Panan - Ministry of Power

CHAPTER 

I 

TABLE OF CONTENTS 

DESCRIPTION 

Executive Summary 

Preliminary Feasibility Report 

Panan HE project (4 x 50 MW) 

PAGE NO. 

1-9 

II Background Information 10-17 

III Project Area 18-25 

IV Topographical & Geo-technical Aspects 26-32 

V Hydrology 33-52 

VI Conceptual Layout and Planning 53-63 

VII Power Potential Studies 64-94 

VIII Power Evacuation 95 

IX Environmental Aspects 96-119 

X Infrastructure 120-123 

XI Construction Planning & Schedule 124-130 

XII Cost Estimate 131-166 

XIII Economic Evaluation 167-174 

Plates 

Annexures

TITLE 

LIST OF DRAWINGS 



PLATE 

No. 

Preliminary Ranking Study Layout 1 

Cascade Development of Teesta River Basin 2 

Cascade Development of Tolung River Basin 3 

Geological Plan of the Project Area 4.1 

Vicinity Map 

6.1 

Layout Plan 6.2 

Layout Plan-Dam Area 6.3 

Layout Plan-Power House Area 6.4 

Water Conductor System L-Section 6.5 

Dam Upstream Elevation 6.6 

Dam Spillway & Non-Overflow Cross Section 6.7 

Typical Cross Section Of Constituents Of Water 

Conductor System & Diversion Tunnel 

6.8 

Single Line Diagram-Power Evacution 8.1

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 

Preliminary Ranking Study Report- By CEA 6.1 

Summary Record of the Discussion with CEA on 

Conceptual Layout 

Records of Discussions, CEA/CWC Comments 

and Replies 

6.2 

6.3

TITLE 

ANNEXURES 6.3 



No. 

Record Discussions on Power Potential Study 3-5 

Reply on CWC’s Comments on Hydrology 6-10 

Reply on General Comments of CEA 11-13 

Reply on comments on CMDD(E&NE), CWC 14-15 

Reply on Comments of SP&PA Division CEA 16-17

CHAPTER-I 

EXECUTIVE SUMMARY 

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Panan HE Project (4 x 50 MW) 

1.0 INTRODUCTION 

The Panan Hydroelectric Project located in North Sikkim district of Sikkim envisages 

utilization of the waters of the river Rangyong a tributary of river Teesta for power 

generation on a run of river type development, harnessing a head of about 322m. 

The project with a proposed installation of 200MW (4 x 50MW) would afford an annual 

energy generation of 762GWh in a 90% dependable year. The tariff from the project at 

present day cost would be Rs 1.99 per KWh(levellised). 

The diversion site is located at Latitude 27º33’ North, Longitude 88º27’ East. The dam 

site is approachable from Mangan-Lingza road. The dam site is at a distance of 1km from 

Lingza and 17km from Mangan, the head quarter of North Sikkim district. The nearest 

railhead is at New Jalpaiguri and airport at Bagdogra 

1.1 GENERAL PROJECT FEATURES 

The Panan HE Project envisages construction of : 

• a 50 m high concrete Dam across river Rangyong to provide a live storage of 

1.69mcum. with FRL at 1095m and MDDL at 1085m; 

• two intakes and two desilting chambers of size 225m(L) x 15m(W) x 20m(H) to 

remove silt particles of size 0.2mm and above; 

• a 8.5km long , 6m diameter head race tunnel terminating in a surge shaft; 

• a 75m high, 15m dia surge shaft; 

• 425m long, 3m dia two pressure shaft; 

• an underground power house having an installation of 4 Francis turbine 

generating units of 50 MW each operating under a net head of 312m; and

2 



• 500m long, 6m diameter tailrace tunnel to carry the power house release back to 

the river; 

The power generated from the project would be evacuated through 220KV double circuit 

lines to be connected at the pooling point near Teesta (III) HE project to feed power to 

National Grid. 

The salient features of the projects are as under: 

SALIENT FEATURES 

LOCATION 

State Sikkim 

District North Sikkim 

River Tolung Chu/ Rangyong 

Location of Dam Site Approx. 1.0km U/S of village Lingza 

Location of Power House Approx. 100m U/S of confluence of Tolung 

Chu and Rahi Chu 

Nearest Rail head New Jalpaiguri 

Nearest Airport Bagdogra 

Dam 88º27’00’’Longitude 

27º33’00’’ Latitude 

Power House 88º32’00’’ Longitude 27º31’00’’ Latitude 

HYDROLOGY 

Catchment area 592 km 2 

Design Flood (PMF) 2200 m 3 /sec

DIVERSION TUNNEL 

Diameter & Shape 8.5 m, Horse-shoe shaped 

Length 600 m 

Diversion Discharge ±400 m 3 /sec 

Diversion Tunnel Gate 2Nos, 3 m X 6.5 m 

COFFER DAMS 

Type Rockfill with Central clay core 

Maximum height of upstream coffer 20.0 m 

dam 

Maximum height of downstream 

coffer dam 

3 

10.0 m 



DAM 

Type Concrete Gravity with central spillway 

Dam Top EL. 1100 m 

River bed level at dam site EL.1050 m 

Maximum Dam height (above deepest 

foundation level) 

55 m 

Length of the Dam 100 m 

Dam height (above River bed level) 50 m 

Max. Dam Height ( above deepest 

foundation level) 

55m 

SPILLWAY 

Design flood (PMF) 2200 m 3 /sec 

Type Low level orifice Type 

Crest level of spillway EL1065 m 

Number & Size of the opening 4 Nos. 5m(W)X 8m(H)

RESERVOIR 

Full Reservoir Level (FRL) EL.1095 m 

Minimum draw down level (MDDL) EL1085 m 

Area under submergence at FRL 15.6 Ha 

Gross Storage 3.52 MCM 

Live Storage 1.69 MCM 

INTAKE 

Invert level EL.1075 m 

Number of Intakes Two 

Size of each Gate 4.5 m × 4.5 m 

Total Design discharge 72.60 m 3 /sec 

Stop logs 1Set of Stop log (4.5 m wide) 

Trash Rack Steel trash rack with m/c 

4 



DESILTING ARRANGEMENT 

Type & Numbers Dufour type, 2 Nos. 

Length 225 m. 

Design Discharge 44 m 3 /sec each ( including 20% flushing 

discharge) 

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

Size 15m(W) x 20m(H) 

SILT FLUSHING TUNNEL 

Size & Shape 2m x 3 m

HEADRACE TUNNEL 

Size & Shape 6.0 m dia, Horse shoe 

Length 8.5 km 

Adits 3 No., 6 m dia D-shaped 

SURGE SHAFT 

Size 15 m dia. 

Height 75 m 

PRESSURE SHAFT 

Number Two 

Type Circular, steel lined 

Diameter 

3 m 

Height (including horizontal portion) 425 m 

POWER HOUSE COMPLEX 

Type and location Under ground, right bank 

Tail water level at outlet EL 770 m 

Centre line of M/C +763 m 

Type of Turbine Vertical Francis 

Gross head 322m 

Rated Net head 312 m 

Design Discharge 72.6 m 3 /sec 

Power House Size 120m X 22m X 45m 

TAILRACE TUNNEL 

Size & Type 6.0m dia, Horse-shoe 

Length 500m 

5 


Panan HE Project (4 x 50 MW)

POWER GENERATION 

Installed capacity 200 MW ( 4 x 50MW) 

Annual Energy generation in a 90% 762MU 

dependable 

COST ESTIMATES & FIANANCIAL ASPECTS ( Rs. Crores) 

Civil Works 554.10 

Electro Mechanical Works 209.17 

Sub Total (Generation) 763.27 

Transmission Works 1.67 

Total (Hard Cost) 764.94 at June,2003 Price Level 

Interest During Construction 81.14 

Grand Total 846.08 

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 

6 

Rs. 2.45 

Rs. 2.15 

Rs. 1.99 

Rs. 1.75 

COSTRUCTION PERIOD 5 years 

1.2 STUDIES/INVESTIGATIONS UNDERTAKEN 

• Study of topographic maps and remote sensing imageries 



• 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. 

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• 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. The dam location has 

been fixed after observing the rock exposures on both the banks and in the riverbed. 

Similarly, the underground powerhouse has been fixed after observing the competency of 

rock and its cover. 

1.3.2 Hydrology 

The river Rangyong drains a catchment area of about 592sq.km at the proposed dam site. 

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 

Panan dam site has been derived from the above data on the basis of catchment area 

proportion and applying an overall reduction factor of 77 %. The computed inflow series 

works out has been utilized for Power Potential Studies. The design flood has been 

assessed as 2200cumecs. 

1.3.3 Power Potential Studies 

The computed inflow series for 21 years viz June 1976 to May 97 has been considered in 

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

8 



year 1976-77 corresponds to 90% dependable year. An installation of 200MW 

comprising 4 generating units of 50MW 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) 762 

Annual Load Factor (%) 42 

Generation during Lean Flow Season (Sept II – Jan I) 

Energy Output (GWh) 342.73 

Load Factor (%) 26 

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

worked out at 762 GWh. 

A pondage of 1.69 mcum has been provided in the diversion dam which would enable the 

station to operate as peaking station. The pondage is equivalent to 1293.2 MWh which 

sufficient to operate the station for 3 hours. 

1.3.4 Power Evacuation Aspects 

The power generated from the project would be evacuated through 220 KV,double circuit 

line to be connected at the pooling point assumed to come up 2km from Teesta (III) HE 

project which shall be connected to National Grid. 

1.3.5 Environmental Aspects 

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

construction of various components is about 105ha. 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.

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1.3.6 Estimates Of Cost 

The project is estimated to cost Rs. 846.08 crores 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 is given below: 

Civil works : Rs. 554.10 crores 

Electro Mechanical Works : Rs. 209.17 crores 

Sub Total Cost (Generation) : Rs. 763.27 crores 

Transmission Works : Rs. 1.67 crores 

Total (Hard Cost) : Rs. 764.94 crores 

Interest During Construction : Rs. 81.14 crores 

Grand Total : Rs. 846.08 crores 

1.3.7 Financial Aspects 

As indicated above, the Panan HE project with an estimated cost of Rs. 846.08 crores 

(including IDC of Rs. 81.14 crores) and design energy of 762 GWh 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. 2.45/KWh & Rs. 

1.99/KWh respectively. 

1.3.8 Conclusion 

The Panan HE project involves simple civil works and could be completed in 5 years. 

The project would afford a design energy of 762 GWh in a 90% dependable year. The 

cost per MW installed work out Rs.3.82. The Preliminary Feasibility Report indicates 

that the scheme merit consideration for taking up for Survey & Investigation and 

preparation of DPR. 

.

CHAPTER –II 

BACKGROUND INFORMATION 

10 



2.1 GENERAL INFORMATION 

2.1.1 Introduction 

The Himalayan state of Sikkim, which in 1975, has elected to join the Indian Union to 

become 22 nd state. 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 other. Rangit also

11 



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 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

12 



200m. The Rongnichu, which drains the Changu lake area joins Teesta from left at 

Singtam and the river receives Ranpo 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 hydroelectric 

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 Feasibility Reports. The 

work of preparation of PFR’s was entrusted by Ministry of Power under overall

13 



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 Panan is one of the such scheme for 

PFR. 

2.1.5.2 About The Project 

The project is located on the river Rangyong Chu / Tolung Chu in Dzongu area of North 

Sikkim district of Sikkim. The headquarter of the district North Sikkim is at Mangan. 

The project involves construction of a 55 m high concrete dam, a 8.5 Km long headrace 

tunnel and an underground powerhouse with an installed capacity of 200 MW. The 

project shall generate 762 MU of energy in a 90% dependable year. The dam site is 

located about 1500 m d/s of the confluence of river Rangyang Chu and Ringyong Chu 

and 1000m u/s of village Linza. The underground powerhouse is located about 100 m u/s 

of the confluence of Tolung Chu and Rahi Chu near the village Panan. The village Linza 

nearest to dam site, is well connected from Mangan by 17 km long state PWD road. 

Panan , the nearest village to powerhouse site, is at a distance of 8.0 km from Mangan. 

Mangan falls on Gangtok– Chungthang state highway at 73 Km from Gangtok the 

Capital of Sikkim and about 160 km from New Jalpaiguri Railway Station and 175 km 

from Bagdogra airport. 

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 generating 

capacity installed in the country has already grown to 107903.53 MW by March 2003.

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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 interconnected 

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 

Gird, providing even greater reliability. 

The proposed Panan Hydro Electric Project located in North Sikkim is envisaged to be 

connected to feed the power at a pooling point near Teesta ( III) HE Project through one 

220KV double circuit line. 

2.2.2 Power Position in East Sikkim Region 

The total Installed Capacity in Eastern Region is 16696.68 MW. Out of this only 

2459.51MW 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 10th and 11th Five Year Plans is 

summarized in Table 2.1. The power and energy availability & requirements during and 

after 10th Plan period in the Eastern Region is shown in Tables as projected in the 16th 

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 10th

15 



five Year Plan. The power situation in the region is dynamic and it is 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 1927 for the needs 

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

an installed capacity of 12MW was constructed by Govt. of Sikkim and this was a big 

boom. Presently following hydel schemes totaling 95.70MW are under operation in the 

state. 

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

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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 

2.2.3 Load Demand & Power Position of Eastern Grid 

Table 2.1 shows the power supply position of Eastern grid up to 2011-12. 

2.3 NECESSITY OF THE PROJECT AND RELATED ASPECTS 

The need for Panan 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 off the river 

scheme in Teesta basin in North Sikkim District, Sikkim. It will generate 762 MU in 90% 

dependable year (1976-77) with 95% machine availability. The power generated at Panan 

H. E. Project (4 X 50 MW) will be fed to a pooling point near Teesta (III) HE Project ( 

approximate 2km from Teesta (III) through one 220KV double circuit line.

POWER SUPPLY POSITION OF EASTERN REGION 

10th Plan 11th Plan 

17 


Panan HE Project, (4 x 50 MW) 

Table 2-1 

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 

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

EnergySurplus(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.

1 


Panan HE Project, (4 x 50 MW)

CHAPTER –III 

PROJECT AREA 

18 



3.1 DESCRIPTION OF PROJECT INCLUDING RIVER SYSTEM 

Panan H.E. Project is situated in the Dzongu area of North Sikkim district of Sikkim .The 

project envisages construction of 55 m high concrete gravity dam at about 1.0 km 

upstream of village Lingza and an under ground powerhouse near the village Panan. The 

river water shall be diverted through a diversion tunnel of 600 m long and 8.5 m dia for 

construction of dam. A headrace tunnel of 8.5km length, 6.0m dia shall carry 72.6 cumec 

of water to the powerhouse. Two numbers of desilting chambers of 225mX15mX20 m 

size shall be constructed to separate the silt particles of 0.2mm size and above from the 

water. A surge shaft of 15 m dia and 75m deep along with two pressure shaft of 3.0m dia 

425 m deep shall be constructed. A tailrace tunnel of 500m length and 6.0m dia shall 

discharge the water back into the river. The powerhouse shall have installed capacity of 

200 MW to generate 762MU of energy in a 90% dependable year. 

The river Rangyong / Tolung Chu are the tributaries of the Teesta river originating in the 

glaciers of North Sikkim at an elevation of about 6500 m above mean sea level. The main 

tributaries of the Tolung Chu are Umram Chu, Passaram Chu, Rangyang Chu ,Ringpi 

Chu, Rangli Chu and Rahi Chu. The Ringpi Chu meets Rangyong Chu upstream of the 

confluence of Rangli Chu. Both the river Rahi Chu and Rangyong Chu meets Teesta 

river near village Singhik . After running about 14 Km from the confluence, the Dikchu 

River joins the Teesta River near the village 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 nontribal 

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

19 



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 consist of Nepalese. The people from the plain, 

mostly involved in trade and services, represent a marginal group. As per the 2001census 

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

the State is 76 per sq. Km. East district is the most populated where as North's density 

only 7 and is the least populated. Sex ratio (females per thousand male) in 1981 was 835, 

where as 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 2001 census is 48.52%. 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 hold economy of the 

region. There are certain household industries also which substantially adds to house hold 

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.

20 



The area in the vicinity of the project is populated. The human settlements are scattered 

and the human population as per the 1991 census up to different aerial distances from the 

project are given in Table 3.1 below. 

Table 3.1: Human settlement and Population around the project vicinity 

Item Up to 2 km from Up to 2-5 km Up to 5-10 km 

Population 2575 3141 6448 

Households 463 1171 1316 

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 Health & Education 

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

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

9 Veterinary hospitals and 25 Veterinary dispensaries. There is a blood bank at 

Gangtok. There are 1234 doctors. Small pox and Kalzor have been eliminated from the 

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

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

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

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

2 Degree colleges, one Industrial Training Institution, a Medical and an Engineering 

college.

21 



3.2.4 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. 

3.2.5 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 two distilleries , one tannery, and other ancillary 

units. Rangpo area has been declared as an industrial Zone. A Brewery is located at 

Melli, South Sikkim. and another at Rangpo, East Sikkim. There is also a fruit 

preservation factory at Singtam. The Sikkim Mining Corporation mines copper, zinc, lead 

etc in the state. 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 

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, zoo lists 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.

22 



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 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. 

3.2.6 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 

It is possible to diver the water of Teesta river d/s of confluence Chento chu near 

Shacham and d/s of confluence Lhonak chu and Poke chu by constructing diversion 

structures at EL ± 3330 and interconnecting tunnels discharging the Tail water at an EL ± 

2623 near the place Zema. The scheme will have installed capacity of about 320 MW.

23 



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. 

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.

24 



Rangit Basin 

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 

1569 MW for preparation of prefeasibility reports as per details given below: 

Sl. Name of Scheme Installed Name of 

District 

No. 

Capacity (MW) River 

1. Dikchu 105 Bakchachu/Dikchu chu East 

2. Rongni 195 Rongni chu East

25 



3. Namlum 160 Rangit South 

4. Panan 200 Tolung chu North 

5. Lingza 160 Ringpi North 

6. Rangyong 141 Rangyong/ Umramchu North 

7. Ringpi 70 Ringpi North 

8. Rukel 33 Rukel/Rangyong North 

9. Jedang 185 Jhonak chu North 

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

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. Name of Scheme Installed Capacity Name of River 

No. 

(MW) 

1. KalepHE Project 40 Teesta 

2. Talem HE Scheme 65 Teesta 

3. Serum HE Scheme 50 Lachung Chu 

4. Lachung HE Scheme 30 Lachung 

5. Chhota Pathing/Rolep 55 Rangpo Chu 

6. Chuzachen 13 Rangpo Chu 

7. Suntalitar HE Scheme 25 Rangpo Chu 

8. Mana 37 Rangit 

9. Gompa 46 Rangit 

10. Rammam Stage-I 70 Rammam 

11. Rammam Stage-II 85 Rammam 

12. Rammam Stage-III 100 Rammam 

13 Chakhung Chu hydel 30 Chakhung Chu 

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

small schemes for hydropower development in the region.

CHAPTER-IV 

26 



TOPOGRAPHIC AND GEOTECHNICAL ASPECTS 


Central Electricity Authority had proposed construction of Panan Hydroelectric Scheme, 

on Tolung Chu a right bank tributary of river Teesta, meeting Teesta near Sankalang. The 

scheme envisaged construction of a diversion structure near village Lingza, a 7.5km long 

water conductor system and a powerhouse on the right bank of river Teesta. This 

powerhouse would be located down stream of confluence of river Teesta and Tolung 

Chhu and tail water would be discharged into river Teesta. The scheme was expected to 

generate about 230 MW of power. The task of preparation of pre-feasibility report was 

given to NHPC. As per the MOU, GSI reports and site visits of experts would form major 

input for topographic and geotechnical aspects. The GSI report titled “Geology of The 

Area Around The Proposed Panan Hydroelectric Project, Teesta Basin, Sikkim” has now 

been received and accordingly the geology of the project has been modified. The GSI 

report is enclosed as Annexure-4.1. 

A study of DPR of Teesta stage-IV project was undertaken. This project envisages 

construction of a dam at about 150m downstream of confluence of Teesta and Tolung 

Chu. FRL of this scheme has been kept at 768M. The powerhouse of Panan scheme 

(CEA proposal) was proposed downstream of the dam of stage-IV. Also powerhouse of 

Teesta stage project envisaged in the upstream will discharge tail water on Tolung Chhu. 

As a sequel to these the powerhouse of Panan scheme had to be relocated with the tail 

water discharging in Tolung Chu above the FRL level of stage-IV scheme and upstream 

of the tail water of Teesta stage (IV) project. 

The area is approachable by a fair-weather road from Mangan which crosses river Teesta 

near Sankalang and runs in the right bank of Tolung Chhu upto village Kayem and

27 



beyond in the left bank of the river passing through village Lingza. Further, a road 

reaches village Laven (Right Bank), which is located in the downstream of the proposed 

diversion structure. Village Laven was unapproachable during the current visit. 

4.2 Regional Geology and tectonic setup 

Teesta is a major river flowing in Sikkim and West Bengal. The river originates from 

Zemeu glaciers and generally flows in north-south direction, at a steeper gradient. Several 

tributaries join the river and major amongst these being Yumthang, Zemu, Talung Chu, 

Dik Chu and Rangpo Chu. The area has a rugged terrain with the peaks reaching a 

maximum of 6000M. The regional geological aspects have been provide by GSI, and 

these are appended as Annexure-4.1. However, stratigraphic succession brought out by 

GSI is provided hereunder. 

Group Lithology 

Gondwana 

Daling 

Chungthan 

Central Crystalline 

Gneissic Complex 

Grits, pebble cum boulder beds and carbonaceous shales 

with occasional coal seams, pegmatite, quartzite 

(Tourmaline bearing) 

Interbedde quartzite and chlorite sericite phyllite / schist. 

Quartzite/ Biotite schist 

Interbedded quartzite and garnetiferous biotite schist. 

Calc-silicate rock/marble 

Garnet-kyanite-Sillimanite-biotite-quartz-schist. 

Banded gneiss with augen gneiss and quartz-biotite gneiss. 

Augen gneiss

28 



4.3 Topographic and Geotechnical Aspects of Component Structures 

Tolung Chu by generally flows in southeasterly direction. The area exhibits sharp and 

rugged hills with steep inaccessible rocky scarps. Steep slopes on both sides bind the 

river valley. In general the river flows along the strike of formations in cascades and has 

developed few falls. In vicinity of diversion axis, the river flows in a steep and deep 

gorge (Photo-1) while towards the downstream the river valley becomes wider. The left 

slopes are dissected by deep drainages namely Rangli Chu, Tadung Chu and Rahi Chu. 

Few high level terraces have been observed in this area especially in vicinity of Lingza 

and Kayem village. Generally thick vegetal cover occupies the area. 

4.3.1 Diversion Structure 

The proposed diversion structure is located about 1km upstream of village Lingza, on 

Tolung Chu (Photo-1). At the proposed axis the river flows easterly within a narrow and 

deep gorge. Further downstream of confluence of Ringpi Chhu and Ringyong Chhu, 

which is located in close proximity, Tolung Chhu flows in a step gradient and has 

developed a fall. Towards the downstream the river valley becomes broader (Photo-2). 

Both the banks rise steeply at about 70°-75°. Upstream of the axis the river flows in 

cascades in a steeper gradient. Both banks appear to be fairly stable. The riverbed is 

occupied by river borne material, which is about 6-8m thick. At the proposed axis 

gneissic rocks are exposed along h the right bank. Towards the left bank, which was 

inaccessible during the visit the rocks appear to be gneissic. The gneisses are strong to 

very strong. The formations generally trend NE-SW and dip northweasterly at about 45- 

60° (Plate-4.1). Towards downstream a wide terrace is observed which is used for 

cultivation purposes. Upstream of the proposed axis the slopes are occupied by a thin 

veneer of slope wash material. Since the area in vicinity of proposed diversion structure 

shows steep rock exposures the need for geophysical surveys was not felt.

29 



4.3.2 Water Conductor System 

Approximately 9 Km long water conductor system in the right hill has been proposed, to 

carry the water from the reservoir to the powerhouse. This tunnel will pass below 

Lingdem village. The proposed water conductor system is expected to be housed within 

gneisses and quartz biotite schists (Plate-4.1). Few thin bands of quartzites may also be 

expected. A part of the tunnel shall be sub-parallel to the principal discontinuity. The 

rock types trend NW-SE dipping NE at 45-60°. Fair to good tunneling media is expected 

during tunneling. The tunnel area at places especially downstream of Lingdem, Kayem 

and Lingthem is occupied by debris material. Thickness of this debris material may be 

ascertained during feasibility stage to assess the extent of rock cover above the water 

conductor system and the alignment be suitably modified. Few slides have been observed 

above the tunnel alignment especially in and around Village Lingdem. The tunnel area is 

occupied by a few small drainages as is observed form topographic maps. 

