Who needs this system

You need a stormwater detention system if your property:

  • has many hard surfaces that stop stormwater absorbing into the ground
  • is a multi-unit development.

A stormwater detention system temporarily stores stormwater from your property. It then releases it into our drain system at a controlled rate. 

A stormwater detention system can also be called an onsite detention system or OSD. 

Before you apply

We recommend you send a general enquiry to our drainage team before you complete your designs.

This helps to make sure there are no delays when you submit your application.

You should include the:

  • site coverage
  • total site area
  • roof area
  • paved areas
  • landscaped area.

Send your enquiry to [email protected].

We will respond within 10 working days and confirm your:

  • detention volume storage requirement
  • permissible site discharge.

You must include these in your designs.

How to apply

Once we have confirmed your requirements, you:

  • apply for a certificate
  • provide a design that meets our requirements.

Use our onsite detention system (OSD) online form:

Apply to build an OSD system

Include in your application:

  • the drainage design plans
  • how you will achieve the required volume of storage
  • how you will limit the flow rate of permissible site discharge
  • approved landscape plans
  • your Certificate of Title-external site.

We will:

  • send you an email or SMS to confirm your application
  • process your application within 4-6 weeks.

You can start building your stormwater detention system when you receive your certificate from us.

Application fees

Inspection fee: $148.50.

Design assessment fee:

  • $143 for single dwelling, or additional dwelling on a lot, 1-3 units
  • $286 for 4-10 units
  • $572 for 11 units or more, or commercial properties.

Fees do not incur GST.

Design requirements

Follow these requirements to make sure your stormwater detention system meets our regulations.

  • Your building envelope-external site must match the plans approved in your permit.
  • Your design must show existing and proposed trees and tree protection zones.
  • Your design must show easements on the property.
  • Your design must include the volume of storage needed, confirmed by our drainage team.
  • Your design must include the permissible site discharge, confirmed by our drainage team.
  • You must comply with the legal point of discharge requirements.
  • Your design must include a site survey that confirms levels of existing services within or near the site.
  • Your design must comply with AS/NZS 3500.3.
  • Your proposed control pit must comply with Council Standard drawing SD999.
  • Above-ground water tanks must not be used for stormwater detention.
  • Groundwater from a basement, or excavation works more than 1.2 m in height, must not be drained into laneways, kerbs and channels.

Request an inspection

After you build your stormwater detention system, you must request an inspection.

We will check that the system complies with the approved designs.

You will need this for your Certificate of Occupancy-external site.

Use our online form:

Request an inspection

Include in your request:

  • the reference number for your approved designs (found on your approval letter)
  • a close-up photo of the orifice plate (the metal plate attachment with a hole that controls the flow of stormwater)
  • a close-up photo of the trash grate (the mesh grate that catches leaves, sticks or rubbish).

We will contact you within 10 business days to confirm a time.

If we find issues during the inspection, you need to:

  • make changes
  • request another inspection
  • pay another inspection fee, depending on the changes needed.

More information

Call us on (03) 9278 4444 or email [email protected].

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