Ringpi - Ministry of Power

CHAPTER 

I 

TABLE OF CONTENTS 

DESCRIPTION 

Executive Summary 

Preliminary Feasibility Report 

Ringpi HE Project (2 x 35MW) 

PAGE NO. 

1-10 

II Background Information 11-18 

III Project Area 19-25 

IV Topographical & Geo-technical Aspects 26-33 

V Hydrology 34-56 

VI Conceptual Layout and Planning 57-67 

VII Power Potential Studies 68-100 

VIII Power Evacuation 101 

IX Environmental Aspects 102-121 

X Infrastructure 122-125 

XI Construction Planning & Schedule 126-131 

XII Cost Estimate 132-168 

XIII Economic Evaluation 169-176 

Plates 

Annexures

TITLE 

LIST OF PLATES 



PLATE 

No. 

Preliminary Ranking Study Layout 1 

Cascade Development of Teesta River Basin 2 

Layout Plan of Schemes in Upper Part of Teesta Basin 3 

Cascade Development of Tolung River Basin 4 

Geological Plan of The Project Area 4.1 

Vicinity Map 6.1 

Layout Plan 6.2 

Dam Area Layout Plan 6.3 

Power House Area Layout Plan 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 

Single Line Diagram – Power Evacuation 8.1 

6.8

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 

Record note of discussions on conceptual layout of 

the project. 

6.2 

Reply on CEA/CWC Comments on Draft PFR 6.3


Ringpi HE Project (2x 35MW) 

CHAPTER – I 

EXECUTIVE SUMMARY

1.0 INTRODUCTION 

CHAPTER-I 

EXECUTIVE SUMMARY 

1 


Ringpi HE Project (2 x 35 MW) 

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

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

generation on a run of river type development, harnessing a gross head of about 1110m. 

The project with a proposed installation of 70MW (2 x 35 MW) would afford an annual 

energy generation of 317.41 GWh in a 90% dependable year. The tariff from the project 

at present day cost would be Rs.2.93 per KWh(levellised). 

The diversion site is located at Latitude 27º40’35” North, Longitude 88º26’39” East. The 

dam site is approachable from road head ending at Lingza by a footpath of about 16 km 

length. The Power house site is approachable by a foot path of about 6.0 km length from 

road head at Lingza and about 17 km by road 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 Ringpi HE Project envisages construction of : 

• a 40 m high concrete Dam across river Ringpi to provide a live storage of 0.567 

mcum. with FRL at 2966m and MDDL at 2963m; 

• one intake and one desilting chamber of size 50m(L)x5m(W)x7.5m(H) to remove 

silt particles of size 0.2mm and above; 

• a 7 km long , 3.3m diameter head race tunnel terminating in a surge shaft; 

• a 50m high, 10m dia surge shaft; 

• 1750m long, 1.5m dia one pressure shaft;

2 



• an underground power house having an installation of 2 Vertical Pelton turbine 

generating units of 35 MW each operating under a net head of 1106m; and 

• 250m long, 3.3m diameter tailrace tunnel to carry the power house release back to 

the river; 

The power generated from the project would be evacuated through one number 220KV 

double circuit lines to a proposed pooling station near Teesta(II) HE Project to feed 

power to the national grid. 

The salient features of the projects are as under; 

LOCATION 

SALIENT FEATURES 

State Sikkim 

District North Sikkim 

River Ringpi Chu 

Location of Dam Site Just d/s of confluence of Jhumthul Chu 

Location of Power house 

and Kishong Chu 

Just u/s of reservoir of Lingza 

H.E. Scheme 

Nearest Rail head New Jalpaiguri 

Nearest Airport Bagdogra 

Latitude of dam & Power house 27º40’35’’& 27º36’21’’ 

Longitude of dam & Power house 88º26’39’’& 88º27’09’’ 

HYDROLOGY 

Catchment area 126 km 2

Design Flood (PMF) 675 m 3 /sec 

DIVERSION TUNNEL 

Diameter & Shape 3.3 m, Horse-shoe shaped 

Length 400 m 

Diversion Discharge ±100 m 3 /sec 

Diversion Tunnel Gate 1 No. Vertical lift gate 

Size of Gate 3.3 m × 4 m 

COFFER DAMS 

Type Rockfill with central clay core. 

Maximum height of upstream coffer dam ± 15.0 m 

Maximum height of downstream coffer 

dam 

DAM 

3 

± 8.0 m 

Type Concrete Gravity 

Dam Top EL. 2970.0 m 

River bed level at dam site EL.2940.0 m 

Maximum Dam height (above deepest 

foundation level) 

40 m 

Length of the Dam 300 m 

Dam height (above River bed level) 30 m 

SPILLWAY 

Type Orifice Type 

No. of bays 3 

Crest level of spillway EL. 2950.0 m 

Size of the opening 4m(w) X 7m(H) 


Ringpi HE Project (2 x 35 MW)

Design flood (PMF) 675 m 3 /sec 

RESERVOIR 

Full Reservoir Level (FRL) EL.2966.0 m 

Minimum draw down level (MDDL) EL.2963.0 m 

Area under submergence at FRL 12.70 Ha 

Gross Storage 1.856 MCM 

Live Storage 0.567 MCM 

INTAKE 

Number One 

Invert level EL.2955.0 m 

Size of each Gate 3.3 m × 3.3 m 

4 



Trash Rack Steel Trash Racks with Raking Machine 

Design discharge 8.68 m 3 /sec 

DESILTING ARRANGEMENT 

No., Type & size of desilting chamber 1 Nos.,Dufour type chamber 50 m long, 5 

m x 7.5m 

Total Design Discharge 8.68 m 3 /sec 

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

SILT FLUSHING TUNNEL 

Size & shape 0.75 m x 1.5 m , D-shaped

HEADRACE TUNNEL 

5 



Size & type 3.3 m Dia, Horse –shoe shaped, concrete 

lined 

Design discharge 7.24 m 3 /sec 

Length 7 Km 

Adits 3 No.; 3.3 m D-shaped 

SURGE SHAFT 

Size & type 10m diameter 

Vertical Shaft height 50 m 

PRESSURE SHAFT 

Type Steel Lined; one, Inclined 

Diameter 1.5 m 

Length 1750 m 

Adits 2 Nos. of dia. 3.3m 

POWER HOUSE COMPLEX 

Type Under ground 

Tail water level at outlet 1853 m 

Turbine Axis Elevation 1854.63 M 

Type of Turbine Vertical axis Pelton 

Generating Capacity 2 X 35 MW 

Gross head 1110.37 m 

Rated Net head 1106.37 m 

Design Discharge 7.24 m 3 /sec 

Power House Size 72 m X 18m X 35m

TRT 

Diameter and type 3.3m dia, Horse-shoe 

Length 250 m 

Tail Water level at outlet 1853m 

SWITCH YARD 

Size 150M X 115M 

POWER GENERATION 

Installed Capacity 70MW (2 x 35MW) 

Annual Energy Generation in a 90% 

dependable year 

6 

317.41MU 

COST ESTIMATES & FIANANCIAL ASPECTS ( Rs. Crores) 

Civil Works 363.00 

Electro Mechanical Works 83.88 

Sub Total (Generation) 446.88 

Transmission Works 19.16 

Total (Hard Cost) 466.04 at June,2003 Price Level 

Interest During Construction 53.23 

Grand Total 519.27 

Tariff for first year per KWh 

a. with 12% free power 

b. without 12% free power 

Levellised Tariff per KWh 

a. with 12% free power 

b. without free power 

Rs. 3.61 

Rs. 3.17 

Rs. 2.93 

Rs. 2.58 

COSTRUCTION PERIOD 4 years 



1.2 STUDIES/INVESTIGATIONS UNDERTAKEN 

• Study of topographic maps and remote sensing imageries 

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• Reconnaissance of area for identifying probable alternative sites of projects 

components. 

• Study of regional geotechnical features/ seimotectonic aspects. 

• Geological appraisal of proposed project components. 

• Water availability design flood studies based on available meteorological/ 

hydrological data. 

• Conceptual layout and project planning. 

• Power potential studies. 

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

environmental impacts of the projects. 

• Study of existing infrastructure. 

• Cost benefit and economic evaluation. 

1.3 RESULTS OF STUDIES AND INVESTIGATIONS 

1.3.1 Geology 

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

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

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

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

powerhouse has been fixed after observing the competency of rock and its cover. 

1.3.2 Hydrology 

The river Ringpi drains a catchment area of about 126 sq.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 

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

8 



proportion and applying an overall reduction factor of 22 %. The computed inflow series 

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

assessed as 675 cumecs. 

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 

year 1976-77 corresponds to 90% dependable year. An installation of 70 MW comprising 

2 generating units of 35 MW 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) 317.41 

Annual Load Factor (%) 51.76 

Generation during Lean Flow Season (SeptII – JuneI) 

Energy Output (GWh) 170.58 

Load Factor (%) 37.19 

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

worked out at 317.41 GWh. 

A pondage of 0.567 mcum has been provided in the diversion dam, which would enable 

the station to operate as peaking station. The pondage is equivalent to 1521.92 MWh 

which sufficient to operate the station for 4 hours. 

1.3.4 Power Evacuation Aspects 

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

lines to a pooling station proposed near Teesta (II) HE Project to feed into the Grid which 

in turn connected to National Grid.

1.3.5 Environmental Aspects 

9 



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

construction of various components is about 149.00 ha. Most of the land falls under the 

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

plans have to be formulated for Catchment Area Treatment, compensatory afforestation 

and other environmental issues. These issues would be addressed during the investigation 

for DPR. 

1.3.6 Estimates Of The Cost 

The project is estimated to cost Rs.519.27 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 (Rs. Crores) is given below: 

Civil works : 363.00 

Electro Mechanical Works : 83.88 

Sub Total (Generation) : 446.88 

Transmission Works : 19.16 

Total (Hard Cost) : 466.04 

Interest During Construction : 53.23 

Grand Total 519.27 

1.4 FINANCIAL ASPECTS 

As indicated above, the Ringpi HE project with an estimated cost of Rs. 519.27crores 

(including IDC of Rs 53.23 crores) and design energy of 317.41GWh in a 90% 

dependable year is proposed to be completed in a period of 4 years. The tariff has been 

worked out considering a debt-equity ratio of 70:30, 16% return on equity, and 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. 3.61 /KWh & Rs. 2.93/KWh respectively.

