Earthquake likely put hole in Wellington water supply

Wellington came dangerously close to running out of water after a leak was found in the city’s main supply pipe.

A ‘‘big hole’’ was found in a valve connected to the pipe underneath Featherston St, near the Wellington Railway Station, at 1pm on Friday.

Workers also discovered a large cavity underneath the road where the pipe was broken.

Utilities company Wellington Water believe the magnitude 7.8 Kaikoura earthquake on November 14, which was felt strongly in Wellington, or one of its aftershocks, caused the leak.

Given the size of the cavity, Wellington motorists were also ‘‘lucky’’ that Featherston St was a strong road, Wellington Water spokesman Alex van Paassen said.

It was touch-and-go on Friday whether the capital would have enough water on Saturday morning, as the two main storage reservoirs supplying the central and eastern suburbs slowly emptied during the evening.

Acting chief executive of Wellington Water Mark Kinvig said they came ‘‘pretty close’’ to sending out a call asking all Wellingtonians to cut back their water use to only the bare essentials.

‘‘There’s really only one main supply pipe into central and eastern Wellington, and this was it.’’

Staff from Wellington Water and contractors worked until 3am on Saturday to temporarily stop the leak.

Workers were back at the site on Sunday morning to permanently repair the valve, which is attached to the 800mm main pipe, buried 4 metres deep.

A careful check on exposed pipes was carried out after the November earthquake but, given many of Wellington’s pipes were buried quite deep, it was ‘‘a bit tricky’’ to check them individually, van Paassen said.

Usually a leaky pipe could be spotted if there was a spectacular geyser that ‘‘makes it pretty obvious you have a problem’’ or a leak that seeps up from the ground, he said.

About 50 million litres goes through the supply pipe every day, which is connected to Wellington’s Macalister and Carmichael reservoirs.

Kinvig said the vulnerability of Wellington city’s water supply was well known, and the earthquake was a wake-up call for people and businesses to plan for the loss of water supply.

Plans were in place to make it more resilient, including building a 35 million-litre reservoir in Prince of Wales Park, and for an alternative pipeline into the city.

But both of these projects will cost tens of millions of dollars and will take years to complete.

People should store enough water at home for at least seven days, to take care of their health and hygiene in case the water goes out, Kinvig said.

Wellington City Council spokesman Richard Maclean said the council became aware of the ‘‘relatively small’’ leak after it was spotted by staff looking at footage from traffic cameras in the area.

As it had been wet in Wellington it was hard to spot and it was took until ‘‘a dry day to make itself known’’, Maclean said.

– Fairfax NZ