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An interim solution to Naseby’s potable water woes is a step closer with an upgrade of the town’s treatment plant to provide service after weather events that affect drinking water quality.
The $570,000 upgrade could be in place within nine months.
At a meeting of the Central Otago District Council (CODC) in Alexandra on Wednesday councillors agreed to proceed with construction of a clarifier, pH correction, and flocculation tank, to be funded from water stimulus funding and to investigate options for an alternative water source for the Naseby water supply.
That investigation included considering a single Maniototo water treatment site later.
Torrential rain between January 1 and 4 resulted high turbidity raw water from the Hawkdun irrigation race being delivered to Naseby.
The treatment plant became inoperable, the reservoirs emptied, and water was cut to Naseby properties for 10 hours.
The plant was bypassed to enable raw water to be supplied and a boil water notice was in place for 28 days.
CODC infrastructure services executive manager Julie Muir told councillors the event had sparked concerns.
‘‘In particular, concerns raised by the community the reservoir had been run dry before the weather event occurred.’’
The report presented to councillors, which was based on a review by consultant Beca detailing the events of January 1 to 4, said the water treatment plant was operating at maximum capacity before the rain but was struggling to meet demand due to high visitor numbers.
The reservoir however had maintained a steady level between 80% and 96% up to January 1, indicating the plant was meeting demand during low turbidity over the peak period.
Ms Muir said the preferred option at this stage was an interim upgrade of the Naseby water treatment to allow the plant to operate during periods of high water turbidity in the Hawkdun irrigation race.
That included retaining the existing plant capacity until investigations into a new source and combined Maniototo water treatment site was completed.
Water restrictions and conserve water notices could still be needed if an event occurred that reduced plant capacity during peak demand.
The upgrade would allow water to continue to be treated during moderate turbidity events and would shorten the period of time for boil water notices during extreme climatic events.
The work would include the construction of a clarifier, pH correction, and flocculation tank improvements at an estimated cost $570,000 and CODC staff were investigating the possibility of obtaining a second-hand clarifier, she said.
The cost would exclude increasing redundancy, increasing capacity, and increasing storage which would be an additional cost of $4,740,000.