Precinct Intertidal Zone Study and Water Quality Assessment
BlueSphere was engaged to design and implement an intertidal discharge study encompassing four representative sites across the Port of Melbourne precinct. The objectives were to characterise the intertidal zone hydrodynamics and water quality in these areas and how they relate to upgradient groundwater and ambient surface water conditions in the Yarra and Maribyrnong Rivers.
A variety of hydraulic and geochemical methods were employed in the investigation, including the installation of multilevel intertidal piezometers, seepage meters, the collection of hydraulic head time series, analysis of the key contaminants of concern and the analysis of geochemical tracers, including chloride and oxygen/deuterium isotope ratios.
The study demonstrated complex tidal interactions, background water quality issues and ultimately facilitated the production of rationalised water quality objectives for much of the upgradient portions of the Port area. The study demonstrated that terrestrial groundwater represents only a small fraction of the pore water discharge to surface water (generally <20%) and that pore water discharge from the intertidal zone comprises a very small component of the water balance of the lower Yarra and Maribyrnong Rivers (<<<1%).
Benefits to Client
- Resulted in substantial rationalisation of water quality objectives for much of the upgradient portions of the Port, avoiding unnecessary investigation and/or remediation.
- Demonstrated that upgradient groundwater quality exceeding the surface water beneficial uses criteria represents a low risk of harm.