1.3.8 Conclusion 

10 



The Ringpi HE project involves simple civil works and could be completed in 4 years. 

The project would afford design energy of 317.41 GWh in a 90% dependable year. The 

cost per MW installed capacity works out Rs.6.38 crores. The Preliminary Feasibility 

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

Investigation and preparation of DPR.



CHAPTER – II 

BACKGROUND INFORMATION

2.1 GENERAL INFORMATION 

2.1.1 Introduction 

CHAPTER –II 

BACKGROUND INFORMATION 

11 



Sikkim has elected to join the Indian Union to become 22 nd state in 1975; It is one of the 

most picturesque regions of Asia. The bowl like, mountain –girdled state in the eastern 

Himalayas bordered on the west by Nepal, on the north by Tibet, on the east by Bhutan 

and the south by Darjeeling district of the West Bengal, lies between 27 0 to 28 0 north 

latitude and 88 0 to 89 0 east longitudes. The Sikkim is the youngest and small hill state of 

India having an area of 7096 Sqkm. Sikkim is surrounded by important mountain ranges. 

The chola range of mountains on its east forms the watershed between it and Bhutan on 

one side and chumbi valley of Tibet on the other. The well-known singalila ridge is of the 

great Himalayas peaks. 

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

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

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

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

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

the East Sikkim’s historic past, mystic religion, sublime monasteries and age old rituals 

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

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

landscape is the mighty massif of Kanchendzonga 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 

joins the Teesta just near the border between Sikkim and West Bengal at Melli. Besides

12 



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 

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 chu on its right. Tolung 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 

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

Singtam and the river receives Rangpo Chu at Rangpo. After Rangpo, Teesta start

13 



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 The Project 

2.1.5.1 Background 

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

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

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

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

Electricity Authority, 162 hydroelectric power schemes with estimated installed capacity 

of 50,560MW were selected in 16 states for preparation of Pre Feasibility Reports. The 

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

coordination of CEA to NHPC Ltd, SJVN Ltd, NEEPCO, WAPCOS, KPCL, HPSEB and 

UJVN Ltd as consultancy work. NHPC was entrusted a total number of 43 schemes of

14 



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 Ringpi is one of the such scheme 

for PFR. 

2.1.5.2 About The Project 

The project is located on the river Ringpi chu in Dzongu area of North district of 

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

construction of a 40m high concrete dam, a 7.0 Km long headrace tunnel and an 

underground powerhouse with an installed capacity of 70 MW. The project shall generate 

317.41 MU of energy in a 90% dependable year. The dam site is located just d/s of the 

confluence of river Jhumthul Chu and Kishong Chu. The underground powerhouse is 

located u/s the dam of proposed Lingza HE project. The village Lingza, nearest to 

Power house site, is connected by a foot path of 6 Km from road end at Lingza which is 

17 km from Mangan. 

2.2 POWER SCENARIO AND EXISTING INSTALLATION 

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. 

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

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

Eastern regional power grids and the transmission system are being progressively inter- 

connected for efficient operation of these five regional grids. 

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

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

15 



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 Ringpi HE Project located in north Sikkim is envisaged to be connected to 

feed the power at a pooling station near Teesta(II) HE Project through one number 

220KV double circuit lines. 

2.2.2 Power Position in North Sikkim Region. 

The total installed capacity in Eastern Region is 16696.68 MW.Out of this only 2459.51 

MW is hydel installation. Thus the hydro thermal mix is 15:85, which is well below the 

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

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

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

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

Electric Power Survey, published by CEA. 

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

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

Eastern region is expected to face peak power and energy deficits during most of the 10 th 

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

16 



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 

Firm 

Capacity 

(MW) (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 

13 Robom Micro Hydel 2003-04 3.0 1.00 

I - Total Hydel Power 95.70 36.95 

II - Total Diesel Power 2.70 2.70 

Total Generation Capacity 98.40 39.65 

2.2.4 Load Demand & Power Position of Eastern Grid 

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

2.3 NECESSITY OF THE PROJECT AND RELATED ASPECTS 

17 



The need for Ringpi H.E.Project has been considered in the context of increasing demand 

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

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

scheme in Teesta basin in North Sikkim District, Sikkim. It will generate 317.41 MU in 

90% dependable year (1976-77) with 95% machine availability. 

The power generated at Ringpi HE Project (2 x 35MW) will be fed to a a pooling station 

near Teesta(II) HE Project through one number 220KV double circuit lines.

Region 

Eastern 

POWER SUPPLY POSITION OF EASTERN REGION 

WITHOUT RINGPI HE PROJECT (70 MW) 

10th Plan 11th Plan 

18 


Ringpi HE Project, (2 x 35 MW) 

Table 2.1 

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

1 2 3 4 5 6 7 8 9 10 

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

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

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

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

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

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

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

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

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

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

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

2003. 

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

4. Energy requirement & peak requirement for the year 2002-2003 onwards is based on the annual increments given at page -117 & 118 of "Sixteenth Electric 

Power Survey Of India". 

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

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



CHAPTER – III 

PROJECT AREA

CHAPTER –III 

PROJECT AREA 

3.1 DESCRIPTION OF PROJECT INCLUDING RIVER SYSTEM 

19 



Ringpi H.E. Project is situated in the Dzongu area of north district of Sikkim .The project 

envisages construction of 40 m high concrete gravity dam near the placeTolung and an 

under ground powerhouse near the place Ishana. The river water shall be diverted through 

a diversion tunnel of 400m length and 3.3 m dia for construction of dam. A headrace 

tunnel of 7.0 km length, 3.3m dia shall carry a discharge of 7.24 cumecs of water to the 

powerhouse. One number of desilting chamber of 50mX5mX7m size shall be constructed 

to separate the silt particles of 0.2mm size and above from the water. A surge shaft of 

10m dia and 50m deep along with one pressure shaft of 1.50m dia 1750 m length shall be 

constructed. A tailrace tunnel of 250m length and 3.3 m dia shall discharge the water 

back into the river. A Switchyard of 150Mx115m size shall also be constructed. The 

powerhouse shall have installed capacity of 70 MW to generate 317.41MU of energy in a 

90% dependable year. 

The river Ringpi Chu is the tributary of the Rangyong Chu originating in the glaciers of 

North Sikkim at an elevation of about 5000 m above mean sea level. The Jumthu Chu, 

Dawathang Chu, Kishong Chu, Pegor Chu and Zong Chu are the main tributary of Ringpi 

Chu. The Ringpi is the tributary of Rangyong Chu and meets Rangyong Chu upstream of 

the confluence of Ringyong Chu and Rangyong Chu. The other tributaries of the 

Rangyong Chu /Tolung Chu are Umram Chu, Passaram Chu, Rangyang Chu , Rangli 

Chu and Rahi 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 

20 



There is no human habitation in the vicinity of the proposed project site. Only a few 

villages under Sakyong Pentong Revenue Block fall within 10km radius of the project 

area. The human population as per the 1991 census up to different aerial distances from 

the project is given below. 

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

1. Population Nil 199 694 

2. Households Nil 49 145 

All 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. Yak herds, herdsmen and sheep grazers 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. 

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 sub-

21 



centre, 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. 

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 

22 



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. 

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. 

3.2.7 Hydropower Potential 

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

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

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

development in different stages. The details of hydropower potential identified is as 

under: 

Teesta Basin : 

According to the preliminary reconnaissance survey, the river could be harnessed under a 

cascade development for hydropower generation is six stages as under :

i) Teesta Stage-I 

23 



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. 

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.

Rangit Basin 

24 



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. 

No. 

Name of Scheme 

Installed 

Capacity 

(MW) 

Name of 

River 

District 

1. Dikchu 105 Bakchachu/Dikchu chu East 

2. Rongni 195 Rongni chu East 

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

25 



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 Chu/Sebokong 

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 

TOPOGRAPHICAL & 

GEO-TECHNICAL ASPECTS

CHAPTER-IV 

26 



TOPOGRAPHIC AND GEOTECHNICAL ASPECTS 


As a sequel to tap balance water potential of Sikkim, Central Electricity Authority 

proposed development of few schemes in a cascade manner. Accordingly, five run-of- 

the-river schemes have been proposed on Tolung Chhu and its left and right bank 

tributaries namely Ringpi Chhu and Rangyong Chhu respectively. These schemes are 

Ringpi and Lingza on Ringpi Chhu, left bank tributary and Rukel and Rangyong on 

Rangyong Chhu, right bank tributary. While another scheme namely Pannan has been 

proposed on Tolung Chhu downstream of confluence of Ringpi Chhu and Rangyong 

Chhu. The above schemes have been mentioned in order of their sequence on these nalas, 

while Ringpi and Rukel are upper most schemes, Lingza and Rangyong are downstream 

schemes on respective nalas and Pannan forms the downstream scheme. The Ringpi 

hydroelectric scheme, proposed by CEA envisages construction of a diversion structure 

across Ringpi Chhu, a 7.2 km long water conductor system in the right hill and a 

powerhouse near Ishana. The diversion structure shall be located downstream of 

confluence of Jumthul chhu and Kishong Chhu. Another scheme namely Lingza scheme 

has been proposed down stream of the powerhouse location of Ringpi scheme. 

As per the MOU between CEA and NHPC, preparation of prefeasibility report of Ringpi 

Scheme has been assigned to NHPC. Accordingly, a visit to assess the geological 

conditions in and around this scheme was undertaken in the month of October. As per the 

MOU report of GSI would form part of the appraisal, accordingly the report titled, 

“Geology of the Area Around Ringpi Hydroelectic Scheme” provided by GSI has been 

enclosed as Annexure-4.1. The present appraisal is based on field visit, study of 

topographic sheet 78A/6 and data from GSI report.

27 



4.2 REGIONAL TOPOGRAPHIC AND GEOTECHNICAL FEATURES 

River Teesta in Sikkim is a major river originating from Zemeu glaciers and generally 

flows in north-south direction, at a steeper gradient. The river is joined by several 

tributaries major amongst them being Yumthang Chu, Zemu Chu, Talung Chu, Dik Chu 

and Rangpo Chu, apart from others join the river. The river valleys in this region are u- 

shaped while, as the tributaries had developed deep gorges, which are bound by steep 

slopes. A thick vegetal cover occupies the hill slopes. These hill slopes are generally used 

for cultivation of cardamom. 

