Detailed Design and Preparation of Tender Documents for Upper Tamakoshi HEP(463 MW)


Funding Agency: Government of Nepal/Nepal Electricity Authority
Client: Nepal Electricity Authority
Date: March 2007 – December 2008

The project was located in Tamakoshi river in Gongar Gaon, Lamabagar VDC of Dolakha District. This project with an installed capacity of 456 MW was design to generate an annual average of 1,737 GWh of electrical energy.

The project was a Peaking Run-of-River (RoR) hydropower development with limited storage capacity in intake pond for daily peaking operation. The design discharge of the plant was 66m3/s and gross head of 822 m. Total catchment area was 1,745 Km2 with two Settling Basins 0f 552 m long each.

Environmental Impact Assessment (EIA) report concluded that the project is an environmentally friendly project with few adverse impacts compared to most other comparable hydropower projects.

The 35 m wide and six inlet openings intake was an integral part of the dam structure, following which the water is conveyed through two parallel 130 m long concrete culverts to the twin settling basins, each of 225 m long and 26 m wide. The headrace tunnel, with a total length of 7.9 Km had a gross excavation cross sectional area of 32 m2 and excavated by drill and blast methods. The surge system comprised a 172 m long link tunnel, branching off the headrace tunnel about 220 m upstream of the top of the penstock shaft, connecting with a 360 m high vertical shaft incorporation a system of horizontal surge chambers at two levels. The powerhouse cavern was 15 m wide, 29 m high and 142 m long the transform cavern was 13 m wide, 12 m high and 167 m long, with a 32 m long central excavated to a height of 17.5 m to accommodate the GIS. The tailrace tunnel comprised of total length of 3 Km with its cross sectional area of 35.0 m2. The evacuated power was transmitted through 47 Km long 220 KV double circuit Transmission line up to khmiti Sub-station.

Infrastructure works, viz., further upgrading of the Public Access Road between Charikot to Lamabagar as required in order to provide the agreed level of trafficability for all the Project contractors, the maintenance including any necessary repair work of the Access Road, construction and maintenance of various site access roads (construction road), other facilities and services to be provided to the all professional or non-professional staffs.

Overall Services provided:

TMS provided local logistics and project management support. Services being provided by TMS were in the areas of hydropower design, geological works, and social development.

However, TMS was involved in following activities (supporting role):

  1. Field Investigations: This includes topographical survey, hydrology and sediment transport, GLOF, Geological and geotechnical investigations, provisional work and environmental investigations and preparations;
  2. Hydrological, Hydraulic Studies and Sediment Transport Study
  3. Detailed Environment and Social Studies,
  4. Detailed Engineering Design, Specifications and Drawings
  5. Preparation of tender Documents;
  6. Construction Plan and Schedules;
  7. Engineer’s Cost Estimates.
  8. Preparation of Environmental and Social Mitigation Management Plan