4.3.3 Powerhouse 

The powerhouse location was fixed keeping in view the FRL of Teesta Stage-IV project 

and tail water level of Teesta stage-III project. The area was studied in detail. A wide 

terrace has been deposited on the right bank below the suspension, here, which was 

considered for locating a surface powerhouse. Since, the area shall be submerged due to 

impoundment of stage-IV dam, this alternative was rejected. Alternately, an underground 

powerhouse has been proposed in the right hill upstream of confluence of Tolung Chhu 

and Rahi Chhu. This are is bound by steep hill, which shows rock exposures. This area is 

thickly vegetated. Towards the upstream the area is occupied by few slides, which shall 

require suitable treatment. At the proposed location the slopes are steep and quartz biotite 

schists/gneisses are exposed. In this area the rock type is under a veneer of slope wash 

material. The rock formations trend NW-SE dipping northeasterly (Plate-1) and are 

expected to provide a fair to good tunneling media. However, the schists are weaker and 

when charged with water these may pose a few problems. Few bands of quartzites have 

also been noticed towards the downstream of the proposed powerhouse. Towards the

30 



tailrace portion the area is occupied by overburden cover and construction of the same 

may interfere with the existing road. Since the area shall be submerged by Teesta stage- 

IV project the tail water level shall be kept at appropriate level. 

4.4 Seismicity 

The site lies within Zone-IV of seismic zonation map of India IS 1893 (Part-I) 2002. IMD 

data for the region covering longitude 86 0 -90 0 and latitude 25 0 -29 0 has been analyzed. 

Table-I 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). 

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. 

It is worthwhile to mention here, that at Teesta Stage-V, Sikkim, site-specific earthquake 

studies were conducted. The Panan scheme lies very close to Teesta-V project and 

earthquake parameters of Teesta-V project can be considered for initial design of the 

project components. However, site-specific studies for the scheme are recommended. 

An account of seismicity of the area has been provided by IMD in Annexure-4.2.

31 



4.5 GEO-PHYSICAL SURVEY 

At dam site, the rock is exposed on the both banks. The power house site is also having 

sufficient rock exposures and hence the Geophysical survey was not done. Moreover, the 

site was not approachable most of the time in rainy season. 

4.6 CONSTRUCTION MATERIAL SURVEY 

Few terraces near village Lingza can be utilized as construction material. However, 

quarries in nearby hills can be developed for the purpose of obtaining construction 

material. 

4.7 RECOMMENDATIONS 

The present studies are based on limited field traverses, as the area was mostly 

inaccessible. Hence, the following aspects need to be taken up during the feasibility 

studies. 

• Geological mapping of the project components needs to be taken up besides 

carrying out subsurface investigations at the dam and powerhouse location to 

ascertain the bedrock characteristics and abutment conditions. 

• Availability of construction material is required to be carried out in detail. The 

material is required to be tested for its suitability as construction material. .Further 

material obtained from excavation of various underground structures can be 

utililised after ascertaining its suitability.

Lingza Village 

32 

Proposed Axis 

Photo-1 View of Tolung Chu in Vicinity of Proposed Diversion Axis 

Photo-2 View of Proposed Powerhouse Area of Panan Scheme on Tolung 



5.1 GENERAL 

CHAPTER – V 

HYDROLOGY 

33 



Panan scheme is a run of the river scheme, proposed on Tolung chu/Rangyong Chu near 

village Lingza. The project envisages construction of a diversion structure about 1 km 

upstream of village Lingza, a water conductor system in the right bank and a power house 

located in the right bank of Teesta upstream of its confluence with Tolung Chu.The 

hydrological investigations and analysis have been carried out for Panan 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. 

5.2 RIVER SYSTEM AND BASIN CHARACTERSTICS 

Talung chu is one of the major tributary of river Teesta, which meets Teesta at Singhik 

on its right. Talung Chu originates from the Talung glacier, which is a part of the 

Kanchenjunga range. 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 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

34 



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. Tolung Chu is known as Rangyong Chu at the site of proposed diversion 

structure.The total length of Tolung Chu / Rangyong Chu from origin upto proposed 

diversion structure is about 30km. Tolung Chu has a very steep gradient with a slope of 

about 1 in 80 in the vicinity of proposed diversion structure and an average slope of 1 in 

12. 

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

of approximately 4000m. The nallah joins Teesta river almost perpendicularly. 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. The proposed diversion scheme on Tolung Chu is located 

within a deep gorge in a narrow valley of about 25-30m width. The right bank slopes are 

generally laid at about 70 0 while the left banks are laid at about 75 0 for about 60m height 

beyond which a 50-60m wide terrace has been developed. Further uphill the left bank 

slopes rise at an angle of about 60 0 . Upstream of the axis the river flows in cascades in a 

steeper gradient. 

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

35 



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 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 168 MW respectively. 

The proposed Panan H.E project on Tolung Chu, lies downstream of Chungthang, 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 10′00” E to 

88 o 32′00” E and Latitude 27 o 30′00” N to 28 o 45’00” N. The catchment area upto the 

proposed dam site is about 592 Sq.km. The catchment is both snowfed as well as rainfed. 

The proposed diversion structure lies at Longitude 88 o 27′00” E and latitude 27 o 33′00” N. 

The deepest riverbed elevation at the proposed diversion structure is 1050m. The 

catchment Plan is shown in Plate-5.1. 

The catchment plan has been prepared from 1:50000, Survey of India toposheets. The 

entire catchment is covered in toposheets no. 78A/6, 78A/7 and 78A/2. The area above 

EL4600m is about 148 Sq.km and has been assumed to be the snowfed area in the 

catchment. Thus the rainfed and snowfed area in the catchment is 444 Sq.km and 148 

Sq.km respectively. 

5.2.3 Temperature And Humidity 

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

36 



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 down in steep gradient, heavy rains in the upper and middle 

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

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

37 



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 annual 

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

proposed scheme comprises the upper and middle portions only.

38 



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 stations in 

the catchment upto Teesta-V H.E project is shown in Table 5-3.

Table 5-3 

39 



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 1974, 

Jan to Apr 83 

7. Dikchu (near Teesta- 

V dam site) 

8. Gayzing 1978 to 1988 

9. Yoksam 1978 to 1988 

10 Rangit dam site 1991 to 1997 

1992 to 1997, 2001 to Feb 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. 

5.3 WATER AVAILABILITY STUDY 

5.3.1 Stream flow and River gauges 

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

40 



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-III, Teesta-V, and Teesta Low 

Dam projects, Stage-III & IV. The various G&D sites and period of data availability in 

Teesta Basin is shown in Table 5-4. 

Table 5-4 

S.No Name of site River Period 

availabilty 

of 

1. Chunthang (before 

confluence of Lachung & 

Lachung Chu) 

2. Chungthang (after 

confluence of Lachung & 

Lachung Chu) 

3. 

Lachen 

Chu 

Third Mile Tolung 

Chu 

4. Lachung Lachung 

Chu 

5. Chuba Yumtha 

ng Chu 

6. Zema Zema 

Chu 

Catchment 

Area 

(Sq.km) 

Jan 75 to Aug 85 1919.25 

Teesta Jan 75 to Jun 86 2786.8 

Jan 75 to Aug 85, 

Apr 90 to Apr 98 

731.25 

May 76 to Aug 85 634.50 

Jan 78 to Aug 85 355.5 

Jan 79 to Aug 85 900.0 

7. Sankalang Teesta Dec 89 to May 98

. 

8. Dikchu (near Teesta-V 

damsite) 

9. Sirwani (Power house 

site-TeestaV) 

10. Legship 

damsite) 

(near Rangit 

Teesta Jan 84 to Oct 91, 

Nov91 to Mar97, 

Jan 00to Oct01, 

Sep02 to Feb 03 

Teesta May 84 to Mar 97, 

2000 

Rangit Jan 77 to Dec 79, 

Apr 87 to Dec 87, 

Jan 90 to Dec 91 

11. Teesta Bazar Teesta 1972 to 1994 

41 



4307 

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 

8065 

5.3.2 Present Study 

For the pre feasibility study, water availability for the proposed project has been 

computed based on the following methodologies: 

(i) The proposed diversion structure for Panan project is located on Tolung 

Chu/Rangyong chu river which is a major tributary of Teesta. At the site of 

diversion structure the river is known as Rangyong Chu while little downstream it 

is known as Tolung Chu. Daily G&D data is available on Tolung Chu from Jan 75 

to Aug 85 and Apr 90 to Apr 98. The site lies downstream of the proposed 

project, having a catchment area of 731 Sq.km. Average 10-daily series has been 

prepared based on this observed data and reduced to dam site using catchment 

area proportion, using a reduction factor of 0.76. 

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

Chungthang has been converted at proposed site using catchment area reduction

42 



(catchment reduction factor – 0.53). Thus a series for the period 1976 to 1984 has 

been obtained. 

(iii) G&D data observed at Lachen has been converted at proposed site using 

catchment area reduction (catchment reduction factor – 0.77). 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. 

(iv) The 10-daily series recommended for Teesta-V H.E project for the period 1976- 

1996 has been converted at proposed damsite using catchment area reduction 

(catchment reduction factor – 0.22). 

Average 10-daily for all the above four series developed is worked out and compared. 

The plot showing this comparison of average 10-daily at Panan is enclosed at Figure-5.1. 

From the plot it is obvious that the average 10-daily of the series obtained on the basis of 

G&D data observed on Tolung Chu is on a much higher side as compared to other three 

series. For pre-feasibility study, no consistency checks have been made for this observed 

data on Tolung Chu and hence the series so obtained cannot be adopted as such, it 

comparatively being on a higher side. Average 10-daily obtained from other three 

approaches are almost comparable. For pre-feasibility stage, the average 10-daily 

obtained from G&D data at Lachen is recommended for Panan H.E. project. This has 

been adopted as Lachen G&D site is nearer to Panan site and also has a smaller 

catchment area as compared to Chungtahng and Teesta-V. The final 10-daily series at 

Panan is enclosed as Annexure-5.2. 

5.4 RESERVOIR ELEVATION AREA CAPACITY CURVE 

The reservoir elevation-area-capacity curve for Panan 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 1080m. The elevation at the proposed dam axis is about 

1050m as read from the toposheets. The area enclosed within the contours has been found

43 



using Autocad. Area has been found from elevation 1080m to 1240m at an interval of 

40m. The volume between any two elevations is calculated using the formula : 

V = H * (A1+A2+√A1A2)/3 

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 is enclosed as Figure-5.2. The curve may be improved after 

receiving toposheets in scale of 1:25000. 

5.5 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 

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

44 



(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 = 14 x 592 3/4 

= 1680 cumec 

(ii) Ali Nawab Jung formula 

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

Where C = 49 to 60 (55 used) 

Q = 55* (0.386*592) (0.925-1/14log(592)) 

= 2853 cumec 

(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. Panan H.e project is located 

on Tolung Chu river which is a major tributary of Teesta river and both the catchments 

are hydrologically and hydro-meteorologically similar. Therefore, it seems logical to 

transpose the design flood value of Teesta-III to proposed dam at Panan. This 

transposition has been done by Dicken’s formula using a conversion factor of 0.313. 

Q Panan = Q Teesta-III * (A Panan/A Teesta-III) 0.75 

= 1431 cumec 

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

formula 

The design flood for Panan 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 Panan project, having a catchment area of 592 

Sq.km comes out to be 0.226.

Q Panan = Q Teesta-V * (A Panan/A Teesta-V) 0.75 

= 2145 cumec 

45 



A comparative study of flood peak computed from various methods is placed as Table 5- 

5. For pre-feasibility stage study, a design flood of 2200 cumec has been recommended 

at proposed dam site. 

Table 5.5 

Comparison Of Various Flood Values 

S.No Method used Design Flood 

(cumec) 

1. Dickens Formula 1680 

2. Ali Nawaz Jung Formula 2853 

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. 

1431 

2145 

On availability of more data/information, design flood will 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. This silt 

rate may be adopted for Panan H.E. project too. Detailed sediment study will be done 

during feasibility stage with more observed data at the proposed site using a suitable 

method.

49 



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

AVERAGE 10-DAILY DISCHARGE 

50 



Annexure 5.2 

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

I 17.37 16.13 18.87 25.61 30.30 48.13 87.13 73.67 78.21 27.90 22.12 13.31 

1976 II 16.63 15.84 20.23 28.03 23.99 93.93 83.03 80.31 45.10 22.04 18.32 11.39 37.15 

III 15.82 16.52 21.94 32.78 33.64 68.15 63.20 85.85 32.93 22.25 16.38 10.52 

I 9.38 15.73 8.69 16.69 18.20 51.76 76.32 87.83 60.26 50.15 26.19 16.31 

1977 II 8.92 15.32 12.40 15.66 22.48 91.83 89.80 73.90 49.28 31.62 23.89 17.23 37.01 

III 8.54 9.18 11.51 16.65 32.03 66.78 107.55 86.29 41.09 25.26 18.04 19.49 

I 13.41 12.41 11.31 16.11 27.85 76.46 89.06 109.05 57.39 54.03 28.77 20.37 

1978 II 12.01 12.15 12.09 20.63 57.09 80.23 95.47 92.15 74.73 42.13 21.46 17.26 43.70 

III 12.27 11.17 13.41 24.44 66.65 101.44 92.13 69.18 56.17 35.91 21.12 15.50 

I 14.30 11.81 13.16 25.04 46.88 54.47 97.05 96.11 79.16 84.45 43.09 31.46 

1979 II 13.20 11.79 13.78 24.90 59.76 65.18 92.84 75.88 69.08 57.63 35.09 25.91 46.99 

III 12.97 12.82 16.96 31.24 45.71 93.46 104.00 80.48 50.67 43.22 33.03 24.95 

I 23.51 21.53 24.74 38.48 53.63 74.98 118.19 128.09 111.92 55.55 37.57 29.25 

1980 II 22.63 22.56 25.37 49.36 45.87 99.79 120.99 140.66 87.73 47.73 34.21 26.59 59.82 

III 22.43 24.06 34.26 56.23 48.89 111.68 126.76 117.15 71.01 44.47 31.49 24.15 

I 23.27 20.02 24.62 30.82 56.47 65.12 135.07 106.24 104.32 65.33 45.04 27.32 

1981 II 21.81 20.59 26.08 39.03 60.99 77.89 115.83 112.11 89.40 60.47 35.94 24.57 57.43 

III 21.53 24.90 30.79 45.99 59.15 105.73 108.94 108.98 71.26 52.85 29.77 19.26 

I 17.69 19.25 20.25 33.93 47.11 90.75 97.01 86.15 73.62 49.46 31.33 23.38 

1982 II 19.69 20.00 22.67 33.88 52.91 99.95 108.68 81.55 106.47 41.54 27.33 21.56 52.00 

III 19.42 19.44 27.00 37.58 51.40 110.48 128.20 95.71 69.86 40.00 26.46 20.41 

I 20.24 11.49 17.08 29.05 47.84 95.92 148.79 102.79 102.35 93.33 51.28 32.37 

1983 II 18.02 11.42 21.89 23.75 57.33 93.09 126.58 109.00 115.08 92.01 47.11 30.35 63.80 

III 12.63 15.89 19.74 29.73 76.29 129.92 125.58 127.34 132.74 62.72 38.80 27.20

51 




I 24.27 20.48 45.11 52.07 63.01 135.95 168.98 161.63 174.74 111.42 81.14 39.95 

1984 II 23.89 21.27 50.41 55.51 92.09 163.48 169.53 162.06 166.76 141.33 70.12 39.31 93.07 

III 21.26 20.43 49.54 55.52 130.83 146.81 179.22 169.66 132.28 108.88 62.32 39.46 

I 39.81 35.77 50.28 61.04 62.60 64.93 181.10 160.58 84.58 58.20 34.11 22.37 

1985 II 37.81 32.70 54.46 73.66 72.65 81.06 236.32 169.39 80.80 51.01 29.65 20.24 80.46 

III 32.74 39.58 50.71 86.99 101.19 229.69 198.71 207.38 67.70 42.03 26.27 18.61 

I 17.65 16.79 21.08 23.17 31.50 42.91 93.39 93.15 77.83 63.46 34.07 23.43 

1986 II 17.56 17.28 22.95 29.96 33.50 72.78 116.69 80.07 96.67 47.46 30.31 21.58 47.59 

III 16.62 19.78 23.56 33.61 35.30 107.83 104.96 88.65 78.69 37.06 26.18 15.91 

I 13.89 11.63 11.80 32.07 33.48 72.49 101.37 102.60 134.61 61.32 31.70 16.02 

1987 II 13.08 11.52 14.00 22.40 37.23 105.29 96.91 111.95 72.01 45.67 19.34 14.66 48.41 

III 12.26 12.64 17.58 29.61 43.70 88.36 108.36 74.82 98.76 39.06 16.99 13.41 

I 13.08 12.68 15.30 26.64 35.78 57.30 141.13 121.26 80.62 51.35 22.60 18.05 

1988 II 13.08 13.28 22.66 30.09 53.61 82.91 110.87 111.31 54.38 34.07 20.40 17.12 50.61 

III 12.92 14.75 23.30 34.99 71.04 90.82 122.19 168.87 60.82 27.41 19.01 16.20 

I 9.92 10.64 11.76 12.81 32.30 72.18 128.75 102.30 76.32 54.25 23.36 15.04 

1989 II 9.65 9.72 11.99 15.34 33.36 119.57 126.65 80.26 69.13 46.17 18.96 13.04 47.04 

III 9.56 10.35 12.32 18.39 81.29 126.45 117.89 78.74 68.68 37.55 17.24 11.42 

I 10.41 8.60 7.13 6.12 18.48 79.11 99.60 92.56 80.08 44.75 22.95 13.12 

1990 II 9.65 8.08 5.82 10.11 32.57 77.28 126.97 94.03 76.69 45.59 17.15 10.82 40.75 

III 8.74 7.80 5.92 12.52 37.46 90.37 108.67 83.45 53.41 37.50 14.32 9.33 

I 9.45 8.89 9.11 28.74 29.11 42.00 69.65 84.81 81.34 53.14 28.66 16.25 

1991 II 9.27 8.45 10.39 16.39 35.47 66.32 67.86 97.71 85.93 42.14 25.34 12.46 38.09 

III 9.17 8.54 10.95 17.34 39.24 60.99 73.96 80.74 66.56 34.58 19.33 10.96 

I 9.98 8.94 8.86 10.83 13.64 17.63 41.84 52.64 50.40 31.01 13.98 11.19 

1992 II 8.28 8.62 8.92 15.22 15.88 25.13 42.34 52.85 49.61 22.24 12.42 9.69 23.12 

III 8.46 8.27 9.17 13.91 15.96 48.70 48.10 57.46 41.06 18.93 11.32 8.95 

I 9.10 8.34 13.99 14.84 24.66 28.86 99.34 130.65 124.81 88.33 46.60 36.75 

1993 II 9.19 8.86 13.96 16.23 22.20 36.87 99.34 123.86 105.12 65.54 41.08 33.77 49.43 

III 8.62 8.56 14.62 19.43 22.48 47.43 116.49 118.63 99.39 56.17 37.66 27.74

52 




I 26.13 24.25 22.90 25.39 32.66 59.78 78.56 78.02 69.52 47.05 31.52 20.95 

1994 II 24.34 23.19 20.67 31.76 33.67 79.15 83.30 76.20 69.62 41.83 25.98 19.16 44.13 

III 24.58 24.87 26.14 29.14 41.41 91.87 84.89 81.95 60.15 38.30 21.71 18.12 

I 17.17 17.01 15.49 19.79 52.20 90.43 124.33 87.59 70.83 45.07 22.29 19.16 

1995 II 17.36 16.95 14.69 24.52 80.59 96.71 104.29 88.37 63.43 43.88 25.46 17.06 48.23 

III 17.15 17.04 20.24 35.79 77.87 97.96 80.17 78.51 61.02 34.28 25.60 15.84 

I 13.65 14.85 14.70 16.69 43.95 50.02 84.05 77.01 72.26 52.72 39.29 22.37 

1996 II 13.57 13.23 17.02 16.21 38.53 42.35 90.50 71.81 68.95 48.32 36.53 20.24 43.54 

III 14.34 14.48 18.14 36.06 53.33 75.64 80.56 72.38 59.97 43.19 32.49 18.61 

I 21.05 20.32 20.49 22.50 26.86 35.26 77.39 64.12 54.96 39.64 18.79 14.18 

1997 II 20.03 20.25 21.50 22.37 30.89 50.27 66.99 78.23 62.25 25.98 17.36 13.84 34.26 

III 20.36 20.01 23.45 23.03 31.91 61.90 55.95 51.39 50.39 20.51 15.73 13.06 

I 17.37 16.13 18.87 25.61 38.30 64.93 105.38 99.04 84.58 58.20 34.11 22.37 

AVG II 16.63 15.84 20.23 28.03 45.70 81.06 107.75 97.91 80.80 51.01 29.65 20.24 49.37 

III 15.82 16.52 21.94 32.78 55.09 98.18 105.32 97.43 67.70 42.03 26.27 18.61

1 



Discharge (cumec) 

180.00 

160.00 

140.00 

120.00 

100.00 

80.00 

60.00 

40.00 

20.00 

0.00 

Jan I 

II 

III 

Feb I 

II 

III 

Mar I 

II 

PANAN H.E PROJECT 

Comparison of average 10-daily discharge at Panan 

III 

Apr I 

II 

III 

May I 

II 

III 

Jun I 

II 

47 

III 

Jul I 

II 

Period 

III 

Aug I 

II 

III 

Sep I 

II 

Transferred from Chunthang 

Transferred from Lachen 

Transferred from observed data at Tolung Chu 

Transferred from Teesta-V 

III 

Oct I 

II 

III 

Nov I 

II 

III 

Dec I 

II 

III 

Figure 5.1

S.No 

Elevation 

(m) 

Area 

(sq.km) 

Volume 

(Mcum) 

1 1050 0.00 0.00 

2 1080 0.10 0.98 

3 1120 0.25 7.75 

4 1160 0.52 22.85 

5 1200 0.87 50.31 

6 1240 1.27 92.93 

Elevation (m) 


RESERVOIR ELEVATION AREA CAPACITY CURVE 

100.00 

1240 

1220 

1200 

1180 

1160 

1140 

1120 

1100 

1080 

1060 

90.00 

80.00 


Reservoir Elevation Area Capacity curve 

1040 

1040 

0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.10 1.20 1.30 

Area (Sq.km) 

48 

70.00 

Capacity (Mcum) 

60.00 

50.00 

40.00 

30.00 

20.00 

10.00 

0.00 

1240 

1220 

1200 

1180 

1160 

1140 

1120 

1100 

1080 

1060 

Elevation (m) 

Figure 5.2

Discharge (cumec) 

180.00 

160.00 

140.00 

120.00 

100.00 

80.00 

60.00 

40.00 

20.00 

0.00 

Jan I 

II 

III 

Feb I 

II 

III 

Mar I 

II 


Comparison of average 10-daily discharge at Panan 

III 

Apr I 

II 

III 

May I 

II 

III 

Jun I 

II 

III 

Jul I 

II 

Period 

III 

Aug I 

II 

III 

Sep I 

II 

Transferred from Chunthang 

Transferred from Lachen 

Transferred from observed data at Tolung Chu 

Transferred from Teesta-V 

III 

Oct I 

II 

III 

Nov I 

II 

III 

Dec I 

II 

III

CHAPTER – VI 

CONCEPTUAL LAYOUT AND PLANNING 

53 




The Panan H.E. project is located in North Sikkim district of Sikkim at 1Km U/S of 

village Lingza. It is a run of the river scheme proposed to harness hydel potential of the 

Tolung Chu, a tributary of river Teesta. A maximum gross head of the order of 325 m 

between Dam site and Power House is proposed to be utilised for power generation. The 

powerhouse will have an installed capacity of 200 MW. A small reservoir of adequate 

capacity has been provided as an operating pool to meet diurnal peaking load demands. 

6.2 PROJECT COMPONENTS 

• 6.5 m diameter, 600 m long Diversion Tunnel with u/s & d/s coffer dam 

• 50 m high & 100m long concrete Dam with a central spillway 

• Intake Structure leading to 2 Nos. 4.5-m dia D-shaped intake tunnels. 

• Two Nos. Underground Desilting Chambers of size 225m (L) x 15m (W) x 

18m(H) 

• One 6.0-m diameter horseshoe shaped concrete lined and 8.5 kms long Head Race 

Tunnel with three adits. 

• One 15 m diameter & apprx. 75 m high semi-Underground Surge Shaft. 

• Two circular Pressure Shaft of 3.0m diameter, 425m long each further bifurcating 

into 2 numbers steel lined circular penstocks of 1.6 m diameter & 35 m long each 

upto Power House. 