A brief of regional geological aspect of this area has been provided. The Eastern 

Himalaya covers the Sikkim-Darjeeling-Bhutan and Arunachal Pradesh sectors, 

extending from the eastern Nepal to western Burma. The higher Himalaya is a zone of 

crystalline rocks dividing two distinct lithofacies association in the south and the north. It 

is designated as the Axial belt. The northern zone comprising the Tethyan Palaeo- 

Mesozoic sedimentary sequence forms the Trans-Axial belt. To the south of the Axial 

belt occurs the Inner belt, comprising thrust sheets of Proterozoic-Upper Palaeozoic 

formations, while the foothill belt is represented by para-autochthonous Siwaliks. This 

scheme is valid for the entire Eastern Himalaya, upto the Lohit District of Arunachal 

Pradesh, where the geological picture does not conform to this general scheme. The 

stratigraphic sequence provided by GSI report on Ringpi Hydroelectric Scheme is 

brought out hereunder for the purpose of regional geological set up of the area. 

Group Lithology 

Gondwana 

Grits, pebble cum boulder beds and carbonaceous shale with 

occasional coal seams, pegmatite, quartzite (Tourmaline 

bearing)

Daling 

Chungthang 

Central Crystalline 

Gneissic Complex 

28 



• Interbedded quartzite and chlorite sericite phyllite / 

schist 

• Lingza Granite 

• Quartzite/ Biotite schist 

• Interbedded quartzite and garnetiferous quart biotite 

schist. 

• Calc-silicate rock/marble. 

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

Banded gneiss with augen gneiss and quart-biotite gneiss. 

Augen gneiss. 

Rock types belonging to Central Crystallines of Higher Himalaya occupy the area. 

Mainly high-grade gneisses with interbands of metasedimentaries, which comprise calc- 

silicate/ quartzites and high-grade schists. The metasedimentaries of the area occur as 

enclaves within high-grade gneisses. All the rock types have discordant intrusions of 

tourmaline bearing quartz veins and pegmatites. 

4.3 TOPOGRAPHIC AND GEOTECHNICAL ASPECTS OF COMPONENT 

STRUCTURES 

The region is thickly vegetated and falls within Tolung Reserve Forest. Jumthul Chhu an 

E-W flowing river originating from Jumthul Phuk glacier meets Kishong chhu (a north- 

south flowing nala) near Tolung giving rise to Ringpi Chhu. Ringi Chhu from this 

confluence (Photo-1) flows south-easterly and takes a sharp easterly bend, beyond which 

it flows southeasterly upto Tolung gompa. Further downstream it flows N-S and then 

takes a southwesterly swing until its confluence with Rangyong Chhu. No major nalas 

join Ringpi Chhu from the right bank while few nalas like Dwathang Chhu, Ludul 

Chhu,Pegar Chhu, Kongcha Chhu and Zong Chhu join it from the left bank. The area is 

bound by ridges, which generally trend NE-SW and follow the general strike of

29 



formations. The river flows in a steep gradient within cascades. Bed load in the nala 

comprises boulders, cobbles and pebbles in sandy/silty matrix. In general the valley 

slopes are thickly vegetated and occupied by a veneer of slope wash material, while rock 

formations are exposed as steep ridges. At places the hill slopes have been utilised for 

cultivation of cardamom. Entire area has a highly rugged terrain with elevation in vicinity 

varying from 2000 M to 6000 M. The area is approachable by a fair weather road upto 

Lingza beyond which a foot track reaches Tolung. 

4.3.1 Diversion Structure 

The proposed diversion structure is located approximately 100m downstream of 

confluence of Jumthul chhu and Kishong Chhu. Here, Ringpi flows southeasterly. At the 

proposed location the nala flows in a relatively wider valley ±200m wide, in a steeper 

gradient. The area was studied in detail to assess the proposed diversion location and any 

possible alternative alignment. During the study it was observed that in vicinity of Tolung 

Gompa the river has carved a wider valley with moderate to steep slopes. Further 

upstream the nala section was inaccessible. A pile of debris material (approximately 10m 

thick) comprising boulders, cobbles and pebbles in a silty/sandy matrix occupies the 

riverbed section. A terrace has been developed in the right bank. The left bank slopes are 

comparatively steeper while the right bank slopes are moderate and become steep 

towards higher elevation, which show rock exposure. The area is under a thick vegetal 

cover. The right bank slopes are essentially used for cardamom cultivation. The diversion 

structure shall be located within gneisses, which are hard compact and jointed. The 

gneisses are expected to provide good abutment conditions. The rock formations 

generally trend NE-SW dipping northwesterly however, occasional NW-SE trends have 

also been observed in the area. Warping in the rock formations has been noticed. During 

future course of investigations few drill holes are required to be drilled in order to probe 

the bedrock and overburden depths. However, abutment conditions shall be assessed 

during further course of investigations.

4.3.2 Water Conductor System 

30 



A 7.0 Km long water conductor system has been proposed in the right hill. A reconnoitre 

traverse from Ishana along the foot track in right bank of Ringpi was undertaken upto 

Tolung. The area is bound by steep ridges (Photo-2), which generally trend NE-SW. A 

pile of slope wash material occupies the slopes along the foot track. Nevertheless, a few 

intermittent reaches show rock exposures. Also rock exposures are observed towards 

higher elevations. From field visit it is observed that the water conductor system is 

crossed by several seasonal drainages. 

This water conductor system shall be housed within the rock types of gneisses with 

occasional bands of augen gneisses. The gneisses are strong to very strong and are 

expected to offer a good tunnelling media. The rock types trend NE-SW dipping 40-65º 

towards NW. Few intermittent stretches of calc silicate rocks/marble are also expected 

during tunnelling. However, these were not observed during the reconnoitre visit 

probably because of the overburden cover that occupies the slopes. Nevertheless, these 

have been reported in the area by GSI. Sufficient super incumbent cover is available 

above the tunnel. Fair to good tunnelling media with few pockets of poor rock mass, are 

expected during tunnelling. Prima-facie no major drainage appears to have deeply incised 

the proposed tunnel alignment. 

4.3.3 Powerhouse 

Ringpi Chhu has developed an easterly convex bend forming a loop and this lope has 

been utilised to locate the water conductor system the powerhouse. The powerhouse 

location was fixed keeping in view the FRL of Lingza Scheme. Accordingly, it was 

proposed to keep the tail water above the FRL of Lingza Scheme. A foot track runs along 

the proposed powerhouse location upto Tolung and the present appraisal is based on the 

observations made along this foot track. At the proposed powerhouse location the 

formations are exposed as steep rocky escarpments. A thick pile of slope wash material 

occupies the area along the foot track. In view of the topographic conditions an

31 



underground powerhouse has been contemplated. The powerhouse shall be housed within 

gneisses belonging to Central Crystallines of Higher Himalaya. These rock formations 

trend NE-SW dipping moderately towards NW. Fair to good rock media is expected 

during powerhouse excavation. Sufficient super incumbent cover is available above the 

proposed powerhouse cavern. The orientation of powerhouse shall be suitably aligned 

with respect to principal discontinuity. Towards the tailrace portion a thick pile of debris 

material is observed. 

4.4 SEISMICITY 

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

data of the region covering longitude 86-90 0 and 25-29 0 has been places at Annexure 4.2 

, which gives a list of earthquake events that have occurred within the region. The 

probable intensity of earthquake within seismic zone-IV corresponds to intensity VIII on 

Modified Mercali Scale. Notable earthquakes that have occurred close to this area are 

Cachar 1869 (M 7.5), Great Assam Earthquake 1897 (M 8.7), Dhubri 1930 (M 7.1), 

Bihar-Nepal Earthquake 1934 (M 8.3), Assam Earthquake 1950 (M 8.5) and Nepal-India 

border earthquake 1988 (M 6.4). The maximum intensity experienced in Sikkim region 

during Great Assam Earthquake, 1897 was VIII (MMI) and during Bihar-Nepal border 

earthquake, 1934 was VII (MMI). 

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

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

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

studies are proposed to design the component structures. 

4.5 GEO-PHYSICAL SURVEY 

The dam site is located in remote area, where proper approaches are not available due 

which Geo-Physical survey could not be conducted in such a small time schedule. While,

32 



the powerhouse site is having sufficient rock exposures and hence the Geophysical 

survey was not done. 

4.6 CONSTRUCTION MATERIAL SURVEY 

The riverbed is full of boulders, but it is shall not be sufficient to met the construction 

materials requirement. The area is bounded by steep rocky ridges and the quarries for 

construction material can be developed. 

4.7 RECOMMENDATIONS 

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

explorations to assess overburden thickness and its amenability for construction of 

various structures. 

• Detailed geological mapping of the project components need to be carried out. 

• The survey of the quarries may be done to assess the quantities of construction 

materials and testing to assessed their suitability.



CHAPTER – V 

HYDROLOGY

CHAPTER –V 

HYDROLOGY 

34 



5.1 GENERAL 

Ringpi H E Project is a run of the river scheme, proposed on Ringpi Chu, one of the 

tributaries of Rangyong Chu/Tolung Chu, which in turn is a major right bank tributary of 

river Teesta. The project envisages construction of a 30 m high diversion structure above 

river bed level, on Ringpi Chu with a gross storage capacity of about 1.856 Mcum and 

area of submergence as 12.7 Ha at FRL 2966 m. 

The hydrological investigations and analysis have been carried out for Ringpi Project 

with a view to: 

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

average 10-daily discharges for the project site. 

• Establish the spillway design flood 

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

levels including FRL and MDDL. 

• Reservoir sedimentation. 

5.2 RIVER SYSTEM AND BASIN CHARACTERISTICS 

Ringpi Chu is one of the major tributary of Talung chu river which in turn is one of the 

major tributary of river Teesta and meets Teesta at Singhik on its right bank. Ringpi Chu 

intercepts a substantial catchment area and is formed by two streams originating at high 

elevations having snow catchment in their upper reaches. The river has substantial flows 

and a steep gradient. The present Ringpi H.E project is proposed just downstream of the 

confluence of Jhumthul Chu and Kishong Chu. The river meets Rangyong Chu/Tolung 

Chu near village Lingza. 

