Legislative Council: Thursday, March 09, 2023


Eyre Peninsula Desalination Project

The Hon. N.J. CENTOFANTI (Leader of the Opposition) (14:32): I seek leave to provide a brief explanation before asking a question of the Minister for Primary Industries regarding the government's announcement of Billy Lights Point as a preferred location for the EP desal plant.

Leave granted.

The Hon. N.J. CENTOFANTI: According to a letter from Eyre Peninsula Seafoods, they were so concerned about the impact of a desalination plant at Billy Lights Point on their business that, and I quote:

…we commissioned a study by Professor Paul McShane, a marine biologist, research manager, and educator with over 30 years of international experience, which raises significant concerns about establishing the proposed desalination plant in Boston or Proper Bay. In his study, McShane found that the biophysical model developed by SARDI Aquatic Sciences was inadequate in characterising the risk of entrainment of mussel larvae in seawater intakes. As a result, 'the magnitude of entrainment relative to source populations remains to be adequately predicted'.

McShane's findings led him to conclude that Boston and Proper bays be excluded from consideration for the desalination plant 'given potential harm to existing and valuable mussel aquaculture enterprises'. My question to the minister is: has she contacted Eyre Peninsula Seafoods to discuss the results of this study? And if not, why not?

The Hon. C.M. SCRIVEN (Minister for Primary Industries and Regional Development, Minister for Forest Industries) (14:33): I thank the honourable member for her question. I am advised that comparison of the hydrodynamic model with moored field measurements was made over a one-year period, and it showed that the model was able to reproduce tidal and lower frequency weather band and seasonal variations in currents, sea level, temperature and salinity.

I am advised that the model therefore demonstrated predictive capability for assessing the transport, dispersal and fate of brine discharges and planktonic larvae associated with the operation of the proposed desalination plant. I am advised that using a five-year model hindcast, far field predictions of the salinity differences, that is, the anomalies, between a 12 gigalitre per year desalination plant operating at full capacity and a model simulation with no desalination, showed a maximum seasonally average salinity anomaly of 0.44 PSU within 250 to 500 metres of out force.

This anomaly, I am advised, is equivalent to a 1.2 per cent change in the ambient salinity. Maximum seasonally adjusted average anomalies were reduced to one kilometre from outfalls. At hourly timescales, predicted far field increases in salinity at distances of approximately 300 metres from outfalls were always one kilometre from outfalls.

I am advised the predicted changes in salinity due to desalination discharges are within the natural salinity variability of the region determined from the measured data. Salinity observations showed an annual range of 1.46 PSU, equivalent to a 4 per cent change in ambient salinity, and variations of approximately 0.1 and approximately 0.5 PSU across timescales of several hours to a week respectively.

Doubell, M. and James, C. 2023, 'Oceanographic far-field modelling to inform desalination in Boston Bay' was the comparison of the brine dispersal patterns from the different outfall locations and demonstrated the spatial extent and magnitude of long-term salinity increases were reduced when outfalls were in offshore waters east of Boston Island.

I am advised that for all outfall locations, salinity increases predicted at distances greater than 250 metres from outfalls, associated with a 12 gigalitre per year plant, modelled in this study were below the less than 5 per cent change in ambient salinity recommended by the Australian and New Zealand guidelines for fresh and marine waters and the one PSU environmental and ecological tolerance limits for flora and fauna reported in the desalination literature.

I am advised that this suggests, given the small size of the proposed plant which is eight gigalitres per year maximum, there are unlikely to be any substantial environmental impacts from the brine discharges in the far field. However, to adequately minimise salinity increases, it will be important that sufficient dilution is achieved by appropriate diffuser designs in the near field.

I am advised that biophysical modelling results for planktonic larvae, based on a limited understanding of the spawning characteristics of blue mussels, showed the far field spatial connectivity assimilated passive larvae with intakes were strongly influenced by tides and the regional circulation patterns.

I am advised that this identified that mussels sourced from Proper Bay and the Boston Bay area inshore from Boston Island have increased connectivity with intakes located near Billy Lights Point and reduced connectivity with the intake located near Point Boston. Similarly, mussels sourced from Louth and Peake bays had increased connectivity with the intake located near Point Boston and reduced connectivity with intakes located near Billy Lights Point.

For all intake locations, the far field connectivity modelling indicated that less than 0.1 per cent of the particles released over the course of the mussel spawning season may be at risk of coming within a 25-metre radius of intakes. I am advised that further validation and development of the biophysical model, including in situ sampling to understand larval source regions and concentrations and the vertical distribution of mussel larvae, is needed to improve the far field connectivity modelling to better inform the number of larvae possibly removed by desalination intakes.

The modelling results, I am advised, that are presented in this study of the potential far field increases in salinity due to desalination brine outfalls and larval entrainment by intakes, should be considered in the context of current and future cumulative environmental impacts in the Port Lincoln region which, as we know, is home to South Australia's most valuable and productive aquaculture zone.