• Underground Power House of size 120m x 22m x 45m consisting of 4 Francis 

units of 50 MW each. 

• One no. 6.0m diameter Horseshoe shaped tailrace tunnel of about 500 m length.

54 



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. 

6.3 CONCEPTUAL LAYOUT 

The choice of location of the dam has been made keeping in view the topography, 

geology and maximum water availability at the various locations of the diversion 

structure near the one suggested earlier by CEA.The location of the power house has 

been fixed keeping the tailrace outlet at EL 770 m taking into consideration the FRL of 

the proposed Teesta H E Project (Stage-IV) which is 768.00m. 

The location of major component of the project, riverbed levels at dam site, TRT outlet 

site and generation capacity of the project as identified in the ranking study undertaken 

by CEA in 1990 have been taken into account during the preparation of this report. Also, 

the ongoing/upcoming hydroelectric projects on Teesta river of which Panan is a tributary 

have been taken into consideration in the conceptual planning of the project. 

The layout plan of the project and a brief write up by CEA during ranking study are 

enclosed as plate-1 and annexure 6.1 respectively and the cascade development schemes 

on the Teesta River as prepared by CEA are enclosed as plate -2. 

Based on the hydrological and topographical study, reconnaissance survey of the site 

input data of ranking study; a conceptual layout plan of the project was prepared and 

discussed in CEA for vetting during sept’03. The minutes of meeting is enclosed as 

annexure- 6.2. 

6.3.1 Dam and River diversion works 

Construction of 50-m high concrete Dam has been proposed across river Tolung Chu 

near village Lingza. Width of the valley at Dam site varies from 50 m at riverbed level to 

100 m at EL1100 m. Average bed level at Dam site is EL 1150 m. FRL is proposed to

55 



be fixed at EL 1095 and MDDL at El.1085 m keeping in view the inflow of water in 

Tolung Chu during lean period. The top of the dam has been proposed at EL 1100 m and 

seat of the dam is proposed to be kept at EL 1045 m after removal of approx. 5.0 m thick 

overburden. Near the dam axis, both the banks slopes rise at about 70º and the rocks are 

exposed .The rock types comprise gneiss/schist. 

The overflow section is 44 m long. and Non –overflow section is 56m The spillway has 

four bays each of size 5 m X 8 m with 3.0 m wide piers. The spillway is designed to pass 

a probable maximum flood of 2200 cumecs with one gate inoperative. The crest of 

spillway has been kept 35 m below the dam top i.e. at EL1065 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. Out of 100 m dam length, 56 m length 

of dam constitutes as non-overflow section comprising 16m on right abutment and 40m 

on left abutment. The top width of non-overflow section is 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 

project area falls within Zone-IV of seismic zoning map. The availability of construction 

material for the dam, cofferdam and its suitability has been discussed elsewhere in the 

report. 

One no. Concrete lined 6.5 m dia 600 m long diversion tunnel has been proposed on the 

left bank of the river to divert a flood of approx. 500 cumecs of Tolung chu. 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 date shall required 

to be firmed up during the preparation of feasibility / detailed project report with the 

availability of more hydrological data & experience gained during the erection of Teesta- 

IV project just d/s of the scheme In order to divert the river during construction of the 

dam, an u/s coffer dam of apprx. height 20m and d/s cofferdam of 10m heights is 

proposed.

56 



The reservoir formed by construction of Dam has a gross storage pre-sedimentation 

capacity of 3.52M.cum and live storage capacity of 1.69M cum. After sedimentation, the 

reservoir is likely to have a live storage capacity of more than what is adequate for 

running the power station at full capacity for four to six hours in a day during the period 

of lean flows. 

6.3.2 Power Intake & Desilting Chambers 

The proposed power intake system is on the right side of the river and consists of two no. 

intake and two no. D-shaped intake tunnels of dia 4.5 m each. Each tunnel will carry 

discharge of 36.3 cumec. 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 intake structures are 

designed to pass 88 cumecs, which is about 20% excess of turbine discharge of 

72.6cumecs. The invert level of the intake structure has been kept as 1075m taking into 

consideration the water seal requirement to prevent the vortex formation and air 

entrainment. Also, this level being 10m higher than the spillway crest, it is ensured that 

entry of sediments shall be reduced in the water conductor system. The intake structure 

shall be provided with the trash racks to prevent the entry of trash in 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. The racks shall be cleaned by a mechanical raking machine operated 

from El.1100m 

For the efficient, trouble free and continuos operation of turbines with least possible 

wearing and erosion damages due to silt, it is necessary to remove 90% of the sediments 

larger than 0.2mm-particle size. Two nos. 15 m wide Dufour type Desilting chambers 

with height 20m shall be provided to remove 90% of particles having size greater than or 

equal to 0.2m. Two separate intakes lead the water to two independent desilting chambers 

225 m long spaced at 30 m c/c, through 25 m long upstream transition which will 

gradually reduce the velocity of water in the chamber to 0.25 m /sec. The chambers have

57 



been provided with central gutter with holes to facilitate the flushing of settled silt 

particles through the flushing tunnel. 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 2m x 3.0m 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. The requirement of desilting chambers is being foreseen, as the 

TEESTA-V project, which is d/s of this project The alignment and orientation of the 

chambers can be optimized after more geological and topo-graphical data become 

available. 

6.3.3 Head Race Tunnel, Surge Shaft, and Pressure Shaft 

The proposed 6.0 m diameter concrete lined horseshoe shaped headrace tunnel of 8.5 

km length, and having a slope of 1 in 300 is designed to carry a design discharge of 72.6 

cumec. The diameter has been fixed keeping the velocity of water within 3.0m/s in the 

tunnel. Invert level of headrace tunnel is fixed at EL. 1075m near intake. The rock cover 

above headrace tunnel generally varies from +100 m to +500 m. The low cover reaches 

are confined to prominent nalla crossings. The HRT shall be aligned with in the rock type 

of schist and gneiss. Three nos. constructions Adits are proposed to facilitate excavation 

of headrace tunnel within the scheduled completion time. The length of tunnel between 

550m long adit-1 & 450 m long adit-2 is 3Km, between adit-2 & 500 m long adit-3 is 3.5 

Km. The tunnel is proposed to be lined with 300 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. 

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 elevation EL 

+1150 m. Surge shaft is proposed to be concrete lined with 0.75 m thick R.C.C. Its 

bottom is kept at EL 1070m at the HRT and surge shaft junction. The transient studies

58 



shall be required to be done to work out the maximum and minimum levels for the worst 

conditions. 

Two no. Steel lined circular Pressure Shaft of 3m diameter and 850 m length takes off 

from the surge shaft each further bifurcating into 2 numbers underground steel lined 

circular penstocks of 1.6 m diameter and 150 m length upto Power House which will feed 

water to 4 units of Francis turbines each of 50 MW. 

6.3.4 Power House Complex & Tail Race Tunnel 

The underground Power House is located on the right bank of Tolung Chu River near 

village Panan about 100m upstream of confluence of Tolung Chu and Rahi Chu. It will 

have an installed capacity of 200MW (4 generating units of 50 MW each). The units are 

spaced at a distance of 20 m center to center. The centerline of the turbine is proposed at 

about EL 763m. The deepest level of the tailrace pit is at EL753m. One number 

electrically operated overhead traveling crane (E.O.T) of apprx.150 MT capacity shall be 

provided for handling the electrical and mechanical equipment. The Main inlet valve 

chamber is proposed on the u/s of the powerhouse. A lift shall be provided near the 

service bay for the transportation of men and material. The overall dimension of the 

Power House is length 120m, width 22 m, and height 45 m. A Control block area shall 

be located on one end of machine hall. The transformer cavern cum draft tube gate shaft 

is proposed 30m d/s of powerhouse cavern. The approx. size is 100mx 14m x 25m. 

A cable tunnel of size 2.0 m x 3.0 m will take off from transformer area and shall carry 

cables to the Pothead yard. The Pothead yard shall measure 100 m x 40 m, which shall 

be formed in cutting/filling. 

Water from the turbines is discharged through four draft tubes, which merges into a 

single tailrace tunnel of diameter 6.0m in the Tolung Chu. This tunnel is 6.0 m diameter 

horseshoe and about 500m long with invert at EL.768 at tailrace outlet. The tailrace outlet

59 



level has been kept so, in view the FRL of proposed Teesta H E Project (Stage-IV) which 

is768.00m. The reservoir of Teesta-IV shall extend beyond the junction of the Tolung 

Chu and Teesta River on the u/s side. 

6.4 FURTHER STUDIES 

6.4.1 Topographical Studies 

1. Topographical contour Survey of the dam area 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 riverbed survey at Dam axis and tailrace outlet shall be undertaken to firm up the 

power potential of the project. 

6.4.2 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. 

6.4.3 Design Studies 

1. Hydraulic design of various structures like spillway, power intake, desilting 

chambers, transient studies of surge shaft 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.

60 



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. 

6.5 HYDRO- MECHENICAL EQUIPMENT 

6.5.1 Diversion Tunnel Gate And Hoist 

After the construction of the dam, for the purpose of plugging the diversion 

tunnel, two numbers fixed wheel type gates 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 & designed 

for operation against water height corresponding to coffer dam height i.e. 20m. 

6.5.2 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.

61 



One set of stoplog has been envisaged to cater to the maintenance requirement 

of four nos. spillway radial gates. The spillway stoplog shall be lowering / raising 

under balanced head condition by means of a suitable Capacity Gantry crane 

with the help of a lifting beam. 

6.5.3 Trash Rack And Trash Rack Cleaning Machine 

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. 

6.5.4 Intake Gate, Bulkhead Gates And Hoists 

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 upstream water level corresponding to FRL. The gate shall be operated 

by means of electrically operated rope drum hoist of suitable capacity. 

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. 

6.5.5 Desilting Chamber Gate 

One set of slide type gate has been envisaged to cater to the maintenance 

requirement of two nos. desilting chambers. The gate shall be lowering / raising 

under balanced head condition by means of a suitable Capacity EOT Crane. 

6.5.6 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

62 



hydraulic hoists. The gate grooves are provided with bonnet structures 

embedded in the concrete & a watertight bonnet cover at the top of the groove. 

6.5.7 Surge Shaft Gate And Hoist 

The intake of pressure shaft is provided with two numbers slide type gates. The 

gate shall be operated under balanced head condition by means of an electrically 

operated rope drum hoist. 

6.5.8 Draft Tube Gates And Hoists 

To isolate turbines from the tailrace tunnel to cater to the inspection / 

maintenance requirements of turbines, four nos. fixed wheel type draft tube gates 

(one for each unit) have been envisaged. The gates shall be operated under 

balanced head conditions by suitable capacity rope drum hoist. 

6.5.9 Tailrace Gate And Hoist 

One set of slide type bulk head gate to isolate tailrace tunnel has been 

envisaged. The slide 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. 

6.5.10 Adit Inspection Gates 

Three nos. adits 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. 

6.5.11 Pressure Shaft Steel Liner 

Two no. Pressure Shaft of dia. 3000 mm fully steel lined will take off from Surge 

Shaft to feed the turbine placed in the powerhouse. It comprises horizontal &

63 



vertical ferrules, 2 nos. vertical bends, 2 nos. plan bends, 1 no. bifurcations 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. 

6.5.12 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. 

6.5.13 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 

64 



7.1 GENERAL 

The Power potential studies of Panan 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) =1095 m 

MDDL (EL) =1085 m 

TWL = EL 770M 

Rated net head= 312 m 

Type of turbine = Vertical Francis 

Speed = 500 RPM 

Rated Discharge of Plant=72.60 cumecs 

Proposed Plant Capacity= 200 MW (4x50 MW) 

Design Energy =761.71 MU in the 90% dependable year with 95% 

machine availability 

Minimum Peaking (Hrs) = 3 hrs (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.

65 



90% Dependable Year: 

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. Here no reservoir capacity has been selected in 

order to have minimum environmental impact. During lean inflow period (winter 

season) the firm power comes out to be 23.52 MW. 

7.4 FULL RESERVOIR LEVEL (FRL) AND MINIMUM DRAW DOWN LEVEL 

(MDDL) 

FRL and MDDL have been fixed at EL 1095m & EL 1085 m respectively based 

on civil consideration. This project is envisaged as a run of the river scheme. 

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 10 m. 

Net operating head = FRL-1/3 (FRL-MDDL)-TWL (all units running)- 

Head losses 

The net operating head comes out to 312 m.

66 



7.6 INSTALLED CAPACITY 

The studies for power output and annual energy generation for the 90% 

dependable year has been given in Tables 7.4. Considering water availability the 

total installed capacity has been selected as 200 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 with capacity each of 50 MW with Francis 

turbine as prime mover has been envisaged, however detailed optimization 

studies for fixation of installed capacity would have to be done at FR/ DPR stage. 

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 7.5 and 7.2. It may be 

seen from this table that the total unrestricted energy generation is 838.70 MU. 

Annual energy generation at 200 MW comes out to be 761.71 MU. Incremental 

benefits have been shown in Table 7.6 which comes out to be 1.71 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 752.6 MU 

after allowing auxiliary consumption of 0.7% and transformer losses of 0.5% 

respectively.

Month 

JUNE 

JULY 

AUGUST 

SEPTEMBER 

OCTOBER 

NOVEMBER 

DECEMBER 

JANUARY 

FEBRUARY 

MARCH 

APRIL 

MAY 

1976- 

1977 

1977- 

1978 

1978- 

1979 

1979- 

1980 

1980- 

1981 

1981- 

1982 

1982- 

1983 

HYDROLOGICAL SERIES 

1983- 

1984 

67 

1984- 

1985 

1985- 

1986 

1986- 

1987 

1987- 

1988 

1988- 

1989 

1989- 

1990 

1990- 

1991 

1991- 

1992 

1992- 

1993 

1993- 

1994 



1-10 48.13 51.76 76.46 54.47 74.98 65.12 90.75 95.92 135.95 64.93 42.91 72.49 57.30 72.18 79.11 42.00 17.63 28.86 59.78 90.43 50.02 

11-20 1 93.93 91.83 80.23 65.18 99.79 77.89 99.95 93.09 163.48 81.06 72.78 105.29 82.91 119.57 77.28 66.32 25.13 36.87 79.15 96.71 42.35 

21-30 2 68.15 66.78 101.44 93.46 111.68 105.73 110.48 129.92 146.81 229.69 107.83 88.36 90.82 126.45 90.37 60.99 48.70 47.43 91.87 97.96 75.64 

1-10 Jan-00 87.13 76.32 89.06 97.05 118.19 135.07 97.01 148.79 168.98 181.10 93.39 101.37 141.13 128.75 99.60 69.65 41.84 99.34 78.56 124.33 84.05 

11-20 4 83.03 89.80 95.47 92.84 120.99 115.83 108.68 126.58 169.53 236.32 116.69 96.91 110.87 126.65 126.97 67.86 42.34 99.34 83.30 104.29 90.50 

21-31 5 83.03 107.55 92.13 104.00 126.76 108.94 128.20 125.58 179.22 198.71 104.96 108.36 122.19 117.89 108.67 73.96 48.10 116.49 84.89 80.17 80.56 

1-10 Jan-00 73.67 87.83 109.05 96.11 128.09 106.24 86.15 102.79 161.63 160.58 93.15 102.60 121.26 102.30 92.56 84.81 52.64 130.65 78.02 87.59 77.01 

11-20 7 80.31 73.90 92.15 75.88 140.66 112.11 81.55 109.00 162.06 169.39 80.07 111.95 111.31 80.26 94.03 97.71 52.85 123.86 76.20 88.37 71.81 

21-31 8 85.85 86.29 69.18 80.48 117.15 108.98 95.71 127.34 169.66 207.38 88.65 74.82 168.87 78.74 83.45 80.74 57.46 118.63 81.95 78.51 72.38 

1-10 Jan-00 78.21 60.26 57.39 79.16 111.92 104.32 73.62 102.35 174.74 84.58 77.83 134.61 80.62 76.32 80.08 81.34 50.40 124.81 69.52 70.83 72.26 

11-20 10 45.10 49.28 74.73 69.08 87.73 89.40 106.47 115.08 166.76 80.80 96.67 72.01 54.38 69.13 76.69 85.93 49.61 105.12 69.62 63.43 68.95 

21-30 11 32.93 41.09 56.17 50.67 71.01 71.26 69.86 132.74 132.28 67.70 78.69 98.76 60.82 68.68 53.41 66.56 41.06 99.39 60.15 61.02 59.97 

1-10 Jan-00 27.90 50.15 54.03 84.45 55.55 65.33 49.46 93.33 111.42 58.20 63.46 61.32 51.35 54.25 44.75 53.14 31.01 88.33 47.05 45.07 52.72 

11-20 13 22.04 31.62 42.13 57.63 47.73 60.47 41.54 92.01 141.33 51.01 47.46 45.67 34.07 46.17 45.59 42.14 22.24 65.54 41.83 43.88 48.32 

21-31 14 22.25 25.26 35.91 43.22 44.47 52.85 40.00 62.72 108.88 42.03 37.06 39.06 27.41 37.55 37.50 34.58 18.93 56.17 38.30 34.28 43.19 

1-10 Jan-00 22.12 26.19 28.77 43.09 37.57 45.04 31.33 51.28 81.14 34.11 34.07 31.70 22.60 23.36 22.95 28.66 13.98 46.60 31.52 22.29 39.29 

11-20 16 18.32 23.89 21.46 35.09 34.21 35.94 27.33 47.11 70.12 29.65 30.31 19.34 20.40 18.96 17.15 25.34 12.42 41.08 25.98 25.46 36.53 

21-30 17 16.38 18.04 21.12 33.03 31.49 29.77 26.46 38.80 62.32 26.27 26.18 16.99 19.01 17.24 14.32 19.33 11.32 37.66 21.71 25.60 32.49 

1-10 Jan-00 13.31 16.31 20.37 31.46 29.25 27.32 23.38 32.37 39.95 22.37 23.43 16.02 18.05 15.04 13.12 16.25 11.19 36.75 20.95 19.16 22.37 

11-20 19 11.39 17.23 17.26 25.91 26.59 24.57 21.56 30.35 39.31 20.24 21.58 14.66 17.12 13.04 10.82 12.46 9.69 33.77 19.16 17.06 20.24 

21-31 20 10.52 19.49 15.50 24.95 24.15 19.26 20.41 27.20 39.46 18.61 15.91 13.41 16.20 11.42 9.33 10.96 8.95 27.74 18.12 15.84 18.61 

1-10 Jan-00 9.38 13.41 14.30 23.51 23.27 17.69 20.24 24.27 39.81 17.65 13.89 13.08 9.92 10.41 9.45 9.98 9.10 26.13 17.17 13.65 21.05 

11-20 22 8.92 12.01 13.20 22.63 21.81 19.69 18.02 23.89 37.81 17.56 13.08 13.08 9.65 9.65 9.27 8.28 9.19 24.34 17.36 13.57 20.03 

21-31 23 8.54 12.27 12.97 22.43 21.53 19.42 12.63 21.26 32.74 16.62 12.26 12.92 9.56 8.74 9.17 8.46 8.62 24.58 17.15 14.34 20.36 

1-10 Jan-00 15.73 12.41 11.81 21.53 20.02 19.25 11.49 20.48 35.77 16.79 11.63 12.68 10.64 8.60 8.89 8.94 8.34 24.25 17.01 14.85 20.32 

11-20 25 15.32 12.15 11.79 22.56 20.59 20.00 11.42 21.27 32.70 17.28 11.52 13.28 9.72 8.08 8.45 8.62 8.86 23.19 16.95 13.23 20.25 

21-28 26 9.18 11.17 12.82 24.06 24.90 19.44 15.89 20.43 39.58 19.78 12.64 14.75 10.35 7.80 8.54 8.27 8.56 24.87 17.04 14.48 20.01 

1-10 Jan-00 8.69 11.31 13.16 24.74 24.62 20.25 17.08 45.11 50.28 21.08 11.80 15.30 11.76 7.13 9.11 8.86 13.99 22.90 15.49 14.70 20.49 

11-20 28 12.40 12.09 13.78 25.37 26.08 22.67 21.89 50.41 54.46 22.95 14.00 22.66 11.99 5.82 10.39 8.92 13.96 20.67 14.69 17.02 21.50 

21-31 29 11.51 13.41 16.96 34.26 30.79 27.00 19.74 49.54 50.71 23.56 17.58 23.30 12.32 5.92 10.95 9.17 14.62 26.14 20.24 18.14 23.45 

1-10 Jan-00 16.69 16.11 25.04 38.48 30.82 33.93 29.05 52.07 61.04 23.17 32.07 26.64 12.81 6.12 28.74 10.83 14.84 25.39 19.79 16.69 22.50 

11-20 31 15.66 20.63 24.90 49.36 39.03 33.88 23.75 55.51 73.66 29.96 22.40 30.09 15.34 10.11 16.39 15.22 16.23 31.76 24.52 16.21 22.37 

21-30 32 16.65 24.44 31.24 56.23 45.99 37.58 29.73 55.52 86.99 33.61 29.61 34.99 18.39 12.52 17.34 13.91 19.43 29.14 35.79 36.06 23.03 

1-10 Feb-00 18.20 27.85 46.88 53.63 56.47 47.11 47.84 63.01 62.60 31.50 33.48 35.78 32.30 18.48 29.11 13.64 24.66 32.66 52.20 43.95 26.86 

11-20 34 22.48 57.09 59.76 45.87 60.99 52.91 57.33 92.09 72.65 33.50 37.23 53.61 33.36 32.57 35.47 15.88 22.20 33.67 80.59 38.53 30.89 

1994- 

1995 

1995- 

1996 

TABLE 7.1 

21-31 35 32.03 66.65 45.71 48.89 59.15 51.40 76.29 130.83 101.19 35.30 43.70 71.04 81.29 37.46 39.24 15.96 22.48 41.41 77.87 53.33 31.91 

1996- 

1997

YEAR 

UNRESTRICTED 

ENERGY 

GENERATION 

MU 

Table No. 7.2 

CALCULATION FOR 90% DEPENDABLE YEAR 

YEAR 

UNRESTRICTED 

ENERGY IN 

DESCENDING 

ORDER 

1976-1977 838.70 1984-1985 2325.33 1 

1977-1978 968.36 1983-1984 1760.17 2 

1978-1979 1078.03 1985-1986 1636.45 

1979-1980 1245.68 1980-1981 1443.51 

1980-1981 1443.51 1981-1982 1347.72 

1981-1982 1347.72 1993-1994 1329.93 

1982-1983 1241.86 1979-1980 1245.68 

1983-1984 1760.17 1982-1983 1241.86 

1984-1985 2325.33 1987-1988 1224.20 

1985-1986 1636.45 1988-1989 1163.43 

9 

10 

1986-1987 1123.53 1986-1987 1123.53 11 

1987-1988 1224.20 1995-1996 1096.81 12 

1988-1989 1163.43 1994-1995 1092.11 13 

1989-1990 1072.05 1978-1979 1078.03 14 

1990-1991 1028.94 1989-1990 1072.05 15 

1991-1992 864.89 1990-1991 1028.94 16 

1992-1993 594.21 1996-1997 1011.07 17 

1993-1994 1329.93 1977-1978 968.36 18 

68 



RANK 

OF 

THE 

CALCULATION OF 90% DEPENDABLE 

YEAR 

YEAR 

3 

4 

5 

6 

7 

8 

N= No. of year 

90% Dependable Year 

=(N+1)*0.9th year 

=(21+1)*0.9th year 

=19.8th year 

=20th year (say) 

90% Dependable year is 1976-1977 

90% Dependable energy (unrestricted) 

is 838.70 MU 

90% Dependable energy 

whenpower is restricted 

to 200 MW is 761.71 

MU 

1994-1995 1092.11 1991-1992 864.89 19 90% DEPENDABLE YEAR IS 1976-1977 

1995-1996 1096.81 1976-1977 838.70 20 

1996-1997 1011.07 1992-1993 594.21 21

PERIOD 90% 

DEPENDABLE 

INFLOW 

CUMECS 

Table No. 7.3 

POWER GENERATION IN 90% DEPENDABLE YEAR (1976-77) 

UNRESTRI 

CTED 

POWER 

POWER IN MW ENERGY IN MU 

RESTRICTED 

TO INSTALLED 

CAPACITY 

69 

UNRESTRICTED 

ENERGY 



RESTRICTED 

ENERGY 

(MU) 

1 2 4 5 6 7 8 

MONTHLY 

ENERGY IN 

GWH 

Jun- 1-10 48.13 132.58 132.58 31.82 

124.88 

76 11-20 93.93 258.74 200.00 62.10 48.00 

21-30 68.15 187.74 187.74 45.06 45.06 

Jul- 1-10 87.13 240.01 200.00 57.60 48.00 148.80 

76 11-20 83.03 228.72 200.00 54.89 48.00 

21-31 83.03 228.72 200.00 60.38 52.80 

Aug- 1-10 73.67 202.93 200.00 48.70 48.00 148.80 

76 11-20 80.31 221.22 200.00 53.09 48.00 

21-31 85.85 236.49 200.00 62.43 52.80 

Sep- 1-10 78.21 215.44 200.00 51.71 48.00 99.59 

76 11-20 45.10 124.25 124.25 29.82 29.82 

21-30 32.93 90.71 90.71 21.77 21.77 

Oct- 1-10 27.90 76.86 76.86 18.45 18.45 49.19 

76 11-20 22.04 60.71 60.71 14.57 14.57 

21-31 22.25 61.28 61.28 16.18 16.18 

Nov- 1-10 22.12 60.94 60.94 14.63 14.63 37.56 

76 11-20 18.32 50.46 50.46 12.11 12.11 

21-30 16.38 45.11 45.11 10.83 10.83 

Dec- 1-10 13.31 36.67 36.67 8.80 8.80 23.98 

76 11-20 11.39 31.36 31.36 7.53 7.53 

21-31 10.52 28.98 28.98 7.65 7.65 

Jan- 1-10 9.38 25.85 25.85 6.20 6.20 18.31 

77 11-20 8.92 24.57 24.57 5.90 5.90 

21-31 8.54 23.52 23.52 6.21 6.21 

Feb- 1-10 15.73 43.32 43.32 10.40 10.40 25.38 

77 11-20 15.32 42.21 42.21 10.13 10.13 

21-28 9.18 25.29 25.29 4.86 4.86 

Mar- 1-10 8.69 23.93 23.93 5.74 5.74 22.31 

77 11-20 12.40 34.16 34.16 8.20 8.20 

21-31 11.51 31.71 31.71 8.37 8.37 

Apr- 1-10 16.69 45.98 45.98 11.04 11.04 32.40 

77 11-20 15.66 43.15 43.15 10.36 10.36 

21-30 16.65 45.85 45.85 11.01 11.01 

May- 1-10 18.20 50.14 50.14 12.03 12.03 50.19 

77 11-20 22.48 61.92 61.92 14.86 14.86 

21-31 32.03 88.24 88.24 23.29 23.29 

838.70 781.39 #REF! 