Tolung Chu originates from the Tolung glacier, which is a part of the Kanchanjunga 

range. The river is known by different names in different reaches. In the upper reach it is

35 



known as Rukel Chu, further downstream it is called Rangyong Chu and in the lower 

reaches it is known as Tolung Chu. Tolung Chu is fed by a number of tributaries having 

large drainage areas at their confluence. 

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 

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. It joins Teesta river almost perpendicularly. 

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

of approximately 4000m. 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 Ringpi H.E project lies 

upstream of Lingza H.E project. 

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

36 



hydro power generation. The cascade development proposed at that stage consisted of 

power generation in six stages on river Teesta. Out of these schemes, NHPC had 

submitted a DPR for Teesta H.E project, Stage-III in 1990. The diversion structure for 

Teesta-III was proposed to be constructed at Chungthang, which lies downstream of the 

confluence of Lachen Chu and Lachung Chu. Another project under Teesta Basin 

development, which is under execution by NHPC, is Teesta Stage-V having an installed 

capacity of 510 MW, where a diversion structure is being built at Dikchu, about 2 Km 

downstream of confluence of Dikchu with Teesta. About 70km downstream of Teesta-V, 

NHPC has been entrusted two projects namely, Teesta Low Dam H.E projects, Stage-III 

& IV, having an installed capacity of 132 MW and 160 MW respectively. The proposed 

Ringpi H.E project on Ringpi Chu, lies downstream of Chungthang on Teesta river, 

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

5.2.2 Catchment Area 

The catchment area of the proposed scheme lies between Longitude 88o18′00” E to 

88o31′00” E and Latitude 27o37′00” N to 27o45’00” N. The catchment area upto the 

proposed dam site is about 126 Sq.km. The catchment is both snowfed as well as rainfed. 

The proposed diversion structure lies at Longitude 88o26′39” E and latitude 27o40′35” 

N. The catchment Plan is shown in Plate-5.1. A map showing various proposed projects 

in Tolung Chu basin is enclosed as Plate-5.2. The catchment plan has been prepared from 

1:50000, Survey of India toposheets. The entire catchment is covered in toposheets no. 

78A/6, and 78A/2. The EL4600m is assumed to be snowline thus making rainfed and 

snowfed areas as 63 Sq.km. 

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 

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

duration. The maximum and minimum temperature varies from 390 C in summer to 60 C

37 



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

humidity observations are being made in the basin at Dikchu site where Teesta-V H.E 

project is being constructed by NHPC and at TLDP-III and TLDP-IV sites, as a part of 

cascade development on Teesta river. The monthly maximum, minimum temperatutre 

and relative humidity at Dikchu from Jan 1998 to Dec 2001 is enclosed as Annexure-5.1 

and annual maximum and minimum temperature from 1998 to 2001 is given in 

Table 5-1. 

Month & Year 

TABLE 5-1 

Temperature And Humidity Data At Dikchu 

Maximum 

Temp o C 

Minimum Temp 

o C 

Max. Relative 

Humidity % 

Min. 

Relative 

Humidity 

1998 38.0 7.0 99.0 89.0 

1999 39.0 6.0 99.0 90.0 

2000 39.0 7.0 97.0 85.0 

2001 31.0 11.0 97.0 90.0 

Overall 39.0 6.0 99.0 85.0 

5.2.4 Precipitation Characterstics 

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

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

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

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

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 

%

38 



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

39 



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

proposed scheme comprises the upper and middle portions only. 

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

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

Out of the 53 rain storms 40 were of 1 day, 11 were of 2 day and only 2 were of 3-day 

duration. It was concluded that 1-day duration storm are more frequent, a fact that 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, with NHPC, is shown in Table 5-3.

S.No Name of 

station 

40 

Table 5-3 



Data Availability Status Of Raingauge Stations upto Teesta-V 

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 

1992 to 1997, 2001 to Feb 03 

1991 to 1997 

11. Pelling May 93 to Dec 96 

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

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

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

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

at present. None of the above rainfall stations lie in the catchment of the proposed project 

so this data has not been used in the hydrological analysis.

5.3 WATER AVAILABILITY STUDY 

5.3.1 Stream flow and River gauges 

41 



Since Teesta River offers ideal conditions for cascade development of hydroelectric 

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

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

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

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

no G&D data is available on Ringpi Chu, at or near the proposed dam site of Ringpi H.E 

project. The various G&D sites and period of data availability in Teesta Basin is shown in 

Table 5-4. 

Table 5-4 

Data Availability Status Of G&D Sites In Teesta Basin 

S.No Name of site River Period of 

1. Chunthang (before 

confluence of 

Lachung & 

2. Lachung Chungthang Chu) (after 

3. 

confluence of 

Lachung & 

Lachung Chu) 

availabilty 

Catchment 

Area 

(Sq.km) 

Lachen Chu Jan 75 to Aug 85 1919.25 

Teesta Jan 75 to Jun 86 2786.8 

Third Mile Tolung Chu Jan 75 to Aug 85, 

Apr 90 to Apr 98 

731.25 

4. Lachung Lachung Chu May 76 to Aug 85 634.50 

5. Chuba Yumthang Chu Jan 78 to Aug 85 355.5

42 



6. Zema Zema Chu 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 (near 

Rangit damsite) 

Teesta Jan 84 to Oct 91, 

Nov91 to Oct96, Jan 

97 to Oct 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 

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 

. 

5.3.2 Present Study 

979 

8065 

No daily G&D data was available on Ringpi Chu, on which the present project is 

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

been computed based on the following methodologies: 

(i) Based on observed discharges at Tolung Chu (Jan 75 to Aug 85, Apr 90 to Apr 

98) 

The proposed diversion structure for Ringpi project is located on Ringpi Chu, which is a 

tributary of Tolung Chu. Daily G&D data is available on Tolung Chu from Jan 75 to Aug 

85 and Apr 90 to Apr 98. The G&D site on Tolung Chu has 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 0.108.

43 



Rainfed area at both the sites has been used in obtaining the reduction factor. The rainfed 

area upto G&D site on Tolung Chu is 583 Sq.km and that upto Rinpi H.E project is 63 

Sq.km. 

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

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

has been converted at proposed site using catchment area reduction (catchment reduction 

factor – 0.076). Rainfed area upto Chungthang site is 834 Sq.km. Thus a series for the 

period 1976 to 1984 has been obtained. 

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

G&D data observed at Lachen has been converted at proposed site using catchment area 

reduction (catchment reduction factor – 0.22). Rainfed area upto Lachen G&D site is 574 

Sq.km. 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) Based on discharge series of Teesta-V H.E project (1976-Feb 2003) 

The 10-daily series at Teesta-V H.E project for the period 1976- Feb 2003 has been 

converted at proposed damsite using catchment area reduction (catchment reduction 

factor – 0.031). Rainfed catchment area upto Teesta-V H.E project is 2020 Sq.km. The 

series from 1976-1996 is the approved series by CWC for Teesa-V and from 1997 to Feb 

2003 is the observed data at Dikchu where observations are being taken by NHPC. 

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

compared. The plot showing this comparison of average 10-daily discharge at Ringpi 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. Rainfall-runoff relationship could not be established for

44 



the observed data on Tolung Chu as no rainfall data in the catchment of the proposed 

project was available. Hence, for pre-feasibility study, the series so obtained on the basis 

of Tolung Chu data cannot be adopted as such, it comparatively being on a higher side. 

Average 10-daily obtained from other three approaches are almost comparable so need 

for further statistical checks is not felt necessary. For pre-feasibility stage, the average 

10-daily obtained from G&D data at Lachen is recommended for Ringpi H.E project. 

Though the catchment area reduction factor is very low for all three series, this series has 

been adopted as Lachen G&D site has a smaller catchment area as compared to 

Chungthang and Teesta-V. After estabilishing G&D site near proposed dam axis and 

obtaining more rainfall data in the catchment, detailed water availability study need be 

done during feasibility/DPR stage. The final 10-daily series at Ringpi is enclosed as 

Annexure-5.2. 

5.4 RESERVOIR ELEVATION AREA CAPACITY CURVE 

The reservoir elevation-area-capacity curve for Ringpi H.E project has been prepared 

from 1:50000 Survey of India toposheets. The contours are available at an interval of 

40m with the minimum bed level at proposed dam site being 2940m. The area enclosed 

within the contours has been found using Autocad. Area has been found from elevation 

2960m to 3120m at an interval of 40m. The volume between any two elevations is 

calculated using the conical formula : 

V = H/3 * (A1+A2+√A1A2) 

Where 

V = Volume between two contours 

H = Contour interval 

A1 = Area at level of first contour 

A2 = Area at level of second contour 

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

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

45 



receiving toposheets in scale of 1:25000. The gross capacity at FRL 2966 m is 1.856 

Mcum and submergence area is 12.7 Ha. 

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: 

(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. 

Therefore, Q = 14 x 126 3/4 

A = Catchment area in sq.km 

= 527 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*126) (0.925-1/14log(126))

= 1252 cumec 

46 



(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. Ringpi H.E project is located 

on Ringpi Chu river which is a tributary of Tolung Chu, which in turn is a major tributary 

of Teesta river and both the catchments can be assumed to be hydrologically and hydro- 

meteorologically similar. Therefore, it seems logical to transpose the design flood value 

of Teesta-III to proposed dam at Ringpi. This transposition has been done by Dicken’s 

formula using a conversion factor of 0.099. 

Q 1 = CA 1 n 

Q 2 = CA 2 n 

Where, A 1 = Catchment area of Ringpi project 

A 2 = Catchment area of Teesta-III project 

Q 1 = Design Flood for Ringpi project 

Q 2 = Design Flood for Teesta-III project 

C = Dicken’s constant 

n= 0.75 

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

= 448 cumec 

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

formula 

The design flood for Ringpi 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 Ringpi project, having a catchment area of 126 

Sq.km comes out to be 0.071.

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

= 672 cumec 

47 



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

Table 5-5. 

TABLE 5- 5 

Comparison of Various Flood Values 

SL .No Method used Design Flood 

(cumec) 

1. Dickens Formula 527 

2. Ali Nawaz Jung Formula 1252 

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. 

For pre-feasibility stage study, a design flood of 675 cumec has been recommended at 

proposed dam site. 

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

deterministic approach using unit hydrograph technique and probabilistic approach using 

flood frequency analysis in feasibility stage. Also, design flood has been worked out on 

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

unit hydrograph technique and flood frequency analysis. 

