By Nova Group Pacific | Geotechnical & Environmental Consultants
Introduction
Contaminated land is more common in Australia than most people expect. Former industrial sites, old service stations, dry cleaners, agricultural properties, and even residential blocks can carry legacy contamination from past activities. If you are buying, developing, or financing land, you cannot treat contamination as an afterthought. The legal, financial, and environmental stakes are too high.
This guide walks through the two-stage site investigation process used across Australia — what each stage involves, when you need one, and how remediation works once contamination is confirmed.
Why contaminated land matters
Soil and groundwater contamination can affect human health, surrounding ecosystems, and property values. Australia regulates contaminated land at the state and territory level, but a nationally consistent framework underpins the approach — principally the National Environment Protection (Assessment of Site Contamination) Measure 1999, commonly called the ASC NEPM, last amended in 2013.
The ASC NEPM sets the health-based investigation levels and methodology that regulators, consultants, and courts rely on across the country. Every credible site contamination assessment in Australia references it.
Beyond the ASC NEPM, each state and territory has its own contaminated land legislation. In New South Wales, the key instrument is the Contaminated Land Management Act 1997. Victoria operates under the Environment Protection Act 2017 and its subordinate regulations. Queensland uses the Environmental Protection Act 1994. While the regulatory labels differ, the underlying assessment methodology is consistent nationwide.
What triggers a contaminated land assessment?
Several situations require — or strongly warrant — a formal assessment:
Development applications. Most councils across Australia require evidence that land is suitable for its intended use before approving a DA. For sensitive land uses (housing, childcare, schools, aged care), the bar is higher than for commercial or industrial development.
Change of land use. Converting an industrial or commercial site to residential use almost always triggers an assessment requirement. Regulators consider the sensitivity of the future users — children and residents face greater exposure risk than adult workers in controlled environments.
Property transactions. Lenders, purchasers, and their solicitors increasingly require a contamination assessment as part of due diligence. An unidentified contamination liability can void a transaction or transfer legal exposure to the buyer.
Known or suspected past land use. If records, aerial photographs, or site inspection reveal a history of fuel storage, chemical handling, metal fabrication, dry cleaning, or intensive horticulture, an assessment is warranted regardless of whether a formal trigger applies.
Regulatory direction. State environment protection authorities (EPAs) can direct landowners or occupiers to investigate and remediate. Receiving such a direction is a legal obligation, not a suggestion.
Stage 1: the Preliminary Site Investigation (PSI)
The Preliminary Site Investigation — sometimes called a Phase 1 ESA (Environmental Site Assessment) — is a desktop and observational study. It does not involve drilling, sampling, or laboratory analysis. Its purpose is to assess whether contamination is plausible given the site's history.
What a PSI involves
A qualified environmental consultant carries out the following:
Historical research. Your consultant reviews historical aerial photographs, topographic maps, Sands Directories, council records, and title searches to reconstruct land use back as far as records allow — typically to the early twentieth century or beyond.
Regulatory database searches. This includes searches of state EPA contaminated sites registers, underground storage tank records, development application histories, and hazardous materials databases.
Site inspection. A site inspection follows, with the consultant observing current conditions: structures, surface staining, odours, stressed vegetation, drainage patterns, drums or containers, and any obvious signs of past industrial activity.
Interview. Where possible, the consultant interviews current and former occupiers, owners, or neighbours to gather knowledge that records may not capture.
Report and risk assessment. The PSI concludes with a qualitative assessment of contamination likelihood. It classifies the site as:
- Low risk — no plausible contamination pathway identified; no further investigation recommended
- Moderate risk — some indicators present; further investigation may be warranted
- High risk — credible contamination source identified; a Detailed Site Investigation is recommended
A well-executed PSI is not merely a checkbox exercise. It shapes the entire scope and cost of what follows. A consultant who misses a former underground tank or an historical chemical storage area at the PSI stage can leave a client exposed to significant liability downstream.
Stage 2: the Detailed Site Investigation (DSI)
Where the PSI identifies a credible contamination risk, a Detailed Site Investigation follows. At this stage, physical sampling and laboratory analysis either confirm or rule out contamination and characterise its nature and extent.
