Liverpool to Ashfield Pipeline

Leighton Contractors Pty Ltd commissioned GHD as its design consultant for the design and construction of a 24km-long pipeline between Liverpool and Ashfield and other related sewer works.  Sydney Water awarded the AUD$131 million contract to Leighton in July 2006.

The Liverpool to Ashfield Pipeline (LAP) is 1050mm in diameter and runs from the Liverpool Sewage Treatment Plant to the Western Branch Main Sewer at Ashfield. The idea was to transfer wastewater flows from the Liverpool STP and the Fairfield SSTP while the Northern Georges River Submain (NGRS) is rehabilitated.  The pipeline has been constructed by open cut trenching, under boring and slip lining inside a disused 1225mm water main.

At Ashfield a vortex drop structure has been designed to transfer the flow from the end of the LAP to the Western Branch Main Sewer located approximately 25m below ground. This drop structure has been designed to fit within the footprint of a proposed local Roads and Traffic Authority development and a proposed park in the area. 

In addition to the pipeline, eight new sewage sites have been designed, including two new pumping stations and a range of associated infrastructure. The scheme has complex operational requirements – it has been designed to cater for the flows required in order to rehabilitate the NGRS and to be used to transfer secondary treated effluent to customers after 2010. The control and monitoring systems have been designed to suit these operational requirements. This included the development of a control strategy for automatic adjustment of the pumps speed at the new pumping stations in accordance with the required flow, the hydraulic constraints of the pipeline and in coordination with the positioning of the Ashfield pressure control valve.

Consideration also had to be given to the delineation of the assets for the purpose of control, operation and maintenance.  Control and monitoring is shared between the treatment plant SCADA systems and the Sydney Water IICATS telemetry system.

This is the largest sewerage rising main of its type in Sydney and a first for Sydney Water. Construction commenced in late 2006, commissioning of the LAP controls started in April 2008, and the system is operational and was transferred to Sydney Water in July 2008.