Spending millions upgrading Dunedin's stormwater infrastructure to better withstand floods would not be possible in the next year and increases would have to be ramped up over time, councillors were told.
Council water and waste group manager Laura McElhone made the comment when asked by Cr Kate Wilson whether it would be possible, as an example, for her staff to manage spending an extra $10million in the next year.
This came as councillors discussed calls from submitters to invest in infrastructure improvements, particularly in light of issues from last June's floods.
Dr McElhone said spending $10million in the next year would not be possible.
It was difficult enough at present to complete all the renewal work on time and in previous years, scheduled work had often needed to be carried forward to the next financial year.
"If you were talking about $10million phased in over the next five years, then that's a much more reasonable proposition.''
She reiterated that the current strategy involved maintaining existing service levels, which meant the focus was on renewing deteriorating infrastructure.
Cr Hilary Calvert asked about the cost of upgrading infrastructure to the standard where it could withstand a one-in-10-year storm event.
Dr McElhone said a costing exercise had never been done but she estimated doing this across the city would cost hundreds of millions, if not more than a billion dollars.
At the moment, the focus was on areas where people were having problems, including from flooding, every two or three years.
In response to questions from Cr Andrew Noone, she said she was comfortable the council was prioritising the "highest risk'' areas when it came to infrastructure upgrades.
However, it was difficult to gauge "how fast the network is deteriorating'' and she could not be certain infrastructure was being upgraded as fast as it deteriorated.
Councillors also discussed flooding in Mosgiel during last June's flood. Cr Lee Vandervis brought up the example of a retired couple from Woodland Ave who had furniture floating around their house.
"They were deeply traumatised and upset,'' Cr Vandervis said.
Their case highlighted the need for investment in areas outside South Dunedin.
"Please don't just look at South Dunedin.''
Dr McElhone said staff were looking at a solution to help reduce flooding in Woodland Ave in future events, but it was not as "simple'' as had been suggested and would cost about $350,000.
Cr Mike Lord brought up concerns about mud-tank maintenance in Mosgiel.
Council infrastructure networks general manager Ruth Stokes said the council was working with Fulton Hogan to ensure it was fulfilling the specifications of its contract to maintain the city's mud tanks.
