Acid sulfate soils, by suburb

225 of the 958 Australian suburbs published on this site have acid sulfate soil features mapped over them. That is a count of our own published pages, not of every suburb in the country — the corpus grows, and this page is rebuilt with it. They are concentrated where you would expect: New South Wales (186), Queensland (27), South Australia (12).

These soils generate acid when exposed to air, which is why the requirement is triggered by the depth and volume of ground disturbance rather than by the building above. A slab at natural ground level may clear the trigger entirely; a cut for a level platform, a pool, a tank base or a deep service trench will not. Where it is triggered, the work needs an investigation and then a management plan covering excavation, treatment and disposal — and treated spoil cannot simply be carted off as ordinary fill, which is where the cost sits rather than in the assessment.

The practical conclusion is the same on every one of these suburbs, and it is worth more than the count: settle how deep the design goes before an architect is briefed. Reducing the volume of disturbance is always cheaper than managing it, and on a sloping site a design that steps down on piers can satisfy the rest of the brief while barely engaging the trigger. On land zoned for large lots, the effluent disposal area is a second set of earthworks to reconcile with the same soils.

The counts below are mapped features intersecting the suburb, not a severity score and not a depth. A high count means the soils are the dominant mapped condition across that suburb; it does not tell you what sits under one parcel, which is an address-level question.