BlueFactor Calculator Explained: What Replaced STORM in Victoria
Planning a new driveway, a multi-dwelling carpark or a residential subdivision in Victoria? You'll probably be asked to run a BlueFactor calculator now, not the old STORM tool. STORM was retired on 14 October 2025, and DEECA replaced it with BlueFactor, built on the Microburst rainfall model, as the default stormwater assessment for sites under one hectare. Bigger job? If your development has more than 5000m² of gross floor area, you're still in MUSIC modelling territory, not BlueFactor. Below we go through what actually changed, which tool applies to your job, and where a permeable concrete driveway or carpark fits into either assessment.
What Is the BlueFactor Calculator?
BlueFactor is the stormwater management assessment tool Victorian councils now point applicants to for most small-to-medium developments: driveways, single dwellings, townhouse and unit developments, small commercial sites. It replaced STORM, the standard tool for planning permit stormwater conditions for years, before that tool was decommissioned on 14 October 2025. Where STORM relied on older rainfall data, BlueFactor uses the newer Microburst rainfall model.
So if a council or your planning permit references a stormwater management score or a STORM rating, that requirement now points to the BlueFactor calculator instead. Exactly how it scores a site is set out in DEECA's own documentation at bluefactor.com.au and your local council's planning pages: inputs, weightings, pass thresholds. We'd rather send you there for the precise numbers than guess at them here.
Why STORM Was Retired
The headline change with BlueFactor is its move to the Microburst rainfall model, a newer rainfall dataset feeding the assessment, not a different philosophy about what counts as good stormwater management. If you've used STORM on a past project, the concepts carry over: reduce runoff, treat or detain what leaves the site. The tool and its numbers, though, don't.
BlueFactor vs MUSIC: Which One Do You Need?
This is the question we get asked most on site. The short version, based on current guidance:
- Sites under roughly a hectare, most driveways, dwellings and multi-unit developments: the BlueFactor calculator is the tool your council or certifier will expect.
- Developments with more than 5000m² of gross floor area: MUSIC modelling is still the required approach. BlueFactor doesn't replace MUSIC for larger commercial and mixed-use sites.
Not sure which bracket your project sits in? Have that conversation with your town planner or the council's duty planner before you get too far into design. It changes what your civil or stormwater engineer needs to produce.
Where Permeable Concrete Fits
Whichever tool applies, the underlying goal is the same: less impervious area, less fast runoff leaving the site. That's exactly what permeable concrete is built to do. Rather than sealing rainfall into a fast sheet of runoff, a permeable concrete driveway or carpark lets water pass straight through the slab, typically 20–26% void content, into a prepared stone base, where it's detained or infiltrates to the subsoil.
We won't promise a permeable concrete pour will hit a specific BlueFactor calculator score sight-unseen. That depends on your site's total impervious area, soil conditions, base design and what else is on the property. What we can say is that permeable surfacing is a recognised way to cut the impervious footprint both BlueFactor and MUSIC assess against, and it can be the difference between needing a detention tank or rain garden and not needing one at all. Get your civil engineer or certifier to model the permeable area into the assessment before you finalise the design; that's the only way to know the actual number. You can read more about how the pavement itself is built on our permeable concrete page.
Where We See This on Real Projects
This exact question comes up most often on the project types we pour every month: multi-dwelling carpark pours for townhouse and unit developments, and driveway packages for residential unit sites going through a planning permit. Both sit squarely in the size bracket where BlueFactor, not MUSIC, is the relevant tool. And both are jobs where swapping a section of pavement to permeable concrete gives the stormwater engineer more room to work with. You can see examples of both carpark and driveway work in our projects gallery.
Keeping the Benefit Over Time
Here's one thing no stormwater calculator accounts for: permeable concrete only keeps performing if it's maintained. Sediment, leaf litter and general grit build up in the surface voids over time, and in a high-sediment setting, an unmaintained surface can lose most of its infiltration capacity within a few years. Regular vacuum sweeping keeps it working. Never a rotary broom, that just pushes debris into the voids. A pressure wash followed by vacuuming recovers most lost capacity if it's been neglected. Whatever figure your engineer used when the site was modelled assumes the surface keeps draining the way it was designed to.
FAQs
Do I need the BlueFactor calculator or MUSIC for my job?
If your development is under roughly a hectare and doesn't exceed 5000m² of gross floor area, expect BlueFactor. Larger or more complex developments over that GFA threshold still need MUSIC modelling. Check with your council or certifier if you're near the line.
What happened to the STORM rating tool?
STORM was decommissioned on 14 October 2025 and replaced by BlueFactor, the DEECA tool that uses the newer Microburst rainfall model.
Will a permeable concrete driveway guarantee I pass my BlueFactor assessment?
No, there's no guaranteed number without your engineer modelling your specific site. What we can say is that permeable paving reduces effective impervious area, which is the input both BlueFactor and MUSIC score against. Check our FAQs for the maintenance and design questions we get asked most.
If you're weighing up permeable concrete for a job going through a BlueFactor or MUSIC assessment, give us a call on 1300 010 499 and we'll talk it through with you.