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Mathilo Mailung Khola Jalvidhyut Aayojana (14.3 MW)

Technical Summary

Mathillo Mailung Khola Jalvidhyut Aayojana (MMKJA) is a 14.3 MW run-of-river (RoR) project located on Uttargaya Rural Municipality ward no: 1 (Previously Haku and Dadagaun VDC), Rasuwa District, Province No. 3 Nepal. The project is being developed by Mathillo Mailun Khola Jalvidhyut Ltd. Shankha Park, Dhumbarahi, ward no. 4 Kathmandu M. C., Nepal (hereinafter referred to as “the Employer”). The license boundaries of the project area are: latitude 28º 08’ 00” N to 28º 05’ 56” N, and longitude 85º 11’ 00” E to 85º 13’ 00” E. The project diverts Mailung River with a watershed area of 72 km² at the proposed Intake.

The proposed Headworks of MMKJA consists of Boulder Lined weir, gated Undersluice, Side Intake with two orifices, Gravel Trap, Approach culvert, two chambered Settling basin and Headrace Canal up to Headrace tunnel Inlet portal. The Headrace tunnel (HRT) is proposed to be of inverted D-shaped. It is planned to excavate the Headrace tunnel from two different faces namely: HRT Inlet portal and HRT Outlet portal. An underground Forebay is proposed at the end segment of Headrace tunnel about 157 m upstream side of the HRT Outlet portal. An underground steel Penstock pipe with two vertical shafts and an inclined tunnel will convey water from underground Forebay to surface Powerhouse which accommodates two generating horizontal axis Pelton Turbines. After generating power, the diverted water will be discharged back to Mailung River through a Tailrace culvert. There will be 11/132 kV Switchyard beside the Powerhouse. From the Switchyard, the generated power will be evacuated to Integrated Nepal Power System (INPS) through a 15 km long, 132 kV transmission line up to Trishuli 3B Hub Substation of Nepal Electricity Authority (NEA) which is under construction.

The Headworks area of MMKJA is located in Uttargaya Rural Municipality ward no. 1, Phedi Odar. The Weir axis is located approximately about 2050.5 m (weir crest level) above mean sea level (amsl). The Headrace tunnel alignment passes through right bank of the Mailung River which is approximately 1855 m up to Forebay. The Powerhouse is proposed to be located on the right bank of the Mailung River in Uttargaya Rural Municipality ward no. 1, at confluence of Raman Kholsi and Mailung River towards Mailung River. At the Powerhouse location, the terrace is narrow and the vertical shaft lies just 170 m upstream of Powerhouse location. The entire project components such as Headworks, Headrace tunnel, Forebay, Penstock, Vertical Shaft, and Powerhouse lie at right bank of Mailung River in Uttargaya Rural Municipality.

Salient Features

 

                                                              Location

Province 3 (Former Central Development Region)
District Rasuwa
Rural Municipality

Uttargaya Rural Municipality (Former Haku

and Dadagaun VDCs.)

Nearest Town Trishuli Bazar
Headworks

Uttargaya Rural Municipality, Ward No. 1,

Rahare Village

Powerhouse

Uttargaya Rural Municipality , Ward No. 1,

Gyangsilung Village

Geographical Co-ordinates

Latitude 28° 05’ 56” N to 28° 08’ 00” N
Longitude 85° 11’ 00” E to 85° 13’ 00” E

General:

Name of River Mailung
Type of Scheme Run-of-River
Gross Head 495.5 m
Installed Capacity 14.3 MW

Hydrology

Catchment Area at Intake site 72 km2
Average Flow 7.65 m3/s (minimum mean monthly flow1.02 m3/s)
Design Flow

3.53 m3

/s (40 % exceedance flow)

Design Flood (Q100) 166 m3/s

Diversion Weir

Type Boulder Lined Weir
Crest Elevation 2049.00 m above msl
Maximum Flood Level 2051.60 m above msl
Crest Length 25.50 m
Maximum height 5 m (from the original ground level)

ndersluice

No. of Bays 1
Invert Elevation 2043.50 m above msl
Size (B X H) 2.5 m x 3.0 m

Intake

Type Side Intake
Number of Orifices 2
Bottom Elevation of Orifice 2046.45 m amsl
Top Elevation of Orifice 2047.75 m amsl
Size (B X H) 2.0 m x 1.3 m

Gravel Trap

Type Surface, RCC, Hopper Shaped
Particle size to be settled ≥ 5 mm
Number of Chambers 1
Size (L x B x H) 7.0 x 5.0 x 2.6 m

