the river, the avalanche/snow conditions over winter and other environmental considerations,” says Kevin.

“The Falls Creek one lane bridge was a key piece of damaged infrastructure that took the full force of the flooded Hollyford River and required extensive work to restore the abutments. We also needed to construct a ‘stone-strong’ wall to reinforce the approaches.

“The design and consenting of structures was undertaken in tandem to ensure we are able to progress the project without delays, while still meeting consenting procedures, physical works oversight and safety throughout the project.

“However, due to the extent of the work required it is likely to take at least another six months to fully complete.

“As the highway is used by some 2600 vehicles, including tourist coach operators, each day during the height of the spring/summer season it is imperative that we get the highway fully reinstated before then to give certainty to the tourism operators, commercial fishermen and other park users.

The temporary road is now open to all vehicles but there are a number of single-lane sections and speed restrictions in place, however repair crews are working to minimise disruptions to travellers and other users of the highway during the construction period.

“Keeping this highway safe and operational is paramount, but it is a challenge,” says Kevin.

“It is one of the realities of having a scenic highway in Fiordland National Park which over the winter requires very close access management and the use of advanced weather warning systems to predict and prepare for extreme storms.”

The estimated cost of the project is likely to be in the region of $9 million.

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