Capital almost ran out of water
Wellington came dangerously close to running out of water after a leak was found in the city’s main supply pipe.
Workers found the cause of the leak – a valve connected to the main water pipe underneath Featherston St, near Wellington Railway Station – at 1pm on Friday.
They also discovered a 10-15 cubic metre hole – big enough to hold a people-mover – that had been created under the road by the leaking water.
Utilities company Wellington Water believes the leak was caused by the magnitude 7.8 Kaikoura earthquake on November 14, which was felt strongly in the capital, or one of its subsequent aftershocks.
Given the size of the cavity, motorists were also ‘‘lucky’’ that Featherston St was a strong road, Wellington Water spokesman Alex van Paassen said.
The erosion of the road underneath Featherston St was ‘‘exactly the kind of conditions’’ that could lead to a sinkhole.
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 city’s central and eastern suburbs slowly emptied out through the night.
Wellington Water acting chief executive Mark Kinvig said the company came ‘‘pretty close’’ to asking all residents 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.’’
Fortunately, its repair crew managed to patch the leak by 3am on Saturday.
Workers were back at the site yesterday to permanently repair the leaking valve, which is attached to the 800mm main pipe buried four metres’ deep.
A careful check of exposed pipes was carried out after the November earthquake but, given that many of Wellington’s pipes were buried quite deep, it was ‘‘a bit tricky’’ to check them all 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 explained.
Daily, about 50 million litres of water goes through the supply pipe, 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 recent quake was a wake-up call for people and businesses to prepare for the loss of water.
Plans were in place to make the city’s system more resilient, including building a 35 millionlitre reservoir in Prince of Wales Park, and for an alternative pipeline into the capital. But both projects would cost tens of millions and take years to complete.
People should store enough water at home to take care of their health and hygiene needs for seven days in the event it could not be supplied.
Wellington City Council is unlikely to push for changes in the way pipes are checked, as the Featherston St leak was ‘‘discovered and fixed’’ in good time, spokesman Richard MacLean said. There was no way to ‘‘proactively check the entire water system, there has to be a clue’’, he added.
‘‘We are just glad we spotted the leak before the problem became dangerous.’’
The council became aware of the issue after it was spotted by staff looking at footage from local traffic cameras. The leak was repaired yesterday but work will continue today to re-seal the road.
The incident was a reminder that residents must be well prepared, said Wellington Region Emergency Management’s Bruce Pepperell. ‘‘The ramifications of the earthquake will be with us for some time yet.’’