Sydney Water has copped a $30,000 fine after untreated sewage overflowed into two creeks at Bangor.
The NSW Environment Protection Authority (EPA) has handed down the penalty.
It came after 67,000 litres of sewage was discharged into Still Creek and another creek in the Woronora Catchment on September 14, last year.
The incident was investigated as part of an EPA compliance campaign during May to September 2018 to assess the adequacy of Sydney Water's responses to dry weather sewage overflows from its sewerage systems.
The two alleged breaches included one for Sydney Water's inadequate response to the overflow, and the other, for failure to comply with the clean-up notice issued by the EPA.
The creeks affected by the incident were the same as those affected by sewage overflows at Bangor in January 2018, for which the EPA issued three penalty notices.
In March this year the EPA also added special conditions to each of Sydney Water's 23 sewage treatment system environment protection licences, requiring an independent assessment of Sydney Water's overarching management and operational framework for responding to dry weather sewage overflows.
EPA Regional Director Metropolitan Giselle Howard says untreated sewage can pose a risk to human health and have significant environmental impacts on waterways and land.
"It is essential Sydney Water undertakes all necessary actions as soon as possible in response to a sewage overflow to minimise the impacts on the environment and public health," she said.
"The campaign identified significant issues with Sydney Water's performance, particularly in relation to the timeliness and adequacy of clean-up of impacted waterways.
"The sewage overflows assessed were from across the network and subsequently reached environmentally sensitive areas such as local creeks. The overflows occurred under normal operating conditions, such as blockages."
Secretary of Georges River Environmental Alliance, Sharyn Cullis, says while the penatly is a positive move, more needs to be done to protect the environment with active measures.
"It's fantastic they've been fined," she said. "I go walking sometimes along the fire trail, and Still Creek is beautiful in a lovely spot of bushland.
"A sewer line runs alongside it and they've been doing work there for over 12 months. I have contacted the EPA a number of times about it.
"My concern is that although the EPA is finally catching up with Sydney Water about something walkers already know and have frustrations about, it's water consumers who end up paying.
"Sydney Water make massive profits and aren't putting that back into infrastructure in places that are community assets. It seems to be out of sight and out of mind. I hardly ever see people walking there, and you can have an overflow and it can go unnoticed. In dry weather, you get concentrated sewage that hasn't been diluted with rain water."