Acid sulfate soils hold iron sulfides. Left wet and undisturbed they do no harm. Dug out or drained, they let air reach the sulfides and sulfuric acid forms, and that acid can harm waterways and plants and eat into concrete and steel.
In New South Wales they lie mostly on low coastal land close to sea level, in and around every estuary, and the largest areas are on the northern coastal floodplains. Some inland waterways have them too.
Councils map these soils by class on an Acid Sulfate Soils Map in their local environmental plan. The class says how deep the soils are expected to be, and so how deep works can go before consent is needed. As one plan sets it out, in summary:
Class 1 is the most constrained and class 5 the least. On class 3 land, for example, the question is whether works go deeper than a metre, as a basement or a pool may.
Our report prints the class exactly as the plan's map records it.
In summary, where the clause applies the council cannot grant consent for the works until it has an acid sulfate soils management plan prepared under the Acid Sulfate Soils Manual. Consent is not needed under the clause at all if a preliminary assessment under the same manual shows that no management plan is needed and the council confirms that in writing. Some emergency and routine works by public authorities are also excepted.
That is a summary of clause 6.1 of the Warringah Local Environmental Plan 2011, not its wording. Councils that map these soils carry a clause of this kind among the local provisions of their own plan, and the clause in that plan is the one that applies. The section 10.7(2) certificate names the plan, and must also disclose any council or public authority policy restricting development because of acid sulfate soils.
For a New South Wales address the report reads the plan's acid sulfate soils map against the whole lot, not just the address point, and prints the class with the map's currency date. Where only part of the lot is mapped it says so and gives the share; where mapped land only meets the boundary as a sliver, it says that rather than calling the land clear.
A class is a planning category, not a soil test. The report does not say whether acid sulfate soils are actually present or at what depth, or whether a particular pool, basement or drain needs a preliminary assessment; a soils assessment does. Where it says no class is mapped, that is a statement about the map over this lot. Not every council has made one, so it is not a finding that the soils are absent: why an unmapped result is not a clear one. The acid sulfate soils map shows each council's share of addresses on a lot mapped Classes 1 to 4, and the council pages list what else is mapped.
Check an addressReports from $9.90 including GST, paid once. The price belongs to the jurisdiction the address is in; the check is free and tells you the exact total for your address, and which registers cover it, before you pay anything.
Acid sulfate soils are naturally occurring sediments that hold iron sulfides and form sulfuric acid when excavation or drainage exposes them to air. In New South Wales they are found in coastal estuaries and on low-lying land, and along some inland waterways.
Local environmental plans map land by class, commonly classes 1 to 5, according to how deep the soils are expected to be: from the surface in class 1 to more than 2 metres down in class 4, with class 5 covering land within 500 metres of class 1 to 4 land. Under the usual form of the clause, consent is required for works below the depth set for the class, or likely to lower the watertable, unless a preliminary assessment shows that no acid sulfate soils management plan is needed and the council confirms that in writing.
Adapted from the NSW Department of Climate Change, Energy, the Environment and Water, © State of New South Wales (Department of Climate Change, Energy, the Environment and Water) 2024, and from the NSW Planning Portal's EPI Acid Sulfate Soils dataset, © State Government of NSW and NSW Department of Planning, Housing and Infrastructure 2018. Both CC BY 4.0: https://creativecommons.org/licenses/by/4.0/
General information about New South Wales registers. Not legal, planning or valuation advice for any particular property.