Teesta - Ministry of Power

50 000 MW HYDROELECTRIC INITIATIVE 

Government of India 

Ministry of Power 

Central Electricity Authority 

320 MW TEESTA(I) H.E. PROJECT 

SIKKIM 

Preliminary Feasibility Report 

Consultant : 

April 2004 

National Hydroelectric Power Corporation Ltd. 

(A Government of India Enterprise)

CHAPTER 

I 

TABLE OF CONTENTS 

DESCRIPTION 

Executive Summary 


Teesta (I) HE Project (4 x 80 MW) 

PAGE NO. 

1-11 

II Background Information 12-19 

III Project Area 20-28 

IV Topographical & Geo-technical Aspects 29-37 

V Hydrology 38-66 

VI Conceptual Layout and Planning 67-82 

VII Power Potential Studies 83-115 

VIII Power Evacuation 116 

IX Environmental Aspects 117-138 

X Infrastructure 139-143 

XI Construction Planning & Schedule 144-151 

XII Cost Estimate 152-193 

XIII Economic Evaluation 194-201 

Plates 

Annexures

TITLE 

LIST OF PLATES 



PLATE 

No. 

Layout Plan of Schemes in Upper Part of Teesta Basin 1 

Cascade Development of Teesta River Basin 2 

Geological Plan of The Project Area 4.1 

Vicinity Map 6.1 

Layout Plan 6.2 

Dam-I Layout Plan 6.3 

Dam-II Layout Plan 6.4 

Power House Area Layout Plan 6.5 

Water Conductor System L-Section (Typical) 6.6 

Dam Upstream Elevation 6.7 

Dam: Spillway & Non-Overflow Cross Section 

(Typical) 

Typical Cross Section Of Constituents Of Water 

Conductor System & Diversion Tunnel 

Single Line Diagram 8.1 

6.8 

6.9

TITLE 

ANNEXURES 



No. 

Geology of the Area Around the Project- By G SI 4.1 

Technical Report on Seismic History and 

Seismicity- By IMD 

4.2 

Reply on CEA/CWC Comments on Draft PFR 6.1 

Letters from CEA/CWC



CHAPTER – I 

EXECUTIVE SUMMARY

1.0 INTRODUCTION 

CHAPTER-I 

EXECUTIVE SUMMARY 

1 



The Teesta (I) Hydroelectric Project located in North Sikkim district of Sikkim 

envisages utilization of the waters of the river Teesta and Zemu Chu for power 

generation on a run of river type development, harnessing a head of about 585m by 

constructing two dams, one at downstream of confluence of Lhonak Chu and Poke 

Chu tributaries of Zemu Chu (Dam-I) and other at downstream of the confluence of 

Chento Chu with Teesta river (Dam-II). 

The project with a proposed installation of 320 MW (4 x 80MW) would afford an 

annual energy generation of 1298.12 GWh in a 90% dependable year. The tariff from 

the project at present day cost would be Rs 1.66 per KWh (levellised). 

The diversion sites are located at Latitude 27º46’46” North, Longitude 88º30’00” East 

(Dam-I) and Latitude 27º48’19” North, Longitude 88º33’25” East (Dam-II). The 

Dam-I site is located just downstream of the confluence of Lhonak Chu and Poke Chu 

and Dam-II site on Teesta river downstream of confluence with Chento Chu. Presently 

Dam-I site is not approachable while the Dam-II site is approachable by 12km long 

road from Zema, which is about 129km from Gangtok the state capital of Sikkim. 

Zema is situated at a distance of 208km from nearest railhead at New Jal Paiguri and 

210km frm Bagdogra, the nearest airport. 

1.1 GENERAL PROJECT FEATURES 

The Teesta (I) HE Project envisages construction of : 

• Two concrete dams, both 40 m high, one across river Zema Chu (dam-I) and 

other at downstream of the confluence of Chento Chu and Teesta river (dam-

2 



II) to provide a total live storage of 2.82 mcum. with FRL at 3265m and 

MDDL at 3258m; 

• two intakes and two desilting chambers system of size 

200m(L)x8m(W)x12m(H) for each water conductor to remove silt particles of 

size 0.2mm and above; 

• two 4m diameter concrete lined 3.5km and 4.25km long head race tunnels 

terminating in a surge shaft; 

• a 75m high, 15m dia surge shaft; 

• 825m long, 2.5m dia two pressure shaft; 

• an underground power house having an installation of 4 Vertical Pelton turbine 

generating units of 80 MW each operating under a net head of 576.85m; and 

• a 1000m long, 5.0m diameter tailrace tunnel to carry the power house release 

back to the river; 

The power generated from the project would be evacuated through one number 

400KV double circuit lines to be connected at the pooling station which is assumed to 

come up near Teesta-I HE Project to feed power to the power grid. 

The salient features of the projects are as under: 

LOCATION 

SALIENT FEATURES 

State Sikkim 

District North Sikkim 

Location of Dam -I + 500 m D/S of confluence of Lohnak chu 

with Zemu chu on Zemu Chu 

Latitude & Longitude of Dam-I 27º46’46’’N & 88º30’00E 

Location of Dam-II + 700 m D/S of confluence of Chento chu 

with Teesta river on Teesta river 

Latitude & Longitude of Dam-II 27º48’19’’ & 88º33’25’’

3 



Location of Power House Just U/S of confluence of Zemu chu with 

Teesta 

Latitude & Longitude of Power House 27º45’50’’ & 88º32’30’’ 

Nearest Rail head New Jalpaiguri 

Nearest Airport Bagdogra 

HYDROLOGY 

Catchment area Dam -I 881 km 2 

Catchment area Dam-II 600 km 2 

Design Flood for Dam -I 1600 m 3 /sec 

Design Flood for Dam-II 1300 m 3 /sec 

DIVERSION TUNNELS 

Diameter & Shape (for both DT’s) 6 m, Horse-shoe shaped 

Length of DT for Dam-I 600 m 

Length of DT for Dam-II 300m 

Diversion Discharge(for both DT’s) ± 400 m 3 /sec 

Diversion Tunnel Gate 1 No. Vertical lift gate 

Size of Gate 6m × 8m 

COFFER DAMS (for both dams) 

Type Rockfill with central clay core. 

Maximum height of upstream coffer dam ± 15.0 m 

Maximum height of downstream coffer 

dam 

CONCRETE DAM-I 

± 8.0 m 

Type Concrete Gravity

Dam Top EL.3270 m 

River bed level at dam site EL.3230m 

Maximum Dam height (above deepest 

foundation level) 

4 

45 m 

Dam height (above River bed level) 40 m 

Length at dam top 350 m 

CONCRETE DAM-II 

Type Concrete Gravity 

Dam Top EL. 3270m 

River bed level at dam site EL.3230m 

Maximum Dam height (above deepest 

foundation level) 

60 m 

Dam height (above River bed level) 40 m 

Length at dam top 240 m 

SPILLWAY 

DAM-I 

Type Orifice Type 

No. of bays 5 

Crest level of spillway EL.3240 m 

Size of the openings 4m(w) X 6m(H) 

Design flood (PMF) 1600 m 3 /sec 

DAM-II 

Type Orifice Type 

No. of bays 4 

Crest level of spillway EL. 3240m 

Size of the openings 4.5m(w) X 6m(H) 

Design flood (PMF) 1300 m 3 /sec 


Teesta (I) HE Project (4 x 80 MW)

RESERVOIR 

DAM-I 

Full Reservoir Level (FRL) EL.3265 m 

Minimum draw down level (MDDL) EL.3260 m 

Area under submergence at FRL 43.75 Ha 

Gross Storage 9.26MCM 

Live Storage 1.78 MCM 

DAM-II 

Full Reservoir Level (FRL) EL. 3265m 

Minimum draw down level (MDDL) EL.3258m 

Area under submergence at FRL 19.57 Ha 

Gross Storage 4.00 MCM 

Live Storage 1.04 MCM 

POWER INTAKES (for both the dams) 

Number Two 

Invert level EL.3250 m 

Size of each Gate 4.5 m ×4.5 m 

Trash Rack 

5 



Steel Trash Racks with Raking Machine 

Design discharge +19.05 m 3 /sec in each intake 

DESILTING CHAMBERS 

(for both the dams) 

No., Type & size of desilting chamber 2 Nos., Dufour type chambers each 200 m 

long, 8 m wide, ht.12m 

Design Discharge in each chamber +19.05 m 3 /sec 

Particle size to be removed ≥ 0.2 mm (90% efficiency)

SILT FLUSHING TUNNELS 

(for both the dams) 

Size and Shape 2m X 3.0m, D-Shaped 

HEADRACE TUNNELS 

6 



Size & type (for both the tunnels) 4m Dia, Horse –shoe shaped, concrete 

lined 

Design discharge 31.76 m 3 /sec 

Length for HRT-I 3.5 Km 

Length for HRT-II 4.25 Km 

SURGE SHAFT 

Size & type 15 m diameter 

Vertical Shaft height ± 75 m 

PRESSURE SHAFT 

Number & Type Two ; Steel Lined, Inclined 

Diameter 2.5 m dia 

Length 825 m 

POWER HOUSE COMPLEX 

Type Under ground 

Tail water level at outlet 2675 m 

Turbine Axis Elevation 2677.82 m 

Type of Turbine Vertical Pelton 

Generating Capacity 4 X 80 MW 

Gross head 584.85 m 

Rated Net head 576.85 m 

Design Discharge 63.52 m 3 /sec

Power House Size 141 m X 22m X40 m 

TRT 

Diameter and type 5 m dia, Horse-shoe 

Length 1000m 

Tail Water level at outlet 2675 m 

SWITCH YARD 

Size 250M X180 M 

POWER GENERATION 

Installed Capacity 320 MW (4X80MW) 

Energy Generation in 90% dependable 

Year 

7 

1298.12MU 



COST ESTIMATES & FIANANCIAL ASPECTS ( Rs. Crores) 

Civil Works 788.45 

Electro Mechanical Works 301.03 

Sub Total ( Generation) 1089.48 at June,2003 Price Level 

Transmission works 1.40 

Total hard cost 1090.88 

Interest during Construction 115.71 

Grand Total 1206.59 

Tariff for first year per KWh 

a. with 12% free power 

b. without 12% free power 

Levellised Tariff per KWh 

a. with 12% free power 

b. without free power 

Rs. 2.05 

Rs. 1.80 

Rs. 1.66 

Rs. 1.46 

COSTRUCTION PERIOD 5 years

1.2 STUDIES/INVESTIGATIONS UNDERTAKEN 

• Study of topographic maps and remote sensing imageries 

8 



• Reconnaissance of area for identifying probable alternative sites of projects 

components. 

• Study of regional geotechnical features/ seimotectonic aspects. 

• Geological appraisal of proposed project components. 

• Water availability design flood studies based on available meteorological/ 

hydrological data. 

• Conceptual layout and project planning. 

• Power potential studies. 

• Study of biotic environment, socio-economic environment for prediction of 

environmental impacts of the projects. 

• Study of existing infrastructure. 

• Cost benefit and economic evaluation. 

1.3 RESULTS OF STUDIES AND INVESTIGATIONS 

1.3.1 Geology 

The preliminary geological survey of the locations of all the structures on the ground 

was carried out after site visits. The site-specific geological data were got collected 

and utilized in the design of various component of the project. The survey of the near 

by area was also carried out to co-relate the geology of the project area. 

1.3.2 Hydrology 

The Teesta river and Zema Chu drain a total catchment area of about 1481sq.km at the 

proposed dam sites. The water availability for the project has been considered on the 

basis of 10-daily discharge series at Lachen for the period from 1976-1997. The water 

availability at the dam-I and dam-II sites has been derived from the above data on the 

basis of catchment area proportion and applying an overall reduction factor of 0.46 

and 0.314 respectively. The computed inflow series works out has been utilized for

9 



Power Potential Studies. The design flood has been assessed as 1600 and 1300 cumecs 

for dam-I and dam-II sites respectively. 

1.3.3 Power Potential Studies 

The computed inflow series for 22 years viz Jan 1976 to Dec 97 has been considered 

in the assessment of a power benefits from the project. As per GOI notification for 

tariff the year 1976-77 corresponds to 90% dependable year. An installation of 

320MW comprising 4 generating units of 80MW has been proposed. The energy 

availability from the project in a 90%dependable and an average year has been 

summarized below: 

Annual Energy Generation 

Annual Energy Generation (GWh) 1298.12 

Annual Load Factor (%) 46.31 

Generation during Lean Flow Season 

Energy Output (GWh) 164.59 

Load Factor (%) 17.71 

The design energy for tariff at 95% availability in a 90% dependable year has been 

worked out at 1298.12 GWh. 

A pondage of 2.82 mcum has been provided in the diversion dams, which would 

enable the station to operate as peaking station. The pondage is equivalent to 3946.54 

MWh which sufficient to operate the station for 3.23 hours. 

1.3.4 Power Evacuation Aspects 

The power generated from the project would be evacuated through 400KV, double 

circuit lines to be connected at the pooling station which is assumed to come up near 

Teesta-I HE Project to feed power to the power grid. 

.

1.3.5 Environmental Aspects 

10 



The project is located in north district of Sikkim. The total land requirement for the 

construction of various components is about 257ha. Most of the land falls under the 

category of private land. Based on assessment of environmental impacts, management 

plans have to be formulated for Catchment Area Treatment, compensatory 

afforestation and other environmental issues. These issues would be addressed during 

the investigation for DPR. 

1.3.6 Estimates Of The Cost 

The project is estimated to cost Rs. 1206.59crores including IDC at June,2003 price 

levels. The preliminary cost estimate of the project has been prepared as per guidelines 

of CEA/CWC. The break down of the cost estimate (Rs. Crores) is given below: 

Civil works : 788.45 

Electro Mechanical Works : 301.03 

Sub Total (Generation) : 1089.48 

Transmission Works : 1.40 

Total (Hard Cost) : 1090.88 

Interest During Construction : 115.71 

Grand Total : 1206.59 

1.3.7 Financial Aspects 

As indicated above, the Teesta (I) HE project with an estimated cost of Rs. 1206.59 

crores (including IDC of Rs. 115.71crores) and design energy of 1298.12GWh in a 

90% dependable year is proposed to be completed in a period of 5 years. The tariff has 

been worked out considering a debt-equity ratio of 70:30, 16% return on equity, 

annual interest rate on loan at 10% and 12% of energy as free power to Home State 

available after losses. The tariff for the first year and levellised tariff has been worked 

out Rs. 2.05/KWh & Rs. 1.66/KWh respectively.

1.3.8 Conclusions 

11 



The Teesta (I) HE project involves simple civil works and could be completed in 5 

years. The project would afford a design energy of 1298.12 GWh in a 90% dependable 

year. The cost per MW installed work out Rs.3.40 crore. The Preliminary Feasibility 

Report indicates that the scheme merit consideration for taking up for Survey & 

Investigation and preparation of DPR.



CHAPTER – II 

BACKGROUND INFORMATION

2.1 GENERAL Information 

2.1.1 Introduction 

CHAPTER –II 

BACKGROUND INFORMATION 

12 



Sikkim, the Himalayan state has elected to join the Indian Union to become 22 nd state 

in 1975,. It is one of the most picturesque regions of Asia. The bowl like, mountain – 

girdled state in the eastern Himalayas bordered on the west by Nepal, on the north by 

Tibet, on the east by Bhutan and the south by Darjeeling district of the West Bengal, 

lies between 27 0 to 28 0 north latitude and 88 0 to 89 0 east longitudes. The Sikkim is the 

youngest and small hill state of India having an area of 7096 Sqkm. Sikkim is 

surrounded by important mountain ranges. The Chola range of mountains on its east 

forms the watershed between it and Bhutan on one side and Chumbi valley of Tibet on 

the other. The well-known Singalila ridge is of the great Himalayas peaks. 

Sikkim is divided into four districts. The most populated area is the Eastern district, 

which contains the capital town Gangtok followed by Southern and Western districts. 

The northern district is sparsely populated because of its inhospitable climate and 

steep ridges. Lying along the slopes of Himalayas between Tibet and plain of India, 

cut off from the rest of the world by mighty mountains, Sikkim’s scenic beauty has no 

parallel in the East, Sikkim’s historic past, mystic religion, sublime monasteries and 

age old rituals have an attraction hardly to be found anywhere else in the world. 

Sikkim is mountainous terrain with cliffs and valleys. Dominating both legend and 

landscape is the mighty massif of Khangchendzonga known to the outside world as 

Kanchenjunga, it is the third highest peak in the world, towering at 8550 meters. 

Sikkim is drained by number of Perennial Rivers. However, the two main river 

systems are Teesta and Rangit. The other entire stream eventually joins one or the

13 



other. Rangit also joins the Teesta just near the broader between Sikkim and West 

Bengal at Melli. Besides the river, there are number of lakes and hot springs which 

add to the beauty of the region. The important hot springs are Phut sachu, Raeong 

sachu, Yumthang and Momay. 

2.1.2 Topography 

The total geographical area of Sikkim State is about 7300 sq. km. The maximum 

horizontal length from north to south is about 112 Km. whereas the maximum width 

from east to west is 90 Km. The Tibetan Plateau on the north, Nathula and other 

passes on the north east, Bhutan on the south east, Darjeeling district of West Bengal 

on the south and Singalila range of Nepal from the boundaries of this picturesque 

Himalayan State. It is a hill state having no plain area. The altitude above mean sea 

level varies from 213m in the south to over 8500m in the northwest. The 

Khangchedzonga, the third highest peak in the world at an elevation of about 8550m 

adorns the state with its beautiful range covered with shining snow. Gangtok, the 

capital is about 1677m above mean sea level. The northern part of the state is cut into 

deep escarpments. The northern part is not populated except in Lachung and Lachen 

valleys. Southern Sikkim is, however, more open and fairly well cultivated. 

2.1.3 Rivers 

The river Teesta is one of the main Himalayan Rivers, which originates in the glaciers 

of Sikkim at an elevation of over 8500m above mean sea level. River rises in 

mountainous terrain and is formed mainly by the union of two hill streams Lachen 

Chu and Lachung Chu at Chungthang in North Sikkim. After the confluence of 

Lachen Chu and Lachung chu at Chungthang, the river gradually increases in width 

and takes a wide flowing down to Singhik, dropping in elevation from 1550m to 

750m. At Singhik, the river receives one of the its major tributaries, the Talung chug 

on its right. Talung Chu originates from the Talung glaciers, which are the part of the 

Khangchendzonga range. From Singhik, the rivers flow towards Dikchu in a very deep

14 



valley and drops from 750mto 550m. From Dikchu the river flows in a big curve again 

down to the Singtam with a drop of about 200m. The Rongnichu, which drains the 

Changu lake area joins Teesta from left at Singtam and the river receives Rangpo Chu 

at Rangpo. After Rangpo, Teesta start widening rapidly and is joined by the great 

Rangit at Melli bazar on Sikkim – West Bengal border. 

2.1.4 Communication 

By Air 

Bagdogra is the nearest airport of Sikkim. There are regular scheduled flights operated 

by the Indian airlines and other private airlines between Calcutta, the capital of West 

Bengal and Bagdogra and also between New Delhi and Bagdogra. Jeep & taxis are 

available outsides Bagdogra airport for Gangtok. Gangtok is 124 kms from Bagdogra 

and the journey takes about 4 hours by jeep and 5 hours by bus. 

By Rail /Road 

The two closest railway stations to Gangtok are Siliguri junction, (Meter Gauge) 

which is 114km away and New Jailpaiguri (Broad Gauge), which is 125km away. A 

number of trains are available for Calcutta, Delhi, Guwhati and other important cities 

of India. Besides jeep taxis, Sikkim National Transport and other private buses ply 

regularly between Sikkim and Siliguri. 

2.1.5 Project 

2.1.5.1 Background 

In order to exploit vast hydro potential in the country and to achieve the ideal hydro 

thermal mix of 40:60, the Honourable Prime Minister of India had launched a hydro- 

electric initiative on 24th May 2003 to develop 50,000MW hydro power potential in 

the country. Accordingly, based on the results of the preliminary ranking studies of 

Central Electricity Authority, 162 hydroelectric power schemes with estimated 

installed capacity of 50,560MW were selected in 16 states for preparation of Pre

15 



Feasibility Reports. The work of preparation of PFR’s was entrusted by Ministry of 

Power under overall coordination of CEA to NHPC Ltd, SJVN Ltd, NEEPCO, 

WAPCOS, KPCL, HPSEB and UJVN Ltd as consultancy work. NHPC was entrusted 

a total number of 43 schemes of 21345 MW comprising of 7 schemes in Indus-Jhelam 

Basin J&K, 25 schemes in Dihang-Dibang-Subansiri Basins Arunachal Pradesh, 1 

scheme in Narmada Basin Madhya Pradesh and 10 schemes in Teesta Basin Sikkim. 

The Teesta-I is one of the scheme for PFR. 

2.1.5.2 About The Project 

The project is located on Teesta and Zemu rivers in north of Sikkim. The project 

involves construction of concrete dam-I of 40 m high on d/s of confluence of Poke 

Chu and Lhonak Chu near the place called Jedang and dam-II of 60m high d/s of the 

confluence of Chento Chu and Teesta river near a place called Shacham, two headrace 

tunnels HRT-I (3.5 Km) and HRT-II (4.25km) length and an underground powerhouse 

with an installed capacity of 320 MW u/s of confluence of Zema Chu and Teesta-I 

near the place called Zema. The project shall generate 1298.12 MU of energy in a 90% 

dependable year. The Dam-I is connected by a hilly footpath of about 5.0 Km and 

Dam-II is about 12.0 Km by road from Zema.The Zema is about 4.0 Km from Lachen, 

the nearest village in the area. The zema is well connected to Gangtok by 129 long 

road and to Singtam (NH-31A) by 118.0 Km long road. The Lachen is a small village 

having the status of block. Lachen is having small market, post office, telephone 

facilities, primary health centers. Mangan, the head quarter of North District, is 65 km 

from Lachen . 

2.2 POWER SCENARIO AND EXISTING INSTALLATIONS 

2.2.1 Power System In India 

The Power System in India has grown from small, isolated stations, serving limited 

consumers in and around large cities, into large regional Power Grids. The

16 



generating capacity installed in the country has already grown to 107903.53 MW by 

March 2003. 

For the purpose of system planning and operation the country has been divided into 

following five geopolitical regions: Northern, Western, Southern, Eastern and North- 

Eastern regional power grids and the transmission system are being progressively 

inter-connected for efficient operation of these five regional grids. 

The objective of the system development is to evolve self-sufficient regional grid 

catering to the individual regional power demands. It is also aimed at achieving the 

maximum benefits from integrated operation, through a proper mix of thermal and 

hydro generation and ultimately to tie the five regional grids together to form a strong 

National Power Grid, providing even greater reliability. 

The power generated at Teesta I HEP (4 X 80MW) shall be partially absorbed in 

North Sikkim and excess power shall be evacuated to national grid. 

2.2.2 Power Position in East Sikkim Region 

The total installed capacity in Eastern Region is 16696.68 MW. Out of this only 

2459.51 MW is hydel installation. Thus the Hydro-thermal mix is 15:85, which is 

well below the national average of 25:75 and desirable ratio of 40:60. 

The power supply position for Eastern region during 10 th and 11 th Five Year Plans is 

summarised in Table2.1. The power and energy availability and requirements during 

and after 10 th Plan period in the Eastern Region is shown in Tables as projected in the 

16 th Electric Power Survey, published by CEA. 

Even considering the coordinated operation of existing hydro and thermal stations, as 

well as benefits from ongoing projects and also from the schemes cleared by CEA, 

the Eastern region is expected to face peak power and energy deficits during most of 

the 10 th five Year Plan. The power situation in the region is dynamic and it is

17 



expected that the power generated from this project shall be cheap and helpful to the 

region as compared to thermal and other expensive power in the region. 

2.2.3 Existing Power Installations In Sikkim 

First time, a micro hydel station was established in Sikkim on the bank of Ranikhola at 

Lower Sichey Busty with an installed capacity of 10 KW on 27 th May 1927for the 

needs of the members of the Royal family and Gangtok. Later, Lower Lagyap Hydel 

Project with an installed capacity was constructed by Govt. of sikkim and this was a 

big boom. Presently the following power stations are under operation in Sikkim. 

Sl. 

No. 

Hydel Schemes Year of 

Completion 

Installed 

Capacities 

(MW) 

Firm 

Capacity 

(MW) 

1 2 3 4 5 

1 Jali Power House 1966 2.10 1.20 

2 Rothak Micro Hydel 1971-72 0.20 0.10 

3 Rimbi Micro Hydel, Stage-I 1970-71 0.60 0.30 

4 Lower Lagyap HEP 1979-80 12.00 5.50 

5 Lachen Micro Hydel 1989-90 0.10 0.05 

6 Rimbi Stage-II 1989-90 1.00 0.50 

7 Rongnichu Micro Hydel-II 1988-89 2.50 1.20 

8 Lachung Micro Hydel 1991-92 0.20 0.10 

9 Mayongchu 1993-94 4.00 2.00 

10 Upper Rongnichu HEP 1994-95 8.00 4.00 

11 Kalej Khola 1995-96 2.00 1.00 

12 Rangit Hydel Project 1999-00 60.00 20.00

18 



13 Robom Micro Hydel 2003-04 3.0 1.00 

I - Total Hydel Power 95.70 36.95 

II - Total Diesel Power 2.70 2.70 

Total Generation Capacity 98.40 39.65 

2.2.4 Load Demand & Power Position of Eastern Grid 

Table-2-1 shows the power supply position of Eastern grid up to 2009-10. 

2.3 NECESSITY OF THE PROJECT AND RELATED ASPECTS 

The need for Teesta I H.E. Project has been considered in the context of increasing 

demand of power in the eastern region. It has been assumed that eastern region will 

have energy requirements at the rate 10% per annum rise of each year. This is a run of 

the river scheme with little pondage in Teesta basin in North Sikkim District, Sikkim. It 

will generate 1298.12 MU in 90% dependable year (1976-77) with 95% machine 

availability. 

The power generated at Teesta I HEP (4 X 80MW) shall be partially absorbed in North 

Sikkim and excess power shall be evacuated to national grid.

Table 2.1 

POWER SUPPLY POSITION OF EASTERN REGION 

WITHOUT TEESTA (I) HEP, (320 MW) 

10th Plan 11th Plan 

19 



Eastern Region 2002-03 2003-04 2004-05 2005-06 2006-07 2007-08 2008-09 2009-10 2010-11 2011-12 

1 2 3 4 5 6 7 8 9 10 

Installed Capacity MW 16697 17197 18327 20077 21237 22369 23269 24769 25429 26749 

Peak availability MW 7676 7906 8425 9230 9763 10284 10697 11387 11690 12297 

Peak requirement MW 8076 8527 9002 9505 10035 10586 11167 11780 12427 13109 

Peak Surplus(Deficit) MW -400 -621 -577 -275 -272 -302 -470 -393 -737 -812 

Peak Surplus(Deficit) % -4.95% -7.28% -6.41% -2.89% -2.71% -2.86% -4.21% -3.34% -5.93% -6.19% 

Energy availability MU 50260 51765 55167 60434 63926 67334 70043 74558 76545 80518 

Energy requirement MU 51653 54484 57469 60619 63941 67400 71046 74890 78941 83212 

Energy Surplus (Deficit) MU -1393 -2718 -2303 -184 -14 -66 -1003 -331 -2396 -2694 

Energy Surplus (Deficit) % -2.70% -4.99% -4.01% -0.30% -0.02% -0.10% -1.41% -0.44% -3.04% -3.24% 

1. All the data for the year 2002-2003 has been taken from the website www.cea.nic.in. 

2. Energy availability for the year 2002-2003 onwards have been estimated on the basis of ratio of Energy availability to Installed 

capacity for the year 2002-2003. 

3. Peak availability for the year 2002-2003 onwards have been estimated on the basis of ratio of Peak availability to installed 

capacity for the year 2002-2003. 

4. Energy requirement & peak requirement for the year 2002-2003 onwards is based on the annual increments given at page -117 & 

118 of "Sixteenth Electric Power Survey Of India". 

5. Micro/mini projects have not been considered for the study. 

Note:- This is a statistical analysis based on various publications mentioned above and are meant for study and planning 

purposes.



CHAPTER – III 

PROJECT AREA

CHAPTER –III 

PROJECT AREA 

20 



3.1 DESCRIPTION OF PROJECT INCLUDING RIVER SYSTEM 

Teesta (I) HE Project is situated in north district of Sikkim on the rivers Zema Chu 

and Teesta river. The project envisages construction of two concrete dams each 45m 

high, dam-I is at d/s of confluence of Poke Chu and Lhonak Chu near the place Jedang 

and dam-II at downstream of confluence of Teesta River with Chento Chu near place 

Shacham and an under ground powerhouse near the place Zema. The rivers water shall 

be diverted through two diversion tunnels of 600 m and 300 lengths and 6.0m dia each 

for construction of dams. Four numbers of desilting chambers of size 200m x 8m x 

12m, two for Dam-I and two for dam-II shall be constructed to separate the silt 

particles of 0.2mm size and above from the water. Two headrace tunnels of size 4.0m 

diameter and length 3.5km and 4.25km shall carry 31.76cumec of water each to the 

powerhouse respectively terminating into a semi underground surge shaft of 15 m dia 

and 75 m deep shall be constructed along with two circular inclined pressure shaft of 

2.5m dia 825m long each bifurcating to feed 4 units of vertical Pelton Wheel turbine. 

An under ground power house of size 141m x 22m x 40m shall houses four generating 

units. A 5m diameter and 1000 m long tailrace tunnel of shall discharge the water 

back into the river. A switchyard 0f 250 m x 180m size shall also be constructed. The 

powerhouse shall have installed capacity of 4units of 80MW each to generate 1298.12 

MU of energy in a 90% dependable year. 

The Zema Chu is one of the tributary of the Teesta river originating in the glaciers of 

north Sikkim at an elevation of about 5200 m above mean sea level. The tributaries of 

the Teesta River u/s of Zema Chu are Lasha Chu, Kalep Chu, Gyamthang Chu, 

Burum Chu, and d/s are Gey Chu, Trum Chu Rabom Chu, Lachung Chu. Further, the 

teesta is joined by OngChu, Chakung Chu, Ri Chu ,Rahi Chu, Tolong Chu, and

21 



Dikchu. In the downstream the Rongni Chu joins Teesta River at Singtam, Rangpo 

Chu at Rangpo and Rangit at Melli. 

3.2 SOCIO-ECONOMIC AND OTHER ASPECTS 

3.2.1 Demographic Features 

Sikkim is a multi-ethnic State. Broadly, the population can be divided into tribal and 

non-tribal groups. Lepchas, Bhutias, Sherpas are categorized as Scheduled Tribes. The 

Lepchas are the original inhabitants of the State. Compared to other ethnic groups, the 

Lepchas still maintain many of their traditional ways. The Bhutias comprise, the 

Sikkimese Bhutia and Bhutia from Bhutan and Tibet. The Sherpas are a marginal 

ethnic group in the State. Over 80% population consists of Nepalese. The people from 

the plain, mostly involved in trade and services, represent a marginal group. As per the 

2001 Census of India, the total population of the State is 540,493. The overall density 

of population in the State is 57 per sq km. East district is the most populated whereas 

that of the North District is only 7 per sq km and is the least populated. Sex ratio 

(females per thousand male) in 1981 was 835, whereas it had improved in 1991 to 878 

and in 2001 has shown a declining trend with a value of 875. There are only eight 

urban towns and urban population is 9.10% of total population. Literacy rate was 

56.94% (19th position) in 1991 and has increased to 70.65% in 2001. The rural 

literacy rate in 2001 is 68.59% whereas the urban literacy rate is 85.80%. 

The economy of Sikkim is mainly based on agricultural and animal husbandry. 

Approximately 11% of the total geographical area is under agriculture. The work force 

participation rate as per 1991 census is 40.44%. The female participation rate in 

Sikkim is also much higher than the national average. This is an important aspect of 

the hill economy, as productivity is low and hence all the able-bodied people are 

employed in agriculture and other activities. Cultivators account for the greater 

majority of the people in the State. Animal husbandry is an integral part of the house 

holds economy of the region. There are certain household industries also which

22 



substantially adds to household incomes. The past one and half decade has witnessed a 

tremendous upward swing in various development programme giving a new thrust to 

the Sikkim economy. This process has increased wage employment opportunities. 

There is very little human habitation in the vicinity of the proposed project sites. 

Though there is no village around the proposed Dam-I, but small hamlets are present 

around proposed Dam-II. These villages include Thangu, Bamchho, Kalep, Yathang, 

Samdong, Talam, Shacham, Thombu, Yunga and Zema, which fall within 7-10km 

radius of the project area. The human population as per the 1991 census up to different 

aerial distances from the project is given below. 

Up to 2 km Up to 2-5 km Up to 5-10 km 

Population Nil Nil 1640 

Households Nil Nil 488 

3.2.2 Ethnographic details (Details of the tribals in the area) 

In Sikkim various communities with their own customs, religion and 

culture intermingle freely to constitute a homogeneous blend. The predominant 

communities are the Lepchas, Bhutias and Nepalese. Many people from the plains 

have also settled, especially in the urban areas and they are almost always engaged in 

business or Government services. A small part of the population consists of migrant 

labourers from Bihar, West Bengal, Eastern UP and Nepal. 

3.2.3 Religion 

Hinduism and Buddhism are the two main religions prevalent in Sikkim. Hindus and 

Buddhists constitute 99 percent of the population; Christians, Muslims, Jains and 

Sikhs together are less than one per cent.

3.2.4 Health & Education 

23 



There are 4 district hospitals, Gyalshing, Namchi, Singtam & Mangan and one Central 

Referral Hospital at Gangtok, besides 25 Primary health centers, 150 Primary health 

sub-centres, 9 Veterinary hospitals and 25 Veterinary dispensaries. There is a blood 

bank at Gangtok. There are 1234 doctors. Small pox and Kalazor have been eliminated 

and many schemes for the provision of safe drinking water to villages and bazaars 

have been implemented. Sikkim has 700 Pre-nursery schools, 531Primary schools, 

122 Middle schools, 64 Secondary schools, 28 Higher secondary schools and 2 Public 

schools. There is a Training Institute for primary teachers, a Law college, a B.Ed 

college, 2 Degree colleges, a Industrial Training Institution, a Medical and an 

Engineering college. 

3.2.5 Trade & Industry 

Sikkim has a State Industrial Development Investment Corporation, which is 

encouraging establishment of industrial units in Sikkim. The Industrial Training 

Institute located at Rangpo is providing necessary expertise to the younger people for 

self-independence in the trade and the know-how. Sikkim has one distillery, one 

tannery and other ancillary units. Rangpo area has been declared as an industrial Zone. 

Two Breweries one is located at Melli, South Sikkim and other at Rangpo in East 

Sikkim. There is also a fruit preservation factory at Singtam. The Sikkim Mining 

Corporation mines copper, zinc, lead etc. The Sikkim Time Corporation a watch- 

manufacturing factory is located at Gangtok, which is producing one of the latest 

watches in India. There is a jewel factory located at Gangtok. Besides the above a 

good number of entrepreneurs have recently proposed to set up new factories. Some of 

the units are manufacturing leather goods, safety matches, local crafts, carpet weaving, 

handmade paper, woodcarving and similar works. The Sikkim State Tea Board has 

also been established for quality tea production.

3.2.6 Natural Resources 

24 



Sikkim is gifted with abundant natural resources. The resources can be grouped into a 

biotic & biotic both of which can be renewable and non-renewable. Biotic resources 

include agricultural crops, forests etc. The entire Himalayan region is endowed with 

natural flora and fauna and is a natural paradise for nature lovers, conservationists, 

botanists, zoolists and environmentalists. There are 4500 species of flowering plants, 

300 species of primulas, 20 species of bamboos etc., 45 species of rhododendrons and 

around 450 species of orchids. 

The State is very rich in fauna also. There are 144 species of mammals, 500-600 

species of birds, over 400 species of butterflies and moths and many species of reptiles 

are available. Sikkim is rich in medicinal plants/herbs and also important shrubs are 

found in low and high altitude areas. The State is endowed with water resources, 

tourism, hydroelectric potential etc. Under economic geology minerals like copper, 

iron, lime, dolomite, limestone, coal, quartzite, silicate & graphite are available in the 

state. As per the available data around 60% of total cardamom production in India is 

from Sikkim. There is a vast potential for hydroelectric power generation. Tourism 

development deserves considerable attention to add to the economy of the region. 

3.2.7 Hydropower Potential 

The Teesta and Rangit are the two main rivers of Sikkim where considerable hydro 

potential is available. Sikkim have developed 95.7 MW of hydropower potential so far 

by constructing mini & micro hydel projects and about 600 MW hydel potential is 

under development in different stages. The details of hydropower potential identified 

is as under: 

Teesta Basin : According to the preliminary reconnaissance survey, the river could be 

harnessed under a cascade development for hydropower generation is six stages as 

under :

i) Teesta Stage-I 

25 



It is proposed to divert the water of Teesta river d/s of its confluence with Chento chu 

near Shacham and water of Zema Chu d/s of confluence Lhonak chu and Poke chu by 

constructing diversion structures at EL ± 3230 and interconnecting tunnels discharging 

the Tail water at an EL ± 2775 near the place Zema. The scheme will have installed 

capacity of 320 MW. 

ii) Teesta Stage-II 

Under this scheme, a diversion dam of 83 m high is proposed near Bonsoi to divert the 

tail water of Teesta Stage-I and the power house at Chungthang. The scheme shall 

generate 330 MW. 

iii) Teesta Stage-III 

The schemes involve construction of Teesta River and Lachung chu near Chungthang 

and a Power house near Singhik. The scheme shall have the installed capacity of 1200 

MW. 

iv) Teesta Stage-IV 

A diversion dam is proposed just d/s of confluence of Teesta and Tolung chu near the 

place called Sanklan and power house near the village Dikchu. The scheme shall have 

installed capacity of 495 MW. 

v) Teesta Stage-V 

A diversion dam has been proposed d/s of confluence of Dikchu chu and Teesta river 

and a power house near the village Sherwani. The scheme shall have installed capacity 

of 510 MW. The project is under construction by NHPC in central sector. 

vi)Teesta Stage-VI 

Power Potential of Rangit Basin It envisages construction of a 76 m high concrete dam 

near Khanitar d/s of the confluence of the Teesta and Rongni chu in East Sikkim and 

the power house near the village Namthang/Tarkhola in South Sikkim with installed 

capacity of 360 MW.

Rangit Basin 

26 



The hydropower development of Rangit river was identified in four stages as under : 

i) Rangit HE Project Stage –I 

The Rathong chu, a major perennial tributary of Rangit river has a very steep bad slop. 

The river takes a big loop near Yoksum. It is proposed to divert the water of Rathong 

chu at an elevation of about 2300 m U/S of Yoksum to elevation of 100 m near village 

Thingtom. The scheme shall generate 47 MW of power at 60 % load factor. 

ii) Rangit HE Project Stage-II 

It is proposed to divert the water of Rimbhi chu near Sigglitem and allow the water to 

drop through 425 m near Lingchum on Kalet chu to generate 10 MW of power at 60% 

load factor. 

iii) Rangit HE Project Stage –III 

A dam has been constructed just d/s of confluence of Rathong chu and Rangit river 

and a power house near the village Mongbru. The installed capacity of the scheme is 

60 MW. The project has been commissioned by NHPC in the year 1999 and is in 

operation. 

iv) Rangit HE Project Stage-IV 

The scheme shall utilize a drop of 110 m from an elevation of 440 m to 355 m in 

Reshi loop. The scheme shall generate 18 MW of power at 60 % load factor. 

Schemes For PFR in Teesta Basin 

The Cenrtral Elecrtricity authority entrusted 10 schemes with total installed capacity 

of 1680 MW for preparation of prefeasibility reports as per details given below: 

Sl. 

No. 

Name of 

Scheme 

Installed 

Capacity 

Name of 

River 

District 

1. Dikchu 105 MW Bakchachu/Dikchu chu East 

2. Rongni 195 MW Rongni chu East 

3. Namlum 160 MW Rangit South

27 



4. Panan 200 MW Tolung chu North 

5. Lingza 160 MW Ringpi North 

6. Rangyong 141 MW Rangyong/ Umramchu North 

7. Ringpi 70 MW Ringpi North 

8. Rukel 33 MW Rukel/Rangyong North 

9. Jedang 185 MW Jhonak chu North 

10. Teesta Stage-I 320 MW Teesta & Zemu chu North 

Subsequently the Jedang scheme was replaced by Lachen scheme (210MW) and 

Namlum scheme by Talem scheme (75MW). 

OTHER SCHEMES IDENTIFIED BY CEA AND SIKKIM 

The CEA in the preliminary ranking studies and Sikkim in the preliminary studies 

identified the fallowing schemes: 

Sl. 

No. 

Name of Scheme Installed 

Capacity 

1. KalepHE Project 40 MW Teesta 

2. Talem HE Scheme 65 MW Teesta 

Name of River 

3. Serum HE Scheme 50 MW Lachung Chu 

4. Lachung HE Scheme 30 MW Lachung Chu/Sebokong Chu 

5. Chhota Pathing/Rolep 55 MW Rangpo Chu 

6. Chuzachen 13 MW Rangpo Chu 

7. Suntalitar HE Scheme 25 MW Rangpo Chu 

8. Mana 37 MW Rangit 

9. Gompa 46 MW Rangit

10. Rammam Stage-I 70 MW Rammam 

11. Rammam Stage-II 85 MW Rammam 

12. Rammam Stage-III 100 MW Rammam 

13 Chakhung Chu hydel 30 MW Chakhung Chu 

28 



In addition to above schemes, the Govt. of Sikkim have identified about 40 

mini/micro/small schemes for hydropower development.



CHAPTER – IV 

TOPOGRAPHICAL & 

GEO-TECHNICAL ASPECTS


CHAPTER-IV 

TOPOGRAPHIC AND GEOTECHNICAL ASPECTS 

29 



Central Electricity Authority as a part of its exercise of tapping the balance 

hydropower potential of various rivers and their tributaries, proposes construction of 

many projects in various parts of the country. As a sequel to this, few projects have 

been identified under river Teesta and its tributaries, in Sikkim. The project Teesta 

Stage-I on river Teesta is apart of this exercise. The project envisages construction of a 

dam at elevation 3230m on river Teesta to tap the potential of Teesta river, a water 

conductor system in the right bank of the river and a powerhouse near the confluence 

of river Teesta and Zemu Chhu. This power potential is proposed to be augmented by 

constructing a diversion across Zemu Chhu at elevation 3230m, a water conductor 

system in the left bank of Zemu Chhu culminating into the power house proposed near 

the confluence of Zemu Chhu and Teesta river. From the discussion between Chief 

Engineer (Civil), Teesta-V project and officers of CEA, it was found that the proposed 

dam across river Teesta shall be located below the confluence of river Teesta and 

Chento Chhu. In order to have an appraisal of the envisaged scheme, a visit to this 

area was made in the month of Nov ’03 and Feb ’04. However, during the visit of 

November ‘03, the first snowfall was occurring in upper areas while during February 

’04 the area was under heavy snow cover. The part of the project on Zemu Chhu 

couldnot be visited, as the same was inaccessible. 

As per the MOU between NHPC and CEA, the geological reports of GSI would form 

the main input data. The report however, this report is yet to be received and as such 

the regional geological details and other geological inputs shall be modified 

subsequent to the receipt of this report. The present appraisal is based on the study of 

topographic sheet no. 78 A/9 and the reconnoitre traverse undertaken.

30 



4.2 REGIONAL TOPOGRAPHIC AND GEOTECHNICAL FEATURES 

This regional geological setup is based on literature studies and geological report of 

GSI for the Scheme. River Teesta in Sikkim is a major river originating from Zemu 

glaciers and generally flows in north-south direction, at a steeper gradient. The river is 

joined by several tributaries major amongst them being Yumthang Chu, Zemu Chu, 

Talung Chu, Dik Chu , Rangpo Chu and Rangit chu, apart from others join the river. 

The river valleys in this region are u-shaped while, as the tributaries had developed 

deep gorges, which are bound by steep slopes. A thick vegetal cover occupies the hill 

slopes. A study of available literature was undertaken to have an overview of the 

regional geology of this area. The Eastern Himalaya covers the Sikkim-Darjeeling- 

Bhutan and Arunachal Pradesh sectors, extending from the eastern Nepal to western 

Burma. The higher Himalaya is a zone of crystalline rocks dividing two distinct 

lithofacies association in the south and the north. It is designated as the Axial belt. The 

northern zone comprising the Tethyan Palaeo-Mesozoic sedimentary sequence forms 

the Trans-Axial belt. To the south of the Axial belt occurs the Inner belt, comprising 

thrust sheets of Proterozoic-Upper Palaeozoic formations, while the foothill belt is 

represented by para-autochthonous Siwaliks. This scheme is valid for the entire 

Eastern Himalaya, upto the Lohit District of Arunachal Pradesh, where the geological 

picture does not conform to this general scheme. The stratigraphic sequence provided 

by GSI report on Ringpi Hydroelectric Scheme has been brought out hereunder for the 

purpose of regional geological set-up of the area. According to this report the region 

from south to north is occupied by Gondwana, Daling, Chungthang and Central 

Crystalline Gneissic group of rocks.

Group Lithology 

31 



Gondwana Grits, pebble cum boulder beds and carbonaceous shale with 

occasional coal seams, pegmatite, quartzite (Tourmaline bearing) 

Daling • Interbedded quartzite and chlorite sericite phyllite / schist 

• Lingza Granite 

• Quartzite/ Biotite schist 

Chungthang • Interbedded quartzite and garnetiferous quartz biotite schist. 

Central 

Crystalline 

Gneissic 

Complex 

• Calc-silicate rock/marble. 

• Garnet-Kyanite-sillimanite-biotite-quartz-schist. 

Banded gneiss with augen gneiss and quartz-biotite gneiss. 

Augen gneiss. 

Rock types belonging to Chungthang Series and Kanchenjunga gneisses of Central 

Crystallines of Higher Himalaya occupy the region. Rock Type of Chungthang series 

comprise qurtz biotite schist, calc silicate rocks and graphitic schists. The quartzites 

are hard and compact and at places have intrusions of amphibolites and pegmatite 

veins. The Chungthang series is followed further north by augen gneisses and streaky 

gneisses of Kanchanjunga group. These are exposed towards higher altitudes. The 

gneisses are hard, compact and well jointed and at places intruded by tourmaline 

granites and pegmatites. The rock types are represented mainly by high-grade 

metamorphics. The contact between the two is reported to be thrusted. Due to complex 

folding gneissic and schistose bands are intricately folded with metasedimentary units. 

In general the rock formations dip easterly. 

For regional geological setup of area GSI report for this scheme may be reffered, 

which is placed as annexure 4.1.

32 



4.3 TOPOGRAPHIC AND GEOTECHNICAL ASPECTS OF COMPONENT 

STRUCTURES 

The river Teesta from its confluence with Kalep Chhu and up to its confluence with 

Zemu Chhu flows N-S in a steeper gradient and is joined by Jongten Chhu, 

Gyamthang Chhu, Chento Chhu and Burum Chhu in the left bank while Goma Chhu 

meets the river in the right bank. The river and most of its tributaries are snow fed. 

The river valley in this stretch is generally narrow with occasional ballooning at 

places, especially in the vicinity of Yathang and Shacham area. The area has a rugged 

terrain with elevations rising from 2500 m to about 6000 m. Also the area is under a 

moderate to thick cover of vegetation. In the river valley, at places moraine deposits 

have been observed. 

The major left bank tributary Zemu Chhu flows NW-SE and meets Teesta near Zemu. 

Between Jekthang and Zemu, this nala is bound by steep N-S trending ridges. Zemu 

Chhu in the vicinity of Dozam is joined by Dozam Chhu and Alakhade Chhu on the 

left and right banks respectively. Towards Zemu, thick vegetal cover has been 

observed along this nala. Few settlements are observed on the banks of river Teesta. 

The area is approachable by a fair weather road, however, Zemu Chhu is approachable 

by foot track, which was reported destroyed during the current visit. 

4.3.1 Diversion Structure 

The proposed dam shall be located about 600 m downstream of the confluence of 

Chento Chhu and Teesta River. In this stretch, the river Teesta takes an easterly 

convex bend and flows in a relatively wider valley. The area during the visit was 

covered by snow (Photo 1A & 1B). Towards the right bank the river is covered by 

debris material, which was noticed along the road and in the uphill. The overburden 

appears to be of the order of ± 30 m below the road, which comprises of boulders and 

pebbles in a silty/clayey matrix. Further uphill, rock exposures are exposed as steep 

rocky escarpments. The river course at present is flowing within a 20-25 m wide

33 



channel. The river valley is occupied by overburden deposit, which may be of the 

order of 10-15 m towards the left bank. The bed load of the river comprises of 

boulders, pebbles and cobbles in a sandy/silty matrix. Towards the left bank rock 

exposures are seen binding the nala slopes. The slopes are moderate to steep. A thin 

veneer of slope wash material hosts sporadic vegetation. Rock type in the area 

comprises of gneisses, which are moderately strong to strong. The diversion area 

needs to be investigated with a back up of subsurface explorations in order to assess 

the extent of overburden cover and nature of bedrock. 

The diversion structure on Zemu Chhu, could not be approached however, the area 

appears to be bound by steep ridges. Rock types comprising of gneisses are expected. 

Before firming up the location of the proposed dam, the area needs to be investigated. 

4.3.2 Water Conductor System 

The water conductor system shall be located in the right hill. The right hill from 

Shacham to Zemu is highly rugged and dissected by several drainages however, no 

major drainage has been observed in this area. In general the E-W trending ridges are 

seen. At places, along the road slope wash deposits were observed. Rock types of the 

area exposed as steep rocky escarpments. The rock types comprise of gneisses, which 

are expected to offer fair to good tunnelling media. In this area quartzites and garnet 

schists have been reported and these may be encountered during tunneling. 

The water conductor system that will carry the water of Zemu Chhu to the proposed 

power house shall be located within the left bank of Zemu Chhu in steep rocky 

escarpments which trend almost N-S and culminate into a NW-SE trending ridge 

towards Zemu. Central Crystallines of Higher Himalaya comprising of gneisses are 

expected during tunnelling. This water conductor system is expected to provide fair to 

good tunnelling media. From the topographic sheet 78 A/9, it is observed that this 

water conductor system will cross below Dozam Chhu nala, accordingly the tunnel

34 



alignment below this nala shall be suitably laced to have a sufficient cover. Sufficient 

super-incumbent cover is otherwise available above both the tunnels. 

4.3.3. Power House 

The proposed powerhouse shall be located in vicinity of Zemu village. At this location 

a NW-SE trending ridge occupies the area between river Teesta and Zemu Chhu. This 

ridge is seen to continuously rise and is steeply laid. A thin veneer of slope wash 

material generally occupies the ridge. However, towards the confluence the area is 

under a thick cover of slope wash deposit (Photo 2). At present an underground 

powerhouse has been contemplated. The area is occupied by rock type of high grade 

gneisses. These are expected to provide fair to good rock media. The orientation of the 

cavern shall be suitably aligned with respect to the principal discontinuity. The 

powerhouse area is required to be investigated for assessing rockmass condition and 

the same need to be taken up during the further course of investigation. The tail waters 

will be discharged into the river Teesta upstream of the confluence of Zemu Chhu and 

river Teesta. 

