Water Kit - Hunter Water

3.5 stormwater management
What is stormwater?
Stormwater is runoff produced by rainfall
that flows into drains or directly into
waterways, wetlands and eventually the
ocean. In urban areas, rain that falls on
houses or runs off paved areas such
as driveways, roads and footpaths, is
carried away through a system of pipes
separate from the wastewater system -
this is called the stormwater system.
Stormwater management
Hunter Water’s role in the management
of stormwater is to maintain stormwater
channels and culverts in the Newcastle,
Lake Macquarie and Cessnock local
government areas. This includes
preventing the accumulation of rubbish.
Hunter Water’s stormwater infrastructure
comprises large scale, concrete trunk
drainage systems constructed to collect
and transport large urban stormwater
Hunter Water helps councils manage
stormwater in the shaded areas
flows into receiving waters. The
stormwater infrastructure controlled
by local councils includes the street
drainage (inlet pits and pipes) that
drains into this system, and the
less formalised ‘natural’ channels
throughout areas upstream and
sometimes downstream of Hunter
Water’s systems.
The majority of Hunter Water’s
stormwater assets are located within
the Newcastle area, in the major urban
catchments of Throsby Creek and
Cottage Creek. Stormwater treatment
structures in the Throsby Creek system
include a sediment trap with floating
Water kit . ssS . 001 . april 2010
boom at Tighes Hill and trash racks in
Lambton and Adamstown.
In Lake Macquarie, Hunter Water
operates stormwater assets in the
Winding Creek catchment, and in
Cessnock stormwater assets are
situated through the urbanised
sections of Black Creek.
Stormwater pollution
There are three main types of
stormwater pollution that are
discharged to our waterways:
• litter, eg cigarette butts, cans,
paper, plastic bags
• chemicals, eg detergents, oil,
fertilisers
• organic materials, eg leaves,
garden clippings, animal
droppings
Stormwater treatment
Unlike wastewater, stormwater is not
treated at a wastewater treatment
plant. This means its quality is largely
unmanaged and variable. In some
situations it passes through pollution
traps, usually located at the end of the
stormwater pipe system.
However, pollution traps only filter large
pieces of litter from the water. These
traps do not remove dissolved solids,
nutrients, sediment, greases and oils
that are often found in stormwater.
Since Hunter Water’s upgrade of
wastewater treatment works in the
Lower Hunter, the major cause of poor
water quality at beaches is polluted
stormwater after heavy rainfall.
We can all help reduce the volume of
stormwater entering waterways and
minimise its pollution. It is more cost
effective to prevent stormwater pollution
than to have to deal with it once it has
occurred.
What affects stormwater
pollution?
The volume and severity of stormwater
pollution is affected by:
The timing and
intensity of
rainfall
building density
and land uses
within the
catchment area
the extent of
vegetation cover
the cleanliness
of streets
Activities that cause
stormwater pollution
Some examples of activities that can
cause stormwater to become polluted
are:
Stormwater impacts
local practices, eg
street sweeping
and chemical use
washing cars in
the street lets
detergents enter
drains and
waterways
dropping litter
where it will be
swept into drains
the next time it
rains
cleaning paint
brushes into
street drains
Environmental impacts
Since stormwater is not treated before
it enters local waterways, it is often
very polluted and can have many
adverse impacts.
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