What a DSI involves
Sampling program design. Based on the PSI findings, your consultant designs a sampling program — targeting the areas most likely to contain contamination based on historical land use, drainage patterns, and site layout.
Intrusive works. Drillers collect soil samples via hand auger, direct push technology (DPT), or machine-drilled boreholes, depending on investigation depth. Where groundwater contamination is possible, the team installs monitoring wells.
Laboratory analysis. Samples go to a NATA-accredited laboratory for analysis. The suite of tests depends on the suspected contaminants — common analytes include total petroleum hydrocarbons (TPH), benzene, toluene, ethylbenzene and xylenes (BTEX), polycyclic aromatic hydrocarbons (PAHs), heavy metals, organochlorine pesticides, and per- and polyfluoroalkyl substances (PFAS).
Comparison against investigation levels. Results compare against the health-based investigation levels in the ASC NEPM, as well as state-specific guideline values where applicable. Exceeding an investigation level does not automatically mean the site needs remediation — it triggers further risk assessment.
Risk assessment. The DSI report presents a human health and ecological risk assessment that considers site-specific exposure pathways: who is on the site, how often, for how long, and through which routes (ingestion, inhalation, dermal contact). A residential site has very different exposure assumptions from an industrial one.
Conclusions and recommendations. The report states whether contamination exceeds applicable criteria for the intended land use and, if so, recommends a path forward — further investigation, remediation, or risk-based management.
Understanding PFAS — a growing focus
Per- and polyfluoroalkyl substances (PFAS) deserve particular attention. These synthetic chemicals — historically used in firefighting foams, non-stick coatings, and waterproofing — persist in the environment and researchers have linked them to adverse health effects at very low concentrations.
PFAS contamination is now a significant issue at and around former defence sites, airports, fire training areas, and industrial facilities across Australia. The Department of Defence has identified numerous contaminated sites associated with aqueous film-forming foam (AFFF) use.
In 2022, regulators amended the ASC NEPM to include PFAS investigation levels for the first time, giving assessors a formal regulatory basis where only interim guidance previously existed. If your site has any connection to fire training, aviation, or military activity — or lies within a few kilometres of a facility that does — PFAS screening should form part of the assessment scope.
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What happens when contamination is confirmed?
Confirming contamination does not necessarily mean a site is undevelopable. It means you must manage contamination down to a level appropriate for the intended land use. There are three broad approaches.
Remediation
Remediation removes, treats, or destroys the contamination. Common techniques include:
Excavation and disposal. The contractor excavates contaminated soil and transports it to a licensed facility for treatment or disposal. Excavation suits localised, shallow contamination well, but costs rise steeply with volume.
In-situ treatment. Chemical oxidation, bioremediation, or soil vapour extraction treats contamination in place, without removing the soil. These techniques suit deep or extensive contamination where excavation is impractical.
Groundwater pump and treat. The team extracts contaminated groundwater, treats it above ground, and either discharges or reinjected it into the ground. Pump and treat is a long-term measure, typically running alongside soil remediation on heavily impacted sites.
Stabilisation and solidification. Chemical reagents bind contaminants within the soil matrix, reducing their mobility and bioavailability. Stabilisation suits sites with certain heavy metal contaminations.
Containment
Where full remediation is disproportionate to the risk, containment limits exposure rather than removing the source. A clean soil cover (clean fill cap) can break the exposure pathway for surface soils — common on former landfill sites redeveloped for commercial or industrial use.
However, containment requires ongoing management and monitoring. It also affects what future uses of the site are permissible. Consequently, owners must disclose these obligations in the site's environmental management history.
Risk-based management
For some sites — particularly those remaining in industrial or commercial use — a risk-based approach accepts that contamination is present but demonstrates through assessment that it poses no unacceptable risk to current or future users under defined land use conditions. This approach relies on institutional controls (site-specific development restrictions registered on title) to prevent incompatible future uses.
Validation and audit
After remediation, a validation report confirms the work achieved its objectives. Specifically, validation involves sampling the remediated area to confirm that contaminant concentrations meet the agreed remediation criteria.
