The Contract Package (MC-3) involves the construction of various civil works components, including the part of Head Race Tunnel (from Surge Shaft end), underground Surge Shaft, Butterfly Valve Chamber, Ferrule Erection Chamber, Pressure Shafts, Machine hall cavern, Transformer/GIS hall cavern, Downstream Surge Chamber, Tail Race Tunnel, and associated Hydro-Mechanical works. M/s Hindustan Construction Company Limited (HCC) was awarded the Contract on March 27, 2009 at a contract price of Nu. 6,880,617,815.00.

The works under those components included in MC-3 package are as follows:

1. Head Race Tunnel:
   • Status: 100% Completed
   • Purpose: Continuation from upstream of MC-2 package and ending at the Surge Shaft bottom.
   • Dimension: 1.6 km length × 10.0 m diameter
   • Type: Circular-shaped tunnel
   • 1 No.
2. Surge Shaft:
   • Status: 100% Completed
   • Purpose: To protect the penstock from sudden water pressure surges by absorbing and regulating water flow fluctuations
   • Dimension: 24.5 m (dia) X128.5m (L)
   • Type: D-shaped Adit tunnel 7.0m
   • 1 No.
3. Surge Shaft Gate & Dome:
   • Status: 100% Completed
   • Purpose: To control/block the flow of water into the pressure shaft during operation and maintenance.
   • Capacity: 90 Tons
   • Type: Vertical Lift Slide Type  Gates
   • 2 Nos.
4. Butterfly Valve Chamber:
   • Status: 100% Completed
   • Purpose: To erect & house the Butterfly Valves
   • Dimension: 80.0 m (L) x 12.7 m (W) x 21.85 m (H)
   • Type: D-shaped Tunnel
   • 2 Nos
5. Ferrule Erection Chamber:
   • Status: 100% Completed
   • Purpose: To facilitate the erection of Pressure Shafts Steel liner/ferrules.
   • Dimension: 99.0 m (L) x 12.0 m (W) x 14.5 m (H)
   • Type: D-shaped Tunnel
   • 1 No
6. Pressure Shafts & Penstock:
   • Status: 100% Completed
   • There are two main steel liner pressure shaft where each pressure shaft is trifurcated into 3 penstocks and connected to MIV at machine hall at Power House.
   • Purpose: To carry water at high pressure for running the machines.
   • Dimension: Dia. 6m, 5.75m, 4.7m  & 3.2m,
   • Type: Circular (Steel Lined)
   • 2 Nos
7. Main Access Tunnel (MAT):
   • Status: 100% Completed
   • Purpose: Constructed to create excess for the construction of PH and other components
   • Dimension: 720.0 m long & 8×9 m
   • Type: D-shaped Tunnel
8. Machine Hall Cavern:
   • Status: 100% Completed
   • Purpose: To house turbines & machines 
   • Dimension: 236.9 m (L) x 22.9 m (W) x 53.0 m (H).
   • 1 No.
   • Machine capacity : 200MW each (200×6=1200MW)
9. Transformer Hall & GIS Hall Cavern:
   • Status: 100% Completed
   • Purpose: To house 20 Nos. of GT, 1 No. stunt reactor etc. which shall be connected to GIS.
   • Dimension: 215.7 m (L) x 14.3 m (W) x 26.3 m (H).
   • Type: Cavern
10. Bus Duct Tunnels:
    • Status: 100% Completed
    • Purpose: For transferring the power generated to GT through GIB/bus bar of the 6-unit turbines
    • Dimension: 52.5 m (L) x 10.10 m (W) x 7.55 m (H).
    • Type: D-shaped Tunnel
    • 3 Nos
11. Draft Tube Tunnels:
    • Status: 100% Completed
    • Purpose: To release the water to DSSG/TRT after heating the turbines.
    • Dimension: 107.2 m (L) x 5.5 m dia.
    • Type: D-shaped Tunnel
    • 6 Draft Tube Tunnels
12. Downstream Surge Gallery (DSSG):
    • Status: 100% Completed
    • Purpose: To house six Nos. of draft Tube gates
    • Dimension: 150.0 m (L) x 11.5 m (W) x 45.4 m (H) Total length 556m (L).
    • Type: D-shaped Tunnel
    • 1 No
    • Has 7.5m cantilever slab at the deck level for erection of gates. Connected with Draft Tube Tunnels (DTT) of 107.2 m (L) x 5.5 m dia.
13. Draft Tube Gates:
    • Status: 100% Completed
    • Purpose: To isolate the turbine and draft tubes from water flow during maintenance and inspection.
    • Type: Fixed Wheel Slide Type
    • 6 Nos
    • Capacity: 45 Ton
14. Drainage Gallery:
    • Status: 100% Completed
    • Purpose: Around the periphery of PH and upstream of MH is constructed to cater all the seepage water
    • Dimension: 879.0m long and 5.0m
    • Type: D-shaped Tunnel
    • 1 No
15. Tail Race Tunnel (TRT):
    • Status: 100% Completed
    • Purpose: To release the water to the outfall that came out after heating the turbines.
    • Dimension: 10.0 m Dia. X 1.26 km Length
    • Type: Circular-shaped tunnels
    • 1 No
    • Connected with two branches (TRT1 and TRT2) from DSSG having length of 157m and 131 m respectively.
16. Cable Tunnel:
    • Status: 100% Completed
    • Purpose: Constructed to take the power from GIS to PHY through XLP Cables.
    • Dimension: 668.0 m (L) x 5.0 m (W) x 6.1 m (H)
    • Type: D-shaped Tunnel
    • 6 Draft Tube Tunnels
17. Pothead Yard (PHY):
    • Status: 100% Completed
    • Purpose: To connect underground power cables to overhead transmission lines.
    • Dimension: 197.0 m (L) x 39.0 m (W) 
    • Type: ICT Building & Substation
    • 1 No
    • PHY is constructed in open area nearby cable tunnel portal area.
18. TRT Gates:
    • Status: 100% Completed
    • Purpose: To control or stop the water flow in the tail race tunnel for maintenance, emergency shutdown or inspection.
    • Capacity : 60 tons each
    • Gate Type : Vertical Lift Fixed Wheel Completed in all respects.
    • 2 Nos
    • Outfall area for discharging water to river is completed in all aspects. 

Work Completion:

The construction of the major components in Contract Package MC-3 stand completed on 14.10.2023 and accordingly Maintenance Certificate is issued on 22.01.2025.