5.6 SEDIMENTATION 

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

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

448 

672

48 



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

adopted for Ringpi H.E project too. 

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

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

using a suitable method. 

5.7 RECOMMENDATIONS FOR FUTURE STUDIES 

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

1. Proper raingauge network along with Gauge-discharge-sediment observation sites 

on Ringpi river need be established before taking up preparation of feasibility 

report /DPR. 

2. After establishing gauge and discharge site on Ringpi river with proper raingauge 

network in the basin, detailed water availability study need be conducted in 

feasibility/DPR stage. 

3. The reservoir elevation area capacity curve need be revised after availability of 

reservoir cross-sections or 1:25000 scale contour maps in feasibility/DPR stage 

study. 

4. On availability of more data/information, design flood need be estimated by 

deterministic approach using unit hydrograph technique and probabilistic 

approach using flood frequency analysis in feasibility/DPR stage. 

5. Detailed reservoir sedimentation study need be done during feasibility/DPR 

stage with observed data on Ringpi river at the proposed dam site using a suitable 

method.

49 


Ringpi HE Project, (2x 35 MW) 

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 2.47 2.29 2.68 3.63 4.30 6.83 12.36 10.45 11.10 3.96 3.14 1.89 

1976 II 2.36 2.25 2.87 3.98 3.40 13.33 11.78 11.39 6.40 3.13 2.60 1.62 5.27 

III 2.22 2.31 3.09 4.69 4.77 9.67 8.97 12.18 4.67 3.16 2.32 1.49 

I 1.33 2.23 1.23 2.37 2.58 7.34 10.83 12.46 8.55 7.12 3.72 2.31 

1977 II 1.27 2.17 1.76 2.22 3.19 13.03 12.74 10.49 6.99 4.49 3.39 2.45 5.25 

III 1.21 1.30 1.63 2.36 4.55 9.48 15.26 12.24 5.83 3.58 2.56 2.77 

I 1.90 1.76 1.60 2.29 3.95 10.85 12.64 15.47 8.14 7.67 4.08 2.89 

1978 II 1.70 1.72 1.72 2.93 8.10 11.38 13.55 13.08 10.60 5.98 3.04 2.45 6.20 

III 1.74 1.58 1.90 3.47 9.46 14.39 13.07 9.82 7.97 5.10 3.00 2.20 

I 2.03 1.68 1.87 3.55 6.65 7.73 13.77 13.64 11.23 11.98 6.11 4.46 

1979 II 1.87 1.67 1.96 3.53 8.48 9.25 13.17 10.77 9.80 8.18 4.98 3.68 6.67 

III 1.84 1.82 2.41 4.43 6.49 13.26 14.76 11.42 7.19 6.13 4.69 3.54 

I 3.34 3.06 3.51 5.46 7.61 10.64 16.77 18.17 15.88 7.88 5.33 4.15 

1980 II 3.21 3.20 3.60 7.00 6.51 14.16 17.17 19.96 12.45 6.77 4.85 3.77 8.49 

III 3.18 3.41 4.86 7.98 6.94 15.85 17.99 16.62 10.08 6.31 4.47 3.43 

I 3.30 2.84 3.49 4.37 8.01 9.24 19.17 15.07 14.80 9.27 6.39 3.88 

1981 II 3.09 2.92 3.70 5.54 8.65 11.05 16.43 15.91 12.69 8.58 5.10 3.49 8.15 

III 3.05 3.53 4.37 6.53 8.39 15.00 15.46 15.46 10.11 7.50 4.22 2.73 

I 2.51 2.73 2.87 4.82 6.68 12.88 13.77 12.22 10.45 7.02 4.45 3.32 

1982 II 2.79 2.84 3.22 4.81 7.51 14.18 15.42 11.57 15.11 5.89 3.88 3.06 7.38 

III 2.75 2.76 3.83 5.33 7.29 15.68 18.19 13.58 9.91 5.68 3.75 2.90 

I 2.87 1.63 2.42 4.12 6.79 13.61 21.11 14.59 14.52 13.24 7.28 4.59 

1983 II 2.56 1.62 3.11 3.37 8.14 13.21 17.96 15.47 16.33 13.06 6.68 4.31 9.05 

III 1.79 2.25 2.80 4.22 10.83 18.43 17.82 18.07 18.84 8.90 5.51 3.86

51 




I 3.44 2.91 6.40 7.39 8.94 19.29 23.98 22.93 24.79 15.81 11.51 5.67 

1984 II 3.39 3.02 7.15 7.88 13.07 23.20 24.06 23.00 23.66 20.05 9.95 5.58 13.21 

III 3.02 2.90 7.03 7.88 18.56 20.83 25.43 24.07 18.77 15.45 8.84 5.60 

I 5.65 5.08 7.13 8.66 8.88 9.21 25.70 22.79 12.00 8.26 4.84 3.17 

1985 II 5.36 4.64 7.73 10.45 10.31 11.50 33.53 24.03 11.46 7.24 4.21 2.87 11.44 

III 4.64 5.62 7.20 12.34 14.36 32.59 28.20 29.43 9.85 6.20 3.84 2.70 

I 2.50 2.38 2.99 3.29 4.47 6.09 13.25 13.22 11.04 9.00 4.83 3.32 

1986 II 2.49 2.45 3.26 4.25 4.75 10.33 16.56 11.36 13.72 6.73 4.30 3.06 6.75 

III 2.36 2.81 3.34 4.77 5.01 15.30 14.89 12.58 11.17 5.26 3.71 2.26 

I 1.97 1.65 1.67 4.55 4.75 10.29 14.38 14.56 19.10 8.70 4.50 2.27 

1987 II 1.86 1.63 1.99 3.18 5.28 14.94 13.75 15.88 10.22 6.48 2.74 2.08 6.87 

III 1.74 1.79 2.50 4.20 6.20 12.54 15.38 10.62 14.01 5.54 2.41 1.90 

I 1.86 1.80 2.17 3.78 5.08 8.13 20.03 17.21 11.44 7.29 3.21 2.56 

1988 II 1.86 1.88 3.22 4.27 7.61 11.76 15.73 15.79 7.72 4.83 2.89 2.43 7.18 

III 1.83 2.09 3.31 4.97 10.08 12.89 17.34 23.96 8.63 3.89 2.70 2.30 

I 1.41 1.51 1.67 1.82 4.58 10.24 18.27 14.52 10.83 7.70 3.31 2.13 

1989 II 1.37 1.38 1.70 2.18 4.73 16.97 17.97 11.39 9.81 6.55 2.69 1.85 6.67 

III 1.36 1.47 1.75 2.61 11.53 17.94 16.73 11.17 9.75 5.33 2.45 1.62 

I 1.48 1.22 1.01 0.87 2.62 11.23 14.13 13.13 11.36 6.35 3.26 1.86 

1990 II 1.37 1.15 0.83 1.43 4.62 10.97 18.02 13.34 10.88 6.47 2.43 1.54 5.78 

III 1.24 1.11 0.84 1.78 5.32 12.82 15.42 11.84 7.58 5.32 2.03 1.32 

I 1.34 1.26 1.29 4.08 4.13 5.96 9.88 12.03 11.54 7.54 4.07 2.31 

1991 II 1.32 1.20 1.47 2.32 5.03 9.41 9.63 13.86 12.19 5.98 3.60 1.77 5.40 

III 1.30 1.21 1.55 2.46 5.57 8.65 10.49 11.46 9.44 4.91 2.74 1.56 

I 1.42 1.27 1.26 1.54 1.94 2.50 5.94 7.47 7.15 4.40 1.98 1.59 

1992 II 1.18 1.22 1.27 2.16 2.25 3.57 6.01 7.50 7.04 3.16 1.76 1.38 3.28 

III 1.20 1.17 1.30 1.97 2.26 6.91 6.82 8.15 5.83 2.69 1.61 1.27 

I 1.29 1.18 1.99 2.11 3.50 4.10 14.10 18.54 17.71 12.53 6.61 5.21 

1993 II 1.30 1.26 1.98 2.30 3.15 5.23 14.09 17.57 14.92 9.30 5.83 4.79 7.01 

III 1.22 1.21 2.07 2.76 3.19 6.73 16.53 16.83 14.10 7.97 5.34 3.94

52 




I 3.71 3.44 3.25 3.60 4.63 8.48 11.15 11.07 9.86 6.68 4.47 2.97 

1994 II 3.45 3.29 2.93 4.51 4.78 11.23 11.82 10.81 9.88 5.94 3.69 2.72 6.26 

III 3.49 3.53 3.71 4.14 5.88 13.04 12.04 11.63 8.54 5.43 3.08 2.57 

I 2.44 2.41 2.20 2.81 7.41 12.83 17.64 12.43 10.05 6.40 3.16 2.72 

1995 II 2.46 2.41 2.08 3.48 11.44 13.72 14.80 12.54 9.00 6.23 3.61 2.42 6.84 

III 2.43 2.42 2.87 5.08 11.05 13.90 11.38 11.14 8.66 4.86 3.63 2.25 

I 1.94 2.11 2.09 2.37 6.24 7.10 11.93 10.93 10.25 7.48 5.58 3.17 

1996 II 1.93 1.88 2.41 2.30 5.47 6.01 12.84 10.19 9.78 6.86 5.18 2.87 5.91 

III 2.04 2.05 2.57 5.12 7.57 10.73 11.43 10.27 8.51 6.13 4.61 2.70 

I 2.99 2.88 2.91 3.19 3.81 5.00 10.98 9.10 7.80 5.62 2.67 2.01 

1997 II 2.84 2.87 3.05 3.17 4.38 7.13 9.50 11.10 8.83 3.69 2.46 1.96 5.68 

III 2.36 2.25 2.87 3.98 6.48 11.50 15.29 13.89 11.46 7.24 4.21 2.87 

I 2.47 2.29 2.68 3.63 5.43 9.21 14.95 14.05 12.00 8.26 4.84 3.17 

AVG II 2.36 2.25 2.87 3.98 6.48 11.50 15.29 13.89 11.46 7.24 4.21 2.87 7.05 

III 2.22 2.31 3.09 4.69 7.92 14.07 15.33 14.17 9.85 6.20 3.84 2.70 

Note : 1) All discharge data is in cumec. 