4.4 SEISMICITY 

The site lies within Zone – IV of seismic zoning map of India IS 1893 (Part – I) 2002. 

IMD data of the region covering longitude 86-90 0 and 25-29 0 has been appended in 

Annexure 4.2, which gives a list of earthquake events that have occurred within the 

region. The probable intensity of earthquake within seismic zone-IV corresponds to 

intensity VIII on Modified Mercali Scale. Notable earthquakes that have occurred 

close to this area are Cachar 1869 (M 7.5), Great Assam Earthquake 1897 (M 8.7), 

Dhubri 1930 (M 7.1), Bihar-Nepal Earthquake 1934 (M 8.3), Assam Earthquake 1950 

(M 8.5) and Nepal-India border earthquake 1988 (M 6.4). The maximum intensity 

experienced in Sikkim region during Great Assam Earthquake, 1897 was VIII (MMI) 

and during Bihar-Nepal border earthquake, 1934 was VII (MMI).

35 



Two major tectonic features occur in the area namely MBT (Main Boundary Thrust) 

and MCT (Main Central Thrust) besides other minor features. Many past occurrences 

of earthquakes have been associated with these major lineaments. Site-specific 

earthquake studies for the scheme are required to be conducted. 

A Technical Report from IMD on seismic history and seismicity of the Teesta basin of 

sikkim covering proposed sites is placed as annexure-4.2. 

4.5 GEO-PHYSICAL SURVEY 

The dam-I is covered with thick snow while the dam-II was not approachable due to 

which Geo-Physical survey was not feasible. However the powerhouse site is having 

rock exposures, hence the Geophysical survey is not required. 

4.6 CONSTRUCTION MATERIAL SURVEY 

The riverbed deposit may not be sufficient for the requirement of construction 

material. The area is bounded by rocky ridges. Therefore additional quarries for 

construction material can be developed. 

4.7 FURTHER STUDIES 

• The foundation for structures are required to be investigated by subsurface 

explorations to assess overburden thickness and its amenability for 

construction of various structures. 

• Construction material survey needs to be conducted to assess its quantity and 

suitability. 

• The possibility of the use of excavated muck may also be explored after 

testing.

36 



Photo-1A: A View of Teesta Valley in Vicinity of Shacham 

Photo-1B: A View of Teesta Valley Indicating Valley Slope

Photo-2: A view of Power House Area 

37 


Teesta (I) HE Project (4 x 80 MW)



CHAPTER – V 

HYDROLOGY

5.1 GENERAL 

CHAPTER –V 

HYDROLOGY 

38 



Teesta-I H.E project is a run of the river scheme, in which two dams have been 

proposed to utilize the discharge of Teesta river. One dam is proposed on Zemu Chu 

and another on the main Teesta river. The project envisages co nstruction of two 

diversion structures, a 45 m high dam above river bed level, on Zemu Chu, about 

200m d/s of confluence of Lohnak Chu with Zemu Chu, having a gross storage 

capacity of about 9.26 Mcum and area of submergence as 43.75 Ha at EL 3265 m and 

another 40m high dam above river bed level, about 500m d/s of confluence of Chento 

Chu with Teesta river, with a gross storage capacity of about 4.00 Mcum and area of 

submergence as 19.57 Ha at EL 3265 m. 

The hydrological investigations and analysis have been carried out for Teesta-I Project 

with a view to: 

• Assess the availability of water for power generation by establishing a series of 

average 10-daily discharges for the project site. 

• Establish the spillway design flood 

• Determine the capacity of the reservoir and the area of submergence at 

different levels including FRL and MDDL. 

• Reservoir sedimentation. 

5.2 RIVER SYSTEM AND BASIN CHARACTERISTICS 

Zemu Chu is one of the major tributary of river Teesta which meets Teesta on its right 

bank. It originates from the Zemu glacier and the upper reaches of the river are 

snowfed. The river Teesta is one of the main Himalayan Rivers, which originates in 

the glaciers of Sikkim at an elevation of over 8500m above mean sea level. It is being 

snow fed by the glaciers Zemu, Changame Khanpu, Talung etc. It is an international

39 



river, which flows through the states of Sikkim and West Bengal in Indian Territory 

and then to Bangladesh. The river rises in mountainous terrain and is formed mainly 

by the union of two hill streams Lachen Chu and Lachung Chu at Chunthang in North 

Sikkim. The river upto this reach generally flows in a very steep gradient and the slope 

of the Teesta river upto the confluence of Lachen chu and Lachung chu is about 1 in 

20. After the confluence of Lachen chu and Lachung chu at Chungthang the river 

gradually increases in width and takes a wide loop flowing down to Singhik dropping 

in elevation from EL 1550 m to EL 750 m. It is here after traversing about 20 Km that 

the river confluences with Tolung Chu. 

The area has a rugged terrain with the surrounding peaks reaching a maximum 

elevation of approximately 4000m. The minimum river bed elevation at both the 

proposed dam sites is about 3230m. The terrain hosts a rich growth of vegetation. In 

general the river flows in southeasterly direction. Numerous valleys are seen in the 

area, which are occupied by cultivated terraces. Few high level terraces have been 

observed in this area especially in vicinity of Lingza and Kayem village. 

5.2.1 Cascade Development In Teesta Basin 

The river Teesta has tremendous potential for development of hydro power, as the 

river descends from an elevation of about 3600m to about 300m over a distance of 

about 175 Km. According to the preliminary reconnaissance survey by Central water 

and power Commission in 1974, the river could be harnessed under a cascade 

development for hydro power generation. The cascade development proposed at that 

stage consisted of power generation in six stages on river Teesta. Out of these 

schemes, NHPC had submitted a DPR for Teesta H.E project, Stage-III in 1990. The 

diversion structure for Teesta-III was proposed to be constructed at Chungthang, 

which lies downstream of the confluence of Lachen Chu and Lachung Chu. Another 

project under Teesta Basin development, which is under execution by NHPC, is 

Teesta Stage-V having an installed capacity of 510 MW, where a diversion structure is

40 



being built at Dikchu, about 2 Km downstream of confluence of Dikchu with Teesta. 

About 70km downstream of Teesta-V, NHPC has been entrusted two projects namely, 

Teesta Low Dam H.E projects, Stage-III & IV, having an installed capacity of 132 

MW and 160 MW respectively. 

The proposed Teesta-I H.E project, lies upstream of Chungthang on Teesta river, 

which was the proposed damsite of Teesta-III H.E project. 

5.2.2 Catchment Area 

The catchment area of the proposed scheme lies between Longitude 88 o 07′22” E to 

88 o 50′35” E and Latitude 27 o 40′36” N to 28 o 06’05” N. The catchment area upto the 

proposed dam site on Zemu Chu is about 881 Sq.km and upto the proposed dam site 

d/s on Teesta river is about 600 Sq.km. Both the catchments are snowfed as well as 

rainfed. The proposed diversion structure on Zemu Chu lies at Longitude 88 o 30′00” E 

and latitude 27 o 46′46” N and that on Teesta river lies at Longitude 88 o 33′25” E and 

latitude 27 o 48′19” N. The catchment Plan showing both the proposed dam sites is 

shown in Plate-5.1. 

The catchment plan has been prepared from the catchment plan of Teesta H.E Project, 

Stage-III as toposheets for entire catchment were not available. The snowfed area for 

both the catchments has been estimated on catchment area proportion in the absence of 

1:50,000 toposheets. The snowfed area of Teesta H.E Project, Stage -III has been 

estimated as 1952 Sq.km in the DPR prepared earlier by NHPC. Thus on this 

catchment area proportion basis, the snowfed areas for Dam-I and Dam-II have been 

estimated as 617 Sq.km and 420 Sq.km respectively. Thus the rainfed and snowfed 

area in the catchments of both dams are 264 Sq.km and 617 Sq.km respectively and 

180 Sq.km and 420 Sq.km respectively.

5.2.3 Temperature And Humidity 

41 



The climate in the region is fairly humid and moist. The abrupt variation in altitude is 

chiefly responsible for abrupt changes in the climatic conditions and aided by the 

complex orography, the area experiences frequent rainfall of varying intensity and 

duration. The maximum and minimum temperature varies from 39 0 C in summer to 6 0 

C in winter and the relative humidity varies from 80% to 100%. Temperature and 

relative humidity observations are being made in the basin at Dikchu site where 

Teesta-V H.E project is being constructed by NHPC and at TLDP-III and TLDP-IV 

sites, as a part of cascade development on Teesta river. The monthly maximum, 

minimum temperatutre and relative humidity at Dikchu from Jan 1998 to Dec 2001 is 

enclosed as Annexure-5.1 and annual maximum and minimum temperature from 

1998 to 2001 is given in Table 5.1. 

Month 

& Year 

Table 5.1 

Temperature And Humidity Data At Dikchu 

Maximum 

Temp o C 

Minimum 

Temp o C 

Max. Relative 

Humidity % 

Min. Relative 

Humidity % 

1998 38.0 7.0 99.0 89.0 

1999 39.0 6.0 99.0 90.0 

2000 39.0 7.0 97.0 85.0 

2001 31.0 11.0 97.0 90.0 

Overall 39.0 6.0 99.0 85.0 

5.2.4 Precipitation Characterstics 

In the Teesta basin the southwest monsoon normally sets in the third week of May and 

withdraws in the second week of October. The major portion of the catchment being 

hilly and the river flowing in steep gradient, heavy rains in the upper and middle 

catchments has an immediate effect of rendering the plains to flash floods.

42 



Sh. B.Biswas and C.V.V Bhadram in their paper titled “A study of major rainstorms of 

Teesta Basin” and published in Mausam (1984), have studied the rainfall distribution, 

major rainstorms and their associated synoptic situations over the catchment based on 

22 years data (1960-81). The entire Teesta catchment extending from its origin in 

north upto the Indo Bangladesh border has been considered. On the basis of the 

rainfall distribution, the Teesta catchment has been divided into three parts viz. upper, 

middle & lower. The average annual rainfall is 1328 mm, 2619 mm & 3289 mm for 

the upper, middle and lower parts respectively. The monthly breakup of the annual 

rainfall of the basin is given in Table 5.2 . 

Table 5.2 

Average Monthly Rainfall (mm) of Teesta Basin 

Month 

Catchment 

Upper Middle Lower 

Jan 21 23 6 

Feb 41 32 16 

Mar 73 66 30 

Apr 72 147 144 

May 142 274 315 

Jun 245 463 547 

Jul 236 621 866 

Aug 222 512 645 

Sep 171 338 495 

Oct 77 112 191 

Nov 15 19 21 

Dec 13 12 13 

Annual 1328 2619 3289 

From the table it is clear that July is the wettest month followed by August and June. 

The upper, middle and lower catchments receive 71.6%, 78.1% and 83.4% of the

43 



annual rainfall respectively due to southwest monsoon. The catchment area upto the 

present proposed scheme comprises the upper and middle portions only. 

The authors have considered 53 rainstorms of duration ranging from one to three days 

in the study. The selection of storms is based on isohyetal analysis of daily rainfall 

values. Out of the 53 rain storms 40 were of 1 day, 11 were of 2 day and only 2 were 

of 3-day duration. It was concluded that 1-day duration storm are more frequent, a fact 

which is also supported by the narrow width of the catchment for which the effect of 

any system lasts for a shorter duration. No storm of longer duration than 3 day is 

reported. Majority of the storms have been reported in July & August. It has also been 

concluded that rain storms over this catchment occur in association with any of the 

following synoptic situations: 

(i) Break monsoon conditions i.e. shifting of the axis of trough close to the 

foothills of the Himalayas. 

(ii) Eastern end of monsoon trough lying north of Latitude 24 0 N. 

(iii) Movement of trough in west lies across the eastern Himalayas ; and 

(iv) Low pressure system lying over or to the west of the catchment. 

Many of the rainstorms studied by the authors were seen to occur due to either of the 

first two synoptic situations in July & August. A combination of first three synoptic 

situations is also a common feature over the area, giving rise to heavy precipitation. 

5.2.4.1 Rain Gauge Network 

As per the paper of Sh. B.Biswas and C.V.V Bhadram, the network density of rain 

gauges in the basin works out to be one raingauge per 300 Sq.km of the basin area. 

The data used by them is of 42 raingauge stations working under Indian Meteorology 

Department (IMD) and Central Water Commision (CWC), 24 of which are equipped 

with self recording raingauges. The rainfall data availability status of the raingauge

44 



stations in the catchment upto Teesta-V H.E project, with NHPC, is shown in Table 

5.3. 

Table 5.3 

Data Availability Status Of Raingauge Stations Upto Teesta-V 

S.No Name of station Period of data availability 

1. Lachung Jul 57 to Dec 58, 1960 to 1964,1970 to 1981, 

Feb 91 to Dec 97 

2. Chunthang Apr 57 to Dec 58, 1960 to 1964,1970 to Jul 

85, 1991 to 1997 

3. Lachen Jan 57 to Dec 58, Jan 60 to Apr64, 1971, Sep 

77 to Jan 78, Jun 92 to Dec 97 

4. Yumthang Jul 57 to Oct 57, 1958, 1960 to 1964, Jan 70 

to Sep 82, Jan 83 to Apr 85 

5. Singhik Sep 75 to Sep 85, 1991 to 1993 

6. Thangu Jan 57 to Dec 58, 1960 to 1964, 1970 to 

7. Dikchu (near Teesta- 

V dam site) 

1974, Jan to Apr 83 

8. Gayzing 1978 to 1988 

9. Yoksam 1978 to 1988 

10 Rangit dam site 1991 to 1997 

1992 to 1997, 2001 to Oct 03 

11. Pelling May 93 to Dec 96 

At all the above raingauge sites, data for few months is missing in between. Raingauge 

sites have also been established near Teesta Low dam projects, Stage-III & IV and are 

operational since August 2000. Lot of efforts has been made to collect all available 

rainfall data in the basin but only rainfall data of 11 stations mentioned above is 

available at present. The annual rainfall of these 11 stations for the available period is 

enclosed as Annexure -5.2.

5.3 WATER AVAILABILITY STUDY 

5.3.1 Stream flow and River gauges 

45 



Since Teesta River offers ideal conditions for cascade development of hydroelectric 

schemes, the discharge passing through the river is measured at various sites by CWC. 

Recently NHPC has also established its various G&D sites on Teesta river since a 

number of projects have been entrusted to NHPC as a part of cascade development on 

the river. These include Teesta-V, and Teesta Low Dam projects, Stage-III & IV. 

However, no G&D data is available in the catchment of proposed projects. The 

various G&D sites and period of data availability in Teesta Basin is shown in Table 

5.4. 

Table 5.4 

Data Availability Status Of G&D Sites In Teesta Basin 

S.No Name of site River Period of availabilty Catchment 

1. Chunthang (Before 

Confluence Of 

Lachung & Lachung 

Chu) 

Are a 

(Sq.km) 

Lachen Chu Jan 76 to Dec 97 1919.25 

2. Chungthang (After Teesta Jan 75 to Jun 86 2786.8 

Confluence Of 

3. 

Lachung & Lachung 

Chu) 

Third Mile Tolung Chu Jan 75 to Aug 85, Apr 731.25 

90 to Apr 98 

4. Lachung Lachung Chu May 76 to Aug 85 634.50 

5. Chuba Yumthang 

Jan 78 to Aug 85 355.5 

6. Zema 

Chu 

Zema Chu Jan 79 to Aug 85 900.0 

7. Sankalang Teesta Dec 89 to May 98 

8. Dikchu (Near Teesta- 

V Damsite) 

Teesta Jan 84 to Oct 96, Jan 97 

to Oct 03 

4307

9. Sirwani (Power House 

Site-Teestav) 

10. Legship (Near Rangit 

Damsite) 

Teesta May 84 to Mar 97, 

46 

2000 

Rangit Jan 77 to Dec 79, Apr 

87 to Dec 87, Jan 90 to 

Dec 91 

11. Teesta Bazar Teesta 1972 to 1994 



12. Samco Ropeway Teesta Aug 2000 till date 7755 

13. Coronation Bridge Teesta 1972 to 1994, Aug 

2000 till date 

14. Domohoni Teesta 1972 to 2000 

5.3.2 Study 

No daily G&D data was available on Zemu Chu, on which one of the dam site for the 

present project is proposed. For the pre feasibility study, water availability for the 

proposed project has been computed based on the following methodologies: 

(i) Based on discharge series of Teesta-III H.E project (1976-1984) 

Average10-daily series recommended for Teesta-III H.E project by CWC at 

Chungthang has been converted at both the proposed sites using catchment area 

reduction (catchment reduction factor : 0.316 and 0.216 for Dam on Zemu Chu and 

Teesta river respectively). Thus a series for the period 1976 to 1984 has been obtained. 

The catchment reduction factor has been obtained on the basis of rainfed area at both 

the sites. The rainfed area at Chungthang is 834 Sq.km and that at proposed dam sites 

on Zemu Chu and Teesta river is 264 Sq.km and 180 Sq.km respectively. 

(ii) Based on observed G&D data at Lachen (1976-1997) 

As both the proposed dam sites are located near the G&D site on Lachen river, G&D 

data observed at Lachen has been converted at both the proposed sites using catchment 

area reduction (catchment reduction factor : 0.46 and 0.314). Rainfed area of both the 

projects has been used in obtaining the catchment reduction factor. The rainfed area at 

8065

47 



Lachen G&D site is 574 Sq.km and that at proposed dam sites on Zemu Chu and 

Teesta river is 264 Sq.km and 180 Sq.km respectively. 

Thus a series for the period 1976 to 1997 has been obtained. Data at Lachen is missing 

for the years 1986-1988, i.e for 3 years. This missing data has been filled from the 

observed data at Dikchu G&D site (Teesta-V) using catchment area reduction. 

Average 10-daily discharge for the above two series developed is worked out and 

compared at both the proposed dam sites. The plots showing this comparison of 

average 10-daily discharge is enclosed at Figure-5.1 and Figure-5.2. Rainfall-runoff 

relationship for consistency check on Lachen G&D data has not been done in the 

absence of sufficient of rainfall data in the catchment. Average 10-daily obtained from 

the above two approaches is almost comparable so need for further statistical checks is 

not felt necessary at this stage. Hence, for pre-feasibility stage, the average 10-daily 

obtained from G&D data at Lachen is recommended for both the dams proposed for 

Teesta-I H.E project. Though the catchment area reduction factor is low for both the 

series, the series from Lachen site has been adopted as Lachen G&D site has a smaller 

catchment area as compared to Chungthang and also lies much near to the proposed 

dam sites. After establishing G&D site near proposed dam axis and obtaining more 

rainfall data in the catchment, detailed water availability study need be done during 

feasibility/DPR stage. The final recommended average10-daily discharge series at 

both the proposed dam sites is enclosed as Annexure -5.3 and Annexure -5.4. 

5.4 RESERVOIR ELEVATION AREA CAPACITY CURVE 

The reservoir elevation-area-capacity curve for both the proposed dam sites of Teesta- 

I H.E project has been prepared from 1:50000 Survey of India toposheets. The 

contours are available at an interval of 40m the minimum contour being of 3240m. 

The area enclosed within the contours has been found using Autocad. Area has been

48 



found from elevation 3240m to 3360m at an interval of 40m. The volume between any 

two elevations is calculated using the conical formula : 

V = H/3 * (A1+A2+√A1A2) 

Where 

V = Volume between two contours 

H = Contour interval 

A1 = Area at level of first contour 

A2 = Area at level of second contour 

The incremental volumes thus computed are added up to obtain cumulative volume. 

The resultant area capacity curve for both the dams is enclosed as Figure -5.3 and 

Figure-5.4. The curve may be improved after receiving contour maps in scale of 

1:15000. The gross storage capacity for dam on Zemu Chu at FRL 3265m is 9.26 

Mcum and submergence area is 43.75 Ha and for dam on Teesta river, the gross 

storage capacity at FRL 3265m is 4.0 Mcum and submergence area is 19.57 Ha. 

5.5.1 DESIGN FLOOD 

Design Flood for a project can be estimated by following approaches: 

(i) Deterministic approach using Unit Hydrograph technique. 

(ii) Statistical approach using Flood frequency analysis 

(iii) Empirical methods 

• Unit Hydrograph technique 

Due to non-availability of G&D data and hourly gauges, design storm values in the 

proposed catchment, rating curves and observed flood hydrographs could not be 

developed for computing the Unit Hydrograph and Design Flood hydrograph. 

• Flood Frequency analysis 

Due to non-availability of long term, consistent G&D data near the proposed scheme, 

frequency analysis could not be done to estimate the design flood.

• Empirical Methods 

49 



The following empirical relationships have been used to estimate the design flood 

peak: 

(i) Dicken’s formula 

Q = CA 3/4 

Where C = Dickens constant with value between 11-14 for North- 

Indian Hilly catchment. A value of 14 has been adopted 

in present study. 

A = Catchment area in sq.km 

Therefore, Q 1 = 14 x 881 3/4 

= 2264 cumec 

Q 2 = 14 x 600 3/4 

= 1697 cumec 

where subscript 1 and 2 stand for the two proposed dams, first on Zemu Chu 

and second on Teesta river respectively. 

(ii) Ali Nawaz Jung formula 

Q = C(0.386A) (0.925-1/14logA) 

Where C = 49 to 60 (55 used) 

Q1 = 55* (0.386*881) (0.925-1/14log(881)) 

= 4210 cumec 

Q2 = 55* (0.386*600) (0.925-1/14log(600)) 

= 3375 cumec 

where subscript 1 and 2 stand for the two proposed dams as explained above. 

(iii) Computation of Design Flood from Design Flood at Teetsa-III using 

Dicken’s formula 

The design flood recommended for Teesta H.E project, Stage-III was 4572 cumec. 

The total catchment area upto Stage-III dam site is 2786 Sq.km. Both the proposed 

dam sites of Teesta-I H.E project are located near Teesta H.E project, Stage -III, both 

the catchments can be assumed to be hydrologically and hydro-meteorologically

50 



similar. Therefore, it seems logical to transpose the design flood value of Teesta-III to 

proposed dam sites on Zemu Chu and Teesta river. This transposition has been done 

by Dicken’s formula using a conversion factor of 0.422 and 0.316 respectively. 

Q 1 = CA 1 n 

Q 2 = CA 2 n 

Where, A 1 = Catchment area of Teesta-I project 

A 2 = Catchment area of Teesta-III project 

Q 1 = Design Flood for Teesta-I project 

Q 2 = Design Flood for Teesta-III project 

C = Dicken’s constant 

n= 0.75 

Q Teesta I(Dam-I) = Q Teesta-III * (A Teesta-I/A Teesta-III) 0.75 

= 1928 cumec 

Q Teesta I (Dam-II) = Q Teesta-III * (A Teesta-I/A Teesta-III) 0.75 

= 1445 cumec 

(iv) Computation of Design Flood from Design Flood at Teetsa-V using 

Dicken’s formula 

The design flood for Teesta-I project has also been estimated by transposing the 

design flood at Teesta-V H.E project using Dicken’s formula. The design flood 

recommended for Teesta-V H.E project, having a catchment area of 4307 Sq.km is 

9500 cumec. The conversion factor for converting it at proposed dam sites for Teesta-I 

project, having a catchment area of 881 Sq.km and 600 Sq.km, comes out to be 0.304 

and 0.228 respectively. 

Q Teesta I (Dam-I) = Q Teesta-V * (A Teesta-I /A Teesta-V) 0.75 

= 2890 cumec 

Q Teesta I (Dam-II) = Q Teesta-V * (A Teesta-I /A Teesta-V) 0.75 

= 2166 cumec

51 



A comparative study of flood peak computed from various methods at both the 

proposed dam sites is placed as Table 5.5. 

.No 

Table 5. 5 

Comparison Of Various Flood Values 

Method used Design Flood-Dam 

on Zemu Chu 

(cumec) 

Design Flood-Dam on 

Teesta river (cumec) 

1. Dickens Formula 2264 1697 

2. Ali Nawaz Jung 

Formula 

3. Transposition of Teesta- 

III Flood peak on the 

basis of Dickens 

formula. 

4. Transposition of Teesta- 

V Flood peak on the 

basis of Dickens 

formula. 

4210 3375 

1928 1445 

2890 2166 

The combined catchment area of both the proposed dams i.e one on Zemu Chu and 

other on Teesta river is 1481 Sq.Km. Taking into account this total catchment area, the 

design flood obtained by transposing the design flood of Teesta-III comes out to be 

2846 cumec. Since the proposed project lies in the vicinity of Teesta-III H.E project, 

the hydrological and hydro-meteorological conditions in their catchments are much 

more similar to Teesta-III. Moreover, to maintain consistency with Lachen H.E 

project, proposed downstream of confluence of Zemu Chu with Teesta river and 

Teesta-III H.E project (proposed dam site at Chunthang), for pre-feasibility stage 

study, a design flood of 1600 cumec and 1300 cumec has been recommended for the 

proposed dam sites, one on Zemu Chu and second on Teesta river respectively. It is

52 



worth to mention here that one of the methods of working out the design flood is on 

the basis of design flood at Teesta-III and Teesta-V, which has been computed using 

both unit hydrograph technique and flood frequency analysis. 

On availability of more data/information, design flood will have to be estimated by 

deterministic approach using unit hydrograph technique and probabilistic approach 

using flood frequency analysis in feasibility stage. 

5.6 SEDIMENTATION 

A rate of sedimentation of 0.1385 Ham/Sq.km/Year has been worked out for Teesta-V 

H.E project based on suspended sediment observations at Dikchu. In the absence of 

sediment data at or near the proposed dam site, the same silt rate of Dikchu may be 

adopted for Teesta-I H.E project too. 

The necessity of Detailed sedimentation study is not felt during PFR stage and the 

same need be done during feasibility/DPR stage with more observed data at the 

proposed site using a suitable method. 

5.7 RECOMMENDATIONS FOR FUTURE STUDIES 

The following are the improvements suggested for feasibility/DPR stage study: 

• Proper raingauge network along with Gauge-discharge-sediment 

observation sites on the river, on which the present projects are proposed, 

need be established before taking up preparation of feasibility report 

/DPR. 

• After establishing gauge and discharge site at or near proposed dam sites 

with proper raingauge network in the basin, detailed water availability 

study need be conducted in feasibility/DPR stage.

53 



• The reservoir elevation area capacity curve need be revised after 

availability of reservoir cross-sections and/or 1:15000 scale contour maps 

in feasibility/DPR stage study. 

• On availability of more data/information, design flood need be estimated 

by deterministic approach using unit hydrograph technique and 

probabilistic approach using flood frequency analysis in feasibility/DPR 

stage. 

• Detailed reservoir sedimentation study need be done during 

feasibility/DPR stage with observed data at/near the proposed dam sites 

using a suitable method.

28°0' 

27°45' 

88°15' 

PAKI CHU 

88°15' 

CATCHMENT PLAN OF TEESTA-I H.E.PROJECT 

LHONAK CHU 

ZEMU CHU 

88°30' 

88°30' 

TEESTA RIVER 

PROPOSED DAM AXIS 

88°45' 

88°45' 

28°0' 

SCALE :- 

KM 

27°45' 

N 

PLATE-5.1 

5 4 3 2 1 0 5 10 15 20 KILOMETRE

55 



TEESTA BASIN PROJECTS Annexure 5.1 

Maximum, Minimum monthly temperature and Relative humidity at Dikchu (Teesta-V dam site) 

Month 1998 1999 2000 2001 

TEMPERATURE RELATIVE 

RELATIVE 

RELATIVE TEMPERATURE 

HUMIDITY TEMPERATURE HUMIDITY TEMPERATURE HUMIDITY 

(%) 

(%) 

(%) 

Max O C Min O C 




RELATIVE 

HUMIDITY 

(%) 

Jan 25 7 92 23 6 90 22 9 90 20 11 96 

Feb 27 8 90 24 7 92 24 7 92 22 14 93 

Mar 30 10 92 28 9 91 N.A N.A N.A 24 15 91 

Apr 36 12 89 34 16 94 32 22 90 29 20 92 

May 38 14 91 35 18 93 36 17 87 29 19 91 

Jun 36 20 98 37 20 99 38 20 89 31 22 93 

Jul 35 20 99 39 21 96 39 22 90 31 20 90 

Aug 36 21 93 38 20 96 36 21 89 30 22 97 

Sep 35 20 93 34 16 97 35 20 89 28 22 95 

Oct 31 16 93 30 15 96 35 16 85 27 19 96 

Nov 29 14 92 28 13 91 31 14 90 25 16 95 

Dec 24 9 92 23 9 91 25 10 97 N.A N.A N.A

Year 

TEESTA BASIN PROJECTS 

56 



Annexure 5.2 

ANNUAL RAINFALL (mm) AT VARIOUS STATIONS IN TEESTA BASIN 

Rainfall In mm At Various Stations 

Lachung Chungthang Lachen Yumthang Singhik Thangu Dikchu Gayzing Yoksam Pelling Rangit Damsite 

1958 2013 2965 1855 1746 N.A 492 N.A N.A N.A N.A N.A 

1960 1660 2656 1773 1592 N.A 716 N.A N.A N.A N.A N.A 

1961 1546 2714 1529 1466 N.A 1204 N.A N.A N.A N.A N.A 

1962 1431 2343 1257 1407 N.A 758 N.A N.A N.A N.A N.A 

1963 1613 2939 1908 1546 N.A 753 N.A N.A N.A N.A N.A 

1964 1624 2301 N.A 1345 N.A 825 N.A N.A N.A N.A N.A 






1975 1615 2582 N.A 1410 N.A N.A N.A N.A N.A N.A N.A 

1976 1758 3638 N.A 1716 3765 N.A 3149 N.A N.A N.A N.A 

1977 2002 3278 N.A 2237 3131 N.A 4090 N.A N.A N.A N.A 

1978 1618 2402 N.A 1252 3433 N.A 3865 2204 3367 N.A N.A 

1979 1827 2775 N.A 1872 2804 N.A 3265 2023 2876 N.A N.A 

1980 2598 2957 N.A 789 4319 N.A 3685 N.A N.A N.A N.A 

1981 2075 2291 N.A 1563 3407 N.A 2799 2784 1770 N.A N.A 

1982 N.A 2181 N.A 919 4428 N.A 2525 1847 3293 N.A N.A 

1983 N.A 2999 N.A 826 4586 N.A 2962 1847 2732 N.A N.A 

1984 N.A 1995 N.A 886 N.A N.A 3016 1112 3055 N.A N.A 

1985 N.A 2659 N.A N.A 4534 N.A 3439 1109 2128 N.A N.A 

1986 N.A N.A N.A N.A N.A N.A N.A 1732 2988 N.A N.A 

1987 N.A N.A N.A N.A N.A N.A N.A 3096 3009 N.A N.A 

1988 N.A N.A N.A N.A N.A N.A N.A 2797 N.A N.A N.A 

1991 N.A 3114 N.A N.A 7011 N.A N.A N.A N.A N.A 2787 

1992 1446 1704 N.A N.A 3555 N.A 2426 N.A N.A N.A 2234 

1993 1610 N.A 1836 N.A 4019 N.A 1988 N.A N.A 2585 2117 

1994 1649 N.A 1415 N.A N.A N.A 1710 N.A N.A 2061 2005 

1995 2167 3164 2398 N.A N.A N.A 2075 N.A N.A 2565 2656 

1996 1841 2872 1874 N.A N.A N.A 2211 N.A N.A 1306 2500 

1997 2298 2849 2152 N.A N.A N.A 2150 N.A N.A 2176

TEESTA (I) H.E PROJECT 

AVERAGE 10-DAILY DISCHARGE - Dam on Zemu Chu 

57 



Annexure 5.3 

YEAR/MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC AVG 

I 10.33 9.59 11.22 15.23 18.02 28.62 51.81 43.80 46.50 16.59 13.15 7.92 

1976 II 9.89 9.42 12.03 16.67 14.27 55.85 49.37 47.75 26.82 13.10 10.89 6.77 22.09 

III 9.41 9.82 13.04 19.49 20.00 40.52 37.58 51.05 19.58 13.23 9.74 6.26 

I 5.58 9.35 5.17 9.93 10.82 30.78 45.38 52.22 35.83 29.82 15.57 9.70 

1977 II 5.30 9.11 7.37 9.31 13.37 54.60 53.39 43.94 29.30 18.80 14.21 10.25 22.00 

III 5.08 5.46 6.84 9.90 19.05 39.71 63.95 51.31 24.43 15.02 10.73 11.59 

I 7.97 7.38 6.72 9.58 16.56 45.46 52.96 64.84 34.12 32.13 17.11 12.11 

1978 II 7.14 7.23 7.19 12.27 33.94 47.70 56.76 54.79 44.43 25.05 12.76 10.26 25.98 

III 7.29 6.64 7.97 14.53 39.63 60.32 54.78 41.14 33.40 21.35 12.56 9.22 

I 8.50 7.02 7.82 14.89 27.88 32.39 57.71 57.15 47.07 50.21 25.62 18.71 

1979 II 7.85 7.01 8.20 14.81 35.53 38.76 55.20 45.12 41.08 34.26 20.86 15.41 27.94 

III 7.71 7.62 10.08 18.58 27.18 55.57 61.84 47.86 30.13 25.70 19.64 14.83 

I 13.98 12.80 14.71 22.88 31.89 44.59 70.27 76.16 66.55 33.03 22.34 17.39 

1980 II 13.46 13.42 15.09 29.35 27.27 59.34 71.94 83.64 52.17 28.38 20.34 15.81 35.57 

III 13.34 14.30 20.37 33.44 29.07 66.40 75.37 69.66 42.22 26.44 18.72 14.36 

I 13.83 11.90 14.64 18.33 33.58 38.72 80.31 63.17 62.03 38.85 26.78 16.24 

1981 II 12.97 12.24 15.50 23.21 36.27 46.31 68.87 66.66 53.16 35.95 21.37 14.61 34.15 

III 12.80 14.81 18.31 27.34 35.17 62.87 64.78 64.80 42.37 31.43 17.70 11.45 

I 10.52 11.45 12.04 20.18 28.01 53.96 57.68 51.22 43.78 29.41 18.63 13.90 

1982 II 11.71 11.89 13.48 20.14 31.46 59.43 64.62 48.49 63.31 24.70 16.25 12.82 30.92 

III 11.54 11.56 16.06 22.34 30.56 65.69 76.23 56.91 41.54 23.78 15.73 12.13 

I 12.03 6.83 10.16 17.27 28.45 57.04 88.47 61.12 60.86 55.50 30.49 19.25 

1983 II 10.72 6.79 13.02 14.12 34.09 55.35 75.26 64.81 68.42 54.71 28.01 18.04 37.93 

III 7.51 9.45 11.74 17.68 45.36 77.25 74.67 75.71 78.93 37.29 23.07 16.17

58 




I 14.43 12.18 26.82 30.96 37.47 80.83 100.47 96.10 103.90 66.25 48.25 23.76 

1984 II 14.20 12.65 29.97 33.00 54.75 97.20 100.80 96.36 99.15 84.03 41.69 23.37 55.34 

III 12.64 12.15 29.45 33.01 77.7 9 87.29 106.57 100.88 78.65 64.74 37.06 23.47 

I 23.67 21.27 29.90 36.29 37.22 38.61 107.68 95.48 50.29 34.60 20.28 13.30 

1985 II 22.48 19.44 32.38 43.80 43.20 48.20 140.52 100.72 48.04 30.33 17.63 12.03 47.84 

III 19.46 23.53 30.15 51.72 60.17 136.57 118.15 123.31 40.26 24.99 15.62 11.07 

I 10.49 9.98 12.53 13.78 18.73 25.51 55.53 55.39 46.28 37.73 20.26 13.93 

1986 II 10.44 10.27 13.64 17.81 19.92 43.27 69.38 47.61 57.48 28.22 18.02 12.83 28.30 

III 9.88 11.76 14.01 19.98 20.99 64.12 62.41 52.71 46.79 22.03 15.57 9.46 

I 8.26 6.91 7.02 19.07 19.90 43.10 60.28 61.01 80.04 36.46 18.85 9.53 

1987 II 7.78 6.85 8.33 13.32 22.14 62.60 57.62 66.56 42.82 27.16 11.50 8.72 28.78 

III 7.29 7.51 10.46 17.60 25.98 52.54 64.43 44.49 58.72 23.22 10.10 7.97 

I 7.78 7.54 9.10 15.84 21.28 34.07 83.92 72.10 47.94 30.53 13.44 10.73 

1988 II 7.78 7.89 13.47 17.89 31.88 49.30 65.92 66.18 32.33 20.26 12.13 10.18 30.09 

III 7.68 8.77 13.85 20.81 42.24 54.00 72.65 100.41 36.16 16.30 11.30 9.63 

I 5.90 6.32 6.99 7.61 19.21 42.92 76.55 60.83 45.38 32.26 13.89 8.94 

1989 II 5.74 5.78 7.13 9.12 19.84 71.10 75.30 47.72 41.10 27.45 11.27 7.75 27.97 

III 5.69 6.15 7.33 10.94 48.34 75.19 70.10 46.82 40.84 22.33 10.25 6.79 

I 6.19 5.11 4.24 3.64 10.99 47.04 59.22 55.04 47.62 26.61 13.65 7.80 

1990 II 5.74 4.80 3.46 6.01 19.36 45.95 75.50 55.91 45.60 27.11 10.20 6.43 24.23 

III 5.20 4.64 3.52 7.45 22.28 53.73 64.61 49.62 31.75 22.30 8.52 5.55 

I 5.62 5.28 5.42 17.09 17.31 24.97 41.41 50.43 48.36 31.60 17.04 9.66 

1991 II 5.51 5.02 6.18 9.74 21.09 39.43 40.35 58.10 51.09 25.05 15.07 7.41 22.65 

III 5.45 5.08 6.51 10.31 23.33 36.26 43.98 48.01 39.58 20.56 11.49 6.52 

I 5.93 5.32 5.27 6.44 8.11 10.48 24.88 31.30 29.97 18.44 8.31 6.66 

1992 II 4.92 5.13 5.30 9.05 9.44 14.94 25.17 31.43 29.50 13.23 7.39 5.76 13.75 

III 5.03 4.92 5.45 8.27 9.49 28.96 28.60 34.16 24.42 11.25 6.73 5.32

59 




I 5.41 4.96 8.32 8.83 14.66 17.16 59.07 77.68 74.21 52.52 27.71 21.85 

1993 II 5.46 5.27 8.30 9.65 13.20 21.92 59.06 73.65 62.50 38.97 24.42 20.08 29.39 

III 5.12 5.09 8.69 11.55 13.37 28.20 69.27 70.54 59.09 33.40 22.39 16.50 

I 15.54 14.42 13.62 15.09 19.42 35.55 46.71 46.39 41.33 27.97 18.74 12.45 

1994 II 14.47 13.79 12.29 18.89 20.02 47.06 49.53 45.31 41.39 24.87 15.45 11.39 26.24 

III 14.62 14.78 15.54 17.33 24.62 54.63 50.47 48.72 35.77 22.77 12.91 10.77 

I 10.21 10.11 9.21 11.77 31.04 53.77 73.93 52.08 42.11 26.80 13.25 11.39 

1995 II 10.32 10.08 8.73 14.58 47.92 57.50 62.01 52.55 37.71 26.09 15.14 10.14 28.67 

III 10.20 10.13 12.03 21.28 46.30 58.25 47.67 46.68 36.28 20.38 15.22 9.42 

I 8.12 8.83 8.74 9.92 26.13 29.74 49.98 45.79 42.96 31.35 23.36 13.30 

1996 II 8.07 7.86 10.12 9.64 22.91 25.18 53.81 42.70 41.00 28.73 21.72 12.03 24.74 

III 8.53 8.61 10.79 21.44 31.71 44.98 47.90 43.04 35.66 25.68 19.32 11.07 

I 12.52 12.08 12.19 13.38 15.97 20.97 46.02 38.12 32.68 23.57 11.17 8.43 

1997 II 11.91 12.04 12.79 13.30 18.37 29.89 39.83 46.51 37.01 15.45 10.32 8.23 20.37 

III 12.10 11.90 13.95 13.69 18.97 36.80 33.27 30.56 29.96 12.20 9.35 7.77 

I 10.33 9.59 11.22 15.23 22.77 38.61 62.66 58.89 50.29 34.60 20.28 13.30 

AVG II 9.89 9.42 12.03 16.67 27.17 48.20 64.07 58.22 48.04 30.33 17.63 12.03 29.36 

III 9.41 9.82 13.04 19.49 32.76 58.38 62.62 57.93 40.26 24.99 15.62 11.07 

Note: 1. All discharge data in cumecs. 

2. Total no. of years - 22

TEESTA-I H.E PROJECT 

AVERAGE 10-DAILY DISCHARGE - Dam on Teesta river 

60 



Annexure-5.4 


I 7.04 6.54 7.65 10.38 12.28 19.51 35.32 29.87 31.71 11.31 8.97 5.40 

1976 II 6.74 6.42 8.20 11.36 9.73 38.08 33.66 32.56 18.29 8.93 7.43 4.62 15.06 

III 6.41 6.70 8.89 13.29 13.64 27.63 25.62 34.81 13.35 9.02 6.64 4.26 

I 3.80 6.38 3.52 6.77 7.38 20.99 30.94 35.60 24.43 20.33 10.62 6.61 

1977 II 3.62 6.21 5.03 6.35 9.11 37.23 36.40 29.96 19.98 12.82 9.69 6.99 15.00 

III 3.46 3.72 4.67 6.75 12.99 27.07 43.60 34.98 16.66 10.24 7.31 7.90 

I 5.43 5.03 4.58 6.53 11.29 31.00 36.11 44.21 23.27 21.90 11.67 8.26 

1978 II 4.87 4.93 4.90 8.36 23.14 32.53 38.70 37.36 30.30 17.08 8.70 7.00 17.71 

III 4.97 4.53 5.43 9.91 27.02 41.12 37.35 28.05 22.77 14.56 8.56 6.28 

I 5.80 4.79 5.33 10.15 19.01 22.08 39.35 38.96 32.09 34.23 17.47 12.75 

1979 II 5.35 4.78 5.59 10.09 24.23 26.43 37.64 30.76 28.01 23.36 14.22 10.51 19.05 

III 5.26 5.20 6.87 12.67 18.53 37.89 42.16 32.63 20.54 17.52 13.39 10.11 

I 9.53 8.73 10.03 15.60 21.74 30.40 47.91 51.93 45.37 22.52 15.23 11.86 

1980 II 9.18 9.15 10.29 20.01 18.60 40.46 49.05 57.03 35.57 19.35 13.87 10.78 24.25 

III 9.09 9.75 13.89 22.80 19.82 45.28 51.39 47.49 28.79 18.03 12.77 9.79 

I 9.43 8.12 9.98 12.50 22.90 26.40 54.76 43.07 42.29 26.49 18.26 11.08 

1981 II 8.84 8.35 10.57 15.82 24.73 31.58 46.96 45.45 36.24 24.51 14.57 9.96 23.28 

III 8.73 10.09 12.48 18.64 23.98 42.86 44.17 44.18 28.89 21.43 12.07 7.81 

I 7.17 7.81 8.21 13.76 19.10 36.79 39.33 34.92 29.85 20.05 12.70 9.48 

1982 II 7.98 8.11 9.19 13.74 21.45 40.52 44.06 33.06 43.17 16.84 11.08 8.74 21.08 

III 7.87 7.88 10.95 15.23 20.84 44.79 51.97 38.80 28.32 16.22 10.73 8.27 

I 8.20 4.66 6.92 11.78 19.40 38.89 60.32 41.67 41.49 37.84 20.79 13.12 

1983 II 7.31 4.63 8.87 9.63 23.24 37.74 51.32 44.19 46.65 37.30 19.10 12.30 25.86 

III 5.12 6.44 8.00 12.05 30.93 52.67 50.91 51.62 53.81 25.43 15.73 11.03

61 




I 9.84 8.30 18.29 21.11 25.54 55.11 68.50 65.52 70.84 45.17 32.90 16.20 

1984 II 9.68 8.62 20.44 22.50 37.33 66.27 68.73 65.70 67.60 57.30 28.43 15.94 37.73 

III 8.62 8.28 20.08 22.51 53.04 59.52 72.66 68.78 53.63 44.14 25.27 16.00 

I 16.14 14.50 20.38 24.75 25.38 26.32 73.42 65.10 34.29 23.59 13.83 9.07 

1985 II 15.33 13.26 22.08 29.86 29.45 32.86 95.81 68.67 32.76 20.68 12.02 8.20 32.62 

III 13.27 16.05 20.56 35.27 41.02 93.12 80.56 84.07 27.45 17.04 10.65 7.54 

I 7.16 6.81 8.55 9.39 12.77 17.39 37.86 37.76 31.55 25.73 13.81 9.50 

1986 II 7.12 7.00 9.30 12.15 13.58 29.50 47.31 32.46 39.19 19.24 12.29 8.75 19.29 

III 6.74 8.02 9.55 13.62 14.31 43.72 42.55 35.94 31.90 15.02 10.61 6.45 

I 5.63 4.71 4.79 13.00 13.57 29.39 41.10 41.60 54.57 24.86 12.85 6.50 

1987 II 5.30 4.67 5.68 9.08 15.10 42.68 39.29 45.38 29.19 18.52 7.84 5.94 19.62 

III 4.97 5.12 7.13 12.00 17.71 35.82 43.93 30.33 40.04 15.83 6.89 5.44 

I 5.30 5.14 6.20 10.80 14.51 23.23 57.22 49.16 32.69 20.82 9.16 7.32 

1988 II 5.30 5.38 9.19 12.20 21.73 33.61 44.95 45.12 22.05 13.81 8.27 6.94 20.52 

III 5.24 5.98 9.45 14.19 28.80 36.82 49.54 68.46 24.66 11.11 7.71 6.57 

I 4.02 4.31 4.77 5.19 13.10 29.26 52.20 41.47 30.94 21.99 9.47 6.10 

1989 II 3.91 3.94 4.86 6.22 13.53 48.47 51.34 32.54 28.03 18.72 7.68 5.29 19.07 

III 3.88 4.20 4.99 7.46 32.96 51.26 47.79 31.92 27.84 15.22 6.99 4.63 

I 4.22 3.49 2.89 2.48 7.49 32.07 40.38 37.52 32.47 18.14 9.31 5.32 

1990 II 3.91 3.27 2.36 4.10 13.20 31.33 51.47 38.12 31.09 18.48 6.95 4.39 16.52 

III 3.54 3.16 2.40 5.08 15.19 36.64 44.06 33.83 21.65 15.20 5.81 3.78 

I 3.83 3.60 3.69 11.65 11.80 17.03 28.24 34.38 32.98 21.54 11.62 6.59 

1991 II 3.76 3.42 4.21 6.64 14.38 26.89 27.51 39.61 34.84 17.08 10.27 5.05 15.44 

III 3.72 3.46 4.44 7.03 15.91 24.72 29.99 32.73 26.99 14.02 7.84 4.45 

I 4.04 3.63 3.59 4.39 5.53 7.15 16.96 21.34 20.43 12.57 5.67 4.54 

1992 II 3.36 3.49 3.62 6.17 6.44 10.19 17.16 21.43 20.11 9.02 5.04 3.93 9.37 

III 3.43 3.35 3.72 5.64 6.47 19.74 19.50 23.29 16.65 7.67 4.59 3.63

62 




I 3.69 3.38 5.67 6.02 10.00 11.70 40.27 52.97 50.60 35.81 18.89 14.90 

1993 II 3.72 3.59 5.66 6.58 9.00 14.95 40.27 50.21 42.62 26.57 16.65 13.69 20.04 

III 3.49 3.47 5.93 7.88 9.11 19.23 47.23 48.09 40.29 22.77 15.27 11.25 

I 10.59 9.83 9.28 10.29 13.24 24.24 31.85 31.63 28.18 19.07 12.78 8.49 

1994 II 9.87 9.40 8.38 12.88 13.65 32.09 33.77 30.89 28.22 16.96 10.53 7.77 17.89 

III 9.97 10.08 10.60 11.82 16.79 37.24 34.41 33.22 24.39 15.53 8.80 7.35 

I 6.96 6.90 6.28 8.02 21.16 36.66 50.40 35.51 28.71 18.27 9.04 7.77 

1995 II 7.04 6.87 5.96 9.94 32.67 39.21 42.28 35.83 25.71 17.79 10.32 6.91 19.55 

III 6.95 6.91 8.20 14.51 31.57 39.72 32.50 31.83 24.74 13.90 10.38 6.42 

I 5.53 6.02 5.96 6.77 17.82 20.28 34.08 31.22 29.29 21.37 15.93 9.07 

1996 II 5.50 5.36 6.90 6.57 15.62 17.17 36.69 29.11 27.95 19.59 14.81 8.20 16.87 

III 5.82 5.87 7.35 14.62 21.62 30.67 32.66 29.34 24.31 17.51 13.17 7.54 

I 8.54 8.24 8.31 9.12 10.89 14.30 31.38 25.99 22.28 16.07 7.62 5.75 

1997 II 8.12 8.21 8.72 9.07 12.52 20.38 27.16 31.71 25.24 10.53 7.04 5.61 13.89 

III 8.25 8.11 9.51 9.33 12.94 25.09 22.68 20.83 20.43 8.32 6.38 5.29 

I 7.04 6.54 7.65 10.38 15.53 26.32 42.72 40.15 34.29 23.59 13.83 9.07 

AVG II 6.74 6.42 8.20 11.36 18.53 32.86 43.68 39.69 32.76 20.68 12.02 8.20 20.02 

III 6.41 6.70 8.89 13.29 22.33 39.80 42.70 39.50 27.45 17.04 10.65 7.54 

Note: 1. All discharge data in cumecs. 

2. Total no. of years - 22

75 

70 

65 

60 

55 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

Jan I 

II 

III 

Feb I 

II 

III 


Comparison of average 10-daily discharges for Dam Proposed on Zemu Chu 

Mar I 

II 

III 

Apr I 

II 

III 

May I 

II 

III 

Jun I 

II 

III 

63 

Jul I 

II 

III 

Aug I 

II 

III 

Sep I 

II 

Transferred from Chunthang 

Transferred from Lachen 

III 

Oct I 

II 

III 

Nov I 

II 

III 

Dec I 

II 

Figure-5.1 

III

Discharge (cumec) 

55 

50 

45 

40 

35 

30 

25 

20 

15 

10 

5 

0 

Jan I 

II 

III 

Feb I 

II 


Comparison of average 10-daily discharges for Dam Proposed on Teesta River 

III 

Mar I 

II 

III 

Apr I 

II 

III 

May I 

II 

III 

Jun I 

II 

III 

64 

Jul I 

II 

Period 

III 

Aug I 

II 

III 

Sep I 

II 

Transferred from Chunthang 

Transferred from Lachen 

III 

Oct I 

II 

III 

Nov I 

II 

III 

Dec I 

II 

Figure-5.2 

III

Elevation(m) Area(Ha) Capacity(Ha.m) Capacity(Ha.m) 

3230 0.00 0.00 0 

3240 12.21 40.71 0.407083 

3280 65.68 1456.90 14.56897 

3320 103.98 4820.95 48.20947 

3360 152.85 9926.32 99.26318 

TEESTA H.E. PROJECT (STAGE-I) 

Reservoir Elevation-Area-Capacity Curve at Dam-I on Zemu Chu river 

Elevation(m) 

3360 

3340 

3320 

3300 

3280 

3260 

3240 

10000 

9000 

8000 

3220 

3220 

0 20 40 60 80 100 120 140 160 

65 

7000 

6000 

Area Curve 

Capacity(Ha.m) 

5000 

Area(Ha) 

4000 

3000 

2000 

This curve is drawn with 1:50000 scale toposheet and it 

is for pre-feasibility stage only. 

