SH50 Waipawa River Bridge deemed structurally sound after washout

Despite a massive washout, the Waipawa River Bridge on State Highway 50 has been assessed as structurally sound ahead of its restoration.

State Highway 50 between Ongaonga and Tikokino closed overnight Friday-Saturday after a large part of the road and the Waipawa River Bridge abutment - the structure built to support the end of the bridge - was washed away due to the river flooding.

The closure has already had an impact on the small Central Hawke’s Bay communities along SH50, with a rural retailer saying they had felt the financial impact since the highway closure reduced traffic on Saturday.

Despite appearances, the Waipawa River Bridge on State Highway 50 has been assessed by Waka Kotahi engineers as structurally sound, with repairs due to begin soon. Photo / Waka Kotahi NZTA

A Waka Kotahi New Zealand Transport Agency spokesman said the agency will be preparing the site in the next few days to begin work to restore the washed-out road approach.

“Engineers have been at the bridge [on Monday] and have assessed the bridge structure as structurally sound. The bridge structure was built in 1980,” the spokesman said.

He said there would be a better indication of the timeframe once the design work had been completed and local communities and iwi would be kept up to date with progress and planning as soon as Waka Kotahi could.

“We know SH50 is a crucial link into Hawke’s Bay from central North Island and the lower North Island, and we thank all road users and communities in the area for their patience while we work towards restoring this access.”

Hawke’s Bay Regional Council contractors will divert water away from the washout to enable the works for the new abutment to begin.

Hawke’s Bay Regional Council contractors will divert water away from the washout to enable the works for the new abutment to begin. Photo / Paul Taylor

Chris Dolley, HBRC asset management group manager, said diverting the channel usually involved shaping a new channel for the river to divert water away from the work area and then blocking off the existing channel.

“Water needs to be diverted away from the bridge abutment area so that earthworks and construction work can be completed to reopen the bridge,” Dolley said.

“This work may also include armouring the abutment and river channel directly upstream to prevent future damage to the bridge.”

It has not yet been determined where the river will be diverted to, but Dolley said it would be either the centre or the other side of the river bed.

“We would normally leave the diversion in place and then usually the river will change during the next fresh flow, where it would typically form a number of braids,” he said.