[holding answer 22 June 2009]: Public information zones (PIZs) around large-scale petrol storage depots and other COMAH ‘top-tier’ onshore non-nuclear major hazard installations are rarely circular. They reflect the effect of site specific conditions, for example, the quantities and locations of hazardous substances stored on the site, and the influence of local weather conditions. PIZs range from a few hundred metres for sites storing flammable substances to a few kilometres for sites storing toxic substances.
The PIZ around a single, large scale petrol storage tank has a radius of 400 m from the edge of the tank’s circular bund. However, most large-scale petroleum storage sites have more than one storage tank, and in some cases the PIZ will extend beyond 400 m due to the presence of the other hazardous substances.
To provide details of the PIZs for all ‘top tier’ COMAH sites, including large-scale petrol storage depots, could be provided only at disproportionate cost.