2) Total no. of years -22



CHAPTER – VI 

CONCEPTUAL LAYOUT & 

PLANNING


CHPAPER-VI 

CONCEPTUAL PLANNING AND LAYOUT 

57 



The Ringpi H.E. project is located in the North district of Sikkim state. It is a run of the 

river scheme proposed to harness hydel potential of the Ringpi Chu, a Sub-tributary of 

river Teesta. The available gross head of 1113 m is proposed to be utilised for generating 

70 MW of Power. One small reservoir of adequate capacity has been provided as 

operating pool to meet diurnal peaking load demands. 

6.2 PROJECT COMPONENTS 

• 3.3 m diameter, 400 m long Diversion Tunnel with u/s & d/s coffer dam. 

• Concrete Dam 40 m high above deepest level & 300m long with a central 

spillway. 

• Power Intake Structure leading to 1 Nos. 3.5 m dia D-shaped intake tunnel. 

• One No. Underground Desilting Chambers of size 50m (L) X 5 m (W) X 7.5 m 

(H). 

• One 3.3m diameter horseshoe shaped concrete lined and 7.0 kms long Head Race 

Tunnel with three adits. 

• One 10 m diameter & approx. 50 m high semi-Underground Surge Shaft. 

• One circular inclined Pressure Shaft of 1.5m diameter, 1750 m long bifurcating to 

feed two Pelton wheel turbines. 

• Underground Power House of size 72m x 18m x 35m consisting of 2 Pelton units 

of 35 MW each. 

• One no.3.3m diameter Horseshoe shaped tailrace tunnel of about 250 m length. 

The conceptual planning and lay-out of project components have been worked out based 

on S.O.I topo sheets of 1:50000 scale (topo-sheet no. 78A/6) with contour intervals 40 m.

6.2.1 Conceptual Layout 

58 



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

and construction material at various locations of the diversion structure near the one 

suggested earlier by CEA. The location of the powerhouse has been fixed keeping the 

tailrace outlet level at EL 1853 m. This level has been kept 3m above FRL of the 

proposed Lingza H E Project. 

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

geology, and maximum water availability at the prospective site. The location of major 

components of the project, riverbed level 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 considered during the preparation of this report. The upcoming hydroelectric 

projects on Teesta River of which Ringpi Chu is a sub-tributary have been taken into 

consideration in the conceptual planning of the project. 

The layout plan of the project and brief write up as envisaged by CEA have been 

enclosed as plate-1 and annexure 6.1 respectively. The cascade development schemes on 

the Teesta River as prepared by CEA is enclosed as plate-2 and of Tolung River basin as 

plate 3 and 4. 

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

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

discussed with CEA for vetting during Dec’03. The minutes of meeting with CEA have 

been enclosed as Annexure-6.2. 

6.2.2 Dam and River diversion works 

Construction of a 40m high concrete Dam has been proposed keeping in view the 

topography, geology and availability of construction material. The reservoir capacity 

formed by construction of dam has a gross storage pre-sedimentation capacity of 1.856

59 



M.cum and live storage capacity of 0.567 M cum. After sedimentation, the reservoir is 

likely to have an adequate live storage capacity adequate for running the power station at 

full capacity for 4 hours in a day during the period of lean flows. 

Width of the valley at dam site varies from 50 m at riverbed level to 300 m at EL 2970 m, 

which is suitable for a concrete dam. Average bed level at Dam site is EL 2940 m. FRL is 

proposed to be fixed at EL 2966 and MDDL at El.2963 m. keeping in view the pondage 

requirement and inflow of water in Ringpi chu during lean period. The top of the dam has 

been proposed to be kept at EL 2970 m and foundation of the dam at EL 2930 m after 

removal of approx. 10.0 m thick overburden. The availability of construction material for 

the dam, cofferdam and its suitability has been discussed elsewhere in the report. 

The overflow section of this dam is 30 m long and Non –overflow section is 270 m 

consisting 126 m on right abutment and 144 m on left abutment. The spillway has three 

bays each of size 4 m X 7 m with 3.0 m wide piers. The spillway is designed to pass a 

probable maximum flood of 675 cumecs with one gate inoperative. The crest of spillway 

has been kept at EL2950 m. The low-level orifice type spillway has been provided to 

flush out the sediment accumulated in the reservoir to maintain the live storage capacity 

of the reservoir. The top width of non-overflow has been fixed as 8 m. The d/s slope of 

the Non-overflow section has been proposed as 0.8H: 1V and u/s slope as 0.1H: 1V. The 

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

One no. Concrete lined 3.3 m dia 400 m long diversion tunnel has been proposed on the 

left bank of the river to divert a flood of approx. 100 cumecs The design diversion 

discharge has been decided based on the experience of various ongoing NHPC projects in 

Teesta valley. This data shall however needs to be firmed up during the preparation of 

detailed project report with the availability of more hydrological data & experience 

gained in the basin e.g.: during the construction of Teesta-V project. In order to divert the

60 



river during construction of the dam, an u/s cofferdam of approx. height 15m and d/s 

cofferdam of 8-m height is proposed. 

6.2.3 Power Intake & Desilting Chambers 

The proposed power intake is on the right bank of the Ringpi chu and consists of an 

intake and a D-shaped intake tunnel of dia 3 m. The intake structure is designed to pass 

8.68 cumecs, which includes flushing discharge i.e. about 20% of turbine discharge (7.24 

cumecs). The invert level of the intake structure has been kept at 5 m higher than the 

spillway crest to check the sediments entry in the water conductor system. The intake 

structure shall be provided with the trash racks to prevent the entry of trash into the water 

conductor system. The gross area of the trash racks shall be determined to give a velocity 

of not more than 1.5m/s. A mechanical raking machine operated from El.2970 m shall 

clean the racks. One vertical lit gate shall be provided for maintenance purposes along 

with a service gate for isolation of water conductor system. 

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

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

larger than 0.2 mm-particle size. A 5 m wide Dufour type Desilting chambers with height 

7.5 m shall be provided to remove 90% of particles having size greater than or equal to 

0.2 mm. The size of desilting chamber has been arrived at to keep the flow through 

velocity to less than 0.25 m/s.The chamber has 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 the chamber runs along the length and a silt flushing 

tunnel of size 075 m x 1.5 m D-shaped and 500 m length which will discharge the 

sediment back into the river d/s of the dam. Thus practically silt free water will be led 

into the headrace tunnel. The requirement of desilting chambers is being foreseen, on the 

lines of Teesta-V project, which is located d/s of this project. The size, alignment, 

orientation of the chambers can be optimized after more geological, topo-graphical and 

sedimentation data become available.

6.2.4 Head Race Tunnel, Surge Shaft, and Pressure Shaft 

61 



The proposed 3.3 m diameter concrete lined horseshoe shaped headrace tunnel of 7.0 

km length, and having a slope of 1 in 250 is designed to carry a design discharge of 7.24 

cumec. The diameter of the headrace tunnel has been fixed from the minimum working 

area requirements. The Invert level of headrace tunnel is fixed at EL. 2955 m near intake. 

The rock cover above headrace tunnel generally varies from +100 m to +800 m. The low 

cover reaches are confined to prominent nalla crossings. Three nos. construction Adits of 

3.3m dia are proposed to facilitate excavation of headrace tunnel within the scheduled 

completion time. The length of tunnel between 350 m long adit-1 & 700 m long adit-2 is 

2.5 Km and the length of tunnel between 700 m long adit-2 & 500 m long adit-3 is 4 Km. 

The location of the adits and portals are indicative and the actual lengths may vary. The 

tunnel is proposed to be concrete lined with 250 mm thick plain M-20 concrete. The rock 

support treatment shall consist of grouted rock bolts/anchors and shotcrete with or 

without wire mesh as per geological conditions encountered. In rock class of IV & V 

steel ribs supports is envisaged. 

A vertical, restricted orifice type semi-underground surge shaft of 10 m finished dia and 

about 50 m height has been proposed with its top opening into a platform at elevation EL 

+2975 m. Surge shaft is proposed to be concrete lined with 0.75 m thick R.C.C. Its 

bottom is kept at EL 2925 m at the HRT and surge shaft junction. The transient studies 

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

operation conditions, and optimize the surge shaft dimension. 

One no. Steel lined inclined circular Pressure Shaft of 1.5m diameter and 1750m length 

takes off from the surge shaft which further bifurcates to feed water to two units of Pelton 

turbines each of 35 MW.

6.2.5 Power House Complex & Tail Race Channel 

62 



The underground Power House is located on the Right bank of Ringpi Chu u/s of Lingza 

dam. It will have an installed capacity of 70 MW (2 generating units of 35 MW each). 

The support system shall comprise of rock bolts and shotcrete. The centerline of the 

turbines is proposed at EL 1854.63 m. One number electrically operated overhead 

traveling crane (E.O.T) shall be provided for handling the electrical and mechanical 

equipment. A lift shall be provided near the service bay for approaching the lower parts 

of power house.The overall dimensions of the Power House are 72 m x 18 m x 35m. A 

Control block area shall be located on one end of machine hall. The transformer cavern 

cum gate shaft is proposed 30m d/s of powerhouse cavern. 

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

cables to a surface switchyard. The Switchyard measuring approx. 150 m x 115 m shall 

be formed in cutting/filling. 

Water from the turbines is discharged in Lingza reservoir through two concrete lined 

tailrace tunnels, which merge into a single tailrace tunnel of diameter 3.3 m. This tunnel 

is 3.3 m diameter horseshoe and about 250m long with invert at EL.1852 at tailrace 

outlet. The tailrace outlet level has been kept at El. 1852 m in conformity with the FRL of 

proposed Lingza H E Project. 

6.3 FURTHER STUDIES 

6.3.1 Topographical Studies 

1. Topographical contour Survey of the dam area and Power House area in 1:5000 

scales with 5m contour intervals. 

2. Survey in 1:1000 scale for locating the adits of the HRT. 

3. The riverbed survey including the cross sections at Dam axis and tailrace outlet shall 

be undertaken to firm up the power potential of the project.

6.3.2 Geological and Geo-technical investigations 

63 



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. 

6.3.3 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. 

3. Hydraulic model studies for reservoir and Dam spillway shall be required for the 

confirmation of design parameters. 

4. Structural design of various components of the project. 

5. Sedimentation analysis for working out the post sedimentation storage capacity of the 

reservoir. 

6. Alternative studies for location, type and layout of main components based on 

detailed topographical and geological studies.

