Knox City Council has warned visitors to Ferntree Gully Quarry Reserve Lake after routine water testing detected E. coli and Enterococci bacteria at levels that could pose a risk to human and animal health.
Signage is being erected around the lake warning visitors not to swim, fish, or let their dogs enter the water effective Thursday, 6 November 2025 until further notice.
E. coli and Enterococci are bacterium commonly found in the gut of humans and warm-blooded animals. Its presence indicates faecal contamination from sources such as stormwater runoff, sewage, dog poo, or wildlife waste.
Most types of E. coli and Enterococci are not considered harmful to humans and animals and are commonly found in natural water bodies, especially after heavy rainfall or increased wildlife activity.
These environmental factors mean that the presence of these bacteria cannot be entirely prevented. However, it is important to take precautions when levels exceed safe thresholds.
Their presence may indicate other disease-causing organisms such as viruses and protozoa, which can make swimmers or people who consume fish from the water sick.
If you experience any symptoms including diarrhoea, abdominal pain, cramps, fever, respiratory infections, ear infections, or skin rashes after swimming in or eating fish from the lake, please seek medical attention.
“We will continue to monitor the water quality, testing weekly until mid-April and will update the community when it returns to safe levels,” the statement reads.
For more information, see Knox City Council’s website or contact its Stormwater team on 9298 8000.
