Tehri Dam Project — CP Systems

Mega Project

Tehri Dam — India's Tallest Dam

Multiple phases of critical work at Tehri HPP (1000 MW) and Tehri PSP — including river dredging of the Bhagirathi River, construction of a 47m baffle wall, HRT/TRT tunnel repair with epoxy mortar, micro piling, drilling & grouting, and epoxy treatment at intake structures.

Client
HCC / THDCIL

Location
Tehri, Uttarakhand

Dredged Volume
~2.5 Lakh Cum (Phase 1+2)

Baffle Wall
47m across Bhagirathi

Phase 1 Feb – Jul 2023

River Dredging at Tehri

River dredging across 640 Rm of the Bhagirathi River downstream of Tehri Dam spillway — executed during zero schedule of Tehri HPP. Water level varied 8-10m twice daily, with only 3-4 hours of working time per shutdown.

Dredging per daily zero schedule by THDCIL
~1 Lakh Cum material dredged and transported 14-15 Km
12 Excavators (210), 2 Excavators (300) with long boom
50-60 Dumpers for muck transportation

12 dewatering pumps (50HP each, 7000-8000 LPM)
Dedicated 30 Cum Batching Plant, 6 Transit Mixers
Boom Placer for underwater concreting
All resources deployed 24 Hrs in two shifts

River dredging operations

Water level at 604+ MTR

Excavation in variable water

Dredging March 2023

Heavy machinery deployment

Water level 603.75 MTR

Phase 1 Feb – Jul 2023

Baffle Wall & Micro Piling Construction

Construction of approx 47m long Baffle Wall across the Bhagirathi River between Spillway & TRT of Tehri HPP (1000MW). Underwater concrete pouring, micro piling in saturated riverbed conditions.

47m Baffle Wall across flowing Bhagirathi River
~2000 Cum RCC constructed in 4 months
1000mm dia Hume Pipe in Baffle Wall
Micro Piling (700m) in saturated foundation

Baffle Wall built in 5-10m segments
Underwater concreting via mobile Boom Placer
Drilling & grouting of anchors on both banks
~400 Rm micro piling completed in 1 month

Baffle Wall construction

Micro piling operations

Concreting in progress

Wall segment formation

Foundation reinforcement

Completed Phase 1 baffle wall

Phase 2 Jun – Jul 2024 (35-Day Shutdown)

River Dredging Phase 2

The second phase involved dredging 150,000 Cum from Chainage 260m to 660m and construction of Ramps (5m wide, 70m long) upstream & downstream of the Baffle Wall — all within a strict 35-day shutdown window.

1,50,000 Cum dredging in 35-day shutdown
Continuous ILO discharge — water never below EL 601.5m
12-day approach road construction through river
Encountered 12m depth area across full river width

20 additional dumpers mid-project for muck transport
Emergency concrete wall for exposed THDCIL building foundation
Rain interruptions during operations
Completed successfully within 35 days

Phase 2 dredging operations

Excavation in progress

River bed operations

Machinery at work

Dumper loading operations

Approach construction

Phase 2 Jun – Jul 2024

Ramp Construction & Micro Piling Phase 2

Construction of 70m long, 5m wide Ramps upstream & downstream along the Bhagirathi River. Micro Piling (850m) in foundation. All carried out during the 35-day shutdown with underwater concreting via Boom Placer.

70m long Ramps upstream & downstream
14,400 Cum concreting
~850m Micro Piling in Ramp foundation
Underwater concrete via Boom Placer

Ramps built in 5-10m segments due to seepage
Foundation never below EL 601m (target: EL 598-600m)
Shuttering fixed in standing water
Formwork buried in muck, required excavation to remove

Ramp construction

Concreting by Boom Placer

Underwater concrete pouring

HRT/TRT Tunnel Repair Campaign

Tunnel Repair by Drilling, Grouting & Epoxy at Tehri PSP

Repair of 8.5m diameter Head Race Tunnels (HRT #3 and #4) at Tehri PSP via surge shaft at 100m vertical depth — involving massive quantities of epoxy mortar, underwater repair, and custom engineering solutions.

HRT #3 Repair

23m length of 8.5m dia HRT repaired
~375 MT Epoxy Mortar consumed
Completed in 36 days (target: 45 days)
Access via Surge Shaft crane (100m vertical)
Material manually transported 700m through tunnel
100-125 workers deployed 24/7

HRT #4 Repair

32m length of 8.5m dia HRT repaired
~430 MT Epoxy Mortar consumed
Completed in 37 days (target: 45 days)
Custom electric mixers — 110kg batch in 5 mins
12mm dia shear connectors @ 300mm C/C
Special curved shuttering matching HRT profile

TRT/HRT repair work

Epoxy mortar in HRT #3

Material through trolley

HRT #4 plug breaking area

Foundation epoxy work

Tunnel repair operations

TRT tunnel preparations

TRT surface preparation

TRT epoxy application

Drilling & Grouting Tehri PSP

Drainage Gallery Upgrades

Specialized drilling and grouting works were performed throughout the Drainage Gallery networks at the Tehri PSP. This critical stabilization and seepage control measure was executed despite heavily restricted tunnel access and spatial constraints.

Drilling & Grouting Operations

Surge Shaft Repair T1, T2, T3, T4

Vertical Shaft (Morning Glory) Epoxy Treatment

Repair of the swirling device bottom area in all four tunnel surge shafts. Faced with continuous waterfalls dropping from 150-160m heights, a spectacular engineering feat was executed: a 25m tall scaffolding was built inside the 16m diameter shaft. Water was funneled away using completely customized GI sheets, enabling full epoxy treatment, mortar seals, and fiberglass cloth wrapping of the shaft walls over 4 stipulated months.