A Victorian council may request a STORM assessment where a development must demonstrate how runoff from roofs, driveways, paving and other impervious surfaces will be treated.
The requirement may arise from the Victorian planning provisions, a local planning policy, an application requirement, a request for further information or a condition of planning permit.
It is not automatically required for every project. The applicable planning controls, development type, site characteristics and council expectations should be checked before deciding which stormwater assessment is needed.
Melbourne Water has also replaced the original STORM Calculator with BlueFactor. Although the term “STORM assessment” remains widely recognised, new projects may need a BlueFactor assessment or another accepted form of stormwater treatment modelling.
A request for a STORM assessment does not come from one universal rule applying identically to every Victorian development.
Instead, the requirement may arise from several parts of the planning process, including:
The project team should therefore review the planning scheme and council requirements for the particular site rather than assuming that an assessment is either always required or never required.
Clause 53.18 addresses stormwater management in urban development. Its purpose includes managing stormwater to reduce impacts on the environment, property and public safety while encouraging retention, reuse and treatment.
Where the clause applies, an application may need to include details of the proposed stormwater management system. This can include information about:
A STORM or BlueFactor assessment may help demonstrate the water-quality treatment component of this response for a suitable project.
However, a calculator result alone may not address every part of Clause 53.18. Separate drainage, detention, discharge or maintenance information may also be needed.
Stormwater treatment assessments are most commonly associated with developments that introduce or increase impervious surfaces.
Projects that may be asked to provide an assessment include:
This does not mean every project in these categories automatically requires the same report. Project size, location, permit triggers and council policy can change the required response.
Townhouse developments are frequently asked to demonstrate stormwater treatment performance because they can introduce multiple roofs, shared driveways, paths and other impervious surfaces onto a residential site.
A council may want to understand:
For these projects, a STORM-style assessment can provide a concise quantitative summary of the proposed runoff treatment strategy.
A small residential extension will not necessarily require a STORM assessment.
The likelihood may increase where the proposal:
The relevant council requirements should be checked before commissioning an assessment solely because the project includes an addition.
Commercial and industrial developments may also need to demonstrate stormwater treatment performance, particularly where they contain large roof areas, car parks, loading areas or other extensive impervious surfaces.
A simple development may be suitable for a BlueFactor assessment. A larger or more complex development may require MUSIC modelling, a broader Stormwater Management Plan or specialist civil engineering input.
The appropriate method depends on the size and complexity of the catchments and treatment measures, not simply on whether the building is residential or commercial.
The need for a stormwater treatment assessment may become apparent at several stages of a project.
The requirement may be identified through a planning scheme review, pre-application meeting, council checklist or advice from the town planner.
If the application does not adequately explain the treatment of runoff, council may issue a request for further information.
A council drainage, engineering or ESD officer may request additional calculations, plans or treatment details.
In some cases, a permit may require a stormwater treatment assessment or revised stormwater documentation before endorsed plans, construction or another nominated stage.
Completing an early requirements review can help avoid discovering the need for treatment measures after the site and landscape design have already been finalised.
A STORM-style assessment has a focused role: it quantifies stormwater treatment performance for relatively straightforward developments.
It may not be sufficient where the project includes:
In these circumstances, council may require a more detailed assessment method or supporting civil and hydraulic documentation.
A STORM assessment should not be presented as a substitute for MUSIC modelling, flood assessment, drainage design or a civil engineering report where those services are required.
Melbourne Water’s original STORM Calculator has been replaced by BlueFactor.
BlueFactor is intended to assess stormwater management for suitable small developments in Victoria. It considers development catchments and proposed treatment measures to produce an overall stormwater performance result.
The change means that project correspondence may use several different terms:
Where older permit conditions or council documents specifically request a STORM report, it may be necessary to confirm whether council will accept a current BlueFactor result.
Identifying the requirement early affects more than the report itself. Stormwater treatment measures often need to be incorporated into the architectural, landscape and hydraulic design.
For example, the assessment may identify a need for:
These measures require physical space and coordination. Leaving the assessment until the end of the planning process can result in conflicts with car parking, private open space, landscaping, services or building setbacks.
Establish whether the requirement arises from Clause 53.18, another planning provision, local policy, a permit condition or a direct council request.
Ask whether council expects BlueFactor, MUSIC or another form of stormwater treatment documentation.
The assessment may need to consider all relevant impervious surfaces, not only the new building roof.
Rainwater tanks, raingardens and permeable areas should be reflected consistently across the architectural, landscape and hydraulic plans.
Confirm whether the project also needs detention calculations, drainage plans, legal point of discharge information or civil engineering documentation.
A request for further information or permit condition often provides the clearest description of what council expects to receive.
An initial requirements review is easier when the following information is available:
These documents help determine whether a quantitative treatment assessment is needed and whether a STORM-style assessment is suitable for the project.
Certified Energy can review the available project information and help identify the appropriate scope for a Victorian stormwater treatment assessment.
This may include:
Where the project requires more detailed MUSIC modelling, drainage design or civil engineering, that broader requirement should be identified rather than treating a basic STORM assessment as a complete substitute.
Visit the STORM Assessment Knowledge Hub or send through the available plans and council correspondence for an initial project review.
It may be required when a planning application needs to demonstrate the treatment of stormwater runoff. The requirement can arise from the planning scheme, council policy, an application checklist, a request for further information or a permit condition.
No. The requirement depends on the development type, planning controls, local council expectations and proposed stormwater system.
Townhouse developments are commonly asked to demonstrate stormwater treatment performance, but the requirement should still be confirmed for the individual site.
Yes. Council may request additional stormwater treatment information if it considers that the submitted plans do not adequately demonstrate the proposed outcome.
Yes. A permit condition may require an assessment, revised treatment strategy or supporting stormwater documentation before plans are endorsed or another nominated project stage is reached.
Melbourne Water has replaced the original calculator with BlueFactor. The STORM name remains common in planning language, but the accepted assessment method should be confirmed with council.
No. Clause 53.18 establishes stormwater management objectives and application requirements, but the appropriate evidence can vary. A STORM or BlueFactor assessment may address the treatment component without necessarily addressing every drainage requirement.
Not automatically. The result depends on tank size, connected roof area, reuse demand and the treatment of other impervious areas such as driveways and paving.
No. A STORM assessment provides quantitative treatment results. A Stormwater Management Plan can be broader and may document drainage, detention, discharge, maintenance and the overall site strategy.
It is best reviewed before the design is finalised so that treatment measures can be coordinated with the site plan, landscaping, services and hydraulic design.