Some of Auckland’s ageing wastewater pipes are getting a new lease on life thanks to trenchless technology being used to reline the pipes.
Auckland’s water and wastewater service provider Watercare is nearing the end of a $4.5 m project to upgrade the wastewater network in the seaside suburb of Takapuna.
Watercare project manager Johan Gerritsen says relining the 1.6 km pipe that runs the full length of Takapuna Beach will significantly reduce wastewater overflows and improve beach water quality.
“The original pipe was built in the 1940s and was a mixture of concrete and cast iron. Earlier this year we discovered it was in urgent need of an upgrade to prevent exfiltration, so, with the help of our construction partners March Cato, we moved quickly to design and deliver a solution,” says Gerritsen.
“By relining this section of pipe with PVC, we’re giving an 80-year-old asset another 50 years of life – and we’ll significantly reduce wastewater overflows in the area.”
In addition, a team from Interflow came over from Australia to carry out the relining work.
A mechanical self-propelling device lines PVC through the pipe by spinning around and lining the inner circumference.
“The PVC is spun into the pipe and extended from one manhole to the next. When it’s all in place, a locking system is released and the lining slowly expands to create a seal against the existing pipe,” Gerritsen says.
“The beauty of this trenchless method is that the wastewater pipe can be kept in service while the relining work is carried out.
“We monitor flows and can continue working with flows up to 30 per cent – if it looks to be getting higher than this, we stop work.”
Downpours over winter have brought the project to a halt a number of times, but most of the work is now complete. More than 30 manholes have also been assessed and repaired where necessary.
“We check for leaks, cracks, tree roots or damage to make sure the manhole is going to last another 50 years, in line with the pipe,” Gerritsen says.
With most of the relining and manhole assessments now complete, the next focus is carrying out the lateral joint repairs, where other pipes connect to the recently relined trunk sewer.
“We found an alternative solution to fixing the internal connections to our trunk main. It’s a great win for us – it means we don’t have to dig up people’s properties to seal the joints at each connection to the main trunk sewer,” says Gerritsen.
“The particular machine we’re using for the lateral joint repairs has a camera inside so you can see the work as it’s happening, and the operator can carry out the quality assurance checks as it’s being installed, which is a big advantage.”
Work also ploughing on in central suburbs
A similar wastewater pipe relining project is underway on the other side of Auckland, in the city fringe suburbs of Parnell and Newmarket.
Under Gerritsen’s direction, about 3.8 km of ageing wastewater pipes will be relined using the same technology. The project is at its half-way point.
“One of the biggest challenges we face is finding specialist contractors available to do the work,” Gerritsen says. “There simply aren’t enough for the amount of work we want to do here in Auckland.”
For more information visit Watercare.
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This article appeared in the October edition of Trenchless Australasia. Access the digital copy of the magazine here.