In Brief
The assessment can usually begin once current architectural plans show the site boundary, building roofs, driveways, paving, landscaping and the proposed location of any stormwater treatment measures.
The assessor will generally need:
- the project address and development description;
- a current site plan;
- a roof plan;
- the total site or assessment area;
- roof, driveway and other impervious areas;
- landscaped and permeable areas;
- rainwater tank capacities and connected roof catchments;
- proposed rainwater reuse demands;
- details of raingardens, permeable paving or other treatment measures; and
- relevant council correspondence or permit conditions.
The drawings do not always need to be fully resolved before work begins. However, the assessment should be reviewed when later changes affect the measured areas, runoff connections or treatment strategy.
Preparing the Project Information
A STORM assessment translates the physical design shown on the project drawings into a quantitative stormwater treatment model.
To do this accurately, the assessor needs to understand:
- the boundary of the area being assessed;
- which surfaces generate stormwater runoff;
- which surfaces remain permeable;
- where runoff from each catchment is directed;
- which treatment measures receive that runoff;
- how rainwater will be stored and reused; and
- which parts of the site remain untreated.
Not every detail needs to be final at the start. The plans must nevertheless contain enough information to support a realistic treatment strategy.
For a broader explanation of STORM reports and Victorian treatment assessments, visit the Certified Energy STORM Knowledge Hub.
1. Project Address and Development Description
The initial information should identify the property and the type of development proposed.
This commonly includes:
- the full street address;
- the relevant lot or title details where available;
- the local council;
- the proposed development type;
- the number of dwellings or buildings;
- whether the project is new construction, an extension or redevelopment;
- the planning application or permit reference, if known; and
- the project contact or consultant responsible for coordination.
This context helps establish the likely assessment boundary and allows the report to be tied to the correct project and drawing set.
2. Current Site Plan
The site plan is usually the most important drawing for a STORM assessment.
It should show, as far as available:
- the property boundary;
- site dimensions;
- existing and proposed buildings;
- driveways and vehicle access;
- car parking and turning areas;
- paths, patios and courtyards;
- landscaped areas;
- private open space;
- rainwater tank locations;
- raingardens or other treatment areas;
- permeable paving; and
- other major external surfaces.
A dimensioned plan or scaled PDF is preferable because it allows the various surface areas to be measured accurately.
Where only an image or unscaled concept plan is available, additional dimensions or area schedules may be needed.
3. Roof Plan
The roof plan helps establish the roof catchments available for rainwater harvesting.
It can also reveal whether different parts of the roof are likely to drain in separate directions.
Useful roof information includes:
- the outline of each roof section;
- roof levels;
- ridges and valleys;
- gutters and drainage directions where known;
- garage, carport or outbuilding roofs;
- balcony or terrace areas;
- downpipe locations where available; and
- the rainwater tank intended to receive each catchment.
The complete roof area should not automatically be assigned to one tank. Only roof sections that can realistically drain to that tank should be included as connected catchment.
4. Total Site or Assessment Area
The assessment needs a clearly defined total area against which the individual surface types can be checked.
This will commonly be the title area or another project boundary established for the assessment.
The total should reconcile with the sum of:
- roof areas;
- driveways and parking;
- paths and conventional paving;
- permeable paving;
- landscaped areas;
- other pervious surfaces; and
- any existing areas included within the assessment boundary.
Where the sum of the entered surfaces differs materially from the total site area, the assessment may contain an omission, overlap or classification error.
5. Impervious Surface Areas
Impervious areas generate most of the runoff evaluated in a STORM assessment.
The assessor will generally need to identify:
- dwelling or building roofs;
- garage and carport roofs;
- balconies and terraces;
- driveways;
- car parking spaces;
- turning areas;
- pedestrian paths;
- patios and courtyards;
- bin storage pads;
- pool surrounds where relevant; and
- other sealed surfaces.
