Until the end of the 20th century, single user sites were the norm in Europe, but in the last 10 years, the situation has changed. Today, especially in the chemical industry, sites are operated by several companies with facilities close to one another.

Beyond business interests, multi-operator sites can offer great advantages to deal with environment, safety, security and emergency management. But, this change generates new risks, because of the interdependence between different companies, and calls for a new organization of risk management at site scale.

For managing overall risk, it is necessary to define a minimum of common rules. In particular, companies should be encouraged to conclude clear and efficient contracts between themselves. These contracts under private law are very flexible and can be easily updated to accompany the development of sites.

The aim of this paper is to highlight the main issues brought by this new kind of organization and to present INERIS' conclusions on appropriate contracts between operators (conventions) and efficient risk management on each site.