THE STORMWATER SYSTEM
What is stormwater?
Stormwater is the runoff generated by rainfall plus anything that is carried with it. In an urban environment stormwater has the potential to become polluted.
The Stormwater System
Unlike some other countries, we have separate systems for sewerage and stormwater. Sewerage systems are usually directed to a treatment plant whereas the stormwater system usually discharges to a river or water body.
Roof water, water runoff from driveways, paths, carparks, water from grassed areas and road runoff are all generally directed to the stormwater system which discharges into the river system.
Stormwater systems components
In Dubbo, the stormwater system consists of underground drains, open drains and swales, stormwater inlet pits and stormwater pipes.
There are over 200km of pipes within the urban area. If you laid them end to end then they would stretch along the Mitchell Highway from Dubbo to Bathurst.
The urban area has more than 6500 stormwater pits, with many of these being inlet pits that capture stormwater runoff.
Council has 36 Gross pollutant traps to help trap pollutants and over 70 retarding basins which control discharge and help to reduce stormwater flows.
A stormwater catchment is an area where the runoff drains to a single point. In an urban environment a catchment may consist of different land use areas.
Do you know where the storm water goes?
What happens to the water when it runs down your driveway and into the gutter?
Where does the water from the stormwater system end up?
Why are Dubbo Drains Just For Rain?
Gross Pollutant Traps
What is a gross pollutant trap?
A gross pollutant trap is a device that is installed to help remove pollutants from stormwater.
How many Gross Pollutant Traps does Council have in the urban area?
Council has 36 Gross Pollutant Traps under its control within the urban area
How many times does Council clean the Gross Pollutant Traps?
This depends on the type and size of the catchment draining to the trap. Council has a cleaning program based on stormwater industry information and its own data. Council continually reviews and improves its GPT inspection and cleaning methodology.
Inside of a Gross Pollutant Trap showing collected litter.
Artificial Wetlands are used to help clean the stormwater by the removal of nutrients and the settlement of suspended solids. Council has one artificial wetland which was constructed in 1999. For more information please click on the attached link for a brochure on Egret Park.
Swales and Bioswales
Swales and bioswales can also act as filters for sediment and other pollutants which enter our stomwater system.
A typical roadside swale.
Treatment Train Approach
The treatment train approach is the use of several types of devices in series to treat stormwater. This may include swales, wetlands and gross pollutant traps. The idea being that each stormwater quality improvement device is used a part of the overall treatment of stormwater.
What Can you do to help?
Please place litter into the bins
Do not wash cars on driveways or in the street.
Minimise use of chemicals that may be washed into the drainage system.
Collect lawn clipping and garden waste.
How does Council manage its stormwater assets?
Council uses asset management guidelines developed by the Institute of Public Works Engineers to help manage the stormwater system. Regular CCTV inspections are undertaken to check the conditions of pipes. This coupled with age profiling and expected useable lives of the assets helps Council to plan repairs and renewals.
Expanding the system
All new subdivisions include the construction of stormwater assets. The underground network can expand by between 5 and 10km per year, based on rates of development.
Capital Works Program
Council has a capital works program where planned expansion of the stormwater system helps to alleviate potential stormwater flooding issues.
Construction of stormwater pipes in North Dubbo.
For more details please contact Council's Customer Service Centre.
Last Edited: 27 Oct 2017