Preparation of DPR and Detailed Engineering Design of Khare Khola Hydroelectric Project including EIA Study of Transmission line

Project Description

Khare Khola is a major tributary of Tamakoshi with a total Catchment area at intake of 150km2 with significant snow cover. The Project was designed as a run of the river project with 2.8m diameter, 5 km long tunnel as the main water conveyance system. The design hydrological parameters were:
• Design discharge = Discharge with 40% exceedance probability (Q40) = 8.43 m3/s
• Design flood(Flood,Q100) = 273 m3/s at intake
• Minimum monthly flow = 2.80 m3/s
Project Configuration: Diversion weir has been designed as a simple overflow weir without control gates. The diverted water passes through a gravel trap, approach canal to the surface settling basin designed to settle 0.2mm and larger particles with 90% efficiency. The size of the settling basin is 100m long, 2 bays of 5m wide by 5.42m deep with transitions at both ends of 18m. The clear water from the settling basin is conveyed to the tunnel through a rectangular covered RCC pipe. Considering constructability aspect and hydraulic considerations a 2.8 m diameter D-shaped headrace tunnel with maximum height at the crown of 3.0m is designed. The total length of the tunnel from the intake portal to the surge shaft is 4,796m which excludes adit tunnel length. The penstock pipe arrangement consists of about 870 m long steel pipe of internal average diameter 1700 mm after the surge shaft. The powerhouse is 35m long x 18 m wide x 14 m high. Adjoining to the powerhouse is a conventional switchyard with dimensions 64mx44m such that the overall plan area occupied by PH and SY is around 80mx70m. This project utilizes a gross head of 343.85m between the NWL at intake of 1538.35 masl and the turbine axis at an elevation of 1194.50 masl and the net head at rated discharge is 333.8 m.
Power and Energy: The proposed power plant has an installed capacity of 24.1 MW with 150.602 GWh average total annual energy generations, which after deduction of transmission loss, self consumption and outage results in the net average annual saleable energy of 143.07 GWh, which includes dry energy of 23.19 GWh and wet energy of 119.89 GWh.
Transmission and Power Evacuation: Generated power from the KKHEP will be evacuated through the NEA’s proposed 132 kV substation located at Singati, Dolakha. For the power evacuation to the 132 kV line, about 11 km long transmission line will have to be constructed by the developer from proposed 33/132 kV switchyard of KKHEP powerhouse.
Capital Cost: Total capital cost of the Project based on DPR level design comes to be 3,100 million NPR, which gives the cost per kilowatt installed capacity as NRs 128,617 (USD 1,649/kW). This total includes VAT, other taxes and owner’s development costs. The study report was submitted to Department of Electricity Development (DOED).

Assignment Description

The services provided included the following under the components, hydropower, transmission line, access road, tunnel & misc. works: • Survey and Investigation: This included detailed topographical survey, hydrological survey, geological/geotechnical survey and investigation including Electrical Resistivity Tomography (ERT), and soil & materials survey • Review of past study document • Capacity optimization • Social & environmental study with action plan • Economic and Financial Analysis • Prepared upgraded Feasibility study (FS) and Detailed Project Report (DPR) • Detailed Design of the Project • Tunnel Design Works • Civil Design Works • Electromechanical Design Works • Hydro-mechanical Design Works • Tender Contract Document Preparation Civil design consisted in hydraulic and structural design of facilities for diversion of water, exclusion of sediment and conveyance of water from intake to the turbine and the design of powerhouse to accommodate the electro-mechanical equipment for power production. The design philosophy has remained to design these structures as small and light as is just required to serve the purpose and keep functional all the time with minimum closure. Electromechanical design consisted in selection of the type of turbine and number of units and determining the specification for the current generator, transformer and all appurtenant equipment. Environmental Impact Assessment (EIA) The Environmental Impact Assessment (EIA) was conducted as per the prevailing regulation of EPA, 1997 and EPR, 1997. The specific assignments completed included: • Review of Plans / Policies, Legislation, Guidelines and Conventions • Preparation and approval of Scoping Document and Terms of Reference • Field investigation and primary data collection of Physical, Biological and Sociological Environmental Data • Analysis and evaluation of beneficial and adverse impacts on Physical, Biological and Sociological Environments • Alternative analysis for project layout, designs, schedule and technology • Identification of beneficial augmentation measures and adverse impact mitigation measures • Preparation of detailed Environmental Management Plan (EMP) for the Project • Preparation of Environmental Monitoring and Environmental Auditing Plan • Extensive public consultation and public hearing in the Project Area • Preparation and approval of Final EIA Report