Sydney Water has been fined $15,000 over the discharge of five million litres of raw sewage into a south Sydney bay.

The fine was issued by the NSW Environmental Protection Agency after a power outage caused a Cronulla sewage pumping plant to discharge the sewage into Woolooware Bay on August 14 2015, affecting local oyster leases.

“The EPA is concerned by Sydney Water’s slow response to the incident. Despite advanced warning that an overflow was likely, Sydney Water staff were not on site until nearly four hours after the incident started,” EPA acting director metropolitan Greg Sheehy said.