Single water supply deemed a risk

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Invercargill City Council water manager Alister Murray at the Invercargill Water Works on Doon St.

IF Invercargill’s sole water supply became contaminated or failed, the impact on the community would be “extreme”, councillors were told at an Invercargill City Council (ICC) infrastructure and services committee meeting on Monday, July 31.

A report outlining the need to establish a second water supply was presented at the meeting. The project was estimated to cost upwards of $8 million.

“If you have a separate system, it would at least halve the risk,” ICC water manager Alister Murray said.

This was not a new proposal, but rather the council had requested an investigation into whether there was a need for the city to have an alternative/emergency water supply, he said.

“It has always been the strategic aim, but, as it represents a considerable investment, it required more information.”

At present, Invercargill has a single water supply – the Oreti River/Branxholme Treatment Plant – and should it fail or become unserviceable the consequences would be “dire”, potentially resulting in an evacuation if the service could not be resumed within several days, council facing claims from businesses forced to close, a government inquiry and widespread community discontent, the report said.

Most New Zealand urban communities of a similar size to Invercargill had more than one water supply, the report said.

Two possible options for a second water supply identified in the report were ground water or self-storage.

Mr Murray favoured the ground water option.

“It is a cost-effective option with a complementary risk profile, so it is worth investigating.”

Whether the second water supply would feed into the existing system or a separate reservoir be established had yet to be decided, he said.

Before 1960, Invercargill’s water supply was sourced from underground bores, but the water quality was poor with high concentrations of iron and magnesium despite being treated, he said.

When asked if this would not be the case again should the ground water option be approved, Mr Murray said: “It would depend on the watersource. We would be looking for a better quality than the ones in the past.”

If approved, the project would be spread over two years between 2025-26 and 2026-27, estimated to cost $4,250,000 per year.

The councillors voted 3:2 in favour of the proposal to retain the development of an alternative water supply in the council’s long-term plan. It will now go before a full council meeting on August 15.

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