The New Zealand Transport Agency (NZTA) has stood by protection works it did on the Waiho River, despite criticism it contributed to a large portion of a bridge washing away in heavy rain on Tuesday.
NZTA systems manager Pete Connors said the bridge's failure was in part due to the degradation of the riverbed, which was doing so at a rate of about 150mm a year.
"If you talk about that at the bridge site, you're talking about a rise of about 10 metres and it's unsustainable for the future.
"The problem with this river is well documented."
He said there were four failures at riverbanks on the day of the heavy rains.
"In terms of the river, the protection works held up pretty well despite the fact that we had a catastrophic failure of the bailey.
"We lost a small part of the abutment which had catastrophic results for the bridge itself but in terms of doing the protection it was meant to do, it held up pretty well."
The works had prevented further damage, he said.
Mr Connors said NZTA was working hard to ensure the bridge was fixed on time, in the seven-to-10 day timeframe.
"There's a whole lot of pieces of the jigsaw that has to come together and … as we speak that's happening."
There were no access issues for workers to get to the bridge.
Workers were presently building a ramp to help build the pier.
Mr Connors said the bailey bridge was being replaced in pieces in a way not dissimilar to the way a kit-set house was built.
"We're pulling out all the stops to get it up as quick as possible."