Frequently Asked Questions - Spills During 4-5 February Floods
- How did the spills happen?
- What impact did the spill have on rivers and creeks?
- What was the community told?
- Do the spills to the waterways pose a health risk?
- How long do the impacts of the spill last?
- Has something like this ever happened before?
- What are you doing to better prevent this from happening?
1. How did the spills happen?
The sewerage network has extra capacity to take stormwater in wet weather. This is an addition the capacity offered by Melbourne’s stormwater drainage system.
As an added failsafe, there are emergency outlets across the sewage network that act as an extra layer of protection for the system in the event of extremely intense rainfall.
These outlets allow pressure to be taken off the system in rare and extreme conditions by enabling a controlled release of highly diluted sewage into suburban creeks and waterways. Failure to release under these conditions would risk ‘backing up’ of the sewage system, which among other things would result in spills into people’s households (showers especially, as they are the lowest point in most homes).
2. What impact did the spill have on rivers and creeks?
The releases would have consisted of very heavily diluted sewage even before it reached the river, which would dilute even further once in the river.
Given how diluted the discharges were, the practical impact on river health is extremely low and these discharges would have been washed out very quickly.
3. What was the community told?
Melbourne Water issued a media release on behalf of Melbourne’s metropolitan water authorities on Saturday 5 February 2011, sent to all media, and posted via our website and Twitter feed (#melbourne).
The EPA issued a number of stormwater alerts, advising people of the potential risk of coming into contact with contaminated water. These were published on the EPA website and provided to the media.
SES also provided advice about water quality during the floods, specifically referencing the potential for floodwaters to contain sewage.
4. Do the spills to the waterways pose a health risk?
Like any urban body of water, floodwaters carry inherent risks to human health.
The Department of Human Services advises people to avoid any contact with floodwaters as they may be contaminated. And if this is unavoidable, then disinfect the affected area thoroughly. The Department of Health has more information on what to do.
5. How long do the impacts of the spill last?
Anytime we have a major flood it has impacts on our waterways. Bacterial levels in water will reduce over time as the bacteria die off due to exposure to a range of factors, such as sunlight.
We don’t expect any long term effects from the higher bacterial levels associated with this flood event.
6. Has something like this ever happened before?
Spills of the type we saw on 5 February are rare; the last time they approached this level was after a major storm in February 2005.
7. What are you doing to better prevent this from happening?
While it’s not practical to build a system that could effortlessly cope with the inflows seen on 4-5 February, two major sewerage projects are underway that will increase the ability of the sewage system to deal with extreme wet weather flows – the Northern Sewerage Project and Melbourne Main Sewer Replacement project.
Combined, these two projects represent an $870 million investment in the city’s sewerage network and are both due for completion in 2012.
We’re also investing over $50 million in a major upgrade of the drainage system in Frankston.
More information
- More information on spill during floods
- Water authorities respond to storm
- Drainage system recovers from record deluge