What happened to STORM
Melbourne Water closed STORM to new projects in October 2025 and replaced it with Blue Factor. STORM still stands for existing applications, or for amendments to approved developments where it was already used — but a new planning application does not go in on a STORM rating.
Blue Factor is aimed at small-scale developments, up to around one hectare, and it also suits simple small commercial and public projects. That covers the overwhelming majority of planning applications.
Holding a STORM report for a project that has not lodged yet? It needs redoing in the current tool. One already attached to a lodged application, or to an approved development being amended, still has standing.
Which clause asks for it
Three provisions of the Victoria Planning Provisions ask for stormwater management, and they apply across Victorian councils:
- Clause 55.05-1 — two or more dwellings on a lot, and residential buildings of up to three storeys: townhouses and dual occupancies. Before Amendment VC267 restructured Clause 55 in March 2025, this standard was Clause 55.03-4. If a permit condition or an old report says 55.03-4, this is what it means. Today 55.03-4 is the entry standard, which has nothing to do with stormwater.
- Clause 53.18 — stormwater management in urban development. It covers applications to subdivide, construct a building or carry out works, with a list of exemptions. Among them: one dwelling on a lot, building or extending a dwelling in a residential zone, and buildings or works of 50 m² or less.
- Clause 56.07-4 — residential subdivision.
Whichever one the council names, the assessment answers it.
What the standard actually asks for
For townhouses and dual occupancies, Standard B5-1 in Clause 55.05-1 asks for:
- at least 20 per cent of the site covered by pervious surfaces;
- a stormwater system that meets the best practice objectives in the EPA’s Urban stormwater management guidance (Publication 1739.1, 2021): an 80 per cent reduction in the mean annual load of suspended solids, 45 per cent for total phosphorus and total nitrogen, and 70 per cent for litter;
- flows directed into treatment areas, garden areas, tree pits and permeable surfaces, with residual flows drained to the legal point of discharge.
The standard now says how that is shown: a certificate from a stormwater assessment tool with a Blue Factor score of at least 100 per cent, or other modelling the council accepts. For almost every townhouse application, the Blue Factor certificate is the report.
Clause 53.18 works the same way for buildings and works. Its Standard W2 points to the same EPA objectives, and adds that chemical pollutants should be kept out of stormwater — bunding and covering or roofing storage, loading and work areas — which is why commercial and industrial jobs get asked about them. Standard W3 asks how the site will be managed during construction: erosion and sediment, stormwater, litter and concrete waste, and chemical contamination.
How a Blue Factor assessment is built
The assessment is only as good as the take-off behind it. Each roof, driveway, porch and permeable surface is measured off the site plan separately, then routed to whatever treats it — one catchment per surface per dwelling. Collapsing a whole site into a single impervious number is the most common shortcut, and it is the part councils query.
Treatment measures the design already carries are assessed as specified, and sized so the result meets the target properly rather than scraping over the line. A result that only just passes is a result that fails as soon as anything on the drawings moves.
Treatment measures that hold up
Rainwater tanks: they have to be used
Melbourne Water is direct about this: tanks used only for watering gardens are much less efficient than tanks used for flushing toilets, because a tank only helps when its water is used often enough to leave room for the next rain. Connect as much of the roof as possible, and plumb the tank to toilets or the laundry.
Raingardens
Melbourne Water’s WSUD maintenance guidelines put routine checks at every three months and after storms: clear litter from the filter media, look for water still ponding after rain and for erosion, keep the mulch even, and keep the planting dense — 6 to 10 plants per square metre. Built-up sediment is removed about once a year. For a home raingarden, use gravel mulch rather than bark or straw, which float into the drains.
Permeable paving and infiltration
Permeable paving gets the same three-monthly check for sediment and ponding, with clogging material swept, wet-vacuumed or hosed out. An infiltration raingarden needs its base above the surrounding groundwater, and runoff from heavy storms should bypass it into the drainage system.
Clause 53.18 lists whether treatment areas can be effectively maintained among the things council must consider, so a measure that is easy to look after is worth more than one that only works on paper.
What to send
The site plan and the area schedule are the two that matter, plus the landscape plan if there is one and the drainage layout if it exists — the drainage layout is also where the legal point of discharge shows up. If the permit also asks for a sustainability assessment, send the conditions and both get quoted together: the BESS stormwater credit is scored from the Blue Factor result.
On larger land development, particularly new estates, Melbourne Water may ask for a Stormwater Management Strategy with the planning application. It states it responds within 45 days for a standard strategy and up to 90 days for a complex one — a separate, larger piece of work than the Blue Factor assessment most applications need.
Sources: Victoria Planning Provisions, Clauses 53.18, 55.05-1 and 56.07-4 (planning.vic.gov.au); Melbourne Water, rainwater tanks, raingardens, WSUD maintenance guidelines and stormwater management strategy review. General information, not an assessment of any particular site.