1000 

Capacity Curve 

0 

3360 

3340 

3320 

3300 

3280 

3260 

3240 

Figure-5.3

Elevation(m) Area(Ha) Capacity(Ha.m) Capacity(Ha.m) 

3230 0.00 0.00 0 

3240 5.71 19.04 0.1904167 

3280 27.89 635.29 6.3529014 

3320 57.52 2307.92 23.079241 3320 

3360 90.47 5242.85 52.428504 

TEESTA H.E. PROJECT (STAGE-I) 

Reservoir Elevation-Area-Capacity Curve at Dam-II on Teesta River 

Elevation(m) 

3360 

3340 

3300 

3280 

3260 

3240 

5000 

Figure-5.4 

3220 

3220 

0 10 20 30 40 50 60 70 80 90 100 

66 

4000 

Area Curve 

Capacity(Ha.m) 

3000 

Area(Ha) 

2000 

This curve is drawn with 1:50000 scale toposheet and it is 

for pre-feasibility stage only. 

1000 

Capacity Curve 

0 

3360 

3340 

3320 

3300 

3280 

3260 

3240 

Elevation (m)



CHAPTER – VI 

CONCEPTUAL LAYOUT & 

PLANNING

CHPAPER-VI 

CONCEPTUAL PLANNING AND LAYOUT 


67 



The Teesta (I) H.E. project is located in the North district of Sikkim state. It is a run of 

the river scheme proposed to harness hydel potential of river Teesta and river Zemu, a 

tributary of River Teesta.The maximum gross head of 590 m is proposed to be utilised 

for generating 320 MW of Power. Two small reservoirs of adequate capacity are 

proposed to be provided in two basins as operating pools to meet diurnal peaking load 

demands. 

6.2 PROJECT COMPONENTS 

• Two nos. 6 m diameter horseshoe shaped Diversion Tunnels one for dam-I on 

Zemu Chu and other for dam-II on Teesta River, of 600 m & 300 m long 

respectively with u/s & d/s coffer dams. 

• Two Concrete dams one 45 m high and other 60m high above deepest 

foundation level of 350m & 240m length respectively. 

• Two power Intake Structures for dam-I & dam-II leading to 2 Nos. 4.5 m dia 

D-shaped intake tunnels. 

• Two Nos.underground Desilting Chambers for dam-I & dam-II each of size 

200m (L) X 8 m (W) X 12 m (H) 

• Two 4m-diameter horseshoe shaped concrete lined 3.5 kms and 4.25Km long 

Head Race Tunnels with two adits for dam-I and dam-II respectively. 

• One 15-m diameter & approx. 75 m high semi-Underground Surge Shaft. 

• Two circular inclined Pressure Shaft of 2.5m diameter, 825m long each 

bifurcating to feed 4 units of vertical Pelton wheel turbine. 

• Underground Power House of size 141m x 22m x 40m consisting of four units 

of 80 MW each.

68 



• One no.5 m diameter Horseshoe shaped tailrace tunnel of about 1000 m length. 

The conceptual planning and lay-out of project components have been worked out 

based on S.O.I topo sheets of 1:50000 scale with contour intervals 40 m. 

6.2.1 Conceptual layout 

The choice of location of the dams has been made keeping in view the 

topography, geology, other prospective schemes in the u/s and maximum water 

availability at these sites. Two reservoirs are proposed to be created in two 

basins with separate intake structure, desilting chambers and headrace tunnels 

to fulfill peaking requirement. The location of the powerhouse has been fixed 

keeping the tailrace outlet at EL 2675 m. The TWL has been kept at EL 2675m just 

u/s of the confluence of Zemu & Teesta. It is not possible to further lower down the 

TWL in the downstream beyond the confluence as there is another scheme proposed 

Just d/s of the confluence. The optimum positioning of tailrace outlet can be decided 

after detailed survey of the area because the contours in the top sheet are unable to 

give clear and specific information of the topography of the area near confluence. 

Thus, the scheme shall utilize a maximum head of 590m. 

Another alternative during FR/DPR can be studied with a feeder tunnel feeding 

the water of Teesta into Zemu and creating a slightly bigger reservoir & bigger 

HRT& DC etc.& altogether removing one HRT and reducing the height of 

Dam on Teesta.The upcoming hydroelectric projects i.e Talem & Jedang on 

Teesta River and Lohnak respectively have been taken into consideration in the 

conceptual planning of the project. 

The layout plan of schemes in Upper Part of Teesta basin and cascade 

development schemes of Teesta river basin are enclosed as Plate -1 & Plate-2 

respectively.

69 



Based on the reconnaissance survey, hydrological and topographical studies on 

topo sheets and input data of ranking study, a conceptual layout plan of the 

project was prepared and discussed in CEA for vetting during Feb’04. The 

summary record of discussions of meeting on conceptual layout was conveyed by 

CEA vide letter no. 7/9/NHPC/2003/HPI/303 dated 16.02.2004 and placed as 

Annexure. 

6.2.2 Dam and River diversion works 

The choice of type of the dams have been made keeping in view the topography, 

geology, fast implementation of the project and construction material for the diversion 

structures. Construction of two 45m & 60m high concrete Dams above the deepest 

foundation level have been proposed on Zemu & Teesta respectively. The availability 

of construction materials for the dams, cofferdams, and their suitability has been 

discussed elsewhere in the report. 

The possibility of concrete face rockfill dams can be looked into during the 

preparation of FR/DPR based on more geological information at the dam sites and 

availability of construction material. 

6.2.2.1 Dam-I 

Dam-I is proposed on 500m d/s of confluence of Lohnak Chu with Zemu Chu. Width 

of the valley at this Dam site is about 350 m at EL 3270 m.Average bed level at Dam 

site is EL 3230 m.The overflow section of this dam is 50 m long and Non –overflow 

section is 300 m consisting 125 m on right abutment and 175 m on left abutment. 

FRL is proposed to be fixed at EL 3265 and MDDL at El.3260 m. keeping in view the 

pondage requirement and inflow of water in Lohnak chu and Zemu chu during lean 

period.

70 



The spillway for dam-I have five bays each of size 4 m X 6 m with 3.0 m wide 

piers.The spillway is designed to pass a probable maximum flood of 1600 cumecs 

with one gate inoperative. The crest of spillway has been kept at EL3250 m. The low- 

level orifice type spillway has been provided to flush out the sediment accumulated in 

the reservoir to maintain the live storage capacity of the reservoir. 

6.2.2.2 Dam-II 

Dam-II is proposed on 700 m d/s of confluence of chento chu with Teesta river. Width 

of the valley at this Dam site is about 240 m at EL 3270 m. Average bed level at Dam 

site is EL 3230 m. The depth of overburden at this location varies from 10-15m in the 

river to 25-30m below the right bank road. The overflow section of lower dam is 42 m 

long and Non overflow section is 198 m consisting 98 m on right abutment and 100 m 

on left abutment. FRL is proposed to be fixed at EL 3265 and MDDL at El.3258 m. 

keeping in view the pondage requirement and inflow of water in Chento chu and 

Teesta river during lean period. 

The spillway for dam-II have four bays each of size 4.5 m X 6 m with 3.0 m wide 

piers.The spillway is designed to pass a probable maximum flood of 1300 cumecs 

with one gate inoperative.The crest of spillways has been kept at EL3250 m. The low- 

level orifice type spillway has been provided to flush out the sediment accumulated in 

the reservoir to maintain the live storage capacity of the reservoir. 

The top width of both the non-overflow sections has been fixed as 8 m. The d/s slope 

of the Non-overflow section has been proposed as 0.8H: 1V and u/s slope as 0.1H: 1V. 

The top of both the dams has been proposed to be kept at EL 3270 m.The rock 

foundation is expected at EL 3225 m and EL3210m after removal of approx. 5 m and 

±20m thick overburden respectively for dam-I & dam-II.The project area falls within 

Zone-IV of seismic zoning map.

6.2.3 Reservoirs 

71 



The reservoir capacity formed by construction of both the dams has a gross storage 

pre-sedimentation capacity of 13.26 M.cum and live storage capacity of 2.82 M cum 

out of which the reservoir of dam-I has the gross storage pre-sedimentation capacity of 

9.26 M.cum and live storage capacity of 1.78 M while reservoir for dam-II has the 

gross storage pre-sedimentation capacity of 4.00 M.cum and live storage capacity of 

1.04 M respectively. After sedimentation, the reservoir is likely to have an adequate 

live storage capacity for running the power station at full capacity for 3-4 hours in a 

day during the period of lean flows. 

6.2.4 River diversion Works 

Two nos. 6 m diameter horseshoe shaped Diversion Tunnels have been proposed to 

divert a flood of approx. 400 cumecs.The diversion tunnel for dam-I is on the right 

bank while diversion tunnel for dam-II is on the left bank.The diversion tunnel for 

dam-I is 600m long while diversion tunnel for dam-II is 300 m long with u/s & d/s 

coffer dams. 

The design diversion discharge has been decided based on the experience of various 

ongoing NHPC projects in Teesta valley and fast track completion of the project. This 

data shall however need to be firmed up during the preparation of detailed project 

report with the availability of more hydrological data & experience gained in the basin 

e.g.: during the construction of Teesta-V project and other upcoming projects. In order 

to divert the river during construction of the dams, an u/s cofferdam of approx. height 

15m and d/s cofferdam of 8 m height is proposed for both the dams. 

6.2.5 Power Intake & Desilting Chambers 

6.2.5.1 Power Intake 

Two nos. power intake structures are proposed one on the left bank of the Zemu chu 

and the other on the right bank of Teesta river. Each intake structure consists of two

72 



no. Intakes and two no. D-shaped intake tunnels of dia 4.5 m each.Each intake 

structure is designed to pass 38.10 cumecs, which includes flushing discharge i.e. 

about 20% of discharge in headrace tunnel i.e. 31.76cumecs. Both the intake structures 

have been designed for equal discharges keeping in view the operating conditions 

during peaking. 

In both the intake structures, two no. intakes are proposed to keep the desilting 

chambers dimension within the manageable limits and to put either of the desilting 

chambers to inspection and maintenance while the other is in operation.The invert 

level of the intake structures has been kept at 10m higher than the spillway crest to 

check the sediments entry in the water conductor system.The intake structures shall be 

provided with the trash racks to prevent the entry of trash into the water conductor 

system. The gross area of the trash racks shall be determined to give a velocity of not 

more than 1.5m/s. A mechanical raking machine operated from El.3270 m shall clean 

the racks. 

6.2.5.2 Desilting Chambers 

For the efficient, trouble free and continuous operation of turbines with least possible 

wearing and erosion damages due to silt, it is necessary to remove 90% of the 

sediments larger than 0.2 mm-particle size. 

For both the water conductor system, two nos. 200 m long 8 m wide Dufour type 

Desilting chambers with height 12 m shall be provided to remove 90% of particles 

having size greater than or equal to 0.2 mm. A silt flushing conduit at the bottom of 

each chamber runs along the length and two flushing tunnels join to form a single silt 

flushing tunnel of size 2 m x 3.0 m d-shaped and ± 500 m length which will discharge 

the sediment back into the river d/s of the dam. Thus practically silt free water will be 

led into the headrace tunnel.

73 



In the desilting chambers for both the water conductor system, two separate intakes 

lead the water to two independent desilting chambers, spaced at 30 m c/c, through 25 

m long upstream transition which will gradually reduce the velocity of water in the 

chamber to around 0.25m /sec. The chambers have been provided with central gutter 

with holes to facilitate the flushing of settled silt particles through the flushing tunnel. 

The requirement of desilting chambers is being foreseen, on the lines of Teesta-V 

project, which is located in the middle part of the Teesta basin. 

6.2.6 Head Race Tunnel, Surge Shaft, and Pressure Shaft 

6.2.6.1 Head Race Tunnel 

From dam-I & dam-II, two 4 m diameter concrete lined horseshoe shaped headrace 

tunnels of 3.5 km & 4.25 km length respectively, and each having a slope of 1 in 250 

is proposed to carry a design discharge of 31.76 cumecs. The diameter of the headrace 

tunnel has been fixed keeping the velocity of water in HRT within permissible limits 

and working area requirement. 

Both the headrace tunnels are meeting at the surge shaft. The Invert level of headrace 

tunnel is fixed at EL. 3250 m near intake. The rock cover above headrace tunnel 

generally is more i.e.+600 m. The low cover reaches are confined to prominent nalla 

crossings.Two nos. construction adits of 4m dia are proposed for both the headrace 

tunnels to facilitate excavation of headrace tunnel within the scheduled completion 

time. The location of the adits and portals are indicative and the actual lengths may 

vary.The tunnels are proposed to be concrete lined with 250 mm thick plain M-20 

concrete. The rock support treatment shall consist of grouted rock bolts/anchors and 

shotcrete with or without wire mesh. In rock class of IV & V steel ribs supports is 

envisaged. 

6.2.6.2 Surge Shaft 

A vertical, restricted orifice type semi-underground surge shaft of 15 m finished dia 

and about 75 m height has been proposed with its top opening into a platform at

74 



elevation EL + 3310 m. Surge shaft is proposed to be concrete lined with 0.75 m thick 

R.C.C. Its bottom is kept at EL 3236 m at the HRT and surge shaft junction. The 

transient studies shall be required to be done to work out the maximum and minimum 

levels for the worst operating conditions. 

6.2.6.3 Pressure Shaft 

Two no. Steel lined inclined circular Pressure Shaft of 2.5m diameter and 825m length 

takes off from the surge shaft which bifurcates to feed water to four units of vertical 

Pelton wheel turbine each of 80 MW. 

6.2.7 Power House Complex & Tail Race Tunnel 

6.2.7.1 Power House Complex 

The underground Power House is located on the Right bank of Teesta river u/s of the 

confluence of Zemu chu with Teesta river. It will have an installed capacity of 320 

MW (4 generating units of 80 MW each). The support system shall comprise of rock 

bolts and wiremesh and shotcrete. The centerline of the turbines is proposed at EL 

2677.82 m. One number electrically operated overhead traveling crane (E.O.T) shall 

be provided for handling the electrical and mechanical equipment. A lift shall be 

provided near the service bay for approaching the lower parts of power house.The 

overall dimensions of the Power House are 141m x 22m x 40m. A Control block area 

shall be located on one end of machine hall. The transformer cavern cum gate shaft is 

proposed 30m d/s of powerhouse cavern and a 8m wide MIV chamber is proposed on 

the u/s of the power house cavern.The power house has been kept underground 

keeping in view the available geological information of the area. 

A cable tunnel of size 2.0 m x 3.0 m will take off from transformer cavern and shall 

carry cables to a surface switchyard. The Switchyard measuring approx. 250 m x 170 

m shall be formed in cutting/filling.

6.2.7.2 Tail Race Tunnel 

75 



Water from the turbines is discharged through four concrete lined tailrace tunnels, 

which merge into a single tailrace tunnel and carry the water to the confluence of 

Zemu Chu with Teesta river. This tunnel is 5 m diameter horseshoe and about 1000m 

long with invert at EL.2674m at tailrace outlet. The TWL has been kept at EL 2675m 

just at the confluence. It is not possible to further lower down the TWL in the 

downstream beyond the confluence. The optimum positioning of tailrace outlet can be 

fixed after detailed survey of the area because the contours in the top sheet are unable 

to give clear picture of the topography of the area near confluence. Thus, the scheme 

shall utilize a maximum head of 590m. 

6.3 FURTHER STUDIES 

6.3.1 Topographical Studies 

1. Topographical contour Survey of both the dam areas and Power House area in 

1:5000 scale with 5m contour interval. 

2. Survey in 1:1000 scale for locating the adits of the HRT. 

3. The survey in Dam area and at tailrace outlet shall be undertaken to firm up the 

power potential of the project. 

6.3.2 Geological and Geo-technical investigations 

1. Geological/geotechnical investigations including surface mapping and subsurface 

explorations like exploratory drilling and seismic profiling at the dam and 

powerhouse area. 

2. Rock mechanic lab tests shall be required for finding out the properties of the rock 

material. 

3. Construction material survey shall be required to be undertaken involving drifts, 

pits, and topographical surveys of the borrow/quarry areas. 

4. Site-specific studies for earthquake design parameters shall also be required to be 

undertaken.

76 



6.3.3 Design Studies 

1 Hydraulic design of various structures like spillway, power intake, desilting 

chambers, transient studies of surge shaft & the optimization studies for HRT 

depending on varying flow conditions during peaking hours in both the water 

conductor system shall be required for firming up the dimensions. 

2 Stability analysis of non-overflow and overflow sections shall have to be done 

taking into account the approved seismic parameters. 

3 Hydraulic model studies for reservoir and Dam spillway shall be required for the 

confirmation of design parameters. 

4 Sedimentation analysis for working out the post sedimentation storage capacity of 

the reservoir. 

5 Alternative studies for location, type and layout of main components based on 

detailed topographical and geological studies. 

6.4 HYDRO- MECHENICAL EQUIPMENT 

6.4.1 Dam-I 

6.4.1.1 Diversion Tunnel Gate And Hoist 

After the construction of the dam, for the purpose of plugging the diversion tunnel, 

one numbers fixed wheel type gate will be provided at the inlet of the tunnel. The gate 

shall be operated by means of electrically operated rope drum hoist located on the 

hoist platform installed over the trestle above deck level. The gate is meant for one 

time closure, just before plugging of the tunnel. 

6.4.1.2 Spillway Radial Gates, Hoists, Stoplogs And Gantry Crane 

Five submerged type radial gates shall be provided to control the discharge through 

the gated portion of the spillway. Each gate shall be operated by means of suitable 

capacity hydraulic hoist from a power pack and two double acting cylinders (one on 

each end of the gate) having a provision of 25% pushing force.

77 



One trolley mounted mobile gasoline engine operated power pack capable of operating 

one gate at 25% of the normal rated speed is envisaged for emergency operation of 

spillway radial gates. 

One portable oil filter unit for filtration, dehydration & degasification of hydraulic oil 

is also envisaged. 

One set of stoplog has been envisaged to cater to the maintenance requirement of five 

nos. spillway radial gates. The spillway stoplog shall be lowered / raised under 

balanced head condition by means of a suitable capacity Gantry crane with the help of 

a lifting beam. 

Suitable de-icing system for radial gates & stoplogs shall be provided, if required in 

accordance with IS: 10021:2000. 

6.4.1.3 Trash Rack, Trash Rack Cleaning Machine, Intake Gate, Bulkhead 

Gates And Hoists 

Upstream face of the intake shall be provided with the trash rack screen, which will be 

cleaned by means of a trash rack-cleaning machine. 

Two numbers fixed wheel type gates shall be provided just downstream of the bell 

mouth of the intake. The intake gates are to be designed for self-lowering against 

flowing water corresponding to FRL. The gate shall be operated by means of 

electrically operated rope drum hoist of suitable capacity. 

Suitable de-icing system for trash rack & intake gate shall be provided , if required in 

accordance with IS: 10021:2000.

78 



For maintenance and inspection of intake gates and embedded parts, two numbers 

vertical slide gates have been proposed on the upstream of the intake gates. The slide 

gates shall be operated by means of a electrically operated rope drum hoist under 

balance head condition. 

6.4.1.4 Desilting Chamber Gate 

One slide type gate has been envisaged to cater to the maintenance requirement of two 

nos. desilting chambers. The gate shall be lowered / raised under balanced head 

condition by means of a suitable capacity EOT Crane. 

6.4.1.5 Silt Flushing Tunnel Gates And Hoists 

In two silt-flushing tunnels, each tunnel is provided with a set of two slide (emergency 

& service) gates for regulating the discharge through flushing tunnels. Both the 

(emergency & service) gates shall be operated by means of hydraulic hoists. The gate 

grooves are provided with bonnet structures embedded in the concrete & a watertight 

bonnet cover at the top of the groove. 

6.4.1.6 U/S Surge Shaft Gate And Hoist 

In order to isolate HRT of dam I from surge shaft, one slide type gate shall be 

provided at the upstream of surge shaft. The gate shall be designed for maximum 

surge level but shall be operated under balanced head condition by means of an 

electrically operated rope drum hoist. Suitable de-icing system for surge shaft gate 

shall be provided , if required in accordance with IS: 10021:2000. 

6.4.1.7 Adit Inspection Gate 

One adit shall be provided with manually operated hinged type gates in the concrete 

plug at the HRT construction to give access to the head race tunnel in the event of any 

inspection, repair and maintenance.

6.4.1.8 Instrument And Remote Control 

79 



Gates shall be provided with PLC based remote control system for Control and 

operation of gates and automatic control of the reservoir level. 

6.4.1.9 Diesel Generating Set 

One diesel generating set complete with all accessories will be provided for 

emergency operation of gates and hoists. 

6.4.2 Dam-II 

6.4.2.1 Diversion Tunnel Gate And Hoist 

After the construction of the dam, for the purpose of plugging the diversion tunnel, 

one number fixed wheel type gate will be provided at the inlet of the tunnel. The gate 

shall be operated by means of electrically operated rope drum hoist located on the 

hoist platform installed over the trestle above deck level. The gate is meant for one 

time closure, just before plugging of the tunnel. 

6.4.2.2 Spillway Radial Gates, Hoists, Stoplogs And Gantry Crane 

Four submerged type radial gates shall be provided to control the discharge through 

the gated portion of the spillway. Each gate shall be operated by means of suitable 

capacity hydraulic hoist from a power pack and two double acting cylinders (one on 

each end of the gate) having a provision of 25% pushing force. 

One trolley mounted mobile gasoline engine operated power pack capable of operating 

one gate at 25% of the normal rated speed is envisaged for emergency operation of 

spillway radial gates. 

One portable oil filter unit for filtration, dehydration & degasification of hydraulic oil 

is also envisaged.

80 



One set of stoplog has been envisaged to cater to the maintenance requirement of four 

nos. spillway radial gates. The spillway stoplog shall be lowered / raised under 

balanced head condition by means of a suitable capacity Gantry crane with the help of 

a lifting beam. 

Suitable de-icing system for radial gates & stoplogs shall be provided , if required in 

accordance with IS: 10021:2000. 

6.4.2.3 Trash Rack, Trash Rack Cleaning Machine, Intake Gate, Bulkhead 

Gates And Hoists 

Upstream face of the intake shall be provided with the trash rack screen, which will be 

cleaned by means of a trash rack-cleaning machine. 

Two numbers fixed wheel type gates shall be provided just downstream of the bell 

mouth of the intake. The intake gates are to be designed for self-lowering against 

flowing water corresponding to FRL. The gate shall be operated by means of 

electrically operated rope drum hoist of suitable capacity. 

Suitable de-icing system for trash rack & intake gate shall be provided , if required in 

accordance with IS:10021:2000. 

For maintenance and inspection of intake gates and embedded parts, two numbers 

vertical slide gates have been proposed on the upstream of the intake gates. The slide 

gates shall be operated by means of a electrically operated rope drum hoist under 

balance head condition. 

6.4.2.4 Desilting Chamber Gate 

One slide type gate has been envisaged to cater to the maintenance requirement of two 

nos. desilting chambers. The gate shall be lowered / raised under balanced head 

condition by means of a suitable capacity EOT Crane.

6.4.2.5 Silt Flushing Tunnel Gates And Hoists 

81 



In two silt-flushing tunnels, each tunnel is provided with a set of two slide (emergency 

& service) gates for regulating the discharge through flushing tunnels. Both the 

(emergency & service) gates shall be operated by means of hydraulic hoists. The gate 

grooves are provided with bonnet structures embedded in the concrete & a watertight 

bonnet cover at the top of the groove. 

6.4.2.6 U/S Surge Shaft Gate And Hoist 

In order to isolate HRT of dam II from surge shaft, one slide type gate shall be 

provided at the upstream of surge shaft. The gate shall be designed for maximum 

surge level but shall be operated under balanced head condition by means of an 

electrically operated rope drum hoist. Suitable de-icing system for surge shaft gate 

shall be provided, if required in accordance with IS: 10021:2000. 

6.4.2.7 Adit Inspection Gate 

One adit shall be provided with manually operated hinged type gates in the concrete 

plug at the HRT construction to give access to the head race tunnel in the event of any 

inspection, repair and maintenance. 

6.4.3 D/S Surge Shaft Gate And Hoist 

Two slide type gates are provided at the downstream of surge shaft to isolate the 

pressure shafts from the surge shaft. The gates shall be designed for maximum surge 

level but shall be operated under balanced head condition by means of an electrically 

operated independent rope drum hoist. Suitable de-icing system for surge shaft gates 

shall be provided, if required in accordance with IS: 10021:2000.

6.4.4 Pressure Shaft Steel Liner 

82 



Two no. Pressure Shaft of dia. 2500 mm fully steel lined will take off from d/s of steel 

transition of Surge Shaft to feed the turbine placed in the powerhouse. It comprises 

horizontal & inclined ferrules, 2 nos. Vertical bends, 2 nos. plan bends, 1 no. 

bifurcation and branch pipes for each pressure shaft for feeding four turbines. 

The material of Pressure Shaft liner shall conform to ASTM A537 Class 1. However 

bifurcation material shall conform to ASTM A517 Gr. F. 

6.4.5 Tailrace Gate And Hoist 

In order to isolate tailrace tunnel from the river, one wheel type gate has been 

envisaged. The gate shall be operated under balanced head conditions by a suitable 

capacity rope drum hoist. Adjoining civil structure shall be provided with by-pass 

valve to create balanced head condition. 

6.4.6 Instrument And Remote Control 

Gates shall be provided with PLC based remote control system for Control and 

operation of gates and automatic control of the reservoir level. 

Remote control system of both the reservoirs shall be interconnected together with the 

help of optical fiber cable, which will be routed through the respective headrace 

tunnels. 

6.4.7 Diesel Generating Set 

One diesel generating set complete with all accessories will be provided for 

emergency operation of gates and hoists.



CHAPTER – VII 

POWER POTENTIAL STUDIES

7.1 GENERAL 

CHAPTER-VII 

POWER POTENTIAL STUDIES 

83 



The Power potential studies of Teesta I HE Project has been made for 90% dependable 

year based on 21 hydrological years, from 1976-77 (June) to 1996-97 (May) as given 

in table 7.1. The salient features of the project are as follows: 

FRL (EL) =3265 m 

MDDL (EL) =3258 m 

TWL = EL 2675 m 

Centre line of M/C = EL 2677.82 m 

Rated net head = 576.85 m 

Type of turbine = Vertical Pelton 

Rated Discharge of Plant = 63.52 cumecs 

Proposed Plant Capacity = 320 MW (4 x 80MW) 

Generation voltage = 11KV 

Design Energy = 1298.12 MU in the 90% dependable year with 

95% machine availability 

Minimum Peaking (Hrs) = 3.23hrs (approx.) 

7.2 AVAILABLE FLOW 

The discharge data for the 90% dependable hydrological year is given in Table 7.3. 

For carrying out the power potential and optimisation studies, the following statistics 

have been computed. 

Year: 

Each 10-daily period of the year represents the average of the flow recorded for the 

corresponding period of each year.

90% Dependable Year: 

84 



This is the lower decile of the series of the corresponding 10-daily period of the record 

i.e. (N+1) x 0.9 th year where N is the years for which continuous hydrological data are 

available. The 90% dependable year comes out to be 1976-77 whose calculations are 

shown in table 7.2. 

7.3 DEFINITION OF TERMS 

Annual Energy 

This is the yearly energy provided during the 90% dependable hydrological year with 

95% machine availability. 

Firm Power 

This is the power capacity, which can be guaranteed continuously during the lean 

period in 90% dependable year. During lean inflow period the firm power comes out 

to be 43.03 MW. 

7.4 FULL RESERVOIR LEVEL (FRL) AND MINIMUM DRAW DOWN 

LEVEL (MDDL) 

FRL and MDDL have been fixed at EL 3265 m & EL 3258 m respectively based on 

civil consideration. This project is envisaged as a run of the river scheme with small 

pondage. 

7.5 OPERATING HEAD AND HEAD LOSSES 

The net operating head for turbines has been derived from the following formula 

where head losses are taken as 8 m. 

Net operating head =MDDL+2/3 (FRL-MDDL)-TCL-Head losses 

The net operating head comes out to 576.85 m.

7.6 INSTALLED CAPACITY 

85 



The studies for power output and annual energy generation for the 90% dependable 

year has been given in Table 7.4 (A). Considering water availability the total installed 

capacity has been selected as 320 MW. 

7.7 SIZE OF GENERATING UNITS 

The power load demand in India is increasing at a very rapid rate and both 

hydroelectric and thermal (including nuclear) Power potential in the country are being 

developed not only to meet the overall requirements, but stimulatingly also to provide 

a proper mix of hydro and thermal power for optimum operation of the system. 

Keeping this in view current practice is to opt for largest size hydro units permissible 

within the parameters of economy, operating efficiency, maintenance, optimum 

utilization of available water, transport limitation etc. It is therefore proposed to install 

4 units each of 80 MW capacity with Pelton turbine as prime mover. 

7.8 ENERGY GENERATION 

The energy generation in the 90% dependable year (1976-77) indicating lean inflow 

period and high inflow period is shown in Table 7.4 (B). It may be seen from Table 

7.4 (A) that the total unrestricted energy generation is 1507.628 MU. Annual energy 

generation at 320 MW comes out to be 1298.12 MU. Annual load factor for lean and 

monsoon periods of all years have been shown in Table 7.4 (C). Incremental benefits 

have been shown in Table 7.6 which comes out to be 2.17 for this year. Also annual 

energy generation unrestricted has been indicated in table 7.7(A) to 7.7(U) for 21 

hydrological years. Energy available at bus bar shall be 1282.58 MU after allowing 

auxiliary consumption of 0.7% and transformer losses of 0.5% respectively.

Table-7.1 

DISCHARGE DATA 

86 


Teesta (I) HE Project, (4 x 80 MW) 

1976- 1977- 1978- 1979- 1980- 1981- 1982- 1983- 1984- 1985- 1986- 1987- 1988- 1989- 1990- 1991- 1992- 1993- 1994- 1995- 1996- 

PERIOD 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 

I 48.13 51.77 76.46 54.47 74.99 65.12 90.75 95.93 135.94 64.93 42.90 72.49 57.30 72.18 79.11 42.00 17.63 28.86 59.79 90.43 50.02 

JUN II 93.93 91.83 80.23 65.19 99.80 77.89 99.95 93.09 163.47 81.06 72.77 105.28 82.91 119.57 77.28 66.32 25.13 36.87 79.15 96.71 42.35 

III 68.15 66.78 101.44 93.46 111.68 105.73 110.48 129.92 146.81 229.69 107.84 88.36 90.82 126.45 90.37 60.98 48.70 47.43 91.87 97.97 75.65 

I 87.13 76.32 89.07 97.06 118.18 135.07 97.01 148.79 168.97 181.10 93.39 101.38 141.14 128.75 99.60 69.65 41.84 99.34 78.56 124.33 84.06 

JUL II 83.03 89.79 95.46 92.84 120.99 115.83 108.68 126.58 169.53 236.33 116.69 96.91 110.87 126.64 126.97 67.86 42.33 99.33 83.30 104.29 90.50 

III 63.20 107.55 92.13 104.00 126.76 108.95 128.20 125.58 179.23 198.71 104.96 108.36 122.19 117.89 108.67 73.97 48.10 116.50 84.88 80.17 80.56 

I 73.67 87.82 109.05 96.11 128.09 106.24 86.14 102.79 161.62 160.58 93.15 102.61 121.26 102.30 92.56 84.81 52.64 130.65 78.02 87.59 77.01 

AUG II 80.31 73.90 92.15 75.88 140.67 112.11 81.55 109.00 162.06 169.39 80.07 111.94 111.30 80.26 94.03 97.71 52.86 123.86 76.20 88.38 71.81 

III 85.86 86.29 69.19 80.49 117.15 108.98 95.71 127.33 169.66 207.38 88.65 74.82 168.87 78.74 83.45 80.74 57.45 118.63 81.94 78.51 72.38 

I 78.21 60.26 57.39 79.16 111.92 104.32 73.63 102.35 174.74 84.58 77.83 134.61 80.63 76.32 80.09 81.34 50.40 124.81 69.51 70.82 72.25 

SEP II 45.11 49.28 74.73 69.09 87.74 89.40 106.48 115.07 166.75 80.80 96.67 72.01 54.38 69.13 76.69 85.93 49.61 105.12 69.61 63.42 68.95 

III 32.93 41.09 56.17 50.67 71.01 71.26 69.86 132.74 132.28 67.71 78.69 98.76 60.82 68.68 53.40 66.57 41.07 99.38 60.16 61.02 59.97 

I 27.90 50.15 54.03 84.44 55.55 65.34 49.46 93.34 111.42 58.19 63.46 61.32 51.35 54.25 44.75 53.14 31.01 88.33 47.04 45.07 52.72 

OCT II 22.03 31.62 42.13 57.62 47.73 60.46 41.54 92.01 141.33 51.01 47.46 45.68 34.07 46.17 45.59 42.13 22.25 65.54 41.83 43.88 48.32 

III 22.25 25.26 35.91 43.22 44.47 52.86 40.00 62.72 108.88 42.03 37.05 39.05 27.41 37.55 37.50 34.58 18.92 56.17 38.30 34.28 43.19 

I 22.12 26.19 28.78 43.09 37.57 45.04 31.33 51.28 81.15 34.11 34.07 31.70 22.60 23.36 22.96 28.66 13.98 46.60 31.52 22.29 39.29 

NOV II 18.32 23.90 21.46 35.08 34.21 35.94 27.33 47.11 70.12 29.65 30.31 19.34 20.40 18.95 17.15 25.34 12.43 41.07 25.98 25.46 36.53 

III 16.38 18.04 21.12 33.03 31.49 29.77 26.46 38.80 62.33 26.27 26.18 16.99 19.01 17.24 14.33 19.33 11.32 37.66 21.71 25.60 32.49 

I 13.32 16.31 20.37 31.46 29.25 27.32 23.38 32.37 39.96 22.37 23.43 16.03 18.05 15.04 13.12 16.25 11.20 36.75 20.94 19.16 22.37 

DEC II 11.39 17.24 17.26 25.92 26.59 24.57 21.56 30.34 39.31 20.23 21.58 14.66 17.12 13.04 10.82 12.46 9.69 33.77 19.16 17.05 20.23 

III 10.52 19.49 15.50 24.94 24.15 19.26 20.40 27.20 39.47 18.61 15.91 13.41 16.20 11.42 9.33 10.97 8.95 27.75 18.12 15.84 18.61 

I 9.38 13.40 14.30 23.51 23.26 17.69 20.23 24.27 39.81 17.65 13.89 13.08 9.92 10.41 9.45 9.97 9.10 26.13 17.17 13.65 21.06 

JAN II 8.92 12.01 13.20 22.64 21.81 19.69 18.03 23.88 37.81 17.56 13.08 13.08 9.65 9.65 9.27 8.28 9.18 24.34 17.36 13.57 20.03 

III 8.54 12.26 12.97 22.43 21.53 19.41 12.63 21.26 32.73 16.62 12.26 12.92 9.57 8.74 9.17 8.46 8.61 24.59 17.15 14.35 20.35 

I 15.73 12.41 11.81 21.53 20.02 19.26 11.49 20.48 35.77 16.79 11.62 12.68 10.63 8.60 8.88 8.95 8.34 24.25 17.01 14.85 20.32 

FEB II 15.32 12.16 11.79 22.57 20.59 20.00 11.42 21.27 32.70 17.27 11.52 13.27 9.72 8.07 8.44 8.62 8.86 23.19 16.95 13.22 20.25 

III 9.18 11.17 12.82 24.05 24.90 19.44 15.89 20.43 39.58 19.78 12.63 14.75 10.35 7.80 8.54 8.27 8.56 24.86 17.04 14.48 20.01 

I 8.69 11.30 13.15 24.74 24.62 20.25 17.08 45.11 50.28 21.08 11.81 15.30 11.76 7.13 9.11 8.86 13.99 22.90 15.49 14.70 20.50 

MAR II 12.40 12.09 13.79 25.38 26.07 22.67 21.89 50.41 54.46 22.94 14.01 22.66 11.99 5.82 10.39 8.92 13.96 20.67 14.69 17.02 21.51 

III 11.51 13.40 16.95 34.26 30.79 27.01 19.74 49.53 50.71 23.56 17.59 23.30 12.32 5.92 10.95 9.17 14.62 26.14 20.23 18.14 23.46 

I 16.70 16.11 25.04 38.48 30.83 33.94 29.05 52.07 61.04 23.17 32.07 26.64 12.80 6.12 28.74 10.83 14.85 25.38 19.79 16.69 22.50 

APR II 15.66 20.63 24.90 49.36 39.03 33.88 23.75 55.50 73.66 29.96 22.40 30.09 15.34 10.11 16.38 15.22 16.23 31.77 24.52 16.21 22.37 

III 16.65 24.44 31.25 56.24 45.98 37.57 29.73 55.52 86.99 33.60 29.60 35.00 18.40 12.53 17.34 13.91 19.43 29.15 35.79 36.06 23.02 

I 18.20 27.85 46.89 53.63 56.48 47.11 47.85 63.01 62.60 31.50 33.47 35.79 32.31 18.48 29.11 13.64 24.66 32.66 52.20 43.95 26.86 

MAY II 22.48 57.08 59.76 45.87 61.00 52.91 57.33 92.08 72.65 33.50 37.24 53.61 33.37 32.56 35.47 15.88 22.20 33.67 80.59 38.53 30.89 

III 32.04 66.65 45.71 48.89 59.15 51.40 76.29 130.83 101.19 35.30 43.69 71.04 81.30 37.47 39.24 15.96 22.48 41.41 77.87 53.33 31.91

YEAR 

Table-7.2 

UNRESTRICTED ENERGY GENERATION 

UNRESTRICTED ENERGY 

ARRANGED IN DESCENDING 

ORDER 

87 



RANK OF 

THE YEAR 

1984-1985 4252.932 1 

1983-1984 3219.240 2 

1985-1986 2992.987 3 

1980-1981 2640.150 4 

1981-1982 2464.967 5 

1993-1994 2432.426 6 

1979-1980 2278.309 7 

1982-1983 2271.297 8 

1987-1988 2239.032 9 

1988-1989 2127.924 10 

1986-1987 2054.866 11 

1995-1996 2006.027 12 

1994-1995 1997.378 13 

1978-1979 1971.684 14 

1989-1990 1960.706 15 

1990-1991 1881.894 16 

1996-1997 1849.212 17 

1977-1978 1771.042 18 

1991-1992 1581.860 19 

1976-1977 1507.628 20 

1992-1993 1086.764 21 

90% dependable year 

=(N+1) x 0.9th year (where N=no. of years) 

=(21+1)*0.9th year 

=20 

1976-77 is 90% dependable year 

1986-87 is 50% dependable year 

Unrestricted energy of 90% dependable year is 1507.628MU 

90% dependable energy when power restricted to 230 MW is 1298.12 MU

88 



Table-7.3 

90% DEPENDABLE FLOWS FOR POWER GENERATION 

MONTH/PERIOD 90% dependable year 1976-77 inflow (cumecs) 

JUN 

JUL 

AUG 

SEP 

OCT 

NOV 

DEC 

JAN 

FEB 

MAR 

APR 

MAY 

10- daily series for the dam 10- daily series for the dam 

on Zemu Chu. 

on Teesta River. 

I 28.62 19.51 

II 55.85 38.08 

III 40.52 27.63 

I 51.81 35.32 

II 49.37 33.66 

III 37.58 25.62 

I 43.80 29.87 

II 47.75 32.56 

III 51.05 34.81 

I 46.50 31.71 

II 28.62 18.29 

III 19.58 13.35 

I 16.59 11.31 

II 13.10 8.93 

III 13.23 9.02 

I 13.15 8.97 

II 10.89 7.43 

III 9.74 6.64 

I 7.92 5.40 

II 6.77 4.62 

III 6.26 4.26 

I 5.58 3.80 

II 5.30 3.62 

III 5.08 3.46 

I 9.35 6.38 

II 9.11 6.21 

III 5.46 3.72 

I 5.17 3.52 

II 7.37 5.03 

III 6.84 4.67 

I 9.93 6.77 

II 9.31 6.35 

III 9.90 6.75 

I 10.82 7.38 

II 13.37 9.11 

III 19.05 12.99

PERIOD INFLOW HEA 

D 

POWER UNRES 

ENERGY 

Table-7.4A 

POWER POTENTIAL STUDY OF 90% DEPENDABLE YEAR 1976-1977 

ENERGY AT DIFFERENT RESTRICTED CAPACITIES 

89 


Teesta (I) HE Project, (4 x 80 MW) 

CUMEC (M) IN MW (MU) 230 MW 240 MW 250 MW 260 MW 270 MW 280 MW 290 MW 300 MW 310 MW 320 MW 330 MW 340 MW 350 MW 360 MW 380 MW 390 MW 

JUNE I 48.13 576.85 242.486 58.197 55.200 57.600 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 58.197 

II 93.93 576.85 473.232 113.576 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 91.200 93.600 

III 68.15 576.85 343.349 82.404 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 82.404 82.404 82.404 82.404 

JULY I 87.13 576.85 438.973 105.354 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 91.200 93.600 

II 83.03 576.85 418.317 100.396 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 91.200 93.600 

III 63.20 576.85 318.410 84.060 60.720 63.360 66.000 68.640 71.280 73.920 76.560 79.200 81.840 84.060 84.060 84.060 84.060 84.060 84.060 84.060 

AUG I 73.67 576.85 371.160 89.078 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 89.078 89.078 

II 80.31 576.85 404.613 97.107 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 91.200 93.600 

III 85.86 576.85 432.575 114.200 60.720 63.360 66.000 68.640 71.280 73.920 76.560 79.200 81.840 84.480 87.120 89.760 92.400 95.040 100.320 102.960 

SEPT I 78.21 576.85 394.033 94.568 55.200 57.600 60.000 62.400 64.800 67.200 69.600 72.000 74.400 76.800 79.200 81.600 84.000 86.400 91.200 93.600 

II 45.11 576.85 227.270 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 54.545 

III 32.93 576.85 165.906 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 39.817 

OCT I 27.90 576.85 140.564 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 33.735 

II 22.03 576.85 110.990 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 26.638 

III 22.25 576.85 112.099 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 29.594 

NOV I 22.12 576.85 111.444 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 26.746 

II 18.32 576.85 92.299 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 22.152 

III 16.38 576.85 82.525 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 19.806 

DEC I 13.32 576.85 67.108 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 16.106 

II 11.39 576.85 57.384 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 13.772 

III 10.52 576.85 53.001 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 13.992 

JAN I 9.38 576.85 47.258 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 11.342 

II 8.92 576.85 44.940 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 10.786 

III 8.54 576.85 43.026 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 11.359 

FEB I 15.73 576.85 79.250 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 19.020 

II 15.32 576.85 77.184 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 18.524 

III 9.18 576.85 46.250 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 8.880 

MAR I 8.69 576.85 43.781 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 10.508 

II 12.40 576.85 62.473 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 14.994 

III 11.51 576.85 57.989 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 15.309 

APR I 16.70 576.85 84.137 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 20.193 

II 15.66 576.85 78.897 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 18.935 

III 16.65 576.85 83.885 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 20.132 

MAY I 18.20 576.85 91.694 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 22.007 

II 22.48 576.85 113.257 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 27.182 

III 32.04 576.85 161.422 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 42.615 

ENERGY OBTAINED ON 100% M/C 

AVAILABILITY 1507.628 1131.73 1156.21 1178.89 1200.97 1223.05 1245.13 1267.21 1289.29 1311.37 1333.03 1352.47 1371.91 1389.75 1406.79 1438.75 1453.39 

FRL= EL 3265 

MDDL= EL 3258 

TWL= 2675 

LOSSES= 8 m 

OVERALL EFFICIENCY= 89.30%

90 


Teesta(I) HE Project (4 x 80 MW) 

Table-7.4 (B) 

POWER POTENTIAL STUDY OF 90% DEPENDABLE YEAR 1976-1977 WITH 

95% MACHINE AVAILABILITY 

Net Head 

576.85 m 

Restricted to 320 

MW 

PERIOD INFLOW 

(cumecs) 

JUNE 

JULY 

AUG 

SEPT 

OCT 

NOV 

DEC 

JAN 

FEB 

MAR 

APR 

MAY 

HEAD 

(m) 

UNREST 

RICTED 

POWER 

IN MW 

Design Discharge 

63.52 cumecs 

UNRESTRI 

CTED 

ENERGY 

(MU) 

POWE 

R 

REST 

RICTE 

D TO 

320 

MW 

Overall efficiency 89.30% 

ENERGY 

(MU) AT 

320 MW 

WITH 95% 

MACHINE 

AVAILABI 

LITY 

ENERGY 

DURING 

HIGH 

INFLOW 

PERIOD 

ENERGY 

DURING 

LEAN 

INFLOW 

PERIOD 

10 1-10 48.13 576.85 242.49 58.197 242.49 58.197 58.197 0.000 

10 11-20 93.93 576.85 473.23 113.576 320.00 72.960 72.960 0.000 

10 21-30 68.15 576.85 343.35 82.404 320.00 72.960 72.960 0.000 

10 1-10 87.13 576.85 438.97 105.354 320.00 72.960 72.960 0.000 

10 11-20 83.03 576.85 418.32 100.396 320.00 72.960 72.960 0.000 

11 21-31 63.20 576.85 318.41 84.060 318.41 80.256 80.256 0.000 

10 1-10 73.67 576.85 371.16 89.078 320.00 72.960 72.960 0.000 

10 11-20 80.31 576.85 404.61 97.107 320.00 72.960 72.960 0.000 

11 21-31 85.86 576.85 432.57 114.200 320.00 80.256 80.256 0.000 

10 1-10 78.21 576.85 394.03 94.568 320.00 72.960 72.960 0.000 

10 11-20 45.11 576.85 227.27 54.545 227.27 54.545 54.545 0.000 

10 21-30 32.93 576.85 165.91 39.817 165.91 39.817 39.817 0.000 

10 1-10 27.90 576.85 140.56 33.735 140.56 33.735 33.735 0.000 

10 11-20 22.03 576.85 110.99 26.638 110.99 26.638 26.638 0.000 

11 21-31 22.25 576.85 112.10 29.594 112.10 29.594 29.594 0.000 

10 1-10 22.12 576.85 111.44 26.746 111.44 26.746 26.746 0.000 

10 11-20 18.32 576.85 92.30 22.152 92.30 22.152 22.152 0.000 

10 21-30 16.38 576.85 82.52 19.806 82.52 19.806 19.806 0.000 

10 1-10 13.32 576.85 67.11 16.106 67.11 16.106 0.000 16.106 

10 11-20 11.39 576.85 57.38 13.772 57.38 13.772 0.000 13.772 

11 21-31 10.52 576.85 53.00 13.992 53.00 13.992 0.000 13.992 

10 1-10 9.38 576.85 47.26 11.342 47.26 11.342 0.000 11.342 

10 11-20 8.92 576.85 44.94 10.786 44.94 10.786 0.000 10.786 

11 21-31 8.54 576.85 43.03 11.359 43.03 11.359 0.000 11.359 

10 1-10 15.73 576.85 79.25 19.020 79.25 19.020 0.000 19.020 

10 11-20 15.32 576.85 77.18 18.524 77.18 18.524 0.000 18.524 

8 21-28 9.18 576.85 46.25 8.880 46.25 8.880 0.000 8.880 

10 1-10 8.69 576.85 43.78 10.508 43.78 10.508 0.000 10.508 

10 11-20 12.40 576.85 62.47 14.994 62.47 14.994 0.000 14.994 

11 21-31 11.51 576.85 57.99 15.309 57.99 15.309 0.000 15.309 

10 1-10 16.70 576.85 84.14 20.193 84.14 20.193 20.193 0.000 

10 11-20 15.66 576.85 78.90 18.935 78.90 18.935 18.935 0.000 

10 21-30 16.65 576.85 83.89 20.132 83.89 20.132 20.132 0.000 

10 1-10 18.20 576.85 91.69 22.007 91.69 22.007 22.007 0.000 

10 11-20 22.48 576.85 113.26 27.182 113.26 27.182 27.182 0.000 

11 21-31 32.04 576.85 161.42 42.615 161.42 42.615 42.615 0.000 

Energy obtained on 95% machine availibility 1298.12 1133.53 164.59 

LOAD FACTOR 46.31 60.49 17.71

Period 

Yearly 

inflow 

(M Cum) 

Annual Energy 

Generation 

(MU) 

Table 7.4 (C) 

91 

Annual 

Load Factor 

(%) 



Load Factor 

during high in 

flow period 

(%) 

Load Factor 

during lean 

inflow period 

(%) 

1976-1977 1225.29 1298.12 46.31% 60.49% 17.71% 

1977-1978 1433.84 1514.92 54.04% 70.16% 21.54% 

1978-1979 1604.36 1632.42 58.23% 75.76% 22.89% 

1979-1980 1850.80 1939.31 69.18% 83.54% 40.23% 

1980-1981 2146.05 1917.21 68.39% 83.19% 38.55% 

1981-1982 2003.69 1870.46 66.73% 83.09% 33.73% 

1982-1983 1842.30 1724.48 61.52% 78.10% 28.08% 

1983-1984 2609.99 2158.14 76.99% 91.02% 48.70% 

1984-1985 3457.01 2381.13 84.94% 95.00% 64.66% 

1985-1986 2425.01 1703.15 60.76% 75.63% 30.76% 

1986-1987 1669.94 1622.73 57.89% 74.89% 23.60% 

1987-1988 1818.92 1679.85 59.93% 77.47% 24.54% 

1988-1989 1718.13 1490.09 53.16% 69.90% 19.39% 

1989-1990 1593.34 1416.07 50.52% 68.30% 14.66% 

1990-1991 1528.25 1456.00 51.94% 70.04% 15.45% 

1991-1992 1285.68 1369.60 48.86% 67.71% 15.77% 

1992-1993 882.58 1086.76 38.77% 49.83% 16.47% 

1993-1994 1975.53 1804.64 64.38% 75.77% 41.41% 

1994-1995 1621.44 1714.69 61.17% 77.73% 27.77% 

1995-1996 1631.02 1615.03 57.61% 73.96% 24.65% 

1996-1997 1504.30 1663.80 59.35% 72.60% 32.65%

PERIOD 

Table-7.5 

92 



POWER GENERATION IN 90% DEPENDABLE YEAR 1976-77 

90% 

DEPENDABLE 

FLOW(CUMECS) 

UN 

RESTRICTED 

POWER IN MW ENERGY IN GWH MONTHLY 

ENERGY 

IN GWH 

RESTRICTED 

TO INSTALLED 

CAPACITY OF 

320MW 

UN 

RESTRICT 

ED 

RESTRICTED 

TO 

INSTALLED 

CAPACITY 

OF 320MW 

1 2 3 4 5 6 7 

1-10 48.13 242.486 242.49 58.197 58.197 

JUN 11-20 93.93 473.232 320.00 113.576 72.960 204.12 

21-30 68.15 343.349 320.00 82.404 72.960 

1-10 87.13 438.973 320.00 105.354 72.960 

JULY 11-20 83.03 418.317 320.00 100.396 72.960 226.18 

21-31 63.20 318.410 318.41 84.060 80.256 

1-10 73.67 371.160 320.00 89.078 72.960 

AUG 11-20 80.31 404.613 320.00 97.107 72.960 226.18 

21-31 85.86 432.575 320.00 114.200 80.256 

1-10 78.21 394.033 320.00 94.568 72.960 

SEP 

T 

11-20 

21-30 

45.11 

32.93 

227.270 

165.906 

227.27 

165.91 

54.545 

39.817 

54.545 

39.817 

167.32 

1-10 27.90 140.564 140.56 33.735 33.735 

OCT 11-20 22.03 110.990 110.99 26.638 26.638 89.97 

21-31 22.25 112.099 112.10 29.594 29.594 

1-10 22.12 111.444 111.44 26.746 26.746 

NOV 11-20 18.32 92.299 92.30 22.152 22.152 68.70 

21-30 16.38 82.525 82.52 19.806 19.806 

1-10 13.32 67.108 67.11 16.106 16.106 

DEC 11-20 11.39 57.384 57.38 13.772 13.772 43.87 

21-31 10.52 53.001 53.00 13.992 13.992 

1-10 9.38 47.258 47.26 11.342 11.342 

JAN 11-20 8.92 44.940 44.94 10.786 10.786 33.49 

21-31 8.54 43.026 43.03 11.359 11.359 

1-10 15.73 79.250 79.25 19.020 19.020 

FEB 11-20 15.32 77.184 77.18 18.524 18.524 46.42 

21-28 9.18 46.250 46.25 8.880 8.880 

1-10 8.69 43.781 43.78 10.508 10.508 

MAR 11-20 12.40 62.473 62.47 14.994 14.994 40.81 

21-31 11.51 57.989 57.99 15.309 15.309 

1-10 16.70 84.137 84.14 20.193 20.193 

APR 11-20 15.66 78.897 78.90 18.935 18.935 59.26 

21-30 16.65 83.885 83.89 20.132 20.132 

1-10 18.20 91.694 91.69 22.007 22.007 

MAY 11-20 22.48 113.257 113.26 27.182 27.182 91.80 

21-31 32.04 161.422 161.42 42.615 42.615 

ENERGY OBTAINED ON 95% MACHINE AVAILABILITY 1298.12

Table-7.6 

93 



INCREMENTAL BENEFIT IN 90% DEPENDABLE YEAR 1976-77 

MW MU DMU/DMW 

Load Factor 

(%) 

Annual Load 

Factor for 

additional 

capacity (%) 

250 1178.89 53.83% 25.89% 

2.21 

260 1200.97 52.73% 25.21% 

2.21 

270 1223.05 51.71% 25.21% 

2.21 

280 1245.13 50.76% 25.21% 

2.21 

290 1267.21 49.88% 25.21% 

2.21 

300 1289.29 49.06% 25.21% 

2.21 

310 1311.37 48.29% 25.21% 

2.17 

320 1333.03 47.55% 24.73% 

1.94 

330 1352.47 46.79% 22.19% 

1.94 

340 1371.91 46.06% 22.19% 

1.78 

350 1389.75 45.33% 20.37% 

1.70 

360 1406.79 44.61% 19.45% 

1.70 

370 1423.83 43.93% 19.45% 

1.49 

380 1438.75 43.22% 17.03% 

1.46 

390 1453.388 42.54% 16.71%

INCREMENTAL (DMU/DMW) 

2.60 

2.40 

2.20 

2.00 

1.80 

1.60 

1.40 

1.20 

2.21 2.21 

TEESTA-I H.E.P. 

