Watercare is working around the clock to complete bypass pipe by early next week. Photo: Watercare
An independent review will commence tomorrow to find out what caused a section of the Ōrākei main sewer line in Auckland to collapse.
It has been two weeks since the combined waste- and storm-water pipe burst, and a 13-metre-deep sinkhole opened up in a carpark in Parnell.
While Watercare is working around the clock to complete a bypass pipe by early next week, wastewater continues to flow into the harbour at Mechanics Bay and the western part of the viaduct.
Watercare head of service delivery Sharon Danks said the review would look at what caused the pipe failure and the sinkhole and would examine the current pipe maintenance programme.
It was revealed at Watercare's board meeting Tuesday that the last time the collapsed main sewer line in Parnell was inspected was in 2019 - at which point no defects were found.
Danks said the once-every-five-years inspection of sewer lines was standard, but that might change to cope with climate change.
She said new technologies like underground drones and fibre optics would enable more frequent monitoring of the wastewater network, whereas the current method of floating CCTV cameras through drains had limitations and safety risks for workers.
This diagram shows the impact of the sinkhole on the Ōrākei main sewer. Photo: Watercare
After Cyclone Gabrielle Watercare had surveyed hundreds of kilometres of pipes in the North Shore and Waitākere where most damage was done, and the focus at the time had been on smaller pipes damaged by slips, rather than big pipes such as the Ōrākei main sewer line, Danks said.
Meanwhile, two-thirds of the bypass pipe has been laid and Watercare was aiming to have it operating by next Tuesday.
Danks told the board that while Watercare initially hoped the bypass would be ready by this Friday, the relocation of gas mains in the area had held up the process.
There was still about 5 metres of blockage left in the main sewer line, made up mostly of large boulders and rocks, she said.
Safeguards would need to be in place before staff remove the last bit of blockage, which could take three to four more weeks, she said. Until that blockage was cleared, there may still be risk in the main pipe when there is heavy rain.
Danks said a longer-term repair plan for the sewer line was still in progress.
Meanwhile, 25 beaches in the inner city and on the North Shore are still labelled as unsafe by Safeswim.
Watercare acting chief executive Dave Chambers said at the meeting today that while Safeswim and Healthy Waters were testing the water to be able to give recreational advice to the public, ecological testing would be separate from that.
Incident controller Nigel Toms said the ecological testing would not begin until after the bypass was complete and wastewater overflow into the harbour was under control.