About Project

Project Details
Salient Features
Project Layout

Salient features of the Project:
The Project components are located in the East and North Sikkim district of the state of Sikkim with Dam at the Lingdoc Village and the Power House site at Dikchu. The project utilizes the fall of head in the River course, of about 350 meters between these two villages.

The main components of the project are:
35 m high concrete dam
Desilting chamber of size 130m(L) x 20m(W) x 12m(H)
4.6km long and 4m diameter head race tunnel terminating in a surge shaft
9m dia surge shaft
600m long, 3m dia pressure shaft
An underground power house having an installation of 3 Francis turbine
generating units of 32 MW each operating under a net head of 350m
1000m long tunnel and 100 m open channel and 4m diameter tail race tunnel

The First unit of the Project is scheduled to be commissioned in August 2013 and the third unit in Dec 2013.

HYDROLOGY
Catchment Area at Dam Site 240 km2
Design Flood 1100 m3 / sec
Probable Maximum Flood (PMF)

RESERVOIR
Full Reservoir Level (FRL) El 950.0 m
Max. Reservoir Level (MWL) El 952.0 m
Minimum Draw Down Level (MDDL) El 939.0 m
Gross storage up to FRL 0.52 M cum
Live Storage at FRL 0.33 M cum

DAM
Type Concrete Gravity dam
Top Elevation of Dam EL 955.0 m
Height of dam above riverbed level 35.0 m
Length of Dam 126 m
Riverbed level EL 920.0 m (avg)

SPILLWAY
Design flood 1100 m3 / sec (PMF)
Type Ogee shape
Crest level El 924 M
Maximum head over crest (w.r.t. FRL) 26.0 m
Type of gate Radial- sluice
Length of spillway 33 m
No of under sluices 3
Size of each radial gate 5m (W) x 8m (H)
Energy dissipation Trajectory bucket

DIVERSION TUNNEL
Number 1
Size 7.0 m
Length (approx) 350.0 m
Diversion Flood 345 m3/sec

TUNNEL INTAKE
Invert level EL 933.00 m
Size of each Gate 4 m x 4 m
Trash Rack Size 5 m x 6 m (Steel Trash Racks)
Design discharge 40 m3 / sec

DESILTING CHAMBER
Size 20 m (width), 11.5m (height)
Length 130m
Design Discharge 40 m3 / sec
Particle size to be removed 0.2 mm and above (90% efficiency)

HEADRACE TUNNEL
Number 1
Size 4 m dia,
Shape Horse Shoe shaped
Length 4.6 km (approx)
No. of Adits 2

SURGE SHAFT
Size & Type 9 m diameter, Simple
Vertical Shaft height 65 m
Maximum Surge Level El 971 m
Minimum Surge Level El 917 m

PRESSURE SHAFT & PENSTOCKS
Pressure Shaft
Diameter 3.0 m (Circular)
Number 1
Underground Pressure Shaft Length 600 m
Penstocks
Type & Number Circular, 3 Nos.
Diameter 1.6 m
Length 25 m

POWER HOUSE
Type Underground
Installed Capacity 96 MW
Number of units 3
Powerhouse cavern size (main) 63m x 12m x 36m
Type of turbine Vertical Axis Francis Turbine
Tail water level at outlet EL 580.0 m
C.L of Turbine EL 570.0m
Rated Head 350 m
Design Discharge 10.67 m3 / sec

TAILRACE
Size 4 m dia
Type D- shaped
Length 1000 m
Tail Water level at outlet EL 580.0 m

SWITCH YARD
Type, Size Open, 60 m x 30 m