Risk Assessment

Risk assessment is central to the investigation of land contamination. It involves gathering information about a site, through desk studies, walkover surveys and intrusive investigations and, dependent upon the environmental setting and current or proposed use, making an informed judgement on the risk or liability associated with the contamination present and the requirement for measures to mitigate the risks identified.

The significance of the potential risk, to human health or the environment, is determined through a combination of the probability of occurrence and the potential severity of the consequence.

At TGEN the process of risk assessment is undertaken in accordance with Model Procedures for the Management of Land Contamination (Environment Agency 2004) - CLR11 and is broken into various stages as detailed below:-

• Phase 1 Preliminary Risk Assessment (PRA) – site reconnaissance, desk study and the production of a preliminary conceptual site model (CSM).
• Phase 2 Generic Quantitative Risk Assessment (GQRA) – Comparison of information/data gathered during site investigations and environmental monitoring against appropriate generic assessment criteria (GAC) in order to refine the preliminary CSM.
• Phase 2 Detailed Quantitative Risk Assessment (DQRA)- Comparison of information/data gathered during site invesitgations and environmental monitoring againset site specific assessment criteria (SSAC) where necessary using fate and transport modelling techniques to assess risks from identified contaminants to sensitive receptors in order to further refine the CSM.
• Phase 3 Remediation – Options appraisal and implementation of measures to mitigate the risks identified to human health, controlled waters and other sensitive receptors to acceptable levels.
• Phase 4 Verification and Closure – Provides confirmation of the success of the remediation process, required for regulatory “sign-off”.

The process detailed above is phased, such that the outcome of each phase will determine the scope of, or in fact need for, the proceeding phase. In many cases regulatory approval is required at the conclusion of each phase prior to proceeding to the next.

All sites and scenarios are different, which as a result means that investigations need to be tailored to our clients specific requirements. Therefore at TGEN we aim to ensure that all aspects of our site investigations not only address the specific requirements of our clients, but also address the demands of the local planning authority and the Environment Agency within the regulatory and planning framework.

An investigation may require part or all of the Phases 1-4 to be undertaken to fully assess and mitigate risks from contamination. If you would like further information on other aspects of the contaminated land investigation process then please see the following pages. Alternatively if you require additional advice or have a question relating to a specific site please contact us at info@terragenenvironmental.co.uk