Do I Need a Preliminary Site Investigation for a Development Application in NSW?
If you are preparing a development application in NSW, you may be asked to provide a Preliminary Site Investigation (PSI) or contamination assessment as part of your application.
This is particularly common where a site has a history of commercial, industrial or agricultural use, contains imported fill, is being changed to a more sensitive land use, or where there is uncertainty about how the land was previously used.
A request for a PSI does not necessarily mean that Council believes the site is contaminated.
Instead, the purpose of the investigation is generally to give the consent authority enough information to determine whether contamination is likely to affect the proposed development and whether the land is suitable — or can be made suitable — for its intended use.
Understanding this process before lodging your development application can help avoid unnecessary Requests for Further Information (RFIs) and allow contamination issues to be addressed alongside the design rather than after the assessment has already commenced.
Why does Council consider contamination during a development application?
Contaminated land has been incorporated into the NSW planning system for decades.
The former State Environmental Planning Policy No 55 – Remediation of Land established a framework requiring planning authorities to consider contamination when making planning and development decisions. These requirements are now contained within Chapter 4 of the State Environmental Planning Policy (Resilience and Hazards) 2021.
Section 4.6 requires a consent authority to consider whether land is contaminated before granting development consent.
Where contamination is present, Council must be satisfied that the land:
is suitable for the proposed development in its existing condition; or
will be suitable following remediation.
If remediation is required, Council must also be satisfied that the land will be remediated before it is used for the proposed purpose.
This is why contamination can become an important consideration during the DA process.
Does every development application require a PSI?
No.
The requirement to consider contamination applies broadly, but this does not mean that every development application requires a Preliminary Site Investigation.
For many sites, the existing land use, planning records and historical information may provide sufficient confidence that contamination is unlikely to present a material issue.
A PSI becomes more likely where there are indicators that the land may have been affected by contamination.
These can include:
former industrial or commercial activities;
service stations, workshops or fuel storage;
agricultural or horticultural land uses;
imported fill of unknown origin;
waste disposal or historical dumping;
demolition of older structures;
dry-cleaning or other activities involving solvents;
potentially contaminating activities on neighbouring properties; or
incomplete information about how the site was historically used.
Section 4.6 also specifically requires a preliminary investigation to be considered for certain changes of use involving potentially contaminated land. This includes circumstances where residential, educational, recreational, childcare or hospital uses are proposed and there is insufficient knowledge about whether contaminating activities have historically occurred.
Individual councils may also have contaminated land policies or Development Control Plan requirements that influence when contamination reports are requested. The NSW EPA notes that council approaches and contaminated-land policies can vary across NSW.
Why undertaking the PSI before lodging the DA can save time
One of the most common ways contamination causes delays is when it is identified during Council's assessment rather than before lodgement.
For example, an applicant may lodge architectural drawings, engineering plans and a Statement of Environmental Effects only for Council to subsequently identify a potentially contaminating historical land use and issue an RFI requesting a PSI.
The application may then effectively pause while the investigation is undertaken.
Where there is a reasonable likelihood that contamination will need to be addressed, undertaking the Preliminary Site Investigation before lodging the DA can identify those issues earlier.
It also allows the consultant, planner and design team to understand whether contamination is likely to materially affect the development.
Sometimes the PSI will conclude that there is a low likelihood of significant contamination and no further investigation is required.
In other cases, it may identify specific areas that require further assessment.
Knowing this early allows the next stage to be planned rather than discovered halfway through the DA process.
What happens during a Preliminary Site Investigation?
A PSI is primarily a historical and conceptual investigation.
The consultant will typically review information such as:
historical aerial photographs;
planning and development records;
historical business directories where available;
EPA contaminated land information;
SafeWork NSW records where relevant;
geology, soils, groundwater and surrounding land uses;
previous environmental reports;
historical site plans; and
observations made during a site inspection.
This information is used to identify potential Areas of Environmental Concern, contaminants that could reasonably be present, and the pathways through which people or the environment could potentially be exposed.
These relationships are brought together in a Conceptual Site Model.
The objective is not to produce the longest possible list of hypothetical contamination sources. It is to identify the sources, pathways and receptors that are reasonably relevant to the site and proposed development.
Does a PSI require soil sampling?
Not necessarily.
A Preliminary Site Investigation can often be completed primarily through desktop research and a site inspection.
However, limited soil sampling can sometimes be useful where a relatively small amount of investigation can resolve an important question.
For example, targeted sampling might provide useful information about shallow fill, a suspected former workshop area or soil within an area proposed for landscaping.
The decision should be driven by the site and the purpose of the investigation rather than an assumption that every PSI either must or must not include sampling.
There is also an important distinction between preliminary sampling and a Detailed Site Investigation.
If the PSI identifies credible contamination risks that require systematic investigation, a small number of soil samples should not be used to artificially avoid progressing to a DSI.
What happens if the PSI recommends a Detailed Site Investigation?
This is where clients can sometimes become concerned that the contamination process will prevent their DA from progressing.
A recommendation for a Detailed Site Investigation does not mean that the site is unsuitable for development.
It usually means that the PSI has identified a contamination source, potential source or material data gap that cannot be adequately resolved using historical information alone.
A DSI is then designed to characterise the nature and extent of potential contamination.
