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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 when you submit an application.

How to apply

Once we have confirmed your requirements, you can apply for a certificate. You will need to provide a design that meets our requirements in your application.

Apply for approval for an on-site detention (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, which you can get through the Landata website.

Design assessment fee

As part of your application to build an on-site detention (OSD) system, you will need to pay:

  • $300 for 1-4 unit development
  • $700 for 5-9 unit development
  • $900 for 10+ unit development

Fees do not incur GST.

After you apply

After you submit your application, we will:

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

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

Design requirements

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

  • Your building envelope site must match the plans approved in your permit. Learn more on the Department of Transport and Planning website.
  • Your design must show existing and proposed trees and tree protection zones. Learn more on our Protect trees during construction page.
  • 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. Learn more on our Connect to the stormwater page.
  • 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 the Standard Drawing SD999 - on-site detention control pit details on our Standard drawings page.
  • 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, or if your drainage approval requires an interim inspection, 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. Learn more on the Victorian Building Authority website.

Inspection fee: $158.50 (does not incur GST)

Request an inspection

You will need to include in your request:

  • a copy of your signed endorsed and approved stormwater drainage plans
  • the reference number for your approved designs (found on your approval letter)
  • a photo of the inside of the control pit that shows the trash grate and orifice plate
  • a close-up photo of the orifice plate (the metal plate attachment with a hole that controls the flow of stormwater) with a measurement of the diameter of the orifice plate.
  • a close up photo of the sump and weepholes.

For a visual example of the photos you need to provide, use the 4 example photos on this page which show what each photo needs to contain.

a photo of the inside of the control pit that shows the trash grate and orifice plate
A photo of the inside of the control pit that shows the trash grate and orifice plate
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 orifice plate (the metal plate attachment with a hole that controls the flow of stormwater)
a measurement of the diameter of the orifice plate
A measurement of the diameter of the orifice plate
A close up photo of the sump and weepholes
A close up photo of the sump and weepholes

After you submit your request

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

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

  • make changes
  • submit another request for an additional inspection
  • pay another inspection fee.

If you cannot make the changes to meet the requirements of the approved stormwater drainage plans, you will need to submit a new application for approval of the new plans with our Drainage Team. This will be a reassessment.

You will need to pay additional fees for the reassessment, and for the new inspection booking that will be required for the altered stormwater detention system.

More information

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

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