About salient features of Mathillo Mailung Khola Jalvidhyut Aayojana
Mathillo Mailung Khola Jalvidhyut Aayojana (MMKJA) is run-of-river (RoR) project with installed capacity 14.3 MW, located in Uttargaya Rural Municipality ward no. 1 (previously Haku and Dadagaun VDC), Rasuwa District, Bagmati Province, Nepal. The Project is being developed by Mathillo Mailun Khola Jalvidhyut Ltd. with its head office located at Shankha Park, Dhumbarahi, ward no. 4 Kathmandu M. C., Nepal. The license boundaries of the project area extends from 28º 08’ 00” N to 28º 05’ 56” N, and 85º 11’ 00” E to 85º 13’ 00” E. The project diverts the design discharge from Mailung River with a watershed area of 72 km² at the proposed intake.
The proposed headworks of MMKJA comprises boulder lined weir, gated undersluice, side intake with two orifices, gravel trap, approach canal, and a two chambered settling basin. An inverted D-shaped headrace tunnel (HRT) immediately follows the settling basin. 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 a horizontal penstock pipe 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 an 11 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 (weir crest level) is located approximately 2049.0 m above mean sea level (amsl). The HRT alignment passes through right bank of the Mailung River which is approximately 1736 m up to the forebay. The powerhouse is proposed on the right bank of the Raman Kholsi just ahead of the confluence of Raman Kholsi and Mailung River in Uttargaya Rural Municipality ward no. 1. The powerhouse is located on a narrow terrain. The vertical shaft lies just 170 m upstream of the powerhouse. The entire project components such as headworks, HRT, forebay, penstock, vertical shaft, and powerhouse lie at right bank of Mailung River in Uttargaya Rural Municipality.
|
Project Location: |
||
|
Province |
Bagmati (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, Gyangsiling 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 flow 1.02 m3/s) |
|
|
Design Flow |
3.53 m3/s (40 % exceedance flow) |
|
|
Design Flood |
166 m3/s |
|
|
Diversion Weir: |
||
|
Type |
Boulder Lined |
|
|
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) |
|
|
Undersluice: |
||
|
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 m x 5.0 m 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 |
Inverted D |
|
|
Length |
1736 m |
|
|
Excavation Size (B x H) |
2.8 m x 2.8 m |
|
|
Longitudinal Slope |
1:1000 |
|
|
Support System |
Concrete Lining, Rock bolts 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 m x 1.00 m |
|
|
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 |
Rectangular (1.1 m X1.1 m ) |
|
|
(for spilled water passage) |
||
|
Support System |
Concrete Lining, Rockbolts and Shotcrete |
|
|
Connecting Tunnel (Spillway tunnel to Penstock tunnel) |
||
|
Shape |
Inverted D |
|
|
Length |
55.00 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 Tunnel: |
||
|
Horizontal tunnel 01 |
||
|
Shape |
Inverted D |
|
|
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 |
Inverted D |
|
|
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 |
Inverted D |
|
|
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 |
95.50% |
|
|
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 m |
|
|
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 |
|