Preliminary Site Investigation (PSI) for Development Applications in NSW: When It’s Required and What Councils Are Looking For

If you’re preparing a Development Application (DA) and have been told you need a Preliminary Site Investigation (PSI) or Environmental Site Assessment, you’re not alone. Across New South Wales, councils and planning authorities regularly require PSIs to assess whether land is suitable for its proposed use particularly where there is potential for contamination.

Understanding why a PSI is required, when it is triggered, and what councils are actually assessing can save significant time, cost, and frustration during the DA process. This article explains the role of a Preliminary Site Investigation in NSW planning, how it fits into contaminated land assessment frameworks, and what developers, architects, and planners need to know to avoid approval delays.

What Is a Preliminary Site Investigation (PSI)?

A Preliminary Site Investigation (PSI) is the first stage of a contaminated land assessment. It is a structured environmental assessment that evaluates whether a site has the potential to be contaminated and whether that contamination could pose a risk to human health or the environment under the proposed development.

In NSW, a PSI is typically undertaken in accordance with:

• NSW EPA contaminated land guidance

• NEPM 2013 (National Environment Protection Measure)

• Relevant planning instruments, LEPs, and DCPs

• Council-specific contaminated land policies

The purpose of a PSI is not necessarily to prove contamination exists, but to determine whether further investigation is required to support planning approval.

When Is a Preliminary Site Investigation Required for a DA?

A PSI is commonly required when a council, certifier, or planning authority identifies a potential contamination risk associated with the site or its proposed use. Typical triggers include:

Historical or Current Land Use

Councils frequently request a PSI where a site has been used for, or is adjacent to, activities such as:

• Industrial or commercial operations

• Service stations or mechanical workshops

• Agricultural uses involving pesticides or herbicides

• Landfilling, uncontrolled fill, or earthworks

• Warehousing, depots, or manufacturing

• Sites with imported fill of unknown origin

Change to a More Sensitive Land Use

Even where no obvious contamination is present, a PSI is often required when land is proposed to be redeveloped for a more sensitive use, such as:

• Residential developments

• Childcare centres or schools

• Hospitals or healthcare facilities

• Aged care or community facilities

This aligns with the NSW planning principle of ensuring land is “suitable for its intended use”.

Council or Planner Request

In many cases, the trigger is simple:

“Council has requested a Preliminary Site Investigation to address potential contamination concerns.”

This may occur through:

• A DA Request for Information (RFI)

• Pre-lodgement advice

• Conditions of consent

• Planner or environmental health officer review

Preliminary Site Investigation vs Detailed Site Investigation (DSI)

A common point of confusion is the difference between a PSI and a Detailed Site Investigation (DSI).

• A PSI is a screening-level assessment. It identifies potential contamination sources, exposure pathways, and receptors, and determines whether contamination is likely.

• A DSI is a sampling-based investigation, involving intrusive soil, groundwater, surface water, or soil vapour testing to quantify contamination levels.

Importantly, not every PSI leads to a DSI. Many PSIs conclude that:

• No contamination sources are present, or

• Contamination is unlikely to pose a risk under the proposed development

A well-prepared PSI can often avoid unnecessary intrusive investigations, saving time and cost.

What Does a Preliminary Site Investigation Typically Include?

While the scope varies depending on the site and council expectations, a PSI in NSW generally includes:

Desktop Study and Site History Review

• Review of historical aerial imagery

• Title records and land use history

• Council files and planning records

• EPA databases and notices

• Surrounding land use context

Site Inspection (Walkover)

• Visual assessment of site conditions

• Identification of potential contamination indicators

• Assessment of fill materials, staining, odours, or buried infrastructure

Preliminary Conceptual Site Model (CSM)

A CSM identifies:

• Potential contamination sources

• Exposure pathways

• Sensitive receptors

• Potential risks relevant to the proposed land use

Preliminary Risk Assessment

Using professional judgement and relevant guidelines, the consultant assesses whether the site presents:

• A low risk suitable for the proposed use, or

• A risk that warrants further investigation (DSI)

Planning and Regulatory Conclusions

The PSI provides a clear conclusion addressing:

• Whether the land is suitable for its proposed use

• Whether further investigation is recommended

• How the findings align with council and NSW EPA expectations

What Councils Are Really Assessing

From a planning perspective, councils are not just looking for technical data. They want confidence that:

• Contamination risks have been properly considered

• The assessment aligns with NSW planning and EPA frameworks

• The proposed development will not pose a risk to future occupants

• Any uncertainty has been appropriately managed

A PSI that clearly addresses these points in plain, planning-focused language is far more likely to be accepted without delay.

Common Mistakes That Delay DA Approval

In practice, many DA delays occur due to avoidable issues, including:

• Generic or non-NSW-specific PSI reports

• Lack of a clear conclusion on site suitability

• Overly conservative recommendations triggering unnecessary DSIs

• Failure to address council-specific concerns

• Poor explanation of professional judgement

A targeted, proportionate PSI prepared by an experienced environmental consultant can significantly reduce these risks.

Engaging an Environmental Consultant for a PSI

When engaging a consultant for a Preliminary Site Investigation, it’s important to choose someone who:

• Understands NSW planning processes

• Regularly works with councils and planners

• Applies professional judgement, not just checklists

• Writes reports that are clear, defensible, and DA-ready

A well-prepared PSI should support your development, not become another obstacle.

Final Thoughts

A Preliminary Site Investigation is a critical step in many NSW development projects, particularly where contaminated land considerations are present. When undertaken early and properly scoped, a PSI can streamline the DA process, provide certainty to planners and developers, and avoid unnecessary delays or costs.

If you’ve been asked to provide a PSI or Environmental Site Assessment to support a Development Application, engaging the right expertise early can make all the difference.