The object of the study was the main pipeline in East Siberia -Pacific Ocean. The main pipeline works in difficult conditions, therefore the assessment of the risks of accidents is absolutely necessary. The combined risk assessment method consisting of the Checklist expert evaluation and the Fault Tree was used in the article. The Fault Tree samplewas suggested for described case study. The standard Checklist questionnaire was revised and expanded from 10 to 50 questions, to get more accurate accidents' risk assessment. The scenario of pipeline depressurization frequencies was also considered. The actual emergencies and incidents registration form was proposed. The ranking of main pipeline sections by accident rate was carried out. The software for systematization risk assessment data and accurate accident predictions is planned to be created during further research.