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If you own commercial or industrial land in Western Australia that has been reported or classified under the Contaminated Sites Act 2003, this guide sets out what you are required to do, how long you have and what it is likely to involve.
Many owners have held a classification for years without hearing from the Department of Water and Environmental Regulation (DWER). That is changing. In September 2026 the Office of the Auditor General reported that over 1,200 possibly contaminated sites had waited more than five years for further assessment information and that more than 110 high-priority sites had been assigned to staff who had since left the department.
The department has agreed to reassign those cases, set clearer triggers for enforcement and track overdue actions. If your site is on the register, expect to be contacted and required to act.
Need a clear plan and a quote for your site? Contact us and we will review your classification and tell you what the next step involves.
The Act sets up a system to identify, record, manage and clean up contaminated land and water in WA. DWER administers it in line with the Contaminated Sites Regulations 2006, classifying sites with advice from the Department of Health on public health risk.
Under the Act, land is considered contaminated when a substance is present above background concentrations and presents, or could present, a risk of harm to human health, the environment or any environmental value. A “site” includes the land, the groundwater beneath it and any surface water.
Owners, occupiers and anyone who caused contamination must report a site to the department:
Within 21 days of first knowing the site is contaminated
As soon as reasonably practicable if they suspect it is contaminated.
Failing to report is an offence. Individuals face fines of up to $250,000 plus $50,000 a day for a continuing offence and penalties for companies are five times higher. If you are working with accredited contaminated sites auditor they must also report contamination if they find it.
Failure to meet your obligations can result in significant financial and legal consequences. Site owners and other parties responsible for contamination can face enforcement notices that compel immediate investigation and remediation.
Ignoring an enforcement notice can lead to fines, approval delays and restrictions on land use. Consequences can, however, go beyond regulatory penalties. Non-compliance often leads to reputational harm and a loss of stakeholder confidence, particularly when there is a potential for environmental and community impacts.
It is also important to understand that liabilities can extend to new owners if contamination was not disclosed in a property transaction. Although you may not be responsible for contamination, you can still face penalties for its poor management.
By addressing contamination risks early and transparently, property owners can avoid the escalating costs and setbacks associated with these penalties.
To ensure your site is compliant with the CSA, follow these steps:
Engage West Soil & Water – to ensure you can navigate regulations with confidence
Check the Contaminated Sites Database – confirm if the land is listed as contaminated and, if so, its classification.
Identify known or suspected contamination – within soil, groundwater and other materials.
Disclose contamination – ensure buyers or lessees are informed as required.
Conduct an investigation – start with a preliminary site investigation and conduct a detailed assessment if risks are present.
Clarify liability – determine who is responsible for remediation and ensure it is documented.
As mandated by the Act, a thorough contaminated site investigation is the first step in redevelopment. At West Soil & Water, we offer two kinds:
Phase 1 Environmental Site Assessments (including desktop studies and site history reviews)
Phase 2 Environmental Site Assessments (involving more targeted soil, groundwater and vapour sampling)
They are designed to identify potential risks, confirm the presence and extent of contamination and produce the documentation regulators demand. In practice, this means less uncertainty, reduced risk of penalties and smooth progress for your transaction and development
If investigations determine the presence of a contaminant, the site will then be assessed and classified under the Act. These classifications include:
Contaminated – remediation required
Contaminated – restricted use
Possibly contaminated – investigation required
Remediated for restricted use
Decontaminated
Each classification carries different implications for the land. This will determine how it can be used and whether further investigation or remediation services are necessary.
Every reported site receives one of seven classifications. The site owner and occupier are usually notified in writing within 45 days.
| Classification | What it means for you |
|---|---|
| Report not substantiated | There is not enough information to indicate contamination. No action is needed. |
| Possibly contaminated, investigation required | Contamination is possible and needs to be confirmed or ruled out. You will need to have the site tested. |
| Contaminated, remediation required | The site is contaminated and must be cleaned up before it is suitable for its current or proposed use. |
| Contaminated, restricted use | The site is contaminated but safe for some uses, with restrictions (for example, no groundwater bores). |
| Remediated for restricted use | The site has been cleaned up to a standard that suits some uses only. |
| Decontaminated | The site has been remediated and is suitable for all uses. |
| Not contaminated, unrestricted use | Testing found no contamination. |
The four “contaminated” classifications (from possibly contaminated to remediated for restricted use) are recorded on the property’s certificate of title as a memorial.
Most dormant cases are classified as possibly contaminated (investigation required) or contaminated (remediation required). These are the classifications the Auditor General found to have to longest wait times and the ones DWER is expected to follow up first.
