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The security of Adelaide’s water supply had become an issue of critical significance in South Australia due to severe droughts and the anticipated effect of climate change. The AU$1.824bn Adelaide Desalination Project (ADP) provided a climate independent water source capable of supplying 50% of Adelaide’s annual water requirements.
The Transfer Pipeline System (TPS), which is a separately contracted sub-project of the Adelaide Desalination Project, provides the link to transfer drinking water from the desalination plant to the Happy Valley Water Treatment Plant (HVWTP), where the water will be delivered into Adelaide’s existing water supply network.
The TPS has been designed to transfer flow rates of between 30 and 375 megalitres (ML) per day. The TPS pump station consists of 8 transfer pumps with pump selection based on flow requirements. It is a single lift pump station, with the static lift being 140m, the total lift at full flow is approximately 185m.
Project Summary
$1.824bn Adelaide Desalination Project
50%of Adelaide's annual water requirements supplied
12kmlong pipeline
The total length of the pipeline installed from the TPS pump station to the HVWTP is approximately 12km and passes through metropolitan and conservation park areas close to houses and sensitive environmental areas. The mild steel cement lined pipe has an internal diameter of 1.515m and a pressure rating of 25 bar.
The pipe crosses over the Field River at a steep rocky gully and is designed to support its own weight without a separate bridge structure.
The main pipeline flows into a 9ML, 44m diameter, 6m high concrete tank. This is subsequently connected to the HVWTP at three locations plus the reservoir providing operational flexibility and the ability to blend desalinated water with traditionally treated reservoir water.
Pump Station
The pump station is located on a narrow sloping site. The layout achieved, first and foremost, a safe design. Considerable effort went into elements such as developing safe access and egress routes from a steep access road, and in selecting equipment to make future maintenance safer.
One example was the selection of horizontal spindle pumps that reduced the complexity and lift height required for future disassembly and maintenance but created design challenges due to a larger pump station footprint. However these design challenges were overcome for the long term benefit of stakeholders.
The horizontal pump-motor configuration allowed the roofline of the whole pump station to be lower than the reference design. This provided an aesthetic benefit to this prominent site along the Adelaide coastline as well as sustainable benefits associated with the savings in steel and concrete.
Field River pipe bridge
The Field River pipe bridge is a self-supporting pipe that spans the Field River. The superstructure was delivered in three segments to a nearby yard for assembly into one 66m segment before being marshalled by road to site. A 250t and a 300t crane performed a tandem lift manoeuvring the pipe into its final location.
Compared to the box truss reference design, this solution reduced steel usage and coating area by approximately 40%, contributing to the sustainability objectives of the project. The aesthetically pleasing pipe bridge demonstrates visible water engineering structures can be functional without creating a major visual intrusion.
Pipeline thrust restraint
The transfer pipeline is generally connected with rubber ring joints with welded sections at bends. During the pipeline design process it became apparent that the size, pressure and jointing regime of the proposed pipeline exceeded the scope of existing design theory and industry practice.
Arup developed an analysis technique which focused closely on the soil-pipe interaction near bends and how this affected the behaviour of the pipeline. The methodology was developed from fundamental principles and allowed the use of structural analysis software to model the pipe and subsequently design thrust restraints that were 20-50% smaller than conventional methods. The method uses limit state principles and is consistent with Australian Design Codes.
