Abstract: High intensity precipitations occurred in Xichang area since June of 2012. In August, several debris flows, rock falls and landslides occurred along the 500 kV transmission line from Jinping Hydroelectric Power Station and Xichang Convert Station. These geological hazards had potentially threatened the safety of the transmission tower foundations. The site reconnaissance results indicate that, in addition to the high intensity rainfalls as well as the complicated and fragile geological condition of the Southwest Mountain areas, the damage of the vegetation and the improper placement of the waste soil near the tower foundations are the factors that triggered the geological hazards. When the tower foundations are located on the potentially instable geological formations or are threatened by the geological hazards and the mitigation measure is impossible or cost prohibitive, the transmission options should consider the relocation, realignment, or span over. When no other relocation option is feasible, the geological hazard mitigation measures have to be considered. Different triggering mechanisms among the landslide, rock fall and debris flow lead to different mitigation considerations. The paper summarizes the frequent geological hazards occurrence characters of Southwest Mountain areas and the lessons learned from the transmission design and construction in these areas.

Key words: High and Steep Slopes, Landslides, Rock Falls, Debris Flows, Prevention and Mitigation of Geological Hazards