Marine Utilities

Alkimos completes intake tunnel as offshore acceptance continues

Published 13 July 2026 Updated 15 July 2026 Editorial responsibility IMWO Region Asia Pacific Confidence Confirmed
Water Corporation cross-section showing Alkimos seawater intake and brine outfall structures connected to separate tunnels beneath the seabed

Water Corporation, Western Australia

Alkimos has completed its 2.5 km intake tunnel and all offshore piling, but the 4 km outfall drive and 130 m diffuser remained active after the original June 2026 marine-construction window. Permanent connection and accepted system testing are still needed before the marine interface can be called complete.

What changed

EPA records environmental approval on 10 August 2023, Jacobs identifies the alliance appointment on 19 April 2024, and the alliance sustainability report separates construction from later tunnelling, marine construction, commissioning and operation. Water Corporation's 15 July 2025 release records both TBMs assembled for separate 2.5 km intake and 4 km outfall drives. Transport WA's 9 December notices establish the two offshore work zones from 10 December 2025. The Western Australian Government records Beverley's 16 March 2026 marine mobilisation. Water Corporation's June panel says the intake TBM reached its destination, the outfall drive was about 80% complete and all offshore piling was complete; its July panel still had outfall-diffuser installation active. Those owner panels publish month precision only, so the dates remain at month precision rather than being assigned an unsupported day. The annual schedule's June 2026 marine endpoint and July 2026 tunnelling endpoint were programme points, not acceptance evidence.

Why it matters

A desalination project can appear advanced onshore while its first-water date remains exposed to a small number of offshore connections. Alkimos's annual programme placed marine construction through June 2026, yet the owner's July panel still had diffuser installation active. The two intake structures, 130 m diffuser, four vertical risers, 2.5 km intake tunnel and 4 km outfall tunnel must meet within survey, environmental and mechanical tolerances before integrated testing can begin.

Decision read

What remains open

The offshore campaign is nearing its physical finish, but the owner's July panel shows that the original June marine-construction point was not completion or acceptance. Diffuser installation and the outfall drive still have to meet precisely at the risers before permanent connections and marine-system testing can begin. Marine works can then converge with plant, power and transfer-pipeline commissioning. Finished piling, closed work zones and a complete intake drive do not settle those interfaces.

Next watchpoints

  • Completion and survey acceptance of the 130 m outfall diffuser
  • Outfall TBM advance, breakthrough, and marine-riser connection after the original July 2026 programme point
  • Permanent connections to both offshore intake structures
  • Underwater-noise, fauna-observation, water-quality, and seabed controls
  • Integrated testing path to first water in 2028

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