Offshore survey to start for potential seawater desalination plant in Alkimos

A map of the testing area off Alkimos.
A map of the testing area off Alkimos.

EARLY investigations for a possible seawater desalination plant in Alkimos will start next week with an offshore survey.

Water Corporation spokeswoman Clare Lugar said the survey was part of ongoing feasibility studies into a possible seawater desalination plant in the area, which may be a future water source for Perth.

“If constructed, the seawater desalination plant would form part of the metropolitan area’s Integrated Water Supply Scheme and predominantly service the city’s growing northern corridor,” she said.

“The Perth metropolitan area already has two operating desalination plants – at Kwinana and Binningup – which together supply 48 per cent of Perth’s fresh water needs.

“An Alkimos desalination plant would be located next to existing wastewater treatment infrastructure, within the Alkimos Water Precinct.

“No decision has been taken at this time to proceed with construction or when a new water source may be needed for Perth.”

The Alkimos testing will start about September 17 and continue to November, with three weeks of seismic testing initially followed by core-sampling of the seabed utilising a drilling barge that may be visible from the coast.

“The seismic testing will involve an exclusion area being off-limits to vessels and equipment to prevent entanglement,” Ms Lugar said.

“The seismic testing, which is non-invasive, involves collecting data from the seabed and subsurface geology through releasing pulses or sound waves.

“Once complete it will be followed by five weeks of core-sampling which will involve drilling small holes into the seabed and extracting samples for analysis.

“During this second stage, the exclusion zone will be smaller, extending 25m around the barge and clearly marked by four flashing yellow buoys.”

Ms Lugar said the surveys would provide information about the seafloor and geology beneath the seabed, which would inform safety, environmental and construction considerations for the possible desalination plant.

The testing will be in waters directly off Alkimos between Alkimos Reef and Eglinton Rocks, extending out about 5.5km from the coast.

“A notice to mariners will be issued with full details for vessel owners and operators,” Ms Lugar said.

“The public will retain access at all times to Alkimos Beach for fishing and swimming and it will be safe to dive at the nearby Alkimos and Eglinton wrecks during the work.

“The work will continue seven days a week depending upon weather and is expected to be completed by mid-November.

“Boaters are asked to remove all fishing equipment from the area by no later than September 16 and adhere to the exclusion zones or avoid the area where possible.”

A possible second desalination plant for Kwinana is also being investigated, as well as other climate-independent sources.

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