Numerical Risk Assessment and Land Use Planning

The proposed siting of new chemical Hazardous Installations, modifications to existing Hazardous Installations, and proposals for development within the vicinity of these installations, are assessed by the Hazardous Installations Directorate (HID) of the Health & Safety Executive. Numerical risk assessment methodology is utilised to enable advice to be given to Local Planning Authorities. The use of ‘top down’ Quantified Risk Assessment methodologies is well established in these circumstances. HID also uses simplified ‘Risk Integral’ techniques to enable decisions to be made on a consistent basis at low cost. This paper describes the application of these numerical techniques with actual case studies which illustrate the methodologies and decision making criteria. The subsequent consideration and provision of risk reduction measures is also described with examples. The implications for the successful management of off-site risk are discussed.