How to read a section 10.7 certificate for ground hazards NSW

A section 10.7 planning certificate in New South Wales tells you which planning controls and hazard overlays a council has attached to a lot, including acid sulfate soils, landslip, filled land and flood. It does not tell you the ground conditions. Shirley and Ingles (2002), writing about building on landslip-prone land, made the point about council hazard maps generally: they identify the hazards of an area so the council can set what further study it needs before approving development. They do not measure the risk on your lot. Read the certificate as a list of questions the site investigation will have to answer.

If you are buying, a 10.7(2) certificate is usually attached to the contract for sale; otherwise order one from the council for the lot, or through the NSW Planning Portal. The 10.7(2) part covers the matters the regulations prescribe, including zoning, the planning instruments that apply, mine subsidence, flood-related development controls, bush fire prone land and any council policy restricting development because of hazards such as landslip, acid sulfate soils, subsidence or contamination. A 10.7(5) part adds other relevant information the council holds and chooses to include, and some councils record filled land or past geotechnical reports only there, so for a hazard check ask for the full 10.7(2) and (5) certificate. Have the LEP (Local Environmental Plan) name to hand, because most entries point back to a clause or map in it.

Step 1: Is it the right lot and the right LEP?

Check the certificate names the correct lot and deposited plan, and note which LEP it cites, for example Wollongong LEP 2009 or Lake Macquarie LEP 2014. Every hazard entry is read against that LEP and its maps. A certificate reflects the controls on the date it was issued, so if it is more than a few months old, order a fresh one before you commit.

Step 2: What does the zoning allow?

Find the land zone (for example R2 Low Density Residential or RU1 Primary Production) and what development it permits with or without consent. This decides whether your build is allowed at all. It says nothing about the soil: a residential zone on a floodplain still carries the flood and, often, the acid sulfate constraints below.

Step 3: What does the acid sulfate soils class mean?

Look for the acid sulfate soils clause, usually citing the LEP acid sulfate soils map and a class from 1 to 5. Class 1 is the most constrained: any works need consent. Classes 2 to 4 need consent for works below the natural ground surface (Class 2), more than 1 metre below it (Class 3) or more than 2 metres below it (Class 4), or works likely to lower the water table to those depths. Class 5 covers land within 500 metres of Class 1 to 4 land, where works likely to lower the water table below 1 metre AHD on adjacent Class 1 to 4 land that is below 5 metres AHD need consent. The acid sulfate soils guide has the full class table.

These soils produce sulfuric acid once the iron sulfides in them are exposed to air, and the acid corrodes concrete and steel. On a site south of Nowra, Batchelder (2012) found the acid sat in the silt and clay of the alluvium rather than the sand, and that carting excavated soil off site was costly even after neutralising.

A Class 5 entry looks minor but can still bring a management plan if you excavate below a trigger level or dewater. Read the clause, not just the class number.

Step 4: Is the land mapped for landslip?

On hillside land, look for a landslip, slope instability or hazard-map entry. NSW councils carry these because planning law requires a consent authority to consider whether a site is exposed to hazards such as landslip when it decides a development application, and most councils do it through a planning instrument with a hazard map (Shirley and Ingles 2002).

If the lot is mapped, expect a geotechnical risk assessment as a condition of consent, and footing and drainage design suited to the slope. Shirley and Ingles note that slow soil creep, around 0.1 to 3 mm a year, can usually be designed for, by founding below the moving soil and controlling surface and subsurface water. Faster landslides are much harder to design against. The certificate flags the hazard; it never says which kind you have.

Step 5: What do the flood, mine subsidence and filled-land entries mean?

Flood. A yes on flood-related development controls means the LEP flood planning controls apply, which usually set minimum floor levels and building materials. The flood level itself normally comes from a separate flood information request to the council.

Mine subsidence. Land in a declared mine subsidence district needs Subsidence Advisory NSW approval for most building work, and the footing design has to allow for it.

Filled land. Look for any note about filled or reclaimed land, under the hazard policies entry or in the 10.7(5) advice. This is the entry that most often changes the footing scope, because fill behaves differently from the natural profile beneath it. The certificate rarely gives the depth, age or compaction of the fill. Whether it is engineered or uncontrolled fill is left for you to establish, and that distinction can move the site class.

Step 6: Does the geology agree with the certificate?

The certificate is a planning document, not a soils document. Cross-check every hazard entry against the published geology and soil landscape maps. They do not always agree with each other or with the overlay. At Bulli, Batchelder (2012) found the acid sulfate soils map, the geological map and the soil landscape map gave three different pictures of one site, and hand-auger samples found acid sulfate soil in a patch of swamp the overlay had not put on the site.

Acid sulfate rock is a separate, rarer problem that the LEP soils map does not cover. It has turned up in Hawkesbury Sandstone in a Sydney road tunnel, where sulfate growth cracked and debonded the shotcrete lining (Hunter 2025), and in dacite cuttings on the Federal Highway near the ACT border (Bridgement 2017). It matters mainly for deep cuts and basements.

Step 7: What field work does each entry trigger?

List each hazard the certificate flags and write next to it the field work it will need:

Certificate entry	What it flags	What it triggers
Acid sulfate soils, Class 1 to 5	Potential sulfide-bearing soils	Sampling, lab testing, management plan
Landslip / slope hazard	Mapped instability	Geotechnical risk assessment
Filled land	Fill of unknown depth or quality	Boreholes into and below the fill
Mine subsidence district	Land over past or present coal workings	Subsidence Advisory NSW approval and design requirements
Flood-related development controls	Flood planning controls apply	Floor level and materials controls

The certificate says nothing about cost or depth. A desktop review of geology, soil landscape, bore records and mapped hazards is the cheapest way to scope the field work before you commission it.

A desktop report pulls the same geology, soil landscape, groundwater and mapped-hazard layers into one place so you can read them against the certificate. Generate a desktop report for the address before you order the site classification, or see a sample report to check what it contains.

LayeredGeo compiles geology, soils, groundwater and site data into an automated geotechnical desktop report for any address in Queensland, New South Wales, Victoria and South Australia.

Sources

• Nicholas Bridgement (2017). Managing the risks associated with acid sulfate rock in NSW road projects. Australian Geomechanics, Volume 52, Number 4 (Dec 2017). geomechanics.org.au
• Bob Batchelder (2012). Acid sulphate soils and rocks – occurrence and management in the Illawarra Region. Australian Geomechanics, Volume 47, Number 1 (Mar 2012). geomechanics.org.au
• Andrew Hunter (2025). Management of acid sulfate rock in a Sydney road tunnel. Australian Geomechanics, Volume 60, Number 1 (Mar 2025). geomechanics.org.au
• Andrew F Shirley and Owen G Ingles (2002). Building In Areas Of Landslip, Subsidence & Rockfall. Australian Geomechanics, Volume 37, Number 3 (Jun 2002). geomechanics.org.au

About this article. Published by LayeredGeo and written from the published research cited in the Sources section above. It is general information about how property and ground conditions are assessed in Australia, not engineering, planning, legal or financial advice, and it is not specific to any property. Check anything that matters against the source dataset or a suitably qualified professional before you rely on it. If you spot something wrong, tell us at hello@layeredgeo.com.au and we will fix it.

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