RAW sewage was dumped into a series of rivers and creeks around Melbourne at the height of this month's floods after the city's sewage network failed to cope.

A host of urban waterways, including the Yarra River, Maribyrnong River, Merri Creek, and Moonee Ponds Creek were subjected to the dumping as Melbourne Water sought to prevent sewage backing up into Melbourne homes.

Drains in Elwood, Brighton and Hampton were also fouled, prompting accusations that authorities failed to properly warn people of the risks to human health.

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The incident occurred on the weekend of February 5, when up to 195 millimetres of rain fell over parts of Melbourne. The deluge overwhelmed the major sewage treatment plants, forcing Melbourne Water to dump untreated waste through emergency sewer exits around the city.

It was unclear yesterday when, if ever, Melbourne Water last had to resort to such an extraordinary procedure.

The sewers carry wastes from households and businesses - including toilet waste, bathwater and industrial discharges - and are separate to the drainage system that collects stormwater run-off from roads and other surfaces.

Melbourne Water mentioned the sewage dumping in a press release on Saturday, February 5, but did not reveal the locations until asked by The Age yesterday.

In the seventh paragraph of the February 5 press release, Melbourne Water said it was ''co-ordinating releases of waste water into drains and waterways via special emergency relief points''.

The same press release later warned people to stay out of waterways because there could be elevated levels of E. coli - a warning that is made after most heavy rains.

Clean Ocean Foundation spokesman James Clark-Kennedy said those mentions did not convey the gravity of the situation, and Melbourne Water had jeopardised human health by underplaying the incident.

''Why do we have to fish into the [lower] paragraphs of a press release … the communication has been bloody disappointing,'' he said.

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