Storm Water Frequently Asked Questions

Paul Milic Director Stormwater Sydney

What are the Environmental Requirements?

Within NSW Stormwater management is regulated by several authorities. These include NSW EPA, Sydney Water (in Sydney Basin) and Local Councils. The various websites of the specific authorities can provide specific details. 

What are my Council Requirements?

Believe it or not many Councils have slightly different requirements which makes it hard to comply with. Most Councils publish their requirements on their web sites. OSD Australia has identified the requirements of all Council, which we utilise on our inspection and Audits.

All Councils though do do require the installation of OSD on all new premises. These requirements usually include a Section 88 Instrument requiring ongoing maintenance of any devices across the life of those devices. 

What is best practice in Stormwater Management?

Stormwater NSW has produced a best practice guide for the operation and maintenance of OSD device. OSD Australia have adopted this as our baseline standard for all works. 

Why are OSD devices with confined spaces more expensive than without?

Some OSD devices include underground tanks with restricted access and the potential to build up dangerous gases, hence increasing WHS risks.

Such devices require specialist staff and equipment to ensure safe entry. In the event that we are not aware of a confined space, we may be required to charge a cancellation and rebook the appointment with additional resources.  

Stormwater Terms

Stormwater Sydney can unblock you drainage system


Any action that reduces factors such as the level or intensity of peak stormwater discharge, pollutant concentrations or loads, during storms or floods.


The process of sucking up or drawing in of a liquid by a porous substance.

Access hole

An opening constructed in a structure to permit human access for the purpose of construction, inspection and/or maintenance. This term is replacing MANHOLE.

Allotment drainage

A system of field gullies, access chambers and underground pipes constructed within private property to convey flows through and from allotments.

Artificial wetland

A water treatment system utilising wetland processes that do not necessarily reflect the natural environment, and where significantly high levels of maintenance are required to achieve their design performance. Examples may include some constructed sub-surface flow wetlands (i.e. gravel bed biological filters).

Baffled pit

A modified stormwater pit fitted with baffles that are specifically designed to encourage heavy sediments and floating debris to remain in the pit.

Stormwater Sydney assists Councils and property managers maintain their drainage assets

Best practice environmental management

The management of an activity in a manner that achieves 43* ongoing minimisation of environmental harm through cost-effective measures assessed against the measures currently used nationally and internationally for the activity.

Detention basin

A basin designed to temporarily hold storm or flood  waters, and release such waters in a controlled manner to attenuate outflows. No water is retained within the basin between storm or flood events.

Detention system

Any stormwater detention management system—basin, parking lot, depressed grassy area, rooftop storage, buried or aboveground tank—used to temporarily detain storm or flood waters for the purposes of delaying or attenuating outflows from a site or catchment.

Diversion drain

A drain that transports stormwater runoff from the 5 shoulders of a road or table drain to a disposal area.



A constructed channel or conduit used for drainage purposes.

Grass swale

A shallow, low-gradient, grass-lined drainage channel used to convey and treat shallow, concentrated stormwater runoff. The swale may or may not contain a subsoil drainage system. Grass swales treat stormwater by settling, filtration and infiltration; they remove pollutants such as sediment, grit, nutrients and hydrocarbons.

Stormwater Sydney services backyard drainage pits


A grid of metal or other material used to prevent debris 2* from entering a drain or pit while allowing pedestrians
and vehicles to pass safely over the opening.

Litter rack

A grill, grate or other barrier located across a channel or 5 pipe to trap litter and debris. The bars may be vertical, horizontal or angled (relative to the direction of inflow) depending on hydraulic and environmental requirements,

such as fish passage or exclusion requirements. Also known as a TRASH RACK.


Routine work required to maintain existing works and systems in a safe and functional condition.


On-Site Detention or On-Site Stormwater Detention


The point at which water discharges from a river, creek or other flow line; lake, tidal basin or drainage depression; or pipe, channel, dam or other hydrologic structure.


A structure or wall built across a channel, drain or watercourse to raise the water level to allow diversion or measurement of discharge rate.

Weirs may be either sharp-crested or broad-crested, and may operate in either a state of free discharge, or a submerged or drowned state.

Stormwater Australia Glossary