The discovery of a partially-collapsed stormwater culvert underneath the only rail link into Port Taranaki is not unexpected but an example of a "nasty surprise", New Plymouth's mayor says.
Mayor Neil Holdom said the damaged culvert was yet more evidence of historical underinvestment in the city's infrastructure.
"It's just another one that reflects when you don't inspect and adequately maintain you're going to find these nasty surprises."
Holdom did not believe the railway line above the collapsing culvert, near New Plymouth's East End beach, was at risk.
"I haven't heard that it's material risk in terms of the railway line. I think the concern is that when these culverts have collapsed is that in peak conditions where we've got high rainfall etc they may not be able to do the job they're designed to do so we can end up with environmental risk and property damage."
It was up to the council to find these problems and get them fixed, Holdom said.
New Plymouth District Council three waters manager Mark Hall agreed the pipe needed repairing to prevent it backing up in heavy rain.
"It's a partial collapse so stormwater's still getting through, although the pipe itself is now more oblong than circular. It's an example of the challenges we face to maintain 1700 kilometres of pipes - all things wear out eventually."
In July, 2020 the council was forced to replace 60m of pipe after a culvert after a culvert collapsed at Waiwaka Terrace in the city.
Engineers estimated the repair job would cost $2.5 million. No estimate has been provided for the cost of fixing the East End culvert.
In its draft 10-Year Plan for 2021-2031, the council is proposing to spend $248m on water infrastructure.
To help pay for this, it's proposed to raise rates 12 percent in the first year and by 6 percent in each of the subsequent nine yeas of the plan.
Mr Hall said if the budget was approved, projects such as collapsing East End culvert repair would likely go to the top of the priority list.
Public submissions on the draft long-term plan close on April 6.