Acid Sulfate Soils and Pool Excavation NSW

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On acid sulfate soils land, the excavation itself needs development consent. Coffs Harbour maps five classes: any works on Class 1, works beyond 1 metre below ground on Class 3, beyond 2 metres on Class 4. A pool is typically 1.5 metres deep, so most coastal pools cross the line and add 3–10 weeks.

The short answer

The trigger is depth, not the pool. Local environmental plans set a depth below natural ground surface for each class, and excavating past it requires development consent in its own right — the same way a flood or heritage overlay does.
Class 3 land triggers at 1 metre. A standard pool is 1.2 to 1.8 metres deep, so on Class 3 land essentially every inground pool crosses the trigger.
A preliminary assessment by a qualified environmental consultant is generally required, and a management plan if acid sulfate soils are actually found.
This is what takes a coastal pool off the complying development path and onto a full development application — the difference between 10–20 business days and 6–10 weeks.
The same five-class structure appears up and down the coast. Coffs Harbour uses clause 7.1 of its 2012 LEP; Port Macquarie-Hastings uses Part 7 of its 2011 LEP.

Acid sulfate soil classes and the depth that triggers development consent — City of Coffs Harbour LEP 2012, clause 7.1
Class	What triggers consent	What that means for a pool
Class 1	Any works	Consent required regardless of depth. Even a shallow plunge pool or a spa
Class 2	Works below the ground surface, or works by which the water table is likely to be lowered	Any excavation at all. A pool always qualifies
Class 3	Works beyond 1 metre below the natural ground surface, or lowering the water table beyond 1 metre	A pool at 1.2–1.8m deep crosses this on virtually every design
Class 4	Works beyond 2 metres below the natural ground surface, or lowering the water table beyond 2 metres	A standard pool may sit under this; a deep end, a spa or a plant pit may not
Class 5	Works within 500 metres of Class 1, 2, 3 or 4 land that are likely to lower the water table below 1 metre AS on adjacent land	You can be caught without your own land being mapped
Assessment required	A preliminary assessment by a suitably qualified environmental consultant is generally required	A report and a consultant's fee before the application is complete
If acid sulfate soils are found	A management plan setting out how the soil will be managed, prepared in accordance with the Acid Sulfate Soils Manual	For minor works, Coffs Harbour allows a self-developed plan through an online form
Effect on the pathway	Development consent, not complying development	6–10 weeks instead of 10–20 business days

What acid sulfate soils actually are, and why councils care

Acid sulfate soils are naturally occurring coastal sediments containing iron sulfides. Left waterlogged and undisturbed they are inert. Dig them up, expose them to air, and the sulfides oxidise and produce sulfuric acid, which can mobilise aluminium and iron, kill fish, corrode concrete and steel, and damage the very pool structure being installed.

That is why the control is on the excavation rather than on the building. A council assessing a pool on acid sulfate soils land is not assessing whether you may have a pool. It is assessing what happens to several cubic metres of disturbed sediment and to the water table beneath it.

Two consequences follow, and both cost money before anything is dug. The excavation becomes an activity requiring consent in its own right, which changes the approval pathway. And the spoil becomes material that may need managing rather than simply carting away — which is a line item your excavation quote may not have priced.

Why a pool crosses the trigger when a house extension does not

This is the part that surprises people. A slab-on-ground extension disturbs a few hundred millimetres of soil. A pool goes down 1.2 to 1.8 metres and takes out the volume of a small room.

On Class 3 land — very common along the NSW coastal strip — the trigger is works beyond 1 metre below the natural ground surface. Every inground pool clears that. On Class 4 the trigger is 2 metres, which a standard pool may sit under, but a deep end, a spa footing or an equipment pit will not. On Class 2 the trigger is any works below the ground surface at all, and on Class 1 it is any works.

Class 5 is the one people miss entirely. It captures works within 500 metres of Class 1 to 4 land where the water table on that adjacent land is likely to be lowered below 1 metre AS. Your block need not be mapped for the clause to reach you.

