Site-specific quantitative risk assessment (QRA) modelling is a fundamental component in any environmental site assessment or environmental toxicology assessment. Specialist computer risk modelling tools are available that simulate the transport of contaminants through soil, water and atmospheric media and assess their likely effects on exposed receptors. These receptors often include human beings who may be exposed to contamination via ingestion, inhalation and dermal contact pathways, or environmental receptors such as aquatic and terrestrial ecosystems. Models can be run in forwards' mode to determine point of exposure (PoE) concentrations for comparison with the pertinent quality standards, and backwards mode to derive site-specific target levels (SSTLs) for remediation where POE concentrations exceed soil or water quality standards.

Modelling scenarios can vary in complexity and it is important that the selected model is appropriate to the circumstances being assessed. A complex hydrogeological system may require the use of a multi-layered model, which can assess the transport and partitioning processes occurring in discrete hydrogeological units along the contaminant migration pathway. Stochastic (probabilistic) modelling tools are useful in assessing the significance of variability present in the modelled scenario, the results of which are generally reported in terms of probability of occurrence and degrees of confidence.

Used diligently QRA modelling will ensure that any risk management measures are targeted where they are actually required and hence ensure that a client's money is not spent unnecessarily or inappropriately implementing an over- engineered solution. Consequently QRA modelling is an essential component of the value-engineering process. SLP offer a comprehensive range of deterministic and probabilistic quantitative risk assessment (QRA) modelling services. Our expertise includes undertaking detailed QRA modelling exercises for human health, groundwater, surface waters and ecosystem receptors. Our in-house experts have delivered some of the most challenging modelling assignments in the environmental sector and written and presented on the topic internationally.

SLP utilise a number of specialist modelling tools, the selection of which will be governed by site-specific circumstances and objectives. Our expertise includes the use of the following tools: