Environmental risk assessment of earth dams in the construction and operation phases using the modified fuzzy FMEA method

The investigations have shown that the construction of the dam and its related facilities have significant physical–chemical and ecological effects on the ecosystem. Failure Mode and Effects Analysis (FMEA) is a technique for ranking risks in projects to construct dams, but it has many deficiencies and ambiguities. Therefore, to prevent the shortcomings of the classical method, the modified fuzzy inference system (MFIS-FMEA) method has been used by creating a two-stage model to assess the risk of Eyvashan Dam more accurately. This work uses two-stage fuzzy reasoning and a Max–Min combination rule. When severity (SEV) and occurrence (OCC) variables are combined, the critical risk index (RCI) values are predicted in the first stage. The RCI and detection index (DET) input are then used to predict the MFIS-RPN in the second stage. The risk priority number (RPN) results in the MFIS-RPN method are much more accurate and serious than the FIS-RPN method due to the two-stage nature and the use of new language terms. The results of the proposed MFIS-RPN technique show that the highest RPN was obtained with immediate action in the dam construction phase for soil erosion and soil pollution and in the dam operation phase for aquatic and water pollution. The comparison of results shows an increase of 1 to 109 and 53 to 171 percent of RPN score in MFIS method compared to FIS method for the construction and operation phases, respectively.