Design Review, Capacity Optimization, Updated Feasibility Study and Design of Tamor-Mewa Hydroelectric Project including Transmission Line

Project Description

The Tamor-Mewa hydroeletric project is the combined scheme of Tamor (128MW) and Mewa (30MW) with an installed capacity of 158 MW. Where the flow from Mewa Khola will be diverted through a 4.5 km tunnel to generate 30 MW power and the discharge from the tailrace of Mewa will be diverted into the Tamor headworks. The combined flow will be diverted through 5.1 km of tunnel to generate 128 MW power at Tamor Powerhouse. The design hydrological parameters are:

• Combined Catchment area = 2712 km2
• Design Discharge
Mewa = 27.24 m3/s
Tamor = 96.49 m3/s
• 1 in 1000 years flood for combined scheme = 2429 m3/s

Mewa Scheme:
• Headworks at Sriganga with a simple ogee shaped concrete diversion structure of crest length 30mand 5m height above bed level and undersluice with two gates of size 4mX 3m
• Surface settling basin of size 105m X 14mX 8m (l XBXH) – 2 basins
• Headrace Tunnel of length 4200m (horseshoe, 14m2 finished cross sectional area.)
• About 30m long Surge Tunnel (finished dia. 12m) at the proximity of valve chamber
• Drop shaft (finished dia. 2.75m) of 188.5m length.
• Surface power house with size 40m X 16m and height 11m from OGL (total 17m)
• Tailrace connected to headworks of Tamor

Tamor Scheme (Combined with Mewa Flow):
• Concrete gravity ogee shape headworks with height 5m from bed level and crest length of 63.5 m
• Flushing undersluice with two gates of size 5mX 5.
• Desanding basin of size 200m X 22mX 14 m (3 basins)
• Headrace tunnel length 4740m with mostly concrete lining and cross-sectional area of 50 m2
• Surge tank of height 35m and diameter 18m
• Drop shaft of length 99m and diameter 5.4m
• Underground power house of size 17mX 26m X 66m
• Underground transformer cavern of size 48m X 12m X22m
• Tailrace tunnel 500m length.

Power and Energy: The Proposed project has combined installed capacity of 158MW with 828.25GWh total annual energy generations, which includes dry energy of 100.66 GWh and wet energy of 727.58 GWh.

Transmission and Power Evacuation: Generated power from the Mewa Powerhouse will be transmitted to the Tamor powerhouse’s substation through 8 km 132 KV transmission line. The total power generated from combined shceme will be evacuated through 16 km long 132 kv transmission line at Kabeli substation.

Capital Cost: Total Capital cost without IDC of the Project based on updated feasibility study comes to be 222.09 million USD, which gives the cost per kilowatt installed capacity as 1405 USD.
The study report was submitted to Department of Electricity Development (DOED).

Assignment Description

The services provided included the following under the components hydropower including tunnel, transmission line, and misc. works: • Survey and Investigation: This included detailed topographical survey, hydrological survey, geological survey and geo-physical investigation. including ERT, SRT, MAM combined with MASW, seismic Hazard Analysis • Review of past study document • Capacity optimization • Economic and Financial Analysis • Prepared upgraded Feasibility study (FS) and Detailed Project Report(DPR) • Updated Feasibility Study included: • 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 (tunnel etc.) 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.