Small surfaces should not be ignored simply because they are individually minor. Collectively, paths, porches and other paved areas can affect the overall treatment result.
6. Landscaped and Permeable Areas
The assessment also needs to distinguish surfaces that remain pervious or form part of the proposed treatment response.
Relevant information may include:
- garden beds;
- lawns;
- deep-soil areas;
- general landscaped areas;
- permeable paving;
- gravel or other permeable finishes;
- raingardens;
- biofiltration areas; and
- other infiltration or treatment zones.
The classification should reflect the actual proposed construction.
Conventional concrete or tightly jointed paving should not be counted as permeable solely because it is located outdoors.
7. Rainwater Tank Capacity
Where rainwater harvesting forms part of the treatment strategy, the assessor needs the proposed storage capacity of each tank.
The information should identify:
- the capacity of each tank in litres;
- whether the stated capacity is total or usable storage;
- the number of tanks;
- which dwelling or building each tank serves;
- whether tanks operate separately or as a connected system;
- the proposed tank location; and
- any relevant dimensional or access constraints.
If the tank size has not been selected, the assessment can test practical alternatives. The final nominated capacity should then be carried into the architectural and hydraulic documentation.
8. Roof Area Connected to Each Tank
Tank capacity alone is not enough to model rainwater harvesting.
The assessor must also know how much roof runoff reaches each tank.
For a multi-dwelling project, this may require a schedule such as:
- Townhouse 1 roof area connected to Tank 1;
- Townhouse 2 roof area connected to Tank 2;
- Townhouse 3 and garage roof connected to Tank 3; and
- remaining roof area discharging without tank treatment.
Where the exact downpipe arrangement is not yet designed, a reasonable preliminary catchment can be tested. It should still be physically achievable based on the roof form and proposed tank location.
9. Proposed Rainwater Reuse
The assessor needs to understand how stored rainwater will be drawn from the tank.
Possible reuse demands may include:
- toilet flushing;
- landscape irrigation;
- laundry use where relevant and accepted;
- external washdown; or
- another credible non-potable use.
For residential projects, it is also useful to confirm:
- the number of dwellings served;
- the number of toilets connected;
- the landscaped area intended for irrigation;
- whether tanks are individual or shared; and
- whether the reuse commitments are shown on the plans or hydraulic notes.
Reuse assumptions should represent the system that will actually be constructed. They should not be added to the model without corresponding design commitments.
10. Raingarden or Biofiltration Information
Where a raingarden is proposed, the assessment needs enough information to represent its treatment area and connected runoff catchment.
Useful details include:
- the proposed raingarden location;
- the available treatment surface area;
- the roof, driveway or paving that drains to it;
- how runoff enters the treatment area;
- whether an overflow or underdrain is proposed;
- relevant site levels where available; and
- any landscape or construction details already prepared.
Raingardens are designed to filter runoff using vegetation, soil and biological treatment processes. The treatment area used in the model must therefore correspond with a real and buildable part of the site. :contentReference[oaicite:1]{index=1}
11. Permeable Paving Information
If permeable paving contributes to the treatment result, the assessor will need to know:
- the exact area proposed as permeable;
- its location;
- the intended pavement system;
- whether adjoining runoff also drains onto it;
- whether infiltration is proposed;
- any known soil or groundwater constraints; and
- whether the architectural or landscape specification identifies it as permeable.
A general note stating “permeable paving where possible” is usually not enough to establish a measurable treatment area.
12. Runoff Connections and Drainage Intent
The assessment does not necessarily require a complete hydraulic design, but it does need a credible understanding of where runoff goes.
Helpful information may include:
- roof drainage directions;
- downpipe locations;
- driveway falls;
- surface drainage directions;
- the intended path from each catchment to its treatment measure;
- tank overflow locations;
- raingarden overflow arrangements; and
- any available drainage concept plan.
Where these details are not yet designed, the assessor may identify assumptions that need to be confirmed during later hydraulic or civil coordination.
