Senior Environmental Health Officer, Myfanwy Appleton said a council water and sewer crew were the first to identify a sewage spill on a routine drive-by in Merimbula around midday on Wednesday, August 5.
The sewage had overflowed into a stormwater drain and tracked down to the lake on the eastern side of Spencer Park.
Ms Appleton said the crew had moved quickly to affix bunding to the end of the drain to stop the flow and organised for a pump truck to suck up the spill while getting to work to remove material, disinfect, and cover the area ahead of forecast rain.
Local oyster farmers were notified of this spill as a priority.
"This is a further reminder that water quality for the oyster industry is critical and that we all have a role to play in ensuring that our waterways are kept pristine," Ms Appleton said.
Council recommends people take a precautionary approach and avoid swimming in the lake until after the weekend as recreational water quality may be affected given this incident and the predicted rain. Signage is in place at Spencer Park, Bar Beach, and Mitchies Jetty.
Water and sewer manager, Chris Best said having a built-up area on a lake, as is the case in Merimbula, means there is always the potential for a spill.
"The work we do is about minimising that risk and limiting any impacts for the environment and for businesses, such as oyster farmers, who operate on our lakes and estuaries."
Mr Best said council has a comprehensive process for proactively identifying and clearing blockages and a good track record for managing spills on Merimbula Lake; a high-risk location.
"We have a CCTV crew of two that travels throughout the shire each year detecting and clearing blockages." Mr Best said.
"We also work through a planned renewal program across our sewer pipe network to ensure pipes are upgraded and kept in good condition to prevent blockages."