The Waiho (Waiau) River bridge at Franz Josef Glacier will be lifted yet again this winter, at a cost of $1.6 million.
The bridge was last lifted by 2m in 2011, by 1.5m in 2002 and also in the 1990s because of the continual build-up of gravel in the glacier-fed river.
Since the last lift just six years ago, the riverbed has risen between 0.5m and 1.5m.
New Zealand Transport Agency regional performance manager Peter Connors said the bridge lift was part of a series of resilience works at the Waiho, including improvements to the surrounding stopbanks.
The riverbed level fluctuates due to large volumes of sediment being washed down the river during high flows. Since the last time the bridge was lifted, the riverbed has fluctuated between 1.5m and 0.5m higher, following the general trend in build-up since monitoring started in 1997.
The construction works, including raising the Bailey bridge structure and the bridge approaches, are due to commence in May or June, with night-time road closures required to allow the contractor access.
- Greymouth Star