Sewage continuing to leak into Wellington Harbour
Sunday, 22 December 2019
Wellington's wastewater leak has been reduced to one-tenth of its size, meaning a new year's dip at Oriental Bay could be on the cards.
Workers have worked through nights after a wastewater pipe collapsed at the corner of Wills St and Dixon St on Friday.
At its peak it sent up to 100 litres of wastewater per second into the harbour - roughly a swimming pool's worth per day.
On Sunday, this had been reduced to 10 litres per second after much of the wastewater was diverted through a disused 1890 pipe beneath Willis St, Wellington Water chief executive Colin Crampton said.
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An overground pipe was also being installed as the ability of the 1890 pipe to carry the full amount of wastewater was uncertain.
A rāhui, or temporary prohibition on water activities, was placed over the inner harbour in the afternoon.
Crampton said there should be a big improvement in the water quality and, all going to plan, the water should be given the all clear within seven days.
The works at the corner of Dixon and Willis - that had caused the tunnel's collapse - were to check the state of the pipe. They would now be abandoned in favour of a complete replacement.
The tunnel was made from concrete and was about 137 centimetres high and 91cm wide – dug by hand in the 1930s.
Crampton said the overground pipe would remain down Willis St for some time though the road would be able to reopen, even if narrower.
The section of Willis St, between Dixon and Ghuznee streets, would remain closed till the work was completed.
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' what caused the collapse of the 80-year old tunnel.
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 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.
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.
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.