Bayside Council has made a written submission strongly opposing the request by Sydney Water to periodically discharge waste water into Mill Stream at Mascot which flows into Botany Bay.
Bayside Council mayor Joe Awada described the move as unhealthy for the community and detrimental to the local environment.
The council is also objecting to the inadequate 14 day time frame the council and the community were given to respond to the impact of the proposal.
"This use of this waterway as sewage overflow cannot continue," Bayside Council mayor Joe Awada said.
"It is unacceptable that residents are prevented from using a beach because Sydney Water has not implemented measures to stop the sewage overflows.
"Mill Stream also plays an important role linking the significant waterways of Botany Bay and the Botany Wetlands.
"The regular discharge of sewage in such an environmentally sensitive is not appropriate in this day and age.
"It is unhealthy for our community and detrimental to the environment of this important area."
Mill Stream flows directly into Botany Bay, a key recreational swimming area of the Sydney region bordered predominantly by the heritage listed Cook Park.
Foreshore Beach is already impacted from sewage overflows discharging to nearby Mill Stream and continues to be graded as very poor in the State Government's annual beach report.
The overflow point is directly upstream to Foreshore Beach, the only local beachfront for residents in the eastern side of the Bayside LGA.
Botany Bay is an important recreational fishing area and Council is concerned about the long term impacts on human health if people are eating fish from a waterway which is impacted by regular sewage overflows.
Botany Bay also has significant environmental value as habitat for threatened and migratory birds, fish habitat, threatened sea grass as well as many different species of animals and plants.
Mill Stream plays an important role in annual migration of long finned eels from Centennial Park Sydney to New Caledonia to breed. These eels travel 2,000 kilometres to return to their place of birth, including swimming through Mill Stream.
In 2018 millions of litres of untreated sewage flowed into Botany Bay, creating a risk to those exposed to the effluent.
Bayside Council has identified Mill Stream and Botany Wetlands as important community assets with significant potential to meet the increased community recreational needs. Continual sewage overflows will significantly restrict the usability of this area.
