12

Technological Risk Prevention Plans are a legal obligation in France since the July 30th, 2003 Law for industrial sites classified as Seveso High Threshold. Their purpose is to plan measures for risk reduction at the source and to act on urbanization to protect populations and activities situated in the surrounding area. They must be developed through dialogue between the State representatives, the local authorities, the industrialists and the local population. The stakes are multiple: this may involve expropriation or consolidation work on their houses for the inhabitants, limitation of urbanization in the case of elected representatives, and expensive measures towards risk reduction for industrialists. Nevertheless, the considerable asymmetry between the actors in terms of technical knowledge results in biasing the dialogue. This is due to the fact that the method of calculation and the nature of the risks taken into account in the studies of dangers in order to define the mapping of hazards are particularly complex. We also show that paradoxically the lack of knowledge and information becomes a strategic resource for certain actors participating in the plan.