Stormwater
 Stormwater is rain which has run off the land including the hard,
"impervious" surfaces like roads, roofs and car parks. Traditionally stormwater
has been piped away from these hard surfaces and discharged into the nearest
waterway (e.g - stream, beach, harbour, wetland). Stormwater is usually not
treated in any way.
Beneath Waitakere City's streets, there is a complex network of 590km of stormwater pipes which carry stormwater downhill to discharge points. For most
of us, the only visible signs of this network are the familiar grates on the
side of the road and perhaps the pipes at the local beach or stream.
Why stormwater has become a problem
In the past, stormwater run-off was only of concern as it could cause
flooding.
Now, stormwater is internationally acknowledged as being a major source of
pollution in the world's waterways. Our modern lifestyle contributes to stormwater pollution, often unwittingly.
Stormwater is contaminated by:
- motor vehicles through metals such as lead, copper, zinc and oil washing
off roadways (it is estimated that 70% of stormwater pollution is caused by
cars)
- rubbish such as plastic bags, bottles and other street litter
- herbicides, garden fertilisers, rotting lawn clippings
- detergent from car washing
- domestic animal faeces
- illegal and accidental spills/dumping into stormwater drains
- air pollution
Stormwater is also dramatically reducing the effectiveness of our wastewater
or sewerage system. In the Auckland region stormwater makes up about 40% of the
annual average wastewater flow. During times of heavy rain, stormwater leaks
into the wastewater network causing it to overload and overflow. These overflows
eventually find their way into the stormwater system and our natural waterways.
They add to the toxic cocktail already in stormwater and pose a serious risk to
public and environmental health.
What we need to consider:
- finding environmentally sustainable ways to manage urban stormwater
- upgrading the regional stormwater systems
- what it will cost to improve the stormwater network.
- public transport versus widespread private motor vehicle use
What is being done right now
EcoWater is currently working on wassa - an
Assessment of Water & Sanitary Services
to look at the best ways to sustainably manage our three waters.
New Stormwater Drainage Connections
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To have your drainage connection installed or for further information,
please contact our Call Centre
Pricing
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Fees & Charges Schedule
(Size 226K)
Find out about Council's innovative project and work with
the community to help restore our streams and improve water
quality -
Twin Streams.
Locating Pipelines
This service entails locating buried service pipes and may attract a charge.
Please contact us for more details.
Countryside & Foothills Stormwater Management Code of
Practice
Waitakere City Council is committed to a policy of avoiding, remedying or
mitigating the adverse environmental effects of these changes to the greatest
possible extent. The Countryside & Foothills Stormwater Management Code of
Practice (CFCOP) looks at why stormwater must be managed, the adverse effects
that may be caused, design objectives and the limitation of this document.
The CFCOP was commissioned by EcoWater Solutions. Depending on the project,
EcoWater Solutions or the Auckland Regional Council process permit
applications relating to stormwater discharges in Waitakere City.
This document has been divided up into separate sections and can be
downloaded individually. It is recommended that you download sections 1 to
3 along with your desired sections.
This is Version 3 of The CFCOP and was published on 29 June 2005.
This document is large in terms of file size and may take
some time to download. Alternatively you can
contact us
for a copy. Please note: Hard copies cost $30 each.
Note: You will need to have
Adobe Acrobat Reader
installed on your computer in order to view and print these documents. For
help opening PDF files or tips on copying information see Helpful
Tips.
Stormwater Solutions
for Residential Sites
This document promotes methodologies for on-site control
of stormwater that are designed to control the effects of
development in an existing urban environment. The document
was developed by EcoWater Solutions (WCC) and is intended to
provide guidance to landowners, developers, engineers and
surveyors on the stormwater management methods applicable to
urban residential sites located in Waitakere City. In this
document "Council" refers to Waitakere City Council.
The document focuses on the management practices
applicable to developments on individual residential lots.
This includes new houses, house extensions, new garages and
driveways. Methodologies described in the document generally
apply to residential properties of 1,000 m2 area or less.
The intent is that the document will be used by WCC
engineers, and applicants for stormwater control for
building permits for these types of developments.
This document is large in terms of file size and may take
some time to download. It can be downloaded as a single
complete document or as individual sections.
Stormwater Solutions for Residential Sites (Size
3M)
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help opening PDF files or tips on copying information see Helpful
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Permeable Paving
The recent floods in Waitakere have highlighted the
importance of keeping hard areas like roofs, roads and
footpaths to an absolute minimum.
Achieving this is often easier said than done but one area
where almost every household can help is in the use of
permeable pavers.
Hard areas are bad news in heavy rain because they cause
stormwater to run-off in volume, at speed and sweep
pollution along with them. Wherever rain can soak in, there
is the opposite effect. It is slowed down and filtered
through the earth.
In fact, that is why there are limits on how much of your
property you can cover in impervious surfaces - 60% of your
section if it is connected to Council's stormwater drain and
only 15% if your property relies on soakage, kerb or stream
discharge (without a consent).
Permeable pavers however, give you the best of both worlds:
paving where you need it, combined with provision for the
water to soak through rather than run-off.
The stormwater problem
Stormwater that runs off urban surfaces (roofs, roads etc) various pollutants as it drains (such as oil, grease and other chemicals) into stormwater pipes and into our streams with little or no treatment to clean it. This is a major source of pollution in our streams and harbours.
Currently some stormwater run-off in Waitakere City is treated in wetlands, swales or other devices. These and other strategies are being used in Project Twin Streams to work with nature to manage and cleanse stormwater. The end result will be restored streams and improve the water quality. Treating stormwater is one of the important ways to do that.
What are permeable paving surfaces?
Permeable paving may include pavers, Gobi
blocks, turf blocks and similar, that provide surfaces that
water can drain through. It is essential that the paving
sits on top of a "basecourse" (free draining metal) which
allows the water to continue to drain into the ground. It is
also important that in-between the layers of basecourse
there is a geotextile (fabric) layer which helps keep the
basecourse layers separate. A perforated pipe in the
basecourse layer also helps speed up the drainage.
Open pavers are designed to accommodate
plants without affecting the structural performance. Not
only do these types of pavers reduce the amount of
impermeable surfaces on your property, they can also help
treat stormwater.
Why use permeable paving?
Permeable pavers provide stormwater treatment by allowing
water to filter through the pavers and basecourse into the
earth where it's filtered through the ground or collected in
subsoil drains before flowing to our streams. They also
help reduce erosion in our streams as they slow down the
rate of flow of the stormwater which also helps reduce
overloading in the City's stormwater system.
How do I construct a permeable paved area?
Contact Us for
details and instructions.
Where could I use permeable pavers?
- Parking areas
- Private driveways
- Walk ways
- Lawns (open pavers)
Is this a costly method?
The permeable paving system is more expensive than normal
materials, however savings are made in reduced stormwater
pipe sizes and stormwater quality benefits.
Do I need a Council permit or Building Consent?
-
In general, not for smaller areas of paving (anything
over 1 metre wide requires a Consent). However, in all
cases, it is recommended to
Contact Us.
- If you are building a house or outbuilding (shed,
garage etc), then this would be taken into consideration
with the Building Consent.
- If the construction of a permeable area is recommended
or required through a Resource Consent, then inspection
and monitoring is required by Council's representative
during construction and at completion.
- As regulations regarding earthworks and impervious
surfaces vary within the city, please check with Council
before embarking on any work
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