NOTE : The energy is calculated taking into consideration 95% machine availability

TABLE -7.4 

70 



POWER GENERATION IN 905DEPENDEBLE YEAR (1976-77) 

PERIOD INFLOW UNRESTR UNRESTR RESTRIC 95% m/c 

10 1-10 48.13 132.58 31.82 31.82 31.82 

Jun-76 10 11-20 93.93 258.74 62.10 48.00 45.60 

10 21-30 68.15 187.74 45.06 45.06 45.06 

10 1-10 87.13 240.01 57.60 48.00 45.60 

Jul-76 10 11-20 83.03 228.72 54.89 48.00 45.60 

11 21-31 83.03 228.72 60.38 52.80 50.16 

10 1-10 73.67 202.93 48.70 48.00 45.60 

Aug-76 10 11-20 80.31 221.22 53.09 48.00 45.60 

11 21-31 85.85 236.49 62.43 52.80 50.16 

10 1-10 78.21 215.44 51.71 48.00 45.60 

Sep-76 10 11-20 45.10 124.25 29.82 29.82 29.82 

10 21-30 32.93 90.71 21.77 21.77 21.77 

10 1-10 27.90 76.86 18.45 18.45 18.45 

Oct-76 10 11-20 22.04 60.71 14.57 14.57 14.57 

11 21-31 22.25 61.28 16.18 16.18 16.18 

10 1-10 22.12 60.94 14.63 14.63 14.63 

Nov-76 10 11-20 18.32 50.46 12.11 12.11 12.11 

10 21-30 16.38 45.11 10.83 10.83 10.83 

10 1-10 13.31 36.67 8.80 8.80 8.80 

Dec-76 10 11-20 11.39 31.36 7.53 7.53 7.53 

11 21-31 10.52 28.98 7.65 7.65 7.65 

10 1-10 9.38 25.85 6.20 6.20 6.20 

Jan-77 10 11-20 8.92 24.57 5.90 5.90 5.90 

11 21-31 8.54 23.52 6.21 6.21 6.21 

10 1-10 15.73 43.32 10.40 10.40 10.40 

Feb-77 10 11-20 15.32 42.21 10.13 10.13 10.13 

8 21-28 9.18 25.29 4.86 4.86 4.86 

10 1-10 8.69 23.93 5.74 5.74 5.74 

Mar-77 10 11-20 12.40 34.16 8.20 8.20 8.20 

11 21-31 11.51 31.71 8.37 8.37 8.37 

10 1-10 16.69 45.98 11.04 11.04 11.04 

Apr-77 10 11-20 15.66 43.15 10.36 10.36 10.36 

10 21-30 16.65 45.85 11.01 11.01 11.01 

10 1-10 18.20 50.14 12.03 12.03 12.03 

May-77 10 11-20 22.48 61.92 14.86 14.86 14.86 

11 21-31 32.03 88.24 23.29 23.29 23.29 

838.70 781.39 761.71 

Restricted Energy generated in 90% dependable year with 95% machine availability with installed capacity of 200 

MW = 761.71MU (say) 

Energy available at Bus – Bar after allowing auxiliary consumptions of 0.7% and transformer losses of 0.5% = 752.6 

MU

TABLE 7.5 

71 



POWER POTENTIAL IN 90% DEPENDABLE YEAR WITH 95% m/c AVAILABILITY 

1976-1977 

Net Head Restricted MW 200 Overall Efficiency 90% 

Period Inflow Head Power Unrestricted Power Energy Energy Energy during 

1-10 48.13 312.0 132.58 31.82 132.58 31.82 0.00 31.82 

Jun-76 

Jul-76 

Aug-76 

Sep-76 

Oct-76 

Nov-76 

Dec-76 

Jan-77 

Feb-77 

Mar-77 

Apr-77 

May-77 

11-20 93.93 312.0 258.74 62.10 200.00 48.00 48.00 0.00 

21-30 68.15 312.0 187.74 45.06 187.74 45.06 45.06 0.00 

1-10 87.13 312.0 240.01 57.60 200.00 48.00 48.00 0.00 

11-20 83.03 312.0 228.72 54.89 200.00 48.00 48.00 0.00 

21-31 83.03 312.0 228.72 60.38 200.00 52.80 52.80 0.00 

1-10 73.67 312.0 202.93 48.70 200.00 48.00 48.00 0.00 

11-20 80.31 312.0 221.22 53.09 200.00 48.00 48.00 0.00 

21-31 85.85 312.0 236.49 62.43 200.00 52.80 52.80 0.00 

1-10 78.21 312.0 215.44 51.71 200.00 48.00 48.00 0.00 

11-20 45.10 312.0 124.25 29.82 124.25 29.82 0.00 29.82 

21-30 32.93 312.0 90.71 21.77 90.71 21.77 0.00 21.77 

1-10 27.90 312.0 76.86 18.45 76.86 18.45 0.00 18.45 

11-20 22.04 312.0 60.71 14.57 60.71 14.57 0.00 14.57 

21-31 22.25 312.0 61.28 16.18 61.28 16.18 0.00 16.18 

1-10 22.12 312.0 60.94 14.63 60.94 14.63 0.00 14.63 

11-20 18.32 312.0 50.46 12.11 50.46 12.11 0.00 12.11 

21-30 16.38 312.0 45.11 10.83 45.11 10.83 0.00 10.83 

1-10 13.31 312.0 36.67 8.80 36.67 8.80 0.00 8.80 

11-20 11.39 312.0 31.36 7.53 31.36 7.53 0.00 7.53 

21-31 10.52 312.0 28.98 7.65 28.98 7.65 0.00 7.65 

1-10 9.38 312.0 25.85 6.20 25.85 6.20 0.00 6.20 

11-20 8.92 312.0 24.57 5.90 24.57 5.90 0.00 5.90 

21-31 8.54 312.0 23.52 6.21 23.52 6.21 0.00 6.21 

1-10 15.73 312.0 43.32 10.40 43.32 10.40 0.00 10.40 

11-20 15.32 312.0 42.21 10.13 42.21 10.13 0.00 10.13 

21-28 9.18 312.0 25.29 4.86 25.29 4.86 0.00 4.86 

1-10 8.69 312.0 23.93 5.74 23.93 5.74 0.00 5.74 

11-20 12.40 312.0 34.16 8.20 34.16 8.20 0.00 8.20 

21-31 11.51 312.0 31.71 8.37 31.71 8.37 0.00 8.37 

1-10 16.69 312.0 45.98 11.04 45.98 11.04 0.00 11.04 

11-20 15.66 312.0 43.15 10.36 43.15 10.36 0.00 10.36 

21-30 16.65 312.0 45.85 11.01 45.85 11.01 0.00 11.01 

1-10 18.20 312.0 50.14 12.03 50.14 12.03 0.00 12.03 

11-20 22.48 312.0 61.92 14.86 61.92 14.86 0.00 14.86 

21-31 32.03 312.0 88.24 23.29 88.24 23.29 0.00 23.29 

Energy obtained on 95% machine availability 781.39 438.66 342.73 

LOAD FACTOR 44.600 99.334 26.154

72 



S. 

No. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

TABLE 7.6 

72 



AVAILABILITY OF UNITS IN KWH/KW FOR INCREMENTAL INSTALLATION IN 90% 

DEPENDABLE YEAR 

1976-1977 

Design Discharge 72.60 

Net Head 312.00 

Overall 

Efficiency 

90% 

Installed 

Capacity MW 

Annual 

Energy 

MU 

Load 

Factor % 

80 491.39 70.12% 

100 549.89 62.77% 

120 603.65 57.42% 

140 651.85 53.15% 

160 696.01 49.66% 

180 740.17 46.94% 

200 781.39 44.60% 

220 815.56 42.32% 

240 834.20 39.68% 

260 838.70 36.82% 

280 838.70 34.19% 

Incremental 

Energy MU 

Incremental 

Energy 

Kwh/Kw 

Load Factor 

For Additional 

Capacity % 

58.50 2925.19 33.39% 

53.76 2688.00 30.68% 

48.20 2409.86 27.51% 

44.16 2208.00 25.21% 

44.16 2208.00 25.21% 

41.22 2060.91 23.53% 

34.17 1708.53 19.50% 

18.64 932.00 10.64% 

4.50 225.00 2.57% 

0.00 0.00 0.00%

INCREMENTAL∆MU/∆MW 

3.00 

2.50 

2.00 

1.50 

1.00 

0.50 

0.00 

PANAN H E PROJECT 

INCREMENTAL BENEFIT FOR 90% DEPENDABLE YEAR(1976-1977) 

2.93 

2.69 

2.41 

2.21 2.21 

73 

2.06 

1.71 

0.93 



40 60 80 100 120 140 160 180 200 220 240 260 280 300 

CAPACITY ( MW) 

0.23 

0.00

TABLE 7.7(A) 

1976-1977 

PERIOD FLOW UNRISTRICTED ENERGY 

MONTH CUMECS MU 

JUNE 1-10 48.13 31.82 

11-20 93.93 62.10 

21-30 68.15 45.06 

JULY 1-10 87.13 57.60 

11-20 83.03 54.89 

21-31 83.03 60.38 

AUGUST 1-10 73.67 48.70 

11-20 80.31 53.09 

21-31 85.85 62.43 

SEPTEMBER 1-10 78.21 51.71 

11-20 45.10 29.82 

21-30 32.93 21.77 

OCTOBER 1-10 27.90 18.45 

11-20 22.04 14.57 

21-31 22.25 16.18 

NOVEMBER 1-10 22.12 14.63 

11-20 18.32 12.11 

21-30 16.38 10.83 

DECEMBER 1-10 13.31 8.80 

11-20 11.39 7.53 

21-31 10.52 7.65 

JANUARY 1-10 9.38 6.20 

11-20 8.92 5.90 

21-31 8.54 6.21 

FEBRUARY 1-10 15.73 10.40 

11-20 15.32 10.13 

21-28 9.18 4.86 

MARCH 1-10 8.69 5.74 

11-20 12.40 8.20 

21-31 11.51 8.37 

APRIL 1-10 16.69 11.04 

11-20 15.66 10.36 

21-30 16.65 11.01 

MAY 1-10 18.20 12.03 

11-20 22.48 14.86 

21-31 32.03 23.29 

74

TABLE 7.7 (B) 

1977-1978 



JUNE 1-10 51.76 34.22 

11-20 91.83 60.71 

21-30 66.78 44.15 

JULY 1-10 76.32 50.46 

11-20 89.80 59.37 

21-31 107.55 78.21 

AUGUST 1-10 87.83 58.06 

11-20 73.90 48.86 

21-31 86.29 62.76 

SEPTEMBER 1-10 60.26 39.84 

11-20 49.28 32.58 

21-30 41.09 27.16 

OCTOBER 1-10 50.15 33.15 

11-20 31.62 20.91 

21-31 25.26 18.37 

NOVEMBER 1-10 26.19 17.32 

11-20 23.89 15.80 

21-30 18.04 11.93 

DECEMBER 1-10 16.31 10.78 

11-20 17.23 11.39 

21-31 19.49 14.18 

JANUARY 1-10 13.41 8.86 

11-20 12.01 7.94 

21-31 12.27 8.92 

FEBRUARY 1-10 12.41 8.21 

11-20 12.15 8.03 

21-28 11.17 5.91 

MARCH 1-10 11.31 7.48 

11-20 12.09 7.99 

21-31 13.41 9.75 

APRIL 1-10 16.11 10.65 

11-20 20.63 13.64 

21-30 24.44 16.16 

MAY 1-10 27.85 18.41 

11-20 57.09 37.74 

21-31 66.65 48.47 

75

TABLE 7.7(C) 

1978-1979 



JUNE 1-10 76.46 50.55 

11-20 80.23 53.04 

21-30 101.44 67.06 

JULY 1-10 89.06 58.88 

11-20 95.47 63.12 

21-31 92.13 67.00 

AUGUST 1-10 109.05 72.10 

11-20 92.15 60.92 

21-31 69.18 50.31 

SEPTEMBER 1-10 57.39 37.94 

11-20 74.73 49.40 

21-30 56.17 37.14 

OCTOBER 1-10 54.03 35.72 

11-20 42.13 27.86 

21-31 35.91 26.12 

NOVEMBER 1-10 28.77 19.02 

11-20 21.46 14.19 

21-30 21.12 13.97 

DECEMBER 1-10 20.37 13.46 

11-20 17.26 11.41 

21-31 15.50 11.27 

JANUARY 1-10 14.30 9.46 

11-20 13.20 8.72 

21-31 12.97 9.43 

FEBRUARY 1-10 11.81 7.81 

11-20 11.79 7.79 

21-28 12.82 6.78 

MARCH 1-10 13.16 8.70 

11-20 13.78 9.11 

21-31 16.96 12.33 

APRIL 1-10 25.04 16.55 

11-20 24.90 16.46 

21-30 31.24 20.65 

MAY 1-10 46.88 31.00 

11-20 59.76 39.51 

21-31 45.71 33.25 

76

TABLE 7.7 (D) 

1979-1980 



JUNE 1-10 54.47 36.01 

11-20 65.18 43.09 

21-30 93.46 61.79 

JULY 1-10 97.05 64.16 

11-20 92.84 61.38 

21-31 104.00 75.63 

AUGUST 1-10 96.11 63.54 

11-20 75.88 50.17 

21-31 80.48 58.53 

SEPTEMBER 1-10 79.16 52.34 

11-20 69.08 45.67 

21-30 50.67 33.50 

OCTOBER 1-10 84.45 55.83 

11-20 57.63 38.10 

21-31 43.22 31.43 

NOVEMBER 1-10 43.09 28.48 

11-20 35.09 23.20 

21-30 33.03 21.84 

DECEMBER 1-10 31.46 20.80 

11-20 25.91 17.13 

21-31 24.95 18.14 

JANUARY 1-10 23.51 15.54 

11-20 22.63 14.96 

21-31 22.43 16.31 

FEBRUARY 1-10 21.53 14.24 

11-20 22.56 14.92 

21-29 24.06 14.31 

MARCH 1-10 24.74 16.36 

11-20 25.37 16.77 

21-31 34.26 24.91 

APRIL 1-10 38.48 25.44 

11-20 49.36 32.63 

21-30 56.23 37.18 

MAY 1-10 53.63 35.45 

11-20 45.87 30.33 

21-31 48.89 35.56 

77

TABLE 7.7 (E) 

1980-1981 



JUNE 1-10 74.98 49.57 

11-20 99.79 65.97 

21-30 111.68 73.83 

JULY 1-10 118.19 78.13 

11-20 120.99 79.99 

21-31 126.76 92.19 

AUGUST 1-10 128.09 84.68 

11-20 140.66 93.00 

21-31 117.15 85.19 

SEPTEMBER 1-10 111.92 73.99 

11-20 87.73 58.00 

21-30 71.01 46.95 

OCTOBER 1-10 55.55 36.72 

11-20 47.73 31.56 

21-31 44.47 32.34 

NOVEMBER 1-10 37.57 24.84 

11-20 34.21 22.61 

21-30 31.49 20.82 

DECEMBER 1-10 29.25 19.34 

11-20 26.59 17.58 

21-31 24.15 17.56 

JANUARY 1-10 23.27 15.38 

11-20 21.81 14.42 

21-31 21.53 15.66 

FEBRUARY 1-10 20.02 13.23 

11-20 20.59 13.61 

21-28 24.90 13.17 

MARCH 1-10 24.62 16.28 

11-20 26.08 17.24 

21-31 30.79 22.39 

APRIL 1-10 30.82 20.38 

11-20 39.03 25.80 

21-30 45.99 30.40 

MAY 1-10 56.47 37.34 

11-20 60.99 40.32 

21-31 59.15 43.02 

78

TABLE 7.7 (F) 

1981-1982 



JUNE 1-10 65.12 43.05 

11-20 77.89 51.49 

21-30 105.73 69.90 

JULY 1-10 135.07 89.30 

11-20 115.83 76.57 

21-31 108.94 79.23 

AUGUST 1-10 106.24 70.23 

11-20 112.11 74.12 

21-31 108.98 79.25 

SEPTEMBER 1-10 104.32 68.97 

11-20 89.40 59.11 

21-30 71.26 47.11 

OCTOBER 1-10 65.33 43.19 

11-20 60.47 39.98 

21-31 52.85 38.44 

NOVEMBER 1-10 45.04 29.78 

11-20 35.94 23.76 

21-30 29.77 19.68 

DECEMBER 1-10 27.32 18.06 

11-20 24.57 16.25 

21-31 19.26 14.01 

JANUARY 1-10 17.69 11.70 

11-20 19.69 13.02 

21-31 19.42 14.12 

FEBRUARY 1-10 19.25 12.73 

11-20 20.00 13.22 

21-28 19.44 12.85 

MARCH 1-10 20.25 13.39 

11-20 22.67 14.99 

21-31 27.00 19.64 

APRIL 1-10 33.93 22.43 

11-20 33.88 22.40 

21-30 37.58 24.84 

MAY 1-10 47.11 31.14 

11-20 52.91 34.98 

21-31 51.40 37.38 

79

TABLE 7.7 (G) 

1982-1983 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 90.75 60.00 

11-20 99.95 66.08 

21-30 110.48 73.04 

JULY 1-10 97.01 64.14 

11-20 108.68 71.85 

21-31 128.20 93.23 

AUGUST 1-10 86.15 56.95 

11-20 81.55 53.92 

21-31 95.71 69.60 

SEPTEMBER 1-10 73.62 48.67 

11-20 106.47 70.39 

21-30 69.86 46.19 

OCTOBER 1-10 49.46 32.70 

11-20 41.54 27.46 

21-31 40.00 29.09 

NOVEMBER 1-10 31.33 20.71 

11-20 27.33 18.07 

21-30 26.46 17.49 

DECEMBER 1-10 23.38 15.46 

11-20 21.56 14.25 

21-31 20.41 14.84 

JANUARY 1-10 20.24 13.38 

11-20 18.02 11.92 

21-31 12.63 9.19 

FEBRUARY 1-10 11.49 7.60 

11-20 11.42 7.55 

21-28 15.89 8.40 

MARCH 1-10 17.08 11.29 

11-20 21.89 14.47 

21-31 19.74 14.36 

APRIL 1-10 29.05 19.21 

11-20 23.75 15.70 

21-30 29.73 19.66 

MAY 1-10 47.84 31.63 

11-20 57.33 37.90 

21-31 76.29 55.48 

80

TABLE 7.7 (H) 

1983-1984 



JUNE 1-10 95.92 63.42 

11-20 93.09 61.55 

21-30 129.92 85.89 

JULY 1-10 148.79 98.37 

11-20 126.58 83.68 

21-31 125.58 91.33 

AUGUST 1-10 102.79 67.96 

11-20 109.00 72.06 

21-31 127.34 92.60 

SEPTEMBER 1-10 102.35 67.67 

11-20 115.08 76.08 

21-30 132.74 87.76 

OCTOBER 1-10 93.33 61.70 

11-20 92.01 60.83 

21-31 62.72 45.61 

NOVEMBER 1-10 51.28 33.90 

11-20 47.11 31.14 

21-30 38.80 25.65 

DECEMBER 1-10 32.37 21.40 

11-20 30.35 20.06 

21-31 27.20 19.78 

JANUARY 1-10 24.27 16.05 

11-20 23.89 15.79 

21-31 21.26 15.46 

FEBRUARY 1-10 20.48 13.54 

11-20 21.27 14.06 

21-29 20.43 12.16 

MARCH 1-10 45.11 29.82 

11-20 50.41 33.33 

21-31 49.54 32.75 

APRIL 1-10 52.07 34.42 

11-20 55.51 36.70 

21-30 55.52 36.71 

MAY 1-10 63.01 41.66 

11-20 92.09 60.88 

21-31 130.83 95.14 

81

TABLE 7.7 (I) 

1984-1985 



JUNE 1-10 135.95 89.88 

11-20 163.48 108.08 

21-30 146.81 97.06 

JULY 1-10 168.98 111.71 

11-20 169.53 112.08 

21-31 179.22 130.34 

AUGUST 1-10 161.63 106.85 

11-20 162.06 107.14 

21-31 169.66 123.38 

SEPTEMBER 1-10 174.74 115.52 

11-20 166.76 110.24 

21-30 132.28 87.45 

OCTOBER 1-10 111.42 73.66 

11-20 141.33 93.44 

21-31 108.88 79.18 

NOVEMBER 1-10 81.14 53.64 

11-20 70.12 46.36 

21-30 62.32 41.20 

DECEMBER 1-10 39.95 26.41 

11-20 39.31 25.99 

21-31 39.46 28.70 

JANUARY 1-10 39.81 26.32 

11-20 37.81 25.00 

21-31 32.74 23.81 

FEBRUARY 1-10 35.77 23.65 

11-20 32.70 21.62 

21-28 39.58 20.93 

MARCH 1-10 50.28 33.24 

11-20 54.46 36.00 

21-31 50.71 36.88 

APRIL 1-10 61.04 40.35 

11-20 73.66 48.70 

21-30 86.99 57.51 

MAY 1-10 62.60 41.39 

11-20 72.65 48.03 

21-31 101.19 73.59 

82

TABLE 7.7 (J) 

1985-1986 



JUNE 1-10 64.93 42.93 

11-20 81.06 53.59 

21-30 229.69 151.85 

JULY 1-10 181.10 119.73 

11-20 236.32 156.24 

21-31 198.71 144.51 

AUGUST 1-10 160.58 106.16 

11-20 169.39 111.98 

21-31 207.38 150.81 

SEPTEMBER 1-10 84.58 55.92 

11-20 80.80 53.42 

21-30 67.70 44.76 

OCTOBER 1-10 58.20 38.48 

11-20 51.01 33.72 

21-31 42.03 30.57 

NOVEMBER 1-10 34.11 22.55 

11-20 29.65 19.60 

21-30 26.27 17.37 

DECEMBER 1-10 22.37 14.79 

11-20 20.24 13.38 

21-31 18.61 13.53 

JANUARY 1-10 17.65 11.67 

11-20 17.56 11.61 

21-31 16.62 12.08 

FEBRUARY 1-10 16.79 11.10 

11-20 17.28 11.42 

21-28 19.78 10.46 

MARCH 1-10 21.08 13.94 

11-20 22.95 15.17 

21-31 23.56 17.14 

APRIL 1-10 23.17 15.32 

11-20 29.96 19.81 

21-30 33.61 22.22 

MAY 1-10 31.50 20.82 

11-20 33.50 22.15 

21-31 35.30 25.67 

83

TABLE 7.7 (K) 

