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Contamination, in relation to land, water or a site, means having a substance present in or on that land, water or site at above background concentrations that presents, or has the potential to present, a risk of harm to human health, the environment or any environmental value (Contaminated Sites Act 2003).

The Contaminated Sites Act 2003  was introduced to identify, record, manage and clean up contamination in Western Australia.

Land owners, occupiers and polluters must report known or suspected contaminated sites to the Department of Water and Environmental Regulation.

Investigating and cleaning up contaminated sites is, in most cases, the responsibility of the polluter or current site owner.

We administer and enforce the Contaminated Sites Act 2003  and Contaminated Sites Regulations 2006. 

This includes classifying sites (in consultation with the Department of Health) and making information on contaminated sites available to the public. 

For a risk from site contamination to exist, all three of the following elements must exist:

• a source (e.g. contaminated groundwater)
• a pathway  (e.g. use of bore water)
• a receptor (e.g. residents).

There are many ways that site contamination can be managed. There is no ‘one size fits all’ approach and each case is assessed individually.

The determination of whether an unacceptable risk from site contamination exists depends on a range of factors, including whether or not the current or proposed land use is considered sensitive, such as residential properties or schools. 

In some cases, the way to minimise and manage risk is to remove one of the three elements – for example, if the pathway is removed then the risk to the public is reduced or removed. Another example would be managing contaminated groundwater by ensuring that bores are not permitted within the contaminated area and preventing access to that water source.

Sometimes sites can be cleaned up by removing the source, such as removing contaminated soil, or by putting physical barriers between the contamination and people, thus removing the pathway.

However, sometimes the nature of contaminants, their location or their extent, may mean that a complete site clean-up is not practicably possible and the contamination may need to be managed on an ongoing basis. 

The Contaminated Sites Act 2003  establishes a hierarchy of responsibility for remediation which includes the ‘polluter pays’ principle.

This means that in most cases the person who caused the site contamination is responsible for implementing and paying for the site assessment and any subsequent management, containment or clean-up of the site. This includes meeting the costs of and undertaking communication with the affected community. 

We classify sites in consultation with the Department of Health, which has specific expertise in assessing public health risk from site contamination. 

In the vast majority of cases, site contamination is associated with industrial and commercial activities.

Western Australia, like other urbanised places in the world, is affected by site contamination issues that are the direct result of past practices including:

• industrial sites such as gasworks and tanneries
• fuel and chemical storage and associated spills and leaks
• agricultural chemicals, herbicides and pesticides/termiticides
• waste products such as ash (which were often buried) and asbestos containing materials.

Contamination is often detected as a result of the site investigations associated with land use planning and development processes required as part of land development and applications for a new use for the land.

There are many chemical substances that can affect the quality of groundwater. The impacts range from an unpleasant taste/odour to potential health hazards.

Often, groundwater contamination is a legacy of past practices and may not have been caused by the current site owner.

Potentially contaminating industries, activities and land uses which can cause contamination are listed in our Assessment and management of contaminated sites guideline.

Many sites with groundwater contamination are under active management and pose no threat to neighbouring communities. 

Since the commencement of the Contaminated Sites Act 2003, land owners, occupiers and polluters must report known or suspected contaminated sites to us. Prior to this, there was no legal requirement to report contamination.

The Contaminated Sites Act 2003 has provided vital improvement to the protection of public health and the environment. Our department, in collaboration with the Department of Health, are now able to assess the risk of contamination to the public and the environment and ensure the responsible parties manage and clean up contaminated sites.

The process of assessing site contamination can be lengthy and will depend on the nature of sampling and testing required. Samples of soil, groundwater or vapour need to be collected in the field and then transported to laboratories for analysis.

The laboratories perform the analysis and perform checks on the test results prior to their release. Once received, test results need to be reviewed and interpreted by health and risk assessment specialists.

Monitoring at a site, such as groundwater, surface water or vapour monitoring, over a period of time is often a necessary part of contamination assessment and management. For example, it may be carried out to assess trends in contaminant behaviour or confirm the successful remediation or containment of contamination.

Often this means monitoring must be carried out over a long period of time to consider longer-term trends and seasonal variations.

Information on all contaminated sites (known and suspected), which are reported to us, is available to the public. There are two ways to access information on reported sites: 

• Contaminated Sites Database â€“ information on confirmed contaminated sites is available online, free of charge.
• Reported sites register – for information on other sites reported to us, any person may submit a Form 2 and applicable fee to obtain information held in relation to a particular property.

If a risk to public health is confirmed, we and/or the responsible party will directly advise the affected community.