Sign at Rushcutters warns of sewage overflow Photo: Alana Levene

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BY ALANA LEVENE

Sydney Water is urging residents to watch what they’re flushing down their toilets after a recent sewer blockage caused wastewater to drain into Rushcutters Bay, blocking the area to swimmers for weeks.

This is the fourth choke in the in Paddington area since the beginning of November, according to a Sydney Water spokesperson. The chokes happen when people flush rags, wet wipes and other materials that don’t belong down the drain.

“People need to understand that the wastewater system is not a rubbish disposal and that anything other than what it’s designed for has to be removed so that it doesn’t end up in the environment,” a Sydney Water spokesperson said.

The organisation initially advised the community of the contamination on 8 April. The advisory remained active on 23 April, a spokesperson confirmed, even though the choke had been cleared.

In the meantime, the Water Department is asking people to avoid swimming due to the lingering possibility of pollution.

Sewage overflows common

Sewer overflows occur frequently across Sydney, particularly after heavy rainfall, when the sewage system becomes overloaded.

“It is fairly common when we have heavy rain events,” said Michelle Rose, an environmental education officer for the Woollahra Council.

As a general precaution, swimming in Sydney Harbour is discouraged for up to three days after rainfall or for as long as stormwater is present. If there are signs of water pollution, like discoloured water, odour, oil, scum, or floating debris, swimming should be avoided.

“This is a real problem for Sydney Water,” said a Sydney Water spokesperson, “which is why our ‘Clean up not down’ campaign stresses that we should always use a rubbish bin and not dispose of wipes or any other bathroom products down the toilet.”

This also includes tissues, the spokesperson said.

This is not a problem unique to Sydney, according to Dr Serena Blyth Lee, who has constructed hydrodynamic models of water movement in the Sydney Harbour.

Sections of Sydney’s complex sewerage infrastructure are old. With age comes maintenance problems, said Lee.

“Older components of the infrastructure may not have been designed to carry the present population load,” Lee said. “Like roads, the network has likely been retrofitted to widen pipes etcetera, but as with any large infrastructure, upon which we rely, this has to be done a piece at a time.”

There are several overflow points at which sewage can overflow into the stormwater network.

Since Rushcutters Bay isn’t a well-flushed locality, among other factors, overflow and subsequent contamination will likely continue with current rates of sewage discharge, according to Gavin Birch, an expert on pollutants in the Sydney Harbour. This is because it is located a few kilometres away from the estuary mouth.

“The most likely issue related to sewage contamination would be faecal coliform virus,” Birch said.

“E. coli — which is a type of faecal coliform bacteria — triggers beach and bay closings,” Lee said.

The signage will remain in place likely until e. coli concentrations, or other bacteria capable of affecting human health, fall below the acceptable limit for a few successive days,” Lee said. “Daily monitoring is likely taking place to monitor these concentrations.”

The warning will be in effect as a precaution until the test results come back completely clear. A Sydney Water spokesperson could not say on Tuesday whether faecal coliform bacteria is present in Rushcutters Bay.

“The results from the most recent testing show dissolved oxygen levels are typical, which would indicate no impacts to the aquatic environment,” the spokesperson said.

The organisation ordered a CCTV inspection of the wastewater pipe to identify blockages and faults, and analyse the current system’s performance.

“Sydney Water takes its responsibility to protect public health and the environment seriously,” the spokesperson said.

Continuing to monitor

“Sydney is blessed with one of the most beautiful harbours in the world,” Birch wrote back in 2007 in a book chapter that outlined Sydney’s geological and environmental history.

“However, like many large, capital ports world-wide, this environment has been exposed to relentless stress due to a rapidly increasing population density and extensive residential, commercial and industrial expansion,” he wrote.

Since 1972, the Clean Waterways Act has controlled discharge into the Harbour’s estuaries. Since 1990, sewage has been dispersed into the sea about four kilometres from the coast, according to Birch.

Sydney Water is also continually conducting water tests to detect sewage.

To avoid future blockages, the organisation says that nothing should be going down sinks and toilets other than wastewater.

For the sinks, no fats oils, and greases, the spokesperson said. And for the toilet, “that’s the 3Ps: only Pee, Poo and Paper.”