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Pollution By Stormwater The stormwater system is designed to take rainwater from our streets and guttering into the closest waterway. Unlike sewage, stormwater is not treated before it enters our waterways. In some cases it is filtered by traps or wetlands, usually located at the end of the pipe system, but in most cases it flows directly from our streets and gutters into our creeks, rivers, bays and the ocean. Maintaining our water quality is a challenge that we all should strive to meet. As our population grows and urban development continues, we must be mindful of the direct link between the stormwater system and our rivers, creeks and bays. All Victorians have a role to play in maintaining the quality of our waterways now and for future generations. This web page will provide you with information on the following points: Urban Stormwater Quality; Urban Stormwater Quantity; Types and Causes of Stormwater Pollution; What We can Do About Stormwater Pollution; and Stormwater Management. Urban Stormwater Quality Urban areas have extensive tracts of constructed impervious surfaces like roads, driveways, car parks, roofs and paving. When stormwater run off flows over these hard surfaces, it readily accumulates pollutants. Stormwater pollutants originate from many different sources ranging from fuel and oil from our roads, to litter dropped on our streets and sediment from building sites. Improving stormwater quality in the long-term will require effective prevention and management of these pollutants at their source as well as treatment of stormwater before it enters our waterways. Urban Stormwater Quantity In urban areas, the increase in the number of impervious areas has reduced the amount of rain that infiltrates the ground or is retained by vegetation. Consequently, increased quantities of stormwater run-off enter the drainage system and the receiving waterways. Urbanisation has also changed the timing for stormwater discharged into water environments. Traditionally, stormwater drainage systems have been constructed to remove stormwater from urban areas as quickly as possible in order to minimise the risk of flooding and to prevent water from becoming stagnant. The increased volume entering waterways causes scouring (in stream erosion) of waterways. In less modified catchments the run-off water is released over a longer period of time and with lower peak discharges, which maintains healthier water environments. Reducing stormwater run off can be more difficult in well-established urban areas that have high density of buildings and infrastructure. However, new developments and the re-development of some urban areas can easily incorporate measures that increase infiltration and reduce adverse impacts on our waterways. For example, we can increase the amount of stormwater infiltrating the ground by using grass swale drains, vegetated filter strips and porous pavements. We can also protect stream habitats and restore creeks that were previously modified (channelled), by incorporating meanders, pools and instream vegetation. Urban stormwater quality should be considered together with the quantity and timing of stormwater run-off entering our water environments. Measures designed to improve stormwater quality and quantity should not compromise the objectives of public safety and local flood protection. In fact, measures designed to improve the environmental management of urban stormwater often have inherent flood management benefits. Types and Causes of Urban Stormwater Pollution Stormwater pollutants originate from many different sources ranging from fuel and oil from our roads, to litter dropped on our streets and sediment from building sites. There are three main types of stormwater pollution: litter, for example cigarette butts, cans, food wrappers, plastic bags or paper; 'natural' pollution, for example leaves, garden clippings or animal faeces; chemical pollution, for example fertilisers, oil, or detergents. Below is a table of the common pollutants found in urban stormwater, their likely sources and the effect of the pollutant on our waterways. Pollutant Sediment Effect Reduces the amount of light in the water available for plant growth and thereby reducing the supply of food for other organisms. Can clog and damage sensitive tissues such as the gills of fish. Can suffocate organisms which live on or in the bed of lakes and streams by forming thick deposits when this suspended material settles out. Urban Source Land surface erosion; Pavement and vehicle wear; Building and construction sites; Spillage/illegal discharge; Organic matter (eg leaf litter, grass); Car washing; Weathering of buildings/structures; Atmospheric deposition. Nutrients An increase of nutrients in water stimulates the growth of aquatic plants. This causes excessive growth of aquatic weeds and algae that may choke lakes and streams and lead to dramatic daily fluctuations in dissolved oxygen levels. Oxygen Demanding Substances PH Acidity Oxygen is used up more quickly than it can diffuse into the water from the atmosphere. The resulting drop in oxygen levels may then be sufficient to kill fish and other aquatic organisms. If all the oxygen in the water is used up, unpleasant odours can result. increased acidity damages plants and animals