Contaminated Land

A 'Contaminated Site' is defined in the Contaminated Sites Act 2003 (CS Act) as one which,

a) contains hazardous or dangerous substances,
b) at levels above normal background levels,
c) which pose a risk to human health and the environment (values).

Hazardous substances may come from a range of human activities but are most often associated with poorly managed industrial and commercial processes. They are found in soils, sediments and water, but also as gases, dusts and radiation emitted from the site.

The term 'site' is defined in the CS Act as an area of land and includes groundwater and surface water. 

A site that has been reported under the CS Act needs to be properly assessed, classified and remediated. Technical guidelines are available on the Department of Water and Environmental Regulation (DWER) (external site)

What is Not a Contaminated Site?

As the CS Act focuses on the regulation of historic contamination, recent, ongoing or small-scale pollution incidents should, where possible be controlled through other existing regulatory powers (e.g. Environmental Protection Act 1986, Health (Asbestos) Regulations 1992, Occupational Safety and Health Regulations 1996) and therefore may not trigger action under the CS Act. 

Land planning and development permits often contain legal conditions requiring the management of hazardous substances to bring the development site into a condition suitable for the proposed use. Provided these conditions are fulfilled and the site is suitable for use, no action under the CS Act may be required. For instance, small scale dumping of rubbish (i.e. fly-tipping) that can be readily and safely removed may not require any action under the CS Act.

Although undisturbed naturally occurring hazardous substances, such as highly mineralised rock, acid sulphate soils or peat deposits, groundwater salinity, or gases or radiation emitted from natural geology, may represent a significant public health risk, they fall outside regulation under the CS Act. Such matters may be assessed and managed in accordance with the Public Health Act 2016.

Risk assessment

For a site to be 'Contaminated Site' there must be an unacceptable risk to health, the environment or environmental values. This means that where small amounts of hazardous substances are present they may not qualify as a 'Contaminated Site' under the CS Act. Even where higher amounts of hazardous substances are present they may still not qualify as a 'Contaminated Site' if they do not affect people or pose an unacceptable risk. These determinations are made through a process of risk assessment. 

If, after a risk assessment, a contaminated site is suitable for some uses, but not others the site may be classified under the CS Act. Classification is a formal process which assigns one of seven classifications (external site) to a reported site. For instance, if a site is suitable for high-rise apartments but not low density housing with gardens it may be classified as 'Contaminated - Restricted Use', restricting the use of the site to high rise apartments only. However, if after risk assessment the site is determined to be not suitable for any use, then remediation works may be required. In this case, the site may be classified as 'Contaminated  - Remediation Required'. 

What is remediation?

'Remediation' is legally defined  under the CS Act and means either,

a) the removal, treatment or containment of some or all of the hazardous substance(s); and/or

b) by restricting access or use of the contaminated site, so as to reduce the risk to human health or the environment to an acceptable level. 

The Department of Health (the Department) acknowledge that it may not always be practicably possible to remove, treat or contain all of the hazardous substances affecting a site. Where, after remediation, some contamination remains, a risk assessment may determine that a site may be suitable for some uses but not others (e.g. a carpark but not a public open space).

This is particularly important where contaminated groundwater has migrated from, say, a Source Site into neighbouring land (Affected Site), rendering groundwater unsuitable for some uses, but not others (e.g. for garden irrigation but not as drinking water). In this case, the site may be classified under the CS Act as 'Remediated for Restricted Use' restricting the use of groundwater to garden irrigation only.

Your rights as an affected site owner

DWER is required to contact the affected site owner in writing as soon as practical after DWER classifies the site. The letter from DWER will set out the site classification and any restrictions imposed on the site that the owner or resident must follow, such as a restriction on ground water. The letter will also provide information on how the site owner may appeal the classification.  

The Department recommends a site owner or resident who is not prepared to commit to the restrictions imposed because the site owner or resident feels that the restrictions are burdensome or unfair should appeal the decision.

