Combination of indexing system method with analytical hierarchy process to assess the environmental risks in gas-transfer pipe lines

In the present research, combination of Indexing System Method with Analytical Hierarchy Process has been applied to assess the environmental risks of gas transfer pipe lines. By this process, classification and qualification of the numerous types of environmental risks would be accessible. Sum Index and Leak Impact Index indicate risk probability and risk severity, respectively. In this regard, total environmental risk is calculated based on multiplication of total risk probability in risk severity. Analytical hierarchy process is applied to evaluate the factors because of differences existed in the total effective level of these factors. For this purpose, Tasooj- Salmas gas transfer pipe line, 24 inch in size and 42 km in length was selected to study the environmental risks. Using geographical information system, investigated risks have been classified throughout the pipe line route. Results showed that 46 %, 48 %, 2 % and 4 % of the total studied pipe line is exposure to the high risk level (5467 - 6054), average risk level (6055 - 6641), low risk level (6642 - 7228) and very low risk level (> 7228), respectively. Vicinity of the southern part of the studied site with National park of Orumieh Lake is considered as the most vital ecological concern of this study. However, 15 km (18-33 of 220 km) of the total pipe line has been located at the 5 km from the considered biosphere reserve. Among the most crucial risk factors of the present project are Third Party Damage Potential, as well as natural potentials (Soil displacement).