1986-1987 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 42.91 28.37 

11-20 72.78 48.11 

21-30 107.83 71.29 

JULY 1-10 93.39 61.74 

11-20 116.69 77.15 

21-31 104.96 76.33 

AUGUST 1-10 93.15 61.58 

11-20 80.07 52.94 

21-31 88.65 64.47 

SEPTEMBER 1-10 77.83 51.46 

11-20 96.67 63.91 

21-30 78.69 52.02 

OCTOBER 1-10 63.46 41.95 

11-20 47.46 31.37 

21-31 37.06 26.95 

NOVEMBER 1-10 34.07 22.52 

11-20 30.31 20.04 

21-30 26.18 17.31 

DECEMBER 1-10 23.43 15.49 

11-20 21.58 14.27 

21-31 15.91 11.57 

JANUARY 1-10 13.89 9.18 

11-20 13.08 8.65 

21-31 12.26 8.92 

FEBRUARY 1-10 11.63 7.69 

11-20 11.52 7.61 

21-28 12.64 6.68 

MARCH 1-10 11.80 7.80 

11-20 14.00 9.26 

21-31 17.58 11.63 

APRIL 1-10 32.07 21.20 

11-20 22.40 14.81 

21-30 29.61 19.57 

MAY 1-10 33.48 22.13 

11-20 37.23 24.62 

21-31 43.70 31.78 

84

TABLE 7.7 (L) 

1987-1988 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 72.49 47.92 

11-20 105.29 69.61 

21-30 88.36 58.42 

JULY 1-10 101.37 67.02 

11-20 96.91 64.07 

21-31 108.36 78.80 

AUGUST 1-10 102.60 67.83 

11-20 111.95 74.01 

21-31 74.82 54.41 

SEPTEMBER 1-10 134.61 88.99 

11-20 72.01 47.61 

21-30 98.76 65.29 

OCTOBER 1-10 61.32 40.54 

11-20 45.67 30.20 

21-31 39.06 28.40 

NOVEMBER 1-10 31.70 20.95 

11-20 19.34 12.79 

21-30 16.99 11.23 

DECEMBER 1-10 16.02 10.59 

11-20 14.66 9.69 

21-31 13.41 9.75 

JANUARY 1-10 13.08 8.65 

11-20 13.08 8.65 

21-31 12.92 9.40 

FEBRUARY 1-10 12.68 8.38 

11-20 13.28 8.78 

21-29 14.75 8.78 

MARCH 1-10 15.30 10.11 

11-20 22.66 14.98 

21-31 23.30 15.40 

APRIL 1-10 26.64 19.37 

11-20 30.09 19.89 

21-30 34.99 23.13 

MAY 1-10 35.78 23.66 

11-20 53.61 35.44 

21-31 71.04 51.66 

85

TABLE 7.7 (M) 

1988-1989 



JUNE 1-10 57.30 37.88 

11-20 82.91 54.81 

21-30 90.82 60.04 

JULY 1-10 141.13 93.31 

11-20 110.87 73.30 

21-31 122.19 88.86 

AUGUST 1-10 121.26 80.17 

11-20 111.31 73.59 

21-31 168.87 122.81 

SEPTEMBER 1-10 80.62 53.30 

11-20 54.38 35.95 

21-30 60.82 40.21 

OCTOBER 1-10 51.35 33.95 

11-20 34.07 22.52 

21-31 27.41 19.93 

NOVEMBER 1-10 22.60 14.94 

11-20 20.40 13.49 

21-30 19.01 12.57 

DECEMBER 1-10 18.05 11.93 

11-20 17.12 11.32 

21-31 16.20 11.78 

JANUARY 1-10 9.92 6.56 

11-20 9.65 6.38 

21-31 9.56 6.95 

FEBRUARY 1-10 10.64 7.03 

11-20 9.72 6.42 

21-28 10.35 5.47 

MARCH 1-10 11.76 7.77 

11-20 11.99 7.93 

21-31 12.32 8.96 

APRIL 1-10 12.81 8.47 

11-20 15.34 10.14 

21-30 18.39 12.16 

MAY 1-10 32.30 21.36 

11-20 33.36 22.06 

21-31 81.29 59.12 

86

TABLE 7.7(N) 

1989-1990 



JUNE 1-10 72.18 47.72 

11-20 119.57 79.05 

21-30 126.45 83.60 

JULY 1-10 128.75 85.12 

11-20 126.65 83.73 

21-31 117.89 85.73 

AUGUST 1-10 102.30 67.63 

11-20 80.26 53.06 

21-31 78.74 57.26 

SEPTEMBER 1-10 76.32 50.46 

11-20 69.13 45.70 

21-30 68.68 45.41 

OCTOBER 1-10 54.25 35.87 

11-20 46.17 30.52 

21-31 37.55 27.31 

NOVEMBER 1-10 23.36 15.44 

11-20 18.96 12.53 

21-30 17.24 11.40 

DECEMBER 1-10 15.04 9.94 

11-20 13.04 8.62 

21-31 11.42 8.31 

JANUARY 1-10 10.41 6.88 

11-20 9.65 6.38 

21-31 8.74 6.36 

FEBRUARY 1-10 8.60 5.68 

11-20 8.08 5.34 

21-28 7.80 4.13 

MARCH 1-10 7.13 4.71 

11-20 5.82 3.85 

21-31 5.92 4.31 

APRIL 1-10 6.12 4.05 

11-20 10.11 6.68 

21-30 12.52 8.28 

MAY 1-10 18.48 12.22 

11-20 32.57 21.53 

21-31 37.46 27.24 

87

TABLE 7.7(O) 

1990-1991 



JUNE 1-10 79.11 52.30 

11-20 77.28 51.09 

21-30 90.37 59.74 

JULY 1-10 99.60 65.85 

11-20 126.97 83.94 

21-31 108.67 79.03 

AUGUST 1-10 92.56 61.19 

11-20 94.03 62.17 

21-31 83.45 60.68 

SEPTEMBER 1-10 80.08 52.94 

11-20 76.69 50.70 

21-30 53.41 35.31 

OCTOBER 1-10 44.75 29.59 

11-20 45.59 30.14 

21-31 37.50 27.27 

NOVEMBER 1-10 22.95 15.18 

11-20 17.15 11.34 

21-30 14.32 9.47 

DECEMBER 1-10 13.12 8.67 

11-20 10.82 7.15 

21-31 9.33 6.79 

JANUARY 1-10 9.45 6.25 

11-20 9.27 6.13 

21-31 9.17 6.67 

FEBRUARY 1-10 8.89 5.87 

11-20 8.45 5.58 

21-28 8.54 4.51 

MARCH 1-10 9.11 6.02 

11-20 10.39 6.87 

21-31 10.95 7.97 

APRIL 1-10 28.74 19.00 

11-20 16.39 10.83 

21-30 17.34 11.47 

MAY 1-10 29.11 19.25 

11-20 35.47 23.45 

21-31 39.24 28.54 

88

TABLE 7.7 (P) 

1991-1992 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 42.00 27.77 

11-20 66.32 43.84 

21-30 60.99 40.32 

JULY 1-10 69.65 46.05 

11-20 67.86 44.86 

21-31 73.96 53.79 

AUGUST 1-10 84.81 56.07 

11-20 97.71 64.60 

21-31 80.74 58.72 

SEPTEMBER 1-10 81.34 53.77 

11-20 85.93 56.81 

21-30 66.56 44.01 

OCTOBER 1-10 53.14 35.13 

11-20 42.14 27.86 

21-31 34.58 25.15 

NOVEMBER 1-10 28.66 18.95 

11-20 25.34 16.75 

21-30 19.33 12.78 

DECEMBER 1-10 16.25 10.74 

11-20 12.46 8.24 

21-31 10.96 7.97 

JANUARY 1-10 9.98 6.60 

11-20 8.28 5.48 

21-31 8.46 6.15 

FEBRUARY 1-10 8.94 5.91 

11-20 8.62 5.70 

21-29 8.27 4.92 

MARCH 1-10 8.86 5.86 

11-20 8.92 5.90 

21-31 9.17 6.67 

APRIL 1-10 10.83 7.16 

11-20 15.22 10.06 

21-30 13.91 9.20 

MAY 1-10 13.64 9.02 

11-20 15.88 10.50 

21-31 15.96 11.61 

89

TABLE 7.7 (Q) 

1992-1993 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 17.63 11.65 

11-20 25.13 16.62 

21-30 48.70 32.20 

JULY 1-10 41.84 27.66 

11-20 42.34 27.99 

21-31 48.10 34.98 

AUGUST 1-10 52.64 34.80 

11-20 52.85 34.94 

21-31 57.46 41.79 

SEPTEMBER 1-10 50.40 33.32 

11-20 49.61 32.80 

21-30 41.06 27.15 

OCTOBER 1-10 31.01 20.50 

11-20 22.24 14.71 

21-31 18.93 13.76 

NOVEMBER 1-10 13.98 9.24 

11-20 12.42 8.21 

21-30 11.32 7.48 

DECEMBER 1-10 11.19 7.40 

11-20 9.69 6.41 

21-31 8.95 6.51 

JANUARY 1-10 9.10 6.01 

11-20 9.19 6.07 

21-31 8.62 6.27 

FEBRUARY 1-10 8.34 5.52 

11-20 8.86 5.86 

21-28 8.56 4.53 

MARCH 1-10 13.99 9.25 

11-20 13.96 9.23 

21-31 14.62 10.63 

APRIL 1-10 14.84 9.81 

11-20 16.23 10.73 

21-30 19.43 12.85 

MAY 1-10 24.66 16.30 

11-20 22.20 14.68 

21-31 22.48 16.35 

90

TABLE 7.7 (R) 

1993-1994 

PERIOD FLOW 

UNRESTRICTED 

ENERGY 


JUNE 1-10 28.86 19.08 

11-20 36.87 24.37 

21-30 47.43 31.36 

JULY 1-10 99.34 65.67 

11-20 99.34 65.67 

21-31 116.49 84.72 

AUGUST 1-10 130.65 86.38 

11-20 123.86 81.89 

21-31 118.63 86.27 

SEPTEMBER 1-10 124.81 82.51 

11-20 105.12 69.50 

21-30 99.39 65.71 

OCTOBER 1-10 88.33 58.39 

11-20 65.54 43.33 

21-31 56.17 40.85 

NOVEMBER 1-10 46.60 30.81 

11-20 41.08 27.16 

21-30 37.66 24.90 

DECEMBER 1-10 36.75 24.29 

11-20 33.77 22.32 

21-31 27.74 20.18 

JANUARY 1-10 26.13 17.28 

11-20 24.34 16.09 

21-31 24.58 17.88 

FEBRUARY 1-10 24.25 16.03 

11-20 23.19 15.33 

21-28 24.87 13.15 

MARCH 1-10 22.90 15.14 

11-20 20.67 13.66 

21-31 26.14 19.01 

APRIL 1-10 25.39 16.78 

11-20 31.76 21.00 

21-30 29.14 19.27 

MAY 1-10 32.66 21.59 

11-20 33.67 22.26 

21-31 41.41 30.11 

91

TABLE 7.7 (S) 

1994-1995 

PERIOD FLOW 

UNRISTRICTED 

ENERGY 


JUNE 1-10 59.78 39.52 

11-20 79.15 52.32 

21-30 91.87 60.74 

JULY 1-10 78.56 51.94 

11-20 83.30 55.07 

21-31 84.89 61.73 

AUGUST 1-10 78.02 51.58 

11-20 76.20 50.38 

21-31 81.95 59.59 

SEPTEMBER 1-10 69.52 45.96 

11-20 69.62 46.02 

21-30 60.15 39.77 

OCTOBER 1-10 47.05 31.10 

11-20 41.83 27.65 

21-31 38.30 27.85 

NOVEMBER 1-10 31.52 20.84 

11-20 25.98 17.18 

21-30 21.71 14.36 

DECEMBER 1-10 20.95 13.85 

11-20 19.16 12.66 

21-31 18.12 13.18 

JANUARY 1-10 17.17 11.35 

11-20 17.36 11.48 

21-31 17.15 12.47 

FEBRUARY 1-10 17.01 11.24 

11-20 16.95 11.21 

21-28 17.04 11.27 

MARCH 1-10 15.49 10.24 

11-20 14.69 9.71 

21-31 20.24 14.72 

APRIL 1-10 19.79 13.08 

11-20 24.52 16.21 

21-30 35.79 23.66 

MAY 1-10 52.20 34.51 

11-20 80.59 53.28 

21-31 77.87 56.63 

92

TABLE 7.7 (T) 

1995-1996 

PERIOD FLOW 

UNRISTRICTE 

D ENERGY 


JUNE 1-10 90.43 59.78 

11-20 96.71 63.94 

21-30 97.96 64.77 

JULY 1-10 124.33 82.20 

11-20 104.29 68.95 

21-31 80.17 58.30 

AUGUST 1-10 87.59 57.90 

11-20 88.37 58.43 

21-31 78.51 57.09 

SEPTEMBER 1-10 70.83 46.83 

11-20 63.43 41.93 

21-30 61.02 40.34 

OCTOBER 1-10 45.07 29.80 

11-20 43.88 29.01 

21-31 34.28 24.93 

NOVEMBER 1-10 22.29 14.74 

11-20 25.46 16.83 

21-30 25.60 16.92 

DECEMBER 1-10 19.16 12.67 

11-20 17.06 11.28 

21-31 15.84 11.52 

JANUARY 1-10 13.65 9.02 

11-20 13.57 8.97 

21-31 14.34 10.43 

FEBRUARY 1-10 14.85 9.82 

11-20 13.23 8.74 

21-29 14.48 8.62 

MARCH 1-10 14.70 9.72 

11-20 17.02 11.25 

21-31 18.14 13.19 

APRIL 1-10 16.69 11.04 

11-20 16.21 10.71 

21-30 36.06 23.84 

MAY 1-10 43.95 29.06 

11-20 38.53 25.48 

21-31 53.33 38.78 

93

TABLE 7.7 (U) 

1996-1997 



JUNE 1-10 50.02 33.07 

11-20 42.35 28.00 

21-30 75.64 50.01 

JULY 1-10 84.05 55.57 

11-20 90.50 59.83 

21-31 80.56 58.58 

AUGUST 1-10 77.01 50.91 

11-20 71.81 47.48 

21-31 72.38 52.64 

SEPTEMBER 1-10 72.26 47.77 

11-20 68.95 45.58 

21-30 59.97 39.64 

OCTOBER 1-10 52.72 34.85 

11-20 48.32 31.94 

21-31 43.19 31.41 

NOVEMBER 1-10 39.29 25.98 

11-20 36.53 24.15 

21-30 32.49 21.48 

DECEMBER 1-10 22.37 14.79 

11-20 20.24 13.38 

21-31 18.61 13.53 

JANUARY 1-10 21.05 13.92 

11-20 20.03 13.24 

21-31 20.36 14.81 

FEBRUARY 1-10 20.32 13.43 

11-20 20.25 13.39 

21-28 20.01 10.59 

MARCH 1-10 20.49 13.55 

11-20 21.50 14.22 

21-31 23.45 17.06 

APRIL 1-10 22.50 14.88 

11-20 22.37 14.79 

21-30 23.03 15.22 

MAY 1-10 26.86 17.76 

11-20 30.89 20.42 

21-31 31.91 23.21 

94

CHAPTER – VIII 

POWER EVACUATION 

95 



8.1 GENERAL 

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 Panan 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 Panan Hydro Electric Project can be done through one 220 kV double circuit 

line to be connected at the pooling point which has been assumed to come up about 2km 

from Teesta III H.E.Project. The length of this 220 kV double circuit line would be 

approximately 5km.

CHAPTER-IX 

ENVIRONMENTAL ASPECTS 

96 




9.1.1 General 

Sikkim has immense potential of hydropower generation from the abundance of snow 

and monsoon fed rivers. The proposed Panan hydroelectric project envisages construction 

of a 55 m high concrete gravity dam (above the deepest foundation level) with a central 

spillway on river Talung chu/ Rangyong, 1 km u/s of village Lingza in the North Sikkim 

district (Fig. 9.1). The water will be conveyed to the underground powerhouse on the 

right bank approximately 100 m u/s of confluence of Tolung and Rahi chu through a 8.5 

km long tunnel and the tailrace will be at riverbed elevation of +770 m which would 

utilise a net head of 312 m. The firm power generation will be about 28 MW and would 

have an optimum power generation capacity of about 200 MW. 

9.1.2 Location 

Sikkim is a small hilly State in the Eastern Himalayas, extending approximately 114 kms 

from north to south and 64 kms 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 or plains. The 

elevations range from 300 to 8476 m above mean sea level consisting of lower, middle 

and higher hills, alpine zones and snow bound land. The project would involve 

construction of a diversion structure on river Talung chu/ Rangyong, 1 km u/s of village 

Lingza in the North Sikkim district. North Sikkim, with its Headquarters at Mangan, 

comprises of the valleys of Lachen, Lachung, Dzongu and Tholung. Each of these is 

formed by fast flowing glacier fed rivers originating from The Great Himalayan range 

and its offshoots. The nearest railhead is New Jalpaiguri whereas the nearest airport is at 

Bagdogra.

97 



9.2 PHYSICAL ENVIRONMENT 

9.2.1 Climate/Meteorology 

The climate of the State has been roughly divided into tropical, temperate and alpine 

zones. 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 irritatingly 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 every 

where. Though summer is officially from May to October, Sikkim is almost always wet 

due to the heavy monsoons, with rains at times continuing for days on ends. Longest 

recorded nonstop rain is 11 days. September to October is autumn. 

9.2.1.1 Temperature 

The minimum 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 - August and minimum during December - January. Fog is a common 

feature in the entire State from May to September. Biting cold is experienced at high 

altitude places in the winter months and snowfall is also not uncommon during this 

period. 

9.2.1.2 Rainfall 

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 southwest 

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.

98 



9.2.2 Topography 

Sikkim encompasses the Lesser Himalaya, Central Himalaya, and the Tethys Himalaya. 

It is 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 areas is rich 

in humus and organic matter. The water holding capacity in most area is low and has low 

cohesiveness. The soil is mainly coarse to fine loam in texture. Some soil has a gray 

tinge. Depth of soil varies between 100 cm and 200 cm. The humus cover over the soil is 

sufficiently thick while at some places depleted in higher areas.

Table 9.1: Major physiographic units of soil in Sikkim 

99 



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 

3 Valleys (

100 



Geology 

The proposed diversion scheme on Tolung chu is located within a deep gorge in a narrow 

valley of about 25-30 m width. At the proposed axis the river flows easterly. Both the 

banks rise steeply. The right bank slopes are generally laid at about 70° while the left 

bank is laid at about 75° for about 60 m height beyond which a 50-60 m wide terrace has 

been developed for cultivation. Further uphill, the left bank slopes rise at an angle of 

about 60°. Upstream of the axis the river flows in cascades in a steeper gradient. Both 

banks appear to be fairly stable, as no instability has been observed. At the proposed axis 

rocks are exposed along both the banks and the bedrock in the channel portion is 

expected to be under a thin pile of overburden material. The rock types comprises of 

gneiss/ schist. The gneisses are strong to very strong while the schist is moderately 

strong. 

9.2.5 Seismicity 

Sikkim falls in the active part of Himalayan seismic belt. The project area falls in zone – 

IV of the seismic zoning map of India. 

9.2.6 Catchment area 

The total catchment area of the project is 592 km 2 (Fig. 9.1). The entire catchment of 

Tolung is mountainous with rugged terrain. The area is imparted by approximately N-S 

trending steep longitudinal hill ranges and valleys. The tributaries are angular and have 

dendritic drainage patterns. Streams have moderate to steep slopes with falls at a number 

of places. The natural vegetation consists of mixed evergreen to deciduous, conifers to 

almost tundra like vegetation at higher elevations. 

9.2.7 River System 

Tolung is a major tributary of Teesta River and joins Teesta upstream of Mangan near 

Sankalang in the North District of Sikkim. Tolung originates from Talung and

101 



Tongshiong Glaciers as Rukel chu. Rukel chu, Urman chu and Ringpi chu rivulets join to 

form river Tolung (Fig. 9.3). 

Rangyong chu rises as Rukel chu from Tongshi and Talung glacier from the base of South 

Kanchenjunga peak (8,476 m). Along its eastward course, Rukel chu receives drainage 

from Tingchen glacier on its right bank (Fig 9.3). Umram chu is the major tributary of 

Rukel chu originating from Umram glacier. Umram chu is joined by Passaram chu on its 

left bank and then drains into Rukel Chu. Thereafter Rukel chu is known as Rangyong chu. 

Rangyong Chu in certain stretches is also known as Tolung chu. Another tributary Ringpi 

Chu joins Rangyong Chu on its left bank about 1.00 km upstream of the proposed dam site. 

The catchment area of Panan H.E. Scheme up to the proposed dam site is 678.35 sq km. 

Total length of Rangyong Chhu from its origin up to dam site is about 25 km. 

9.2.8 Landuse Pattern 

The landuse / land cover pattern within the 7 km radius of the proposed Panan 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 

Pan Scenes of area covering 7 km radius of the project site are given in Figures 9.4 & 9.5. 

The 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 /land cover 

categories is given in Table 9.2 and the percent representation of each of the landuse / 

landcover type is shown in Figure 9.7. From the data it is clear that Dense Mixed 

Broadleaf Forests constitute more than half (55%) of the total land area, therefore form 

the predominant landuse in the vicinity of the proposed project site. The degradational 

type of forests, namely open and degraded, constitutes 12% and 14%, respectively of the 

land area covering about 6300 ha of land. It is evident from the results that the area does 

not significantly disturb ecosystems, as the area under human intervention around the 

project vicinity comprises only 7% of the land area. A sizeable portion of the area is 

under rocky land and cliffs comprising about 7% of land area. Primary analysis of the

102 



landuse / landcover indicates that the area is under natural ecosystem with only limited 

human intervention. Presence of modified or managed landscapes is limited and majority 

of the area is under natural ecosystems. Natural landscape features also include areas 

under snow and water bodies, which constitute 3% and 20% of the land area, 

respectively. The dense forests in the catchment are present towards northeast, east, 

northwest and southwest. These forests are represented by Tolung Reserve Forest in the 

north and north-east, Sakyong Reserve Forest in the west and southwest and Lingdem 

Reserve Forest in the south and south-east. These forests are mostly broad-leaf forests 

with occasional representation of bamboo in them, particularly in the warmer areas. 

Table 9.2 Area (ha) under different landuse/landcover categories in 7 km 

radius of Panan H.E. Scheme 

Landuse/landcover Area (ha) 

Barren land/Cultivation/Settlements 1822.65 

Degraded Forest 3290.41 

Open Forest 3001.37 

Rocky land 1781.75 

Dense Mixed Forest 13202.12 

Damp Areas/Water bodies 603.76 

Snow 609.08

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Figure 9.7 Percent area under various landuse/landcover categories in 7 km 

radius of the proposed Panan H.E. Scheme. 

14% 

12% 

9.2.9 Submergence 

The project is likely to inundate a total area of 15.6 ha of land, which is very small and is 

confined to the river valley. The FRL is at an elevation of 1095 m and the MDDL is at 

EL 1085 m. The spread of reservoir is shown in Figure 9.8. The predominant landuse in 

the submergence area is degraded and open forest and does not involve inundation of any 

village or human habitation. 

7% 

55% 

Dense Forest Degraded Forest Open Forest 

Barren /Cultivation/Settlements 

Snow 

Rockyland Water/Damp Areas 

7% 

2% 

3%

9.2.10 Infrastructure 

The existing facilities in the project area are as follows: 

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Road communication Network 

The project area falls in the North District of Sikkim and mainly single lane road exists in 

the area. Roads are impaired at a number of places by landslides and sinking zones. The 

Government of Sikkim has taken up road widening works at a number of places. The 

roads are maintained by DGBR organization and State PWD. 

Bank 

There exists branches of SBI at Mangan, Chungthang and Tolung . 

Post office 

One Post office branch exists at Mangan. 

Educational Facilities 

Higher Secondary school exists at Tingbong. Primary schools are situated at a number of 

places in the vicinity of the project as Namprick Primary School. Tingbong Community 

Information Centre (CIC) North Sikkim Upper Dzongu is there to provide education in 

information technology to the students of the school. For higher education, students go to 

Gangtok at Sikkim Govt. College, Tadong, Gangtok, Manipal Institute of Technology 

Sikkim and Sikkim Manipal University of Health Technology & Medical Sciences. 

Communication 

The communication network is poor. However, there is one telephone exchange at 

Mangan. Tingbong Community Information Centre (CIC) at North Sikkim, Upper 

Dzongu and another one at Mangan, provide internet facilities to the locals. 

Government Department 

Government department offices exist at block level in the project area. There is a District 

centre at Mangan.

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Hospitals/ Primary Health Centers 

Primary health centres are available at Sankalang. There is a District Hospital at Mangan. 

