Water authorities are set to drill for drinking water in Wellington harbour in a bid to find a supply that keeps flowing following an earthquake.
A barge will drill exploratory bores into the harbour seabed off Miramar Peninsula with the water to be pumped out and tested for its quality.
Supplier Wellington Water hopes to establish a secure water source that does not need to be piped across quake fault lines.
Current water pipelines cross a series of faultlines as they travel along State Highway 1 and 2 from three treatment plants supplied by the Waiwhetu Aquifer, the Wainuiomata and Orongorongo rivers and Hutt River.
"In the event of an earthquake, it's likely that these main water pipelines will break and could take months to repair," the company says.
The drilling comes after a 2016 survey revealed the Waiwhetu Aquifer may extend under Wellington Harbour as far as the harbour's entrance.
The test bores will be drilled between 550m and 2km off the Miramar Peninsula and stretch in the direction of Eastbourne.
If the tests are successful a permanent bore could be working within two years.
Authorities hope it could provide 30 million litres a day, or about 20 per cent of the city's needs, RNZ reports.
If it is not possible to draw water from under the harbour, Wellington Water will investigate whether it can build an underwater pipeline to bring water from across the harbour.