The access road that includes the road tunnel to Upper Arun Hydroelectric Project (UAHEP) is situated in Bhotkhola Rural Municipality of Sankhuwasabha district in Province 1. UAHEP of 335 MW installed capacity is on a high priority among other hydropower projects being developed by NEA due to its expected low generation cost and high availability of firm power. Geologically most of the area of project lies in the tectonic window of the Lesser Himalaya. The project area has diversified topography from deep gorges, gullies, steep slopes and high mountains and valleys.
The access road to UAHEP starts from Koshi Highway at Gola village. After crossing the proposed bridge over Arun River the road alignment turns towards the downstream and then ascends up with few hairpin bends and reaches Sibrung village at elevation of 1620 m. From Sibrung the alignment follows contour with mild gradient passing through Hema village and reaches Namase village where some hairpin bends are planned. The alignment reaches southern portal of 2.03 km long tunnel which is located at the approximate height of 2020 m. After northern portal of the tunnel, the alignment reaches Rukuma village where it descends with some hairpin bends. Afterwards, it follows contour and reaches intake site. The elevation of intake site is about 1620 m total length of this road section is about 21.65 km including tunnel and located in steep terrain.
Similarly, the access road for Ikhuwa Khola Hydropower Project (IKHPP), the proposed construction power for UAHEP starts from Koshi Highway section near Simmuwa village at approximate elevation of 1370 m. It descends north east towards valley (Arun River) with various hairpin bends, traversing along steep hill slope. It passes through forest and agricultural land and reaches the proposed bridge site which connects bottom hill of Uwa village to Sirutar village. Sirutar village is where powerhouse site of IKHPP is located.
I was employed by East Management & Engineering Services Pvt. Ltd. which took the responsibility of geological and geotechnical investigation of the access road for the JV consultants. I was involved in this project to evaluate the overall geological condition for the proposed access road of the project in terms of rock mass assessment, stability condition, potential source of aggregates. Major activities include geological/engineering geological mapping of road and road tunnel, discontinuities survey, rock mass classification, and slope stability analysis using 2D program called Slide2.