A giant desalination plant in Perth’s northern suburbs is in the mix to be the city’s next major drinking water source, with the Water Corporation set to undertake preparatory works.

The State-owned utility has revealed it is about to carry out a seismic survey of the seabed off Alkimos to identify potential issues or risks associated with building a desalination plant there.

Testing will begin on September 17 and last for three weeks, before a drilling barge is used for “core sampling” until November.

The Water Corp said an exclusion zone up to 5.5km offshore would be set up around the affected area, although it stressed that the work would be non-invasive.

The move presages the likely building of a desal plant in the northern Perth suburb at a cost of more than $1 billion within the next five to 10 years.

While the Water Corp has not committed to a timeframe for building the facility, Alkimos has long been earmarked for one to service Perth’s rapidly expanding northern fringe.

To date, the area has been supplied using mostly groundwater from the Gnangara aquifer system, with the city’s dams and two existing desal plants located to the south.

However, amid pressure on Perth’s groundwater resources because of falling rainfall and increasing demand, the Water Corp believes a “climate-independent” source may be needed in the northern suburbs.

The announcement the Water Corp is poised to conduct seismic testing is the strongest indication yet that the utility will select Alkimos for its next major upgrade of the supply scheme.

Water Corp spokeswoman Clare Lugar said no decision had been taken on the timing of a desal plant at Alkimos, while noting the utility was also investigating whether to build a second such plant at Kwinana “as well as other climate-independent sources”.

Ms Lugar also noted that any desal plant at Alkimos would be built next to the corporation’s existing wastewater treatment facilities. “The work will provide information about the sea floor and geology beneath the seabed, which will inform safety, environmental and construction considerations for offshore components of the possible new desalination plant,” Ms Lugar said.

“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.”