INCREMENTAL BENEFIT FOR 90% DEPENDABLE YEAR (1976-77) 

2.21 

2.21 2.21 2.17 

2.21 

94 

1.94 

1.00 

260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 

1.94 

MW CAPACITY 

1.78 

1.70 

1.70 

1.49 

1.46 


Teesta(I) HE Project, (4 x 80 MW)

Table-7.7 (A) 

95 


Teesta(I) HE Project (4 x 80MW) 

UNRESTRICTED ENERGY GENERATION IN YEAR 1976-77 

PERIOD INFLOW HEAD POWER UNRESTRICTED 

ENERGY 

CUMEC (M) IN MW (MU) 

JUNE I 48.13 576.85 242.486 58.197 

II 93.93 576.85 473.232 113.576 

III 68.15 576.85 343.349 82.404 

JULY I 87.13 576.85 438.973 105.354 

II 83.03 576.85 418.317 100.396 

III 63.20 576.85 318.410 84.060 

AUG I 73.67 576.85 371.160 89.078 

II 80.31 576.85 404.613 97.107 

III 85.86 576.85 432.575 114.200 

SEPT I 78.21 576.85 394.033 94.568 

II 45.11 576.85 227.270 54.545 

III 32.93 576.85 165.906 39.817 

OCT I 27.90 576.85 140.564 33.735 

II 22.03 576.85 110.990 26.638 

III 22.25 576.85 112.099 29.594 

NOV I 22.12 576.85 111.444 26.746 

II 18.32 576.85 92.299 22.152 

III 16.38 576.85 82.525 19.806 

DEC I 13.32 576.85 67.108 16.106 

II 11.39 576.85 57.384 13.772 

III 10.52 576.85 53.001 13.992 

JAN I 9.38 576.85 47.258 11.342 

II 8.92 576.85 44.940 10.786 

III 8.54 576.85 43.026 11.359 

FEB I 15.73 576.85 79.250 19.020 

II 15.32 576.85 77.184 18.524 

III 9.18 576.85 46.250 8.880 

MAR I 8.69 576.85 43.781 10.508 

II 12.40 576.85 62.473 14.994 

III 11.51 576.85 57.989 15.309 

APR I 16.70 576.85 84.137 20.193 

II 15.66 576.85 78.897 18.935 

III 16.65 576.85 83.885 20.132 

MAY I 18.20 576.85 91.694 22.007 

II 22.48 576.85 113.257 27.182 

III 32.04 576.85 161.422 

Energy Obtained 

42.615 

1507.628

Table-7.7 (B) 

96 





ENERGY 

CUMEC (M) (MW) (MU) 

JUNE I 51.77 576.85 260.824 62.598 

II 91.83 576.85 462.652 111.037 

III 66.78 576.85 336.447 80.747 

JULY I 76.32 576.85 384.511 92.283 

II 89.79 576.85 452.375 108.570 

III 107.55 576.85 541.852 143.049 

AUG I 87.82 576.85 442.449 106.188 

II 73.90 576.85 372.319 89.356 

III 86.29 576.85 434.741 114.772 

SEPT I 60.26 576.85 303.598 72.864 

II 49.28 576.85 248.280 59.587 

III 41.09 576.85 207.017 49.684 

OCT I 50.15 576.85 252.663 60.639 

II 31.62 576.85 159.306 38.233 

III 25.26 576.85 127.263 33.598 

NOV I 26.19 576.85 131.949 31.668 

II 23.90 576.85 120.412 28.899 

III 18.04 576.85 90.888 21.813 

DEC I 16.31 576.85 82.172 19.721 

II 17.24 576.85 86.858 20.846 

III 19.49 576.85 98.193 25.923 

JAN I 13.40 576.85 67.511 16.203 

II 12.01 576.85 60.508 14.522 

III 12.26 576.85 61.768 16.307 

FEB I 12.41 576.85 62.523 15.006 

II 12.16 576.85 61.264 14.703 

III 11.17 576.85 56.276 10.805 

MAR I 11.30 576.85 56.931 13.663 

II 12.09 576.85 60.911 14.619 

III 13.40 576.85 67.511 17.823 

APR I 16.11 576.85 81.164 19.479 

II 20.63 576.85 103.937 24.945 

III 24.44 576.85 123.132 29.552 

MAY I 27.85 576.85 140.312 33.675 

II 57.08 576.85 287.577 69.018 

III 66.65 576.85 335.792 88.649 

ENERGY OBTAINED 1771.042

Table-7.7 (C) 

97 





ENERGY 


JUNE I 76.46 576.85 385.216 92.452 

II 80.23 576.85 404.210 97.010 

III 101.44 576.85 511.069 122.657 

JULY I 89.07 576.85 448.747 107.699 

II 95.46 576.85 480.941 115.426 

III 92.13 576.85 464.164 122.539 

AUG I 109.05 576.85 549.409 131.858 

II 92.15 576.85 464.265 111.423 

III 69.19 576.85 348.589 92.027 

SEPT I 57.39 576.85 289.139 69.393 

II 74.73 576.85 376.500 90.360 

III 56.17 576.85 282.992 67.918 

OCT I 54.03 576.85 272.211 65.331 

II 42.13 576.85 212.257 50.942 

III 35.91 576.85 180.920 47.763 

NOV I 28.78 576.85 144.998 34.799 

II 21.46 576.85 108.118 25.948 

III 21.12 576.85 106.406 25.537 

DEC I 20.37 576.85 102.627 24.630 

II 17.26 576.85 86.958 20.870 

III 15.50 576.85 78.091 20.616 

JAN I 14.30 576.85 72.045 17.291 

II 13.20 576.85 66.503 15.961 

III 12.97 576.85 65.345 17.251 

FEB I 11.81 576.85 59.500 14.280 

II 11.79 576.85 59.400 14.256 

III 12.82 576.85 64.589 12.401 

MAR I 13.15 576.85 66.252 15.900 

II 13.79 576.85 69.476 16.674 

III 16.95 576.85 85.396 22.545 

APR I 25.04 576.85 126.155 30.277 

II 24.90 576.85 125.450 30.108 

III 31.25 576.85 157.442 37.786 

MAY I 46.89 576.85 236.238 56.697 

II 59.76 576.85 301.079 72.259 

III 45.71 576.85 230.293 60.797 

ENERGY OBTAINED 

1971.684

Table-7.7 (D) 

98 





ENERGY 


JUNE I 54.47 576.85 274.427 65.863 

II 65.19 576.85 328.436 78.825 

III 93.46 576.85 470.865 113.007 

JULY I 97.06 576.85 489.002 117.360 

II 92.84 576.85 467.741 112.258 

III 104.00 576.85 523.966 138.327 

AUG I 96.11 576.85 484.216 116.212 

II 75.88 576.85 382.294 91.751 

III 80.49 576.85 405.520 107.057 

SEPT I 79.16 576.85 398.819 95.717 

II 69.09 576.85 348.085 83.540 

III 50.67 576.85 255.283 61.268 

OCT I 84.44 576.85 425.420 102.101 

II 57.62 576.85 290.298 69.671 

III 43.22 576.85 217.748 57.486 

NOV I 43.09 576.85 217.093 52.102 

II 35.08 576.85 176.738 42.417 

III 33.03 576.85 166.410 39.938 

DEC I 31.46 576.85 158.500 38.040 

II 25.92 576.85 130.589 31.341 

III 24.94 576.85 125.651 33.172 

JAN I 23.51 576.85 118.447 28.427 

II 22.64 576.85 114.063 27.375 

III 22.43 576.85 113.005 29.833 

FEB I 21.53 576.85 108.471 26.033 

II 22.57 576.85 113.711 27.291 

III 24.05 576.85 121.167 26.172 

MAR I 24.74 576.85 124.644 29.914 

II 25.38 576.85 127.868 30.688 

III 34.26 576.85 172.607 45.568 

APR I 38.48 576.85 193.868 46.528 

II 49.36 576.85 248.683 59.684 

III 56.24 576.85 283.345 68.003 

MAY I 53.63 576.85 270.195 64.847 

II 45.87 576.85 231.099 55.464 

III 48.89 576.85 246.315 65.027 


Table-7.7 (E) 

99 





ENERGY 


JUNE I 74.99 576.85 377.810 90.674 

II 99.80 576.85 502.806 120.674 

III 111.68 576.85 562.659 135.038 

JULY I 118.18 576.85 595.407 142.898 

II 120.99 576.85 609.564 146.295 

III 126.76 576.85 638.635 168.600 

AUG I 128.09 576.85 645.335 154.880 

II 140.67 576.85 708.715 170.092 

III 117.15 576.85 590.218 155.818 

SEPT I 111.92 576.85 563.869 135.328 

II 87.74 576.85 442.046 106.091 

III 71.01 576.85 357.758 85.862 

OCT I 55.55 576.85 279.869 67.168 

II 47.73 576.85 240.470 57.713 

III 44.47 576.85 224.046 59.148 

NOV I 37.57 576.85 189.283 45.428 

II 34.21 576.85 172.355 41.365 

III 31.49 576.85 158.651 38.076 

DEC I 29.25 576.85 147.366 35.368 

II 26.59 576.85 133.964 32.151 

III 24.15 576.85 121.671 32.121 

JAN I 23.26 576.85 117.187 28.125 

II 21.81 576.85 109.882 26.372 

III 21.53 576.85 108.471 28.636 

FEB I 20.02 576.85 100.864 24.207 

II 20.59 576.85 103.735 24.896 

III 24.90 576.85 125.450 24.086 

MAR I 24.62 576.85 124.039 29.769 

II 26.07 576.85 131.344 31.523 

III 30.79 576.85 155.124 40.953 

APR I 30.83 576.85 155.326 37.278 

II 39.03 576.85 196.639 47.193 

III 45.98 576.85 231.654 55.597 

MAY I 56.48 576.85 284.554 68.293 

II 61.00 576.85 307.327 73.758 

III 59.15 576.85 298.006 78.674 


Table-7.7 (F) 

100 





ENERGY 


JUNE I 65.12 576.85 328.084 78.740 

II 77.89 576.85 392.421 94.181 

III 105.73 576.85 532.682 127.844 

JULY I 135.07 576.85 680.501 163.320 

II 115.83 576.85 583.568 140.056 

III 108.95 576.85 548.905 144.911 

AUG I 106.24 576.85 535.252 128.460 

II 112.11 576.85 564.826 135.558 

III 108.98 576.85 549.056 144.951 

SEPT I 104.32 576.85 525.579 126.139 

II 89.40 576.85 450.410 108.098 

III 71.26 576.85 359.018 86.164 

OCT I 65.34 576.85 329.192 79.006 

II 60.46 576.85 304.606 73.105 

III 52.86 576.85 266.316 70.307 

NOV I 45.04 576.85 226.918 54.460 

II 35.94 576.85 181.071 43.457 

III 29.77 576.85 149.985 35.996 

DEC I 27.32 576.85 137.642 33.034 

II 24.57 576.85 123.787 29.709 

III 19.26 576.85 97.035 25.617 

JAN I 17.69 576.85 89.125 21.390 

II 19.69 576.85 99.201 23.808 

III 19.41 576.85 97.790 25.817 

FEB I 19.26 576.85 97.035 23.288 

II 20.00 576.85 100.763 24.183 

III 19.44 576.85 97.941 18.805 

MAR I 20.25 576.85 102.022 24.485 

II 22.67 576.85 114.215 27.412 

III 27.01 576.85 136.080 35.925 

APR I 33.94 576.85 170.994 41.039 

II 33.88 576.85 170.692 40.966 

III 37.57 576.85 189.283 45.428 

MAY I 47.11 576.85 237.347 56.963 

II 52.91 576.85 266.568 63.976 

III 51.40 576.85 258.960 68.366 


Table-7.7 (G) 

101 





ENERGY 


JUNE I 90.75 576.85 457.211 109.731 

II 99.95 576.85 503.562 120.855 

III 110.48 576.85 556.614 133.587 

JULY I 97.01 576.85 488.750 117.300 

II 108.68 576.85 547.545 131.411 

III 128.20 576.85 645.889 170.515 

AUG I 86.14 576.85 433.985 104.156 

II 81.55 576.85 410.860 98.606 

III 95.71 576.85 482.200 127.301 

SEPT I 73.63 576.85 370.958 89.030 

II 106.48 576.85 536.461 128.751 

III 69.86 576.85 351.964 84.471 

OCT I 49.46 576.85 249.186 59.805 

II 41.54 576.85 209.284 50.228 

III 40.00 576.85 201.526 53.203 

NOV I 31.33 576.85 157.845 37.883 

II 27.33 576.85 137.692 33.046 

III 26.46 576.85 133.309 31.994 

DEC I 23.38 576.85 117.792 28.270 

II 21.56 576.85 108.622 26.069 

III 20.40 576.85 102.778 27.133 

JAN I 20.23 576.85 101.922 24.461 

II 18.03 576.85 90.838 21.801 

III 12.63 576.85 63.632 16.799 

FEB I 11.49 576.85 57.888 13.893 

II 11.42 576.85 57.536 13.809 

III 15.89 576.85 80.056 15.371 

MAR I 17.08 576.85 86.051 20.652 

II 21.89 576.85 110.285 26.468 

III 19.74 576.85 99.453 26.256 

APR I 29.05 576.85 146.358 35.126 

II 23.75 576.85 119.656 28.717 

III 29.73 576.85 149.784 35.948 

MAY I 47.85 576.85 241.075 57.858 

II 57.33 576.85 288.837 69.321 

III 76.29 576.85 384.360 101.471 


Table-7.7 (H) 

102 





ENERGY 


JUNE I 95.93 576.85 483.309 115.994 

II 93.09 576.85 469.000 112.560 

III 129.92 576.85 654.555 157.093 

JULY I 148.79 576.85 749.625 179.910 

II 126.58 576.85 637.728 153.055 

III 125.58 576.85 632.690 167.030 

AUG I 102.79 576.85 517.870 124.289 

II 109.00 576.85 549.157 131.798 

III 127.33 576.85 641.506 169.358 

SEPT I 102.35 576.85 515.654 123.757 

II 115.07 576.85 579.739 139.137 

III 132.74 576.85 668.763 160.503 

OCT I 93.34 576.85 470.260 112.862 

II 92.01 576.85 463.559 111.254 

III 62.72 576.85 315.992 83.422 

NOV I 51.28 576.85 258.356 62.005 

II 47.11 576.85 237.347 56.963 

III 38.80 576.85 195.480 46.915 

DEC I 32.37 576.85 163.085 39.140 

II 30.34 576.85 152.857 36.686 

III 27.20 576.85 137.037 36.178 

JAN I 24.27 576.85 122.276 29.346 

II 23.88 576.85 120.311 28.875 

III 21.26 576.85 107.111 28.277 

FEB I 20.48 576.85 103.181 24.763 

II 21.27 576.85 107.161 25.719 

III 20.43 576.85 102.929 22.233 

MAR I 45.11 576.85 227.270 54.545 

II 50.41 576.85 253.973 60.953 

III 49.53 576.85 249.539 65.878 

APR I 52.07 576.85 262.336 62.961 

II 55.50 576.85 279.617 67.108 

III 55.52 576.85 279.717 67.132 

MAY I 63.01 576.85 317.453 76.189 

II 92.08 576.85 463.912 111.339 

III 130.83 576.85 659.140 174.013 


Table-7.7 (I) 

103 





ENERGY 


JUNE I 135.94 576.85 684.885 164.372 

II 163.47 576.85 823.585 197.660 

III 146.81 576.85 739.649 177.516 

JULY I 168.97 576.85 851.294 204.311 

II 169.53 576.85 854.116 204.988 

III 179.23 576.85 902.986 238.388 

AUG I 161.62 576.85 814.264 195.423 

II 162.06 576.85 816.481 195.955 

III 169.66 576.85 854.771 225.659 

SEPT I 174.74 576.85 880.364 211.287 

II 166.75 576.85 840.110 201.626 

III 132.28 576.85 666.445 159.947 

OCT I 111.42 576.85 561.349 134.724 

II 141.33 576.85 712.040 170.890 

III 108.88 576.85 548.553 144.818 

NOV I 81.15 576.85 408.845 98.123 

II 70.12 576.85 353.274 84.786 

III 62.33 576.85 314.027 75.367 

DEC I 39.96 576.85 201.324 48.318 

II 39.31 576.85 198.049 47.532 

III 39.47 576.85 198.855 52.498 

JAN I 39.81 576.85 200.568 48.136 

II 37.81 576.85 190.492 45.718 

III 32.73 576.85 164.898 43.533 

FEB I 35.77 576.85 180.214 43.251 

II 32.70 576.85 164.747 39.539 

III 39.58 576.85 199.410 38.287 

MAR I 50.28 576.85 253.318 60.796 

II 54.46 576.85 274.377 65.850 

III 50.71 576.85 255.484 67.448 

APR I 61.04 576.85 307.528 73.807 

II 73.66 576.85 371.109 89.066 

III 86.99 576.85 438.268 105.184 

MAY I 62.60 576.85 315.388 75.693 

II 72.65 576.85 366.021 87.845 

III 101.19 576.85 509.809 134.590 


Table-7.7 (J) 

104 





ENERGY 


JUNE I 64.93 576.85 327.126 78.510 

II 81.06 576.85 408.392 98.014 

III 229.69 576.85 1157.210 277.730 

JULY I 181.10 576.85 912.407 218.978 

II 236.33 576.85 1190.663 285.759 

III 198.71 576.85 1001.129 264.298 

AUG I 160.58 576.85 809.024 194.166 

II 169.39 576.85 853.410 204.819 

III 207.38 576.85 1044.809 275.830 

SEPT I 84.58 576.85 426.126 102.270 

II 80.80 576.85 407.082 97.700 

III 67.71 576.85 341.132 81.872 

OCT I 58.19 576.85 293.169 70.361 

II 51.01 576.85 256.995 61.679 

III 42.03 576.85 211.753 55.903 

NOV I 34.11 576.85 171.851 41.244 

II 29.65 576.85 149.381 35.851 

III 26.27 576.85 132.352 31.764 

DEC I 22.37 576.85 112.703 27.049 

II 20.23 576.85 101.922 24.461 

III 18.61 576.85 93.760 24.753 

JAN I 17.65 576.85 88.923 21.342 

II 17.56 576.85 88.470 21.233 

III 16.62 576.85 83.734 22.106 

FEB I 16.79 576.85 84.590 20.302 

II 17.27 576.85 87.009 20.882 

III 19.78 576.85 99.654 19.134 

MAR I 21.08 576.85 106.204 25.489 

II 22.94 576.85 115.575 27.738 

III 23.56 576.85 118.699 31.336 

APR I 23.17 576.85 116.734 28.016 

II 29.96 576.85 150.943 36.226 

III 33.60 576.85 169.281 40.628 

MAY I 31.50 576.85 158.701 38.088 

II 33.50 576.85 168.778 40.507 

III 35.30 576.85 177.846 46.951 


Table-7.7 (K) 

105 





ENERGY 


JUNE I 42.90 576.85 216.136 51.873 

II 72.77 576.85 366.625 87.990 

III 107.84 576.85 543.313 130.395 

JULY I 93.39 576.85 470.512 112.923 

II 116.69 576.85 587.900 141.096 

III 104.96 576.85 528.803 139.604 

AUG I 93.15 576.85 469.303 112.633 

II 80.07 576.85 403.404 96.817 

III 88.65 576.85 446.631 117.911 

SEPT I 77.83 576.85 392.118 94.108 

II 96.67 576.85 487.037 116.889 

III 78.69 576.85 396.451 95.148 

OCT I 63.46 576.85 319.720 76.733 

II 47.46 576.85 239.110 57.386 

III 37.05 576.85 186.663 49.279 

NOV I 34.07 576.85 171.649 41.196 

II 30.31 576.85 152.706 36.649 

III 26.18 576.85 131.898 31.656 

DEC I 23.43 576.85 118.044 28.330 

II 21.58 576.85 108.723 26.094 

III 15.91 576.85 80.157 21.161 

JAN I 13.89 576.85 69.980 16.795 

II 13.08 576.85 65.899 15.816 

III 12.26 576.85 61.768 16.307 

FEB I 11.62 576.85 58.543 14.050 

II 11.52 576.85 58.039 13.929 

III 12.63 576.85 63.632 12.217 

MAR I 11.81 576.85 59.500 14.280 

II 14.01 576.85 70.584 16.940 

III 17.59 576.85 88.621 23.396 

APR I 32.07 576.85 161.573 38.778 

II 22.40 576.85 112.854 27.085 

III 29.60 576.85 149.129 35.791 

MAY I 33.47 576.85 168.627 40.470 

II 37.24 576.85 187.620 45.029 

III 43.69 576.85 220.116 58.111 


Table-7.7 (L) 

106 





ENERGY 


JUNE I 72.49 576.85 365.215 87.652 

II 105.28 576.85 530.415 127.300 

III 88.36 576.85 445.170 106.841 

JULY I 101.38 576.85 510.767 122.584 

II 96.91 576.85 488.246 117.179 

III 108.36 576.85 545.933 144.126 

AUG I 102.61 576.85 516.963 124.071 

II 111.94 576.85 563.969 135.353 

III 74.82 576.85 376.954 99.516 

SEPT I 134.61 576.85 678.184 162.764 

II 72.01 576.85 362.796 87.071 

III 98.76 576.85 497.567 119.416 

OCT I 61.32 576.85 308.939 74.145 

II 45.68 576.85 230.142 55.234 

III 39.05 576.85 196.739 51.939 

NOV I 31.70 576.85 159.709 38.330 

II 19.34 576.85 97.438 23.385 

III 16.99 576.85 85.598 20.544 

DEC I 16.03 576.85 80.761 19.383 

II 14.66 576.85 73.859 17.726 

III 13.41 576.85 67.561 17.836 

JAN I 13.08 576.85 65.899 15.816 

II 13.08 576.85 65.899 15.816 

III 12.92 576.85 65.093 17.184 

FEB I 12.68 576.85 63.884 15.332 

II 13.27 576.85 66.856 16.045 

III 14.75 576.85 74.313 16.052 

MAR I 15.30 576.85 77.084 18.500 

II 22.66 576.85 114.164 27.399 

III 23.30 576.85 117.389 30.991 

APR I 26.64 576.85 134.216 32.212 

II 30.09 576.85 151.598 36.383 

III 35.00 576.85 176.335 42.320 

MAY I 35.79 576.85 180.315 43.276 

II 53.61 576.85 270.095 64.823 

III 71.04 576.85 357.909 94.488 


Table-7.7 (M) 

107 





ENERGY 


JUNE I 57.30 576.85 288.685 69.284 

II 82.91 576.85 417.712 100.251 

III 90.82 576.85 457.564 109.815 

JULY I 141.14 576.85 711.083 170.660 

II 110.87 576.85 558.579 134.059 

III 122.19 576.85 615.610 162.521 

AUG I 121.26 576.85 610.925 146.622 

II 111.30 576.85 560.745 134.579 

III 168.87 576.85 850.791 224.609 

SEPT I 80.63 576.85 406.225 97.494 

II 54.38 576.85 273.974 65.754 

III 60.82 576.85 306.420 73.541 

OCT I 51.35 576.85 258.708 62.090 

II 34.07 576.85 171.649 41.196 

III 27.41 576.85 138.095 36.457 

NOV I 22.60 576.85 113.862 27.327 

II 20.40 576.85 102.778 24.667 

III 19.01 576.85 95.775 22.986 

DEC I 18.05 576.85 90.938 21.825 

II 17.12 576.85 86.253 20.701 

III 16.20 576.85 81.618 21.547 

JAN I 9.92 576.85 49.978 11.995 

II 9.65 576.85 48.618 11.668 

III 9.57 576.85 48.215 12.729 

FEB I 10.63 576.85 53.555 12.853 

II 9.72 576.85 48.971 11.753 

III 10.35 576.85 52.145 10.012 

MAR I 11.76 576.85 59.249 14.220 

II 11.99 576.85 60.407 14.498 

III 12.32 576.85 62.070 16.386 

APR I 12.80 576.85 64.488 15.477 

II 15.34 576.85 77.285 18.548 

III 18.40 576.85 92.702 22.248 

MAY I 32.31 576.85 162.782 39.068 

II 33.37 576.85 168.123 40.349 

III 81.30 576.85 409.601 108.135 


Table-7.7 (N) 

108 





ENERGY 


JUNE I 72.18 576.85 363.653 87.277 

II 119.57 576.85 602.410 144.578 

III 126.45 576.85 637.073 152.897 

JULY I 128.75 576.85 648.660 155.679 

II 126.64 576.85 638.030 153.127 

III 117.89 576.85 593.946 156.802 

AUG I 102.30 576.85 515.402 123.696 

II 80.26 576.85 404.361 97.047 

III 78.74 576.85 396.703 104.730 

SEPT I 76.32 576.85 384.511 92.283 

II 69.13 576.85 348.287 83.589 

III 68.68 576.85 346.019 83.045 

OCT I 54.25 576.85 273.319 65.597 

II 46.17 576.85 232.611 55.827 

III 37.55 576.85 189.182 49.944 

NOV I 23.36 576.85 117.691 28.246 

II 18.95 576.85 95.473 22.913 

III 17.24 576.85 86.858 20.846 

DEC I 15.04 576.85 75.774 18.186 

II 13.04 576.85 65.697 15.767 

III 11.42 576.85 57.536 15.189 

JAN I 10.41 576.85 52.447 12.587 

II 9.65 576.85 48.618 11.668 

III 8.74 576.85 44.033 11.625 

FEB I 8.60 576.85 43.328 10.399 

II 8.07 576.85 40.658 9.758 

III 7.80 576.85 39.297 7.545 

MAR I 7.13 576.85 35.922 8.621 

II 5.82 576.85 29.322 7.037 

III 5.92 576.85 29.826 7.874 

APR I 6.12 576.85 30.833 7.400 

II 10.11 576.85 50.936 12.225 

III 12.53 576.85 63.128 15.151 

MAY I 18.48 576.85 93.105 22.345 

II 32.56 576.85 164.042 39.370 

III 37.47 576.85 188.779 49.838 


Table-7.7 (O) 

109 





ENERGY 


JUNE I 79.11 576.85 398.567 95.656 

II 77.28 576.85 389.347 93.443 

III 90.37 576.85 455.297 109.271 

JULY I 99.60 576.85 501.799 120.432 

II 126.97 576.85 639.693 153.526 

III 108.67 576.85 547.495 144.539 

AUG I 92.56 576.85 466.330 111.919 

II 94.03 576.85 473.736 113.697 

III 83.45 576.85 420.433 110.994 

SEPT I 80.09 576.85 403.505 96.841 

II 76.69 576.85 386.375 92.730 

III 53.40 576.85 269.037 64.569 

OCT I 44.75 576.85 225.457 54.110 

II 45.59 576.85 229.689 55.125 

III 37.50 576.85 188.930 49.878 

NOV I 22.96 576.85 115.676 27.762 

II 17.15 576.85 86.404 20.737 

III 14.33 576.85 72.197 17.327 

DEC I 13.12 576.85 66.100 15.864 

II 10.82 576.85 54.513 13.083 

III 9.33 576.85 47.006 12.410 

JAN I 9.45 576.85 47.610 11.427 

II 9.27 576.85 46.704 11.209 

III 9.17 576.85 46.200 12.197 

FEB I 8.88 576.85 44.739 10.737 

II 8.44 576.85 42.522 10.205 

III 8.54 576.85 43.026 8.261 

MAR I 9.11 576.85 45.897 11.015 

II 10.39 576.85 52.346 12.563 

III 10.95 576.85 55.168 14.564 

APR I 28.74 576.85 144.796 34.751 

II 16.38 576.85 82.525 19.806 

III 17.34 576.85 87.361 20.967 

MAY I 29.11 576.85 146.660 35.198 

II 35.47 576.85 178.703 42.889 

III 39.24 576.85 197.697 52.192 


Table-7.7 (P) 

110 





ENERGY 


JUNE I 42.00 576.85 211.602 50.784 

II 66.32 576.85 334.129 80.191 

III 60.98 576.85 307.226 73.734 

JULY I 69.65 576.85 350.906 84.218 

II 67.86 576.85 341.888 82.053 

III 73.97 576.85 372.671 98.385 

AUG I 84.81 576.85 427.285 102.548 

II 97.71 576.85 492.277 118.146 

III 80.74 576.85 406.779 107.390 

SEPT I 81.34 576.85 409.802 98.353 

II 85.93 576.85 432.927 103.903 

III 66.57 576.85 335.389 80.493 

OCT I 53.14 576.85 267.727 64.254 

II 42.13 576.85 212.257 50.942 

III 34.58 576.85 174.219 45.994 

NOV I 28.66 576.85 144.393 34.654 

II 25.34 576.85 127.666 30.640 

III 19.33 576.85 97.387 23.373 

DEC I 16.25 576.85 81.870 19.649 

II 12.46 576.85 62.775 15.066 

III 10.97 576.85 55.268 14.591 

JAN I 9.97 576.85 50.230 12.055 

II 8.28 576.85 41.716 10.012 

III 8.46 576.85 42.623 11.252 

FEB I 8.95 576.85 45.091 10.822 

II 8.62 576.85 43.429 10.423 

III 8.27 576.85 41.665 9.000 

MAR I 8.86 576.85 44.638 10.713 

II 8.92 576.85 44.940 10.786 

III 9.17 576.85 46.200 12.197 

APR I 10.83 576.85 54.563 13.095 

II 15.22 576.85 76.680 18.403 

III 13.91 576.85 70.081 16.819 

MAY I 13.64 576.85 68.720 16.493 

II 15.88 576.85 80.006 19.201 

III 15.96 576.85 80.409 21.228 


Table-7.7 (Q) 

111 





ENERGY 


JUNE I 17.63 576.85 88.822 21.317 

II 25.13 576.85 126.608 30.386 

III 48.70 576.85 245.357 58.886 

JULY I 41.84 576.85 210.796 50.591 

II 42.33 576.85 213.264 51.183 

III 48.10 576.85 242.335 63.976 

AUG I 52.64 576.85 265.208 63.650 

II 52.86 576.85 266.316 63.916 

III 57.45 576.85 289.441 76.412 

SEPT I 50.40 576.85 253.922 60.941 

II 49.61 576.85 249.942 59.986 

III 41.07 576.85 206.916 49.660 

OCT I 31.01 576.85 156.233 37.496 

II 22.25 576.85 112.099 26.904 

III 18.92 576.85 95.322 25.165 

NOV I 13.98 576.85 70.433 16.904 

II 12.43 576.85 62.624 15.030 

III 11.32 576.85 57.032 13.688 

DEC I 11.20 576.85 56.427 13.543 

II 9.69 576.85 48.820 11.717 

III 8.95 576.85 45.091 11.904 

JAN I 9.10 576.85 45.847 11.003 

II 9.18 576.85 46.250 11.100 

III 8.61 576.85 43.378 11.452 

FEB I 8.34 576.85 42.018 10.084 

II 8.86 576.85 44.638 10.713 

III 8.56 576.85 43.126 8.280 

MAR I 13.99 576.85 70.484 16.916 

II 13.96 576.85 70.332 16.880 

III 14.62 576.85 73.658 19.446 

APR I 14.85 576.85 74.816 17.956 

II 16.23 576.85 81.769 19.625 

III 19.43 576.85 97.891 23.494 

MAY I 24.66 576.85 124.241 29.818 

II 22.20 576.85 111.847 26.843 

III 22.48 576.85 113.257 29.900 


Table-7.7 (R) 

112 





ENERGY 


JUNE I 28.86 576.85 145.401 34.896 

II 36.87 576.85 185.756 44.581 

III 47.43 576.85 238.959 57.350 

JULY I 99.34 576.85 500.489 120.117 

II 99.33 576.85 500.438 120.105 

III 116.50 576.85 586.943 154.953 

AUG I 130.65 576.85 658.233 157.976 

II 123.86 576.85 624.024 149.766 

III 118.63 576.85 597.674 157.786 

SEPT I 124.81 576.85 628.810 150.914 

II 105.12 576.85 529.609 127.106 

III 99.38 576.85 500.690 120.166 

OCT I 88.33 576.85 445.019 106.805 

II 65.54 576.85 330.200 79.248 

III 56.17 576.85 282.992 74.710 

NOV I 46.60 576.85 234.777 56.347 

II 41.07 576.85 206.916 49.660 

III 37.66 576.85 189.736 45.537 

DEC I 36.75 576.85 185.152 44.436 

II 33.77 576.85 170.138 40.833 

III 27.75 576.85 139.808 36.909 

JAN I 26.13 576.85 131.647 31.595 

II 24.34 576.85 122.628 29.431 

III 24.59 576.85 123.888 32.706 

FEB I 24.25 576.85 122.175 29.322 

II 23.19 576.85 116.834 28.040 

III 24.86 576.85 125.248 24.048 

MAR I 22.90 576.85 115.373 27.690 

II 20.67 576.85 104.138 24.993 

III 26.14 576.85 131.697 34.768 

APR I 25.38 576.85 127.868 30.688 

II 31.77 576.85 160.062 38.415 

III 29.15 576.85 146.862 35.247 

MAY I 32.66 576.85 164.546 39.491 

II 33.67 576.85 169.634 40.712 

III 41.41 576.85 208.629 55.078 


Table-7.7 (S) 

113 





ENERGY 


JUNE I 59.79 576.85 301.230 72.295 

II 79.15 576.85 398.769 95.704 

III 91.87 576.85 462.854 111.085 

JULY I 78.56 576.85 395.796 94.991 

II 83.30 576.85 419.677 100.722 

III 84.88 576.85 427.637 112.896 

AUG I 78.02 576.85 393.076 94.338 

II 76.20 576.85 383.906 92.137 

III 81.94 576.85 412.825 108.986 

SEPT I 69.51 576.85 350.201 84.048 

II 69.61 576.85 350.705 84.169 

III 60.16 576.85 303.094 72.743 

OCT I 47.04 576.85 236.994 56.879 

II 41.83 576.85 210.745 50.579 

III 38.30 576.85 192.961 50.942 

NOV I 31.52 576.85 158.802 38.113 

II 25.98 576.85 130.891 31.414 

III 21.71 576.85 109.378 26.251 

DEC I 20.94 576.85 105.499 25.320 

II 19.16 576.85 96.531 23.167 

III 18.12 576.85 91.291 24.101 

JAN I 17.17 576.85 86.505 20.761 

II 17.36 576.85 87.462 20.991 

III 17.15 576.85 86.404 22.811 

FEB I 17.01 576.85 85.699 20.568 

II 16.95 576.85 85.396 20.495 

III 17.04 576.85 85.850 16.483 

MAR I 15.49 576.85 78.041 18.730 

II 14.69 576.85 74.010 17.762 

III 20.23 576.85 101.922 26.907 

APR I 19.79 576.85 99.705 23.929 

II 24.52 576.85 123.535 29.648 

III 35.79 576.85 180.315 43.276 

MAY I 52.20 576.85 262.991 63.118 

II 80.59 576.85 406.024 97.446 

III 77.87 576.85 392.320 103.572 


Table-7.7 (T) 

114 





ENERGY 


JUNE I 90.43 576.85 455.599 109.344 

II 96.71 576.85 487.238 116.937 

III 97.97 576.85 493.587 118.461 

JULY I 124.33 576.85 626.392 150.334 

II 104.29 576.85 525.428 126.103 

III 80.17 576.85 403.908 106.632 

AUG I 87.59 576.85 441.291 105.910 

II 88.38 576.85 445.271 106.865 

III 78.51 576.85 395.544 104.424 

SEPT I 70.82 576.85 356.801 85.632 

II 63.42 576.85 319.519 76.685 

III 61.02 576.85 307.427 73.783 

OCT I 45.07 576.85 227.069 54.497 

II 43.88 576.85 221.074 53.058 

III 34.28 576.85 172.707 45.595 

NOV I 22.29 576.85 112.300 26.952 

II 25.46 576.85 128.271 30.785 

III 25.60 576.85 128.976 30.954 

DEC I 19.16 576.85 96.531 23.167 

II 17.05 576.85 85.900 20.616 

III 15.84 576.85 79.804 21.068 

JAN I 13.65 576.85 68.771 16.505 

II 13.57 576.85 68.368 16.408 

III 14.35 576.85 72.297 19.086 

FEB I 14.85 576.85 74.816 17.956 

II 13.22 576.85 66.604 15.985 

III 14.48 576.85 72.952 15.758 

MAR I 14.70 576.85 74.061 17.775 

II 17.02 576.85 85.749 20.580 

III 18.14 576.85 91.392 24.127 

APR I 16.69 576.85 84.087 20.181 

II 16.21 576.85 81.668 19.600 

III 36.06 576.85 181.675 43.602 

MAY I 43.95 576.85 221.426 53.142 

II 38.53 576.85 194.120 46.589 

III 53.33 576.85 268.684 70.933 


Table-7.7 (U) 

115 





ENERGY 


JUNE I 50.02 576.85 252.008 60.482 

II 42.35 576.85 213.365 51.208 

III 75.65 576.85 381.135 91.472 

JULY I 84.06 576.85 423.506 101.641 

II 90.50 576.85 455.952 109.428 

III 80.56 576.85 405.873 107.150 

AUG I 77.01 576.85 387.987 93.117 

II 71.81 576.85 361.789 86.829 

III 72.38 576.85 364.661 96.270 

SEPT I 72.25 576.85 364.006 87.361 

II 68.95 576.85 347.380 83.371 

III 59.97 576.85 302.137 72.513 

OCT I 52.72 576.85 265.611 63.747 

II 48.32 576.85 243.443 58.426 

III 43.19 576.85 217.597 57.446 

NOV I 39.29 576.85 197.948 47.508 

II 36.53 576.85 184.043 44.170 

III 32.49 576.85 163.689 39.285 

DEC I 22.37 576.85 112.703 27.049 

II 20.23 576.85 101.922 24.461 

III 18.61 576.85 93.760 24.753 

JAN I 21.06 576.85 106.103 25.465 

II 20.03 576.85 100.914 24.219 

III 20.35 576.85 102.526 27.067 

FEB I 20.32 576.85 102.375 24.570 

II 20.25 576.85 102.022 24.485 

III 20.01 576.85 100.813 19.356 

MAR I 20.50 576.85 103.282 24.788 

II 21.51 576.85 108.370 26.009 

III 23.46 576.85 118.195 31.203 

APR I 22.50 576.85 113.358 27.206 

II 22.37 576.85 112.703 27.049 

III 23.02 576.85 115.978 27.835 

MAY I 26.86 576.85 135.324 32.478 

II 30.89 576.85 155.628 37.351 

III 31.91 576.85 160.767 42.442 




CHAPTER – VIII 

POWER EVACUATION

8.1 GENERAL 

CHAPTER-VIII 

POWER EVACUATION 

116 



This chapter contains data regarding existing Power network of the Eastern region and 

the power evacuation arrangement required, consequent upon power generation at the 

proposed Teesta I Hydro Electric Project. 

8.2 APPRAISAL OF EXISTING POWER EVACUATION FACILITIES 

The nearest pooling point being proposed is a new 400/220 KV substation at Siliguri 

(New Jalpaiguri) where power from Tala H.E.P and Teesta stages is expected to be 

pooled. Adjoining to this is also a new substation of 220/132 KV level being created 

by WBSEB. Hence power evacuation with respect to development of national grid and 

consumption by the state can be considered as assured for the present project. 

Underlying 220/132 KV 200 MVA PGCIL and 132 KV network in the entire area is 

available to cater for local loads. 

8.3 PROPOSED EVACUATION ARRANGEMENT TO THE NEAREST 

FACILITY 

After study of existing power evacuation facilities, it emerges that evacuation of 

power generated at Teesta I Hydro Electric Project can be done through one no. 400 

kV double circuit line to be connected at the pooling point which can be assumed to 

come up near Teesta I H.E.P (2 km from Teesta –I H E Project). The length of this 400 

kV double circuit line would be approximately 2 km.



CHAPTER – IX 

ENVIRONMENTAL ASPECTS


9.1.1 General 

CHAPTER - IX 

ENVIRONMENTAL ASPECTS 

117 



Teesta (I )H.E. scheme is one of the various projects proposed in Teesta river basin in 

Sikkim (Fig 9.1). The proposed project envisages construction of two dams, i.e. Dam-I is 

to be located about 200 m downstream of confluence of Lhonak Chhu with Zemu Chhu 

and Dam-II is to be located aout 500 m downstream to the confluence between Chento 

Chhu and river Teesta in the North district of Sikkim (Fig. 9.2). 

The project involves construction of 40 m high dam-I (above river-bed level) and 

diversion of water through a 3.5 km long tunnel. The water from the 40 m high dam-II 

(above river-bed level) is proposed to be diverted through a 3.5 km long headrace tunnel 

(Fig. 9.2). An underground powerhouse is proposed immediately upstream of Zema on 

the right bank of Teesta River. 

9.1.2 Location 

Sikkim is a small hilly State in the Eastern Himalayas, extending approximately 114 

Kms from north to south and 64Kms from east to west, surrounded by vast stretches of 

Tibetan Plateau in the North, Chumbi Valley of Tibet and the Kingdom of Bhutan in 

the east, Darjeeling district of West Bengal in the south and the Kingdom of Nepal in 

the west. The State, being a part of inner ranges of the Himalaya, has no open valley. 

The elevations ranging from 300 to 8583 meters above mean sea level consisting of 

lower, middle and higher hills, alpine zones and snow bound area. 

The nearest railhead is New Jalpaiguri and the nearest airport is Bagdogra. The 

location details are given below:

9.2 PHYSICAL ENVIRONMENT 

9.2.1 Climate/Meteorology 

Town : Lachen 

Revenue Block : Lachen 

Sub-division : Chungthang 

District : North Sikkim 

State : Sikkim 

118 



The climate of the State has been roughly divided into tropical, temperate and alpine 

zones. Generally the lowlands are hot and humid, the hills are temperate and the 

mountain peaks are permanently covered with snow. For most of the period in the 

year, the climate is cold and humid. A peculiar feature of the State is that it 

experiences a cold winter from end of November to February and monsoons 

throughout the year with a little respite during May - June and October - November. 

Even the winter months can be very wet and damp with unpredictable showers. The 

area experiences heavy rainfall due to its proximity to the Bay of Bengal. The general 

trend of decrease in temperature with increase in altitude holds good everywhere. 

The mean temperature in the lower altitudinal zone varies from 1.5° C to 9.5° C. 

Temperature varies with altitude and slope. The maximum temperature is recorded 

usually during July and August and minimum during December & January. Fog is a 

common feature in the entire State from May to September. 

Rainfall is heavy and well distributed during the months from May to early October. 

July is the wettest month in most of the places. The intensity of rainfall during South- 

West monsoon season decreases from south to north, while the distribution of winter 

rainfall is in the opposite order. The highest annual rainfall for the individual station 

may exceed 5000 mm and average number of rainy days (days with rain of 2.5 mm or 

more) ranges from 100 at Thangu to 184 at Gangtok.

9.2.2 Topography 

119 



Sikkim encompasses the Lesser Himalaya, Central Himalaya, and the Tethys 

Himalaya. It is essentially a mountainous State without flat piece of land of any extent 

anywhere. The mountains rise in elevation northward. The northern portion of the 

State is deeply cut into steep escarpments. South Sikkim is lower, more open, and 

fairly well cultivated. This configuration of the State is partly due to the direction of 

the main drainage, which is towards the south. The trend of the mountain system is 

generally in east-west direction. The Rangit and the Teesta, which form the main 

channels of drainage, run nearly north south. The valleys cut by these rivers and their 

feeders are very deep and are rather open towards the top, but usually attain a steep 

gorge like structure as they approach the bed of the rivers. 

9.2.3 Soils 

The State of Sikkim enjoys a wide range of climate, physiography, geology and 

vegetation which have further influenced formation of different kinds of soils that are 

classified under 5 broad physiographic units. Table 9.1 gives area wise details of this 

soil. The light textured soil and rocky areas are prone to sliding. Topsoil in most area 

is rich in humus and organic matter. The water holding capacity in most area is low 

and has low cohesiveness. The soil in general is loamy sand to silty clay loam with a 

depth of 30 cm to 100 cm and in some cases even more than 120 cm. 

Table 9.1: Major physiographic units of soil in Sikkim 

No. Physiographic units Area (ha) % of total geographic area 

1 Summit & Ridge (>30%) 31459.45 4.43 

2 

2.1 

2.2 

2.3 

2.4 

Slide slope of hills 

Very steep slope (>50%) 

Escarpments (>50%) 

Steeply sloping (30-50%) 

Moderately sloping (15-30%) 

213100.01 

30480.73 

214641.28 

16024.82 

30.03 

4.3 

30.24 

2.26

120 



3 Valleys (

121 



The area falls within axial belt of Central Crystalline Zone of the North Sikkim 

Himalayas where the rock types are mainly high grade gneisses having inter-bands of 

meta-sedimentaries represented by calc-silicate/quartzite, high-grade schist and their 

fine inter laminations. The meta-sedimentaies occur as enclaves in the high-grade 

gneisses in the area around the proposed project. Discordant tourmaline bearing 

quartz veins and pegmatite often intrudes all these rock types. 

9.2.5 Seismicity 

Sikkim is a part of active Himalayan belt, which is tectonically young. The area has 

experienced mild tremors in the recent past. The project area falls in Zone IV of 

Seismic Zoning Map of India as per IS 1893 - 1984. 

9.2.6 Catchment Area 

The catchment areas of dam I and II up to the proposed dam sites are approximately 

881 sq km and 600 sq. km respectively. The catchment is mountainous with rugged 

terrain in its upper reaches. Steep longitudinal hill ranges and valley with topographic 

highs is a typical feature of the area. The tributaries are angular and have dendritic 

drainage patterns. Streams have moderate to steep slopes in upper reaches. The natural 

vegetation ranges from mixed evergreen to deciduous. 

9.2.7 River System & Drainage Pattern 

Zemu Chhu on which the proposed dam-I of the scheme is located rises from Zemu 

glacier (6800 m) and a number of other glaciers like Lhonak glacier complex, East 

Longpo glacier, Chanson glacier and Khorakhang glacier. Zemu glacier is drained by 

Poke chhu, which is joined by Thomphyak chhu after traversing a distance of more than 

6 km from the snout of the glacier. After the confluence of Thomphyak chhu, Poke chhu 

is joined downstream by Lhonak chhu at a distance of about 4 km. Lhonak chhu rises 

from the Lhonak glacier complex in the north-west and Khorakhang glacier in the north.

122 



Lhonak glacier complex is drained by Goma chhu, which is joined by Lungma chhu 

before meeting Khora chhu that rises from the Khorakhang glacier (Fig.3). The streams 

from these glaciers meet Naku chhu to form Langbo chhu, which flows down as Lhonak 

chhu and meets Poke chhu to form Zemu chhu. The total river length of Lhonak chhu 

from its origins to the proposed dam site (dam-I) is about 37.8 km. 

Teesta river on which dam-II is located rises from a number of sources including Teesta 

Khangse glacier, Lhamo chho (lake), Gurudongmar chho (lake) which form Chhombo 

chhu constituting the headwaters of the river. Small minor and major tributaries like 

Lasha chhu, Kalep chhu and Chento chhu, all left bank tributaries, meet Teesta river 

upstream of the proposed dam site (dam-II) (Fig.3). Teesta river flows for about 40 km 

from its origins up to the proposed dam site (dam-II). 