A new 100 bed Community Health Centre is under construction at Mangan, North 

Sikkim. Central Referral hospital is at Gangtok 

9.3 BIOTIC ENVIRONMENT 

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. Nowhere in the world in such a small area can one find 

flora and fauna of all varieties - Tropical to the Alpines. Sikkim's botanical and 

zoological richness is awe- inspiring, boasting of more than 4500 species of flowering 

plants. 30% of all the birds in the country are 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 4500 

species of flowering plants, 362 species of ferns and its allies, 11species 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 important shrubs are found in low and high 

altitude areas. 

9.3.2 Flora 

The dam site is located in a tropical hilly terrain and the area in the vicinity of the project 

is mainly comprised of dense mixed forests. This area experiences hot and humid 

summers and mild winters. There is an extended spell of warm humid 

climate throughout the year with a short dry spell during winter months starting from 

October to February. Owing to prolonged spell of humidity and moderate temperatures at 

these altitudes the vegetation is constituted mostly by tropical moist deciduous and

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evergreen plant species. These areas are densely vegetated by all the physiognomic forms 

– trees, shrubs and herbaceous flora. At warmer altitudes Duabanga sonnertoides and 

other woody elements like Aglaia lawii, Bombax ceiba, Chukrasia tabularis, Eugenia 

kurzii, and Mangifera sylvatica can be seen. In the catchment broad-leaved species are 

represented by Castanopsis indica, Eurya cerasifolia, Gynocardia odorata and 

Macaranga. The vegetation in the sub-tropical zone is comprised of elements like Adina 

cordifolia, Bischofia javanica, Michelia velutina, etc. At higher reaches, the species like 

Magnolia hodsonii and Helicia sp. are encountered. Schima wallichi is an important 

constituent of the vegetation of this area. At many places the mixed forests is replaced by 

pure bamboo formations of Dendrocalamus strictus (Ringal) on the slopes. Wherever 

bamboo is absent the natural formations have profuse growth of ground and shrubby 

flora. The shrubs are represented by Buddleja asiatica, Clerodendrum japonicum, C. 

viscosum and Embelica floribunda. The undershrubs and ground flora comprises Barleria 

cristata, B. strigosa, Justicia procumbens, Pavetta indica and Vitex negundo. Some of the 

important and commonly occurring lianas and climbers besides Bauhinia vahlii are the 

species of Piper, Cissus and Cryptolepis. In areas where first storey tree cover is sparse 

and gaps are huge, Cyathea spinulosa, the tree fern is met with frequently among the 

shrubs and undershrubs. Majority of area is under dense broad leaf mixed forests and 

human intervention is limited to the area surrounding villages like Sakkyong, Phantong, 

Myong, Lingzah, Laven, Lingdem and Nung. 

9.3.3 Faunal and Wildlife 

As the project site falls in the vicinity of dense forests a good presence of wildlife is 

expected in and around the project site. The upper part of catchments of Ringpi Chhu and 

Tolung Chhu and Rangyong Chhu harbour several faunal species like Hoary-bellied 

squirrel (Callossciurus pygerithrus), Orange-bellied squirrel (Dremomys lokhriah), 

Assamese macaque (Macaca assamensis), Himalayan palm civet (Paguma larvata), 

Stone marten (Martes foina) and jackals (Canis aureus). These animals are generally 

found in the vicinity of agricultural crops. They raid the crops of large cardamom during

107 



the fruiting season. In addition there are also species like Civets (Viverra zibetha), 

porcupines (Hystrix brachyura), Grey musk shrew (Suncus murinus), the house mouse 

(Mus musculus) and Bandicoot rat (Bandicota bengalensis). The upper reaches i.e. the 

alpine areas of the catchment harbour other mammalian species, which include Nayan, 

Bharal, Snow leopard, bear, Himalayan tahr, Barking Deer, Himalayan marmot and 

pikas. These animals, however seldom come down below altitudes of 2,100 m. The 

avifauna is comprised of bulbuls, thrushes, eagles, partridges, pigeons, doves, koels, 

owls, kingfishers, nightjars, woodpeckers, orioles, drongos, mynas, flycatchers, babblers, 

robins, etc. Among the reptiles Python molurus, Naja naja and Dendrelaphis sp. are 

important species found in the catchment. Among the invertebrates many species of 

butterflies and dragonflies are found abundantly in the area. 

Among the various faunal species present in the catchment area Panthera 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 

Ichthyofauna of the river in lower reaches is comprised mainly of Balm, Asala, Chepti, 

Gadela, etc. and snow trout and minor trouts are also found at higher elevations. Some of 

the identified fish species found in the area are Schizothorax richardsonii, Schizothorax 

progastis, Barilius bendelisis, Acrossocheilus hexagonolepis, Tor putitora, Garra gotylo 

gotylo, Bagarius bagarius, Glyptothorax cavia, Channa orientalis, etc. 

9.4 EXISTENCE OF ANY PROTECTED AREA/ARCHAEOLOGICAL SITES 

There is no protected area in the form of Wildlife Sanctuary or National Park within 7 km 

radius of the proposed project. In addition to this, there are no sites or monuments of 

archaeological or national importance, which would be affected by the project activities 

directly or indirectly.

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9.5 SOCIO-ECONOMIC ENVIRONMENT 

The area in the vicinity of the project is very thinly populated. The human settlements are 

scattered and the human population as per the 1991 census up to different aerial distances 

from the project are given below. 

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

Population 328 565 2773 

Households 69 125 535 

Most of the land required for the project area lies in the North district of Sikkim. The land 

requirement for the project may include private land, marginal forestland and village 

forests. Most of the population in the project area comprises of Lepchas, Bhutias and 

Nepalese which constitute about 85% of the population. Most of the people are tribals 

with little agricultural earnings being farmers with meager land holdings. Cardamom and 

ginger is grown at a number of places on private as well as forestlands. The families in 

general have a few cattle, sheep and pigs with some poultry. Most parts of the valley are 

inhabited with minuscule population. Yaks herds, herdsmen and sheep grazers are seen 

in to migrate in the catchment area. 

The existing public facilities in the project area are not sufficient. There are very low 

opportunities of employment in the local area. People are involved in small roadside 

business as kiosks selling tea, snacks, eggs, vegetables, etc. grown in the fields. The 

overall economic conditions are not very healthy. Jhoras (small streams) are main source 

of drinking water in the area. Most of the houses of the locals are kuccha. However, the 

Government is constructing pucca model houses in a number of villages.

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9.6 PREDICTION OF ENVIRONMENTAL IMPACTS 

9.6.1 Impacts on Land Environment 

Sufficient land would be required for construction of the proposed dam, powerhouse, 

colonies & approach roads etc. Some portion of the land would also come under 

submergence. All these activities would mean some disturbance and change in the 

landscape/landuse pattern of the area. 

9.6.2 Impacts on Water Environment 

During the construction phase there may be some instances of excavated and quarried 

material getting washed away along with the rain water that may cause turbidity or 

sedimentation downstream. Natural sedimentation emanating from severely degraded 

catchment area is one of the important issues to be addressed. Also the problems of 

waste disposal and management (human excreta and domestic sewage) due to 

congregation of large population of migrant labourers may be encountered. Proper waste 

management measures are required to be implemented during the construction phase of 

the project so as to protect water body from pollution. 

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, some land will be inundated. The direct impact of 

construction activity of a water resources project in a hilly terrain is generally limited to 

the vicinity of the construction sites. A large number of labourers and technical staff and 

other groups of people are likely to aggregate in the area during construction phase. In 

this area majority of rural community depends on forest for food, fodder and timber.

110 



Submergence of forest area in primary impact zone may reduce the availability of 

resources for the local people. This would also result in significant changes at the 

structural resource level in forest. The acquisition of land for various project activities 

would also lead to cutting of vegetation on these lands. 

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. The operation of various construction equipments is likely to generate 

significant noise. Likewise blasting too is likely to generate noise level and vibration 

intermittently. The noise may scare the fauna in the region and force them to migrate to 

other areas. There might also be some impacts due to increased human interference. 

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 fluctuation of 8-10 m in the 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 birds, especially 

water birds. However because of the presence of a good habitat it is quite likely that 

water birds will flock in this area in a large number. The birds from cold climatic areas 

could also use this area during the winter season. 

9.6.4.4 Impacts on aquatic ecology: 

The major physical change upstream of the proposed dam will be formation of a 

lacustrine habitat from a riverine habitat. Whereas below the damsite, there will be 

regulated water or very little water in river course. As such there will be some changes in 

the aquatic environment in this stretch. There is a possibility of stratification in the 

reservoir during winter. For this the water quality analysis shall be conducted regularly. 

Moreover, some migratory fish species may get affected due to construction of the dam.

111 



Also fish species which are riverine and are not accustomed to deep lake environment 

may also get replaced. 

9.6.5 Impacts on Socio-Economic Environment 

Since the submergence area is small and is confined to the river valley, no village is 

expected to 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 a project of this magnitude and most of the labourers 

employed in the project will be from the local population. 

As a part of the Environmental Impact Assessment Study, a detailed socioeconomic 

survey would 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.

112 



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 

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 

120 



10.1 EXISTING ACCESS AND INFRASTRUCTURE FACILITIES 

10.1.1 Road Communication 

The Powerhouse is located on the right bank of Ranyong Chu u/s of confluence of 

Tolung Chu and Rahi Chu near the village Panan. The Powerhouse is about 9.0 Km from 

Mangan and 7.5 Km from Singtam - Mangan state highway which runs along the left 

bank of river Teesta. The power house is about 1.5 Km from CWC gauge and discharge 

site at Sanklan, about 600m u/s of the power house of Teesta (III) H.E. Project and about 

1300 m u/s of the dam of Teesta (IV) H.E. Project. The Power house site is well 

connected by road from Mangan, Singtam (NH31A) and Gangtok. 

The dam site is located near the village Lingza. The Lingza is 17 Km from Mangan, the 

head quarter of North Sikkim District 0f Sikkim, 62 Km from Singtam (NH31A), 152 

Km from NJP railway station and 167 Km from Bagdogra airport. The Lingza village is 

well connected form Mangan by a PWD road. . The Siliguri-Gangtok (NH-31A) and 

Singtam-Mangan-Sanklan state highways are being maintained by BRO while the 

Lingza-Sanklan-Rungto-Laven roads are being maintained by state PWD. 

10.1.2 Housing And Community Facilities 

Panan is the small village near to power house with basic facilities of health care, 

schooling, market, postal and telephone. These facilities are catering the need of very 

small population and would be totally inadequate for the project personals. It is therefore 

necessary to plan housing, office, recreation, store etc. for meeting the requirement of the 

project.

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10.1.3 Power Availability 

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 95 MW. 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 project area. Therefore , the necessary construction power 

shall be available from Phodong Sub-Station for the execution of Panan H.E. Project. 

10.2 PROPOSED ACCESS AND INFRASTRUCTURE FACILITIES 

Keeping in view the available infrastructure facilities of communication,, housing and 

power, the requirement of the same for Panan H.E. Project has been worked out. 

10.2.1 Improvement Of Existing Road And Bridges 

The Powerhouse is located near the confluence of Tolung Chu and Rahi Chu near the 

village Panan . The state highway having a length of 11km from Sanklan connects the 

power house and dam sites. The Sanklan-Lingza-Rungto-Laven PWD roads connecting 

damsite , adit I&II are required to be improved for a length of about 8.5 Km by 

widening. There are 2 bridges from Sanklan to Lingza, one across the river Rangyong 

about 120m long and another 30m long on the road to Lingza are required to be upgraded 

to suitable classes. The bridges from Tolung chu to the power house of Teesta (III) 

H.E.Project have not been considered as these should form the cost of Teesta (III) 

H.E.Project . The Dam of Teesta (V) HE Project under execution is located about 18 Km 

downstream of Sanklan, therefore, all the bridges are being upgraded to class 30R unto

122 



Dam site and class 70R unto Powerhouse at Dipudara. Therefore, no more bridges are 

required to be upgraded. 

10.2.2 Construction Of Roads & Bridges 

The dam site shall be accessed from Mangan - Lingza road from left bank for which a 

new project road of 3.0 Km is to be constructed alongwith a bridge at dam site across the 

river. The adit-I, II &III & surge shaft shall be approached from right bank PWD road. 

Two townships have been proposed one at Lingza and another at Sanklan. 

10.2.3 Accommodation For Residential Purpose 

To accommodate the project employees and contractors, land would be required for 

construction of suitable residential complexes. The residential colony and office 

complexes will be located near Lingza and Sanklan villages where suitable land is 

available. The 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 as . 100. 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 40% of the buildings as the permanent and the remaining as temporary. This 

conclusion has been drawn on the basis that 40% of the staff strength would be required 

for maintenance and operation after the completion of the project. 

Requirement of built up accommodation has been worked out and it is estimated that 

about 2484 Sq.m of permanent built up area and 4675 Sq.m of temporary builtup area 

would be required. Total plinth area for residential accommodation worked out to be 

7159 Sq.m,

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10.2.4 Accommodation For Non-Residential Purposes 

The office complexes are proposed at Lingza and Sanklan. Workshops, laboratories, 

stores, water supply, fire stations, electrical substations etc would be accommodated in 

the project area near Sanklan. One small –store – cum –stockyard is proposed at railhead 

near new Jalpaiguri Railway station where construction materials like cement, steel and 

machinery and equipments would be store for further transportation to the project site, 

Batching and mixing plants are to be commissioned, one near dam site and the other near 

power house site. 

Accommodation required for non residential purposes have been worked out to be 2220 

Sq.m of which about 40% 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 

A 11KV line from 2.5 MVA, 66/11KV Sub-station at Phodong have been considered to 

meet the construction power requirements for the execution of Panan H.E. Project. A 10 

to 15 km long 11KV transmission line shall be constructed from Phodong/ Mangan 

substations to Panan H.E. Project.

CHAPTER –XI 

CONSTRUCTION PLANNING & SCHEDULE 

124 




The equipment planning & construction methodology of Panan H.E. Project in Teesta 

Basin has been developed on following considerations. 

1. The project construction period has been considered as five years. 

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 (from May to September) rainy season has been considered while 

planning surface works. The progress will slow down during rainy season. 

11.2 CONSTRUCTION METHODOLOGY 

11.2.1 Infrastructure Works 

The main infrastructure development is proposed to be carried out in a period of 12 

months. During infrastructure period Land Acquisition, construction of approach roads, 

bridges & culverts, arrangement of construction power will be undertaken. 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, Motor Grader, Air 

compressor, Road Roller etc. are proposed for deployment during infrastructure stage. 

11.2.2 Diversion of River 

The excavation of 6.5m finished diameter, Horse shoe shaped 600m long diversion tunnel 

would be carried out by full face drilling & blasting method from 7 th month. Excavation 

of Diversion Tunnel will be carried out with 2 Boom drill jumbo, Air Track/ Wagon Drill 

2.5cum side dump loader, L.P. Dumpers etc.. Diversion tunnel excavation & concreting

125 



would be completed in 12 months. The concreting equipment proposed are 30 cum/hr 

Batching & Mixing plant, Concrete pump, Transit mixer, shotcrete m/c, Grout pump and 

shutters. U/s & D/s Coffer dam would be constructed immediately after construction of 

diversion tunnel within a period of 4 months to divert the river . 

11.2.3 Concrete Dam 

After construction of coffer dam and river diversion, the excavation of river bed will be 

taken up. The excavation of Dam & foundation treatment would be carried out in 5 

months. Excavated material will be handled by 1.0 cum Hyd. Excavator and 20/ 25t 

dumpers. Concreting of Dam & HM work would be carried out in further 26 months. 

Concreting would be done by 2 Nos. traveling tower crane (4.5 t at 30 m radius) with 

2.0/3.0 cum bucket capacity, 30 Cum/hr Batching& Mixing plant installed at Diversion 

Tunnel, another 120 cum/hr. Batching & Mixing Plant at Dam site and 300TPH 

Aggregate Processing plant. Batching & Mixing Plant and Aggregate Processing plant 

would also cater the requirement of Diversion tunnel, Desilting chambers and some 

portion of HRT. 

11.2.4 Intake Structure, Desilting Chamber & Silt Flushing tunnel 

2Nos. dufour type desilting chamber of size 225m length, 15m width & 20m height 

would be excavated in 24 months. For excavation of desilting chamber, the intake 

structure & intake tunnels would be excavated first. The intake tunnels would be 

extended upto the 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 intake 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, loader, excavators, Dumpers, concrete pump, 

transit mixers etc.

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11.2.5 Head Race Tunnel 

Construction of 9.0 km long, 6.0 m finished diameter horse shoe shaped Head Race 

Tunnel is proposed by full face drilling & blasting method. It will be excavated through 3 

nos intermediate adits of 6m dia.. The excavation of adits would be carried out in five 

months. Excavation would be carried out by 2 boom drill jumbo, 2.5Cum Side Dump 

Loader and L.P. Dumpers. Concreting will be carried out by deploying 4 sets of 

concreting equipment i.e. Concrete pump, 4.0cum Transit Mixer etc. 30 cum/hr Batching 

& Mixing Plant & 50 TPH Aggregate processing Plant would be deployed at HRT. The 

excavation, concreting and grouting of HRT will be completed in 41months. 

11.2.6 Surge Shaft 

For Construction of Surge Shaft an adit to surge shaft bottom would be excavated. After 

completion of construction adit, 15m dia., Surge shaft would be taken up from top of 

surge shaft. Excavation of Surge Shaft would involve pilot hole drilling, reaming of pilot 

hole & enlargement of reamed hole. Raise borer, Jack Hammer, L.P. Dumpers etc will 

be deployed for excavation of Surge shaft. Concreting would be completed employing 2 

m shutter. 30 cum/hr. Batching & Mixing Plant would be deployed at surge shaft. 

Construction of surge shaft would be completed in 32 months. 

11.2.7 Pressure Shaft 

3.0 m diameter, two no. pressure shaft will be excavated in the same way as surge shaft 

by deploying Raise borer , 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 month time. 

11.2.8 Power House 

4 X 50 MW (200 MW) underground power house (120 m X 22 m X 45 m size) would be 

excavated in 18 months. For excavation of Power House a Main Access Tunnel would be 

excavated in about 6 months. A branch from this Main Access Tunnel would be extended

127 



upto the crown of power house followed by extension of this extended MAT upto 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 adit. From Power House Cavern four shafts of 2.0 m diameter would be 

excavated up to the bottom level of draft tube followed by benching of Power House 

cavern upto the bottom of Power House. Mucking will be carried out through TRT. The 

equipment to be deployed for excavation are jack hammers, wagon drills, air 

compressors, loader, excavators, dumpers, winches etc. Concreting of Powerhouse would 

be carried out with the help of concrete pump, Transit Mixers etc. 60 cum/hr. Batching 

& Mixing Plant 150 TPH aggregate processing Plant would be deployed at Power House 

which would also cater the requirement of Pressure shaft and TRT. Installation & Testing 

of Machine would be undertaken in such a manner that Project get commissioned in 60 th 

month from the start of Project construction. 

11.2.9 Tail Race Tunnel 

500m long horse shoe shaped Tail Race Tunnel having 6.0 m finished diameter will be 

excavated in 7 months. Excavation of Tail Race Tunnel would be carried out by full face 

drilling & blasting method with 2 boom Drill Jumbo, Side dump Loader, 25T L.P. 

Dumper etc. The TRT will be excavated from the start of major work because TRT will 

be used for mucking of power house. After the excavation of power house concreting of 

TRT will be taken up with the help of concrete pump, Transit Mixer, Batching & Mixing 

plant and aggregate processing Plant installed at Dam. 

11.3 CONSTRUCTION SCHEDULE 

The construction schedule has been drawn up for the actual construction phase, wherein a 

total period of five years has been assumed for construction. Main considerations/ 

assumptions while framing the construction schedule are as under:

128 



i) Since the date of CCEA clearance cannot be anticipated at this stage, the time 

assumed for various activities is inclusive of the effect of monsoon. 

ii) The major contracts will be awarded within three months of CCEA clearance 

and within another three months, the agencies will mobilize to start work at 

site. 

iii) The 600m Diversion Tunnel (including HM work) will be done within next 14 

months. Since the lean discharge is less, cofferdam building (initial stage) and 

river diversion will be possible in another one month, i.e., by 21st month. 

iv) A total period of 31 months has been allowed for complete concreting and 

HM works of concrete dam including 5 months for foundation work apart 

from 2 months for reservoir filling. 

v) The Head Race Tunnel of about 9 km. length will be executed mainly from 6 

faces through three adits, in a total period of 50 months including adits 

plugging, charging of HRT Tunnel construction of adits. 

vi) Surge shaft, Pressure shaft and Penstocks works will be taken up concurrently 

and independently. 

vii) Power House and Transformer Caverns will be excavated in 18 months in all. 

However after about 12 months’ work concreting should start and EOT level 

will be achieved in Service Bay portion by 27 th month. The EOT crane should 

be made available for use from 30 th month. 

viii) The E&M works upto commissioning of all three units will be done in 35 

months time, of which 31 months will be available after commissioning of 

EOT crane. 

ix) Other works like Trail Race Tunnel, Pothead yard, etc. will be executed 

concurrently. 

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.

CHAPTER-XII 

COST ESTIMATE 

131 



12.1 PRELIMINARY COST ESTIMATE FOR CIVIL, HYDRO- 

MECHANICAL, ELECTRO-MECHANICAL WORKS: - 

The estimate has been prepared to arrive at the Capital Cost of Panan 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: - 

12.1.1 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 River Diversion Work , Coffer dam, Concrete Dam and Spillway 

along with associated Hydro-mechanical equipment. 

J-POWER PLANT CIVIL WORKS 

This covers the cost of project components viz. Intake Structure,Desilting Chamber, 

Headrace Tunnel and TRT, Surge Shaft, Pressure Shaft, Power House and Transformer

132 



Cavern and other Appurtenant Works along with associated Hydro-mechanical 

equipment. 

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.

133 



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.

134 



12.3 III-TOOLS AND PLANTS 

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. Also the recoveries on account of 

resale of DG sets, Transformer etc and resale of temporary buildings have also been 

envisaged. 

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.

135 



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 4.54 

B - Land 11.00 

C - Works 95.41 

J - Power Plant Civil Works 331.37 

K - Buildings 12.92 

O - Miscellaneous 10.94 

P - Maintenance 4.61 

Q-Special Tools & Plants 3.98 

R - Communication 20.94 

X - Environment & Ecology 10.14 

Y - Losses on Stock 1.15 

Total of I-Works 506.99 

II - Establishment @ 8% of cost of I-Works less B- 39.68 

III - Tools and Plants @ 1% of cost of I-Works 5.07 

IV - Suspense 0.00 

V - Receipt & Recoveries (-) -2.82 

Total Direct Charges 548.92 

2. INDIRECT CHARGES 

a) Capitalised Value of Abatement of Land Revenue 0.11 

b) Audit and Account Charges @1% of cost of I- 5.07 

Total Indirect Charges 5.18 

Total Of Direct & Indirect Charges 554.10 

ABSTRACT : 

A Civil Works 554.10 

B Electrical Works 209.17 

C Transmission Works 1.67 

Total Cost 764.94 

C IDC 81.14 

D Total Cost With IDC 846.08

S. 

No. 

A- PRELIMINARY 

Description of Work Qty Unit 

136 



Rs in Lakhs 

Rate Amount 

1.0 Prefeasibility 

1.1 Preparation of Prefeasibility Report LS 14.00 

2.0 Preparation of Detailed Project 

Report 

2.1 Detail survey for final location of project 

components 

LS 25.00 

2.2 Aerial survey, contour survey for 

reservoir basin including establishment of 

permanent benchmarks. 

LS 10.00 

2.3 Geological and geophysical surveys and 

investigation 

I) Drifting 800 m 0.05 40.00 

ii) Geophysical LS 20.00 

iii) Core drilling 300 m 0.10 30.00 

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 8.00 

2.5 Investigations for foundation and rock 

LS 6.00 

testing 

2.6 Investigation for availability of 

construction materials. 

LS 3.50 

2.7 Construction of access roads to facilitate 

investigations 

LS 7.00 

2.8 Model experiment. LS 8.00 

2.9 Computer and telecommunication 

LS 3.00 

facilities. 

2.10 Vehicles for inspecting officers for site 

investigations 

LS 25.00 

2.11 Camping equipment LS 2.00 

2.12 Preliminary soil test, establishing soil 

testing laboratory. 

