Introduction

Preliminary Site Investigations (PSIs) are essential for identifying environmental risks early in the development process. One of the key outcomes is detecting soil contamination, which can significantly impact project timelines, approval pathways, and remediation costs.

This article answers five commonly asked questions about common soil contaminants identified during PSIs and how they affect remediation.

What Is a Preliminary Site Investigation (PSI)?

A Preliminary Site Investigation (PSI) is the first step in assessing whether a site is contaminated. It involves reviewing historical land use, conducting site inspections, and identifying potential contamination risks. PSIs are typically required:

• As part of due diligence during property transactions
• For planning approvals and rezoning applications
• Prior to construction or redevelopment
• Under NSW EPA and SEPP 2021 regulatory frameworks

The goal is to determine whether contamination is potentially present and if a Detailed Site Investigation (DSI) is required.

What Are the Most Common Soil Contaminants in Australia?

Several high-risk contaminants are frequently found on commercial, industrial, and even some residential development sites. The most common include:

• Asbestos fragments from old building materials or illegal dumping
• Heavy metals like lead, arsenic, mercury, and cadmium (often from historical industrial or agricultural use)
• Total Petroleum Hydrocarbons (TPH) and Polycyclic Aromatic Hydrocarbons (PAHs) from fuel leaks or old mechanical workshops
• Pesticides and herbicides from past agricultural operations
• Polychlorinated Biphenyls (PCBs) from electrical equipment or transformers
• Per- and polyfluoroalkyl substances (PFAS) from firefighting foam or industrial activities

These contaminants may occur individually or in combination, depending on the site’s land-use history. For more information on Soil & Waste classification, please visit our dedicated page.

How Do These Contaminants Affect Site Remediation?

Each contaminant type affects remediation in different ways:

• Asbestos often requires physical removal and certified waste disposal
• Heavy metals may need soil capping, stabilisation, or excavation
• Hydrocarbons often require bioremediation or vapour barrier installation
• Pesticides may lead to selective soil treatment or complete removal
• PFAS poses complex challenges due to its persistence and may require specialist intervention

The contaminant’s concentration, depth, spread, and risk to human health or the environment determine the scope and cost of remediation.

Can a PSI Confirm Whether Remediation Is Needed?

A PSI alone generally cannot confirm the full extent of contamination or recommend remediation. Instead, it:

• Flags potential risks based on historical data and visual inspections
• Identifies the likely types of contaminants
• Recommends whether a Detailed Site Investigation (DSI) is needed to quantify contamination levels
• Helps inform risk-based decisions early in project planning

Skipping this step can lead to costly surprises later in development.

What Happens After Contaminants Are Detected?

If a PSI indicates the potential for significant contamination, the next steps are:

1. Detailed Site Investigation (DSI) – involves sampling and lab testing to define contaminant extent
2. Site-specific risk assessment – evaluates health and environmental risks
3. Remediation Action Plan (RAP) – outlines strategies for managing or removing contamination
4. Site remediation and validation – ensures the land meets reuse criteria under SEPP and NEPM guidelines

The presence of high-risk contaminants may also trigger EPA notification obligations and affect your DA or subdivision approvals.

To learn more, read our guide detailing the soil contamination testing process – check out our Step-by-Step Overview here.

Start with Accurate Soil Contamination Screening

At Raw Earth Environmental, our environmental consultants deliver fast, compliant PSIs tailored to the requirements of NSW planning authorities. We help you identify risks early, avoid regulatory delays, and confidently move toward remediation if needed.

Book a Preliminary Site Investigation today.