9.2.8 Submergence 

The project envisages construction of two dams, each 40 m high from the riverbed 

level. The reservoir of dam-I would result in inundation of 43.75 ha of land whereas 

dam-II is likely to submerge only 19.57 ha of land. Therefore, Teesta Stage-I H.E. 

project would inundate 63.32 ha of land, which is mostly under dense forest and alpine 

scrub. The spread of the two reservoirs is indicated in Figure 9.8. The predominant 

landuse in the submergence area of dam-I is alpine open scrub forest (45%) and dense 

mixed forest (45%) and the rest of the area is characterized by rockyland, moraines 

and degraded forests. The area likely to be submerged by dam-II reservoir is 

comprised only of dense mixed forests (89%), rockyland (9%), alpine scrub (1%) and 

about 1% waterbody/ river. The proposed project, however, does not involve 

inundation of any village or human habitation. 

9.2.9 Landuse pattern (including land requirement of the project) 

The landuse/landcover pattern within the 7 km radius of the proposed Teesta Stage-I

123 



H.E. project was interpreted and generated from LISS-III scene of Path/Row 107/051 

of 19th January, 2000 and PAN D scene of Path/Row 107/051 of 13th January, 2002. 

LISS and PANscenes of area covering 7 km radius of the project site are given in 

Figures 9.4 & 9.5. The first level classified landuse/landcover map generated from 

these two scenes coupled with ground truthing is given in Figure 9.6. Area covered by 

various landuse/lancover categories is given in Table 9.2 and the percent 

representation of each of the landuse/landcover type is shown in Figure 9.7. Analysis 

and field studies show that the catchment area around 7 km radius of both the dams is 

a typically high altitude Himalayan zone with predominant alpine vegetation. The 

predominant landuse of the area is a mixture of forests, alpine scrub, rockyland, 

moraines, snow and ice cover. The dense mixed forests, which occupy the lower 

altitudes of the catchment along river slopes, constitute about 25% of the land area 

while alpine open scrubs constitute 18% of the total land area. Rockylands and 

rockfall areas in the catchment constitute an important landuse/landcover of the area 

covering about 7785 ha (15%) of the land. Similarly, large areas in the catchment are 

either under permanent ice cover/glaciers (12%) or snow cover (16%). Notably there 

is little part of catchment under settlements/ agriculture. The area has sparse human 

habitation sites, which are restricted to areas downstream of the proposed powerhouse 

site. The dense forests are present all along Zemu chhu as well as Teesta river towards 

upstream and downstream areas and the proposed dam sites are located within these 

dense forest areas. The forests towards west of dam-I are represented by Zema 

Reserve Forest mostly along left bank of Lhonak chhu and on both the banks of Poke 

chhu. The forests in the south are represented by Pangnal Reserve Forest on both the 

banks of Teesta river. These are mostly coniferous forests with predominant growth of 

Abies densa and occasional representation of Larix griffithii mixed with the former. 

The areas above these dense mixed forests are represented by alpine/open scrub type 

of vegetation.

124 



Table 9.2: Area (ha) under different landuse/landcover categories in 7 km 

radius of Teesta (I) H.E. Project 

Landuse/landcover Area (ha) 

Dense Mixed Forest 13300.70 

Alpine Scrub 9501.34 

Degraded Forest 4770.56 

Rockyland 4057.74 

Rockfalls 3727.64 

Moraines 2584.91 

Ice/Glacier 6170.22 

Snow 8124.82 

12% 

5% 

16% 

7% 

8% 

Dense Mixed Forest Alpine Scrub Degraded Forest Rockyland 

9% 

25% 

Rockfalls Moraines Ice/Glacier Snow 

Figure 9.7 Percent area under various landuse/landcover categories in 7 km 

radius of the proposed Teesta (I) H.E. Project 

18%

9.3. BIOTIC ENVIRONMENT 

125 



Sikkim stretches from the low lands in the south with tropical climate to the 

mountainous regions in the north. The altitude varies right from sea level to mountain 

peaks covering a wide spectrum of flora and fauna. In such a small area one can find 

flora and fauna of many varieties from Tropical to the Alpine. Sikkim's botanical and 

zoological richness is awe- inspiring, boasting of more than 4500 species of flowering 

plants. 30% of the bird population in the country is found in Sikkim. 

9.3.1 Vegetation (details of forest types, etc.) 

Its extreme altitudinal variation brings in tremendous change in climatic conditions 

that in turn supports the biodiversity of different heights. With only 0.22% 

geographical area of the country, Sikkim harbors 1/3 rd of the country’s flowering 

plants. There are approximately 4500 species of flowering plants, 362 species of ferns 

and its allies, 11 species of oaks, 8 species of tree ferns, 448 species of orchids, 30 

species of Primula and 20 species of bamboos. Many medicinal plants, herbs and 

shrubs are found in low and high altitude areas. 

9.3.2 Flora 

The two dam sites are located in cold temperate and alpine montane terrain of Sikkim 

Himalaya. The area in the vicinity of the project is comprised of dense coniferous 

forests and dense mixed broadleaf-coniferous forests along the river course. Towards 

higher slopes the predominant vegetation communities comprise dense alpine and 

open scrub. This area experiences cold summers and severe cold winters. Owing to 

good moisture conditions and cool temperatures throughout the year at these altitudes 

the vegetation is constituted mostly by the cold temperate evergreen plant species. The 

forests are mostly confined to lower slopes in the river valley and are represented by 

all the physiognomic forms – trees, shrubs and herbs. The woody elements in these 

forests are represented by dominant Abies densa, Larix griffithii and small trees of 

Rhododendron species. In the alpine areas much of the vegetation is either alpine

126 



scrub or alpine grasslands type. Most of the scrubs are dominated by several species of 

Rhododendron bushes as well as small woody ones. Among other associates are 

species of Salix, Juniperus, Cotoneaster, Gaulthertia, Viburnum, Ribes, Rosa, Acer 

and others. The diversity of herbaceous species comprise Primula, Arisaema, 

Meconopsis, Podophyllum, Fritillaria, Gentiana and members of Ranunculaceae, 

Apiaceae and Brassicaceae. At many places besides the species of Rhododendron, 

Salix, Viburnum and several members of Rosaceae and Ericaceae are seen growing 

predominantly in the region. The alpine meadows harbour several species of 

Primulaceae, Gentianaceae, Papavaraceae, Brassicaceae, Poaceae and Juncaceae. 

These areas harbour some of the important endemic and endangered medicinal plant 

species of Himalaya. Among these species Artemisia vulgaris, Podophyllum 

hexandrum, Aconitum spp., Saussurea spp., Nardostachys jatamansi, Picrorrhiza 

kurroa and Meconopsis spp. are noteworthy. 

9.3.3 Fauna and Wildlife 

The upper parts of catchments of Lhonak chhu, Zemu chhu and Teesta River harbour 

several faunal species like Himalayan brown bear (Selenarctos thibetanus), Great 

Tibetan sheep, Snow leopard (Panthera uncia), Bharal, Himalayan tahr (Hemitragus 

jemlahicus), Hoary-bellied squirrel (Callossciurus pygerithrus), Orange-bellied 

squirrel (Dremomys lokhriah), Himalayan palm civet (Paguma larvata) and Stone 

marten (Martes foina). There are species like Civets (Viverra zibetha), porcupines 

(Hystrix brachyura), Grey musk shrew (Suncus murinus) and Bandicoot rat 

(Bandicota bengalensis). The upper reaches, i.e. the alpine areas of the catchment 

harbour mammalian species, which include Nayan, Bharal, Snow leopard, bear, 

Himalayan tahr, Barking Deer, Himalayan marmot and pikas. These animals inhabit 

areas mostly above 2,200 m in the catchment. The avifauna of the catchment is 

represented by bird species like bulbuls, thrushes, eagles, partridges, pigeons, doves, 

koels, owls, kingfishers, nightjars, woodpeckers, orioles, drongos, mynas, flycatchers, 

babblers, robins, etc. Python molurus, Naja naja and Dendrelaphis sp. are the

127 



commonly found reptilian species found in the catchment. In this stretch no fish fauna 

has been recorded. However, fishes like snow trout and minor trouts have been 

recorded downstream around Lachen. The invertebrates are represented by some 

species of butterflies and dragonflies in the catchment area. 

Among the various faunal species present in the catchment Panthera uncia, P. pardus, 

Neofelis nebulosa, Felis bengalensis, Macaca assamensis and Cervus duvaucelli are 

Scheduled as threatened animals of India while Panthera tigris, Selenarctos thibetanus 

and Cervus duvaucelli are considered as globally threatened species. 

9.3.4 Aquatic life 

The rivers in Sikkim harbour a variety of fish species. Ichthyofauna in the area is 

comprised mainly of Balm, Asala, Chepti, Gadela, etc. and snow trout and minor 

trouts are found at higher elevations. Some of the identified fish species found in the 

area are Anguilla bengalensis, Pseudochensis sulcatus, Garra annadelei, Tor putitora, 

Salvelinus fontinalis and Acrossocheilus hexagonolepis, etc. 

9.4. Existence of any Protected Area/Archaeological Sites 

There are no protected areas or areas of archaeological importance present within 7 

km radius of either of the two proposed dams. However, there are pristine dense 

forests and alpine meadows around the proposed project areas, which would be 

affected by the project activities directly or indirectly. 

9.6 PREDICTION OF ENVIRONMENTAL IMPACTS 

9.6.1. Impacts on Land Environment 

Sufficient amount of land will be required for construction of the proposed dam, 

powerhouse, colonies & approach roads etc. About 63.32 ha of land (including water

128 



bodies) would come under submergence, which would mean some disturbance and 

change in the landscape. There will be changes in the Landuse of the area and in its 

physical composition. 

9.6.2 Impacts on Water Environment 

A reservoir area covering 63.32 ha would be created due to the proposed scheme. It 

may also have some adverse impact on the fishes of river. Construction of the 

proposed dams may convert the river habitat into a lake-like reservoir. This often 

eliminates native population of fish. Warm, slow moving reservoirs also often favour 

predators of naturally occurring species. Water stagnation, may also lead to the 

accumulation of decaying materials in the reservoir and a corresponding loss of 

oxygen, which may increase substances toxic to aquatic life in the reservoir. This 

oxygen-deprived water when released from the dam, may affect fish and vegetation 

downstream. However, it is too early to predict a definitive adverse impact unless a 

detailed Environmental Impact Assessment Study is conducted in the area. 

Among the positive impacts, due to creation of a large water body, water birds are 

likely to get attracted and would also provide a good spot for tourism. Reservoir may 

also create a new habitat for lacustrine fish species that prefer deep waters. This would 

further boost the local economy with increased fishing opportunities. 

9.6.3 Impacts on Air Environment 

The construction of the proposed dam would increase dust generation in the area and 

some vehicular pollution. However these would only be limited to the construction 

period. 

9.6.4 Impacts on Flora/Fauna 

9.6.4.1 Impacts on terrestrial flora 

Due to construction of dam, about 63.32 ha of land will be inundated. The 

predominant landuse in the submergence area of dam-I is alpine open scrub forest and

129 



dense mixed forest while that of dam II is comprised of dense mixed forests, 

rockyland, traces of alpine scrub, etc. Creation of reservoir would thus result in 

habitat fragmentation and loss. All these aspects would be addressed in detail during 

the Environmental Impact Assessment Study and proper mitigatory measures would 

be formulated for implementation. 

9.6.4.2 Impacts on terrestrial fauna 

During the construction phase, a large number of machinery and construction labour 

will have to be mobilized. This activity may cause some disturbance to the wildlife 

population. Likewise blasting too is likely to generate noise level and vibration 

intermittently. The noise generated may scare the fauna in the region and force them 

to migrate to other areas. There might be some impacts due to increased human 

interference as well. 

9.6.4.3 Impacts on avi-fauna 

The construction of the proposed dam will lead to formation of a reservoir, which will 

have a fluctuating water level, which precisely means the reservoir bank will remain 

wet throughout the year. Due to such reasons grasses may grow along the reservoir 

banks. Such conditions are generally ideal for various kinds of water birds. 

9.6.4.4 Impacts on fishes 

A dam will fragment and isolate upstream resident fish. The resident species may 

congregate in the tail water release site. Fish from upstream will occasionally sweep 

downstream during the monsoon, stay in the tail water or swim further downstream. 

A dam may obstruct the route of the long and mid-distance migratory fish. There may 

be an impact on the fish composition due to construction of dam. A detailed fishery 

study would be conducted during the EIA/EMP study to determine the likely impacts 

and suitable mitigatory measures would be adopted.

9.6.5 Impacts on Socio-Economic Environment 

130 



Since the submergence area is small and no habitation is present nearby, no village 

will be submerged. Thus displacement is not anticipated. At present, there are small 

business and little employment facilities in the project area. However, with the 

construction of the project new business and employment opportunities will open up 

for the local people which are likely to improve the economic conditions of the local 

people. Further, there will be development of infrastructure facilities as housing, water 

supply, medical facilities, schools, transportation and communications. These factors 

are expected to bring about positive impact on the socio-economic status of the people 

living in the project area. There is possibility of changes in lifestyle and cultural 

values of local people due to migrant worker population. However, the impact is 

expected to be low as the number of immigrant people will be small for the project 

and most of the labourers employed in the project will be local people. 

As a part of the Environmental Impact Assessment Study, a detailed socio-economic 

survey will be carried out to determine the following: 

Information on various aspects of the affected population viz; demographic 

details, socio-economic and cultural characteristics, enumeration of personal 

properties of the affected population, education level and occupational profile 

etc. 

Enumeration of social infrastructure and community property resources in the 

submergence area. 

Ethnographic assessment of PAFs. 

9.7 ENVIRONMENTAL MANAGEMENT PLANS 

The objective of the Environmental Management Plan (EMP) is to ameliorate the 

negative impacts of a developmental project. The most reliable way to ensure proper 

implementation of these management plans is to integrate the same with various

131 



processes involved during project planning, designing, construction and operation 

phases. Based on the assessment of environmental impacts, following management 

plans will be formulated: 

Catchment Area Treatment 

Compensatory Afforestation 

Wildlife Conservation 

Resettlement and Rehabilitation 

Public Health Management System 

Muck Disposal 

Fishery Management 

Restoration of Construction Area 

Green Belt Development 

Free Fuel Provision 

Disaster Management



CHAPTER – X 

INFRASTRUCTURE

CHAPTER – X 

INFRASTRUCTURE 

10.1 EXISTING ACCESS AND INFRASTRUCTURE FACILITIES 

10.1.1 Road Communication 

139 



The Dam -I is located d/s of the confluence of Poke Chu and Lhonak Chu and near 

the place called Jedang and Dam –II is located d/s of the confluence of Chento Chu 

with Teesta river near the place called Shacham. Jedang was not approachable in 

winter due snow cover and hill slides in summer but stated to be connected by a 

difficult hilly foot path of 5.0 Km and Shacham by a road of 12 Km from Zema. The 

place Zema is 129 Km from Gangtok, 208 Km from NJP railway station and 210 Km 

from Bagdogra airport. The Zema is 4.0 Km from the Lachen, the block level village 

of Sikkim and can be accessed from Singtam-Mangan-Chungthang and Gangtok- 

Mangan-Chungthang highways. The Siliguri-Gangtok (NH-31A) and Singtam- 

Mangan-Chungthang-Lachen-Zema state highways are being maintained by BRO. 

The Powerhouse is located near the place called Zema. The Zema is 4.0 Km from 

Lachen. 

10.1.2 Housing And Community Facilities 

Lachen is the nearest village to the project area where basic facilities of health, 

schooling, market, postal and telephone are available. These facilities are catering to 

the need of very small population and would be totally inadequate for the project 

personals. It is therefore necessary to plan housing, offices, recreation, and stores etc. 

for meeting the requirement of the project. The infrastructure facilities available at 

Lachen can be utilized on a small scale in the initial stage of the commencement of 

Infrastructure work.

10.1.3 Power Availability 

140 



The state of Sikkim, at present, is dependent mainly its mini and micro hydel power 

stations for meeting its power demand. The total installed capacity of state at present is 

about 95MW. The state gets some share of power from Chuka Hydel Electric Project 

in Bhutan, Farakka Thermal Power Station, West Bengal and Rangit Hydel Power 

Project of NHPC Ltd. Teesta (V) HE Project, 510 MW being executed by NHPC in 

central sector is also under advance stage of construction. The existing transmission 

system of this state comprises of mainly 66 KV and 11 KV transmission lines. A 132 

KV S/C transmission line is being constructed from Melli border town of Sikkim- 

West Bengal to Ranipool. A 132 KV sub station is being constructed at Melli. A 

substation of 2.5MVA, 66/11KV is located at Phodong near the Mangan. Robom, the 

3.0MW micro hydel project and a 0.10 MW micro hydel projects are supplying power 

in the area. 

10.2 PROPOSED ACCESS AND INFRASTRUCTURE FACILITIES 

Keeping in view the available infrastructure facilities of communication, housing and 

power, the extent of such facilities required for the execution of Teesta (I) HE Project 

have been assessed as under. 

10.2.1 Improvement of Existing Road And Bridges 

The Powerhouse is located near the place called Zema near the highway u/s of 

confluence of Zema Chu with Teesta and is 4 Km from Lachen. It is presumed that the 

Teesta (II) HE Project shall be commissioned before the Teesta (I) HE Project, hence 

all the roads and bridges shall be upgraded for the dam of Teesta (II) H.E. Project. 

Dam-II is connected by a road of class 9 but improvements are required to be done in 

a length of 4 to 5 Km length by widening on curves and formation width. The bridge/ 

culverts from Bonsoi to Zema shall also require up gradation. The present bailey 

bridge on Zemu has been proposed for upgradation.

10.2.2 Construction of Roads & Bridges 

141 



The dam site-I &II shall be accessed from Zema. Dams site-I is located d/s of the 

confluence of Poke Chu and Lhonak Chu and presently connected by a foot path. 

Therefore, a new approach road from Zema to the dam-I, diversion tunnel and adits 

shall be constructed along with a bridge near dam location. Approach road from Zema 

to Dam-II is available but new roads to diversion tunnel, adits, surge shaft, power 

house, tailrace tunnel and a bridge across the river at dam-II shall be constructed. The 

existing road in the u/s of the dam-II shall get submerged in the reservoir; therefore, a 

new road at higher elevation shall be constructed along the reservoir for a length of 3.0 

Km. 

The main township has been proposed at near Thombu where sufficient land is 

available. However, Small Township shall also be developed near dam-II and shall be 

connected to Gangtok. 

10.2.3 Accommodation for Residential Purpose 

Project colony would have accommodation for all categories of officials deployed for 

the construction. The strength of the officials and staff of various categories required 

for the project has been worked out to 300. Each personal would be provided with the 

accommodation as per the entitlement. Keeping in view the construction period and 

subsequent operation and maintenance of the project, it is proposed to construct about 

50% of the buildings as the permanent and the remaining as temporary. This 

conclusion has been drawn on the basis that 50% of the staff strength would be 

required for maintenance and operation after the completion of the project. 

In addition to above requirement of residential facilities for regular and work charged 

project staff, buildings would be required for the staff engaged in construction. 

Requirement of built up accommodation has been worked out and it is estimated that 

about 10630 sq.m of permanent built up area and 10330 sq.m of temporary builtup

142 



area would be required. Total plinth area requirement for residential purposes worked 

out to be 20961sq.m, which includes the requirement of small requirement of work 

charged staff and labours quarter besides meeting the requirement of project officers 

and staff. 

10.2.4 Accommodation for Non-Residential Purposes 

The main office complex is proposed nearby Thombu, which is about 135 km from 

Gangtok. However, the temporary Workshops, laboratories, stores, water supply, fire 

stations, electrical substations etc would be accommodated in the project area near 

power house site and dam sites. A stockyard is proposed at railhead near new 

Jalpaiguri Railway station where construction materials like cement, steel and 

machinery and equipments would be stored for further transportation to the project 

site, Batching and mixing plants are to be commissioned, one each near dam sites and 

the other near power house site. Provision for guest houses, field hostels, schools, 

hospitals etc has also been kept. 

Accommodation required for non residential purposes have been worked out to be 

26875 sq.m of which about 50% would be permanent and rest will be temporary. 

10.3 TELECOMMUNICATION FACILITIES 

The different work sites of the project, offices, stores, laboratories, workshop and 

residences would be connected through a telecommunication network. The 

telecommunication facilities would also be provided between the projects and outside. 

Therefore, an internal telephone exchange would be provided at the project for 

communication within and outside the project. Most parts of Sikkim are presently 

connected with different parts of the world through satellite telecommunication 

network for which an earth satellite station with electronic exchange exists. The same 

network would be extended to the project area for telecommunication with outstation 

agencies.

10.4 CONSTRUCTION POWER 

143 



It is presumed that Teesta II/III/IV/V/ HE Projects shall be commissioned before the 

execution of Teesta (I) HE Project and therefore, the necessary construction power 

shall be available for the execution of Teesta (I) HE Project from a near place to 

Chungthang.



CHAPTER – XI 

CONSRUCTION PLANNING 

& SCHEDULE

CHAPTER –XI 

CONSTRUCTION PLANNING & SCHEDULE 


144 



The Equipment Planning & Construction Methodology of Teesta-I H.E. Project (4x80 

MW) in Teesta Basin Sikkim has been developed on following considerations. 

1. The project construction period has been considered as five years after 

completion of Stage I & II activities. 

2. Available Geological Data at PFR stage. 

3. Requirement of Construction Equipment has been planned to handle the 

quantities worked out on the basis of preliminary layout. 

4. Five months (May to September) rainy season has been considered 

while planning surface works. 

11.2 CONSTRUCTION METHODOLOGY 

11.2.1 Infrastructure Works: 

The main infrastructure development is proposed to be carried out in period of 12 

months. During infrastructure period Land Acquisition, construction of approach 

roads, bridges& culverts, arrangement of construction power will be undertaken. 

Critical component of project would be started from 7 th month after construction of 

approach roads. Platform to accommodate batching plant, stores for construction 

material, site workshop, offices and other buildings (residential/ non residential) 

colonies will also be developed in infrastructure period. Crawler Dozer, Loader cum 

Excavator, Air compressor, Road Roller etc. are proposed for deployment during 

infrastructure stage. 

11.2.2 Diversion of River 

The construction of two nos. diversion tunnels 6.0 m finished dia. each, Horse shoe 

shaped 600m long for Dam-I and 300 m long for Dam-II, would be carried out by full

145 



face method. Excavation of Diversion Tunnel will be carried out by deploying 

separate set of equipment i.e Two Boom drill jumbo, Jack hammers, 2.5 cum side 

dump loader & 20/25 t dumpers.. Excavation & concreting of both diversion tunnel 

would be completed in 12 months. The concreting equipment proposed are two set of 

38 cum Concrete pump, Transit mixer, shotcrete machine, Grout pump, shutters etc. 

Concreting requirement would be catered by the same batching & mixing Plant and 

Aggregate processing Plant, being proposed for each Dam . U/s & D/s Coffer dam 

would be constructed immediately after construction of diversion tunnel in 3 months 

to divert the river. River bed excavation would be taken up after completion of coffer 

dam. 

11.2.3 Concrete Dam-I 

The excavation & foundation treatment would be carried out in 2 months. Excavated 

material will be handled by 1.0/2.0 cum Hyd. Excavator and 25/35t Dumpers. 

Concreting of Dam & HM work would be carried out in further 25months. Concreting 

would be done by deploying 2 nos. Travelling Tower cranes (4.5 T at 60 m radius), 1 

No. 120 cum/hr Batching& Mixing plant and 250TPH Aggregate Processing plant. 

11.2.4 Concrete Dam-II 

The excavation and foundation treatment would be carried out in 4 months. Excavated 

material will be handled by 1.0/2.0 cum Hyd. Excavator and 25/35t Dumpers. 

Concreting of Dam & HM work would be carried out in further 25 months. Concreting 

would be done by deploying 2 nos. Travelling Tower crane (4.5 T at 60 m radius), 1 

No. 120 cum/hr Batching& Mixing plant and 250TPH Aggregate Processing plant. 

11.2.5 HRT-I, Intakes, Desilting Chambers and Silt flushing Tunnel 

Initially excavation of adits & approaches would be carried out in 5 months. 

Thereafter,2 Nos. Intake structure, 2 Nos. Dufour type Desilting chambers of size 

200m X8mX12m each and HRT of 4.0 m dia. would be excavated in 20months . 2

146 



nos. intake tunnel would be excavated by full face method. Excavation of Desilting 

Chamber would be taken up from intake tunnel. Intake tunnel would be extended upto 

full length of Desilting Chamber. Thereafter it will be expanded side wise to the full 

width of desilting chamber resulting in desilting chamber dome. Mucking of 

excavated material would be done through the tunnel. After the excavation of desilting 

chamber, concreting will be carried out. Excavation of silt flushing tunnel & gate 

operation chamber would be a parallel activity. The equipment to be deployed are Jack 

hammers, wagon drills, air compressors, skid steer loader, tippers, concrete pump, 

transit mixers etc. 

Excavation of 3.5 km long, 4.0 m finished diameter horse shoe shaped Head Race 

Tunnel is proposed by full face drilling & blasting method. It will be excavated 

through 2 nos adits. Excavation would be carried out by deploying two set of 

equipment i.e single boom drill jumbo, Tunneling excavator Loader and 10 T tipper. 

Concreting will be carried out by deploying concreting equipment i.e. Concrete pump, 

Transit Mixer etc. Concreting requirement would be catered by Batching & Mixing 

Plant & aggregate processing plant installed at dam site and 1 no. 30 cum/hr. Batching 

& Mixing plant and 50TPH aggregate processing plant at HRT. However batching & 

Mixing Plant, being proposed at Surge shaft would also cater the requirement of HRT. 

11.2.6 HRT-II, Intakes, Desilting Chambers and Silt flushing Tunnel 

Initially excavation of adits & approaches would be carried out in 5 months. 

Thereafter,2 Nos. Intake structure and 2 Nos. Dufour type Desilting chambers of size 

200m X8mX12m each and HRT of 4.0 m dia. would be excavated in 24 months . 2 

nos. intake tunnel would be excavated by full face method. Excavation of Desilting 

Chamber would be taken up from intake tunnel. Intake tunnel would be extended upto 

full length of Desilting Chamber. Thereafter it will be expanded side wise to the full 

width of desilting chamber resulting in desilting chamber dome. Mucking of 

excavated material would be done through the tunnel. After the excavation of desilting

147 



chamber, concreting will be carried out. Excavation of silt flushing tunnel & gate 

operation chamber would be a parallel activity. The equipment to be deployed are Jack 

hammers, wagon drills, air compressors, skid steer loader, tippers, concrete pump, 

transit mixers etc. 

Excavation of 4.25 km long, 4.0 m finished diameter horse shoe shaped Head Race 

Tunnel is proposed by full face drilling & blasting method. It will be excavated 

through 2 nos adits. Excavation would be carried out by deploying two set of 

equipment i.e single boom drill jumbo, Tunnel excavator loader and 10 t tippers. 

Concreting will be carried out by deploying concreting equipment i.e. Concrete pump, 

Transit Mixer etc. Concreting requirement would be catered by Batching & Mixing 

Plant & aggregate processing plant installed at dam site and 1 no. 30 cum/hr. Batching 

& Mixing plant and 50TPH aggregate processing plant at HRT. However batching & 

Mixing Plant, being proposed at Surge shaft would also cater the requirement of HRT. 

11.2.7 Surge Shaft 

For Construction of 15m diameter, 75 m high Surge Shaft, an adit to surge shaft 

bottom would be excavated in four months. After the completion of adit, pilot shaft of 

approx. 2.5 m dia would be excavated by deploying Raise climber, Jack hammers 

from bottom to top through bottom adit. Thereafter pilot hole would be further 

enlarged to excavated diameter & shaft would be lowered to full length of surge shaft 

with the help of wagon drill, jack hammer, crawler Dozer, side dump loader etc. 

Mucking would be done through the bottom adit. Concreting would be completed 

employing 2 m shutter, concrete pump, Transit Mixer & 60 cum/hr batching &mixing 

plant. Batching & Mixing Plant would also cater the part requirement of HRT and 

Pressure Shaft. Construction of surge shaft would be completed in 32 months.

11.2.8 Pressure Shaft: 

148 



Initially construction of approaches & adit would be completed. Thereafter two nos. 

825 m long 2.5 m dia. inclined pressure shaft, will be excavated in the same way as 

surge shaft by deploying , Raise climber, Jack hammer etc. Steel liner erection & 

concreting will be carried out by deploying 10/20 t winches, Slipform liner etc. 

Construction of Pressure shaft would take around 30 months. Concreting of pressure 

shaft would be done by Batching & Mixing Plant and aggregate processing plant 

proposed to be installed at surge shaft and Power House 

11.2.9 Power House 

4X 80 MW (320MW) underground power house (141 m X 22 m X 40 m size), 

Transformer Cavern & MIV would be excavated in 20 months. For excavation of 

Power House a construction adit would be excavated up to the crown of power house. 

Main access tunnel would also be excavated simultaneously. Construction adit would 

be extended up to full length of power House. Thereafter it will be expanded side 

wise to the full width of power house resulting in Power House Cavern. Mucking of 

excavated material would be done through the Construction adit. From Power House 

Cavern 4 shafts of 2.0 m diameter would be excavated up to the bottom level of draft 

tube followed by benching of Power House cavern up to the bottom of Power House. 

Mucking will be carried out through Main access Tunnel/TRT. The equipment to be 

deployed for excavation are jack hammers, wagon drills, air compressors, loader, 

excavators, tippers, winches etc. Concreting of Powerhouse would be carried out in 23 

months with the help of concrete pump, transit mixer etc. Concreting requirement 

would be catered by deploying 60 cum/hr batching & mixing plant and 100 TPH 

aggregate processing plant. Power house Installation & Testing of Machine would be 

undertaken in such a manner that Project get commissioned in 60 months from the 

start of Project construction.

11.2.10 Tail Race Tunnel: 

149 



1 No. 1000m long horse shoe shaped Tail Race Tunnel having 5.0 m finished diameter 

will be excavated by full face method. Excavation of Tail Race Tunnel would be 

carried out with two boom Drill Jumbo, Wagon drill, 2.5 cum side dump Loader , 10 t 

tippers etc. The TRT will be excavated from 7 th month & will be completed in further 

12 months. Concreting of TRT would be done with the help of concrete pump, Transit 

mixer, Batching & mixing plant & aggregate processing plant ( installed at Power 

house). 

11.2 CONSTRUCTION SCHEDULE 

Schedule has been drawn up for the actual construction phase, wherein a total period 

of five years has been assumed for construction. The schedule for stage I & II 

activities upto CCEA clearance and construction schedule has been prepared in the 

form of bar chart at annexure –11.1 & 11.2 respectively.

S. No. 

1 Preparation of stage-I activity estimates 1 

2 

Details of works 

Data collec./ application for clearance from 

MOEF 

3 MOEF clearance 1 

4 Essent. Temp. infra./access 6 

5 Estab. of G&D sites, Metrological 

obser. And Hydrological measurement 

6 Essential Geological & Geo-physical 

exploration, Topographical surveys 

7 Formulation of Feasibility Report, 

preparation of estimate for st-II activities 

8 EIA / EMP studies 15 

9 Commercial viability from CEA 1 

10 Vetting & sanction of st-II activity estimates 1 

11 Detailed Topogr./Geological/Hydro 

metero. & Construction material survey 

12 MOEF clearance 3 

13 Const. of resid./non resid. buildings,roads 

bridges and arrangement of const. Power 

14 Preparation of Detailed Project Report 

and its submission 

15 Techno Economic Clearance 3 

16 Pre PIB delibrations 1 

17 PIB Clearance 1 

18 CCEA Clearance (Investment Sanction) 1 

2 

SCHEDULE FOR STAGE-I&II ACTIVITIES (UP TO CCEA CLEARANCE) 

*This schedule is in accordances with three stage clearance policy of Ministry of Power ,Govt. of India vide no. 16/31/2000-DO(NHPC) dated 8/6/2001 

Annexure-11.1 

MONTHS 

Duration 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 

24 

11 

14 

14 

19 

14 

150 

Contd. 

Contd. 

Zero date for 

Construction

Sl. 

No. 

Name of Work Unit Quantiy Duration 

(months) 

1 INFRASTRUCTURE DEVELOPMENT 

a Acquisition of private & forest land Ha 85 8 

b Construction of roads & buildings 

LS 

12 

2 AWARD OF CONTRACTS 

a Tendering & awarding 

LS 

3 

b Mobilization 

LS 

3 

3 DIVERSION TUNNELS (2 nos. 6 m dia 

horseshoe of 600m/300 m long ) 

a 

Excavation 

3 

m 86,000 8 

b Concrete Lining 3 

m 16,500 6 

c HM Works Job LS 6 

d Plugging of DT's Job LS 2 

4 4 Nos.COFFER DAMS (U/s & D/s) 

for Dam-I& Dam II 

Const.of Coffer Dams & River Diversion m 3 1,18,000 3 

5 CONCRETE DAM-I (45 m High, 350 m 

Length at top ) with Spillways 

a Excavation and foundation treatment m 3 

68,000 

2 

b Mass Concreting m 3 

2,28,500 

15 

c Errection of Hyromechanical gates & misc. works LS LS 

15 

d Reservoir filling Job 3 

6 CONCRETE DAM-II (60 m High, 240 m 

Length at top )with Spillways 

a Excavation and foundation treatment m 3 

2,03,000 

4 

b Mass Concreting m 3 

2,64,000 

18 

c Errection of Hyromechanical gates & misc. works LS LS 

12 

d Reservoir filling Job 3 

7 HEAD RACE TUNNEL-I (4m dia ,3.5 km 

length), INTAKES & DESILTING 

CHAMBERS (2 nos.of size 200x8x12 m ) 

a Excavation of adits (2 nos. ) m 5 

b Excavation 3 

m 1,77,500 20 

c Concrete Lining & Grouting 3 

m 48,000 18 

d HM Works Job LS 15 

e Cleanning, Adit pluggung & other misc. works Job LS 3 

f HRT filling Job 1 

8 HEAD RACE TUNNEL-II (4m dia 

4.25 km length),INTAKES & DESILTING 

CHAMBERS (2 nos.of size 200x8x12 m ) 

a Excavation of adits m 5 

b Excavation 3 

m 1,97,500 24 

c Concrete Lining & Grouting m 3 53,700 20 

d HM Works Job LS 15 

e Cleanning, Adit pluggung & other misc. works Job LS 3 

f HRT filling Job 1 

9 POWER HOUSE COMPLEX 

a Exc. of Cavern of PH, TH & MIV including Adits 

m 3 

2,00,000 20 

b Concreting in sub & super structures 

3 

m 80,000 23 

c Erection of EOT crane Job 3 

10 SURGE SHAFT (15 m dia.,75 m Vertical 

Height) 

a Excavation 3 

m 62,000 20 

b Concreting 3 

m 5,000 12 

11 PRESSURE SHAFTS( 2 nos.,2.5 m dia 825 

m inclined length ) & PENSTOCKS 


m 28,000 20 

b Erection of steel liners & Concreting 3 

m 20,000 15 

12 TAILRACE TUNNEL (5m dia horseshoe 

shaped,1000m long) 


m 27,000 12 

b Concreting & HM Works 3 

m 7,800 10 

13 SWITCHYARD(Size 250 x180 m) m 3 Exc.=60,000 

Conc.=4000 

18 

14 ELECTRO-MECHANICAL WORKS 

a Erection, Testing & Commisioning of E&M components Job 34 

Note: The time assumed for various activities is inclusive of the effect of monsoon. 

CONSTRUCTION SCHEDULE OF TEESTA-I HE PROJECT (320 MW), SIKKIM 

Ist year IInd year 

Schedule of Constructiom 

IIIrd year IVth year 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 

151 

V th year 

Annexure -11.2



CHAPTER – XII 

COST ESTIMATE

CHAPTER –XII 

COST ESTIMATES 

152 



PRELIMINARY COST ESTIMATES FOR CIVIL, HYDRO-MECHANICAL, 

ELECTRO-MECHANICAL AND TRANSMISSION WORKS 

The estimate has been prepared to arrive at the Capital Cost of Teesta-I H. E. Project 

and is of Pre-feasibility level of accuracy. The base date of the estimate is June 2003 

and the Cost is expressed in Indian Rupees. The Cost Estimate is divided into Civil, 

Electrical and Transmission Works. For Civil Works, the sub heads are as under: - 

12.1 I-WORKS 

Under this head, provision has been made for various components of the Project as 

detailed hereunder:- 

A-Preliminary 

Under A-Preliminary, provision has been made for all surveys and investigations to be 

conducted to arrive at the optimum of the Project Components. 

B-Land 

This covers the provision for acquisition of land for construction of the Project, 

colonies, offices and stores and compensation for trees and standing crops etc. 

C-Works 

This covers the cost of Diversion Tunnels, Coffer dams, Concrete Dams and Spillways 

along with associated Hydro-mechanical equipment.

J-Power Plant Civil Works 

153 



This covers the cost of project components viz. Intake Structure, Headrace Tunnel and 

TRT, Power House and Transformer Cavern, Pressure Shaft, Surge Shaft and other 

Appurtenant Works. 

The quantities indicated in the estimates for C - Works & J-Power Plant Civil Works 

(Civil & HM) are calculated from the preliminary Engineering drawings and as per 

experience of other on-going or commissioned projects. 

The unit rates for various items are taken as per the Guidelines issued by CEA for 

preparation of PFRs. It has been assumed that the quarry is available at a distance of 

10 Kms from the work site. 

K-Buildings 

Buildings, both residential and non-residential have been provided under this head. 

Under the permanent category only those structures have been included which shall be 

subsequently utilized during the operation and maintenance of the project. The costs 

are worked out on plinth area basis prevalent in the area for the type of construction 

involved. 

O-Miscellaneous 

Under this head provision has been made to cover the cost of the following 

miscellaneous works. 

a) Capital cost of electrification, water supply, sewage disposal, fire 

fighting equipments etc. 

b) Repair and maintenance of electrification, water supply, sewage 

disposal, medical assistance, recreation, post office, telephone and 

telegraph office, security arrangements, fire fighting, inspection 

vehicles, schools, transport of labour etc.

154 



c) Other services such as laboratory testing, R&M of Guest House and 

transit camps, Community center, retrenchment compensation, 

photographic instruments as well as R&M charges etc. 

P-Maintenance During Construction And Y-Losses On Stock 

A provision of 1% and 0.25% of C-Civil works, J-Power Plants, K-Buildings & R- 

Communications has been made for maintenance of works during construction period 

and losses on stock respectively. 

Q-Special Tools And Plant 

It is assumed that the work will be carried out through Contracts and not through 

departmental construction. Accordingly, provision for general purpose equipment and 

inspection vehicle only has been made as per CWC guidelines. 

R-Communication 

Provision under this head covers the cost of new roads, widening/improvement of 

roads and strengthening of bridges. The costs of roads and bridges are based on the 

rate structure prevalent in the area of the Project, for the type of construction involved 

X-Environment And Ecology 

Provision under this head has been taken as 2% of I -Works towards bio-diversity 

Conservation, creation of Green Belt, Restoration of Construction Area, Catchment 

Area Treatment, Compensatory Afforestation etc 

12.2 II-ESTABLISHMENT 

Provision for establishment has been made at 8% of I-works minus B-Land for civil 

works.

12.3 III-TOOLS AND PLANTS 

155 



This provision is distinct from that under Q-Special T&P and is meant to cover cost of 

survey instruments, camp equipment and other small tools and plants. The outlay is 

provided at 1% of cost of I-works. 

12.4 IV-SUSPENSE 

No provision has been made under this head as all the outstanding suspense are 

expected to be cleared by adjustment to appropriate heads at completion of the project. 

12.5 V-RECEIPTS AND RECOVERIES 

Under this head, provision has been made for estimated recoveries by way of resale or 

transfer of equipment used in infrastructure works, DG set and Temporary buildings. 

12.6 ELECTRICAL WORKS AND GENERATING PLANT 

The cost of Generating Plant and Equipment is based on indigenous sources. The 

prices of auxiliary equipment and services are based on prevailing market prices/costs 

incurred at other ongoing or commissioned projects.

156 



ABSTRACT OF COST OF WORKS 

S.No Description Amount 

(Rs. in 

Crores) 

( June 2003 

P.L.) 

A CIVIL WORKS 

1. DIRECT CHARGES 

I - Works 

A - Preliminary 17.91 

B - Land 33.63 

C - Works 245.50 

J - Power Plant Civil Works 291.19 

K - Buildings 39.26 

O - Miscellaneous 27.34 

P - Maintenance 6.18 

Q-Special Tools & Plants 5.20 

R - Communication 41.77 

X - Environment & Ecology 14.48 

Y - Losses on Stock 1.54 

Total of I-Works 723.99 

II - Establishment @ 8% of cost of I-Works less B-Land 55.23 

III - Tools and Plants @ 1% of cost of I-Works 7.24 

IV - Suspense 0.00 

V - Receipt & Recoveries (-) -5.55 

TOTAL DIRECT CHARGES 780.91 

2. INDIRECT CHARGES 

a) Capitalised Value of Abatement of Land Revenue 0.31 

b) Audit and Account Charges @1% of cost of I-Works 7.24 

TOTAL INDIRECT CHARGES 7.55 

TOTAL OF DIRECT & INDIRECT CHARGES 788.45 

ABSTRACT : 

A Civil Works 788.45 

B Electrical Works 301.03 

C Transmission Works 1.40 

TOTAL COST 1090.88 

C IDC 115.71 

D Total Cost With IDC 1206.59

S. 

No. 

A- Preliminary 

Description of Work Unit Qty Rate 

( Rs) 

157 



Rs. In lakhs 

Amount 

1.0 Expenditure for preparation of PFR LS 14.00 

2.0 Preparation of Detailed Project 

Report 

2.1 Detail survey for final location of 

project componenets 

LS 50.00 

2.2 Aerial survey, contour survey for 

reservoir basin including 

establishment of permanent 

LS 60.00 

benchmarks. 

2.3 Geological and geophyical surveys 

and investigation 

I) Drifting m 1200 0.15 180.00 

ii) Geophysical LS 45.00 

iii) Core drilling m 1200 0.20 240.00 

2.4 Hydrological and Metrological 

surveys including establishment of 

rain gauges/ river gauges and 

discharge, sedimentation stations 

and their running charge for 1 year 

LS 30.00 

2.5 Investigations for foundation and 

rock testing 

LS 15.00 

2.6 Investigation for availability of 

construction materials. 

LS 20.00 

2.7 Construction of access roads to 

facilitate investigations 

LS 40.00 

2.8 Model experiment. LS 60.00 

2.9 Computer and telecommunication 

facilities. 

LS 30.00 

2.10 Vehicles for inspecting officers for 

site investigations 

LS 60.00 

2.11 Camping equipment LS 50.00 

2.12 Preliminary soil test, establishing 

soil testing laboratory. 

LS 20.00

2.13 Consultant’s fees including charges 

for preliminary design work or 

device 

158 



LS 50.00 

2.14 Training of engineers during 

investigation and preparation of 

project reports 

LS 20.00 

2.15 Ground water studies. LS 15.00 

2.16 Environment and ecological LS 25.00 

studies. 

2.17 Preparation and printing of DPR LS 50.00 

Sub Total( I ) 1074.00 

3.0 Pre-Construction Stage 

Investigations 

3.1 Topographical Surveys LS 60.00 

3.2 Geological Investigation 

I) Diamond Core Drilling m 500 0.15 75.00 

ii) Exploratory Drift m 500 0.20 100.00 

iii) Excavation in trenches & pits LS 5.00 

iv) Testing of Samples LS 10.00 

3.3 Hydrological and Silt data 

collection - 3 sites for 5 years 

Year 5 6.00 30.00 

3.4 Meteorological Data Collection 3 

sites for 5 years 

Year 5 6.00 30.00 

3.5 Construction material survey 

I) Topographical Survey LS 5 0.10 0.50 

ii) Collection and Transportation of LS 10.00 

samples 

iii) Laboratory Testing of Samples 

including charges for all T&P and 

Machineries 

LS 15.00 

3.6 Model studies LS 15.00 

3.7 Seismological data collection for 5 Year 5 1.00 5.00 

years 

3.8 Survey for layout of colonies and 

roads 

I) Residential-cum-Office 

accomodation 

Ha 10 0.50 5.00 

ii) Batching Mixing Plant and 

Workshop 

Ha 3 0.50 1.50 

iii) Project and quarry site road Km 40 0.50 20.00

159 



3.9 Workcharged establishment for 

unforseen works 

Year 5 4.00 20.00 

4.0 Design & Consultancy 

4.1 Cost of Design Establishement 

including procurement of printing 

stationery and preparation of 

completion report, History of 

Project etc. 

LS 50.00 

4.2 Cost of Special Studies and 

Designs 

LS 40.00 

4.3 Fees for Consultant and specialists LS 40.00 

4.4 Training of Engineers LS 30.00 

5.0 Equipment 

5.1 Drawing and Mathematical 

Instruments 

LS 40.00 

5.3 Survey Instruments LS 75.00 

5.4 Office instruments LS 40.00 

Sub Total (II) 717.00 

Grand Total :( I+II ) 1791.00

160 



B-LAND 

S. No. Description Unit Qty. Rate (Rs) 

Rs. In lakhs 

Amount 

(Rs) 

1 Private land Requirement 

Permanent residential and non 

residential buildings 

Ha 30.00 6.30 189.00 

Diversion tunnel Ha 6.00 6.30 37.80 

Submerged in the reservior area Ha 60.00 6.30 378.00 

Construction of dam Ha 10.00 6.30 63.00 

Construction material Ha 4.00 6.30 25.20 

Construction of approach Roads Ha 70.00 6.30 441.00 

Power house Ha 6.00 6.30 37.80 

Construction of adits Ha 3.00 6.30 18.90 

Switch Yard Ha 2.00 6.30 12.60 

Surge Shaft Ha 2.00 6.30 12.60 

Land for Misc Purpose Ha 2.00 6.30 12.60 

Sub Total (1) 195.00 1228.50 

2 Forest land 

River bed Ha 20.00 0.00 0.00 

Underground Ha 6.00 0.00 0.00 

Sub total (2) 26.00 0.00 

3 Other Compensation 

Cost of crops standing on Ha 156 1.89 294.84 

cultivated land required @ 30% 

of cultivated land 

Compensation for trees LS 10.00 

Sub total (3) 304.84 

4 Land on lease/ hire for 5 

Years 

Dumping area Ha 6.00 2.50 15.00 

Area for batching and mixing Ha 4.00 2.50 10.00 

plant 

Temporary Residential and 

Non- Residential buildings 

Ha 10.00 2.50 25.00 

Contractors Colony Ha 6.00 2.50 15.00 

Contractors 

facilities 

Construction Ha 4.00 2.50 10.00

161 



Railway Siding Facilities Ha 2.00 2.50 5.00 

Electro - Mechanical Works Ha 2.00 2.50 5.00 

Hydro -Mechanical Works Ha 2.00 2.50 5.00 

Sub Total (4) 36.00 90.00 

5 Misc. Compensation 

Compensation for relocating 

10.00 

electric and telephone poles 

Crop Compensation for 

submergence 

LS 1000.00 

Sub Total (5) 1010.00 

Total (1+2+3+4+5) 2633.34 

6 Interest charges on account of 

award for the period taking over 

possession of land and date of 

award @ 12% per year of 25% 

cost of land acquisition for two 

years 

158.00 

7 Solatium charges for compulsary 

acquisition of land @ 30% of the 

cost of private land 

368.55 

8 Provision for legal charges @1% 

on total compensation 

26.33 

9 Labour and material required for 

measurement and demarcation of 

land and properties @1%of land 

acquision 

10 Establishment charges @ 6.25% 

of cost of total compensation 

12.29 

164.58 

Grand Total 3363.09

S. 

N. 

ABSTRACT OF COST OF C - WORKS 

162 



Description Amount (Rs. In Lakhs) 

Civil HM Total 

1. Diversion Tunnels (Both) 1701.91 236.25 1938.16 

2. Coffer Dams (For Both the Dams) 1589.44 1589.44 

3. Concrete Dams (For Dam-I & Dam- 

II) 

13300.86 1111.74 14412.60 

4. Spillways (For Dam-I & Dam-II) 6128.03 6128.03 

TOTAL 22720.24 1347.99 24068.23 

ADD FOR WORKS TAX @ 2% 454.40 26.96 481.36 

GRAND TOTAL 23174.65 1374.95 24549.60

S. 

No. 

163 



RIVER DIVERSION WORKS (FOR BOTH DIVERSOIN TUNNELS) 

DIVERSION TUNNELS 

Description Unit Qty. Rate 

(Rs.) 

Amount 

( Rs. in 

Lakhs) 

1 Surface Excavation 

1.1 Common excavation Cum 35,000 125 43.75 

1.2 Rock excavation Cum 8,000 300 24.00 

2 Underground excavation Cum 43,000 1000 430.00 

3 Rock Support System 

3.1 Rockbolts M 21,000 400 84.00 

3.2 Steel Rib Supports MT 150 42000 63.00 

3.3 Shotcrete Cum 2,000 4000 80.00 

3.4 Concrete lagging Cum 350 7000 24.50 

4 Concrete 

4.1 Concrete lining M-20 Cum 6,000 4000 240.00 

4.2 M-15 Cum 5,500 2930 161.15 

4.3 M-25 Cum 5,000 3610 180.50 

5 Reinforcement MT 500 27000 135.00 

Sub total A 1465.90 

6 Miscellaneous and ancillary works @ 

7.5% of sub-total A 

7.50% 109.94 

Sub total B 1575.84 

7 Instrumentation @ 1% of sub-total B 1.00% 15.76 

8 Dewatering @ 2% of sub total B 2.00% 31.52 

9 Contingency @ 3% of sub-total B 3.00% 47.28 

10 Work Charged establishment @ 2% of 

Sub-total B except of lump-sum items 

2.00% 31.52 

Total 1701.91

S. 

No. 

COFFER DAMS 

(FOR BOTH THE DAMS) 

164 



Description Unit Qty. Rate Amount 

(In 

Lakhs) 



2 Embankment Construction 

2.1 Earth/ Rockfill Cum 80,000 342 273.60 

2.2 Impervious Core Cum 30,000 354 106.20 

2.3 Filter Cum 8,000 901 72.08 

3 Concrete 

3.1 Concrete cut off wall Sqm 5,000 20000 1000.00 



Sub Total(A) 1464.38 

0.50% 7.32 

Sub Total(B) 1471.70 

5 Dewatering @ 3% of sub total-B 3.00% 44.15 

6 Contingency @ 3% of sub-total-B 3.00% 44.15 

7 Work Charged establishment @ 2% 

of Sub-total-B except of lum-sum 

items 

2.00% 29.43 

Total 1589.44

S. 

No. 

CONCRETE DAMS 

(FOR DAM-I & DAM-II) 

Description Unit Quantity Rate 

(Rs.) 

165 



Amount 

( Rs. in 

Lakhs) 




2 Rock Support system 

2.1 Rock bolts M 2,500 400 10.00 

2.2 shotcrete cum 1,000 4000 40.00 

3 Concrete 

3.1 M-15 cum 325,000 2930 9522.50 

3.2 M-20 cum 2,500 3390 84.75 

3.3 M-25 cum 40,000 3610 1444.00 

4 Reinforcement steel MT 2,000 27000 540.00 


5 Miscellaneous and ancillary 

works @ 2.5% of sub-total 

2.5% 297.63 

Sub-Total(B) 12202.63 

6 Instrumentation @ 1% of sub-total 1% 122.03 

7 Dewatering @ 3% of sub total 3% 366.08 

8 Contingency @ 3% of sub- 

3% 366.08 

total 

9 Work Charged establishment 

@ 2% of Sub-total except of 

lum-sum items 

2% 244.05 

Total 13300.86

S. 