6.4 HYDRO- MECHENICAL EQUIPMENT 

6.4.1 Diversion Tunnel Gate And Hoist 

64 



For the diversion of water during construction stage, one number horseshoe shaped 

diversion tunnel of 3.3m diameter has been proposed. 

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

number fixed wheel type gate will be provided at the inlet of the tunnel. The gate shall be 

operated by means of electrically operated rope drum hoist located on the hoist platform 

installed over the trestle above deck level. The gate is meant for one time closure, just 

before plugging of the tunnel. Height of the cofferdam is 15m and gate is to be designed 

for operation against water height corresponding to 19.0m. 

6.4.2 Spillway Radial Gates, Hoists, Spillway Stoplogs And Gantry Crane 

Three 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 having a provision of 

25% pushing force (one on each end of the gate). 

One trolley mounted mobile gasoline engines operated power pack capable of operating 

two gates at 25% of the normal rated speed are envisaged for emergency operation of 

spillway radial gates. 

One portable oil filter unit for filtration, dehydration and degasification of hydraulic oil is 

also being provided. 

One set of spillway stoplogs has been envisaged to cater to the maintenance requirement 

of three nos. spillway radial gates. The spillway stoplogs shall be lowered / raised under 

balanced head condition by means of a suitable capacity of Gantry Crane.

6.4.3 Instrument And Remote Control 

65 



Gates shall be provided with PLC based remote control system for Control and operation 

of gates and automatic control of the reservoir level. 

6.4.4 Diesel Generating Set 

One diesel generating set complete with all accessories, equipment, instrument and 

wiring for making the equipment complete and for warranting a trouble free safe 

operation including its design, manufacturing, testing and commissioning will be 

provided for emergency operation of gates and hoists. 

6.4.5 Intake 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. 

6.4.6 Intake Gates, Bulkhead Gates And Hoists 

One number fixed wheel type gate shall be provided just downstream of the bell mouth of 

the intake. The intake gate is 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 gate and embedded parts, one number vertical 

slide gate has been proposed on the upstream of the intake gate. The slide gate shall be 

operated by means of a electrically operated rope drum hoist under balance head 

condition. 

6.4.7 Desilting Chamber Gate And Hoist 

One number slide type gate has been envisaged to cater to the maintenance requirement 

of the desilting chamber. The gate shall be lowered / raised under balanced head 

condition by means of a suitable capacity rope drum hoist.

6.4.8 Silt Flushing Tunnel Gates And Hoists 

66 



Silt-flushing tunnel is provided with a set of two slide (one emergency & one service) 

gates for regulating the discharge through flushing tunnels. Both the (emergency & 

service) gates shall be operated by means of hydraulic hoists. The gate grooves are 

provided with bonnet structures embedded in the concrete & a watertight bonnet cover at 

the top of the groove. 

6.4.9 Surge Shaft Gate And Hoist 

The upstream of the surge shaft is provided with a slide type gate. The gate shall be 

operated under balanced head condition by means of an electrically operated rope drum 

hoist. 

6.4.10 Tailrace Gate And Hoist 

To isolate powerhouse from the river during flood, one number of fixed wheel type gate 

has been envisaged. The fixed wheel gate shall be operated under unbalanced head 

condition by a suitable capacity electrically operated monorail hoist placed in the 

transformer cavern. 

6.4.11 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. 

6.4.12 Pressure Shaft Steel Liner 

One no. Pressure Shaft of dia. 1500 mm fully steel lined will take off from d/s of steel 

transition of Surge Shaft to feed the turbine placed in the power house. It comprises 

horizontal & inclined ferrules, 2 nos. vertical bends, 2 nos. plan bends, 1 no. bifurcation 

and branch pipes for feeding three turbines.

67 



The material of Pressure Shaft liner shall conform to ASTM A537 Class 1. However 

bifurcation material shall conform to ASTM A517 Gr. F.



CHAPTER – VII 

POWER POTENTIAL STUDIES

7.1 GENERAL 

CHAPTER-VII 

POWER POTENTIAL STUDIES 

68 



The Power potential studies of Ringpi 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) = 2966 m 

MDDL (EL) = 2963 m 

TWL = EL 1853 m 

Centre line of M/C = EL 1854.63m 

Rated net head = 1106.37 m 

Type of turbine = Vertical Pelton 

Rated Discharge of Plant = 7.24cumecs 

Proposed Plant Capacity = 70 MW (2x 35MW) 

Generation voltage = 11KV 

Design Energy = 317.41 MU in the 90% dependable year with 

95% machine availability 

Minimum Peaking (Hrs) = 4.00 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.

90% Dependable Year: 

69 



This is the lower decile of the series of the corresponding 10-daily period of the record 

i.e. (N+1) x 0.9 th year where N is the years for which continuous hydrological data are 

available. The 90% dependable year comes out to be 1976-77 whose calculations are 

shown in table 7.2. 

7.3 DEFINITION OF TERMS 

Annual Energy 

This is the yearly energy provided during the 90% dependable hydrological year with 

95% machine availability. 

Firm Power 

This is the power capacity, which can be guaranteed continuously during the lean period 

in 90% dependable year. During lean inflow period the firm power comes out to be 11.69 

MW. 

7.4 FULL RESERVOIR LEVEL (FRL) AND MINIMUM DRAW DOWN 

LEVEL (MDDL) 

FRL and MDDL have been fixed at EL 2966 m & EL 2963 m respectively based on civil 

consideration. This project is envisaged as a run of the river scheme with small pondage. 

7.5 OPERATING HEAD AND HEAD LOSSES 

The net operating head for turbines has been derived from the following formula where 

head losses are taken as 15 m. 

Net operating head =MDDL+2/3 (FRL-MDDL)-TCL-Head losses 

The net operating head comes out to 1106.37 m.

7.6 INSTALLED CAPACITY 

70 



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

has been given in Table 7.4 (A). Considering water availability the total installed capacity 

has been selected as 70 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 2 units each of 35 MW capacity 

with Pelton turbine as prime mover. 

7.8 ENERGY GENERATION 

The energy generation in the 90% dependable year (1976-77) indicating lean inflow 

period and high inflow period is shown in Table 7.4 (B). It may be seen from Table 7.4 

(A) that the total unrestricted energy generation is 410.248 .Annual energy generation at 

70 MW comes out to be 317.41 MU. Annual load factor for lean and mansoon periods 

have been shown in Table 7.4(B). Incremental benefits have been shown in Table 7.6 

which comes out to be 2.45 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 313.61MU after allowing auxiliary consumption of 0.7% and transformer 

losses of 0.5% respectively.

71 



Table-7.1 

DISCHARGE DATA 

PERIOD 1976- 1977- 1978- 1979- 1980- 1981- 1982- 1983- 1984- 1985- 1986- 1987- 1988- 1989- 1990- 1991- 1992- 1993- 1994- 1995- 1996- 

1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 

JUN 

I 

II 

6.83 

13.33 

7.34 

13.03 

10.85 

11.38 

7.73 

9.25 

10.64 

14.16 

9.24 

11.05 

12.88 

14.18 

13.61 

13.21 

19.29 

23.20 

9.21 

11.50 

6.09 

10.33 

10.29 

14.94 

8.13 

11.76 

10.24 

16.97 

11.23 

10.97 

5.96 

9.41 

2.50 

3.57 

4.10 

5.23 

8.48 

11.23 

12.83 

13.72 

7.10 

6.01 

JUL 

III 

I 

II 

9.67 

12.36 

11.78 

9.48 

10.83 

12.47 

14.39 

12.64 

13.55 

13.26 

13.77 

13.17 

15.85 

16.77 

17.17 

15.00 

19.17 

16.43 

15.68 

13.77 

15.42 

18.43 

21.11 

17.96 

20.83 

23.98 

24.06 

32.59 

25.70 

33.53 

15.30 

13.25 

16.56 

12.54 

14.38 

13.75 

12.89 

20.03 

15.73 

17.94 

18.27 

17.97 

12.82 

14.13 

18.02 

8.65 

9.88 

9.63 

6.91 

5.94 

6.01 

6.73 

14.10 

14.09 

13.04 

11.15 

11.82 

13.90 

17.64 

14.80 

10.73 

11.93 

12.84 

III 8.97 15.26 13.07 14.76 17.99 15.46 18.19 17.82 25.43 28.20 14.89 15.38 17.34 16.73 15.42 10.49 6.82 16.53 12.04 11.38 11.43 

