Design change for Eyre Peninsula desalination plant

SA Water has made changes to the design for its proposed desalination plant at Billy Lights Point in response to feedback and scientific analysis.

The utility said it reworked the design to reflect its commitment to minimising impacts to the coastal and marine environment following early engagement and analysis.

The proposal involves building a small-scale plant designed to provide long-term water security for the people of the Eyre Peninsula and ensure the ongoing health of the Uley South Basin, which provides the majority of the region’s drinking water.

The design changes include using a trenchless construction method for the installation of the plant’s intake and outfall pipes (where seawater will be drawn in and concentrated seawater will be dispersed), and the placement of these pipes in a deeper area off the coast of Billy Lights Point within a higher flushing zone.

SA Water Senior Manager of Capital Delivery, Peter Seltsikas, said the work forms part of a comprehensive process with early contract involvement partner ACCIONA.

“We have listened to and responded to feedback from the Project Reference Group and other key community groups, our regulators and various other government agencies, which highlighted the importance of minimising disturbance to the Billy Lights Point coastline and avoiding the shallow waters of Proper Bay,” Mr Seltsikas said.

“We will need to conduct additional geotechnical studies to refine the scope of the trenchless construction method, and from early next month, we will use a barge and small drill rig off the coast of our existing nearby wastewater treatment plant to collect soil and rock samples from the ocean floor.

“This will enable a better understanding of the site’s geology, to determine the exact type of construction method, which could include directional drilling or tunnelling.”

The geotechnical work is expected to take several weeks to complete. SA Water said the results will help inform a detailed concept design, which will be incorporated into its development application for the project, to be lodged with the State Commission Assessment Panel in early 2024.

“The Uley South Basin is the primary source of drinking water for Port Lincoln and the lower Eyre Peninsula, but the Basin is under stress so a desalination plant is essential to augment supply,” Mr Seltsikas said.

“A combination of long-term lower groundwater recharging of the Basin and ongoing extraction rates to meet community demand means the aquifer’s water levels are likely to reach historically low levels by the mid-2020s.

“We need to build the desalination plant at Billy Lights Point to protect the health of the Basin and provide an alternative climate-independent water source to deliver drinking water to the local community.”

SA Water said it will also be undertaking further hydrodynamic modelling within the preferred marine zone and a re-run of the particle tracking model to support the geotechnical studies, which will add to existing knowledge of mussel spat movement and narrow down the exact alignment and location of the intake and outfall pipes.

“We are planning to place the pipes in a zone to the east of Billy Lights Point, up to 1.5km offshore and more than 2.5km from existing mussel leases,” Mr Seltsikas said.

“This location is near a commercial shipping corridor which extends from the marina to Cape Donnington, and is within water around ten to 15m deep.

“The outfall for our Port Lincoln Wastewater Treatment Plant sits outside of this zone further to the south, and our extensive monitoring to date has demonstrated no negative impact to the local marine environment from this marine infrastructure.”

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