The Dunedin City Council has moved rapidly to head off potential water contamination in Mosgiel, announcing 10,000 residents will switch to town water on Monday.
The council announced the move yesterday, following a report that said faecal matter had in the past contaminated the system of bores used in the suburb.
Council chief executive Sue Bidrose said yesterday there was nothing wrong with the suburb's bore water at the moment.
''Those bores meet the current drinking water standards.
''However, in the future they may become contaminated. That's a risk. We've become aware that risk is increasing and it's not a risk we're willing to take.''
Council staff had spent a week and a-half preparing for the changeover, which would take place early on Monday.
Asked if the public should have been consulted, Dr Bidrose said: ''I don't think public safety's something you consult on.
''Providing safe drinking water that we're absolutely confident is safe is an absolute core part of council's job. There's not a lot of point consulting on something where there aren't really any other options.''
The council had not sought legal advice on its responsibility in the case of a Havelock North-style incident.
''We've all be talking about the Havelock report - I think the whole local government sector's been talking about the Havelock report.
''It's made all councils around the country spend a lot of time thinking about where our risks lie.''
The Mosgiel water supply does not contain fluoride or chlorine.
Asked about those opposed to fluoride and chlorine in their water, Dr Bidrose said some people would be unhappy.
However staff had checked there were plenty of businesses selling water filters.
International drinking water consultant Colin Fricker had been asked by the council to assess Dunedin's water supply to help it understand any risks in the system.
Dr Fricker said in his report he was in no doubt the council should discontinue the use of untreated groundwater to supply Mosgiel.
Dr Fricker recommended either the council should treat the bore water with ultraviolet light and chlorine or supply Mosgiel with water already treated.
Historical data of the aquifer and the presence of E. coli in the water supply on several occasions contradicted the suggestion the groundwater used in Mosgiel was safe and confined, he said.
There was conclusive evidence faecal matter had entered the groundwater several times when surface water flowed into the aquifer.
''In every jurisdiction in the developed world, treatment of such water is mandatory,'' Dr Fricker said.
Cr Mike Lord said there was no way the council could ever say the bore water was completely safe, which is why the supply needed to be changed.
Mosgiel-Taieri Community Board chairwoman Sarah Nitis said she was in favour of the switch, but understood why some residents were not.
''Yes, our bore water is clean, but that doesn't stop the risk of contamination.''
