Wellington wastewater problem: Roads to reopen as surface pipe comes to the rescue
Monday, 23 December 2019
Commuters travelling in Wellington City can rejoice - popular roads shut down by a collapsed wastewater tunnel are set to be reopened on Thursday but those wanting to swim in the harbour will have to wait.
Last Friday, a Dixon St/Willis St tunnel collapsed, causing more than two olympic-sized pools of wastewater to spill into Wellington Harbour.
Workers were pulled from their Christmas function to tackle the problem and, since then, 30 staff members have been working around the clock.
Wellington Water chief executive Colin Crampton said it was laying a large black pipe on the surface of Willis St which meant the roads could be reopened and manual pumping would no longer necessary.
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'When that's commissioned, we know we've got a very secure system,' Crampton said.
The black pipe, which will run along Willis St between Dixon St and Ghuznee St, will sit along parking spots for about two months.
Around the end of February, Wellington Water would then focus on its long-term plan which was to bury a pipe beneath Willis St.
The pipe would turn down a side road that goes towards a tunnel near the motorway and then it would all go back to normal, he said.
'We're going to block off the old tunnel on Dixon St where the collapse is - we don't want to operate that anymore.
'It's a very complicated underground system, it's deep and very tricky for our workers to work in it so we're happy to close that off forever and use this new system.'
The big question on everybody's mind though was this: When can people get back into the water?
Health and safety signs had been put up near the Taranaki dive platform and along popular swimming spots between the Port and Point Jerningham.
Iwi Taranaki Whānui placed a rāhui last Friday on swimming in the harbour.
That night, Wellington Water stopped sewage overflow into the harbour but at least two olympic-sized pools of wastewater had spilled into it, Crampton said.
'The minimum period is three days - we've got to take samples morning and night.
'We test it for bacteria and viruses and after three days, if all of those samples are clear, then we would technically be able to get back in the water.'
Wellington Water asked mana whenua to place a rāhui over the site so mother nature could restore the balance between the sea, the people and the environment.
'If everything goes well, we may well be able to lift that [the rāhui] by the weekend.'
HOW DID THE TUNNEL COLLAPSE?
Last Friday, Crampton said the tunnel, beneath Willis St and Dixon St had already been showing signs of wear.
'We had signals from residents that it was starting to smell in that area.'
Wellington Water was in the process of fixing it when it partially collapsed, and then completely collapsed on Friday morning.
'We hadn't established the extent of the damage at that stage.'
WHAT HAPPENS NEXT?
The entire network of other junction points would need to be checked, in case they had deteriorated to the same extent.
There was a piece of critical pipework in Thorndon near Sar St - similar to the one that collapsed - that Wellington Water would look at soon.
There were many pipes beneath Wellington made of asbestos and cement, cast iron, and earthenware.
The number of complaints about leaks had increased since the 7.8-magnitude quake in Kaikōura, suggesting that was partly to blame.
'All of them are coming to the end of their useful life,' Crampton said.