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Land Contamination: The Assessment Process

Land contamination means that chemical substances or waste are present in soil above naturally occurring levels. Contamination represents a potential or actual risk to human health or the environment and may require an environmental assessment to determine whether remediation is required.

The Recommended Process

Contaminated land assessments generally go through multiple stages depending on the complexity of the site conditions and contaminant properties. The recommended process is detailed in the NEPM (National Environment Protection Measure), the national guideline for assessment of site contamination.

The four phases of assessment are:

Phase I – Preliminary Site Investigation
Phase II – Detailed Site Investigation
Phase III – Remediation Action Plan (RAP)
Phase IV – Validation

Triggers for Contamination Assessments

There are a number of triggers for contamination assessments. In all cases, the key question to be answered is “Based on an investigation of the level and extent of soil contamination, is this site suitable for its intended use?”

Planning and Development
Council planning requirements often include an environmental assessment particularly if the site is being developed for a sensitive use such as a childcare centre. An assessment may also be sought in response to a specific issue or complaint.

Due Diligence
Contamination assessments are regularly used for due diligence purposes in real estate acquisitions, sales, leases and financing transactions. Good due diligence will quantify any risks which can be invaluable in a sales negotiation or efficiently managing costs and timelines for development projects.

Environmental Protection Authorities can also require contamination assessments and clean up actions in their mission to protect health and the environment. An EPA may require action if a site is giving rise to pollution off-site, or where the condition of a site is not suitable for its current use. This can include investigation and/or remediation works, or a statutory environmental audit.

Preliminary Site Assessment

As contamination is often a result of current or historical activities at the site or one adjacent to it, the first stage of assessment involves a desktop study to determine how the present and historical uses of the site and identify any potential sources of contamination. If there is no suspicion of contamination, this is usually the end of the assessment process. If potential contamination is identified, further investigation is needed and will involve collecting and testing samples that are collected on site.

What happens if contamination is identified?

Investigation and evaluation will determine typical concentrations of site contaminants and their potential impact. It is important to note that just because a sample may test above the investigation levels included in the NEPM (or other guidelines) this does not automatically mean clean-up is necessary. What it does mean is that a risk assessment and possibly further investigation is required. As stated in the NEPM, inappropriate use of investigation levels as default remediation criteria may result in unnecessary remediation adding to development costs, cause unnecessary disturbances to the site, and potentially waste valuable landfill space. This is why good advice is essential for cost-effective compliance.


If remediation is required, a risk-based approach is utilised to address the proposed land use and contaminant source-pathway-receptor model developed as part of the Detailed Site Investigation. Consequently, the extent of remediation depends on the level of contamination and the actual and potential human exposure.

From this point, the most sustainable remediation option that best balances environmental, social and economic elements is determined and defined in the RAP. The RAP also sets out the validation or management requirements post-remediation to ensure that clean-up objectives are met.

Experience Counts

Geo-Logix has assessed and remediated hundreds of contaminated sites around Australia. We know that a well-designed site assessment is critical for quantifying contamination risks. Environmental site assessment done right, the first time, results in costs savings down the line. Liabilities can be better quantified, and the risk of unknown finds significantly reduced. Our technical expertise, industry experience and sound understanding of legislative requirements will ensure you meet your project objectives. Contact us for further information and advice.

The four stages of contaminated land assessment