Micro-organisms Toxic Organics Contain very high numbers of bacteria and viruses. Some of these organisms can cause illnesses, including hepatitis and gastroenteritis. Can poison living organisms or damage their life processes. Heavy Metals Poison living organisms or damage their life processes in some other way. Persists in the environment for a long time. Organic matter; Fertiliser; Sewer overflows/septic tank leaks; Animal/bird faeces; Detergents (car washing); Atmospheric deposition; Spillage/illegal discharge. Organic matter decay; Atmospheric deposition; Sewer overflows/septic tank leaks; Animal/bird faeces; Spillage/illegal discharges. Atmospheric deposition; Spillage/illegal discharge; Organic matter decay; Erosion of roofing material. Animal/bird faeces; Sewer overflows/septic tank leaks; Organic matter decay. Pesticides; Herbicides; Spillage/illegal discharge; Sewer overflows/septic leaks. Atmospheric deposition; Vehicle wear; Sewer overflows/septic tank leaks; Weathering of buildings/structures; Spillage/illegal discharges. Gross Pollutants (litter and debris) Unsightly. Animals can eat and choke on this material. Oils, Detergents and Shampoos (surfactants) Highly toxic poison to fish and other aquatic life. Increased Water temperature High temperatures are lethal to fish and other aquatic organisms Elevated water temperatures stimulate the growth of nuisance plants and algae. This and other effects can lead to decreased levels of dissolved oxygen which can threaten other aquatic life. Pedestrians and vehicles; Waste collection systems; Leaf-fall from trees; Lawn clippings; Spills and accidents. Asphalt pavements; Spillage/illegal discharges; Leaks from vehicles; Car washing; Organic matter. Run-off from impervious surfaces; Removal of riparian vegetation. (Table modified from Table 1.1 in Urban Stormwater: best practice environmental management guidelines, 1999 CSIRO). What can we do about Urban Stormwater Pollution? The most effective way to reduce stormwater pollution is to stop it entering the system in the first place. In other words, if you look after your local drains, you can dramatically improve what happens in our creeks, rivers and bay. Individuals can help reduce stormwater pollution through the following actions. Tips to prevent stormwater pollution Washing your car Wash your car on a grassed area rather than on the road. That way the detergents and dirt will not run down the road and into a stormwater drain. Fixing your car If you are fixing your car at home do not tip engine oil into stormwater drains. Check with your local council regarding chemical collection services. Also make sure your car is regularly maintained so it does not leak oil or petrol. Disposal of garden waste An alternative to allowing leaves or garden clippings to accumulate in gutters or driveways is to sweep them up and start a compost heap or use them in your garden as mulch. This way you will prevent them entering the street drain where they can cause pollution. Put litter in a bin Make sure all your litter ends up in a bin. Litter dropped in our streets ends up in our street drains and is transported to our waterways following rain. Paint brush cleaning Rinse paint brushes in the laundry trough or garden rather than letting the contaminated water flow into the street stormwater drain. Tip or wipe excess paint on brushes onto newspaper or a rag. Allow to dry and then place this waste in a bin. Cleaning the footpath Always sweep rather than hose your footpath and place waste in the bin. Hosing with water carries dirt, soil or other waste into the street drains. Pick up dog droppings Always clean up after your animals. Dog dropping left in our streets ends up in our street drains and is transported to our waterways following rain. Stormwater Management The value of our waterways is important to present and future generations. In spite of increasing populations and levels of development in urban catchments, many streams and waterways still retain significant natural value and provide important environmental, commercial and recreational benefits. It is important that these uses are protected from the threat of stormwater pollution. Environmental studies, have found that some of the main areas of poor environmental quality in our waterways correspond with urban stormwater inputs from drains, creeks and rivers. This is so for the Yarra River. Studies in regional Victoria have also highlighted urban stormwater pollution as a significant cause of long-term degradation of important water environments. Waterways close to regional centres are particularly vulnerable to stormwater impacts. Protection of our waterways largely depends upon improved management of pollution carried by stormwater. This has become apparent in a number of Australian cities and overseas, where better management of stormwater within urban catchments has now become an essential component of improved water quality management programs. Local government, Melbourne Water, the Department of Infrastructure, the Department of Sustainability and Environment, Catchment Management Authorities and EPA all play a role in managing stormwater in Victoria. EPA's program to control stormwater discharges includes controlling industrial discharges to stormwater through regulation and advice to industry on best environmental practice