The NSW contaminated land planning framework describes a DSI as appropriate where contamination is present or likely to be present and the available information is insufficient to make planning or site-management decisions.
The investigation might involve soil sampling, groundwater monitoring, soil vapour assessment or another targeted investigation depending on the conceptual site model.
If the investigation demonstrates that the site is suitable for the proposed development, the contamination assessment may conclude at that point.
If remediation is required, the next stage may involve preparation of a Remediation Action Plan (RAP).
Can the DA still proceed if remediation is required?
Often, yes.
The critical planning question is not necessarily whether contamination is currently present.
It is whether Council can be satisfied that the site is suitable or can be made suitable for the proposed use.
This distinction is important.
A former industrial site may contain contamination and still be capable of being redeveloped for residential, commercial or mixed-use purposes where an appropriate investigation and remediation strategy demonstrates how the risks will be managed.
Depending on the site, this process may involve:
PSI → DSI → RAP → Remediation → Validation
Not every site needs every stage.
The purpose of good contaminated land consulting is to establish the investigation and management pathway that is appropriate for the actual risks present at the site.
What if parts of the site cannot be investigated before the DA?
This is relatively common.
An operational commercial or industrial property may still contain buildings, slabs, plant or infrastructure that prevent parts of the site from being physically investigated before demolition.
That does not necessarily make the contamination assessment impossible.
The PSI and DSI should clearly identify these limitations and determine whether enough information is available for the planning authority to make its decision.
Where appropriate, the investigation strategy may recommend additional targeted investigation following demolition or when previously inaccessible areas become available.
For example, investigation beneath an existing building footprint may be undertaken after demolition but before construction of the new development.
However, simply postponing important contamination issues is not an appropriate substitute for investigation.
The DA-stage assessment still needs to provide Council with sufficient information to determine whether the proposed development can reasonably proceed and whether the site is capable of being made suitable.
Whether staged post-demolition investigation is acceptable will depend on the contamination risk, proposed development and the requirements of the relevant consent authority.
This is where designing the contamination assessment around the development program rather than treating it as an isolated environmental report can make a significant difference.
Working with the development rather than against it
A well-designed contamination investigation should be proportionate to the risk and coordinated with the proposed development.
For example, it may make little commercial sense to drill through an operational building simply to investigate soil that will become readily accessible during demolition several months later — provided the remaining uncertainty can be appropriately managed and the planning authority has enough information to make its decision.
Similarly, where a proposed basement will involve substantial excavation, the investigation should consider not only whether contaminants pose a risk to future occupants but also how potentially contaminated soil will be excavated, classified, reused or disposed of during construction.
The proposed development therefore forms an important part of the Conceptual Site Model.
A contamination assessment for a warehouse renovation involving predominantly existing hardstand may look very different from an assessment of the same property being redeveloped into apartments with landscaped communal areas and a basement.
The investigation should respond to those differences.
Can Council require an independent review or certified consultant?
Requirements vary between councils and projects.
Some councils have adopted policies requiring certain contaminated land reports to be prepared or reviewed by consultants holding recognised contaminated land certification.
The NSW EPA itself requires reports submitted to the EPA under the Contaminated Land Management Act 1997 to be prepared or approved by an appropriately certified contaminated land consultant, but the EPA notes that extending this requirement to reports submitted through the planning process is generally a matter for the relevant planning authority.
For more complex or higher-risk sites, Council may also request review by an NSW EPA-accredited Site Auditor.
EPA guidance notes that planning authorities may seek a site audit where they have reasonable grounds to believe information is incomplete or incorrect, wish to independently verify that investigations comply with relevant standards and guidance, or do not have the internal resources to undertake the technical review themselves.
Identifying these requirements early can help avoid reports being prepared and subsequently requiring additional review or rework.
What should you do if Council asks for a PSI?
If a planner, architect or Council officer advises that a Preliminary Site Investigation is required, the first step should be to provide the environmental consultant with as much information about the proposed development as possible.
Ideally, this includes:
the site address and Lot/DP;
architectural or concept plans;
the proposed land use;
known previous uses of the property;
any previous contamination, geotechnical or environmental reports; and
any correspondence or RFI issued by Council.
The consultant can then determine the appropriate scope and whether desktop investigation alone is likely to be sufficient or whether preliminary sampling should be considered.
You can read more about how long a Preliminary Site Investigation takes, how much a Preliminary Site Investigation costs?, and what a Conceptual Site Model is and why it matters in our related guides.
Preliminary Site Investigations for development applications in NSW
Contamination does not have to become a barrier to development.
Addressed early, a Preliminary Site Investigation can identify whether contamination is actually relevant to the project, provide Council with the information required to assess the application and establish a practical pathway for any further investigation or remediation.
Confluence Environmental prepares Preliminary Site Investigations for development applications and planning proposals throughout NSW.
Our approach is to understand the proposed development first, identify the contamination issues that are genuinely relevant to that development and design an investigation pathway that provides the required level of confidence without undertaking unnecessary work.
Where further investigation is required, we can assist with Detailed Site Investigations, Remediation Action Plans, contamination management and validation through the subsequent stages of the development.
If you have been asked by Council to provide a PSI, or you are preparing a DA and want to determine whether contamination is likely to become an issue, contact Confluence Environmental to discuss the proposed development before lodgement.