Alkimos Desalination Trunk Main Design

As part of WA’s transition toward a climate-resilient water supply, a 33.5km desalination trunk main is being delivered from the Alkimos Desalination Plant to service the northern metropolitan corridor of Perth.

A key section of this infrastructure is a 1.26km DN1400 link through Alkimos Central – a 200-hectare, masterplanned town centre delivered by DevelopmentWA. Designed around transit-oriented principles and anchored by Alkimos Train Station, the precinct integrates residential, commercial, business and industrial uses within a highly coordinated urban framework.

The pipeline link is to be installed within the future NS02 corridor, a north–south distributor road through Alkimos Central, slated for construction in the coming years.

Cossill & Webley, as DevelopmentWA’s civil engineers for Alkimos Central, brought deep precinct knowledge to the project- having previously led the design and delivery of early stages around the station, including major infrastructure such as a DN1500 sewer beneath the adjacent Yanchep Rail Extension corridor. That track record of large-format precinct design across Alkimos Central and its key infrastructure, was critical to ensuring the new 1.26km desalination link properly accounts for future NS02 services and road construction.

For this project, Cossill & Webley developed a preliminary engineering design that coordinates the DN1400 desalination pipeline with multiple future services, including a DN1500 sewer extension, DN900 distribution water main and DN900 transfer mains. The design also future proofs the vertical designs for either signalised or roundabout intersections at NS02, preserving DevelopmentWA’s options as the road network evolves.

The result is a forward-thinking, integrated design that aligns major water infrastructure with long-term urban development, ensuring efficient delivery without compromising future precinct outcomes.