Major milestone ticked off on $300+ million programme to improve wastewater services in Warkworth, Snells Beach and Algies Bay

On Sunday 10 November, Piper – a tunnel-boring machine – completed the final leg of her journey to install a five-kilometre-long pipeline to transport wastewater from Warkworth to the Snells Beach Wastewater Treatment Plant.

The new pipeline is part of a broader programme of work to improve the performance of the local wastewater network and support growth in Warkworth, Snells Beach and Algies Bay.

We are investing over $300 million, which includes building a state-of-the-art wastewater treatment plant at Snells Beach.

Photo: The Snells Beach Wastewater Treatment Plant is on track to come into service mid to late 2025.

Project manager Dirk Du Plessis says the pipeline was tunnelled in three stages, with the last stage being the shortest and easiest for Piper to complete.

“On her final leg, Piper went headfirst, mostly downhill, to tunnel through consistent but hard ground. Unlike the other two legs, her third leg had no curves on it – making things a bit easier and faster. Throughout her journey, Piper used her face to devour a smorgasbord of various soft and hard ground that were transported out of the tunnel and separated from the water at a dedicated separation plant at the launchpad.

Photo: Piper breaks through.

“At the separation plant, the ground material is separated and water is pumped back to Piper to transport much-needed bentonite for lubrication and for pumping tailings back to the surface. Since September of last year, Piper has been installing the pipeline at a rate of about 36 meters per day.”

Senior project engineer AJ Jaafar says despite Piper breaking down twice on her 14-month journey, the installation of the pipeline has gone rather smoothly.

“Between each leg, a dedicated McConnell Dowell crew would spend two to three months getting her ready to go.

“During this time, the crew would give her a good pampering: washing and checking her hydraulics, motors, and navigation systems, as well as replacing worn-out seals and mechanical parts or broken equipment damaged from her last leg.

“Plus, it also gave the crew time to set up the equipment at each new launch site and do final checks and balances before starting each leg.

“Once she’s tunnelling up to 50 metres underground, it’s almost impossible to get her out for repairs without causing damage and delays to the project.

Jaafar says once Piper completes this final leg, she will undergo a full maintenance check.

“After Piper gets a clean bill of health, she will move onto her next job with her own dedicated drive crew. Our next major milestone for the project is to backfill the drive sites and to connect the pipeline into the Lucy Moore Wastewater Pump Station and Snells Beach Wastewater Treatment Plant.

“After that, this pipeline will be brought into service at the same time as the pump station and treatment plant, which is scheduled to be in service by mid to late 2025.”