Gravel Flushing Culvert

Number 1
Size (B X H) 1.0 m x 1.0 m
Length 26.69 m

Approach Canal

Type RCC, Rectangular Shape
Number of Bays 2
Size (B x H) 1.1 x 2.7 m
Length 15.48 m
Longitudinal bed slope 1:800

Settling Basin

Type Surface, RCC, Hopper Shaped
Particle size to be settled ≥ 0.15 mm
Number of bay 2
Length

60 m, additional 27.80 m length in inlet

transition

Dimension ( B X H ) 6 m x 3.05 m (each)
Particle Trap efficiency 90 %
Longitudinal slope 1 : 50

Sediment Flushing Culvert

Number 2
Size (B X H)

1 m x 1.5 m before junction, 2 m x 1.5 m

after junction

Length

23.6 m ( one 13.1 m another 10.6 m)

before junction, 7.7 m after junction

Headrace Tunnel

Type Free Flow
Shape Shape
Shape 1736 m
Excavation Size (B x H) 2.8 m x 2.8 m
Longitudinal Slope 1:1000
Support System Concrete Lining, Rockbolts and Shotcrete

Forebay

Type Underground, Rectangular
Size (approx. B x H) 5.00 m x 8.30 m
Length 46 m (including transition)
Side Spillway Size (B x H) 1.65 x 1.00

Spillway Tunnel

Type Free Flow
Shape Inverted D
Length 180.67 m
Excavation Size (B x H) 2.8 m x 2.8 m

Shape and Size of Spillway trench(for spilled

water passage)

Rectangular (1.1 m X1.1 m )
Support System Concrete Lining, Rockbolts and Shotcrete

Connecting Tunnel (Spillway tunnel to Penstock tunnel)

Shape Inverted D
Length 55 m
Excavation Size (B x H) 2.5 m x 2.5 m

Penstock

Total penstock Length 1172.378 m
Diameter 1.20 m
Thickness 6 mm to 40 mm

Penstock

Total penstock Length 1172.378 m
Diameter 1.20 m
Thickness 6 mm to 40 mm

Penstock Tunnel

Horizontal tunnel 01

Shape D shaped
Size 2.5 m x 2.5 m
Length 151.575 m

Vertical Shaft 01

Shape Circular
Diameter 2.25 m
Height 224.567 m

Horizontal tunnel 02

Shape D shaped
Size 2.5 m x 2.5 m
Length 298.892 m

Vertical Shaft 02

Shape Circular
Diameter 2.25 m
Height 189.97 m

Horizontal tunnel 03

Shape D shaped
Size 2.5 m x 2.5 m
Length 227.473 m

Adit Tunnel

Shape Inverted D
Length 70.73 m
Excavation Size (B x H) 2.5 m x 2.5 m
Longitudinal Slope 1:22.6
Support System Concrete Lining, Rockbolts and Shotcrete

Penstock Pipe

From Forebay to Outlet Portal

Diameter 1.20 m
Length 1092.477 m
Thickness 8 mm to 36 mm

From Outlet Portal to Bifurcation

Diameter 1.20 m
Length 51.163 m
Thickness 36 mm to 40 mm

From Bifurcation onwards up to reducer

Diameter 0.85 m
Length 5.0 m (Branch 1) & 14.918 m (Branch 2)
Thickness 36 and 40 mm

After reducer

Diameter 0.63 m
Length 3.44 m (Branch 1) & 5.4 m (Branch 2)
Thickness 20 mm and 25 mm

Powerhouse

Type Surface
Size (L x B x H) 40.60 m x 14.00 m x 13.10 m

Turbine

Type Horizontal Axis Pelton Turbine
Number of Unit 2 (Two)
Turbine Capacity per Unit 7500 KW
Discharge per Unit 1.765 m3/s
Turbine Axis Elevation 1553.50 m amsl
Turbine efficiency 89%

Generator

Type of Generators Three phase, Synchronous
Number of Unit 2 (Two)
Rated Output 8500 kVA
Generation Voltage 11 kV
Frequency 50 Hz
Power Factor 0.85
Excitation System Brushless
Generator efficiency 95.5%

Transformers

Type Three-Phase, Oil immersed
Number of Units 1 (One)
Rating 18500 kVA
Frequency 50 Hz
Voltage Ratio 11kV/ 132 kV
Transformer Efficiency 99.00%

Tailrace Canal

Type RCC, Rectangular
Size (B x H) 1.40 m x 1.90
Length 14.50 m and 9.00 m

Power and Energy

Installed Capacity 14.3 MW
Dry energy 13.16 GWh
Wet energy 66.51 GWh
Annual Net Energy Output 79.67 GWh

Transmission Facilities

Transmission Voltage 132 kV
Transmission Line Length 11 km
Connection Point Trishuli 3B Hub Substation

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