Download Urban Stormwater pollution

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:
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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:
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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
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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.
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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.
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increased acidity damages
plants and animals
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Micro-organisms
Toxic Organics
Contain very high numbers of
bacteria and viruses. Some of
these organisms can cause
illnesses, including hepatitis
and gastroenteritis.
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Can poison living organisms or
damage their life processes.
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Heavy Metals
Poison living organisms or
damage their life processes in
some other way. Persists in
the environment for a long
time.
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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.
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Oils, Detergents and
Shampoos (surfactants)
Highly toxic poison to fish and
other aquatic life.
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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.
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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