In large-scale construction projects, site situation and surrounding environment can change daily. This is due to multiple factors acting as “incident catalysts”, like less, or un-skilled workers, outsourcing, more complex construction phases (heights or confined spaces), under pressure working conditions, as well as changes in environmental conditions (e.g. wind, temperature, etc.). It is essential to acquire a statistical significant reference concerning the unsafe acts and risky behaviour to implement proactive measures preventing occurrences of major incidents. In this paper, the construction phase in the Middle East of one of the world’s largest oil and petrochemical integrated complex was considered. Starting from the accident/incident pyramid approach, management, direct field supervisors, as well as subcontractors were involved in the development and upgrading of a Multilayer Reporting System, covering any risk behaviours, unsafe situation, violations or acts, safety or environmental issues, near misses as well as minor, or major accidents. The modular approach provided a comprehensive overview of the core human and technical issues in the construction and testing of the process plant, suggesting how to implement technical and managerial solutions to handle them effectively, reduce the likelihood of errors, violations and avoid damages to the facilities, environment and humans.