In most cases the person who caused the contamination is responsible for investigating it and cleaning it up. This is the “polluter pays” principle and the Act sets a hierarchy of responsibility behind it.
If the polluter cannot be found or no longer exists, responsibility can fall to the current owner. However, an owner or occupier who changes, or proposes to change, the use of the land is responsible for any extra clean-up that the new use requires.
The hierarchy also takes into account whether an owner knew about the contamination when they bought the site. The State is the last party in the chain. Disputes about who is responsible go to the Contaminated Sites Committee.
The department follows a set escalation path: a reminder, then an action required letter, then a formal notice. For a site classified as possibly contaminated (investigation required), the formal step is an investigation notice, which states what must be done and by when.
There is no single deadline that applies to every classified site. The timeframe is set in the letter you receive, so read it carefully and note the date. Failing to comply with a formal notice can attract penalties of up to $500,000, plus up to $100,000 a day.
As such, the most cost effective strategy is to act early. If you respond to a reminder or action required letter with a plan and a timeframe, you keep control of the scope and the cost.
Once you receive DWER notice, how do you find out if your site is actually contaminated? You start with a preliminary site investigation (PSI), which looks at the property’s history, past land uses, earlier reports and the department’s records, and usually includes limited soil sampling. It tells you whether contamination is likely, where and what kind.
If the PSI confirms a risk, a detailed site investigation (DSI) follows. Targeted soil, groundwater and, where needed, soil vapour testing maps the extent of contamination and shows whether it poses a risk to people or the environment. Samples are analysed by NATA-accredited laboratories.
The results decide your path:
No unacceptable risk: the reports support a request to reclassify the site
Risk that can be managed: a site management plan sets out restrictions and monitoring
Risk that needs treatment: a remediation plan sets out the clean-up and validation testing
For some sites, an accredited contaminated sites auditor must sign off on the work before the classification can be changed.
The cost of investigation, monitoring and remediation depends on the scope. Most investigators account for the size of the site, its history, the contaminants involved, the number of samples and laboratory analyses and whether groundwater is affected.
In practice, a desktop review costs far less than a groundwater investigation and a site with a long industrial history will need more sampling than one with a single past use.
You can keep the cost down by:
Using existing reports first, because earlier investigations often answer part of the question
Targeting the testing at known sources (old tanks, wash-down areas, fill) instead of blanket grids
Agreeing the scope with the department early, so work is not repeated
Staging the work, so you only pay for a DSI if the PSI shows you need one
We quote investigations in stages, so you know the cost of each step before you commit to it.
If a site is classified as contaminated (remediation required), contaminated (restricted use) or remediated for restricted use, the owner must give a signed disclosure (Form 6) to the buyer, any mortgagee or lessee and the department at least 14 days before the sale settles. Any investigation or clean-up notice on the site must also be disclosed. Failing to disclose is an offence carrying a fine of up to $125,000, plus $25,000 a day.
We’d also recommend voluntary disclosure for sites that are possibly contaminated (investigation required), in addition to the note already on the title.
If you are buying, you can search the contaminated sites database for confirmed contamination. You will, however, need to request a basic summary of records to learn about suspected contamination. We offer due diligence investigations before settlement to help you understand what you are taking on and discover grounds to negotiate on price.
You can appeal a classification to the Contaminated Sites Committee either within 21 days of the notice or the stated period (if the notice has one). Note, the classification still applies while the appeal is decided.
If the timeframe has passed, you will have to undergo an investigation and provide test results that support a different classification. A PSI or DSI that shows no unacceptable risk is the most common basis for reclassification.
We are an independent environmental consultancy in Western Australia. We work for commercial and industrial landowners, developers and buyers on contaminated sites across WA, providing everything from desktop assessments through to remediation and ongoing monitoring.
We read your classification and the department’s letters, tell you what has to be done and quote a scope that meets it without extra work. We respond quickly when a notice has a deadline and explain results in plain language so you can make clear and confident decisions.
It depends on the site’s size and history, the contaminants and whether groundwater is affected. Most owners start with a preliminary site investigation, which costs far less than a full investigation, and only move to the next stage if the results require it.
You have the time stated in the letter or notice, there is no single statutory deadline for every site. Be sure to check the date and respond before it, even if only with a plan.
Gather any previous reports on the site, then commission a preliminary site investigation through our team. It shows whether contamination is likely and what testing, if any, comes next.
Yes. If testing shows there is no unacceptable risk or the site has been remediated, DWER can reclassify it based on the reports you provide. Some sites need an accredited auditor’s sign-off first.
It is a notice registered on the certificate of title that records the site’s classification under the Act. It applies to the four classifications that indicate possible or confirmed contamination and stays until the site is reclassified.
