By rosebell
New Zealand’s largest city will host construction of a new wastewater pipeline in the coming Monday.
With the aim of improving water quality in the Manukau Harbour, a 1.2m-diameter TBM is due to be launched to build a new outfall at Clarks Beach in Auckland.
According to project manager Jason Salmon: “The NZ$22m (€11.6m) outfall installation was expected to take six or seven weeks.To ensure the resilience of the outfall, the pipeline will be double layered. The carrier pipeline, which is made from high-density polyethylene, will sit inside a steel pipe to prevent any leaks or ground and seawater intrusion.”
He aslso added: “To install the outfall the TBM will cut through the ground and install the exterior steel pipeline at the same time. Once it’s reached its destination, the carrier pipe will be pulled through and plugged until it is brought into service. A 66m-long diffuser will then be installed.”
The diffuser includes 22 rubber nozzles called duck bills, reflecting their shape resembling a duck’s bill.
In order to allowing the periodic release of treated effluent flow out but stops sea water flowing in, this nozzle has been designed in an special way.
The responsibility of lifting out the TBM will be up to a team of divers, who are going to unbolt it from the carrier pipe in the outfall, attach lift bags to it and winch it out on to a pontoon, and then onto land.
Programme delivery manager Dave Kennerley said: “The outfall was a crucial part of a wider programme of work that would support the projected population growth of Auckland’s south-west which is expected to grow to around 30,000 people by 2050.Initially, it will carry highly treated wastewater from the Clarks Beach Wastewater Treatment Plant, which we’re currently upgrading. But it has been designed and sized to support future population growth in the wider area.”
