The Invercargill City Council has decided it is prepared to risk waiting to establish a fully alternate supply rather than a lower capacity emergency one.
Cr Lesley Soper cautioned the committee at a meeting last week about approving the emergency supply option as it could be a "millstone around the neck of the council we are welcoming in October".
She preferred the council wait for additional technical information that would become available later.
"We are talking about a wetland area and that for me signals just how importantly we need to treat this matter and how careful we need to [be] about the effects of pumping and the effects on our environment.
"This is not an area we can afford to play around with at an early stage, without the maximum amount of information."
It had taken several years to reach this point and waiting a further two and a-half years for the best outcome was asking too much of the council, she said.
It would take up to two years to establish an emergency supply connected by pipework into Bluff’s main water pipe.
In the event of an emergency, the 3million-litre draw would still require the city’s 55,000 residents to be water-rationed.
The committee voted to delay the project in favour of a fully alternate supply that would provide the council time to construct a dedicated main trunk, a new water reservoir and unlock further capacity for industrial and regional development.
Invercargill was the only city of its size in the nation with a single supply source and only two days’ water storage.
Infrastructure and strategy committee chairman Grant Dermody acknowledged the singular supply posed a risk to residents in the event of severe drought or contamination.
The council had been searching for an alternate supply for the past 10 years but announced earlier this year it had identified an aquifer in the Awarua Plains as a potential supply source.
The site was being tested to determine whether it could supply a reliable alternative water source.
Initial modelling suggested the supply was high quality water but would only yield 3 to 5million litres a day — below the capacity required for an alternative supply.
While exploratory drilling had been completed, council staff wanted more time to also explore subsidence analysis in the area if more water was drawn off.
Council infrastructure services group manager Erin Moogan said staff were still unsure if land, shrunk by the water take, would become flood-prone or at risk of sea water inundation, or what impact an intake would have on the area’s wetlands.
— Toni McDonald