On the NSW coast the question is not whether your pool is allowed. It is whether digging the hole is a development in its own right — and past one metre on Class 3 land, it is.

What it does to the approval pathway, and to the calendar

This is the practical cost, and it is measured in weeks rather than dollars.

A straightforward pool on unconstrained land can usually go through a fast-track pathway — a complying development certificate from a private certifier, typically issued in 10 to 20 business days. Where the excavation requires development consent under an acid sulfate soils clause, that pathway is not available and the application goes to council as a development application, commonly 6 to 10 weeks and longer where reports are requested or neighbours notified.

Add the preliminary assessment before lodgement. A suitably qualified environmental consultant is generally required to assess the site, and if acid sulfate soils are found, a management plan prepared in accordance with the Acid Sulfate Soils Manual must be provided to the consent authority before consent can be granted. For minor works Coffs Harbour allows a self-developed plan through its online form, which is the cheaper route where it applies.

We are not publishing a cost for the consultant's assessment. It is a competitive professional service, it varies with site size and sampling depth, and no council or regulator publishes a figure. Get two quotes for it the same way you would for the pool.

Acid sulfate soils are one of several things that quietly move a pool into the slow lane — flood mapping, heritage, bushfire, easements and steep slopes do the same. Do you need council approval for a pool covers the full list, and why a pool build takes longer than quoted puts the weeks in sequence.

Where this applies, and how to check before you buy

The five-class structure is not unique to one council. City of Coffs Harbour uses clause 7.1 of its Local Environmental Plan 2012; Port Macquarie-Hastings uses the same Class 1 to 5 structure in Part 7 of its LEP 2011; the pattern repeats through coastal local environmental plans across New South Wales, including the Hunter, the Mid North Coast, the Northern Rivers and estuarine parts of Sydney.

How to check your own block, free, before you commit:

Get the planning certificate for the property. Acid sulfate soil class is a matter routinely disclosed on it.
Check your council's acid sulfate soils map, which is a mapped layer of the local environmental plan.
Read the clause number your council's LEP uses — it is clause 7.1 in Coffs Harbour, Part 7 in Port Macquarie-Hastings, and 6.1 in some others — and read the depth trigger for your class.
Compare that depth with the deepest point of the pool you want, including plant pits and spa footings, not just the pool floor.

If you are buying a coastal property with a pool in mind, do this before exchange. It does not usually stop the pool, but it changes the timeline by weeks and adds a consultant's report to the budget — and both are much easier to accept before you own the block than after.

Common questions

Does acid sulfate soil mean I cannot have a pool?

Almost never. It means the excavation requires development consent and, generally, a preliminary assessment by a suitably qualified environmental consultant. City of Coffs Harbour explains the class structure and the assessment requirement on its development on land with acid sulfate soils page. What changes is the pathway and the timeline, not the answer.

How deep is a standard swimming pool?

Typically 1.2 metres at the shallow end and 1.8 metres at the deep end, so 1.5 metres is a reasonable planning figure. That is above the 1 metre Class 3 trigger and below the 2 metre Class 4 trigger — which is exactly why the class on your planning certificate matters so much.

Who pays for the acid sulfate soils assessment?

You do, as the applicant, unless your builder has included it. Check whether the quote lists it — it is one of the reports most commonly missing from a pool quote on a coastal block, and its absence is not a saving. See what should be in a pool quote.

Is this the same as a contaminated land issue?

No. Acid sulfate soils are naturally occurring, not the result of contamination, and they are managed under the local environmental plan rather than the contaminated land framework. Councils often publish both topics on the same page, which is where the confusion comes from.

Sources

General information only, current at 2026-09-07. Pool rules differ by state and by council, and penalty amounts are updated regularly. Confirm your own obligations with your council or a registered inspector before acting.

Acid sulfate soils and what they do to a pool excavation