13. Council Correspondence
Council correspondence can be as important as the drawings because it helps clarify why the assessment is being requested.
Relevant documents may include:
- a planning application checklist;
- pre-application advice;
- a request for further information;
- a planning permit condition;
- comments from a council ESD officer;
- drainage or engineering comments;
- a planning officer email;
- a referral authority response; and
- an existing endorsed stormwater condition.
The wording can help determine whether council expects a focused treatment assessment or a broader package that also addresses drainage, detention, discharge or maintenance.
14. Planning and Property Information
Depending on the project, it can also be useful to provide:
- a planning property report;
- the relevant planning controls;
- the development application description;
- an existing planning permit;
- the town planning report;
- a BESS, SDA or SMP request where applicable; and
- other site-specific water-management requirements.
This material helps place the assessment within the correct planning context without turning the STORM report into a broad planning or sustainability document.
15. Landscape Plans
A landscape plan is particularly useful where the treatment strategy includes:
- raingardens;
- biofiltration areas;
- irrigated gardens;
- permeable paving;
- passive irrigation;
- deep-soil areas; or
- other landscaped treatment measures.
The plan helps confirm that sufficient physical space remains available and that the modelled treatment areas do not conflict with access, services, tree planting or private open space.
If the landscape plan has not yet been prepared, the architectural drawings should at least reserve the required treatment area.
16. Available Hydraulic or Civil Information
Detailed hydraulic or civil drawings are not always required before a STORM assessment can begin.
Where available, they may help confirm:
- downpipe and gutter connections;
- tank inlet and overflow arrangements;
- toilet and irrigation reuse connections;
- driveway drainage;
- pit locations;
- the legal point of discharge;
- on-site detention;
- raingarden underdrains; and
- the relationship between treatment and the wider drainage system.
The presence of this information improves coordination but does not make every hydraulic calculation part of the STORM assessment itself.
Can the Assessment Start Before Final Drawings?
Yes. A preliminary assessment can often begin from developed concept plans.
This can be beneficial because it allows the project team to test:
- likely tank capacities;
- available roof connections;
- rainwater reuse options;
- the effect of driveway runoff;
- the approximate raingarden area required;
- the benefit of permeable paving; and
- whether the site has enough space for the proposed strategy.
An early assessment should be treated as preliminary where major design elements remain unresolved.
The result should be reviewed after changes to:
- the building footprint;
- roof geometry;
- driveway or parking layout;
- paving;
- landscape areas;
- tank size or location;
- reuse connections; or
- other treatment measures.
What If Some Information Is Missing?
Missing information does not always prevent the assessment from starting.
Where appropriate, a preliminary model may use clearly stated assumptions for matters such as:
- the proposed tank capacity;
- the portion of roof connected to a tank;
- toilet or irrigation reuse;
- the approximate raingarden area;
- the intended permeable paving area; or
- the routing of driveway runoff.
These assumptions should be identified for the project team and confirmed before the assessment is finalised.
The final report should not quietly rely on unverified measures that are absent from the design documentation.
Common Information Problems
Several recurring issues can delay or weaken an assessment:
- plans without dimensions or usable scale;
- no roof plan;
- unclear site boundaries;
- different tank sizes shown on different drawings;
- no indication of connected roof catchments;
- reuse included without plumbing commitments;
- landscape areas that do not reconcile with the site plan;
- permeable paving without a defined area;
- a raingarden shown without dimensions;
- superseded architectural drawings;
- missing council correspondence; and
- uncertainty about whether a simplified assessment is acceptable.
Providing the current drawing set and the exact council request at the outset usually reduces unnecessary revisions.
What Is Not Usually Needed for the Initial Assessment?
A focused stormwater treatment assessment does not normally require every aspect of the final construction package before modelling can begin.
Depending on the project, the initial assessment may not need:
- final pit and pipe sizing;
- complete civil construction details;
- final structural tank details;
- complete detention calculations;
- final finished surface levels;
- full flood modelling;
- final planting schedules; or
- all supplier product data.
