A child's bowel movement in a swimming pool that led to a pump failure and sent chlorine into a nearby creek has cost Lake Macquarie council $15,000.
The NSW Environment Protection Authority issued the fine after the West Wallsend Swim Centre discharged 16,000 litres of chlorinated water into the creek next door in April.
A council spokeswoman said the backwash was intended to treat a faecal contamination after "a child who was not toilet-trained used the pool without a correctly fitted aqua nappy".
Swim centre staff followed a "rigorous procedure" of evacuating the pool, chemically treating the water and back-washing the filtration equipment to remove pathogens, the council said, in line with NSW Health guidelines.
A Fire and Rescue HAZMAT crew also attended.
"Council was aware that the pump was not operating properly, but decided not to take action to fix it as it was seen as a low priority. The pump subsequently failed and caused the discharge," Karen Marler, the EPA's Hunter director, said.
"The EPA recognises the pollution discharge was not intentional, however it was the result of council's failure to maintain its pumping equipment."
Ms Marler added that the council had been "swift to respond to the incident and ensure appropriate clean up and restoration of the creek and has now replaced the faulty pumping equipment".
The council has carried out an investigation into the chlorine discharge alongside the investigation of the EPA.
"No observable damage to the creek occurred, as council's clean-up response was immediate and involved removing chlorinated water from the creek into a wastewater tanker truck at a nearby weir," a council spokeswoman said.