In some states — particularly Victoria and South Australia — an independent environmental auditor (accredited by the relevant EPA) must review the assessment and remediation findings and issue an audit statement or certificate. This gives regulatory certainty and councils or EPAs often require it before issuing a planning permit or approving a sale.
In NSW, a similar function is carried out by a site auditor accredited under the Contaminated Land Management Act.
How long does a contaminated land assessment take?
Timelines vary depending on site complexity, investigation scope, and laboratory turnaround.
The desktop and inspection phase — the PSI — typically takes two to four weeks. The DSI, which includes field work and laboratory analysis, generally runs six to twelve weeks. Remediation timelines vary enormously: a small excavation job may wrap up in a matter of weeks, while a complex groundwater treatment program can run for years. Validation sampling and reporting adds a further three to six weeks after remediation is complete. Where an independent environmental audit is required (Victoria and South Australia in particular), allow an additional three to six months for the auditor's review and sign-off.
These are indicative ranges. A simple PSI on a single residential lot moves faster than a complex multi-source industrial investigation. When groundwater monitoring forms part of the scope, standard practice requires quarterly sampling over at least one year before consultants can draw conclusions.
Who can carry out a contaminated land assessment in Australia?
The ASC NEPM requires a suitably qualified person (SQP) to carry out assessments. In practice, this means a consultant with formal qualifications in environmental science, chemistry, or engineering, combined with demonstrated experience in site contamination assessment.
In Victoria, the Environment Protection Act 2017 introduced formal requirements for environmental auditors — only EPA-accredited auditors can issue the audit statements required for prescribed contamination matters. In NSW, SA, and WA, similar accreditation schemes exist for site auditors.
Choosing the right consultant therefore matters. The PSI and DSI reports become legal documents that regulators, courts, and transaction parties rely on. A report that is methodologically weak, or prepared by someone without relevant experience, can fail to satisfy regulatory requirements — costing time and money to redo.
Summary: the assessment pathway at a glance
The process moves through five steps. The Preliminary Site Investigation (PSI) identifies plausible contamination sources from historical records and site observation, and produces a risk classification with a recommendation on whether to proceed to the next stage. If a credible risk is identified, the Detailed Site Investigation (DSI) follows — confirming whether contamination is present, characterising its extent, and assessing the risk to human health and the environment. Where contamination exceeds acceptable levels for the intended land use, remediation removes or treats it to meet the required criteria. A validation report then confirms the remediation objectives were achieved through post-works sampling. Finally, in states where it is required, an independent environmental audit provides regulatory sign-off in the form of an audit statement or certificate.
Speak to an environmental specialist
If you are buying, developing, or managing land with a complex history, the right assessment from the start saves time, money, and legal exposure. A contamination liability discovered late — during construction, after settlement, or when a future buyer commissions their own assessment — is always far more expensive to resolve than one identified and managed proactively.
Nova Group Pacific provides preliminary and detailed site investigations, remediation management, and validation reporting across Australia and New Zealand. Our team includes suitably qualified persons (SQPs) with experience across the full spectrum of Australian contamination types and regulatory frameworks.
Contact us to discuss your site and request a scope and fee proposal.
Frequently asked questions
Do I need a PSI before buying a commercial property?
Not always legally required, but strongly advisable nonetheless. The cost of a PSI is typically low relative to the risk of acquiring an undisclosed contamination liability. Most commercial lenders and many solicitors now require one as standard due diligence.
Can a site pass a PSI but still be contaminated?
Yes. A PSI is a desktop and observational exercise. It can identify risk, but it cannot rule out contamination — only a DSI with physical sampling can do that. A low-risk PSI conclusion means the available evidence does not indicate a plausible contamination source, not that the site is guaranteed clean.
What is the difference between a site auditor and an environmental consultant?
An environmental consultant carries out the investigation and prepares the reports. A site or environmental auditor is an independently accredited professional who reviews those reports and issues a regulatory sign-off. Where an audit applies — VIC, SA, and NSW for certain matters — the auditor's statement satisfies the planning or EPA authority, not the consultant's report alone.
This article provides general information only. Contaminated land regulation varies by state and territory. Always engage a suitably qualified environmental professional for advice specific to your site and jurisdiction.
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