The last spill in the area was in February. Local residents attending a Clean Up Australia Day event weeks later raised concerns about potential pollution from raw sewage.
A Sydney Water spokesman said samples had been taken in the area and the overflow had been significantly diluted, meaning no effluent was detected.
“Spillovers from emergency relief structures are permissible under our EPA [Environmental Protection Agency] “Permit-requiring and necessary to protect homes and businesses from sewage surcharge that could enter their properties,” they said.
“In wet weather, excess water can enter the network and result in a severely diluted overflow.
“Sydney Water began cleaning up the site and upon completion samples were taken and no effluent was found.”
Neil Saintilan, a professor of environmental sciences at Macquarie University whose research focuses on wetland responses to climate change, said Sydney Water needs to make the composition of the runoff and the amounts discharged public.
“The pattern of the dieback is directly related to the channel of the creek through which the pollution would have flowed,” he said, adding that he inspected the mangroves at Oatley and saw no other explanation for the dieback (eg. Insects). infestation).
Kim Wagstaff, president of the Oatley Flora and Fauna Conservation Group, said it’s important that an investigation determine whether mangroves are vulnerable to anything that leaks from the emergency overflow system.
On the opposite side of town, recent flooding has caused a mass die-off of the mangroves in upper Hawkesbury.
However, Saintilan, who has been conducting field research at Hawkesbury, said the damage there was caused by a thick layer of sentiment that completely covered the mangroves’ breathing roots: thereby virtually suffocating the mangroves, which are used to regularly being outdoors at low tide be .
“I have seen no evidence of a similar impact at Lime Kiln Bay,” he said. “I think there is good reason to link the extinction to the pollution event and a full investigation by either the EPA or the Department of Planning and Environment would be warranted.”
A spokesman for Environment Secretary Penny Sharpe referred questions to the EPA, which confirmed Sydney Water had reported three wet weather sewage spills in February because its emergency relief structure was “activated as planned.”
“We are not aware of any direct impact on mangrove health and will be working with Georges River Council to address any concerns,” the spokesman said.
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