No. 

SPILLWAYS 

(FOR DAM-I & DAM-II) 

166 



Description Unit Qty. Rate (Rs.) Amount 

( Rs. in 

Lakhs) 




2 Concrete 

2.1 M-15 Cum 75,000 2930 2197.50 

2.2 M-25 Cum 50,000 3610 1805.00 

3 Reinforcement steel MT 5,000 27000 1350.00 

4 Structural Steel T 300 42000 126.00 

Sub Total 5590.25 

5 Various Miscellaneous works 

like wire mesh/steel fibre 

reinforcement, drilling & 

grouting, PVC pipes, water 

stops, other steel works, slope 

protection works, road works, 

architectural works for dam etc 

@ 2.5% of sub-total 

(A) 

1.5% 83.85 

Sub-Total 

(B) 

5674.10 

6 Instrumentation @ 1% of sub-total 1% 56.74 

7 Dewatering @ 3% of sub total 2% 113.48 

8 Contingency @ 3% of sub-total 3% 170.22 

9 Work Charged establishment @ 

2% of Sub-total except of 

lump-sum items 

2% 113.48 

Total 6128.03

167 



J -POWER PLANT APPURTENANCES (CIVIL WORKS) 

S. Description Amount (Rs. in Lakhs) 

No. CIVIL HM TOTAL 

1. Intake Structure (For Both the Water 

Conductor Systems) 

1303.26 634.62 1937.88 

2. Desilting Chambers (Including S. F. T.) 2749.28 561.12 3310.40 

(For Both the Water Conductor Systems) 

3. Adits 1343.34 14.28 1357.62 

4. Head Race Tunnels (2 Nos.) & Tail Race 

Tunnel 

7208.71 21.84 7230.55 

5. Surge Shaft 646.87 150.57 797.44 

6 Pressure Shafts & Penstocks 1265.25 3252.38 4517.62 

7. Power Housr Complex 8894.27 8894.27 

8. Switchyard 501.94 501.94 

Total 23912.91 4634.81 28547.72 

Add For Works Tax @ 2% 478.26 92.70 570.95 

GRAND TOTAL 24391.17 4727.50 29118.67

S. 

No. 

INTAKE STRUCTURES 

(FOR BOTH THE WATER CONDUCTOR SYSTEMS) 

168 



Description Unit Quantity Rate(Rs.) Amount 

( Rs. in 

Lakhs) 

1 Surface excavation 




3 Supports System 

3.1 Rock bolts m 11,000 400 44.00 

3.2 Steel Rib Supports MT 50 42000 21.00 

3.3 Shotcreting Cum 800 4000 32.00 


4 Concrete 

4.1 M15 Cum 1,000 2930 29.30 

4.2 M-20 Cum 500 3390 16.95 

4.3 M-25 Cum 15,000 3610 541.50 

5 Reinforcment Steel MT 1,000 27000 270.00 



works @ 1.5% of sub-total 

1.5% 18.00 


7 Instrumentation @ 1% of sub-total 

B 

1% 12.18 

8 Dewatering @ 1% of sub total B 1% 12.18 

9 Contingency @ 3% of sub-total B 3% 36.54 


@ 2% of Sub-total B except 

of lum-sum items 

2% 24.36 

Total 1303.26

S. 

No. 

169 



DESILTING CHAMBERS (INCLUDING S.F.T.) 

(FOR BOTH THE WATER CONDUCTOR SYSTEMS) 


( Rs. in 

Lakhs) 






3.1 Rock bolts m 40,000 400 160.00 

3.2 Steel Supports MT 300 42000 126.00 

3.3 Shotcreting Cum 2,000 4000 80.00 


4 Concrete 

4.1 M15 Cum 14,000 2930 410.20 

4.2 M-20 Cum 1,500 3390 50.85 

4.3 M-25 Cum 10,000 3610 361.00 

5 Reinforcement Steel MT 800 27000 216.00 



works @3.5% of sub-total 

3.5% 86.08 


7 Instrumentation @ 1% of sub-total B 1% 25.46 




@ 2% of Sub-total B except 

of lum-sum items 

2% 50.91 

Total 2749.28

S. 

No. 

ADITS 

170 




in Rs. 

Amount 

( Rs. in 

Lakhs) 

1 Surface Excavation at Portals 





3.1 Rockbolts m 30,000 400 120.00 

3.2 Steel Rib Support MT 200 42000 84.00 

3.3 Shotcrete Cum 2,500 4000 100.00 


4 Concrete 

4.1 Cement Concrete lining M-20 Cum 1,500 4000 60.00 

4.2 M-15 Cum 6,500 2930 190.45 

4.3 M-25 Cum 1,200 3610 43.32 

5 Reinforcement steel MT 150 27000 40.50 




3.5% 42.06 






Sub-total except of lum-sum items 

2% 24.88 

Total Civil Cost 1343.34

S. 

No. 

171 



HEAD RACE TUNNELS (2 Nos.) & TAIL RACE TUNNEL 


( Rs. in 

Lakhs) 






3.1 Rockbolts m 142,000 400 568.00 

3.2 Steel Supports MT 800 42000 336.00 

3.3 Shotcrete Cum 11,000 4000 440.00 

3.4 Concrete lagging Cum 2,500 7000 175.00 

4 Concrete 

4.1 Concrete Linning M20 Cum 32,000 4000 1280.00 

4.2 M15 Cum 27,500 2930 805.75 

4.3 M-25 Cum 8,000 3610 288.80 

5 Reinforcement MT 650 27000 175.50 

Sub-Total(A) 6209.05 

6 Miscellaneous and ancillary works 

@7.5% of sub-total A 

7.5% 465.68 



B 

1% 66.75 




of Sub-total B except of lum-sum 

items 

2% 133.49 

Total 7208.71

S. 

No. 

SURGE SHAFT 

172 



Description Unit Qty Rate (Rs.) Amount 

( Rs. in 

Lakhs) 




2 Underground excavation 

2.1 Surge shaft Excavation Cum 12,000 1200 144.00 

2.2 Surge shaft Excavation with raise Cum 200 1500 3.00 

borer 

2.3 Concrete Lagging Cum 200 7000 14.00 

3 Support System 

3.1 Rock bolts m 11,000 400 44.00 

3.2 Steel Ribs Support MT 25 42000 10.50 

3.3 Shotcrete Cum 500 4000 20.00 

4 Concrete 

4.1 M20 Cum 2,000 3390 67.80 

4.2 M-25 Cum 3,000 3610 108.30 

5 Steel Works 

5.1 Deformed Reinforcement Steel MT 300 27000 81.00 

5.2 Steel Liner MT 25 70000 17.50 



@ 1.5% (sub-total) A 

1.5% 8.85 



B 

1% 5.99 




of Sub-total B except of lum-sum 

items 

2% 11.98 

Total 646.87

S. 

No. 

PRESSURE SHAFTS AND PENSTOCKS 

173 



Description Unit Quantity Rate in Rs. Amount 

( Rs. in 

Lakhs) 



2.1 Rock bolts M 20,000 400 80.00 

2.2 Steel ribs support MT 150 42000 63.00 

2.3 Shotcrete Cum 2,500 4000 100.00 

3 Concrete 

3.1 Backfill concrete M15 Cum 20,000 2930 586.00 



works @ 1.5% (sub-total) 

1.5% 17.48 



6 Dewatering @ 1% of sub total 

B 

1% 11.82 

7 Contingency @ 3% of sub-total 

B 

3% 35.47 


2% of Sub-total B except of 

lum-sum items 

2% 23.65 

Total Civil Cost 1265.25

S. 

No. 

POWER HOUSE COMPLEX 

174 



Description Unit Qty. Rate 

(Rs.) 

Amount ( 

Rs. in 

Lakhs) 

1 Under ground excavation Cum 200,000 1000 2000.00 


2.1 Rockbolts m 80,000 400 320.00 

2.2 Steel ribs support MT 100 42000 42.00 

2.3 Shotcrete Cum 8,000 4000 320.00 

2.4 Concrete lagging Cum 1,000 7000 70.00 

3 Concrete 

3.1 Backfill Concrete M15 Cum 1,000 2930 29.30 

3.2 Concrete Lining M20 Cum 4,000 4000 160.00 

3.3 M25 Cum 75,000 3610 2707.50 

4 Reinforcement Steel MT 7,500 27000 2025.00 

5 Structural Steel for roof trusses etc. MT 350 42000 147.00 

6 Masonry 

6.1 Stone Cum 1,000 2000 20.00 

6.2 Brick Cum 2,000 2000 40.00 



@4.5% of sub-total 

4.5% 354.6 






Sub-total B except of lum-sum items 

2% 164.71 

Total 8894.27

S. 

No. 

SWITCHYARD 


(Rs.) 

175 



Amount 

( Rs. in 

Lakhs) 





2.1 Rock bolts m 2,000 400 8.00 

2.2 Shotcrete Cum 100 4000 4.00 

3 Earthwork in Filling Cum 50,000 342 171.00 

4 Concrete 

4.1 M15 Cum 2,000 2930 58.60 

4.2 M20 Cum 2,000 3390 67.80 

5 Deformed Reinforcement Steel MT 100 27000 27.00 

6 Stone/Brick Masonry Cum 1,000 2000 20.00 



@4.5% of sub-total A 

4.5% 20.20 





2% of Sub-total B except of lumsum 

items 

2% 9.38 

Total 501.94

S. 

No. 

HYDRO MECHANICAL EQUIPMENT 

176 



Detail of Items Unit Qty.. Rate 

(Rs.) 

Amount 

(Rs. In 

Lakhs) 

DAM-I 

1 Diversion tunnel gate & hoist 

Gate(Fixed wheel type) (6.0m x 8.0m)- 1 

No. 

Ton 50 60000 30.00 

Embedded Parts - 1 Set Ton 15 50000 7.50 

Ropedrum hoist 140 T Capacity - 1 Set Ton 50 100000 50.00 

Hoist Supporting structure and trestle - 1 

Set 

Ton 50 50000 25.00 

2 Spillway structure 

a) Spillway Radial Gates (4.0m x 6.0m) -5 

Nos. 

Ton 200 100000 200.00 

Embedded Parts (including anchorages, 

hoist structure) including breast wall liners 

- 5 Sets 

Ton 120 50000 60.00 

Hydraulic Hoist (One power pack + Two 

cylinders of 40T Cap. each) 

Set 5 2800000 140.00 

b) Spillway stoplog( 4.0m x 8.0m) - 1 No. Ton 24 60000 14.40 

Embedded Parts - 5 Sets Ton 50 50000 25.00 

Gantry crane 20 T capacity Set 1 2200000 22.00 

Lifting Beam - 1 No. Ton 3 50000 1.50 

De-icing arrangement for gate & Stoplog LS 1800000 18.00 

Portable oil filter unit along with 

Contamination checking kit & Low 

vacuum dehydration and degassification 

Set 1 500000 5.00 

unit 

Portable trolley mounted gasoline engine 

operated power pack 

Set 1 1000000 10.00 

3 Intake structure 

a) TrashRacks and Embedded parts( 9m X 

7m) - 2 Set 

Ton 36 50000 18.00 

Trash rack cleaning machine Set 1 10000000 100.00 

De-icing arrangement for Trash Rack LS 1000000 10.00 

b) Intake gate(fixed wheel type) including 

ballast (4.5m x 4.5m) - 2 No. 

Ton 68 60000 40.80

177 



Embedded Parts -2 Set Ton 24 50000 12.00 

Rope drum hoist 65T Cap.- 2 Sets Ton 46 100000 46.00 

Hoist platform and trestle - 2 Sets Ton 46 50000 23.00 

De-icing arrangement for Intake gate LS 600000 6.00 

b) Intake bulkhead gate (4.5m x 4.5m) - 2 No. Ton 24 60000 14.40 




4 Desilting Chamber Gates 

Outlet Gates 

Gate (Slide Type) 4.0m x4.0m -1No. Ton 12 60000 7.20 

Embedded parts - 2 Set Ton 10 50000 5.00 

EOT Crane 25T Cap. Set 1 2500000 25.00 

5 Silt Flushing Gates (Slide Type) 

Gates (Service & Emergency) 2.0m x3.0m Ton 20 100000 20.00 

- 4 Nos. 

Embedded parts (including bonnet, bonnet 

cover,gate body liner etc.)- 4Set 

Hydraulic Hoist ( Two Double acting 

cylindres of 180T Cap. each + one 

common power pack) 

Ton 80 50000 40.00 

Set 2 8500000 170.00 

6 U/s Surge shaft gate & hoist 

Gate(Slide Type) 4.0m x4.0m - 1 No. Ton 27 60000 16.20 


Rope drum hoist 40T Cap.- 1 Set Ton 14 100000 14.00 

Hoist platform and trestle - 1 Set Ton 14 50000 7.00 

De-icing arrangement for Surge Shaft gate LS 400000 4.00 

7 Adit Gates 

Adit gates (2.5m x2.5m) - 1 Nos. Ton 8 60000 4.80 


8 Instruments and Remote Control Set 1 5000000 50.00 

9 D G Set 312.5 KVA Set 1 1500000 15.00 

Sub Total 1295.80 

10 Spare parts & contingency (5% of total 

cost) 

5% 64.79 

Total 1360.59 

Add for Works Tax and Surcharge 2% 27.21 

Grand Total (Dam-I) 1387.80

178 



DAM-II 

11 Diversion tunnel gate & hoist 

Gate(Fixed wheel type) (6.0m x 8.0m)- 1 

No. 

Ton 50 60000 30.00 


Ropedrum hoist 140 T Capacity - 1 Set Ton 50 100000 50.00 

Hoist Supporting structure and trestle - 1 

Set 

Ton 50 50000 25.00 

12 Spillway structure 

a) Spillway Radial Gates (4.5m x 6.0m) -4 

Nos. 

Ton 160 100000 160.00 

Embedded Parts (including anchorages, 

hoist structure) including breast wall liners 

- 4 Sets 

Ton 96 50000 48.00 

Hydraulic Hoist (One power pack + Two 

cylinders of 40T Cap. each) 

Set 4 2800000 112.00 

b) Spillway stoplog( 4.5m x 8.0m) - 1 No. Ton 24 60000 14.40 

Embedded Parts - 4 Sets Ton 40 50000 20.00 

Gantry crane 20 T capacity Set 1 2200000 22.00 

Lifting Beam - 1 No. Ton 3 50000 1.50 

De-icing arrangement for gate & Stoplog LS 1500000 15.00 

Portable oil filter unit along with 

Contamination checking kit & Low 

vacuum dehydration and degassification 

Set 1 500000 5.00 

unit 

Portable trolley mounted gasoline engine 

operated power pack 

Set 1 1000000 10.00 

13 Intake structure 

a) TrashRacks and Embedded parts( 9m X 

7m) - 2 Set 

Ton 36 50000 18.00 

Trash rack cleaning machine Set 1 10000000 100.00 

De-icing arrangement for Trash Rack LS 1000000 10.00 

b) Intake gate(fixed wheel type) including 

ballast (4.5m x 4.5m) - 2 No. 

Ton 68 60000 40.80 




De-icing arrangement for Intake gate LS 600000 6.00 

b) Intake bulkhead gate (4.5m x 4.5m) - 2 No. Ton 24 60000 14.40 

Embedded Parts -2 Set Ton 10 50000 5.00

179 





14 Desilting Chamber Gates 

Outlet Gates 

Gate (Slide Type) 4.0m x4.0m -1No. Ton 12 60000 7.20 


EOT Crane 25T Cap. Set 1 2500000 25.00 

15 Silt Flushing Gates (Slide Type) 

Gates (Service & Emergency) 2.0m x3.0m Ton 20 100000 20.00 

- 4 Nos. 

Embedded parts (including bonnet, bonnet 

cover, gate body liner etc.)- 4Set 

Hydraulic Hoist ( Two Double acting 

cylindres of 180T Cap. each + one 

common power pack) 

Ton 80 50000 40.00 

Set 2 8500000 170.00 

16 U/s Surge shaft gate & hoist 





De-icing arrangement for Surge Shaft gate 

D/s Surge shaft gate & hoist 

LS 200000 2.00 





De-icing arrangement for Surge Shaft gate 

LS 200000 2.00 

17 Adit Gates 

Adit gates (2.5m x2.5m) - 1 Nos. Ton 8 60000 4.80 


18 Pressure shaft steel Liner 

Steel Liner (ASTM A537 Cl.1) - 2 set Ton 4150 70000 2905.00 

Bifurcation (ASTM A 517 Gr. F ) - 2 Sets Ton 250 77000 192.50 

19 Tail race gates & hoist 

Gate (Fixed Wheel type) 5.0m x 5.0m - 1 Ton 13 60000 7.80 

Nos. 


Rope drum hoist 20T Cap. -1 Set Ton 7 100000 7.00

180 



Hoist platform and trestle - 1 Sets Set 7 50000 3.50 

20 Instruments and Remote Control Set 1 5000000 50.00 

21 D G Set 312.5 KVA Set 1 1500000 15.00 

22 Optical fiber cable 8 Km (approx) long for 

connecting dam I & dam II control systems 

Set 1 2500000 25.00 

Sub 

Total 

4402.10 

23 Spare parts & contingency (5% of total 

cost) 

5% 220.11 

Total 4622.21 

Add for Works Tax and Surcharge 2% 92.44 

Grand Total (Dam-II) 4714.65 

Grand Total (Dam-I + Dam-II) 6102.45

K-BUILDINGS 

Sl No Description Plinth Area 

(Sqm). 

1.0 Residential Buildings 

1.1 Residential permanent 

buildings 

Service Charges @ 31% 

1.2 Residential temporary 

buildings 

Service Charges @ 27% 

Total (Residential) 

2.0 Non-Residential Buildings 

2.1 Non residential permanent 

buildings 

181 



Rs. In lakhs 

Rate Unit Amount 

10630.5 0.075 Sqm 797.29 

247.16 

10330.5 0.065 Sqm 671.48 

181.30 

20961 1897.23 

12765 0.065 Sqm 829.73 

Service Charges @ 22.5% 

186.69 

2.2 

Non residential and other 

purposes temporary buildings 

(Sl No. 1,3&4) 

14110 0.055 Sqm 776.05 

Service Charges @ 20.5% 

159.09 

Total( Non-Residential) 26875 1951.55 

Total(1+2) 47836 3848.78 

Add works Tax @ 2% 76.98 

Grand Total 3925.76

S. 

No 

O-MISCELLANEOUS 

182 



Rs. In lakhs 

Description Unit Quantity Rate Amount 

1 CAPITAL COST 

1.1 Purchase of Diesel Generator Sets 

(50 KVA) including anciliary 

equipments etc. 

1.2 Cost of transmission line for 

construction power 

1.3 Water Supply, purification & 

distribution arrangements including 

purchase of water tankers,filters, cost 

of tanks & chlorination. 

1.4 Providing sewage disposal and storm 

water drains in office and residential 

complexes. 

1.5 Providing & fixing of fire fighting 

equipments. 

Nos 8 5 40.00 

Km 60 10 600.00 

LS 50.00 

LS 60.00 

LS 30.00 

1.6 Providing telephone, Telegraph LS 30.00 

1.7 

office, Post office and Wireless 

equipments. 

Providing hospital equipments. LS 40.00 

1.8 Construction of children park and 

welfare centres for officials and 

LS 40.00 

labourers. 

1.9 Furnishing and equipping of rest 

houses and field hostels of officers 

and staff. 

1.1 Purchase of furniture and other 

articles for labour welfare centres 

and clubs and schools. 

1.1 Purchase of equipment for quality 

control/field Laboratories 

LS 30.00 

LS 30.00 

LS 25.00 

Sub Total Item 1 975.00 

2 MAINTENANCE & SERVICE 

CHARGES OF 

2.1 R&M of Diesel Generator sets 4 Nos 5 16 80.00

Nos. for 5 years. 

2.2 R&M of Transmission line for 5 

years. 

2.3 R&M of water supply facilities to the 

staff and labour colonies for 5 years 

183 



km 60 2.50 150.00 

LS 30.00 

2.4 R&M of sanitation and drainage 

facilities for office and residential 

complex and labour colonies. 

LS 15.00 

2.5 R&M of fire fighting equipments. LS 10.00 

2.6 Maint. of telecommunication system 

and post offices. 

LS 30.00 

2.7 R&M of hospitals. LS 75.00 

2.8 Maint. of parks and welfare centres, 

clubs and school. 

LS 15.00 

2.9 R&M of Rest houses and field 

hostels. 

2.10 R&M of research & quality control 

laboratories 

2.11 Labour welfare compensation and 

retrenchment benefits. 

LS 15.00 

LS 10.00 

LS 50.00 

2.12 Providing Security & Policing LS 300.00 

2.13 R&M of Inspection vehicles and 

staff cars (50 nos) for 5 year 

Nos 50*5 2.5 625.00 

2.14 R&M of school buses, Ambulance 

Car etc. (10 nos) for for 5year 

3.0 MISCELLANEOUS 

3.1 Foundation stone laying ceremony, 

inaguration and visit of Dignitaries. 

Nos 10*5 2.0 100.00 


LS 15.00 

3.2 Railway siding LS 30.00 

3.3 Installation and maintenance of LS 24.00 

Petrol/Diesel Pumps 

3.4 Providing anti malarial measures LS 10.00 

3.5 Procurement of technical leterature. LS 5.00 

3.6 Model Exhibits LS 15.00 

3.7 Canteen facilities and co-operative LS 30.00 

stores. 

3.8 Photographic and Cinemagraphic 

equipment and their maintenance 

LS 20.00

184 



3.9 Group insurance LS 30.00 

3.10 Publication and pamplets LS 5.00 

3.11 Creches LS 5.00 

3.12 Compensation for accident LS 20.00 

3.13 Training of personnels aboard LS 25.00 

includig study course and visit 

3.14 Award to workers LS 20.00 


Grand Total Item (1+2+3) 2734.00

S. 

No. 

Q-Spl T&P for Infrastructure Development 

Description of equipment Quantity 

(Nos.) 

185 



Rate 

(Rs in 

Lacs) 

Amount 

(Rs in 

Lacs) 

1 Hydraulic Excavator, 1.0 cum. 1 50.00 50.00 

2 Loader cum Excavator, 1.0/0.25 cum. 1 18.00 18.00 

3 Front end loader 1.5 -2.0 cum 1 30.00 30.00 

4 Crawler Dozer, 100 FHP 2 50.00 100.00 

5 Crawler Dozer, 200 FHP with ripper 1 85.00 85.00 

6 Wheel Dozer, 300 FHP 1 95.00 95.00 

7 Motor Grader, 145 FHP 1 60.00 60.00 

8 Air Track/Wagon Drill 2 15.00 30.00 

9 Jack Hammer/Pavement Breaker 5 0.35 1.75 

10 Diamond Core Drill (Mechanical) 2 15.00 30.00 

11 Diamond Core Drill (Hyd) 1 60.00 60.00 

12 Compressed Air(cfm) 2000 0.0125 25.00 

13 Rock splitter 1 10.00 10.00 

14 Hyd. Rock breaker 

(Mounted on 20 t excavator) 

1 60.00 60.00 

15 Mobile Crane, 10 t Pick & Carry 1 10.00 10.00 

16 Mobile Crane, 20 t (Rough terrain) 1 60.00 60.00 

17 Road Roller, 8/10 t 2 10.00 20.00 

18 Concrete Mixer, 14/10 cft 1 1.50 1.50 

19 Concrete Mixer, 28 NT 1 4.00 4.00 

20 Dewatering Pump L.S 20.00 20.00 

21 Tipper 4.5/6.0 cum. 5 9.00 45.00 

22 Truck, 10 t 5 7.50 37.50 

23 Low Bed Tractor Trailor, 30 t 1 45.00 45.00 

24 Explosive Van, 10 t 1 10.00 10.00 

25 Water Tanker/Sprinkler, 10 KL 2 12.00 24.00 

26 Petrol/Diesel Tanker, 10 KL 2 12.00 24.00 

27 Bus/Mini Bus 5 8.00 40.00 

28 Car/MUV 4 4.50 18.00 

29 Jeep (Petrol/Diesel) 20 4.50 90.00 

30 Ambulance 2 8.00 16.00 

31 Workshop Equipment L.S. 25.00 25.00

186 



32 Fire Tender 1 15.00 15.00 

33 Recovery Van 1 5.00 5.00 

34 Pick up Van/L.C.V 2 5.00 10.00 

35 Snow Cutter 2 50.00 100.00 

1274.75

S. 

No. 

Q-Spl T&P for Infrastructure Development 

Description of equipment Quantity 

(Nos.) 

187 



Rate 

(Rs in 

Lacs) 

Rs. In Lakh 

Amount 

(Rs in 

Lacs) 

1 Hydraulic Excavator, 1.0 cum. 1 50.00 50.00 

2 Loader cum Excavator, 1.0/0.25 cum. 1 18.00 18.00 

3 Front end loader 1.5 -2.0 cum 1 30.00 30.00 

4 Crawler Dozer, 100 FHP 2 55.00 110.00 

5 Crawler Dozer, 200 FHP with ripper 1 85.00 85.00 

6 Wheel Dozer, 300 FHP 1 95.00 95.00 

7 Motor Grader, 145 FHP 1 60.00 60.00 

8 Air Track/Wagon Drill 2 15.00 30.00 

9 Jack Hammer/Pavement Breaker 5 0.35 1.75 

10 Diamond Core Drill (Mechanical) 2 15.00 30.00 

11 Diamond Core Drill (Hyd) 1 60.00 60.00 

12 Compressed Air(cfm) 2000 0.0125 25.00 

13 Rock splitter 1 10.00 10.00 

14 Hyd. Rock breaker 

(Mounted on 20 t excavator) 

1 60.00 60.00 

15 Mobile Crane, 10 t Pick & Carry 1 10.00 10.00 

16 Mobile Crane, 20 t (Rough terrain) 1 60.00 60.00 

17 Fork lift, 5t 1 15.00 15.00 

18 Fork lift, 8/10t 1 25.00 25.00 

19 Road Roller, 8/10 t 2 10.00 20.00 

20 Concrete Mixer, 14/10 cft 1 1.50 1.50 

21 Concrete Mixer, 28 NT 1 4.00 4.00 

22 Dewatering Pump L.S 20.00 20.00 

23 Tipper 4.5/6.0 cum. 5 9.00 45.00 

24 Truck, 10 t 5 8.00 40.00 

25 Low Bed Tractor Trailor, 30 t 1 45.00 45.00 

26 Submersible cutter pump 1 100.00 100.00 

27 Explosive Van, 10 t 1 10.00 10.00 

28 Water Tanker/Sprinkler, 10 KL 4 12.00 48.00 

29 Petrol/Diesel Tanker, 10 KL 2 12.00 24.00 

30 Bus/Mini Bus 5 8.00 40.00

188 



31 Car/MUV 4 4.50 18.00 

32 Jeep (Petrol/Diesel) 25 4.50 112.50 

33 Ambulance 2 8.00 16.00 

34 Workshop Equipment L.S. 25.00 25.00 

35 Fire Tender 1 15.00 15.00 

36 Recovery Van 1 5.00 5.00 

37 Pick up Van/L.C.V 2 5.50 11.00 

38 Snow Cutter 2 50.00 100.00 

1474.75 

DISTRIBUTION OF COST UNDER HEAD Q - SPECIAL T & P AND V - 

RECEIPT & RECOVERIES 

Cost of equipments excluding inspection 

vehicles 

(Rs. In lakhs) 

Cost Q R&R 

1273.25 318.31 238.73 

Cost of inspection vehicles 201.50 201.50 40.30 

Provision under head Q - Spl. T&P 519.81 

Recoveries to be shown under V- Receipt 

and Recoveries 

279.03

R - COMMUNUCATION 

189 



S. 

No. Description Unit Quantity Rate Amount 

Rs. In lakhs 

1 Proposed new roads 

Approach road to dam-I DT, Top of 

Dam Km 15 80.00 1200.00 

Approach road to dam -II, DT, Top of 

Dam Km 6 80.00 480.00 

Approach road to power house site/TRT Km 2 80.00 160.00 

Realignment of Existing road due to 

submergence Km 5 80.00 400.00 

Switch yard Km 1 80.00 80.00 

Surgeshaft, Adit I,II,III Km 9 80.00 720.00 

Colony Roads Km 6 80.00 480.00 

2 Proposed new bailey bridges Cl 30 

At dam -I m 30 2.25 67.50 

At dam -II m 30 2.25 67.50 

3 Proposed Culverts 

Culverts (4 nos) 15m to 20m each m 80 1.00 80.00 

4 

Upgradation/ Improvement of Roads & 

Bridges 

Upgradation of Bridge across the Zemu 

Chu m 40 3.00 120.00 

Upgradation of road to Dam-II Km 4 60.00 240.00 

Total 4095.00 

Add works Tax @ 2% 81.90 

Grand Total 4176.90

S. 

No. 

V - RECEIPT & RECOVERIES 

190 



Item Amount 

(Rs. In Lakhs) 

1. Recovery from the Sale of Equipments 279.03 

2. Recovery from Resale of DG Sets 8.00 

3. Recovery from Temporary Building 268.19 

Total 555.22

COST ESTIMATE OF E&M WORKS 

Generator, Turbine and Accessories 

191 



S.No. Item Particulars Qty Unit Rate Amount Excise Duty* 

Total 

(Rs Rate % Amount (Rs 

Lakhs) 

Lakhs) 

1 2 3 3(a) 4 5 6 7 5+7 

1 (a) Generating units and 

Bus Ducts 4 X 80 MW, 

300 rpm, Head 576.85 

meters 

2 Step up transformer 

11/400 KV, 33MVA, 

single phase bank 

4 no. 4000 

Rs/KW 

13 no. 260 

Rs/KVA 

12800.00 16 2048.00 14848.00 

1115.4 16 178.464 1293.864 

3 Auxiliary Electrical 

Equipment for Power 

Stations (Except 

Transformer) (5% of item 

1) 

640 16 102.4 742.40 

4 Auxiliary Equipment & 

Services for Power stations 

(5% of Item 1) 

640 16 102.4 742.40 

XLPE Cable (220 kV) 2750 m 0 Rs/m 0.00 16 0.00 0.00 

5 

XLPE Cable termination 

Kit 

Switchyard (400KV) 7 

6 Spares (5% of item 1 and 

3% of item 2 to 5 ) 

20 no. 0 each 0.00 16 0.00 0.00 

250 1750.00 16 280.00 2030.00 

bays lakhs/bay 

640 124.36 764.36 16 122.30 886.66 

7 Subtotal(1-6) 20543.32 

8 Central Sales tax** 4% of 

item 7 

708.39 821.73 

9 Transportation & 

Insurance 6% of item 7 

1232.60 

10 Erection & commissioning 

8% of item 7 except spares 

1572.53 

11 Subtotal (7-10) 

Total of FC (XLPE Cable 

24170.19 

12 and Termination kit) in 

INR (As per Annexure-I) 

3093.08

13 

14 

15 

16 

17 

18 

Custom Duty @22% of 

item 12 

Marine frieght and 

insurance @6% Approx of 

12 

Inland Frieght and 

insurance 6% of item 12 

Erection & commissioning 

8% of item 12 excluding 

spares 

Subtotal of FC ( item 12- 

16 in INR) 

Subtotal of item no 

11+17(Foreign plus indian 

component) 

19 Establishment, 

Contingency, other 

charges 11% of Item 18 

Excluding duties 

GRAND TOTAL (In 

Lakhs) 

included 

in above 

item 12 

192 



185.59 

185.59 

241.39 

3705.65 

27875.84 

2226.95 

30102.79 

Annex-I 

Feb 2004 price level 

S.No. 

Item Particulars Qty Rate Amount 

Custom Duty* 

Amount'( 

Total 

( Lakhs 

Lakhs (Lakhs 

( USD) USD) Rate% USD) USD) 

1 2 3 4 5 6 7 5+7 

2 

XLPE Cable (400 kV) 6500 m 

700 

USD/m 45.50 22 10.01 55.51 

3 

XLPE Cable termination 

Kit 26 no. 35000 9.10 22 2.00 11.10 

4 

Spares for above @ 3% of 

2 1.37 22 0.30 1.67 

Total 68.28 

*Custom duty in case of imported Items 

**Not applicable for Imported Items 

1 USD conversion rate as on 23/02/04= Rs. 45.300

Power Evacuation system 

193 



S.No. Item Particulars Qty Rate Amount Excise Duty* 

Total 

(Rs (Rs Rate Amount (Rs 

Lakhs) Lakhs) 

Lakhs) 

1 2 3 4 5 6 7 5+7 

1 1 no 400kV Double Circuit 

line (of approximately 30 

kms) 

2 km 46 

lakhs/km 

92.00 16 14.72 106.72 

2 Spares ( 3% of 1) 2.76 16 0.4416 3.20 

3 Subtotal(1) 109.92 

4 Central Sales tax 4% of 

item 3 

3.79 4.40 

5 Transportation & 

Insurance 6% of item 3 

6.60 

7 Erection & commissioning 

8% of item 3 except spares 

8 Subtotal(2) 129.45 

9 Establishment, 

Contingency, other 

charges 11% of Item 3 

excluding duties 

10.42 

GRAND TOTAL (In 

Lakhs) 

8.54 

139.87



CHAPTER – XIII 

ECONOMIC EVALUATION

13.1 GENERAL 

CHAPTER – XIII 

ECONOMIC EVALUATION 

194 



The Project has been contemplated as a run-off the river scheme on river Teesta 

/Zemu chu. The project is estimated to cost Rs. 1090.88 crores excluding IDC at 

June 2003 Price Level. Sale price of energy generated at powerhouse bus bars has 

been worked out as 2.05 Rs. per unit (Table 13.2) & Rs. 1.80 per unit without free 

power to home state (Table 13.2-A). 

13.2 ECONOMIC JUSTIFICATION: 

The energy generation of the project with an installed capacity of 4 X 80 MW has 

been estimated at 1298.12 MU in a 90% dependable year. 

13.3 COST ESTIMATES AND PHASING OF EXPENDITURES 

The cost of construction of the project has been estimated at June 2003 price level 

with a construction schedule of 6.5 years including 1.5 years for Infrastructure works. 

The estimated Present Day Cost of the project is Rs. 1090.88 Crores without IDC at 

June 2003 Price level. 

13.4 PHASING OF EXPENDITURE 

The phasing of expenditure has been worked out on the basis of anticipated 

construction programme. 

The phasing of expenditure without IDC for the present cost is shown as below:

Year Estimated Cost at June 2003 P.L. 

(Rs. in Crores) 

1 st 43.64 

2 nd 98.18 

3 rd 

195 

141.81 

4 th 185.45 

5 th 272.72 

6 th 207.27 

6.5 th 141.81 

Net Cost 1090.88 

13.5 INTEREST DURING CONSTRUCTION (IDC) 



Based upon above phasing of expenditure the interest during construction (IDC) have 

been calculated with 70:30 debt equity ratio and 10.0% interest on loan. (Table 13.1) 

The estimated IDC with estimated present cost is Rs 115.71Crores 

13.6 COST OF ENERGY GENERATION 

The cost of energy generation has been calculated for the annual energy generation in 

a 90% dependable year based upon following assumptions. 

1. Debt-equity ratio 70 : 30 

2. Annual interest rate on loan 10.0% 

3. Return on equity 16% 

4. Annual interest rate on working capital 10.0% 

5. O&M Charges 1.5% of Project Cost 

6. Free power to Home State 12% of the energy 

available after losses

196 



7. Depreciation considered 1/12 th of loan amount 

during loan repayment 

period. 

The levellised tariff of the Project at present day cost works out to be Rs. 1.66 Per Unit 

with free power to home state(Table 13.3) & Rs 1.46 per unit without free power to 

home state . (Table 13.3-A).

197 


Teesta (I) HE Project (4 x 80MW) 

STATEMENT SHOWING IDC CALCULATION AT PRESENT DAY COST (JUNE 2003 LEVEL) 

PRESENT DAY COST 1090.88 Crs. 

Civil Works 788.45 Crs. Electrical Works 301.03 Crs. 

INTEREST RATE PER ANNUM 10% Transmission cost 1.40 Crs. 

(Rs. in Crs.) 

Present Day Amount Receivable I.D.C Loan Outstanding Amount Receivable 

Year Cost Equity Loan at the end of Equity Loan 

year (for the year) 

1 2 3 4 5 6 7 8 

1 43.64 43.64 43.64 

2 98.18 98.18 98.18 

3 141.81 141.81 141.81 

4 185.45 78.35 107.10 3.09 110.19 78.35 110.19 

5 272.72 272.72 24.66 407.57 297.38 

6 207.27 207.27 51.12 665.96 258.39 

6.5 141.81 141.81 36.84 844.61 178.66 

Total 1090.88 361.98 728.90 115.71 361.98 844.61 

IDC 115.71 Crs. Equity 361.98 Crs. 

Net cost of the project 1206.59 Crs. Loan 844.61 Crs. 

Table-13.1

198 



TABLE-13.2 

UNIT COST OF ENERGY AT BUS BAR AT CURRENT PRICE LEVEL 

(June 2003 P.L.) 

(Based on 16% return on equity & 10% interest on loan, 10% interest on working capital) 

1 Installed capacity 320 MW 

2 Cost of the Project (Net) Rs. 1090.88 Crores 

3 Interest During Construction Rs. 115.71 Crores 

4 Total Cost of Project 

(Including IDC) 

Rs. 1206.59 Crores 

a) Equity 30% Rs. 361.98 Crores 

b) Loan 70% Rs. 844.61 Crores 

5 Annual Energy Generation 

0.7% As Auxiliary Consumption of 

1298.12 MU 

6 No. 5 0.70% 9.09 MU 

7 Energy Available After Auxiliary Consumption 1289.03 MU 

8 0.5% As Transformer Loss of No. 7 

Energy Available After Transformer 

0.50% 6.45 MU 

9 Loss 1282.59 MU 

10 Free Power to Home State 

Energy Available After Allowing 

12% 153.91 MU 

11 Free Power 1128.68 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 80.94 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

70.38 Crores 

SUB-TOTAL 151.32 Crores 

B) Energy Charges 

a) O&M Charges 1.50% 18.10 Crores 

b) Return on Equity 16.00% 57.92 Crores 


c) Interest on Working Capital 10.00% 4.01 Crores 

I) O&M Charges for 1 month 1.51 

II) 2 Months Average Billing 38.56 

TOTAL Rs. 231.34 Crores 

13 Sale Price at Bus Bar/Unit 2.05 Rs. 

14 Cost of Generation at Bus Bar/Unit 1.35 Rs. 

(Without Allowing Free Power to Home State and Return on Equity) 

Note : This unit rate is excluding water cess, income tax incentive, penalties etc.

199 



TABLE-13.2 A 

UNIT COST OF ENERGY AT BUS BAR AT CURRENT PRICE LEVEL 

(June 2003 P.L.) WITHOUT FREE POWER TO HOME STATE 

(Based on 16% return on equity & 10% interest on loan, 10% interest on working capital) 

1 Installed capacity 320 MW 

2 Cost of the Project (Net) Rs. 1090.88 Crores 

3 Interest During Construction Rs. 115.71 Crores 

4 Total Cost of Project 

(Including IDC) 

Rs. 1206.59 Crores 

a) Equity 30% Rs. 361.98 Crores 

b) Loan 70% Rs. 844.61 Crores 

5 Annual Energy Generation 1298.12 MU 

6 0.7% As Auxiliary Consumption of No. 5 0.70% 9.09 MU 

7 Energy Available After Auxiliary Consumption 1289.03 MU 

8 0.5% As Transformer Loss of No. 7 0.50% 6.45 MU 

9 Energy Available After Transformer Loss 1282.59 MU 

10 Free Power to Home State 

Energy Available After Allowing Free 

0% 0.00 MU 

11 Power 1282.59 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 80.94 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

70.38 Crores 


B) Energy Charges 

a) O&M Charges 1.50% 18.10 Crores 

b) Return on Equity 16.00% 57.92 Crores 


c) Interest on Working Capital 10.00% 4.01 Crores 

I) O&M Charges for 1 month 1.51 

II) 2 Months Average Billing 38.56 

TOTAL Rs. 231.34 Crores 

13 Sale Price at Bus Bar/Unit 1.80 Rs. 

14 Cost of Generation at Bus Bar/Unit 1.35 Rs. 

(Without Allowing Free Power to Home State and Return on Equity) 

Note : This unit rate is excluding water cess, income tax incentive, penalties etc.

TEESTA-I H. E. PROJECT, SIKKIM, (4 X 80 MW) 

CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION 

200 



Table 13.3 

Annual Generation in a 90% dependable 1298.12 MU O&M Charges 1.50% 

Annual Generation after allowing losses & free Rate of increase of O&M Charges after 1st Year (Compounded) 6% 

power to home state in a 90% dependable year 1128.68 MU Interest rate on Loan 10.0% 

Total cost including IDC Rs. 1206.59 Crores Interest rate on Working Capital 10.00% 

Equity 30% Rs. 361.98 Crores Return on Equity 16% 

Loan 70% Rs. 844.61 Crores Discounting rate 12% 

Year Capacity Charges Charges Per Unit Discounting Discounted 

Out- (Rs.in Cr.) (Rs.in Cr.) (Rs. per Unit) Factor Tariff 

standing Interest Depre- Total Return O&M Interest on Working Capital Total Capacity Energy Total (Paisa per 

O&M 2 months 

Loan(Rs.in 

on 

for1 Average 

Cr.) on loan ciation 

equity Charges month Billing Interest charges charges Unit) 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

1 844.61 80.94 70.38 151.33 57.92 18.10 1.51 38.56 4.01 80.02 1.34 0.71 2.05 1.0000 2.05 

2 774.23 73.90 70.38 144.29 57.92 19.18 1.60 37.55 3.91 81.02 1.28 0.72 2.00 0.8929 1.78 

3 703.84 66.87 70.38 137.25 57.92 20.34 1.69 36.55 3.82 82.08 1.22 0.73 1.94 0.7972 1.55 

4 633.46 59.83 70.38 130.21 57.92 21.56 1.80 35.57 3.74 83.21 1.15 0.74 1.89 0.7118 1.35 

5 563.08 52.79 70.38 123.17 57.92 22.85 1.90 34.60 3.65 84.42 1.09 0.75 1.84 0.6355 1.17 

6 492.69 45.75 70.38 116.13 57.92 24.22 2.02 33.64 3.57 85.70 1.03 0.76 1.79 0.5674 1.01 

7 422.31 38.71 70.38 109.10 57.92 25.67 2.14 32.69 3.48 87.07 0.97 0.77 1.74 0.5066 0.88 

8 351.92 31.67 70.38 102.06 57.92 27.21 2.27 31.77 3.40 88.53 0.90 0.78 1.69 0.4523 0.76 

9 281.54 24.63 70.38 95.02 57.92 28.85 2.40 30.85 3.33 90.09 0.84 0.80 1.64 0.4039 0.66 

10 211.15 17.60 70.38 87.98 57.92 30.58 2.55 29.95 3.25 91.74 0.78 0.81 1.59 0.3606 0.57 

11 140.77 10.56 70.38 80.94 57.92 32.41 2.70 29.07 3.18 93.51 0.72 0.83 1.55 0.3220 0.50 

12 70.38 3.52 70.38 73.90 57.92 34.36 2.86 28.21 3.11 95.38 0.65 0.85 1.50 0.2875 0.43 

13 10.49 10.49 57.92 36.42 3.03 17.82 2.09 96.42 0.09 0.85 0.95 0.2567 0.24 

14 10.49 10.49 57.92 38.60 3.22 18.19 2.14 98.66 0.09 0.87 0.97 0.2292 0.22 

15 10.49 10.49 57.92 40.92 3.41 18.59 2.20 101.04 0.09 0.90 0.99 0.2046 0.20 

16 10.49 10.49 57.92 43.37 3.61 19.01 2.26 103.55 0.09 0.92 1.01 0.1827 0.18 

17 10.49 10.49 57.92 45.98 3.83 19.45 2.33 106.22 0.09 0.94 1.03 0.1631 0.17 

18 10.49 10.49 57.92 48.74 4.06 19.92 2.40 109.05 0.09 0.97 1.06 0.1456 0.15 

19 10.49 10.49 57.92 51.66 4.31 20.42 2.47 112.05 0.09 0.99 1.09 0.1300 0.14 

20 10.49 10.49 57.92 54.76 4.56 20.95 2.55 115.23 0.09 1.02 1.11 0.1161 0.13 

21 10.49 10.49 57.92 58.05 4.84 21.51 2.64 118.60 0.09 1.05 1.14 0.1037 0.12 

22 10.49 10.49 57.92 61.53 5.13 22.11 2.72 122.17 0.09 1.08 1.18 0.0926 0.11 

23 10.49 10.49 57.92 65.22 5.43 22.74 2.82 125.95 0.09 1.12 1.21 0.0826 0.10 

24 10.49 10.49 57.92 69.13 5.76 23.41 2.92 129.97 0.09 1.15 1.24 0.0738 0.09 

25 10.49 10.49 57.92 73.28 6.11 24.12 3.02 134.22 0.09 1.19 1.28 0.0659 0.08 

26 10.49 10.49 57.92 77.68 6.47 24.87 3.13 138.73 0.09 1.23 1.32 0.0588 0.08 

27 10.49 10.49 57.92 82.34 6.86 25.67 3.25 143.51 0.09 1.27 1.36 0.0525 0.07 

28 10.49 10.49 57.92 87.28 7.27 26.51 3.38 148.57 0.09 1.32 1.41 0.0469 0.07 

29 10.49 10.49 57.92 92.52 7.71 27.41 3.51 153.94 0.09 1.36 1.46 0.0419 0.06 

30 10.49 10.49 57.92 98.07 8.17 28.35 3.65 159.64 0.09 1.41 1.51 0.0374 0.06 

31 10.49 10.49 57.92 103.95 8.66 29.36 3.80 165.67 0.09 1.47 1.56 0.0334 0.05 

32 10.49 10.49 57.92 110.19 9.18 30.43 3.96 172.06 0.09 1.52 1.62 0.0298 0.05 

33 10.49 10.49 57.92 116.80 9.73 31.56 4.13 178.84 0.09 1.58 1.68 0.0266 0.04 

34 10.49 10.49 57.92 123.81 10.32 32.75 4.31 186.03 0.09 1.65 1.74 0.0238 0.04 

35 10.49 10.49 57.92 131.24 10.94 34.02 4.50 193.65 0.09 1.72 1.81 0.0212 0.04 

TOTAL 9.1566 15.23 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax etc. Levellised Tariff =(B)/(A) 1.66

CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION 

WITHOUT FREE POWER TO HOME STATE 

201 


Teesta(I)HE Project (4 x 80 MW) 

Table 13.3A 

Annual Generation in a 90% dependable year 1298.12 MU O&M Charges 1.50% 

Annual Generation after allowing losses Rate of increase of O&M Charges after 1st Year (Compounded) 6% 

in a 90% dependable year 1282.59 MU Interest rate on Loan 10.0% 

Total cost including IDC Rs. 1206.59 Crores Interest rate on Working Capital 10.00% 

Equity 30% Rs. 361.98 Crores Return on 16% 

Loan 70% Rs. 844.61 Crores Discounting rate 12% 

YEAR CAPACITY CHARGES CHARGES PER UNIT Discounting Discounted 

Out- (Rs.in Cr.) (Rs.in Cr.) (Rs. per Unit) Factor Tariff 

standing Interest Depre- Total Return O&M Interest on Working Capital Total Capacity Energy Total (Paisa per 

Loan(Rs.in on loan ciation on Charges O&M 2 months Interest charges charges Unit) 

Cr.) 

equity 

for1 Average 

month Billing 

1 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

35 

2 

844.61 

774.23 

703.84 

633.46 

563.08 

492.69 

422.31 

351.92 

281.54 

211.15 

140.77 

70.38 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

3 

80.94 

73.90 

66.87 

59.83 

52.79 

45.75 

38.71 

31.67 

24.63 

17.60 

10.56 

3.52 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

0.00 

4 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

70.38 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

5 

151.33 

144.29 

137.25 

130.21 

123.17 

116.13 

109.10 

102.06 

95.02 

87.98 

80.94 

73.90 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

10.49 

6 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

57.92 

7 

18.10 

19.18 

20.34 

21.56 

22.85 

24.22 

25.67 

27.21 

28.85 

30.58 

32.41 

34.36 

36.42 

38.60 

40.92 

43.37 

45.98 

48.74 

51.66 

54.76 

58.05 

61.53 

65.22 

69.13 

73.28 

77.68 

82.34 

87.28 

92.52 

98.07 

103.95 

110.19 

116.80 

123.81 

131.24 

8 

1.51 

1.60 

1.69 

1.80 

1.90 

2.02 

2.14 

2.27 

2.40 

2.55 

2.70 

2.86 

3.03 

3.22 

3.41 

3.61 

3.83 

4.06 

4.31 

4.56 

4.84 

5.13 

5.43 

5.76 

6.11 

6.47 

6.86 

7.27 

7.71 

8.17 

8.66 

9.18 

9.73 

10.32 

10.94 

9 

38.56 

37.55 

36.55 

35.57 

34.60 

33.64 

32.69 

31.77 

30.85 

29.95 

29.07 

28.21 

17.82 

18.19 

18.59 

19.01 

19.45 

19.92 

20.42 

20.95 

21.51 

22.11 

22.74 

23.41 

24.12 

24.87 

25.67 

26.51 

27.41 

28.35 

29.36 

30.43 

31.56 

32.75 

34.02 

10 

4.01 

3.91 

3.82 

3.74 

3.65 

3.57 

3.48 

3.40 

3.33 

3.25 

3.18 

3.11 

2.09 

2.14 

2.20 

2.26 

2.33 

2.40 

2.47 

2.55 

2.64 

2.72 

2.82 

2.92 

3.02 

3.13 

3.25 

3.38 

3.51 

3.65 

3.80 

3.96 

4.13 

4.31 

4.50 

11 

80.02 

81.02 

82.08 

83.21 

84.42 

85.70 

87.07 

88.53 

90.09 

91.74 

93.51 

95.38 

96.42 

98.66 

101.04 

103.55 

106.22 

109.05 

112.05 

115.23 

118.60 

122.17 

125.95 

129.97 

134.22 

138.73 

143.51 

148.57 

153.94 

159.64 

165.67 

172.06 

178.84 

186.03 

193.65 

12 

1.18 

1.12 

1.07 

1.02 

0.96 

0.91 

0.85 

0.80 

0.74 

0.69 

0.63 

0.58 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

0.08 

13 

0.62 

0.63 

0.64 

0.65 

0.66 

0.67 

0.68 

0.69 

0.70 

0.72 

0.73 

0.74 

0.75 

0.77 

0.79 

0.81 

0.83 

0.85 

0.87 

0.90 

0.92 

0.95 

0.98 

1.01 

1.05 

1.08 

1.12 

1.16 

1.20 

1.24 

1.29 

1.34 

1.39 

1.45 

1.51 

14 

1.80 

1.76 

1.71 

1.66 

1.62 

1.57 

1.53 

1.49 

1.44 

1.40 

1.36 

1.32 

0.83 

0.85 

0.87 

0.89 

0.91 

0.93 

0.96 

0.98 

1.01 

1.03 

1.06 

1.10 

1.13 

1.16 

1.20 

1.24 

1.28 

1.33 

1.37 

1.42 

1.48 

1.53 

1.59 

15 

1.0000 

0.8929 

0.7972 

0.7118 

0.6355 

0.5674 

0.5066 

0.4523 

0.4039 

0.3606 

0.3220 

0.2875 

0.2567 

0.2292 

0.2046 

0.1827 

0.1631 

0.1456 

0.1300 

0.1161 

0.1037 

0.0926 

0.0826 

0.0738 

0.0659 

0.0588 

0.0525 

0.0469 

0.0419 

0.0374 

0.0334 

0.0298 

0.0266 

0.0238 

0.0212 

16 

1.80 

1.57 

1.36 

1.18 

1.03 

0.89 

0.77 

0.67 

0.58 

0.51 

0.44 

0.38 

0.21 

0.20 

0.18 

0.16 

0.15 

0.14 

0.12 

0.11 

0.10 

0.10 

0.09 

0.08 

0.07 

0.07 

0.06 

0.06 

0.05 

0.05 

0.05 

0.04 

0.04 

0.04 

0.03 

TOTAL 9.1566 13.40 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax etc. Levellised Tariff =(B)/(A) 1.46



PLATES

TALEM H.E PROJECT 

R.B.L- EL. 3630 

F.R.L- EL. 3675 

88° 34' 

TEESTA RIVER 

88° 32' 

3800 

4000 

4000 

DEUTHANG 

88° 33' 

KALEP 

27° 52' 

4400 

3648 

4200 

4605 

YATHAOG 

27° 51' 

4000 

CHOTENGANG 

GOMA CHU 

SAMDONG 

H.R.T. H.S.SHAPE 

SWITCHYARD CHHOCHEN 

3455 

27° 50' 

TALAM 

3600 

3800 

3400 

27° 49' 

3600 

CHENTO CHU 

SHACHAM 

3249 

T.R.T 

(OUTLET LEVEL-EL. 3268) 

(GROSS HEAD - 400) 

POWER HOUSE 

SURGE SHAFT 

4600 

4000 

THOMBU 

27°48' 

4225 

H R T 

H S SHAPE 

4000 

3800 

4625 

H R T H.S SHAPE 

TEESTA H.E PROJECT (STAGE-I) 

R.B.L- EL. 3230 

F.R.L- EL. 3265 

TEESTA H.E PROJECT (STAGE-I) 

R.B.L- EL. 3230 

F.R.L- EL. 3265 

3600 

3400 

T.R.T 



CHIMAKARU 

SURGRE 

SHAFT 

3400 

3730 

LOG BRIDGE 

27°47' 

YUNGA 

POWER HOUSE 

4000 

YUGEYGO 

4250 

3400 

3600 

3600 

LACHEN H.E PROJECT 

R.B.L- EL. 2590 

F.R.L- EL. 2650 

TEESTA RIVER 

DOZAM 

3800 

4000 

27°46' 

4000 

ZEMU CHU 

4200 

2800 

ZEMA 

NARAM 

2675 

H.R.T. H.S. SHAPE 

3400 

SWITCH YARD 

3600 

ALAKHADE CHU 

3600 

4200 

5000 

27°45' 

3200 

3600 

4000 

88°30' 

4000 

3800 

PHYAKTOK 

3800 

PUCHIKANGMA 

3600 

3400 

2800 

27°44' 

GEY CHHU 

3400 

3600 

SURGE SHAFT 

MONASTERY 

LACHEN 

3400 

2600 

3600 

3200 

3000 


TENGMOCHI 

3000 

3200 

2800 

2600 

4200 

3800 

4000 

CHHATEN 

27°43' 

. 

