Society committee member and Pisa Moorings resident Ian Paterson said the council's application for consent to build a 2 million-litre water reservoir on the Sugarloaf hill to supply the wider Pisa area was riddled with misinformation.
The application stated the Pisa Moorings supply was "insecure" according to the New Zealand Drinking Water Standards, and required complex water treatment plants.
"It's full of inaccuracies - the council obviously hasn't done its homework," Mr Paterson said.
He said the council's perceived need for a reservoir was "nonsense" and a "complete waste of ratepayers' money".
"If our supply was proven to be insecure we would put a UV treatment plant in."
Council utility services manager Peter Greenwood said Paterson Pitts Partners Ltd, which prepared the council's application, had "intimate knowledge" of the Pisa Moorings supply, as it had been involved in the construction and commissioning of the independent scheme.
"Water supply information was also verified with McNeill Drilling, which installed the lakeside bore. If the council has it wrong and the supply is secure according to the criteria outlined in the [national standards], then the council apologises," Mr Greenwood said.
He said the supply came from a shallow bore near residential properties.
For a supply to be deemed secure, it had to be demonstrated to be either from a deep source, from a confined aquifer, or be regularly monitored.
"The process of proving bore security is involved. The new reservoir is required to provide security of supply ultimately, for the Pisa area and the Lowburn Valley area.
"It is also anticipated that water could be drawn back into Cromwell from the Pisa Area reservoir, should such a situation require it to improve security to the Cromwell township," Mr Greenwood said.
Mr Paterson personally lodged a submission opposing the application, and the society also lodged one that did not support or oppose the application, aiming to address what it deemed to be inaccuracies in the document.
Mr Paterson said the society's supply had been regularly tested and it was deemed to be as good as bottled water.
If the council built a reservoir, it would cost residents between $3000 and $8000 to connect to the new scheme.
The council's application stated Pisa Moorings residents would not be compelled "in any way" to connect their private scheme to the council supply.
An independent commissioner will preside over a hearing for the application later this year.
Water worries
Residential subdivisions in the Pisa area, 10km north of Cromwell, include Pisa Moorings, Wakefield Bay, Pisa North, and Perriam Cove.
There are three separate existing arrangements to supply water to those subdivisions, two of which involve the Central Otago District Council.
The council proposes to establish a 2 million-litre water reservoir on the Sugarloaf hill formation, across State Highway 6 from Pisa subdivisions, to serve the whole community.
It would connect Pisa households to the Cromwell water supply.
