Get approval for an on-site detention (OSD) system if it's one of the following:
a condition in your legal point of discharge certificate
a condition in your Planning Permit.
An OSD system temporarily stores stormwater runoff from a property, then releases it into the council drain network at a controlled rate.
Stormwater runoff is rainwater that runs off surfaces such as roads, roofs, driveways and buildings.
OSD systems are often needed on land where there are lots of hard surfaces that stop the stormwater from being absorbed into the ground - for example, multi-unit developments.
To build an OSD system, you need to:
- Submit your designs to us for approval.
- Request an inspection of the completed OSD system.
Follow our OSD system design requirements to ensure your system follows our regulations. This will help minimise any delays in approving your design.
Documents required for application
Include the following documents with your application:
- drainage design plans
- drainage computations
- approved landscape plans
- current copy of the Certificate of Title.
How to apply
This application has 2 fees*:
- A design assessment fee, calculated according to the number of units
- An inspection fee of $143.00.
Design assessment fees
After you apply
We might contact you if there's information missing from your application. When we have all the required information, we will process your application within 4-6 weeks.
We will assess your designs to check they are consistent with the legal point of discharge.
If you need to make any changes to your designs, we will send you an email.
You can send your amended designs back to [email protected]
Request an inspection
Request an inspection of the completed OSD system so we can check it complies with the approved designs.
Provide the following items when requesting the inspection:
- The reference number for your approved OSD designs, found on your OSD assessment approval letter
- Photo of the orifice plate (the metal plate attachment with a hole that controls the flow of stormwater)
- Photo of the trash grate (the mesh grate that captures obstructions such as leaves, sticks or rubbish).
Once you have submitted the request, we will contact you within 10 business days to confirm a time.
If we find any issues during the inspection, we will ask you to make the necessary changes and request another inspection.
Depending on the changes you need to make, we may charge you for another inspection.
A Certificate of Occupancy can only be signed once the OSD system has passed inspection.