In March 2019 the West Coast was battered by one of the most intensive storms in the history of Aotearoa. Torrential rain caused raging floodwaters that swept away the Waiho Bridge, severing the main transport link between Franz Josef to the rest of southern Westland.
As the Structures Management Consultant for the region, our team of engineers, technicians and bridge inspectors responded immediately to the news of the bridge collapse.
WSP along with key contractors and the New Zealand Defence Force, achieved months of investigation, design and construction work in a short space of time.
The Waiho Bridge is a Bailey design, a modular form of system that is versatile and relatively quick to erect. The Waiho River is a challenging and constantly changing environment, with a riverbed level that fluctuates due to large volumes of gravel being washed down the river from the surrounding valleys. A Bailey bridge was installed on a semi-permanent basis as it can be raised to accommodate the unstable nature of the riverbed. The previous Bailey bridge had been lifted several metres since 1990 because of rising riverbed levels.
WSP oversaw the coordination, deconstruction, repair and recovery of the 170m bridge, which required innovative solutions due to the complex design and construction challenges.
We ensured that resilience was incorporated within the recovery design, with the northern approach retention and northern pier designed to be significantly more robust; ready for unexpected future events.
The loss was estimated to cost the West Coast Region between $2-3m per day however, in just two weeks, the bridge was reopened and the community reconnected.
Insights from this project have been shared to continue improving how we respond to emergency events in New Zealand.