A deluge of rain on the weekend turned several Illawarra waterways into a sludgy mess and forced the closure of beaches, with authorities looking into the cause.
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On Saturday, the region recorded the state's heaviest falls, with 63mm falling at Bellambi in five hours - resulting in pollutants to flow down stream and into the ocean (which is not uncommon).
However, black sludgy water could be seen flowing along Bellambi Gully Creek and exiting at Bellambi Beach, while Collins Creek at Woonona was running like a river with what some residents believed to be coal run-off.
Surf Life Saving Illawarra chose to close a number of Illawarra beaches due to the pollution, while Beachwatch data (on the NSW Office of Environment and Heritage website) listed nearly all beaches as likely to be contaminated and not suitable for swimming.
John Rosenzweig swims at Woonona beach daily, often spending hours after a storm helping pick up rubbish that ends up on the beach.
He told the Mercury it wasn't unusual for rubbish "within a stone's throw" of the local creeks to be washed down during a storm, but said he'd never seen Collins Creek flow so rapidly before.
"Surfers were trying to come down and across ... but you couldn't walk through it was that strong," Mr Rosenzweig said.
Mr Rosenzweig took video and photos of the raging, dirty run-off on Saturday to alert his friends not to swim that day - noting there was a distinct black sediment which was separating and getting caught on the sand.
Further south, Kaye Osborn was walking her dog near Bellambi Beach and saw a "black plume" flowing out of the nearby creek and into the sea, leaving a grey slick.
She said the last time she had seen the creek looking "this bad" was several years ago, so walked up upstream to investigate.
Her videos - also from Saturday - show a black, sludgy mess cruising down Bellambi Gully Creek so she reported it to authorities.
A spokeswoman for the EPA said investigations in the Woonona incident were ongoing as there were no "licensed premises" in the upstream areas and they would work with Wollongong City Council to find the cause.
In regards to Bellambi Gully Creek, environmental officers surveyed the area on Monday morning and "observed brown coloured water that is typical of urban storm water during rainfall".
The spokeswoman said there was no evidence found of coal pollution in Bellambi, with the discharge to be attributed to the storm rather than a coal mine at Russell Vale.
"Publicly available data from the Wollongong Coal's water quality monitors recorded elevated sediment across monitors on and off the site on Saturday," she said.
"These readings appear to be associated with heavy rainfall across the entire catchment on Saturday ( 50 mm), particularly during the evening.
"In addition, Wollongong Coal has advised the EPA they are not aware of any issue that would have resulted in the discharge of coal wash."
The public is still encouraged to report pollution incidents to the Environment Line on 131 555 for investigation.
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