3840 

3400 

POWER HOUSE 

M. A. T 

BENSHOI 

3200 

T.R.T 



SCALE 

0 0.65 

CHYAGA CHHU 

27°42' 

APRIL 2004 

2800 

3000 

JORPUL 

(SAMPAKANGMA) 

2600 

2400 

2800 

2600 

. 

2400 

RINJNKHENGU 

2765 

2400 

2600 

3400 

3600 

3800 

4000 

4200 

4400 

27°41' 

88°36' 

88°35' 

88°34' 

TEESTA H.E PROJECT(STAGE-II) 

R.B.L- EL. 2210 

F.R.L- EL. 2287 

1.30 1.95 2.60 3.25 KM. 

PLATE :- 01 

88°33' 

88°32' 

88°31' 

00 

F/DCE/730/01/02

ELEVATION IN METERS 

SCHEMATIC DIAGRAM SHOWING CASCADE DEVELOPMENT OF TEESTA RIVER BASIN (SIKKIM) 

4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

000 

TEESTA PROJECT 

STAGE -VI 

SALENTFEATURES:- 

1. CATCHMENT AREA 4874sqkm 

2. DISCHARGE(Dependable) 93CUMECS 

3. F.R.L. 341m. 

4. TYPE OF DAM(Conc.GravityDam) 

5. T.W.L. 253.5om. 

6. AVERAGE GROSS HEAD 84.50m. 

7. LENGTH OF TUNNEL 3.50km. 

8. FIRM POWER 55.50MW. 

9. PROPOSED INSTALLED 

CAPACITY 360MW. 

11O 

UNDER CONST.BY NHPC 


STAGE -V 


1. CATCHMENT AREA 4336sqkm 

2. DISCHARGE(Dependable) 60cumecs 

3. F.R.L. 579m. 

4. TYPE OF DAM-Conc.GravityDam 

5. T.W.L. 359.5m. 

6. AVERAGE GROSS HEAD 216.73m. 

7. LENGTH OF TUNNEL 18km. 

8. FIRM POWER 100mw. 


CAPACITY 510mw. 

100 90 80 70 


STAGE -II 


1. CATCHMENT AREA 1772sqkms 

2. DISCHARGE(Dependable)9.29cumecs. 

3. F.R.L. 2287m. 


5. T.W.L. 1592m. 

6. AVERAGE GROSS HEAD 683m. 


8. FIRM POWER 57.38mw. 




STAGE -III 


1. CATCHMENT AREA 2787sqkm. 

2. DISCHARGE(Dependable)31cumecs 

3. F.R.L. 1585m. 

4. TYPE OF DAM(Conc.GravityDam) 

5. HEIGHT OF DAM 103m. 

6. T.W.L. 779m. 


8. LENGTH OF TUNNEL 12.93m. 

9. FIRM POWER 180mw. 



60 50 

DISTANCE IN KILOMETER 


STAGE-IV 


1. CATCHMENT AREA 3859sqkms 

2. DISCHARGE(Dependable)56cumecs. 

3. F.R.L. 722m. 


5. T.W.L. 589m. 


7. LENGTH OF TUNNEL 11km. 




40 

LACHEN PROJECT 


1. CATCHMENT AREA 1604sq.km. 

2. DISCHARGE(Dependable)9.25 cumecs. 

3. F.R.L. 2650m. 


5. T.W.L. 2290m. 






30 20 


STAGE -I 



2. DISCHARGE(Dependable)10.8 cumecs. 

3. F.R.L. 3265m. 

4. TYPE OF DAM(Conc.GravityDam) 2Nos. 

5. T.W.L. 2675m. 






10 0 

4000 

3500 

3000 

2500 

2000 

1500 

1000 

500 

000 

TALEM PROJECT 



2. DISCHARGE(Dependable) 2.96 cumecs. 

3. F.R.L. 3675m. 

4. TYPE OF DAM:- Conc. Face Rockfill Dam. 

5. T.W.L. 3268m. 




9. PROPOSED INSTALLED CAPACITY 75mw. 

PLATE-02

TALEM HYDRO ELECTRIC PROJECT 

(3 X 25 MW ) 

RINGPI HYDRO ELECTRIC PROJECT 

( 2 X 35 MW ) 

RANGYONG HYDRO ELECTRIC PROJECT 

( 3 X 47 MW ) 

RUKEL HYDRO ELECTRIC PROJECT 

( 3 X 11 MW ) 

N E P A L 

LINGZA HYDRO ELECTRIC PROJECT 

( 3 X 40 MW) 

YANGSS CHHU 

RAMAM OR 

RIYONG KHOLA 

RANGBONG KHOLA 

C H I N A 

CHAUNRIKHIANG 

LAMBI 

TIKIPCHHU 

RIMBI CHHU 

T I B E T 

PHUTHUNG CHHU 

TONGSHIONG GLACIER 

TALUNG GLACIER 

CHOKCHURANG CHHU 

PREK CHHU 

KHUNGME 

RATHANG CHHU 

KALEJ KHOLA 

TINGCHEN KHANG 

RONGDUNG CHHU 

REFLI CHHU 

RISHI KHOLA 

GOMA CHHU 

RUKEL CHHU 

GEZING 

REATHOK KHOLA 

SOMBARE NAYA BAZAR 

KHORA CHHU 

LUNGMA CHHU 

UMMRAM CHHU 

RANGYONG CHHU 

RANGIT RIVER 

KAYAM CHHU 

NAMCHI 

RINGYONG CHHU 

RANGPO CHHU 

GREAT RANGIT RIVER 

NACHUNGTHANGKHA 

THANG CHHO 

NAKU CHHU 

LANGBO CHHU 

THOMPHYAK CHHU 

POKE CHHU 

LHONAK CHHU 

RINGPI CHHU 

MONMU CHHU 

RANGPHAP CHHU 

ZEMU CHHU 

TOLUNG CHHU 

RUN CHHU 

SINGTAM 

TEESTA RIVER 

MANGKHA 

SIRWANI 

RAHI CHHU 

RONGNI CHHU OR RANI K 

TEESTA RIVER 

LASHA CHHU 

KALEP 

MANGAN 

DIKCHU 

CHHU 

TEESTA RIVER 

GYAMTHANG CHHU 

GEY CHHU 

BURUM CHHU 

TEESTA RIVER 

RANGPO CHHU 

RANGPO 

TARUM CHHU 

RABOM CHHU 

RI CHHU 

RISHI KHOLA 

BAKCHA 

DIK CHHU 

YUMRHANG CHHU 

CHUNGTHANG 

GANGTOK 

RORA CHHU 

TAKCHOM CHHU 

W E S T B E N G A L 

CHAKUNG CHHU 

CHHU 

RANGLI KHOLA 

DONGKYA CHHU 

TOKLUNG CHHU 

RATE CHHU 

BYU CHHU 

SEBOZANG CHHU 

LUNGZE CHHU 

RANGPO CHHU 

C H I N A 

T I B E T 

B H U T A N 

PANAN HYDRO ELECTRIC PROJECT 

(4 X 50MW) 

RONGNI STORAGE PROJECT 

( 3 X 65 MW) 

NOTES 

1. NO DIMENSION SHALL BE MEASURED FROM THIS DRAWING. 

PRE- FEASIBILITY REPORT DRAWING 

VICINITY MAP 

PLATE NO.- 6.1 

TEESTA HYDRO ELECTRIC PROJECT(STAGE-I) 

( 4 X 80 MW ) 

LACHEN HYDRO ELECTRIC PROJECT 

( 3 X 70 MW ) 

TEESTA HYDRO ELECTRIC PROJECT(STAGE-V) 

( 3 X 170 MW ) 

DIKCHU HYDRO ELECTRIC PROJECT 

( 3 X 35 MW ) 

LEGEND 

INTERNATIONAL BOUNDARY 

STATE BOUNDARY 

RIVER 

TRIBUTARY 

ROAD 

DAM SITE 

F/DCE730/01/02

27°48' 

27°47' 

27°46' 

27°45' 

5000 

LOHANAK CHU 

LOG BRIDGE 

U/S COFFER DAM 

3800 

4000 

3400 

3400 

4200 

3800 

88°30' 

4000 

4000 

DESILTING CHAMBER 

3200 

3400 

ADIT-1 

CONC. DAM I (R B L. - 3230.00) 

D.T. 6.0 M Ø H.S.SHAPE 

4625 

SILT FLUSHING TUNNEL 

D/S COFFER DAM 

88°31' 

ZEMU CHU 

3600 

ALAKHADE CHU 

4600 

4.0 M Ø H R T 

HORSE SHOE SHAPE 

YUGEYGO 4250 

15 M Ø SURGRE 

SHAFT 

3600 

DOZAM 

4 M. Ø H R T 


ADIT-2 

SWITCH YARD 

4000 

POWER HOUSE 

88°32' 

3200 

3600 

4225 

YUNGA 

ZEMA 

2675 

3000 

3600 

3400 

CHIMAKARU 

2.5 M Ø PRESSURE 

SHAFT 

M.A.T. 

2800 

TEESTA RIVER 

3400 

SHACHAM 



ADIT-2 

THOMBU 

NARAM 

88°33' 

TEESTA RIVER 

CHENTO CHU 

ADIT-1 

3730 

5.0 MØ T.R.T. H.S. SHAPE 

3200 

3400 

D.T. 6.0MØ H.S. SHAPE 

CONC.DAM II (R B L. - 3230.00) 


3400 

88°34' 

3600 


NOTES 

1. NO DIMENSION SHALL BE MEASURED FROM 

THIS DRAWING 

2. CONTOURS AND OTHER FEATURES HAVE 

BEEN TRACED FROM THE S.O.I. TOPO-SHEET 

NO. 78A/5 & 78A/9 (SCALE:- 1:50000) 


LAYOUT PLAN 


00 

F/DCE/730/01/02

27° 47' 

LOHNAK CHU 

3400 


INTAKE TUNNEL 4.5 M. Ø 

3400 

350000 

88° 30' 


(200 X 8 X 12 M.) 

SPILLWAY 5 BAYS (4.0M. X 6.0M.) 


CONCRETE DAM I (R B L. - 3230.00) 

3400 

3200 

DIVERSION TUNNEL 6.0 M Ø H.S.SHAPE 

ZEMU CHU 


2 X 3 M. D-SHAPED 

HRT 4.0 M Ø 

HORSE SHOE SHAPE

27°48' 

88°33' 

HRT 4.0 M. Ø 


3400 

INTAKE TUNNEL 4.5M. Ø 


( 200 X 8 X 12M.) 

3400 



3200 

TEESTA RIVER 

240000 

D T 6.0MØ H.S. SHAPE 

CONC. DAM II (R B L. - 3230.00) 


(2.0 X 3.0 M. D-SHAPE) 

3400 

SPILLWAY 4 BAYS (4.5 X 6.0) 

3600 

NOTES 


THIS DRAWING 



NO. 78A/9 (SCALE:- 1:50000) 


DAM-II 

LAYOUT PLAN 


00 

F/DCE/730/01/02

H.R.T. 4.0 MØ H.S. SHAPE 

(FROM DAM-I) 

27°46' 

3200 

15 M Ø SURGRE 

SHAFT 

ZEMU CHU 

88°32' 

POWER HOUSE CAVERN 

(141M. X 22M. X 40M.) 

SWITCH YARD 

( 250M. X 180M.) 

3000 

CABLE TUNNEL 

3600 

H.R.T. 4.0 MØ H.S. SHAPE 

(FROM DAM-II) 

3400 


SHAFT 

ZEMA 

2800 

3200 


M.I.V. CHAMBER 

TRANSFORMER CAVERN 

3000 

TEESTA RIVER 

T.R.T. 5.0 M Ø H.S.SHAPE 

88°33' 

NOTES 


THIS DRAWING 



NO. 78A/9 (SCALE:- 1:50000) 


POWER HOUSE AREA 

LAYOUT PLAN 


00 

F/DCE/730/01/02

FRL 3265.00 

MDDL 3260.00/3258.00 

EL 3250.00 

EL 3245.00 

TRESTLE 

EL 3270.00 

? 

? 


(200M. X 8M.X12M.) 


(2.0 M.X3.0 M. D-SHAPED) 

? 

? 

GATE OPERATION 

CHAMBER 

EL 3270.00 

EL3310 

1 250 

? ? 

HRT 4.0M.Ø H.S. SHAPE 

STEEL LINED PRESSURE SHAFT 

2.5M. Ø (2 NOS.) 

SURGE SHAFT 

15M. Ø 

ADIT TO P.S. 

3.5M.Ø D-SHAPE 

EL 3235.00 

EL. 2677.82 

C L - OF MACHINE 

MIV 

8000 

? 

? 

ADIT TO P.S. 

3.5M.Ø D-SHAPE 

22000 

? 

EL.2708.00 

BUS DUCT 

30000 

POWER HOUSE CAVERN 

14000 

EL.2689.00 

? 

TRANSFORMER CAVERN 

CABLE TUNNEL 

T.R.T. 5.0M.Ø H.S.SHAPE 

NOTES: 


APRIL 2004 

C.C. BLOCKS 

TWL 2675.00 

COFFERWALL 

WATER CONDUCTOR SYSTEM 

L-SECTION (TYPICAL) 

PLATE NO.-6.6 

1 ALL DIMENSIONS ARE IN MILLIMETERS AND LEVELS IN 

METERS.UNLESS OTHERWISE SPECIFIED. 

2 NO DIMENSION SHALL BE MEASURED FROM THIS 

DRAWING. 

F/DCE730/01/02

L10 

? 

L9 L8 L7 

PARAPET 

L6 

? 

L5 

? 

175000 

PARAPET 

L6 L5 L4 

L4 

NSL 

ANTICIPATED ROCK PROFILE 

? 

L3 

STOPLOG GANTRY 

CRANE 

L2 

L1 

RADIAL GATE 4000 X 6000 

350000 

4000(TYP.) 

S5 

50000 

S3 S2 S1 

UPSTREAM ELEVATION (DAM-I) 

S4 

3000 (TYP.) 

240000 

100000 


CRANE 

42000 

4500(TYP.) 3000 (TYP.) 

98000 

? 

R3 

L2 L1 

RADIAL GATE 4500 X 6000 

ANTICIPATED ROCK PROFILE 

? 

S4 

? 

S3 S2 S1 R1 R2 

UPSTREAM ELEVATION (DAM-II) 

? 

? 

? 

R1 

DAM TOP EL 3270.00 

R2 


R3 

NSL 

R4 

? 

R5 

125000 

R3 R4 R5 R6 

? 

R6 

NOTES: 


APRIL 2004 

? 

DAM 

UPSTREAM ELEVATION 


R7 

1 ALL DIMENSIONS ARE IN MM AND LEVELS IN 

METRES. UNLESS OTHERWISE SPECIFIED. 


THIS DRAWING. 

F/DCE730/01/02

STOPLOG GATE GROOVE 

1 

EL ±3225.00 / ±3210.00 

CREST EL. 3240.00 

RBL ±EL 3230.00 

1 


CRANE 


FRL EL. 3265.00 

MDDL EL. 3260.00/3258.00 

STEEL LINER 

GROUT CURTAIN HOLES 

? 

3500 

DAM AXIS 

8000 

ROAD 

EL. 3248.00 

R9600 

FOUNDATION 

GALLERY 

DRAINAGE HOLE 

BREAST WALL 

AIR VENT PIPE 

RADIAL GATE (4M. X 6M.) / (4.5M. X 6M.) 

HIGH PERFORMANCE CONC. 

50000/60000 

TRUNION BEAM 

? ? ? ? ? 

SPILLWAY- MAXIMUM SECTION (TYPICAL) 

1 

1 

1 

1 

12250 

7000 LONG ROCK ANCHORS 

@1500 c/c STAGGERED 

MAX. T W L 

NORMAL T W L 

CONCRETE APRON 

DAM TOP EL. 3270.00 

FRL EL. 3265.00 

MDDL EL.3260.00/ 3258.00 

EL. VARIES 

COMPACTED BACKFILL 

1 

0.1 

DAM AXIS 

8000 

? 

NON- OVERFLOW SECTION (TYPICAL) 

NOTES: 


APRIL 2004 

? ? 

DAM 


0.8 

1 ALL DIMENSIONS ARE IN MM AND LEVELS IN 

METRES UNLESS OTHERWISE SPECIFIED. 


DRAWING. 

SPILLWAY & NON-OVER FLOW 

CROSS-SECTION (TYPICAL) 

1 

F/DCE730/01/02

HRT4000 Ø 

FROM DAM-I 

32Ø 5000 LONG ROCK BOLTS/ 

ANCHORS @ 1500 c/c 

R.C.C. LINING 250 THK. 

12000 

Ø15000 

TYP. SECTION - SURGE SHAFT 

8000 

R4000 

6000 LONG 25 MMØ ROCK BOLTS/ 

ANCHORS 2000 c/c 

HRT4000 Ø 

FROM DAM-II 

32Ø 5000 LONG ROCK BOLTS / 

ANCHORS @ 2000 c/c 

1.5 

SECTION - DESILTING CHAMBER (TYPICAL) 

1 

100 THK. SHOTCRETE 

WITH WIREMESH 

100 THK. SHOTCRETE 

WITH WIREMESH 

R.C.C. LINING 750 THK. 


2500 Ø 

Ø4000 



Ø2000 

Ø4000 

TYP. SECTION - HRT 

CONC. LINING 250 THK. 

50MM THK. 

SHOTCRETE 

Ø6000 

Ø3000 

Ø6000 

TYP. SECTION - DIVERSION TUNNEL 

Ø2500 

TYP. SECTION - PRESSURE SHAFT 




ANCHORS 1000 c/c(IF REQUIRED) 

BACK FILL 750 THK. 

STEEL LINER 

50THK. 

SHOTCRETE 

CONC.LINING 250 THK. 

50/75MM THK. SHOTCRETE 

NOTE :- 

PRE-FEASIBILITY REPORT DRAWING 

TYPICAL CROSS SECTION 

OF CONSTITUENTS OF WATER 

CONDUCTOR SYSTEM & DIVERSION TUNNEL 

APRIL 2004 


1 ALL DIMENSIONS AREIN MILIMETRES AND LEVELS 

IN METRE UNLESS OTHERWISE SPECIFIED. 


DRAWING. 

00 

F/DCE/730/01/02

400KV 

BUS1 

BUS CVT-1 

400kV 

BUS-II 

BUS CVT-2 

EX. Tr. 

NGT 

UNIT -IV 

S.A. 

XLPE CABLE 

GSU Tr. 

SC PTSP 

SA 

PT 

PT 

G-IV 

UAT 

64G1 

64G2 

FUTURE 

CVT 

EX. Tr. 

NGT 

UNIT -III 

S.A. 

GSU Tr. 

SC PTSP 

SA 

PT 

PT 

G-III 

UAT 

64G1 

64G2 

TO 400KV 

FEEDER-1 

CVT 

BUS 

COUPLER 

EX. Tr. 

NGT 

UNIT -II 

S.A. 

XLPE CABLE XLPE CABLE 

GSU Tr. 

SC 

SA 

PT 

PT 

G-II 

UAT 

64G1 

64G2 

PTSP 

TO 400KV 

FEEDER-2 

CVT 

EX. Tr. 

NGT 

UNIT -I 

S.A. 

XLPE CABLE 

GSU Tr.1Ø,33 MVA 

11/ 400/ 3 KV 

UAT 

11 / 0.415KV,1000KVA 

SC 

SA 

PT 

PT 

G-I 

80 MW,11 KV 

64G1 

64G2 

PTSP 

FOR 

METERING & 

PROTECTION 

FOR 

DVR DUPLICATE 

PROTECTION 

APR, 2004 

SINGLE LINE DIAGRAM 

VED PAL KAPIL V.K.SINGH 

NH/DEM/TST-I/SLD/01 

00



ANNEXURES

1 

Annexure 4.1 

GEOLOGY OF THE AREA AROUND THE PROPOSED TEESTA 

(STAGE –I ) HYDROELECTRIC PROJECT, TEESTA BASIN, 

SIKKIM 

INTRODUCTION 

The Central Electricity Authority (CEA), with a view to fill the gap between supply 

and demand in the field of power have embarked on an exercise to assess the balance 

hydroelectric potential in the country and rank the schemes thus identified in various parts of 

the country in different river basins. As a part of this exercise, 162 schemes with probable 

installed capacity of 50,600 MW and located in various river basins spread over 16 states have 

to be taken up for preparation of Pre Feasibility Reports (PFRs) in the first phase. The 

schemes found feasible are proposed to be taken up for further development in X and XI five 

year Plans. The proposed Teesta (Stage – I) Hydroelectric Project is one such scheme 

identified in Teesta Basin in Sikkim. The Teesta (Stage – I) Hydroelectric Project is a run of 

the river scheme that envisages the construction of a diversion dam/weir across the river 

Teesta (27 o 48 ’ 15” N: 88 o 33 ’ 30” E) and Zema Chhu at (27 o 46 ’ 50” N: 88 o 29 ’ 55” E), a water 

conductor system including 4.25km + 3.5km km long twin head race tunnels, one each from 

both dam sites and a powerhouse ( 27 o 45 ’ 55” N: 88 o 32 ’ 30” E) common to both the tunnels 

with an installed capacity of 320 MW. 

REGIONAL GEOLOGY 

The area with gneissic outcrops has a rugged topography on either side of 

Zema Chhu valley, which follows a prominent E-W trending lineament. Here the 

ridges trend roughly –S & E-W. The tree lines is at an altitude 3900 m. ASL, and 

upstream of Yabuk, the Zema Glacier double snout is encountered. From the snout 

onwards, the Zema Valley is broad and ‘U’ shaped with glacial and paleoglacial 

geomorphic features. Evidences for neotectonics could be marked by dextral off sets 

(faults) of esker lines and normal faults of the eskers. Similarly, perhaps due to 

neotectonic uplift, the feeder channels to Green Lake have been diverted and hence the 

lake has dried up. 

The area comprises part of the Central Crystalline Zone. The central 

Crystalline zone comprises high grade metasediments conformably interbanded calc 

gneisses, quartzites, pelitic schists with high grade gneisses and migmatite. These are 

intruded by Tertiary Granites. Ray (1989) (also see Ravishanker et al, 1989), has 

grouped these high grade metasedimentaries into the Sikkim Group (older than the 

Daling Group) consisting of Kanchenjungha Gneiss, Darjeeling Gneiss and 

Chungthang (*Part of Bhutan) Subgroup, which were deformed and metamorphosed 

during the Mid-Late Proterozoic.

The rock types encountered in the area essentially are high grade migmatitic 

gneisses, banded gneisses and augen gneisses, and are referred to here as 

Khangchandzonga Migmatitic Gneiss (KMG). They are concordantly interbanded by 

calcsilicate gneiss. The KMG, usually mesocratic, comprise essentially of a 

garnetiferous biotite gneisses with fine sillimanite needles among the biotite flakes. 

They define a mineral lineation parallel to the strikes of the gneissosity. Alignment of 

the biotite flakes define the pervasive foliation. The leucosomes consist of garnet 

bearing quartzofeldspathic bands with less modal biotite than the melanosomes. 

Variants of KMG are augen gneisses with gneissic foliation swerving around the Kfeldspar 

augen, which usually lie flattened in the plane of foliation. These gneisses are 

considered to be paragneisses and classified as granodiorite – tonalities (Neogi, 

1998). 

High grade metasedimentaries (HGMS), which are conformably interbanded 

with the KMG consist of calc-silicate gneisses (banded diopside marble) with fine 

layers of biotite schists, a heterolithic unit and micaceous quartzites. The precursor 

sediments of these metasedimentaries varied from a calcareous to arenaceous to 

argillaceous lithofacies. These calcsilicate genisses are usually grey to buff coloured 

showing typical ribbed weathering pattern in outcrop. 

Wollastonite usually occurs at the contact zones with the calc-silicate gneiss. 

(apparently as products of both thermal and regional metamorphism). 

Calc-silicates occur around Dzema, West of Rest camp and around Green 

Lake. Felsic intrusive into the KMG and HGMS are represented by biotite 

leucogranite (with enclaves of KMG at places), tourmaline biotite leucogranite and 

biotite pegmatite. Massive sheet like intrusives of leucogranite also occur at the North 

face of Mt. Khangchendzonga. The KMG enclaves within the leucogranite intrusive 

eg at Yabuk, suggest derivation of the Leucogranite by partial fusion of the crustal 

KMG. Apart from a few boulders of fresh dolerite, no basic intrusive / amphibolite is 

observed in the area. 

STRUCTURE AND TECTONICS 

A detailed study of structure and metamorphism could not be attempted 

because of limited outcrops, hence a brief synoptic table is given correlating the 

structural phases and metamorphic episodes, the data being obtained primarily from a 

few outcrops and scanty mesosopic data. 

D2 : F2 Tight – Isoclinal folds on 

pervasive gneissosity (S1) and 

on K-feldspar prophyroclasts 

2 

M3 (thermal Metamorphism) 

Wollastonite + Idocrase + 

Grossular in calcsilicate gneiss 

were intruded by Leucogranite. 

Tertiary Event. 

M2 Syn F2 (?) 

Alm garnet prophyroblasts and 

K-feldspar lath prophyr-oblasts

and quartzofeldspatihc leucosomes. 

Not directly observed in KMG. 

This phase of deformation 

generated the pervasive 

gneissosity S’ Intrafolial 

isoclinal folds on bedding of 

quartzites which are 

concordantly interbanded with 

the KMG 

Pre D1 / M1 event ? 

3 

athwart 

M1 : Sn F1 

High grade metamorphism Sil 

– K Felspar (no primary 

muscovites) 

Anatexis and formation of 

migmatites. 

Forsterite and scapolite in 

HGMS. 

The generalized structural elements in the area can be broadly grouped under 

two categories, namely, the “Primary or non-diastrophic structures” like bedding 

plane, other primary structures include symmetric ripples and the “Diastrophic 

structures” such as planer and linear features related to deformation. The area shows 

evidences of three phases of deformation which are recorded into three distinct 

generation of folds and related structures. 

The diastrophic structures observed in the field can be broadly divided into 

two groups, viz. , Planer structures and Linear structures. 

Besides schistosity, the joint planes of different orientations and joint sets 

define a joint system in the map area. Joints are usually found to occur as families of 

fracture with more or less regular spacing in quartzites, micaceous quartzites and some 

competent schists. Most of the joint sets dip steeply to vertical Microscopic studies 

revealed the presence of micro joints within competent unit. Joints seem to show 

distinctive patterns of surface relief in the form of plume structure in massive rocks 

like greywacke etc. Replacement joints are also reported. 

Evidences of local fault movements and slips are commonly observed in the 

area. These are evidenced in the field by the presence of localised small scale fault 

planes, slip surfaces and some development of slickensides and striated surfaces with 

minor fault gouge. 

Metamorphism rocks show evidences of prograde metamorphism. Grade of 

metamorphism varies from greenschist to amphibolite facies. The lithological 

assemblages in the mapped area report low grade metapelites and metapsammites and 

high grade metasedimentaries and gneisses. Successively higher grade of 

metamorphsim is observed at higher tectonic levels. 

Evidences of retrogression are quite common in the metapelites and Central 

Crystalline Complex.

SEISMOTECTONICS AND SEISMICITY 

Seismotectonically the area under reference is located in Axial Belt of Central 

Crystalline Zones of North Sikkim. According to Narula at al (2000) the northern part 

of the area is occupied by poorly metamorphosed sequence (Tethyan) folded during 

Himalayan Orogeny. Similar tectonic pockets representing Gondwana sequence crop 

out within Rangit Window as well as lenticular tectonic wedge along the Main 

Boundary Thrust (MBT). The northern Tethyan Belt is followed successively to the 

south by high-grade complex of Central Crystallines and low-grade complex of Lesser 

Himalayan rock worked during Himalayan Orogeny. The latter packet is exposed 

within tectonic windows as well as linear belt between Main Central Thrust (MCT) 

and MBT. South of MBT the foot hill region is occupied by sequence of frontal belt 

affected by the terminal phase of the Himalayan Orogeny. Adjacent Peninsular tract is 

covered by Quaternary alluvial fill along the foredeep. In the southwestern part, 

Peninsular element is represented by small inliers of gneissic complex and Rajmahal 

Trap. The basement gneissic complex, representing a part of Shillong massif along 

with marine transgressive cover are present in south eastern part. Like other parts of 

Himalayas, this area is the high grade Central Crystallines from comparatively lower 

grade Lesser Himalayan packages which are separated from the Siwalik Belt by 

MBT. At places, particularly towards east, several subsidiary thrust are presented 

between MCT and MBT. Besides these, several approximately N-S trending gravity 

faults are present particularly within northern Tethyan Belt and the southern foot hill 

belt. Within northern Tethyan Belt these N-S faults define some well knows graben 

structures, viz. Pum Qu Graben and Yadong Gulu Graben. In the former, the faults 

affecting the Quaternary glacial deposits are clearly evident. The latter graben is 

considered to be longest one in Tibetan Plateau and is segmented into several N-S 

smaller grabens. The foredeep tract east of Munger – Saharsha Ridge is known as 

Purnia Basin where Gondwana sequence has developed over the rifted basement. The 

structural configuration of this foredeep region is architectured by a set of almost N-S 

trending faults resulting in development of alternate horst and graben structures. The 

westernmost is the Munger – Saharsha Ridge which alternates towards east by Purnia 

Basin. The western and eastern boundaries of Purnia Basin are defined by the Munger 

- Saharsha Ridge Morginal Fault (MSRF) and Malda Kishanganj Fault (MKF). The 

former fault known as Sainthia – Brahmani Fault further south, along which cluster of 

earthquakes have been recorded by the Geological Survey of India, has been found 

seismically active. Further east the prominent tectonic feature is the Rangpur Ridge 

bound by MKF and Jangipur – Goribandha Fault, Teesta Fault and Katihar – 

Nailphamari Fault. Several subsidiary faults, parallel to Teesta Fault forming grabens 

are reported from ridge. Gondwana sequence is found to have developed within these 

grabens. Along with transverse faults, several lineaments cutting across the 

Himalayan belt are also present. These exhibit NE and NW trends. The NE trending 

Azun Lineament considered to be trace of northern extension of East Patna Fault, 

Kanchanjunga Lineament and NW-SE trending Teesta and Purnia lineaments are other 

prominent transverse lineaments. The basement contours corroborate the presence of 

Purnia Saddle and Rangpur Ridge. 

4

Most of the earthquakes in this area are shallow focus (40 km. The 

depth of focus for one event, that of 21.05.1935, has been interpreted to be 140 km. 

As such observed seismic events are mostly concentrated in Main Himalayan Belt. 

Keeping in view the seismotectonic set up and seismicity, the area has been kept in 

Zone – IV as per Map of India Showing Seismic Zones (IS - 1893 (part –I) : 2002). 

GEOTECHNICAL APPRAISAL 

This project envisages the construction of two diversion dams/weirs, one 

across the Teesta river and another on Zemu Chu to augment the discharge for 

optimum utilization for generation of 320 MW of power. The water conductor system 

from Teesta dam / weir to the power house located near the confluence of these two 

rivers near Zema constitutes a 4.25 km long headrace tunnel on the right 

bank of Teesta river and a 3.5km long headrace tunnel on the left bank of Zemu 

Chu. As per the geological map of the area the whole project is located within the high 

grade Central Crystallines which include banded gneisses, migmatite gneisses 

interbanded with calc silicate rocks with bands of quartzites and amphibolite bodies 

belonging to the Chungthang sub group of rocks.The general trend of gneissosity of 

these gneissic rocks is northwestwards with moderate dips towards NE. 

The geological map shows that the project is located in a glacial valley in the higher 

reaches of Sikkim Himalaya with scanty rock outcrops and thick morainic deposits are 

expected both at the diversion site on Teesta river and along the initial reaches of the 

HRT from Teesta to the power house site which might require geophysical surveys for 

delineation of glacial moraine /overburden thickness. However, the diversion site on 

Zemu Chu shows exposures of Crystalline rocks and sound foundation media is 

expected here as compared to the Teesta diversion site. The N-S striking lineaments/ 

mega joints/ fractures/ shear zones likely to be encountered along the HRT alignment 

along Zemu Chu as well as the power house site will have to be carefully delineated , 

classified and proper treatments worked out for such weak zones in the gneisses. 

The sites of the diversion structures expose banded and augen gneisses and 

quartzite – biotite gneisses belonging to CCGC. The rocks are foliated and jointed. It 

is suggested that thickness of overburden in the river bed and on the abutments be 

assessed and availability of bed rock on the abutments be assured before finalizing the 

type of structure and location. The diversion tunnels are expected to encounter the 

gneisses of CCGC and these are expected to provide good tunneling media. The 

proposed HRTs are expected to encounter the high grade gneisses belonging to CCGC 

and interbedded quartzite and garnetiferous quartz biotite schist belonging to 

Chhungthang Group. The rocks belonging to CCGC and Chhunghang Group are 

5

interbanded and are expected to provide good to fair tunneling media in general except 

for reaches where local faults and shears are encountered where poor rock conditions 

can be expected. The preliminary layout of the project indicates that no intermediate 

construction adit has been included along any of these two HRTs. It is suggested that 

tunnels be shifted towards the hills in the middle reaches along the rocks and a kink be 

provided so that at least one construction adit is provided to facilitate construction in 

each HRT. However, adequate lateral and top cover be ensured so that structure is 

safe. The proposed underground powerhouse with installed capacity of 320 MW is 

envisaged at the confluence. The rock conditions are expected to be fair in general. 

The tailrace may also encounter high grade gneisses. The Project is located in zone- 

IV as per Map of India Showing Seismic Zones (BIS : 1893 (Part-I) : 2002). 

Therefore proper seismic coefficient be incorporated in the designs of appurtenant 

structures of the project. This preliminary geotechnical appraisal is based on regional 

geological set up without field visit to the project site. 

REFERENCES 

Lal, Jaya, Mukhopadhyay, G.C. and Ravikant S. (1992-93) Interim report on 

geological mapping of the area between Dikchu and Tong in parts of east and north 

districts, Sikkim (Unpub.Geol. Ind. Rep.for F.S. 1992-93). 

Narula, P.L. Acharayya, S.K., and Banerjee, J., (Eds) (2000). Seismotectonic Atlas of 

India and its Environs, GSI Publication. 

6

1 

Annexure-4.2 

TECHNICAL REPORT ON SEISMIC HISTORY AND SEISMICITY OF THE 

TEESTA BASIN OF SIKXKIM COVERING PROPOSED SITES FOR 

HYDROELECTRIC SCHEMES 

Historical and instrumentally recorded data on earthquakes show that the whole area of 

the proposed sites for hydroelectric schemes at Dikchu, Rongni Storage, Panan, 

Namlum, Zedang, Teesta St-I, Ringpi, Lingza, Rukel and Rangyong in Sikkim lies in a 

region liable to damage due to moderate to great earthquakes. Noteworthy earthquakes 

which affected the region in the past are (i) the Cachar earthquake of 10.01.1869 

(Magnitude= 7.5 on Richter scale), (ii) the Shillong plateau earthquake of 12.06.1897 

(Magnitude= 8.7), (iii) the Dhubri earthquake of 02.07.1930 (Magnitude= 7.1), (iv) the 

Bihar-Nepal Border earthquake of 15.01.1934 (Magnitude= 8.3), (v) the Assam 

earthquake of 15.08.1950 (Magnitude= 8.5) and (vi) the Nepal-India Border earthquake 

of 21.08.1988 (Magnitude= 6.4). The 1897 earthquake had its epicentral tract in and 

around Shillong where there was considerable damage to lives and property, in addition 

to other effects of very strong ground shaking. One of the significant observations made 

on this earthquake was that boulders were thrown out vertically upwards from their 

original places showing that the force of earthquake motion exceeded the force due to 

gravity, at least momentarily. The earthquake was followed by a large number of 

aftershocks. 

In addition to the above significant earthquakes, the region has experienced 

several earthquakes of lesser intensity originating within a radius of 450 km around 

Shillong and neighbouring regions. A list of important earthquakes from I.M.D. 

catalogue occurred in the region bounded by Lat. 25.00 to 30.00°N and Long. 86.00 to 

91.00°E for the period 1505 to 2001 is enclosed. 

The occurrence of earthquakes in Sikkim region is broadly associated with the 

tectonic activity along the well-known faults in the Himalayas such as the Main 

Boundary Thrust (MBT) and the Main Central Thrust (MCT). Besides, earthquakes 

occurring along some other faults namely Malda-Kishanganj Fault, Tista Fault, Purnia- 

Everest Lineament, Katihar-Nailphamani Fault, Dhubri Fault etc. have also affected the 

region. 

In the seismic zoning map of India prepared by a committee of experts under the 

auspices of Bureau of Indian Standards (BIS: 1893: Part I 2002), the entire area of 

Sikkim has been placed in the zone IV. The seismic zone IV is broadly associated with 

a seismic intensity VIII on Modified Mercalli (MM) scale. It may be mentioned that the 

seismic intensity VIII corresponds to a horizontal ground acceleration range of 51- 

350cm/sec 2 or an average acceleration of 172cm/sec 2 in any direction. The ground 

acceleration and hence the intensity of an earthquake at a place depends on magnitude 

of earthquake, distance from the focus, duration of earthquake, type of underlying soil 

and its damping characteristics and liquefaction potential. The damage to the buildings

founded on sandy soil is higher than that in the similar type of buildings having their 

foundation on hard bedrock. Also, the damage will be higher for higher magnitude and 

long duration earthquakes, less epicentral distance soft soil conditions and area with 

high liquefaction potential. 

Presently, there is no scientific technique available anywhere in the world to predict 

occurrence of earthquakes with reasonable degree of accuracy with regard to space, 

time and magnitude. It is, therefore suggested that appropriate steps may be taken to 

ensure that the dwellings and other structures in the region are designed and constructed 

as per guidelines laid down by Bureau of Indian Standards (BIS) to minimize the losses 

caused by earthquakes. Suitable seismic design parameters may be adopted as per 

recommendations of National Committee on Seismic Design Parameters (NCSDP) 

for designing and engineering Hydroelectric Projects. 

EXPLANATION OF COMPUTER OUTPUT (IMD CATALOGUE) 

1. “O” – Time means time of Origin of Earthquake in UTC. 

2. “Depth” means Focal Depth in Kilometers. If depth is reported as 33, it means 

that the earthquake is located in the crust but its focal depth could not be 

determined. 

3. “MAG” means magnitude on Richter scale. 

4. “Zero” under any column means that the parameters have not been determined. 

2

MODIFIED MERCALLI INTENSITY SCALE (ABRIDGED) 

CLASS OF REMARKS 

EARTHQUAKE 

I Not felt except by a very few under specially favourable circumstances. 

II Felt only by a few persons at rest, specially on upper floors of buildings; and 

delicately suspended objects may swing. 

III Felt quite noticeably indoors, specially on upper floors of buildings but many 

people do not recognize it as an earthquake; standing motor cars may rock 

slightly; and vibration may be felt like the passing of a truck. 

IV During the day felt indoors by many, outdoors by a few, at night some 

awakened; dishes, windows, doors disturbed; walls make creaking sound, 

sensation like heavy truck striking the building; and standing motor cars rocked 

noticeably. 

V Felt by nearly everyone; many awakened; some dishes, windows, etc. broken; a 

few instances of cracked plaster; unstable object overturned; disturbance of 

trees; polls and other tall objects notices sometimes; and pendulum clocks may 

stop. 

VI Felt by all, many frightened and run outdoors; some heavy furniture moved; a 

few instances of fallen plaster or damaged chimneys and damaged slight. 

VII Everybody runs outdoors, damage negligible in buildings of good design and 

construction; slight to moderate in well built ordinary structures; considerable 

in poorly built or badly designed structures; and some chimneys broken, noticed 

by person driving motor cars. 

VIII Damage slight in specially design structures; considerable in ordinary but 

substantial buildings with partial collapse; very heavy in poorly build structures; 

panel walls thrown out of framed structured; falling of chimney, factory stacks, 

columns, monuments and walls; heavy furniture overturned, sand and mud 

ejected in small amounts; changes in well water; and disturbs person driving 

motor cars. 

IX Damage considerable in specially designed structures: well designed framed 

structures thrown out of plumb; very heavy in substantial buildings with partial 

collapse; buildings shifted off foundations; ground cracked conspicuously; and 

underground pipes broken. 

3

X Some well built wooden structures destroyed; most masonry and framed 

structures with foundations destroyed; ground badly cracks; rails bent; 

landslides considerable from river banks and steep slopes; shifted sand and mud; 

and water splashed over banks. 

XI Few, if any, masonry structures remain standing; bridges destroyed; broad 

fissures in ground, underground pipelines completely out of services; earth 

slumps and landslips in soft ground; and rails bent greatly. 