LS 6.00

137 



2.13 Consultant’s fees including charges for 

preliminary design work or device 

LS 15.00 

2.14 Training of engineers during investigation 

and preparation of project reports 

LS 4.00 

2.15 Ground water studies. LS 6.00 

2.16 Environment and ecological studies. LS 10.00 

2.17 Preparation and printing of DPR LS 10.00 

Sub Total 252.50 

3.0 Pre-Construction Stage Investigations 

3.1 Topographical Surveys LS 15.00 

3.2 Geological Investigation 

I) Diamond Core Drilling 100 m 0.10 10.00 

ii) Exploratory Drift 100 m 0.1 10.00 

iii) Excavation in trenches & pits LS 0.75 

iv) Testing of Samples LS 4.00 

3.3 Hydrological and Silt data collection - 2 

sites for 4 years 

8.00 Year 2.00 16.00 

3.4 Meteorological Data Collection 2 sites for 

4 years 

8.00 Year 0.40 3.20 

3.5 Construction material survey 

I) Topographical Survey 4.00 Hec. 0.05 0.20 

ii) Collection and Transportation of samples LS 3.00 

iii) Laboratory Testing of Samples including 

charges for all T&P and Machineries 

LS 6.00 

3.6 Model studies LS 10.00 

3.7 Seismological data collection for 4 years 4.00 Year 1 4.00 

3.8 Survey for layout of colonies and roads 

I) Residential-cum-Office accommodation 2.00 Hec. 0.5 1.00 

ii) Batching Mixing Plant and Workshop 1.00 Hec. 0.5 0.50 

iii) Project and quarry site road 0.50 Hec. 0.5 0.25 

3.9 Workcharged establishment for 

unforeseen works 

5.00 Year 2 8.00

4.0 Design & Consultancy 

4.1 Cost of Design Establishment including 

procurement of printing stationery and 

preparation of completion report, History 

of Project etc. 

138 



LS 25.00 

4.2 Cost of Special Studies and Designs LS 15.00 

4.3 Fees for Consultant and specialists LS 15.00 

4.4 Training of Engineers LS 5.00 

5.0 Equipment 

5.1 Drawing and Mathematical Instruments LS 10.00 

5.3 Survey Instruments LS 30.00 

5.4 Office instruments LS 10.00 

Grand Total : 454.40

S. 

No. 

B – LAND 

139 



Rs in Lakhs 

Description Qty. Unit Rate Amount 

1. Private Land required 

i Permanent Residential and Non 

Residential Buildings 

6.00 Ha 5.50 33.00 

ii Diversion tunnel 3.00 Ha 5.50 16.50 

iii Submerged in the reservoir area 15.60 Ha 5.50 85.80 

iv Construction of dam/ weir 4.00 Ha 5.50 22.00 

v Construction material 2.00 Ha 5.50 11.00 

vi Approach Roads 40.00 Ha 5.50 220.00 

vii Power house 2.00 Ha 5.50 11.00 

viii Adits 3.00 Ha 5.50 16.50 

ix Switch Yard 1.00 Ha 5.50 5.50 

x Surge Shaft 1.00 Ha 5.50 5.50 

x Land for Misc Purpose 2.40 Ha 5.50 13.20 

Sub total (1) 80.00 440.00 

2, Forest Land 

I River bed 10.00 Ha 0.00 0.00 

ii Underground 5.00 Ha 0.00 0.00 

Sub total (2) 15.00 0.00 

3. Land on lease/ hire for 4 Years 

Dumping area 0.50 Ha 3.00 1.50 

Dumping area for Batching and 

mixing plant 

0.50 Ha 3.00 1.50 

Temporary residential & nonresidential 

buildings 

2.00 Ha 3.00 6.00 

Contractors Colony 2.00 Ha 3.00 6.00 

Construction facilities 2.00 Ha 3.00 6.00 

Railway Siding Facilities 1.00 Ha 3.00 3.00 

Electro - mechanical Contractor 1.00 Ha 3.00 3.00 

Hydro -mechanical works 1.00 Ha 3.00 3.00 

Total (3) 10.00 30.00

4. Other Compensation 

I Cost of crops standing on 

cultivated land required @ 30% of 

cultivated land 

140 



80 Ha 1.65 132.00 

ii Buildings with brick walls and 

GGI sheet roofing 

3.00 Nos 3.00 9.00 

iii Compensation for trees LS 10.00 

Sub total (4) 151.00 

5. Misc. Compensation 

Compensation for relocating 

2.00 

electric and telephone poles 

Crop Compensation for LS 200.00 

submergence 

Total (5) 202.00 

Total (1+2+3+4+5) 823.00 

6. Interest 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 

7. Solatium charges for compulsory 

acquisition of land @ 30% of the 

cost of private land 

8. Provision for legal charges @1% 

on total compensation 

9. Labour and material required for 

measurement and demarcation of 

land and properties @ 1% of land 

acquisition 

10. Establishment charges @6.25% of 

cost of total compensation 

35.46 

177.30 

8.23 

4.70 

51.44 

Total 1100.13

S. 

N. 

ABSTRACT OF COST OF C - WORKS 

Description Amount (Rs. In Lakhs) 

141 



civil HM total 

1. Diversion Tunnel 930.50 94.50 1025.00 

2. Coffer Dam 447.39 447.39 

3 Concrete Dam 2021.83 118.13 2139.96 

4 Spillway 5060.88 680.40 5741.28 

Total 8460.60 893.03 9353.62 

Add For Works Tax @ 2% 169.21 17.86 187.07 

Grand Total 8629.81 910.89 9540.70

S. 

No. 

DIVERSION TUNNEL 

Description Unit Qty. Rate 

(Rs.) 

142 



Amount 

( Rs. in 

Lakhs) 

1.0 Surface Excavation 

1.1 Common excavation Cum 15,000 125 18.75 

1.2 Rock excavation Cum 4,000 300 12.00 

2.0 Underground excavation Cum 25,000 1000 250.00 

3.0 Rock Support System 

3.1 Rock bolts M 14,000 400 56.00 

3.2 Steel Supports MT 100 42000 42.00 

3.3 Shotcreting Cum 1,000 4000 40.00 

3.4 Concrete lagging Cum 200 7000 14.00 

4.0 Concrete 

4.1 Concrete lining M-20 Cum 4,000 4000 160.00 

4.2 M-15 Cum 2,200 2930 64.46 

4.4 M-25 Cum 2,500 3610 90.25 

5.0 Reinforcement MT 200 27000 54.00 

Sub total A 801.46 

6.0 Miscellaneous and ancillary works @ 

7.5% of sub-total A 

7.50% 60.11 

Sub total B 861.57 

7.0 Instrumentation @ 1% of sub-total B 1.00% 8.62 

8.0 Dewatering @ 2% of sub total B 2.00% 17.23 

9.0 Contingency @ 3% of sub-total B 3.00% 25.85 

10.0 Work Charged establishment @ 2% of 

Sub-total B except of lump-sum items 

2.00% 17.23 

Total 930.50

S. 

No. 

COFFER DAM 


(Rs.) 

143 



Amount 

(In 

Lakhs) 



2.0 Embankment Construction 

2.1 Earth/ Rockfill Cum 40,000 342 136.80 

2.2 Impervious Core Cum 15,000 354 53.10 

2.3 Filter Cum 4,000 901 36.04 

3.0 Concrete 

3.1 Concrete cut-off wall Sqm 900 20000 180.00 

Sub Total (A) 412.19 

4.0 Miscellaneous and ancillary works 

@ 0.50% of sub-total A 

0.50% 2.06 

Sub Total (B) 414.25 

5.0 Dewatering @ 3% of sub total-B 3.00% 12.43 

6.0 Contingency @ 3% of sub-total-B 3.00% 12.43 

7.0 Work Charged establishment @ 2% 

of Sub-total-B except of lump-sum 

items 

2.00% 8.29 

Total 447.39

S. 

No. 

CONCRETE DAM 

144 



Description Unit Quantity Rate Amount 

( Rs. in 

Lakhs) 




2.0 Rock Support system 

2.1 Rock bolts m 1,000 400 4.00 

2.2 shotcrete cum 500 4000 20.00 

3.0 Concrete 

3.1 M-15 cum 40,000 2930 1172.00 

3.2 M-20 cum 500 3390 16.95 

3.3 M-25 cum 7,000 3610 252.70 

4.0 Reinforcement steel MT 1,000 27000 270.00 


5.0 Miscellaneous and ancillary 

works @ 2.5% of sub-total 

2.5% 45.24 

Sub-Total (B) 1854.89 

6.0 Instrumentation @ 1% of sub-total 1% 18.55 

7.0 Dewatering @ 3% of sub total 3% 55.65 

8.0 Contingency @ 3% of sub-total 3% 55.65 

9.0 Work Charged establishment @ 

2% of Sub-total except of lumpsum 

items 

2% 37.10 

Total 2021.83

S. 

No. 

SPILLWAY 

145 



Description Unit Quantity Rate (Rs.) Amount 

( Rs. in 

Lakhs) 




2.0 Concrete 

2.1 M-15 cum 50,000 2930 1465.00 

2.2 M-25 cum 40,000 3610 1444.00 

3.0 Reinforcement steel MT 6,000 27000 1620.00 

4.0 Structural Steel T 150 42000 63.00 


5.0 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 

1.5% 69.25 


6.0 Instrumentation @ 1% of sub-total 1% 46.86 

7.0 Dewatering @ 3% of sub total 2% 93.72 

8.0 Contingency @ 3% of sub-total 3% 140.58 


2% of Sub-total except of lumpsum 

items 

2% 93.72 

Total 5060.88

146 



J -POWER PLANT APPURTENANCES (CIVIL WORKS) 

S. Description Amount (Rs. in Lakhs) 

No. civil HM Total 

1. Intake Structure 937.32 276.15 1213.47 

2. Desilting Chamber (Including S.F.T.) 5134.61 357.74 5492.35 

3. Adits 2094.05 25.20 2119.25 

4. Head Race & Tail Race Tunnel 12933.31 40.69 12974.00 

5. Surge Shaft 646.87 95.55 742.42 

6. Pressure Shafts And Penstocks 904.93 1591.28 2496.20 

7. Power House Complex 7039.30 187.95 7227.25 

8. Switchyard 222.18 222.18 

Total 29912.57 2574.55 32487.11 

Add For Works Tax @ 2% 598.25 51.49 649.74 

Grand Total 30510.82 2626.04 33136.86

S. 

No. 

INTAKE STRUCTURE 

147 



Description Unit Qty. Rate(Rs.) Amount 

( Rs. in 

Lakhs) 

1.0 Surface excavation 




3 Supports System 

2.1 Rock bolts m 9,000 400 36.00 

2.2 Steel Rib Supports MT 50 42000 21.00 

2.3 Shotcreting Cum 400 4000 16.00 


3.0 Concrete 

3.2 M15 Cum 2,000 2930 58.60 

3.3 M-20 Cum 500 3390 16.95 

3.4 M-25 Cum 10,000 3610 361.00 

4.0 Reinforcing Steel MT 500 27000 135.00 



works @ 1.5% of sub-total 

1.5% 12.95 


6.0 Instrumentation @ 1% of sub-total 

B 

1% 8.76 

7.0 Dewatering @ 1% of sub total B 1% 8.76 

8.0 Contingency @ 3% of sub-total B 3% 26.28 

9.0 Work Charged establishment 

@ 2% of Sub-total B except 

of lump-sum items 

2% 17.52 

Total 937.32

S. 

No. 

DESILTING CHAMBER (INCLUDING S.F.T.) 

148 



Description Unit Qty. Rate (Rs.) Amount 

( Rs. in 

Lakhs) 






3.1 Rock bolts m 81,000 400 324.00 

3.2 Steel Rib Supports MT 300 42000 126.00 

3.3 Shotcreting Cum 4,600 4000 184.00 


4.0 Concrete 

4.1 M15 Cum 18,000 2930 527.40 

4.2 M-20 Cum 1,500 3390 50.85 

4.3 M-25 Cum 30,000 3610 1083.00 

5.0 Reinforcing Steel MT 1,500 27000 405.00 



works @3.5% of sub-total 

3.5% 160.77 



B 

1% 47.54 



10.0 Work Charged establishment 

@ 2% of Sub-total B except 

of lump-sum items 

2% 95.09 

Total 5134.61

S. 

No. 

ADITS 


(Rs.) 

149 



Amount 

( Rs. in 

Lakhs) 





3.0 Supports System 

3.1 Rock bolts m 50,000 400 200.00 

3.2 Steel Ribs Support MT 200 42000 84.00 

3.3 Shotcrete Cum 2,000 4000 80.00 

3.4 Concrete lagging Cum 2,500 7000 175.00 

4.0 Concrete 

4.1 Cement Concrete lining M-20 Cum 2,000 4000 80.00 

4.2 Concrete in portals, backfill etc. 

M-15 Cum 8,500 2930 249.05 

M-20 Cum 1,200 3610 43.32 

5.0 Reinforcing steel MT 150 27000 40.50 



3.5% of sub-total A 

3.5% 65.57 


7.0 Instrumentation @ 1% of sub-total B 1% 19.39 




Sub-total except of lump-sum items 

2% 38.78 

Total 2094.05

S. 

No. 

HEAD RACE & TAIL RACE TUNNEL 

150 




( Rs. in 

Lakhs) 






3.1 Rock bolts m 222,000 400 888.00 

3.2 Steel Rib Supports MT 1,100 42000 462.00 

3.3 Shotcrete Cum 11,000 4000 440.00 


4.0 Concrete 

4.1 Cement Concrete Linning M20 Cum 60,000 4000 2400.00 

4.2 Concrete M15 Cum 49,000 2930 1435.70 

4.4 M-25 Cum 13,500 3610 487.35 

5.0 Reinforcement Steel MT 900 27000 243.00 

Sub-Total (A) 11139.80 


@7.5% of sub-total A 

7.5% 835.49 

Sub-Total (B) 11975.29 


B 

1% 119.75 




of Sub-total B except of lump-sum 

items 

2% 239.51 

Total 12933.31

S. 

No. 

SURGE SHAFT 

151 




( Rs. in 

Lakhs) 




2.0 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 

3.0 Support System 

3.1 Rock bolts m 11,000 400 44.00 

3.2 Steel Rib Support MT 25 42000 10.50 

3.3 Shotcrete Cum 500 4000 20.00 

4.0 Concrete 

4.1 M20 Cum 2,000 3390 67.80 

4.2 M-25 Cum 3,000 3610 108.30 

5.0 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 






of Sub-total B except of lump-sum 

items 

2% 11.98 

Total 646.87

S. 

No. 

PRESSURE SHAFTS AND PENSTOCKS 

152 




( Rs. in 

Lakhs) 



2.1 Rock bolts m 24,000 400 96.00 

2.2 Steel ribs support MT 175 42000 73.50 

2.3 Shotcrete Cum 1,000 4000 40.00 

3.0 Concrete 

3.1 Backfill concrete M15 Cum 12,000 2930 351.60 

Sub Total 

(A) 

825.10 


works @ 2.5% (sub-total) 

2.5% 20.63 

Sub Total 

(B) 

845.73 





2% of Sub-total B except of lumpsum 

items 

2% 16.91 

Total 904.93

S. 

No. 

POWER HOUSE COMPLEX 

153 




(Rs.) 

1.0 Under ground excavation 

Excavation of PH cavern, Transformer 

cum MIV cavern and draft tube gate 

Amount 

( Rs. in 

Lakhs) 

Cum 175,000 1000 1750.00 


2.1 Rock bolts m 70,000 400 280.00 

2.2 Steel ribs support MT 100 42000 42.00 

2.3 Shotcrete Cum 7,000 4000 280.00 


3.0 Concrete 

3.1 Backfill concreteM15 Cum 1,000 2930 29.30 

3.2 Concrete lining M20 Cum 3,000 3390 101.70 

3.3 M25 Cum 52,000 3610 1877.20 

4.0 Reinforcing Steel MT 6,000 27000 1620.00 

5.0 Structural Steel. MT 350 42000 147.00 

6.0 Masonry Work 

6.1 Stone Masonry Cum 500 2000 10.00 

6.2 Brick Masonry Cum 1,500 2000 30.00 



@4.5% of sub-total 

4.5% 280.7 







2% 130.36 

Total 7039.30

S. 

No. 

SWITCHYARD 

154 




(Rs.) 

Amount 

( Rs. in 

Lakhs) 





3.1 Rock bolts m 1,000 400 4.00 

3.2 Shotcrete Cum 50 4000 2.00 

4.0 Earthwork in filling Cum 25,000 342 85.50 

5.0 Concrete 

5.1 M15 Cum 1,000 2930 29.30 

5.2 M20 Cum 1,000 3390 33.90 

6.0 Reinforcing Steel MT 50 27000 13.50 

7.0 Masonry Work 

Stone Masonry/Brick Masonry Cum 300 2000 6.00 



@4.5% of sub-total A 

4.5% 8.94 






2% 4.15 

Total 222.18

S. 

No. 

HYDRO MECHANICAL EQUIPMENT 

155 



Detail of Items Unit Qnty. Rate (Rs.) Amount 

(Rs. In 

Lakh ) 

1 Diversion tunnel gate & hoist 

Gate(Fixed wheel type) including ballast- 

(3.0mx6.5m)-2 Nos. 

Ton 40 60000 24.00 

Embedded Parts -2 Sets Ton 12 50000 6.00 

Ropedrum hoist 55 T Capacity -2 Nos. Ton 40 100000 40.00 

Hoist platform and trestle - 2 Nos. Ton 40 50000 20.00 

2 Spillway structure 

a) Radial Gates (5.0m x 8.0m) - 4 Nos. Ton 240 100000 240.00 

Embedded Parts (including anchorages, 

hoist structure) including breast wall liners - 

4 Sets 

Ton 152 50000 76.00 

Hydraulic Hoist (One power pack + Two 

80T Cap. Hydraulic cylinders with 

provision of 25% pushing force) 

Set 4 6000000 240.00 

Portable oil filter unit along with 

Contamination checking kit & Low 

vacuum dehydration and degassification 

unit 

Portable trolley mounted gasoline engine 

operated power pack 

Set 1 750000 7.50 

Set 1 1000000 10.00 

Spillway Stoplogs( slide type) - 5.0m x 

10.0m - 1 Set 

Ton 40 60000 24.00 

Embedded Parts - 4 Sets Ton 48 50000 24.00 

Lifting Beam - 1 No. Ton 3 50000 1.50 

Gantry crane 25 T capacity Set 1 2500000 25.00 

3 Intake structure 

a) Trash rack cleaning machine Set 1 10000000 100.00 

TrashRacks and Embedded Parts including 

raking guides 

Ton 40 50000 20.00

156 



b) Intake Bulkhead Gate( slide type) -4.5m x 

4.5m - 2 Nos. 

Ton 30 60000 18.00 


Ropedrum hoist 30T Capacity - 2 Nos. 

Hoist platform and trestles (Included in the 

intake service gate) 

Ton 20 100000 20.00 

b) Intake service gate(fixed wheel type) 

including ballast - 4.5m x 4.5m - 2Nos. 

Ton 60 60000 36.00 


Ropedrum hoist 60T Capacity - 2 Nos. Ton 40 100000 40.00 

Hoist platform and trestles (Including 

bulkhead gate) - 2 Sets 

Ton 40 50000 20.00 

4 Desilting Chamber gate ( slide type) - 

6.0m x 6.0m - 1 No. 

Ton 27 60000 16.20 


EOT Crane 50T Capacity Set 1 4500000 45.00 

5 Silt Flushing gates (slide type) 

Gates (service & emergency) -3.0m x 2.0m 

- 4 Nos. 

Embedded Parts (including bonnet,bonnet 

cover, gate body liner etc) - 4 Sets 

Hydraulic Hoist (Two double acting 

cylinders 240T capacity each and one 

power pack) 

Ton 32 100000 32.00 

Ton 120 50000 60.00 

Set 2 9000000 180.00 

6 Surge shaft gate & hoist 

Gate(Slide Type)- 4.0m x 6.0m - 2 Nos. Ton 60 60000 36.00 

Embedded parts- 2 Sets Ton 30 50000 15.00 

Rope drum hoist 50T Cap. - 2 Nos. Ton 30 100000 30.00 

Hoist platform and trestle- 2 Sets Ton 20 50000 10.00 

7 Draft Tube gates & hoist 

Gate(Fixed wheel type)- 6.0m x 6.0m - 4 

Nos. 

Ton 140 60000 84.00 


Rope drum hoist 50 T Cap.- 4 Nos. Ton 60 100000 60.00

157 



Hoist platform and trestle- 4 Sets Ton 30 50000 15.00 

8 Tail race gates & hoist 

Gate(Slide Type) - 6.0m x 6.0m - 1 No. Ton 25 60000 15.00 

Embedded Parts - 1 Set Ton 7.5 50000 3.75 

Rope drum hoist 50 T Cap.- 1 No. Ton 15 100000 15.00 

Hoist platform and trestle - 1 Set Set 10 50000 5.00 

9 Pressure shaft steel Liner 

Ferrules (ASTM A 537Cl-I) - 2 Sets Ton 2000 70000 1400.00 

Bifurcation, (ASTM A 517Gr. F) - 2 Sets Ton 150 77000 115.50 

10 Adit Gates 

Adit gates - 2.5m x 2.5m - 3 Nos. Ton 30 60000 18.00 


11 Instruments and Remote Control Set 1 10000000 100.00 

12 D G Set 250 KVA Set 1 1250000 12.50 

13 Spare parts & contingency (5% of total 

cost) 

5% 165.12 

Total 3467.57

S. 

No. 

K - BUILDINGS 

Description of Buildings Plinth 

Area 

158 



Rs.in 

lakhs 

Rate Unit Amount 

1.0 Residential Buildings 

i Permanent residential buildings 3960 0.075 Sqm 297.00 

Service Charges @ 31% 92.07 

ii Temporary residential buildings 3970 0.065 Sqm 258.05 

Service Charges @ 27% 69.67 

Residential Buildings 7930 716.79 

2.0 Non - Residential Buildings 

i Non residential permanent buildings 3485 0.065 Sqm 226.53 

Service Charges @ 22.5% 50.97 

ii Non residential and other purposes 

temporary buildings 

4105 0.055 Sqm 225.78 

Service Charges @ 20.5% 46.28 

Total Non - residential Buildings 7590 549.55 

Total 15520 1266.35 

Add Works Tax @ 2% 25.33 

Grand Total 1291.67

S. 

No. 

O-MISCELLANEOUS 

159 



(Rs. In Lakh) 

Description Quantity Unit Rate Amount 

1.0 CAPITAL COST 

1.1 Purchase of Diesel Generator Sets 

(25 KVA) including ancillary 

equipments etc. 

1.2 Cost of transmission line for 

construction power 

1.2 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. 

3.00 Nos 2.50 7.50 

15.00 km 10.00 150.00 

LS 30.00 

LS 25.00 

LS 20.00 

1.6 Providing telephone, Telegraph 

office, Post office and Wireless 

equipments. 

LS 20.00 

1.7 Providing hospital equipments. LS 15.00 

1.8 Construction of children park and 

welfare centres for officials and 

labourers. 

LS 8.00 

1.9 Furnishing and equipping of rest 

houses and field hostels of officers 

and staff. 

1.10 Purchase of furniture and other 

articles for labour welfare centres 

and clubs and schools. 

1.11 Purchase of equipment for quality 

control/field Laboratories 

LS 5.00 

LS 5.00 

LS 15.00 

Sub Total Item 1 300.50

2.0 MAINTENANCE & SERVICE CHARGES 

OF 

2.1 R&M of Diesel Generator sets 3 

Nos. for five years. 

2.2 R&M of Transmission line for five 

years. 

2.3 R&M of water supply facilities to 

the staff and labour colonies 

2.4 R&M of sanitation and drainage 

facilities for office and residential 

complex and labour colonies. 

160 



15.00 Nos 5.00 75.00 

20.00 km 5.00 100.00 

LS 10.00 

LS 8.00 

2.5 R&M of fire fighting equipments. LS 4.00 

2.6 Maint. Of telecommunication 

system and post offices. 

LS 20.00 

2.7 R&M of hospitals. LS 16.00 

2.8 Maint. of parks and welfare centres, 

clubs and school. 

LS 10.00 

2.9 R&M of Rest houses and field 

hostels. 

LS 8.00 

2.10 R&M of research & quality control 

laboratories 

LS 8.00 

2.11 Labour welfare compensation and 

retrenchment benefits. 

LS 40.00 

2.12 Providing Security & Policing LS 8.00 

2.13 R&M of Inspection vehicles and 

staff cars (25 nos) for five 

years 

25*5 year 2.50 312.50 

2.14 R&M of school buses, Ambulance 

Car etc. (4 nos) for five years 

4*5 year 1.80 36.00 

Sub Total Item 2 655.50 

3.0 MISCELLANEOUS 

3.1 Foundation stone laying ceremony, 

inauguration and visit of 

Dignitaries. 

