A pipeline could be built across Wellington Harbour to supply fresh water from the Hutt Valley to the central city if an earthquake cut the mains supply.
The underwater pipeline could run from Gracefield to Miramar to connect the Wainuiomata and Waterloo water catchments to the city.
Greater Wellington regional council had been asked to investigate the idea by the Wellington City Council, as technology had improved to the point where it might be feasible, regional council general manager of water supply Chris Laidlow said.
"We've been told there have been a lot of advances . . . we'll be investigating what they are, what it looks like, what equipment might be needed and what the costs are."
The pipeline would provide some security for the central city's water supply, which is vulnerable to disruption. The main supply lines run by land from storage lakes at Te Marua, through the Hutt Valley and into Wellington, crossing fault lines several times.
A report from the Wellington Lifelines Group last year suggested parts of the central city could be without safe water for 75 days if a big earthquake hit.
"[The pipeline] would be able to get water into the city more quickly," Mr Laidlow said.
The council would be meeting engineers who had done similar work in the past to discuss ballpark costs. "We would then get into a full feasibility study, but we haven't committed to doing that yet.
"There could be some cheaper options for providing emergency water than the pipeline, but there could be some operational benefits [to the mains supply] in having [it]."
The pipeline would not affect plans to build new storage lakes in Kaitoke to augment the supply from Te Marua, he said. A proposed storage lake at Takapu Rd, near Tawa, to supply Porirua in an emergency, would also not be affected.
Wellington City Council spokesman Richard MacLean said discussions over the pipeline had only just begun. "It is very, very early days in the process."
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