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Ratepayers could be asked to pick up a six-figure bill if the Dunedin City Council opts to provide an alternative, non-fluoridated water supply for those wanting to avoid the chemical.
Options for offering alternative, non-fluoridated drinking water would be considered by councillors at this week's annual plan budget meeting, beginning on Thursday.
A council staff report to the meeting outlined three options for providing the service, ranging from encouraging people to buy filters for their homes, to more expensive filtered public tap supplies at locations around the city.
Encouraging ''point of use'' filters would allow those wanting to avoid fluoridated water to do so, by buying under-bench filters for their homes, the report by council water and waste services asset strategy team leader Tom Dyer said.
The filters cost between $100 and $400 each, and claimed to effectively remove between 90%-100% of fluoride, as well as other impurities, he said.
The council could also consider offering a subsidy as part of efforts to promote their use, he said.
The second option would be to invest in one or more public water taps, filtered to remove fluoride as the ''Speight's tap'' already was, at locations around the city, he said.
However, ''appropriate'' traffic management, access and parking arrangements would be needed, meaning each site could cost the council $15,000-$25,000 to establish and about $7500 a year to operate, he said.
The council would also need to give ''careful consideration'' to the level of serve required across the city, he said.
An even spread of public taps - for example allowing each property in the city to be within 10km of a tap - would require about six taps to be installed, he said.
That would mean a total capital cost of up to $150,000, and annual operating costs of $45,000, for the council, he said.
The third option was to install alternative, non-fluoridated taps at the Mt Grand and Southern water treatment plants, by diverting some of the flow through the plants before fluoride was added.
That, too, would come at a cost, estimated to be $40,000-$50,000 per site and annual operating costs of $6500 per site, he said.
Council staff have been considering the issue since last year's annual plan meetings, when councillors voted to ask staff to investigate options for a non-fluoridated drinking water supply.
That move came after the council received 34 public submissions on fluoride - more than any other subject - with most concerned the chemical was being added to drinking water for oral health benefits.