LS 30.00 

3.2 Railway siding LS 20.00 

3.3 Installation and maintenance of 

Petrol/Diesel Pumps 

LS 16.00

161 



3.4 Providing anti malarial measures LS 2.00 

3.5 Procurement of technical literature. LS 2.00 

3.6 Model Exhibits LS 4.00 

3.7 Canteen facilities and co-operative 

LS 12.00 

stores. 

3.8 Photographic and Cinematographic 

equipment and their maintenance 

LS 8.00 

3.9 Group insurance LS 15.00 

3.10 Publication and pamphlets LS 2.00 

3.11 Creches LS 2.00 

3.12 Compensation for accident LS 8.00 

3.13 Training of personnels aboard 

including study course and visit 

LS 15.00 

3.14 Award to workers LS 1.5 

Sub Total Item 3 137.50 

Grand Total Item (1+2+3) 1093.50

Q-Spl T&P for Infrastructure Development 

Sl.No. Description of equipment Quantity 

(Nos.) 

162 



(Rs in Lacs) 

Rate Amount 

1 Hydraulic Excavator, 1.0 cum. 1 50.00 50.00 

2 Loader cum Excavator, 1.0/0.25 

cum. 

1 20.00 20.00 

3 Crawler Dozer, 100 FHP 2 50.00 100.00 

4 Wheel dozer 300 HP 1 95.00 95.00 

5 Motor Grader, 145 FHP 1 60.00 60.00 

6 Diamond Core Drill (Mechanical) 2 15.00 30.00 

7 Diamond Core Drill (Hyd) 1 60.00 60.00 

8 Air Track/Wagon Drill 2 16.00 32.00 

9 Jack Hammer/Pavement Breaker 5 0.35 1.75 

10 Compressed Air (cfm) 2000 0.0125 25.00 

11 Mobile Crane, 10 t Pick & Carry 2 10.00 20.00 

12 Mobile Crane, 20 t (Rough terrain) 1 70.00 70.00 

13 Road Roller, 8/10 t 2 10.00 20.00 

14 Dewatering Pump L.S 20.00 20.00 

15 Tipper 4.5/6.0 cum. 4 10.00 40.00 

16 Truck, 10 t 4 8.00 32.00 

17 Low Bed Tractor Trailor, 30 t 1 50.00 50.00 

18 Concrete Mixer, 14/10 cft 2 2.00 4.00 

19 Explosive Van, 10 t 1 12.00 12.00 

20 Water Tanker/Sprinkler, 10 KL 1 15.00 15.00 

21 Petrol/Diesel Tanker, 10 KL 1 12.00 12.00 

22 Bus/Mini Bus 5 10.00 50.00 

23 Car/MUV 4 5.50 22.00 

24 Jeep (Petrol/Diesel) 20 4.50 90.00 

25 Ambulance 2 10.00 20.00 

26 Workshop Equipment L.S 20.00 20.00 

27 Fire Tender 1 15.00 15.00 

28 Recovery Van 1 5.00 5.00 

29 Pick up Van/L.C.V 2 5.00 10.00 

1000.75

S. 

No. 

163 



R - COMMUNICATION 

Description Quantity Unit 

Rs. In Lakhs 

Rate Amount 

1 Improvement/Reconstruction of 

bridges on existing District Road 

from Mangan to Lingza 

Bridges 

Bridge on Lingza road 2.0 Nos 30.00 60.00 

Bridge across the river Rangyong 

Roads 

120.0 m 2.25 270.00 

To lingza 4.0 Km 60.00 240.00 

Widening on curves 6.0 Nos 1.50 9.00 

Suspension Bridge to Rungto 

(Adit-II) 

1.5 Km 60.00 90.00 

Rungto (Adit-II) to Laven (Adit-I) 4.5 Km 60.00 270.00 

2 Proposed new roads 

Approach road to dam site, DT, 

Top of Dam 

3.0 Km 80.00 240.00 

Approach road to power house site 0.8 Km 80.00 64.00 

Switch yard 1.0 Km 75.00 75.00 

Surge shaft 2.0 Km 75.00 150.00 

Adit-III/II/I 4.6 Km 75.00 345.00 

Colony Roads 2.0 Km 75.00 150.00 

3 Proposed new bailey bridges Cl 

30 

At Dam site 40.0 m 2.25 90.00 

Grand Total 2053.00 

Add Works Tax @ 2% 41.06 

Grand Total 2094.06

S. 

No. 

V - RECEIPT & RECOVERIES 

Item Amount 

164 

(Rs. In Lakhs) 

1. Recovery from the Sale of Equipments 190.10 

2. Recovery from Resale of DG Sets 1.50 

3. Recovery from Temporary Building 89.97 

Total 281.57 



165 



ELECTRO MECHANICAL WORKS 

Annex-I Page 1 of 2 

Generator, Turbine and Accessories 

S.N Item Particulars Qty Unit Rate Amount 

Dec 2003 Price Level 

Excise Duty* Total 

(Rs in Rate Amount (Rs. In 

Lakh) % (Rs. In 

Lakh) 

Lakh) 

1 2 3 3(a) 4 5 6 7 5+7 

1 (a) Generating units and Bus Ducts 4 no. 4600.00 9200.00 16 1472.00 10672.00 

4X50 MW, 500 rpm, Head 312 

meters 

Rs/KW 

2 

3 

4 

Step up transformer,3 phase 11/ 220 

KV, 62 MVA, 

Auxiliary Electrical Equipment for 

Power Stations (Except 

Transformer) (5% of item 1) 

Auxiliary Equipment & Services for 

Power stations (5% of Item 1) 

4 no. 220.00 545.60 16 87.30 632.90 

460 16 73.6 533.60 

460 16 73.6 533.60 

5 Spares (5% of 1 and 3% of 2 to 4) ) 460 43.97 503.97 16 80.635 584.60 

6 SUB TOTAL(1-5) 

12956.70 

7 Central Sales tax **4% of item 6 518.27 

8 

9 

Transportation & Insurance 6% of 

item 6 

Erection & commissioning 8% of 

item 6 Excluding spares 

10 Sub total item 6,7, 8,9 

11 Total of FC(GIS,XLPE Cable and 

Termination kit) in INR(As per 

Annexure-I) 

12 Custom Duty @22% of item 11 included in above item 11 

13 Marine frieght and insurance @6% 

Approx of 11 

14 Inland Frieght and insurance 6% of 

item 11 

15 Erection & commissioning 8% of 

item 11 Excluding spares 

16 SUB TOTAL of FC ( item 

11,12,13,14,15, in INR) 

17 Subtotal of item no 16+10(Foreign 

plus indian component) 

18 Establishment,Contingency,other 

charges (11% of Item17 excluding 

duties) 

GRAND TOTAL (Rs in Lakh) 

777.40 

989.77 

15242.14 

3445.98 

206.76 

206.76 

275.52 

4135.01 

19377.15 

1539.36 

20916.51

166 



Annex-I Page 2 of 2 

S.N Item Particulars Qty Rate Amount Custom Duty* Total 

( USD in 

Lakh) 

Rate 

% 

Amount ( 

USD in 

Lakh) 

(USD in 

Lakh) 

1 2 3 4 5 6 7 5+7 

1 220 KV GIS BAY 

6.521 

(USD in 

45.65 22 10.04 55.69 

7 

Lakh) 

2 XLPE Cable (220 kV) 350 m 280.00 9.80 22 2.16 11.96 

0 

(USD) 

3 XLPE Cable termination Kit 

no. 35000.00 4.90 22 1.08 5.98 

14 

(USD) 

4 Spares for above @ 3% of 1 & 2 

1.66 22 0.37 2.03 

Total 62.01 75.65 

*Custom duty in case of 

**Not applicable for Imported 

1 USD conversion rate as on 15/12/03= 45.55 

POWER EVACUATION SYSTEM 

Dec 2003 Price Level 

Annex-II (page 1 of 1) 

S.N Item Particulars Qty Rate Amoun Total 

(Rs (Rs Rate Amount (Rs 

1 2 3 4 5 6 7 5+7 

1 220kV Double Circuit line 5 km 22.00 110.00 16 17.60 127.60 

3 Spares ( 3% of 1 ) 3.3 16 0.528 3.83 

4 Subtotal(1) 131.43 

5 Central Sales tax **4% of item 4 #REF! 5.26 

6 Transportation & Insurance 6% 

of item 4 7.89 

7 Erection & commissioning 8% 

of item 4 except spares 10.21 

8 Subtotal(2) 154.78 

9 Establishment,Contingency, 

other charges (11% of Item 8) 

12.46 

GRAND TOTAL (In Lacs) 167.24 

*Custom duty in case of 

**Not applicable for Imported 

1 USD conversion rate as on 15/12/03= 45.55

167 



CHAPTER – XIII 

ECONOMIC EVALUATION 

167 



13.1 GENERAL 

The Project has been contemplated as a run-off the river scheme on river Tolung Chu / 

Rangyong. The project is estimated to cost Rs. 764.94 crores excluding IDC at June 

2003 Price Level. Sale price of energy generated at powerhouse bus bars has been 

worked out as 2.45 Rs. per unit (Table 13.2) & without free power to state government 

comes to Rs. 2.15 per unit (Table 13.2-A). 

13.2 ECONOMIC JUSTIFICATION: 

The energy generation of the project with an installed capacity of 4 X 50 MW has been 

estimated at 762 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. 764.94 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 30.60 

2 nd 68.84 

3 rd 

168 

99.44 

4 th 130.04 

5 th 191.24 

6 th 145.34 

6.5 th 99.44 

Net Cost 764.94 



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 81.14 Crores 

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

169 



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. 1.99 Per Unit 

(Table 13.3) & tariff without free power to state government comes to Rs. 1.75 per unit 

(Table 13.3-A).

170 



STATEMENT SHOWING IDC CALCULATION AT PRESENT DAY COST (JUNE 2003 LEVEL) 

Table-13.1 

PRESENT DAY COST 764.94 Crs. Electrical Works 209.17 Crs. 

Civil Works 554.10 Crs. Transmission cost 1.67 Crs. 

INTEREST RATE PER ANNUM 10% 

(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 30.60 30.60 30.60 

2 68.84 68.84 68.84 

3 99.44 99.44 99.44 

4 130.04 54.94 75.10 2.17 77.27 54.94 77.27 

5 191.24 191.24 17.29 285.79 208.52 

6 145.34 145.34 35.85 466.98 181.19 

6.5 99.44 99.44 25.83 592.26 125.28 

Total 764.94 253.82 511.12 81.14 253.82 592.26 

IDC 81.14 Crs. Equity 253.82 Crs. 

Net cost of the 

project 846.08 Crs. Loan 592.26 Crs.

171 



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 200 MW 

2 Cost of the Project (Net) Rs. 764.94 Crores 

3 Interest During Construction Rs. 81.14 Crores 

4 Total Cost of Project Rs. 846.08 Crores 

(Including IDC) 

a) Equity 30% Rs. 253.82 Crores 

b) Loan 70% Rs. 592.26 Crores 

5 Annual Energy Generation 762.00 MU 

6 0.7% As Auxiliary Consumption of No. 5 0.70% 5.33 MU 

7 Energy Available After Auxiliary Consumption 756.67 MU 

8 0.5% As Transformer Loss of No. 7 0.50% 3.78 MU 

9 Energy Available After Transformer Loss 752.88 MU 

10 Free Power to Home State 12% 90.35 MU 

11 

Energy Available After Allowing Free 

Power 662.54 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 56.76 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

49.35 Crores 

Sub-Total 106.11 Crores 

B) Energy Charges 

a) O&M Charges 1.50% 12.69 Crores 

b) Return on Equity 16.00% 40.61 Crores 


c) Interest on Working Capital 10.00% 2.81 Crores 

I) O&M Charges for 1 month 1.06 

II) 2 Months Average Billing 27.04 

Total Rs. 162.22 Crores 

13 Sale Price at Bus Bar/Unit 2.45 Rs. 

14 Cost of Generation at Bus Bar/Unit 1.62 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.

172 



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 200 MW 

2 Cost of the Project (Net) Rs. 764.94 Crores 

3 Interest During Construction Rs. 81.14 Crores 

4 Total Cost of Project Rs. 846.08 Crores 

(Including IDC) 

a) Equity 30% Rs. 253.82 Crores 

b) Loan 70% Rs. 592.26 Crores 

5 Annual Energy Generation 762.00 MU 

6 0.7% As Auxiliary Consumption of No. 5 0.70% 5.33 MU 

7 Energy Available After Auxiliary Consumption 756.67 MU 

8 0.5% As Transformer Loss of No. 7 0.50% 3.78 MU 

9 Energy Available After Transformer Loss 752.88 MU 

10 Free Power to Home State 0% 0.00 MU 

11 

Energy Available After Allowing Free 

Power 752.88 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 56.76 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

49.35 Crores 


B) Energy Charges 

a) O&M Charges 1.50% 12.69 Crores 

b) Return on Equity 16.00% 40.61 Crores 


c) Interest on Working Capital 10.00% 2.81 Crores 

I) O&M Charges for 1 month 1.06 

II) 2 Months Average Billing 27.04 

Total Rs. 162.22 Crores 

13 Sale Price at Bus Bar/Unit 2.15 Rs. 

14 Cost of Generation at Bus Bar/Unit 1.62 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.

173 



CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION 

Table-13.3 

Annual Generation in a 90% dependable 762 MU O&M Charges 1.50% 

Annual Generation after allowing losses& Rate of increase of O&M Charges after 1st Year (Compounded) 6% 

power to home state in a 90% dependable 662.54 MU Interest rate on 10.0% 

Total cost including IDC Rs. 846.08 Crores Interest rate on Working 10.00% 

Equity 30% Rs. 253.82 Crores Return on 16% 

Loan 70% Rs. 592.26 Crores Discounting rate 12% 

YEAR CAPACITY (Rs.in Cr.) CHARGES PER UNIT Discounting Discounted 

Out- (Rs.in Cr.) (Rs. per Factor Tariff 

standing Interest Depre- Total Return O&M Interest on Working Capital Total Capacity Energy Total 

(Paisa per 

Loan on loan ciation on Charges O&M 2months Interest charges charges Unit) 

(Rs.in 

equity 

1 month Average 

Billing 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

1 592.26 56.76 49.35 106.11 40.61 12.69 1.06 27.04 2.81 56.11 1.60 0.85 2.45 1.0000 2.45 

2 542.90 51.82 49.35 101.18 40.61 13.45 1.12 26.33 2.75 56.81 1.53 0.86 2.38 0.8929 2.13 

3 493.55 46.89 49.35 96.24 40.61 14.26 1.19 25.63 2.68 57.55 1.45 0.87 2.32 0.7972 1.85 

4 444.19 41.95 49.35 91.31 40.61 15.12 1.26 24.94 2.62 58.35 1.38 0.88 2.26 0.7118 1.61 

5 394.84 37.02 49.35 86.37 40.61 16.02 1.34 24.26 2.56 59.19 1.30 0.89 2.20 0.6355 1.40 

6 345.48 32.08 49.35 81.44 40.61 16.98 1.42 23.59 2.50 60.10 1.23 0.91 2.14 0.5674 1.21 

7 296.13 27.15 49.35 76.50 40.61 18.00 1.50 22.93 2.44 61.06 1.15 0.92 2.08 0.5066 1.05 

8 246.77 22.21 49.35 71.56 40.61 19.08 1.59 22.27 2.39 62.08 1.08 0.94 2.02 0.4523 0.91 

9 197.42 17.27 49.35 66.63 40.61 20.23 1.69 21.63 2.33 63.17 1.01 0.95 1.96 0.4039 0.79 

10 148.06 12.34 49.35 61.69 40.61 21.44 1.79 21.00 2.28 64.33 0.93 0.97 1.90 0.3606 0.69 

11 98.71 7.40 49.35 56.76 40.61 22.73 1.89 20.39 2.23 65.57 0.86 0.99 1.85 0.3220 0.59 

12 49.35 2.47 49.35 51.82 40.61 24.09 2.01 19.78 2.18 66.88 0.78 1.01 1.79 0.2875 0.52 

13 7.36 7.36 40.61 25.54 2.13 12.49 1.46 67.61 0.11 1.02 1.13 0.2567 0.29 

14 7.36 7.36 40.61 27.07 2.26 12.76 1.50 69.18 0.11 1.04 1.16 0.2292 0.26 

15 7.36 7.36 40.61 28.69 2.39 13.03 1.54 70.85 0.11 1.07 1.18 0.2046 0.24 

16 7.36 7.36 40.61 30.42 2.53 13.33 1.59 72.61 0.11 1.10 1.21 0.1827 0.22 

17 7.36 7.36 40.61 32.24 2.69 13.64 1.63 74.48 0.11 1.12 1.24 0.1631 0.20 

18 7.36 7.36 40.61 34.17 2.85 13.97 1.68 76.47 0.11 1.15 1.27 0.1456 0.18 

19 7.36 7.36 40.61 36.22 3.02 14.32 1.73 78.57 0.11 1.19 1.30 0.1300 0.17 

20 7.36 7.36 40.61 38.40 3.20 14.69 1.79 80.80 0.11 1.22 1.33 0.1161 0.15 

21 7.36 7.36 40.61 40.70 3.39 15.09 1.85 83.16 0.11 1.26 1.37 0.1037 0.14 

22 7.36 7.36 40.61 43.14 3.60 15.50 1.91 85.67 0.11 1.29 1.40 0.0926 0.13 

23 7.36 7.36 40.61 45.73 3.81 15.95 1.98 88.32 0.11 1.33 1.44 0.0826 0.12 

24 7.36 7.36 40.61 48.48 4.04 16.42 2.05 91.13 0.11 1.38 1.49 0.0738 0.11 

25 7.36 7.36 40.61 51.39 4.28 16.91 2.12 94.12 0.11 1.42 1.53 0.0659 0.10 

26 7.36 7.36 40.61 54.47 4.54 17.44 2.20 97.28 0.11 1.47 1.58 0.0588 0.09 

27 7.36 7.36 40.61 57.74 4.81 18.00 2.28 100.63 0.11 1.52 1.63 0.0525 0.09 

28 7.36 7.36 40.61 61.20 5.10 18.59 2.37 104.18 0.11 1.57 1.68 0.0469 0.08 

29 7.36 7.36 40.61 64.87 5.41 19.22 2.46 107.95 0.11 1.63 1.74 0.0419 0.07 

30 7.36 7.36 40.61 68.77 5.73 19.88 2.56 111.94 0.11 1.69 1.80 0.0374 0.07 

31 7.36 7.36 40.61 72.89 6.07 20.59 2.67 116.17 0.11 1.75 1.86 0.0334 0.06 

32 7.36 7.36 40.61 77.27 6.44 21.34 2.78 120.65 0.11 1.82 1.93 0.0298 0.06 

33 7.36 7.36 40.61 81.90 6.83 22.13 2.90 125.41 0.11 1.89 2.00 0.0266 0.05 

34 7.36 7.36 40.61 86.82 7.23 22.97 3.02 130.45 0.11 1.97 2.08 0.0238 0.05 

35 7.36 7.36 40.61 92.02 7.67 23.86 3.15 135.79 0.11 2.05 2.16 0.0212 0.05 

TOTAL 9.1566 18.19 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax Levellised 1.99

CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION 

WITHOUT FREE POWER TO HOME STATE 

174 



Table-13.3 A 

Annual Generation in a 90% dependable year 762 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 752.88 MU Interest rate on 10.0% 

Total cost including IDC Rs. 846.08 Crores Interest rate on Working 10.00% 

Equity 30% Rs. 253.82 Crores Return on 16% 

Loan 70% Rs. 592.26 Crores Discounting rate 12% 

YEAR CAPACITY 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 on loan ciation on Charges O&M 2months Interest charges charges Unit) 

(Rs.in Cr.) 1 month Average 

equity 

Billing 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

1 592.26 56.76 49.35 106.11 40.61 12.69 1.06 27.04 2.81 56.11 1.41 0.75 2.15 1.0000 2.15 

2 542.90 51.82 49.35 101.18 40.61 13.45 1.12 26.33 2.75 56.81 1.34 0.75 2.10 0.8929 1.87 

3 493.55 46.89 49.35 96.24 40.61 14.26 1.19 25.63 2.68 57.55 1.28 0.76 2.04 0.7972 1.63 

4 444.19 41.95 49.35 91.31 40.61 15.12 1.26 24.94 2.62 58.35 1.21 0.77 1.99 0.7118 1.41 

5 394.84 37.02 49.35 86.37 40.61 16.02 1.34 24.26 2.56 59.19 1.15 0.79 1.93 0.6355 1.23 

6 345.48 32.08 49.35 81.44 40.61 16.98 1.42 23.59 2.50 60.10 1.08 0.80 1.88 0.5674 1.07 

7 296.13 27.15 49.35 76.50 40.61 18.00 1.50 22.93 2.44 61.06 1.02 0.81 1.83 0.5066 0.93 

8 246.77 22.21 49.35 71.56 40.61 19.08 1.59 22.27 2.39 62.08 0.95 0.82 1.78 0.4523 0.80 

9 197.42 17.27 49.35 66.63 40.61 20.23 1.69 21.63 2.33 63.17 0.88 0.84 1.72 0.4039 0.70 

10 148.06 12.34 49.35 61.69 40.61 21.44 1.79 21.00 2.28 64.33 0.82 0.85 1.67 0.3606 0.60 

11 98.71 7.40 49.35 56.76 40.61 22.73 1.89 20.39 2.23 65.57 0.75 0.87 1.62 0.3220 0.52 

12 49.35 2.47 49.35 51.82 40.61 24.09 2.01 19.78 2.18 66.88 0.69 0.89 1.58 0.2875 0.45 

13 7.36 7.36 40.61 25.54 2.13 12.49 1.46 67.61 0.10 0.90 1.00 0.2567 0.26 

14 7.36 7.36 40.61 27.07 2.26 12.76 1.50 69.18 0.10 0.92 1.02 0.2292 0.23 

15 7.36 7.36 40.61 28.69 2.39 13.03 1.54 70.85 0.10 0.94 1.04 0.2046 0.21 

16 7.36 7.36 40.61 30.42 2.53 13.33 1.59 72.61 0.10 0.96 1.06 0.1827 0.19 

17 7.36 7.36 40.61 32.24 2.69 13.64 1.63 74.48 0.10 0.99 1.09 0.1631 0.18 

18 7.36 7.36 40.61 34.17 2.85 13.97 1.68 76.47 0.10 1.02 1.11 0.1456 0.16 

19 7.36 7.36 40.61 36.22 3.02 14.32 1.73 78.57 0.10 1.04 1.14 0.1300 0.15 

20 7.36 7.36 40.61 38.40 3.20 14.69 1.79 80.80 0.10 1.07 1.17 0.1161 0.14 

21 7.36 7.36 40.61 40.70 3.39 15.09 1.85 83.16 0.10 1.10 1.20 0.1037 0.12 

22 7.36 7.36 40.61 43.14 3.60 15.50 1.91 85.67 0.10 1.14 1.24 0.0926 0.11 

23 7.36 7.36 40.61 45.73 3.81 15.95 1.98 88.32 0.10 1.17 1.27 0.0826 0.11 

24 7.36 7.36 40.61 48.48 4.04 16.42 2.05 91.13 0.10 1.21 1.31 0.0738 0.10 

25 7.36 7.36 40.61 51.39 4.28 16.91 2.12 94.12 0.10 1.25 1.35 0.0659 0.09 

26 7.36 7.36 40.61 54.47 4.54 17.44 2.20 97.28 0.10 1.29 1.39 0.0588 0.08 

27 7.36 7.36 40.61 57.74 4.81 18.00 2.28 100.63 0.10 1.34 1.43 0.0525 0.08 

28 7.36 7.36 40.61 61.20 5.10 18.59 2.37 104.18 0.10 1.38 1.48 0.0469 0.07 

29 7.36 7.36 40.61 64.87 5.41 19.22 2.46 107.95 0.10 1.43 1.53 0.0419 0.06 

30 7.36 7.36 40.61 68.77 5.73 19.88 2.56 111.94 0.10 1.49 1.58 0.0374 0.06 

31 7.36 7.36 40.61 72.89 6.07 20.59 2.67 116.17 0.10 1.54 1.64 0.0334 0.05 

32 7.36 7.36 40.61 77.27 6.44 21.34 2.78 120.65 0.10 1.60 1.70 0.0298 0.05 

33 7.36 7.36 40.61 81.90 6.83 22.13 2.90 125.41 0.10 1.67 1.76 0.0266 0.05 

34 7.36 7.36 40.61 86.82 7.23 22.97 3.02 130.45 0.10 1.73 1.83 0.0238 0.04 

35 7.36 7.36 40.61 92.02 7.67 23.86 3.15 135.79 0.10 1.80 1.90 0.0212 0.04 

TOTAL 9.1566 16.01 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax etc. Levellised Tariff =(B)/(A) 1.75

Panan - Ministry of Power

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