The project consists of preparation of Detailed Engineering Design & tender documents of camp facilities, civil works, hydro-mechanical & electro-mechanical works of Upper Brahmayani Hydroelectric Project (BHEP – 19 MW), and other assignment as per ToR. The proposed Brahmayani Hydroelectric Project (BHEP) will utilize the flow available in Nyamya Masal Khola which is merges with Lagan Khola at Ladanbesi to form Balephi Khola, which later merges with the Sunkoshi River, the main tributary of the Sapta Koshi River Basin.
UBHEP has already completed a Power Purchase Agreement (PPA) with NEA and obtained the Survey License from DOED with a project capacity of 15.15 MW based on releasing 50% of downstream release from monthly flows. However, as per the recently amended guidelines of Physical Infrastructure Development and Operation in the protected areas, 2080 only 35% of the mean monthly flow is to be released as a downstream release for the project whose entire project layout lies in a protected area and has plant capacity lies below 25 MW. Therefore, the required downstream release is 35% of the mean monthly flow from Nyamya Masal Khola for power generation of UBHEP. The plant’s installed capacity is 19.00 MW as per updated project layout with a design discharge of 5.40 m3/s considering a gross head of 442 m and after downstream release.
As per the Updated Feasibility Study Report (Sept. 2024), the design discharge from Nyamya Masal Khola is 5.40 m³/s at a probability exceedance of 48.89%. The diversion weir (WCL 3070 m amsl) is located about 80 m downstream of the confluence of Nyamya Masal Khola (originating from Jugal Glacier) and a tributary from Dorje Lakpa Glacier. The headworks, including the diversion weir, intake, undersluice, gravel trap, and desander, are situated on the right bank of Nyamya Masal Khola. Similarly, the project waterways headrace pipe (1.5 m dia., 3,350 m length), surge pipe (3 m dia., 90 m length), and surface penstock (1.15–1.25 m dia., 1,674 m length) are located along the right bank. The proposed surface powerhouse is on the left bank of Lagan Khola, just upstream of the Nyamya Masal & Lagan Khola confluence at Ladanbesi, and will house two vertical-axis Pelton turbines. A bypass with an energy-dissipating structure is included to control water velocity during turbine shutdown and safely convey flow to the downstream headpond. If the downstream project is inactive, discharge will be released via the tailrace into Lagan Khola. Generated energy is planned to evacuate to the substation at the Brahmayani Hydroelectric Project (45 MW) via a 6 km, 132 kV single-circuit line, and subsequently to Pantang Sub-station through a 15 km, 132 kV dedicated single-circuit line.