XII Total damage; waves seen on ground surfaces; lines of sight and levels distorted; 

and objects thrown upward 

4

LIST OF EARTHQUAKES FROM IMD CATALOGUE OCCURING BETWEEN LAT25 . 00 TO 30 . 00 

DEG. AND LONG 86 . 00 TO 91 . 00DEG. E FOR THE PERIOD 1505 TO 2001 

DATE 

O-TIME LAT LONG DEPTH MAG 

Y M D Hr Mn Sec Deg-N Deg-E Km 

1833 8 26 0 0 . 0 27 . 50 86 . 50 0 . 7 . 5 

1834 7 8 0 0 . 0 25 . 80 89 . 40 0 . 6 . 3 

1834 7 21 0 0 . 0 25 . 80 89 . 40 0 . 6 . 0 

1842 2 5 21 15 . 0 25 . 00 87 . 00 0 . 5 . 5 

1842 11 11 0 0 . 0 25 . 00 90 . 00 0 . 6 . 5 

1843 8 10 0 0 . 0 27 . 00 88 . 30 0 . 5 . 5 

1849 2 27 0 0 . 0 27 . 00 88 . 30 0 . 6 . 0 

1852 5 0 0 0 . 0 27 . 00 88 . 00 0 . 6 . 5 

1897 6 12 11 6 . 0 25 . 90 91 . 00 0 . 8 . 7 

1899 9 25 0 0 . 0 27 . 00 88 . 30 0 . 6 . 0 

1909 2 17 0 0 . 0 27 . 00 87 . 00 0 . 5 . 0 

1918 2 4 17 54 49 . 0 29 . 60 87 . 80 0 . 6 . 0 

1923 4 24 22 3 6 . 0 29 . 60 87 . 80 0 . 5 . 5 

1923 9 9 22 3 42 . 0 25 . 30 91 . 00 0 . 7 . 1 

1926 12 4 11 15 23 . 0 29 . 60 87 . 80 0 . 6 . 0 

1930 7 2 21 3 34 . 0 25 . 80 90 . 20 0 . 7 . 1 

1930 7 3 0 19 5 . 0 25 . 80 90. 20 0 . 5 . 5 

1930 7 4 18 54 44 . 0 25 . 80 90 . 20 0 . 5 . 5 

1930 7 4 21 34 . 0 25 . 80 90. 80 0 . 5 . 5 

1930 7 8 4 32 24 . 0 25 . 80 90 . 80 0 . 5 . 5 

1930 7 8 9 43 . 0 25 . 80 90. 80 0 . 5 . 5 

1930 7 13 14 0 12 . 0 25 . 80 90 . 80 0 . 5 . 5 

1932 3 24 16 8 44 . 0 25 . 80 90 . 20 0 . 5 . 5 

1932 3 25 4 29 32 . 0 30 . 00 89 . 20 0 . 5 . 5 

1933 3 6 13 5 38 . 0 25 . 70 90 . 50 0 . 5 . 8 

1934 1 15 8 43 25 . 0 26 . 60 86. 80 0 . 8 . 3 

1934 1 16 4 59 22 . 0 28 . 00 86 . 00 0 . 5 . 6 

1934 7 21 0 0 . 0 25 . 80 89 . 40 0 . 5 . 5 

1935 5 21 4 22 31 . 0 28 . 80 89 . 30 140 . 6 . 3 

1936 5 30 7 8 38 . 0 25 . 70 90 . 50 0 . 5 . 3 

1936 6 9 0 2 42 . 0 27 . 50 87 . 00 0 . 5 . 5 

1936 6 18 14 56 27 . 0 26 . 60 90 . 30 0 . 5 . 8 

1936 9 7 2 30 49 . 0 27 . 50 87 . 00 0 . 5 . 7 

1937 8 15 11 36 48 . 0 30 . 00 90 . 00 0 . 5 . 8 

1938 1 29 4 13 8 . 0 27 . 50 87 . 00 0 . 5 . 8 

1938 2 26 12 10 43 . 0 28 . 00 90 . 50 0 . 5 . 7 

1938 4 13 1 10 17 . 0 26 . 00 91 . 00 0 . 5 . 2 

1939 6 4 22 36 . 0 28 . 50 86 . 50 0 . 5 . 7 

5

1940 8 2 3 3 59 . 0 28 . 00 90 . 50 0 . 5 . 2 

1945 5 19 5 2 53 . 0 25 . 10 90 . 90 0 . 6 . 1 

1949 12 10 19 37 14 . 0 26 . 00 89 . 00 0 . 6 . 0 

1950 2 26 3 35 48 . 0 28 . 00 90 . 50 0 . 6 . 0 

1951 4 7 20 29 12 . 0 25 . 90 90 . 50 0 . 6 . 8 

1951. 5 28 15 59 19 . 0 29 . 00 87 . 00 0 . 6 . 0 

1952 3 6 9 11 23 . 0 29 . 60 90 . 80 0 . 5 . 5 

1952 11 19 10 23 28 . 0 29 . 80 86 . 60 0 . 6 . 0 

1955 3 27 14 38 43 . 0 29 . 90 90 . 20 0 . 6 . 3 

1958 11 23 20 15 48 . 0 28 . 79 86 . 94 0 . 5 . 5 

1959 6 10 4 25 15 . 0 30 . 00 91 . 00 0 . 5 . 7 

1960 7 29 10 42 44 . 6 26 . 90 90 . 30 11 . 6 . 5 

1960 8 21 3 29 4 . 9 27 . 00 88 . 50 29 . 5 . 5 

1961 9 29 22 36 30 . 0 28 . 00 87 . 00 0 . 5 . 5 

1961 12 25 11 19 10 . 0 27 . 00 90 . 00 0 . 5 . 5 

1963 2 22 1 32 30 . 0 27 . 20 87 . 10 0 . 5 . 2 

1964 2 1 11 28 19 . 2 27 . 30 87 . 78 33 . 4 . 8 

1964 3 27 23 3 41 . 1 27 . 13 89 . 36 29 . 5 . 0 

1964 4 13 3 19 57 . 3 27 . 52 90 . 17 1 . 5 . 2 

1964 8 30 2 35 7 . 3 27 . 36 88 . 21 21 . 5 . 1 

1964 11 9 16 12 51 . 9 29 . 53 86 . 04 33 . 5 . 0 

1965 1 12 13 32 24 . 1 27 . 40 87 . 84 23 . 5 . 8 

1965 1 12 13 55 18 . 1 27 . 31 87 . 68 18 . 5 . 2 

1967 3 2 11 47 13 . 0 28 . 70 86 . 38 20 . 4 . 8 

1968 8 18 14 18 58 . 0 26 . 42 90 . 62 22 . 5 . 1 

1968 10 28 17 48 30 . 1 27 . 57 86 . 03 37 . 4 . 9 

1969 11 5 20 25 13 . 7 27 . 66 90 . 24 13 . 5 . 0 

1970 7 25 1 35 26 . 0 25 . 72 88 . 58 32 . 5 . 1 

1971 10 24 8 59 6 . 3 28 . 30 87 . 19 57 . 4 . 8 

1971 10 31 15 54 48 . 2 26 . 18 90 . 65 33 . 4 . 7 

1971 12 4 8 38 . 2 27 . 92 87 . 95 29 . 5 . 2 

1972 8 21 14 4 34 . 2 27 . 33 88 . 01 33 . 4 . 5 

1972 11 6 10 56 13 . 5 26 . 88 88 . 43 59 . 4 . 4 

1973 3 22 1 6 57 . 4 28 . 12 87 . 15 33 . 5 . 0 

1973 8 1 14 5 15 . 5 29 . 59 89 . 17 63 . 4 . 9 

1974 3 24 14 16 1 . 1 27 . 66 86 . 00 0 . 5 . 4 

1974 3 24 16 17 35 . 3 27 . 63 86 . 01 3 . 4 . 7 

1975 1 23 1 37 42 . 6 27 . 44 88 . 37 33 . 4 . 5 

1975 2 6 6 39 48 . 7 27 . 95 87 . 67 63 . 4 . 7 

1975 4 24 1 35 51 . 2 27 . 44 87 . 04 26 . 4 . 9 

1975 6 24 15 38 28 . 1 27 . 74 87 . 50 33 . 4 . 8 

1975 11 21 13 49 27 . 9 26 . 96 86 . 54 0 . 4 . 9 

1975 11 26 15 2 31 . 1 28 . 15 87 . 80 33 . 5 . 0 

1976 9 14 6 43 51 . 6 29 . 81 89 . 57 75 . 5 . 4 

1977 6 5 19 21 37 . 4 26 . 07 88 . 43 0 . 4 . 7 

1978 10 14 18 48 48 . 9 27 . 66 87 . 33 0 . 4 . 8 

1978 10 23 14 36 50 . 4 28 . 56 86 . 78 33 . 4 . 4 

1979 4 2 1 16 46 . 5 26 . 46 90 . 68 33 . 4 . 4 

1979 4 11 16 8 12 . 6 25 . 98 88 . 84 33 . 4 . 7 

1979 6 19 16 29 8 . 4 26 . 74 87 . 48 1 . 5 . 2 

6

1979 10 17 1 44 22 . 2 27 . 97 87 . 62 33 . 4 . 6 

1979 11 16 19 17 27 . 4 27 . 95 88 . 69 39 . 4 . 6 

1980 6 11 5 25 15 . 4 25 . 79 90 . 31 68 . 4 . 9 

1980 11 19 19 0 44 . 5 27 . 40 88 . 80 1 . 6. 0 

1980 12 22 4 36 8 . 0 26 . 67 89 . 59 33 . 4 . 4 

1980 12 26 5 19 44 . 9 29 . 08 88 . 88 66 . 4 . 5 

1981 2 9 15 49 21 . 6 27 . 20 89 . 76 16 . 4 . 9 

1981 11 21 4 25 5 . 6 29 . 52 89 . 12 50 . 4 . 8 

1982 1 28 7 18 7 . 6 25 . 47 90 . 89 33 . 4 . 4 

1982 2 26 0 5 47 . 5 25 . 79 90 . 62 48 . 4 . 6 

1982 4 5 2 19 41 . 1 27 . 38 88 . 84 9 . 5 . 0 

1982 6 20 15 29 19 . 8 26 . 24 89 . 97 33 . 4 . 5 

1982 7 6 6 13 32 . 0 25 . 88 90 . 31 8 . 5 . 0 

1982 8 18 18 1 7 . 6 27 . 04 89 . 26 51 . 4 . 6 

1983 10 16 22 3 14 . 5 29 . 51 90 . 31 33 . 4 . 5 

1983 12 16 15 15 40 . 1 28 . 37 86 . 65 116 . 4 . 2 

1983 12 23 19 35 44 . 2 25 . 87 87 . 91 33 . 4 . 3 

1984 1 25 23 49 44 . 6 27 . 49 86 . 10 11 . 4 . 6 

1985 5 25 0 28 18 . 7 27 . 60 88 . 48 33 . 4 . 6 

1985 6 7 18 23 59 . 0 26 . 87 90 . 21 33 . 4 . 8 

1985 6 17 21 52 49 . 0 25 . 65 90 . 20 22 . 4 . 6 

1985 10 2 16 33 50 . 3 27 . 19 89 . 73 45 . 4 . 4 

1986 1 7 20 20 . 4 27 . 40 88 . 43 41 . 4 . 7 

1986 1 10 3 46 30 . 9 28 . 65 86 . 56 63 . 5 . 5 

1986 2 2 0 13 50 . 7 27 . 92 86 . 45 33 . 4 . 5 

1986 2 10 12 56 23 . 0 28 . 15 87 . 86 87 . 4 . 7 

1986 4 12 12 44 2 . 2 28 . 63 86 . 57 33 . 4 . 8 

1986 10 25 21 25 30 . 4 26 . 12 88 . 26 33 . . 0 

1986 12 1 19 14 29 . 0 28 . 30 87 . 80 10 . . 0 

1987 4 23 9 5 56 . 8 27 . 93 87 . 01 48 . 4 . 7 

1987 4 25 22 13 47 . 0 25 . 30 88 . 46 10 . . 0 

1987 5 10 5 10 42 . 3 28 . 99 87 . 26 33 . 4 . 5 

1987 6 22 23 6 53 . 5 28 . 40 87 . 17 33 . 4 . 1 

1987 9 25 23 16 29 . 0 29 . 84 90 . 37 19 . 5 . 1 

1987 9 26 1 3 3 . 0 29 . 82 90 . 45 33 . 4 . 4 

1987 9 29 17 30 28 . 3 29 . 91 90 . 41 33 . 4 . 6 

1987 9 29 21 12 30 . 0 29 . 70 90 . 41 46 . 4 . 5 

1987 10 6 22 18 17 . 2 29 . 90 90 . 42 10 . 4 . 7 

1987 10 22 21 23 56 . 0 27 . 07 89 . 06 19 . 4 . 2 

1987 11 25 19 20 40 . 0 27 . 70 86 . 17 33 . 4 . 5 

1987 12 6 23 29 44 . 0 27 . 00 88 . 52 42 . . 0 

1987 12 11 6 39 40 . 0 26 . 04 90 . 92 57 . 4 . 6 

1987 12 12 5 49 . 0 29 . 80 90 . 40 45 . 4 . 8 

1988 1 10 6 18 35 . 0 29 . 75 90 . 29 50 . 4 . 7 

1988 1 10 6 31 42 . 7 29 . 89 90 . 44 10 . 4 . 7 

1988 1 19 11 23 51 . 0 27 . 80 88 . 80 33 . 4 . 3 

1988 3 27 5 56 30 . 0 27 . 10 88 . 42 70 . 4 . 1 

1988 4 9 12 57 55 . 7 29 . 84 86 . 87 33 . 4 . 4 

1988 4 20 6 40 25 . 8 27 . 02 86 . 72 55 . 5 . 4 

1988 4 25 16 4 3 . 7 26 . 90 86 . 54 79 . 4 . 7 

7

1988 5 10 7 16 16 . 1 25 . 32 90 . 88 33 . 4 . 4 

1988 5 26 16 30 5 . 5 27 . 45 88 . 61 42 . 4 . 7 

1988 5 28 23 13 12 . 0 28 . 00 89 . 70 33 . . 0 

1988 8 20 23 9 10 . 1 26 . 72 86 . 63 65 . 6 . 4 

1988 8 20 23 38 56 . 0 26 . 90 86 . 70 38 . . 0 

1988 8 22 11 34 34 . 7 26 . 61 86 . 74 33 . 4 . 3 

1988 8 24 9 55 34 . 3 26 . 77 86 . 44 41 . 4 . 7 

1988 8 29 12 12 17 . 0 26 . 39 87 . 50 33 . 4 . 5 

1988 9 1 22 4 11 . 3 26 . 80 86 . 53 33 . 4 . 5 

1988 9 2 6 35 34 . 3 26 . 56 86 . 48 33 . 4 . 3 

1988 9 27 19 10 10 . 0 27 . 19 88 . 37 28 . 5 . 0 

1988 12 10 15 24 31 . 4 26 . 38 86 . 68 33 . . 0 

1988 12 13 6 29 17 . 3 27 . 14 87 . 97 52 . 4 . 4 

1988 12 24 13 32 22 . 0 26 . 90 88 . 00 41 . 4 . 4 

1988 12 27 2 56 1 . 8 27 . 98 87 . 86 38 . 4 . 6 

1989 2 12 23 44 57 . 0 30 . 00 89 . 86 53 . . 0 

1989 4 9 2 31 36 . 3 29 . 11 90 . 02 10 . 5 . 1 

1989 4 16 0 2 33 . 0 29 . 20 89 . 70 33 . . 0 

1989 5 10 23 20 34 . 0 27 . 70 87 . 20 33 . . 0 

1989 5 22 19 24 31 . 0 27 . 38 87 . 86 4 . 5 .0 

1989 6 11 13 42 45 . 7 26 . 39 90 . 70 50 . 4 . 5 

1989 7 30 21 4 44 . 0 30 . 00 90 . 50 33 . . 0 

1989 10 10 4 10 56 . 0 28 . 36 87 . 49 38 . 4 . 7 

1989 11 19 22 11 34 . 0 29 . 00 89 . 70 33 . 4 . 4 

1990 1 9 2 29 21 . 8 28 . 15 88 . 11 35 . 5 . 7 

1990 1 10 23 1 21 . 7 26 . 52 86 . 67 66 . 4 . 4 

1990 2 18 18 12 48 . 3 29 . 39 89 . 95 10 . 4 . 5 

1990 2 22 13 33 16 . 6 29 . 14 90 . 02 54 . 4 . 9 

1990 2 23 14 25 19 . 3 29 . 38 90 . 02 10 . 4 . 3 

1990 3 1 18 47 28 . 0 28 . 70 88 . 40 33 . 4 . 2 

1990 5 6 10 30 9 . 0 29 . 99 89 . 98 33 . 4 . 2 

1990 5 19 2 18 57 . 0 25 . 40 90 . 93 33 . . 0 

1990 7 13 11 50 11 . 0 28 . 20 86 . 90 33 . 4 . 5 

1990 10 29 12 6 28 . 0 27 . 60 89 . 10 33 . . 0 

1991 1 5 14 50 8 . 0 28 . 90 87 . 92 33 . . 0 

1991 3 4 0 55 38 . 0 28 . 10 89 . 20 33 . . 0 

1991 3 15 4 28 18 . 2 28 . 34 87 . 55 64 . 4 . 7 

1991 6 8 18 59 57 . 8 26 . 30 90 . 37 33 . 4 . 0 

1991 8 7 11 36 29 . 1 25 . 27 88 . 66 10 . 4 . 7 

1991 8 19 22 28 41 . 0 26 . 80 90 . 70 10 . . 0 

1991 9 25 19 26 49 . 3 26 . 70 88 . 40 33 . . 0 

1991 9 27 11 56 40 . 8 29 . 90 90 . 40 33 . . 0 

1991 10 30 13 13 57 . 0 26 . 00 88 . 60 33 . . 0 

1991 12 21 19 52 45 . 1 27 . 79 87 . 96 65 . 4 . 7 

1992 3 7 22 41 50 . 8 29 . 40 89 . 40 113 . 4 . 3 

1992 4 1 13 41 3 . 9 27 . 40 87 . 10 33 . 4 . 3 

1992 4 4 17 43 20 . 7 28 . 10 88 . 00 33 . 4 . 9 

1992 4 20 19 22 59 . 7 25 . 80 90 . 60 55 . 4 . 2 

1992 7 24 6 24 17 . 6 29 . 30 90 . 20 33 . 4 . 8 

1992 7 30 8 24 46 . 6 29 .60 90 . 20 14 . 5 . 9 

8

1992 7 30 9 7 39 . 1 29 . 90 90 . 30 33 . 4 . 2 

1992 7 30 13 36 42 . 0 29 . 80 90 . 30 33 . 4 . 4 

1992 7 30 17 28 53 . 9 30 . 00 90 . 40 33 . 4 . 5 

1992 7 30 19 6 13 . 3 29 . 80 90 . 20 33 . 4 . 3 

1992 8 4 22 50 3 . 0 29 . 90 90 . 40 10 . 4 . 2 

1992 8 8 19 50 42 . 6 29 . 90 90 . 30 33 . 4 . 3 

1992 8 9 22 34 46 . 4 28 . 70 86 . 50 37 . 4 . 3 

1993 2 15 14 29 40 . 8 25 . 90 87 . 50 30 . 5 . 0 

1993 3 3 5 17 31 . 0 25 . 40 90 . 20 33 . 4 . 5 

1993 3 20 14 51 59 . 7 29 . 10 87 . 30 12 . 5 . 8 

1993 3 20 21 26 39 . 4 29 . 00 87 . 40 21 . 5 . 0 

1993 3 31 13 44 10 . 1 29 . 10 87 . 30 20 . 5 . 1 

1993 7 3 2 0 22 . 2 28 . 30 86 . 60 33 . 4 . 7 

1993 7 9 16 23 17 . 3 26 . 80 86 . 00 33 . 4 . 6 

1993 9 5 6 5 54 . 6 27 . 20 87 . 30 33 . 4 . 5 

1993 12 14 2 27 44 . 4 28 . 40 86 . 80 33 . 4 . 8 

1993 12 14 2 27 44 . 4 28 . 40 86 . 80 33 . 4 . 8 

1994 1 16 14 22 38 . 3 26 . 40 89 . 10 33 . 3 . 9 

1994 4 15 14 28 48 . 7 25 . 90 90 . 50 33 . 4 . 2 

1994 5 25 7 38 53 . 7 26 . 60 87 . 80 48 . 4 . 6 

1995 1 1 19 36 13 . 6 27 . 80 87 . 60 33 . 4 . 9 

1995 1 12 23 39 51 . 0 29 . 40 88 . 20 33 . 4 . 9 

1995 8 8 16 52 48 . 8 26 . 40 90 . 40 33 . 4 . 4 

1995 12 6 0 50 33 . 0 25 . 20 91 . 00 33 . 4 . 5 

1995 12 11 9 49 36 . 0 27 . 60 87 . 50 33 . 4 . 0 

1996 1 25 7 15 19 . 3 28 . 00 87 . 00 33 . 5 . 2 

1996 1 25 7 15 13 . 0 28 . 40 86 . 90 33 . 4 . 4 

1996 3 23 16 7 34 . 2 27 . 20 88 . 30 33 . 4 . 0 

1996 4 26 16 31 3 . 0 27 . 80 87 . 60 33 . 5 . 2 

1996 5 10 9 7 1 . 8 30 . 00 88 . 10 0 . 4 . 8 

1996 5 11 3 58 50 . 2 29 . 90 88 . 10 0 . 4 . 8 

1996 5 11 7 27 11 . 2 29 . 90 88 . 10 0 . 4 . 3 

1996 5 14 5 41 8 . 9 29 . 70 87 . 90 0 . 4 . 1 

1996 7 3 7 0 28 . 9 29 . 90 88 . 10 0 . 4 . 1 

1996 7 3 10 10 33 . 8 29 . 90 88 . 20 0 . 5 . 0 

1996 7 3 10 19 42 . 9 30 .00 88 . 20 0 . 4 . 3 

1996 7 3 10 49 50 . 5 29 . 90 87 . 80 0 . 4 . 1 

1996 7 4 18 11 4 . 6 30 . 00 88 . 10 0 . 4 . 9 

1996 7 6 8 12 39 . 4 29 . 90 87 . 90 0 . 3 . 8 

1996 7 13 8 29 4 . 0 29 . 90 88 . 10 0 . 4 . 3 

1996 7 22 15 54 7 . 0 30 . 00 88 . 00 0 . 4 . 5 

1996 8 3 7 12 6 . 0 30 . 00 88 . 20 0 . 4 . 1 

1996 8 18 2 48 . 0 25 . 80 90 . 10 0 . 4 . 4 

1996 9 13 3 41 8 . 6 27 . 00 88 . 20 33 . 4 . 5 

1996 9 25 17 41 17 . 2 27 . 40 88 . 50 33 . 5 . 0 

1996 10 3 1 29 3 . 1 28 . 20 87 . 50 33 . 4 . 5 

1996 10 14 14 49 12 . 7 29 . 90 88 . 20 33 . 4 . 4 

1996 12 30 11 8 18 . 9 27 . 43 86 . 63 37 . 5 . 0 

1996 12 30 15 16 29 . 5 27 . 23 86 . 50 33 . 3 . 6 

1997 1 22 11 12 4 . 4 25 . 60 90 . 30 33 . . 0 

9

1997 1 25 20 8 28 . 7 30 . 00 88 . 00 33 . 4 . 4 

1997 3 3 9 29 40 . 0 27 . 24 86 . 00 45 . 4 . 7 

1997 3 22 21 16 4 . 8 29 . 89 88 . 15 33 . 4 . 4 

1997 4 4 10 8 41 . 0 25 . 50 90 . 80 33 . 3 . 8 

1997 4 7 13 0 42 . 0 27 . 40 86 . 50 33 . 4 . 4 

1997 5 26 0 45 32 . 1 27 . 70 86 . 90 33 . . 0 

1997 7 5 6 22 53 . 5 28 . 80 86 . 86 33 . 4 . 8 

1997 7 8 21 16 49 . 8 29 . 83 88 . 31 33 . 3 . 7 

1997 7 9 7 18 52 . 9 29 . 90 88 . 40 33 . 4 . 1 

1997 7 12 23 41 9 . 7 29 . 90 88 . 40 33 . . 0 

1997 8 10 11 53 17 . 2 29 . 16 89 . 49 33 . 3 . 4 

1997 8 17 20 3 32 . 8 28 . 13 87 . 56 33 . . 0 

1997 9 18 7 37 10 . 0 28 . 87 86 . 15 33 . 4 . 6 

1997 10 11 10 11 10 . 3 27 . 70 86 . 40 33 . 4 . 3 

1997 10 12 19 45 25 . 8 30 . 00 88 . 00 33 . . 0 

1997 10 30 2 2 52 . 0 29 . 50 89 . 70 33 . 5 . 3 

1997 10 30 20 3 . 0 29 . 20 89 . 40 0. 4 . 9 

1997 11 14 12 30 23 . 9 25 . 30 87 . 70 33 . . 0 

1997 11 27 16 11 57 . 0 27 . 60 87 . 34 33 . 5 . 1 

1997 11 27 16 55 52 . 1 27 . 70 87 . 76 33 . 4 . 2 

1997 12 8 2 3 55 . 8 27 . 48 87 . 17 33 . 5 . 0 

1997 12 8 6 37 57 . 8 27 . 48 87 . 16 33 . . 0 

1998 1 16 18 6 42 . 5 30 . 00 86 . 00 33 . 4 . 0 

1998 2 1 17 32 48 . 2 28 . 10 87 . 10 33 . 4 . 5 

1998 2 12 2 40 29 . 1 26 . 50 88 . 10 33 . 4 . 6 

1998 2 28 4 59 30 . 7 27 . 00 87 . 50 33 . 4 . 4 

1998 3 15 20 35 29 . 3 28 . 55 86 . 88 33 . 4 . 4 

1998 3 16 10 35 2 . 0 26 . 90 89 . 68 33 . 3 . 8 

1998 3 18 18 12 18 . 9 27 . 36 88 . 33 33 . 4 . 0 

1998 5 13 1 24 55 . 6 28 . 18 89 . 80 10 . 4 . 9 

1998 7 31 17 50 18 . 3 28 . 01 87 . 73 33 . 4 . 1 

1998 8 18 4 10 20 . 6 27 . 55 90 . 98 22 . 5 . 2 

1998 8 24 7 32 21 . 5 30 . 00 87 . 92 33 . . 0 

1998 8 25 9 43 6 . 0 29 . 99 88 . 09 33 . 4 . 1 

1998 8 25 9 56 44 . 0 29 . 83 87 . 91 33 . 4 . 4 

1998 8 25 10 25 6 . 0 29 . 98 88 . 10 33 . 4 . 4 

1998 8 25 12 43 4 . 3 29 . 96 88 . 09 33 . 4 . 4 

1998 8 25 13 39 49 . 5 29 . 92 88 . 12 33 . 3 . 8 

1998 8 25 15 16 2 . 7 29 . 97 88 . 10 33 . 4 . 4 

1998 8 30 3 49 48 . 1 29 . 90 87 . 98 33 . 4 . 0 

1998 9 3 18 15 56 . 5 27 . 85 86 . 94 33 . 5 . 6 

1998 9 3 18 22 19 . 2 27 . 97 87 . 04 33 . . 0 

1998 9 3 18 51 38 . 6 27 . 65 86 . 80 33 . 4 . 4 

1998 9 3 21 0 53 . 5 27 . 72 86 . 88 33 . 4 . 1 

1998 9 3 23 2 28 . 3 27 . 60 86 . 73 33 . 4 . 6 

1998 9 4 0 36 17 . 9 27 . 45 86 . 46 33 . 4 . 1 

1998 9 4 1 10 18 . 4 27 . 77 86 . 79 33 . 4 . 2 

1998 9 4 21 16 13 . 7 27 . 65 86 . 72 33 . . 0 

1998 9 6 21 35 49 . 4 27 . 86 86 . 89 33 . 4 . 6 

1998 9 10 22 57 16 . 9 27 . 20 88 . 34 33 . 4 . 7 

10

1998 9 12 5 8 52 . 1 27 . 85 86 . 90 33 . 4 . 2 

1998 9 21 23 24 40 . 6 29 . 94 88 . 00 33 . 4 . 1 

1998 9 26 20 48 44 . 1 27 . 52 86 . 13 33 . 3 . 9 

1998 9 30 2 29 55 . 1 29 . 94 88 . 11 33 . 5 . 1 

1998 10 11 22 0 49 . 9 26 . 35 86 . 40 90 . 4 . 4 

1998 10 13 14 47 51 . 9 29 . 74 87 . 88 33 . . 0 

1998 10 16 14 17 16 . 7 30 . 00 88 . 19 33 . . 0 

1998 11 26 10 14 27 . 6 27 . 75 87 . 89 73 . 5 . 1 

1998 12 1 5 35 9 . 2 27 . 93 87 . 64 33 . 4 . 8 

1999 1 28 16 10 33 . 9 28 . 22 87 . 31 41 . 4 . 0 

1999 3 25 5 4 54 . 3 28 . 51 88 . 28 33 . 3 . 8 

1999 3 25 20 47 57 . 4 28 . 50 87 . 63 13 . 4 . 2 

1999 3 31 22 32 57 . 8 28 . 57 86 . 81 21 . . 0 

1999 4 10 20 42 39 . 7 28 . 04 87 . 85 33 . 4 . 2 

1999 5 7 17 53 52 . 3 27 . 22 90 . 64 33 . . 0 

1999 5 9 8 8 57 . 7 27 . 40 89 . 45 15 . . 0 

1999 6 13 7 38 6 . 4 28 . 14 86 . 64 33 . 4 . 4 

1999 7 4 6 5 15 . 2 25 . 42 90 . 28 33 . 3 . 8 

1999 8 1 8 24 51 . 2 28 . 37 86 . 79 40 . 5. 0 

1999 9 5 2 28 22 . 8 28 . 07 87 . 53 33 . 4 . 5 

1999 9 8 18 8 27 . 9 27 . 90 87 . 91 19 . 3 . 7 

1999 9 16 12 20 9 . 8 27 . 55 87 . 71 33 . . 0 

1999 9 20 7 28 5 . 6 27 . 24 87 . 98 23 . 4 . 1 

1999 9 21 13 54 39 . 8 25 . 16 88 . 86 2 . 3 . 9 

1999 10 15 7 33 1 . 0 29 . 61 90 . 06 33 . 4 . 4 

1999 10 18 16 12 55 . 7 26 . 68 87 . 22 33 . . 0 

1999 11 5 15 57 21 . 4 28 . 59 87 . 08 23 . 3 . 7 

1999 11 17 5 27 14 . 0 28 . 09 89 . 18 33 . 3 . 6 

1999 1 28 16 10 33 . 9 28 . 22 87 . 31 41 . 4 . 0 

1999 3 25 5 4 54 . 3 28 . 51 88 . 28 33 . 3 . 8 

1999 3 25 20 47 57 . 4 28 . 50 87 . 63 12 . 4 . 2 

1999 4 10 20 42 39 . 7 28 . 04 87 . 85 33 . 4 . 2 

1999 6 13 7 38 6 . 4 28 . 14 86 . 64 33 . 4 . 4 

1999 7 4 6 5 15 . 2 25 . 42 90 . 28 33 . 3 . 8 

1999 8 1 8 24 51 . 2 28 . 37 86 . 79 40 . 5 . 0 

1999 9 5 2 28 22 . 8 28 . 07 87 . 53 33 . 4 . 5 

1999 9 8 18 8 27 . 9 27 . 90 87 . 91 19 . 3 . 7 

1999 9 20 7 28 5 . 6 27 . 24 87 . 98 22 . 4 . 2 

1999 9 21 13 54 39 . 8 25 . 16 88 . 86 2 . 3 . 9 

1999 10 15 7 33 1 . 0 29 . 61 90 . 06 33 . 4 . 4 

1999 11 5 15 57 21 . 4 28 . 59 87 . 08 23 . 3 . 7 

1999 11 7 5 11 57 . 6 27 . 10 89 . 13 14 . 3 . 8 

1999 11 17 5 27 13 . 8 28 . 04 89 . 22 33 . 3 . 3 

2000 1 20 12 54 27 . 5 27 . 78 86 . 02 33 . 5 . 0 

2000 1 25 12 7 33 . 3 29 . 94 89 . 72 0 . 5 . 0 

2000 2 21 18 21 43 . 2 28 . 36 86 . 56 33 . 4 . 7 

2000 3 13 20 44 38 . 3 27 . 43 87 . 85 108 . 4 . 1 

2000 4 18 7 53 45 . 2 26 . 55 90 . 26 33 . 3 . 3 

2000 6 20 7 16 43 . 8 26 . 04 90 . 31 33 . 4 . 3 

2000 9 6 7 19 8 . 9 28 . 52 86 . 86 33 . 4 . 2 

11

2000 10 3 17 8 22 . 4 26 . 88 89 . 8 33 . 2 . 8 

2001 1 16 8 6 57 . 4 26 . 42 90 . 24 33 . . 0 

2001 2 9 10 20 55 . 7 27 . 24 89 . 67 13 . 3 . 9 

2001 2 27 1 46 7 . 0 26 . 48 90 . 55 20 . 4 . 7 

2001 2 27 16 21 25 . 6 28 . 38 86 . 97 33 . 4 . 9 

2001 4 3 23 8 38 . 0 27 . 74 86 . 13 33 . 4 . 6 

2001 4 3 23 26 4 . 4 27 . 82 86 . 18 18 . 3 . 5 

2001 4 8 18 35 49 . 3 28 . 16 88 . 57 20 . 3 . 9 

2001 4 20 18 35 2 . 7 26 . 13 90 . 67 33 . 4 . 6 

2001 4 28 10 37 59 . 1 28 . 55 87 . 14 33 . 5 . 0 

2001 4 29 10 39 9 . 1 28 . 70 87 . 14 33 . 4 . 5 

2001 5 3 16 2 59 . 6 27 . 63 90 . 47 33 . 3 . 8 

2001 5 21 21 55 7 . 8 28 . 54 86 . 72 33 . 3 . 8 

2001 6 12 10 47 46 . 6 28 . 46 86 . 57 20 . 3 . 9 

2001 7 3 19 16 18 . 4 26 . 15 89 . 20 6 . 3 . 6 

2001 7 6 23 4 3 . 4 27 . 65 88 . 64 10 . 2 . 7 

2001 8 6 6 23 32 . 7 27 . 47 87 . 47 9 . 4 . 3 

2001 9 4 22 8 3 . 7 25 . 37 90 . 96 15 . 3 . 7 

2001 9 27 22 40 11 . 1 26 . 99 87 . 76 2 . 4 . 1 

2001 12 2 22 41 14 . 8 27 . 18 88 . 33 15 . 4 . 8 

NO. OF EARTHQUAKES = 358 

12

TITLE 

ANNEXURES 6.1 

Reply of General Comments & on power 

potential studies by CEA (HP& I) 

Reply of Comments of SP&PA Division , CEA 

(HP& I) 



No. 

1-2 

3-5 

Reply of comments of CMDD(E&NE), CWC 6-7 

Reply of comments of HCD(E&NE),CWC 8 

Reply of CWC’s Comments on Hydrology 9-12

REPLY OF COMMENTS OF CEA (HP & I ) ON DRAFT PFR OF 

TEESTA (I) H E PROJECT. 

(CEA Letter No.7/9/(NHPC)//HP&I/2004/536 dated 07.03.2004 ) 

Sr.No. Comments Reply 

1 

General Comments 

It may be ensured that the Initial This has been considered. 

Environmental studies 

incorporated in the PFR are as per 

scope of work for PFR. 

2 It may be ensured that the 

Financial Parameters are taken as 

per guidelines sent vide our Lr. 

No. 7/9/HPI-2003/1118-1123, 

dated 21 st October, 2003. 

3 It may be ensured that the Cost 

Estimates prepared are as per the 

Guidelines sent vide our Letter 

No.7/9/HP&I/2003/1163-1172, 

dated 24.10.2003. 

4 NHPC may indicate 

recommendations for further 

studies required wherever 

necessary in the relevant chapters 

of PFRs for consideration during 

FR/DPR stage. 


Installed Capacities & assessment 

of power benefits takes into 

account various comments and 

advise given in this regard. 


hydrology adopted is approved by 

CWC. 

. 

1 

Annexure 6.1 

The Financial Parameters has 

been taken as per guidelines of 

CEA. 

Cost estimate is as per CEA 

guidelines and in line with 

discussions with CEA and 

subsequent comments thereupon. 

Recommendation for further 

studies required for preparation 

of FR/DPR has been indicated 

wherever necessary. 

The installed capacities and 

assessment of power benefits 

require no change. 

Hydrology adopted is as per 

decisions taken in the progress 

review meeting held with CEA.

7 The layout planning of project 

components may take into 

account the view and advise of 

CWC. 

8 The power evacuation 

arrangements considered in the 

PFR should take into account 

views and suggestions of 

SP&PA Division of CEA. 

9 An Executive Summary may be 

prepared as per general guidance 

sent vide our Lr. No. 7/9/hpi- 

2003/1412-1419 dated 2 nd 

December, 2003. 

10 GSI report may be obtained and 

included in the PFR. 

Power Potential Studies: 

1 A table giving the summary of 

studies indicating yearly inflows, 

annual energy generation, load 

factor of operation during 

monsoon and lean flow period 

may be presented in studies. 

2 It is presumed that the selection 

of unit size takes into account 

transport limitations etc. 

3 NHPC may indicate 

recommendations for further 

studies required for preparation 

of FR/DPR. 

2 

This has been considered. 

The chapter on power evacuation 

arrangements is based upon the 

finalized scheme of Power 

evacuation as communicated by 

CEA. 

This has been incorporated in the 

PFR. 

GSI report has been obtained and 

attached as annexure 4.1. 

Table 7.4(C) of the PFR chapters 

already gives the summary of studies 

indicating yearly inflows, annual 

energy generation, load factor of 

operation during monsoon and lean 

flow period. 

The transport limitations as informed 

by the site have been taken into 

consideration. 

Recommendation for further studies 

required for preparation of FR/DPR 

has been indicated wherever 

necessary.

REPLY ON COMMENTS OF SP&PA DIVISION ON DRAFT PFR OF 

TEESTA (I) HE PROJECT 

(CEA Letter No.7/9/(NHPC)/ 2003/HP&I/541 dated 18.03.2004 & 

letter no.67/23/2003-HP&PI/334dt. 12.04.04 ) 

Comments Reply 

General 

Teesta HEP is located in North 

Sikkim district of Sikkim envisages 

utilization of the water of the river 

Teesta and Zemu Chu for power 

generation on a run of river type 

development, having 4 units of 80MW 

each with underground power house. 

Construction Power 

The necessary construction power shall 

be available for the execution of 

Teesta(I) HEP from 66/11KV 

Chungthang substation. 

Switchyard 

A switchyard of 250mx170m size 

shall be formed near the underground 

power house having 7Nos. of 400kV 

bays. 

Generator bays – 4Nos. 

220 kV line - 2 Nos. 

Station Transformer bay – 1No. 

Bus Coupler bay – 1No. 

Which is in order but diagram of 

switchyard is not furnished. 

Power Evacuation: 

NHPC has proposed that power will 

be generated at 11KV and stepped up 

to 400kV through 13Nos. 33MVA (1- 

O)11/400 kV unit transformers. Power 

generated at Teesta(I) HEP can be 

evacuated through one no. 400kV D/C 

line to be connected at the pooling 

point which is proposed to be 2km 

away downstream from Teesta(I) HEP 

which is in order. 

3 

It is general description of the 

project and no reply is required. 

This has been considered in PFR. 

The Single line diagram of 

switchyard is placed as plate 8.1 in 

the Final PFR. 

It is general description and no reply 

is required

Cost: 

1. Cost of switchyard (400 kV) with 7 

bays has been estimated at Rs. 

250 Lakhs/bay. XLPE Cables 400 

kV with termination kit @ LS $ 

700/m for 6500 meters has been 

considered. For XLPE cables 

Custom duty@ 22% has been 

considered. 

In addition to above ED @ 16% 

(for indigenous equipment), 

spares@ 3 %, marine freight and 

insurance @ 6% for XLPE cable 

and inland freight and insurance 

@ 6 %, erection and 

commissioning @8%, 

establishment and contingency, 

other charges @ 11 % has been 

considered. In this connection it is 

to be intimated that consideration 

of marine freight and inland 

freight @6% each is not correct, 

instead for XLPE cable 

transportation and insurance 

should not be more than 3%. 

Similarly establishment and 

contingencies and other charges 

should be considered @8% - 2% 

handling charges on custom duty 

for the imported equipment may 

be considered. 

Estimates of switchyard except 

for the comments mentioned 

above is generally in order. 

2. 1 No. 400kV D/C transmission line 

@ 65 lakhs/km. has been 

considered. 

In addition ED@ 16%, spares @ 

3%, CST @ 4%, transportation 

and insurance @ 6%, erection and 

commissioning @ 8%, 

establishment, contingency and 

other charges @ 11% has been 

considered. 

This cost in hilly terrain of 

4 

The composition of Tax and duties 

is in line with the CEA guidelines 

and submitted PFRs. The 

transportation and insurance cost has 

been taken as 6% in line with the 

other project components ( viz. 

Generating units, transformers etc.). 

For XLPE cables, the Marine 

insurance and Marine transportation 

has been taken as equal to inland 

transportation and insurance. 

The cost of transmission line has 

been revised and incorporated in the 

cost estimate of final PFR.

Sikkim is on the higher side as 

the overall cost should not go 

beyond 70 lakh/km. However, at 

the time of submission of FR the 

detailed break up of the 

components of cost will be 

required to be furnished. 

5

REPLY ON COMMENTS OF CMDD DIRECTORATE, CWC ON 

PFR OF TEESTA (I) HE PROJECT 

(Letter No C.W.C. P.U. No. 20/2/03-CMDD(E&NE)/223 dated 7.4.2004) 

Comments of CEA/CWC Replies of Design Division 

1. The difference in elevation 

between MWL of Dam-II of Teesta-I 

project and TRT outlet of Talam H.E. 

Project may be reviewed. 

2. The report should indicate the 

alternative layouts and alternative 

locations of project components 

examined during the preparation of 

PFR to bring out their merits and 

demerits of each including the finally 

adopted in PFR. The reasons for 

rejecting the particular alternative 

should be elucidated justifying the 

rejection. 

3. As per clause no. 5.2 of IS: 12966 

(Part-I)-1992 inspection galleries at 

higher levels above the foundation 

gallery may be provided. Also 

instrumentation gallery may be 

incorporated in the drawings. 

4. From Drg. No. F/DCE/730/01/02 it 

is seen that the upstream face is 

curvaceous, however it is felt that it is; 

due to projection of heel of the NOF 

blocks. This may be clarified. 

However a blowup plan may be 

provided in PFR. 

5. The reasons for giving skew axis of 

d/s cofferdam may be elucidated. 

6. It should be mentioned in the report 

that the PMF value has been vetted by 

hydrology (NE) Dte. CWC. 

7. Choice of a diversion flood to a 

tune of 400 cumecs (for both the 

dams) is daring and does not have a 

bearing on experience & construction 

6 

FRL, MDDL and Tail water level 

of both the project have been 

vetted by CEA. 

The study on alternative layouts 

and alternative locations has been 

included in further studies to be 

taken up during FR/DPR stage. 

Details of inspection & 

instrumentation galleries are 

normally shown in the FR/DPR 

drawings when exact rock profile 

& more information on 

topography & geology etc. is 

available. 

In a valley foundation level of dam 

continuously goes up and base 

width keeps on reducing from 

center of river towards both 

abutment as we go up. 

Therefore upstream face appears 

curvaceous even though the axis is 

straight. However blowup plan of 

dam area has already been 

provided. 

The d/s cofferdam axis is 

perpendicular to the direction of 

flow. 

This point pertains to hydrology 

wing. 

Reasons have been detailed in 

revised chapter-VI (conceptual 

layout and planning of PFR).

of the project on the fast track basis. 

This should have purely a technical 

formulation considering the type of 

dam as well as the return period/lean 

period discharges etc. Moreover this 

aspect needs to be vetted by hydrology 

Directorate (NE) of CWC. 

Accordingly this paragraph may be 

reconstructed. 

8. An elaborate chapter regarding the 

quality and quantity of construction 

material may be incorporated. 

9. Profile of crest of the d/s glacis of 

overflow section may be incorporated. 

10. In the u/s elevation, it is seen that 

provision of sump well, air vent pipe 

& lift well have not been indicated. A 

fresh drawing incorporating all these 

may be provided. 

7 

Availability of Construction 

material has been addressed in 

revised Chapter–IV (Topographical 

& Geo-technical aspect 

of PFR). The construction material 

testing has to be done during 

FR/DPR stage for ensuring quality 

of construction material. 

D/S glacis profile of the spillway 

crest has to be studied in detail and 

designed during FR/DPR stage 

and hydraulic model studies have 

to be taken up. 

Air vent pipe has been shown in 

overflow section of dam. Such 

details are in the scope of 

FR/DPR.when more specific data 

of rock profile, topography & 

geology etc. will be available.

REPLY ON COMMENTS OF HCD(E&NE) DIRECTORATE, CWC ON 

PFR OF TEESTA (I) HE PROJECT 

(Letter No CWC U.O. No. 3/5/2000-HCD(E&NE)/871dated 8.4.2004) 

1. Specific comments cannot be made 

on general layout of the scheme due to 

non-availability of the contours 

upstream of the intake and further d/s 

of the tailrace. 

2. Provision/design of desilting 

chamber needs to be reviewed with 

the more observed data. 

3. Sizing, shape, type & location of 

surge shaft needs to be reviewed with 

detailed transient studies. 

4. Efficacy of silt flushing through low 

level spillway on the live storage and 

also at the power intake vicinity needs 

to be examined. 

5. Provision of a vertical drop instead 

of inclined one, in the pressure shaft 

needs to be evaluated. 

8 

The contours and other features 

have been traced from S.O.I. of 

India topo-sheet no. 78A/10 (Scale 

1:50000). 

It has been included in further 

studies to be taken up during 

FR/DPR stage. 

Transient studies of the surge shaft 

have been included in further 


FR/DPR stage. 

Efficacy of silt flushing shall be 

seen through model studies, which 

has been included in further 


FR/DPR stage. 

Detailed design studies of the 

pressure shaft shall be taken up 

during FR/DPR stage.

Consistency of 

data 

Water 

availability 

studies 

REPLY OF CWC’s COMMENTS ON HYDROLOGY CHAPTER OF 

TEESTA (I) HE PROJECT 

(CWC Letter NO. 4/330/2003(V)/Hyd(NE)/128 dt 31/3/2004) 

CWC Comments NHPC Replies 

The approved series of Lachen 

G&D data used for converting to 

the present project may be 

furnished for vetting of the 

present series. 

i) As per the available records 

in this Directorate the total 

catchment area upto Lachen 

G&D site is 1717 sq.km., out 

of which 207 sq.km. is rain 

fed. The total catchment area 

upto Teesta Stage III is 2787 

sq.km., out of which 1189 

sq.km. is rainfed. The 

figures given in the report are 

not consistent with these 

figures. The same may be 

clarified/reconciled. 

ii) The project authorities have 

not mentioned about the 

source, methodology of 

observation, consistency 

checks performed on the 

discharge data. The same 

may be clarified/reconciled. 

iii) The period of the availability 

of the data at Lachen G&D 

site is mentioned as from 

1976 to 1997. However, as 

per the available information 

in this Directorate the data at 

Lachen G&D site is available 

only from 1989 onwards. 

This may be confirmed. 

iv) In the absence of site specific 

observed data the project 

authorities are advised to use 

the Lachen dam site series 

issued by CWC for DPR of 

Teesta Stage II. However, at 

9 

The available average 10-daily 

series at Lachen is enclosed as 

Appendix (A). 

(i) The catchment area given in the 

report are in consistent with that 

mentioned in DPR – Dec 1997 of 

Teesta-V and Addendum to 

DPR-May 1990 of Teesta-III. 

(ii) The data has been collected by 

CWC, by float method of 

velocity measurement. 

(iii) The data base at Lachen G&D 

site given in the report is 

consistent with that mentioned in 

DPR – Dec 1997 of Teesta-V and 

taken from data volume prepared 

by CWC along with Teesta-VI 

report. 

(iv) For the present the average 10daily 

series obtained on the basis 

of data observed at Lachen G&D 

site may be taken. The series 

need be improved in DPR stage 

as per CWC suggestion.

the DPR stage, only the site 

specific scientifically 

observed discharge data is to 

be used. 

Design flood i) The design flood studies 

done by NHPC are too 

empirical to be relied upon. 

ii) In the absence of short 

interval concurrent rainfallrunoff 

data the design flood 

may be calculated using 

relevant sub-zonal report of 

CWC superimposing PMP 

values from IMD. 

The value so computed may be 

incorporated in the comparative 

study and adopt a realistic figure 

of design flood. 

Sedimentation Though the project is a run-offthe-river 

scheme approximate 

sedimentation studies may be 

carried out to decide the sill level 

of permanent outlet and live 

storage available for peaking 

purpose. 

General 

comments 

The hydrological studies for PFR 

may be revised incorporating the 

above observations. 

The agency taking up the detail 

investigations/DPR must review 

the hydrological and hydro 

meteorological networks and the 

other recommendations given in 

the report in consultation with 

HSO, CWC. 

10 

It is worth mentioning here that 

although deterministic approach of 

design flood computation has not 

been used directly in the present 

study for Teesta-I sub basin, 

however, this approach has been 

used indirectly along with Emperical 

method, as the design flood Teesta- 

V dam site had been computed by 

deterministic approach only. 

We are aware of the findings of 

CWC studies published in the 

Compendium on silting of reservoirs 

in India. As per that report, the 

sediment rate varies from 0.05658 to 

0.2785 Ham/Sq.km /year for Indus, 

Ganga and Brahmaputra basin. But 

the silt rate adopted for this 

particular project has been adopted 

on the basis of observed data at 

Dikchu in Teesta basin and is more 

region specific than that given in 

“Compendium on silting of 

reservoirs in India”. 

Agreed, the observation network and 

analysis needs to be done at the time 

of DPR

YEAR/ 

MONTH 

I 

1976 II 

III 

I 

1977 II 

III 

I 

1978 II 

III 

I 

1979 II 

III 

I 

1980 II 

III 

I 

1981 II 

III 

I 

1982 II 

III 

I 

1983 II 

III 

I 

1984 II 

III 

I 

1985 II 

III 

I 

1989 II 

III 

I 

1990 II 

III 

I 

1991 II 

III 

I 

1992 II 

III 

I 

1993 II 

III 

TEESTA BASIN PFR PROJECTS 

AVERAGE 10-DAILY DISCHARGE AT LACHEN 

11 

Appendix (A) 

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC AVG 

22.46 20.85 24.40 33.11 39.17 62.22 112.64 95.24 101.11 36.07 28.60 17.21 

21.50 20.48 26.15 36.24 31.02 121.43 107.34 103.82 58.31 28.49 23.68 14.72 

20.45 21.36 28.36 42.37 43.49 88.11 81.70 110.99 42.57 28.76 21.17 13.60 

12.13 20.33 11.23 21.58 23.53 66.92 98.67 113.54 77.91 64.83 33.86 21.08 

11.53 19.81 16.03 20.25 29.06 118.72 116.09 95.54 63.71 40.88 30.89 22.28 

11.04 11.87 14.88 21.52 41.41 86.33 139.04 111.56 53.12 32.65 23.32 25.20 

17.33 16.05 14.62 20.83 36.00 98.85 115.14 140.98 74.19 69.85 37.20 26.33 

15.53 15.71 15.63 26.67 73.80 103.72 123.42 119.13 96.61 54.47 27.74 22.31 

15.86 14.44 17.33 31.60 86.17 131.14 119.11 89.44 72.62 46.43 27.31 20.04 

18.49 15.27 17.01 32.37 60.61 70.42 125.47 124.25 102.34 109.17 55.70 40.67 

17.06 15.24 17.82 32.19 77.26 84.27 120.02 98.10 89.31 74.50 45.36 33.50 

16.77 16.57 21.92 40.39 59.10 120.82 134.45 104.05 65.51 55.88 42.70 32.25 

30.39 27.84 31.99 49.75 69.33 96.94 152.79 165.59 144.69 71.81 48.57 37.82 

29.26 29.17 32.80 63.81 59.30 129.01 156.42 181.85 113.42 61.71 44.22 34.37 

29.00 31.10 44.29 72.70 63.21 144.38 163.88 151.45 91.80 57.49 40.71 31.22 

30.08 25.88 31.83 39.85 73.01 84.19 174.62 137.34 134.86 84.46 58.23 35.32 

28.19 26.62 33.71 50.46 78.85 100.69 149.74 144.93 115.58 78.17 46.46 31.77 

27.83 32.19 39.80 59.45 76.47 136.69 140.84 140.89 92.12 68.33 38.48 24.90 

22.87 24.89 26.18 43.87 60.90 117.32 125.42 111.37 95.18 63.94 40.50 30.23 

25.46 25.85 29.31 43.80 68.40 129.21 140.50 105.43 137.65 53.70 35.33 27.87 

25.10 25.13 34.91 48.58 66.45 142.83 165.74 123.73 90.32 51.71 34.21 26.38 

26.16 14.86 22.08 37.56 61.85 124.01 192.35 132.89 132.32 120.66 66.29 41.85 

23.30 14.76 28.30 30.70 74.12 120.35 163.64 140.91 148.77 118.95 60.90 39.23 

16.33 20.54 25.52 38.44 98.63 167.96 162.35 164.62 171.61 81.08 50.16 35.16 

31.38 26.48 58.32 67.31 81.46 175.75 218.45 208.95 225.90 144.04 104.90 51.65 

30.88 27.50 65.17 71.76 119.05 211.34 219.17 209.51 215.58 182.71 90.65 50.82 

27.48 26.41 64.04 71.78 169.13 189.80 231.70 219.33 171.01 140.76 80.57 51.02 

51.46 46.24 65.00 78.91 80.93 83.95 234.12 207.60 109.35 75.24 44.10 28.93 

48.88 42.27 70.40 95.23 93.93 104.79 305.52 218.98 104.45 65.94 38.33 26.16 

42.32 51.17 65.56 112.46 130.82 296.94 256.89 268.10 87.53 54.34 33.96 24.06 

12.82 13.75 15.20 16.56 41.76 93.31 166.45 132.25 98.67 70.13 30.20 19.44 

12.48 12.56 15.50 19.83 43.13 154.58 163.73 103.76 89.37 59.69 24.51 16.86 

12.36 13.38 15.93 23.78 105.09 163.48 152.41 101.80 88.79 48.55 22.29 14.77 

13.46 11.12 9.21 7.92 23.89 102.27 128.77 119.66 103.53 57.85 29.68 16.96 

12.48 10.44 7.52 13.07 42.10 99.91 164.15 121.56 99.14 58.93 22.18 13.99 

11.30 10.09 7.66 16.19 48.43 116.83 140.49 107.88 69.04 48.48 18.52 12.06 

12.22 11.49 11.77 37.16 37.64 54.30 90.04 109.65 105.15 68.70 37.06 21.01 

11.99 10.92 13.43 21.18 45.85 85.73 87.73 126.32 111.09 54.47 32.76 16.11 

11.86 11.04 14.16 22.42 50.73 78.84 95.62 104.38 86.05 44.71 24.99 14.18 

12.90 11.56 11.45 14.00 17.63 22.79 54.10 68.06 65.16 40.09 18.07 14.47 

10.71 11.15 11.53 19.67 20.53 32.49 54.73 68.33 64.13 28.76 16.06 12.53 

10.93 10.69 11.85 17.99 20.63 62.96 62.18 74.28 53.09 24.47 14.63 11.57 

11.76 10.79 18.09 19.19 31.88 37.31 128.42 168.90 161.35 114.19 60.25 47.51 

11.88 11.46 18.05 20.99 28.71 47.66 128.42 160.13 135.90 84.72 53.10 43.66 

11.14 11.06 18.90 25.12 29.07 61.32 150.60 153.36 128.49 72.62 48.68 35.87 

48.03 

47.84 

56.49 

60.74 

77.34 

74.25 

67.23 

82.48 

120.33 

104.02 

60.81 

52.69 

49.24 

29.89 

63.90

I 

1994 II 

III 

I 

1995 II 

III 

I 

1996 II 

III 

I 

1997 II 

AVG 

III 

I 

II 

III 

33.79 31.34 29.60 32.82 42.23 77.28 101.56 100.86 89.87 60.82 40.75 27.08 

31.46 29.98 26.72 41.06 43.53 102.32 107.69 98.52 90.00 54.08 33.59 24.77 

31.78 32.15 33.80 37.68 53.54 118.77 109.74 105.94 77.77 49.51 28.07 23.42 

22.20 21.99 20.02 25.58 67.49 116.90 160.73 113.23 91.57 58.27 28.82 24.77 

22.44 21.92 18.99 31.69 104.19 125.03 134.83 114.25 82.00 56.73 32.92 22.05 

22.17 22.03 26.16 46.27 100.68 126.65 103.64 101.49 78.88 44.31 33.10 20.48 

17.65 19.19 19.01 21.58 56.82 64.66 108.66 99.56 93.41 68.16 50.80 28.93 

17.55 17.10 22.00 20.95 49.82 54.76 117.00 92.84 89.14 62.47 47.23 26.16 

18.55 18.72 23.45 46.62 68.94 97.79 104.14 93.57 77.52 55.83 42.00 24.06 

27.22 26.27 26.50 29.09 34.72 45.59 100.05 82.89 71.06 51.24 24.29 18.34 

25.90 26.18 27.80 28.92 39.94 64.99 86.60 101.13 80.48 33.59 22.44 17.89 

26.32 25.88 30.32 29.77 41.25 80.02 72.34 66.43 65.15 26.52 20.33 16.89 

22.46 20.85 24.40 33.11 49.52 83.95 136.23 128.04 109.35 75.24 44.10 28.93 

21.50 20.48 26.15 36.24 59.08 104.79 139.30 126.58 104.45 65.94 38.33 26.16 

20.45 21.36 28.36 42.37 71.22 126.93 136.15 125.96 87.53 54.34 33.96 24.06 

12 

57.05 

62.35 

53.79 

44.29 

63.83

Teesta - Ministry of Power

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