Olympic-sized pool of sewage spilling into Wellington Harbour for second day
Saturday, 21 December 2019
It could take up to three days to halt the daily flow of an Olympic-sized pool of sewage into Wellington Harbour.
And swimmers could be waiting a week after that till they can return to the water.
On Saturday Wellington Water chief executive Colin Crampton said staff were working on a bypass around the collapsed tunnel pushing wastewater into the harbour.
He said it was hoped the plan, temporarily closing an about-200-metre section of upper Willis St, could be completed as soon as in a day. However it could take up to three days. It could be up to a week after that till people could return to the water.
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The section of Willis St, between Dixon and Ghuznee streets, would remain closed till the work was completed.
Crampton said the daily flow of wastewater into the harbour would be enough to fill an Olympic-sized pool. Tests showing bacteria levels in the harbour water would not be ready till Sunday.
The wastewater was running into the harbour at about 50 litres a second – about 4.3 million litres a day.
He said the wastewater could not infiltrate drinking water around the harbour.
Asked if there had been underspending on wastewater infrastructure, he said Wellington Water was 'comfortable' with the way it managed the pipes.
'We just think this is a one-off issue, particularly in this area. But… we're going to check other parts of the network to make sure we haven't got the same sort of problems.'
Crampton said it was 'hard to tell' whether work on the pipes before the collapse actually caused the problem.
Workers were digging to the pipe to find out what was causing initial problems. 'We thought we'd stabilised it… but it ended up collapsing further.'
On Friday morning Wellington Water announced sewage was flowing into the harbour after a tunnel collapsed under Dixon and Willis streets.
Officials did not know how much would pour into the harbour, or how long it might last – except it would likely continue for days. The main discharge points were expected to be the Whairepo Lagoon and the diving platform.
The tunnel was made from concrete and was about 137 centimetres high and 91cm wide – dug by hand in the 1930s.
The bypass would send the wastewater around the blockage, up about 200m of Willis St, and back into the system to the Moa Point treatment plant.
Officials hoped to use an existing decommissioned underground pipe and were building an above-ground connection too as a back-up.
Wellington Water waste water chief adviser Steve Hutchison said it would be a temporary fix till a permanent solution was found.
On Friday Wellington Water urged people to stay out of the harbour between the port and Point Jerningham. This included no fishing or collecting shellfish.
A rāhui, or temporary prohibition on water activities, was placed over the inner harbour in the afternoon.
By Saturday the rāhui was still in place. 'Please continue to stay out of the water, and do not go fishing or collect seafood,' Wellington Water said.
Wastewater and sewage are the same thing – a mixture of water and human waste, sent from homes and businesses to a wastewater treatment plant.
It's not the first time raw sewage has entered the harbour – in August effluent was being pushed out of stormwater pipes under Foxglove restaurant on Queen's Wharf until contractors were able to clear a blocked wastewater pipe.
In June, Wellingtonians were told to stay out of the water after a suspected sewage leak around and near Shed 5, between Frank Kitts Park and the TSB Arena.
Previously Crampton said Friday's collapse would cause a much greater amount of sewage to leak in to the harbour compared with the events in June and August.
On Saturday Crampton said patrols were in place around outflows to catch any 'unsavoury' items running into the water.