A Conceptual Site Model (CSM) is the central analytical tool in contaminated land risk assessment. It describes the characteristics of a site in terms of potential contaminant sources, the pathways by which those contaminants might migrate, and the receptors (human health, controlled waters, ecosystems, or property) that could be affected.

The CSM is developed during the Phase 1 desk study using information gathered from historical mapping, environmental databases, geological data, and the site walkover. It is refined and updated during the Phase 2 site investigation as measured data from soil, groundwater, and gas sampling becomes available.

A complete source-pathway-receptor linkage is known as a pollutant linkage. For a contamination risk to exist, all three elements must be present and connected. If any element is absent or can be broken, the risk is managed.

For example:

Source: Historical fuel storage tank (identified from mapping)
Pathway: Migration through permeable made ground and shallow groundwater
Receptor: Future site users (residential end use) and underlying aquifer

The CSM is typically presented in both written and diagrammatic form — a cross-section showing the geological strata, contaminant locations, and potential migration routes provides a clear visual summary for regulators and stakeholders.

The LCRM framework requires the CSM to be the basis of all risk assessment decisions. Generic Assessment Criteria and site-specific risk calculations are applied to the pollutant linkages identified in the CSM to determine whether risks are acceptable or require remediation.

Aegaea develops robust CSMs as part of our contaminated land assessment services, ensuring they are clear, defensible, and satisfy the requirements of Environmental Health Officers and the Environment Agency.