Understanding the key phases of a contaminated land investigation is essential for property developers, environmental consultants, and stakeholders managing site risk. From uncovering potential contamination to developing remediation plans, each phase plays a critical role in meeting NSW EPA compliance and protecting human health.
This article answers five commonly asked questions about the contaminated land investigation process.
When Is a Contaminated Land Investigation Required?
A contaminated land investigation is typically triggered during due diligence for property transactions, development approvals, or following the discovery of hazardous materials such as asbestos, heavy metals, or hydrocarbons. These investigations are often mandated when:
- A site has a history of industrial or commercial use
- Changes in land use (e.g. from industrial to residential) are proposed
- Contamination is suspected or confirmed during earthworks
- Regulatory notices or planning authorities require a formal assessment
In NSW, contaminated land management is regulated under the Contaminated Land Management Act 1997 and the SEPP (Resilience and Hazards) planning framework, with strict guidelines from the EPA and local councils.
What Happens During a Preliminary Site Investigation (PSI)?
The Preliminary Site Investigation (PSI) is the first formal step in assessing contamination risk. Its purpose is to identify whether contamination is likely based on the site’s history, condition, and surrounding land uses.
Key PSI activities include:
- Desktop review of historical land use, aerial imagery, and planning records
- Site inspection for visible contamination or signs of distress (e.g. chemical drums, staining)
- Interviews with current or past owners/operators
- Review of adjacent land uses and potential contaminant migration
The PSI helps determine if further investigation is warranted. If no risk is identified, the site may be cleared for development. If potential risks are present, a Detailed Site Investigation (DSI) is usually recommended.
What Does a Detailed Site Investigation (DSI) Involve?
A DSI is more invasive and provides data-driven insight into the presence, type, and extent of contamination. It typically includes:
- Soil and groundwater sampling and laboratory analysis
- Surface water and vapour testing (where relevant)
- Use of boreholes and monitoring wells to assess vertical migration
- Human health and ecological risk assessments
- Contaminant pathway modelling (e.g. air, water, soil transport)
The goal of the DSI is to confirm whether contamination levels exceed investigation thresholds set out in the National Environmental Protection Measure (NEPM) and local EPA guidelines. If contamination is present above acceptable levels, the site may require remediation before it can be redeveloped.
