Conceptual Site Model (CSM)
Summary
A Conceptual Site Model (CSM) is a structured representation of how contamination may be present at a site and how it could affect human health or the environment. It brings together site history, environmental data and professional judgement to describe potential sources of contamination, pathways and receptors.
Definition
A Conceptual Site Model is a qualitative or semi-quantitative description of site conditions that identifies potential contaminant sources, environmental pathways and sensitive receptors. It is commonly presented in both narrative and diagrammatic form.
The CSM evolves as more information becomes available and is refined throughout the investigation and remediation process.
Why Conceptual Site Models Matter
From a technical perspective, the CSM provides the framework for understanding contamination risk. It informs decisions about where to sample, which contaminants to assess and which exposure pathways are relevant.
From a regulatory perspective, councils, regulators and auditors rely on the CSM to assess whether investigations and remediation strategies are appropriate and proportionate to site risk. A poorly developed CSM can lead to unnecessary sampling, missed contamination or approval delays.
From a project delivery perspective, a clear CSM reduces uncertainty by aligning investigation, remediation and validation activities with actual site conditions rather than generic assumptions.
Typical Components of a Conceptual Site Model
A CSM typically identifies and links the following elements:
Sources – potential or known contamination sources such as fuel storage, waste disposal or industrial activities
Contaminants of concern – substances that may pose a risk based on site history
Pathways – mechanisms by which contaminants may migrate, such as soil, groundwater, vapour or surface water
Receptors – people, ecosystems or structures that may be exposed
These elements are often summarised using a source–pathway–receptor framework.
When a Conceptual Site Model Is Developed
A CSM is typically developed and refined during:
Preliminary Site Investigations
Detailed Site Investigations
Remediation Action Plan development
Site remediation and validation
Environmental due diligence assessments
The model is updated as new information becomes available.
Legislative and Regulatory Context
Conceptual site models are embedded within contaminated land assessment frameworks and guidance.
In New South Wales, regulators and councils expect PSIs, DSIs and remediation documentation to demonstrate a clear and logical CSM that supports investigation scope and conclusions. Similar expectations apply across Australia.
A defensible CSM is a key indicator of assessment quality.
How We Can Help
Confluence Environmental develops and applies conceptual site models across contaminated land and remediation projects.
Our services typically include:
Development of site-specific CSMs
Refinement of CSMs as investigations progress
Use of CSMs to guide sampling design and risk assessment
Integration of CSMs into remediation and validation strategies
Clear documentation to support regulatory review
We focus on CSMs that are practical, transparent and aligned with site conditions.
Related Terms and Concepts
Contaminated Land
Preliminary Site Investigation
Detailed Site Investigation
Remediation Action Plan
Site Remediation
Site Validation
Environmental Site Assessment