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Contaminated Land and Acid Sulfates

Contaminated Land

The Land within the Georges River Council area has had many different uses over the years including residential, commercial and industrial land uses.

Although contaminated sites can occur anywhere, they are typically clustered in areas previously or currently used for industry.  Some of this industrial use may have occurred before strong environmental protection controls were in place or even considered necessary. 

Requirements to remediate potentially contaminated land are triggered, by the following:

Application to rezone land
  1. Rezoning of land under a new or amended LEP
  2. Development Application
  3. Voluntary remediation or
  4. Environmental Protection Authority Orders following a pollution incident.
Contaminated land can have major economic, legal and planning implications for the community. Contamination may limit land use potential or increase costs for developers. 

The investigation and clean-up of contaminated land is important to protect human health and the local environment.

Council is responsible for assessing whether a site is contaminated and is suitable for the intended use as part of the Development Application process. Council also maintains a register of contaminated sites located within the local government area. The planning and development control process under the Environmental Planning and Assessment Act 1979 (EP&A Act) is an important tool used for the management of land contamination. It aims to ensure that land is not allowed to be developed unless the presence of contamination is investigated and addressed if detected.
In accordance with the State Environmental Planning Policy No 55 - Remediation of Land, Council requires contamination assessments to be submitted with all Development Applications where:
  • The Development Application is for a childcare facility or school regardless of site history
  • The Development Application is for residential or recreational development on land which has been used for any industrial or commercial purpose
  • The site is known to have been used for a potentially contaminating use or is otherwise suspected by Council to be contaminated.

The following is a simplified guideline used to assist in determining if land is suitable for its proposed use:
Step Information to be provided Details 
1 A Preliminary Site Investigation (PSI) Report A Preliminary Site investigation (PSI) report is to be submitted with the Development Application to determine contamination (if any) from known records and or previous land use history.  

A PSI is also known as Phase I Environmental Site Assessment.
2 Detail Site Investigation (DSI) Report  If PSI requires further investigation, then a Detailed Site Investigation (DSI) report is to be submitted to Council prior to the determination of the development 

A DSI and report must be carried out by a Contaminated Land Consultant, certified under the consultant certification scheme recognised by the NSW EPA and in accordance with SEPP55 and the associated guidelines.  

A DSI is also known as Phase II Environmental Site Assessment.
3 Remedial Action Plan  A Remedial Action Plan (RAP) is a document detailing how the contaminants are going to be treated or removed from the site and is usually submitted with the DSI report prior to the determination of the development. 

A RAP must be carried out by a Contaminated Land Consultant, certified under the consultant certification scheme recognised by the NSW EPA. 

A RAP is also known as Phase III Environmental Site Assessment.
4 Site Validation Report  Site Validation Report is a document confirming that contamination has been adequately remediated.  

A Site Validation Report must be carried out by a Contaminated Land Consultant, certified under the consultant certification scheme recognised by the NSW EPA. 

Depending on the type and severity of the contamination, a Site Validation Report is required either at the Construction Certificate stage or at Prior to Occupation Certificate stage.
5 Site Audit Statement Council will require a Site Audit Statement (SAS) where: 
  • verification of information is required to ensure it adheres to appropriate standards, procedures and guidelines,  
  • it is believed on reasonable grounds that the information provided is incorrect or incomplete, and or
  • the complexity of the contamination requires an independent review.  
A Site Audit is carried out by Site Auditor who are accredited under the Contaminated Land Management Act.  
6 Environmental Monitoring Program 
An Environmental Monitoring Program (EMP) is required where clean-up of the site is not feasible and contamination requires monitoring.  

An EMP is prepared by a Contaminated Land Consultant, certified under the consultant certification schemes recognised by the NSW EPA, which addresses the manner in which site operations will be conducted and monitored.  The monitoring program usually includes (but not limited to): 
  • Details of the proposed monitoring strategy.
  • Parameters to be monitored,
  • Monitoring locations,
  • Frequency of monitoring, and 
  • Reporting requirements

Contact Council’s Duty Planner if you have any further questions regarding the development process. 


Acid Sulfates

What are Acid Sulfate Soils?

Acid sulfate soils are natural sediments that contain iron sulphides and are common along the NSW coast. Acid sulfate soils are safe and harmless when not disturbed. 

However, if the soils are drained, excavated or exposed to air by a lowering of the water table, the sulfides react with oxygen to form sulfuric acid, which can cause damage to the environment and to buildings, roads and other structures.

The acid also attacks soil minerals, releasing metals like aluminium and iron. Rainfall can then wash the acid and metals from the disturbed soil into the surrounding environment. 

The Impacts

Environmental Impacts
The acid and released metals can have many harmful effects:
  • Damaging waterways and killing aquatic life – Rainfall can wash acid and toxic metals into waterways, killing organisms that are immobile (such as oysters) or that live in sediment. It can also reduce survival and growth rates of plants and animals, and promote outbreaks of disease (especially red-spot disease in fish).
  • Killing plants – Very acidic soil can kill all plants growing in it.
  • Toxic water and dust – Acid sulfate soil and water can irritate your skin and eyes. Drinking acidic water may make animals ill.
Building Impacts
The acid and released metals can have many damaging effects including corrosion. Sulfuric acid can corrode concrete, iron, steel and some aluminium alloys

Where can it be found locally? 

The NSW government has produced maps to show where acid sulfate soils are likely to be found. If you plan any sort of excavation in areas along the waterways, you must consider the possibility of encountering acid sulfate soils. 

What can be done to prevent its damaging effects?

Minimising disturbance can be quite easy, and may involve:
  • Designing the work to limit the amount of excavation.
  • Relocating the work to part of a property where acid sulfate soils are buried deepest, so the amount of acid sulfate soil removed is reduced.
  • Using construction methods and site management procedures that don't leave acid sulfate soils exposed to air without treatment.


If acid sulfate soil is disturbed, it must be treated.

The most common method of treatment is to mix an alkaline material into the soil, where it can react with acidity to neutralise. Agricultural lime (powdered calcium carbonate—CaCO3) is the most common neutralising material in use.

While minimising and avoiding disturbance can be easy, managing it is complex and should be done by appropriately trained people.

Expert advice

Any project planned in the waterfront areas must consider engaging the services of an environmental consultant prior to commencing. 


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