Importantly the site owner should be aware that the site classification and any accompanying restrictions will be placed on the property title. In some instances this action may affect land value, development potential or mortgage and insurance decisions. The Department advises that the home owner or resident may wish to appeal the classification and seek professional or legal advice. 

The site owner or resident might expect the owner or operator of the polluting site to remediate the contamination to the affected site owner's satisfaction. However, under the CS Act, as long as something has been put in place (i.e. restriction on ground water) to protect the health of the affected site owner then the site can be deemed to have been remediated. While the Department supports the polluter pays principal to the extent that every effort should be made to remediate the contamination, the Department does not have the regulatory power to force polluters to undertake extensive remediation. Therefore, the Department suggests that affected site owners seek legal advice on the premise that the overall benefits of remediation should be greater than any adverse effects arising from the remediation such as restrictions on use of one's property.

Although the Department considers it desirable, there is no legal requirement for all parties engaged in consultation to endorse a remediation plan or classification.

The Department advise that home owners and residents seek professional legal advice in the event that they are not satisfied with the outcome of a consultation and the proposed remediation. An accredited Contaminated Sites Auditor may be relied upon to provide independent advice to all parties during the process.

Stakeholder consultation

The Department encourages open and transparent communication with stakeholders affected by a contaminated site. Stakeholders may include current owners and occupiers, local government and other responsible agencies, neighbours and other affected parties; and in certain circumstances the wider community when they are impacted. Effective stakeholder engagement means that stakeholders' concerns are addressed, risks are explained and remediation plans are discussed.

Stakeholder consultation should be initiated and led by the party responsible for the implementation of the remediation plan. Where contamination is migrating from a 'Source site' into neighbouring properties this would be the party responsible for the 'Source Site'.  Any plan to remediate a site, including any proposed restrictions on use, should be discussed with all stakeholders in advance of enactment. 

State legislation and appeal

The CA Act and the associated Contaminated Sites Regulations 2006 came into effect on 1 December 2006.

The CS Act provides a strong legal framework to report, investigate, assess and manage contamination sites in Western Australia. Information about all contaminated sites is attached to the Memorial on Title and Mandatory Disclosure requirements may apply.

Information on all reported sites is made available to other government sites and the public through a 'Basic Summary of Records' facility, and where remediation works are required or a restriction on use (preventing access or use of the land) is in place, information is available via a public access database (external site).  

This allows individuals to make informed decisions about the site, particularly if they wish to purchase, occupy, use, redevelop or sell the site. As classification under the CS Act may affect land value, and development mortgage and insurance decisions, the purchaser and their settlement agent are advised to seek professional advice prior to settlement. 

In certain circumstances a site maybe affected by contamination which is migrating from another source site. Although both 'Source' and 'Affected' sites maybe classified under the CS Act, it is the responsibility of the Source site to investigate, assess and remediate both sites.  Any persons impacted under the CS Act (as either a source or affected site) may appeal the classification decision to the Contaminated Sites Committee (CSC) (external site)

Whilst the DWER administers the CS Act, the Department provides advice on public health aspects, including public health assessments and site remediation works to ensure that nearby communities and future owners and occupiers are not exposed to unacceptable health risk.  Comprehensive information on the CS Act is available from the contaminated sites team at Department of Water and Environmental Regulation (external link)

Public health guidelines

The Department of Health has developed guidance and information material on the following topics:

  • Asbestos soil contamination - comprehensive reference material is available on a number of issues associated with the reporting, assessment and management of asbestos in soil.
  • Ground and surface water screening guidelines (PDF 155KB) - a document that covers the reporting, evaluation and management of chemicals in ground and surface water for suspected or known contaminated sites. This document should be used in conjunction with the CS Act and the associated Contaminated Sites Guidelines published by the Department of Water and Environment Regulation.
Current issues

The following links provide further information on current issues in Western Australia associated with contaminated land or on emerging contaminants of concern.

More Information

Environmental Health Directorate 


Phone: (08) 9222 2000

Last reviewed: 29-10-2021