The security of Adelaide’s water supply had become an issue of critical significance in South Australia due to severe droughts and the anticipated effects 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. 

Supplying Adelaide with desalinated drinking water

The Transfer Pipeline System (TPS), a separately contracted sub-project of the Adelaide Desalination Project, links the desalination plant to the Happy Valley Water Treatment Plant (HVWTP), where drinkable water will be delivered into Adelaide’s existing water supply network.  

The TPS has been designed to handle 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 variable flow requirements. It is a single lift pump station, with a static lift of 140m and the total lift at full flow approximately 185m. 

Piping water across sensitive areas

The length of pipeline from the TPS pump station to the HVWTP is approximately 12km, and it 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 the desalinated water with traditionally treated reservoir water.

Designing a pump station for future ease of maintenance

The pump station is located on a narrow sloping site. The layout of the area demanded first and foremost a safe design. We put considerable effort into developing safe access and egress routes from the 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. This novel solution created design challenges due to a larger pump station footprint, but these were overcome for the long term benefit of stakeholders. 

The horizontal pump-motor configuration allowed the roofline of the pump station to be lower than the reference design, providing an aesthetic benefit to this prominent site along the Adelaide coastline as well as sustainable benefits associated with the savings in steel and concrete.

The pump station site
The construction site of the pump station

Piping water over water at the 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, with two 250t and 300t cranes performing a tandem lift to manoeuvre the pipe into its final location.

Compared to the original box truss reference design, this solution reduced steel usage and coating area by approximately 40%, contributing to the sustainability of the project. By installing an aesthetically pleasing pipe bridge we demonstrated that visible water engineering structures can be functional without creating a major visual intrusion.

Using fundamental physics to design innovative pipeline thrust restraints

The transfer pipeline is generally connected with rubber ring joints, with welded sections at bends. During the design process it became clear that the size, pressure and jointing regime of the proposed pipeline exceeded the scope of existing design theory and industry practice. To remedy the situation, we went back to the classroom.

Our team developed an analysis technique which focused on soil/pipe interactions at 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 design thrust restraints that were 20-50% smaller than conventional methods. Our innovative method used limit state principles for subjected loads, leading to a design solution that is efficient, compact, and consistent with Australian Design Codes.

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