Some of these items may still be required elsewhere in the planning, drainage or construction process.
The STORM assessment needs sufficient information to model treatment performance; it does not replace the separate design of every stormwater component.
STORM, BlueFactor and the Requested Output
Project correspondence may refer to a STORM assessment even where the current accepted output uses a newer assessment platform.
Before finalising the submission, it is useful to confirm:
- which assessment method council accepts;
- whether a calculator certificate is required;
- whether a written report is also expected;
- whether marked-up catchment plans are needed;
- whether the result must be shown on architectural plans;
- whether maintenance notes are required; and
- whether another consultant must address drainage or detention.
Current planning requirements can extend beyond treatment performance to retention, detention, discharge and the wider stormwater management system. The exact submission scope should therefore be read from the applicable planning controls and council request. :contentReference[oaicite:2]{index=2}
Practical Submission Checklist
Before sending a project for assessment, check whether the following items are available:
- project address;
- development description;
- current site plan;
- current roof plan;
- drawing numbers and revision dates;
- total site area;
- roof areas;
- driveway and parking areas;
- paths, patios and other paving;
- landscaped areas;
- permeable paving areas;
- tank capacities;
- roof catchments connected to tanks;
- toilet, laundry or irrigation reuse information;
- raingarden dimensions and catchments;
- available landscape plans;
- available hydraulic or civil plans;
- council requests or permit conditions; and
- any existing stormwater assessment.
Where an item is not yet available, it can be identified as a design input requiring confirmation rather than delaying all preliminary assessment work.
How Certified Energy Can Help
Certified Energy can review the available plans and identify whether there is enough information to begin a stormwater treatment assessment.
The process may include:
- reviewing the council request or permit condition;
- checking the drawing set and revision status;
- measuring roof, driveway, paving and landscape areas;
- identifying treated and untreated catchments;
- reviewing proposed rainwater tanks;
- checking connected roof areas and reuse assumptions;
- reviewing raingardens and permeable surfaces;
- identifying missing project information;
- testing preliminary treatment options where details remain unresolved;
- documenting the final treatment commitments; and
- identifying where separate MUSIC, drainage or civil engineering input may be required.
The assessment can often begin before every construction detail is final, provided the project team understands which assumptions must be retained or confirmed.
Explore the STORM Assessment Knowledge Hub or send through the current plans and council correspondence for an initial project review.
Frequently Asked Questions
What information is needed for a STORM assessment?
The assessment generally needs current plans, the total site area, impervious and landscaped surface areas, proposed stormwater treatment measures, rainwater tank information and relevant council correspondence.
What plans should I provide?
A site plan and roof plan are usually the most important. Floor plans, elevations, landscape plans and available hydraulic or civil plans may also assist.
Do the plans need to be final?
No. A preliminary assessment can often begin from developed concept plans, but the result should be checked again if the design changes.
Is a roof plan essential?
It is highly useful because it helps measure roof catchments and determine which areas can realistically connect to each rainwater tank.
What tank details are required?
The assessor generally needs the tank capacity, connected roof area, uses or dwellings served and proposed reuse demands.
Do I need a hydraulic plan first?
Not always. The assessment may begin before detailed hydraulic design where the proposed catchments, treatment measures and reuse strategy are sufficiently clear.
Should I provide the council request?
Yes. Council correspondence can clarify whether a focused treatment assessment, broader stormwater documentation or a particular modelling method is expected.
What if the tank size has not been selected?
Practical tank options can be tested during a preliminary assessment. The selected capacity should then be incorporated consistently into the project documents.
Can assumptions be used?
Reasonable preliminary assumptions may be used where details remain unresolved, but they should be clearly identified and confirmed before the final report is issued.
Are drainage calculations required?
Not ordinarily for the treatment assessment itself. Drainage capacity, detention, discharge and flood matters may need separate specialist documentation.
