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Stormwater Pollution

Stormwater Pollution I The Difference Between Stormwater and Sewage I Pollution Sources I The Impact of Stormwater Pollution I Major Pollution Sources I Penalties for Stormwater Pollution

Stormwater Pollution

Urban stormwater pollution is one of the biggest threats to the health of our waterways.

Stormwater is water which, after rainfall, drains off the land surfaces of our roads, roofs, buildings and driveways into drains. When it rains, stormwater run-off washes oil, grease, dirt, fertilisers, chemicals, leaves, cigarette butts and litter from our yards and streets, into gutters and drains. The gutters and drains are the beginning of the stormwater system; they transport stormwater run-off via channels and pipes straight into our creeks and rivers and eventually into Botany Bay. This results in pollution of our waterways.

The Difference Between Stormwater and Sewage

Stormwater flows directly into our waterways untreated. However, household waste-water from our toilets, showers and sinks is collected via the sewerage system and is treated at the sewage treatment plant before it is discharged into the ocean. Therefore it is important to remember that the Drain is Just for Rain!

Pollution Sources

Our waterways become polluted when anything that is not natural enters them. Many pollutants are regularly released into the stormwater system from residential, commercial and industrial areas.

Pollution in local waterways can be either point source or non-point source. Point source pollution comes from one identifiable outlet or source, such as an industrial discharge, spill or sewage overflows. Non-point pollution is more difficult to trace as it comes from a combination of sources across a catchment, including litter and domestic fertilisers.

The Impact of Stormwater Pollution

Toxic chemicals such as heavy metals, oils and grease which accumulate in sediments and aquatic life can reach toxic levels in fish and plants. High levels of phosphorus can lead to blue-green algal blooms which consume the oxygen that supports marine life. Litter and dumped rubbish affects the quality of our waterways. Plastics in particular pose a major health hazard to marine life because aquatic animals can swallow or become tangled in plastic. Faecal coliforms, a sign of sewage overflows, can cause disease and illness to people who come into contact with polluted water.

Major Pollution Sources

Major stormwater pollutants and their sources are summarised in the table below.






Road run-off

Oil, petrol

Toxic to aquatic organisms


Fertilisers, detergents

Phosphorus, nitrogen, fertilisers from gardens and golf courses

Excessive growth of aquatic vegetation; algal blooms

Toxic material

Pesticides and herbicides

Garden and agricultural products

Accumulate in food chain, toxic to organisms


Discharge from industry and vehicle emissions (particularly lead) from road surface run-off

Lead, mercury, zinc and copper

Concentrate in sediments and bio-accumulate in living organisms

Bacteria and viruses

Sewage overflows, defective sewage systems, animal faeces

Faecal coliforms and faecal streptococci

Sickness and infections in bathing waters; seafood unsafe


Building sites

Sand, sediment, cement

Destroy habitats by smothering plants and animals living on bottom of waterway

Inorganic litter

Roads, parks, shopping centres

Fast food packaging, plastics, aluminium cans, paper and cigarette butts

Aesthetically unpleasing and can entangle wildlife causing death

Organic litter

Parks, roads, bushland

Leaves, twigs and garden waste

Decreases sunlight penetration in water and destroys habitats

Penalties for Stormwater Pollution

It is an offence for anyone to let any substance other than rainwater enter a waterway, including the stormwater system. You can be fined for water pollution by washing your car on the street ($4,000), disposing grass clippings or oil down the stormwater drain ($4,000), dropping litter - large item ($250), small item ($80), discarding a lit cigarette ($250) and discarding an extinguished cigarette ($80).

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