Hydronumerics was commissioned to assess the likely impacts on human and riverine health resulting from wet weather sewage discharges from the Emergency Relief Structure (ERS) at Brimbank Park. The three-dimensional hydrodynamic model ELCOM (Estuaries, Lake and Coastal Ocean Model) was applied to a discrete section of the Maribyrnong River (Victoria) downstream of Brimbank Park ERS.

The model was used to assess the transport and fate of ERS discharge in the river, to compare the composition of ERS discharge against inflows from Maribyrnong River and Taylors Creek, and to assess the percentage composition of ERS discharge into major recreational areas downstream of Canning St Ford. Under baseline conditions, modelling shows that the river can achieve a 1:1100 natural dilution of ERS discharge, suggesting that there is some buffer to public health impacts afforded by the natural riverine inflows. A series of catchment-wetness and riverine flow scenarios were also examined to determine the river health under worst case scenario.