AUG 

I 

II 

10.45 

11.39 

12.46 

10.49 

15.47 

13.08 

13.64 

10.77 

18.17 

19.96 

15.07 

15.91 

12.22 

11.57 

14.59 

15.47 

22.93 

23.00 

22.79 

24.03 

13.22 

11.36 

14.56 

15.88 

17.21 

15.79 

14.52 

11.39 

13.13 

13.34 

12.03 

13.86 

7.47 

7.50 

18.54 

17.57 

11.07 

10.81 

12.43 

12.54 

10.93 

10.19 

SEP 

III 

I 

II 

III 

12.18 

11.10 

6.40 

4.67 

12.24 

8.55 

6.99 

5.83 

9.82 

8.14 

10.60 

7.97 

11.42 

11.23 

9.80 

7.19 

16.62 

15.88 

12.45 

10.08 

15.46 

14.80 

12.69 

10.11 

13.58 

10.45 

15.11 

9.91 

18.07 

14.52 

16.33 

18.84 

24.07 

24.79 

23.66 

18.77 

29.43 

12.00 

11.46 

9.85 

12.58 

11.04 

13.72 

11.17 

10.62 

19.10 

10.22 

14.01 

23.96 

11.44 

7.72 

8.63 

11.17 

10.83 

9.81 

9.75 

11.84 

11.36 

10.88 

7.58 

11.46 

11.54 

12.19 

9.44 

8.15 

7.15 

7.04 

5.83 

16.83 

17.71 

14.92 

14.10 

11.63 

9.86 

9.88 

8.54 

11.14 

10.05 

9.00 

8.66 

10.27 

10.25 

9.78 

8.51 

OCT 

I 

II 

3.96 

3.13 

7.12 

4.49 

7.67 

5.98 

11.98 

8.18 

7.88 

6.77 

9.27 

8.58 

7.02 

5.89 

13.24 

13.06 

15.81 

20.05 

8.26 

7.24 

9.00 

6.73 

8.70 

6.48 

7.29 

4.83 

7.70 

6.55 

6.35 

6.47 

7.54 

5.98 

4.40 

3.16 

12.53 

9.30 

6.68 

5.94 

6.40 

6.23 

7.48 

6.86 

NOV 

III 

I 

II 

3.16 

3.14 

2.60 

3.58 

3.72 

3.39 

5.10 

4.08 

3.04 

6.13 

6.11 

4.98 

6.31 

5.33 

4.85 

7.50 

6.39 

5.10 

5.68 

4.45 

3.88 

8.90 

7.28 

6.68 

15.45 

11.51 

9.95 

6.20 

4.84 

4.21 

5.26 

4.83 

4.30 

5.54 

4.50 

2.74 

3.89 

3.21 

2.89 

5.33 

3.31 

2.69 

5.32 

3.26 

2.43 

4.91 

4.07 

3.60 

2.69 

1.98 

1.76 

7.97 

6.61 

5.83 

5.43 

4.47 

3.69 

4.86 

3.16 

3.61 

6.13 

5.58 

5.18 

DEC 

III 

I 

II 

III 

2.32 

1.89 

1.62 

1.49 

2.56 

2.31 

2.45 

2.77 

3.00 

2.89 

2.45 

2.20 

4.69 

4.46 

3.68 

3.54 

4.47 

4.15 

3.77 

3.43 

4.22 

3.88 

3.49 

2.73 

3.75 

3.32 

3.02 

2.90 

5.51 

4.59 

4.31 

3.86 

8.84 

5.67 

5.58 

5.60 

3.84 

3.17 

2.87 

2.70 

3.71 

3.32 

3.06 

2.26 

2.41 

2.27 

2.08 

1.90 

2.70 

2.56 

2.43 

2.30 

2.45 

2.13 

1.85 

1.62 

2.03 

1.86 

1.54 

1.32 

2.74 

2.31 

1.77 

1.56 

1.61 

1.59 

1.38 

1.27 

5.34 

5.21 

4.79 

3.94 

3.08 

2.97 

2.72 

2.57 

3.63 

2.72 

2.42 

2.25 

4.61 

3.17 

2.87 

2.70 

JAN 

I 

II 

1.33 

1.27 

1.90 

1.70 

2.03 

1.87 

3.34 

3.21 

3.30 

3.09 

2.51 

2.79 

2.87 

2.56 

3.44 

3.39 

5.65 

5.36 

2.50 

2.49 

1.97 

1.86 

1.86 

1.86 

1.41 

1.37 

1.48 

1.37 

1.34 

1.32 

1.42 

1.18 

1.29 

1.30 

3.71 

3.45 

2.44 

2.46 

1.94 

1.93 

2.99 

2.84 

FEB 

III 

I 

II 

III 

1.21 

2.23 

2.17 

1.30 

1.74 

1.76 

1.72 

1.58 

1.84 

1.68 

1.67 

1.82 

3.18 

3.06 

3.20 

3.41 

3.05 

2.84 

2.92 

3.53 

2.75 

2.73 

2.84 

2.76 

1.79 

1.63 

1.62 

2.25 

3.02 

2.91 

3.02 

2.90 

4.64 

5.08 

4.64 

5.62 

2.36 

2.38 

2.45 

2.81 

1.74 

1.65 

1.63 

1.79 

1.83 

1.80 

1.88 

2.09 

1.36 

1.51 

1.38 

1.47 

1.24 

1.22 

1.15 

1.11 

1.30 

1.26 

1.20 

1.21 

1.20 

1.27 

1.22 

1.17 

1.22 

1.18 

1.26 

1.21 

3.49 

3.44 

3.29 

3.53 

2.43 

2.41 

2.41 

2.42 

2.04 

2.11 

1.88 

2.05 

2.36 

2.88 

2.87 

2.25 

MAR 

I 

II 

1.23 

1.76 

1.60 

1.72 

1.87 

1.96 

3.51 

3.60 

3.49 

3.70 

2.87 

3.22 

2.42 

3.11 

6.40 

7.15 

7.13 

7.73 

2.99 

3.26 

1.67 

1.99 

2.17 

3.22 

1.67 

1.70 

1.01 

0.83 

1.29 

1.47 

1.26 

1.27 

1.99 

1.98 

3.25 

2.93 

2.20 

2.08 

2.09 

2.41 

2.91 

3.05 

APR 

III 

I 

II 

III 

1.63 

2.37 

2.22 

2.36 

1.90 

2.29 

2.93 

3.47 

2.41 

3.55 

3.53 

4.43 

4.86 

5.46 

7.00 

7.98 

4.37 

4.37 

5.54 

6.53 

3.83 

4.82 

4.81 

5.33 

2.80 

4.12 

3.37 

4.22 

7.03 

7.39 

7.88 

7.88 

7.20 

8.66 

10.45 

12.34 

3.34 

3.29 

4.25 

4.77 

2.50 

4.55 

3.18 

4.20 

3.31 

3.78 

4.27 

4.97 

1.75 

1.82 

2.18 

2.61 

0.84 

0.87 

1.43 

1.78 

1.55 

4.08 

2.32 

2.46 

1.30 

1.54 

2.16 

1.97 

2.07 

2.11 

2.30 

2.76 

3.71 

3.60 

4.51 

4.14 

2.87 

2.81 

3.48 

5.08 

2.57 

2.37 

2.30 

5.12 

2.87 

3.19 

3.17 

3.98 

MAY 

I 

II 

2.58 

3.19 

3.95 

8.10 

6.65 

8.48 

7.61 

6.51 

8.01 

8.65 

6.68 

7.51 

6.79 

8.14 

8.94 

13.07 

8.88 

10.31 

4.47 

4.75 

4.75 

5.28 

5.08 

7.61 

4.58 

4.73 

2.62 

4.62 

4.13 

5.03 

1.94 

2.25 

3.50 

3.15 

4.63 

4.78 

7.41 

11.44 

6.24 

5.47 

3.81 

4.38 

III 4.55 9.46 6.49 6.94 8.39 7.29 10.83 18.56 14.36 5.01 6.20 10.08 11.53 5.32 5.57 2.26 3.19 5.88 11.05 7.57 6.48

YEAR 

Table-7.2 

UNRESTRICTED ENERGY GENERATION 

UNRESTRICTED ENERGY 

ARRANGED IN DESCENDING 

ORDER 

72 



RANK OF 

THE YEAR 

1984-1985 1157.401 1 

1983-1984 876.174 2 

1985-1986 816.100 3 

1980-1981 718.437 4 

1981-1982 670.779 5 

1993-1994 661.965 6 

1979-1980 620.019 7 

1982-1983 618.082 8 

1987-1988 609.362 9 

1988-1989 579.126 10 

1986-1987 559.195 11 

1995-1996 546.002 12 

1994-1995 543.618 13 

1978-1979 536.593 14 

1989-1990 533.657 15 

1990-1991 512.106 16 

1996-1997 506.387 17 

1977-1978 481.352 18 

1991-1992 430.499 19 

1976-1977 410.248 20 

1992-1993 295.777 21 

90% dependable year 

=(N+1) x 0.9th year (where N=no. of years) 

=(21+1)*0.9th year 

=20 

1976-77 is 90% dependable year 

1986-87 is 50% dependable year 

Unrestricted energy of 90% dependable year is 410.248 MU 

90% dependable energy when power restricted to 70 MW is 317.41 MU

Table-7.3 

90% DEPENDABLE FLOWS FOR POWER GENERATION 

MONTH/PERIOD 

JUN 

JUL 

AUG 

SEP 

OCT 

NOV 

DEC 

JAN 

FEB 

MAR 

APR 

MAY 

73 



90% dependable year 1976-77 inflow (cumecs) 

10- daily series for the reservoir 

I 6.83 

II 13.33 

III 9.67 

I 12.36 

II 11.78 

III 8.97 

I 10.45 

II 11.39 

III 12.18 

I 11.10 

II 6.40 

III 4.67 

I 3.96 

II 3.13 

III 3.16 

I 3.14 

II 2.60 

III 2.32 

I 1.89 

II 1.62 

III 1.49 

I 1.33 

II 1.27 

III 1.21 

I 2.23 

II 2.17 

III 1.30 

I 1.23 

II 1.76 

III 1.63 

I 2.37 

II 2.22 

III 2.36 

I 2.58 

II 3.19 

III 4.55

Table-7.4 (A) 

POWER POTENTIAL STUDY OF 90% DEPENDABLE YEAR 1976-1977 

Period Inflow Head Power Unres Energy Energy At Different Restricted Capacities 

74 



CUMEC (M) IN MW (MU) 25 MW 30 MW 35 MW 40 MW 45 MW 50 MW 55 MW 60 MW 65 MW 70 MW 75 MW 80 MW 85 MW 90 MW 95 MW 100 MW 105 MW 

JUNE I 6.83 1106.37 65.998 15.840 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.840 15.840 15.840 15.840 15.840 15.840 15.840 15.840 

II 13.33 1106.37 128.807 30.914 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.940 

III 9.67 1106.37 93.441 22.426 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.305 22.426 22.426 

JULY I 12.36 1106.37 119.434 28.664 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.940 

II 11.78 1106.37 113.830 27.319 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.940 

III 8.97 1106.37 86.677 22.883 6.270 7.524 8.778 10.032 11.286 12.540 13.794 15.048 16.302 17.556 18.810 20.064 21.318 21.739 22.883 22.883 22.883 

AUG I 10.45 1106.37 100.978 24.235 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.023 

II 11.39 1106.37 110.061 26.415 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.940 

III 12.18 1106.37 117.695 31.071 6.270 7.524 8.778 10.032 11.286 12.540 13.794 15.048 16.302 17.556 18.810 20.064 21.318 22.572 23.826 25.080 26.334 

SEPT I 11.10 1106.37 107.259 25.742 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.820 15.960 17.100 18.240 19.380 20.520 21.660 22.800 23.940 

II 6.40 1106.37 61.843 14.842 5.700 6.840 7.980 9.120 10.260 11.400 12.540 13.680 14.100 14.842 14.842 14.842 14.842 14.842 14.842 14.842 14.842 

III 4.67 1106.37 45.126 10.830 5.700 6.840 7.980 9.120 10.260 10.830 10.830 10.830 10.830 10.830 10.830 10.830 10.830 10.830 10.830 10.830 10.830 

OCT I 3.96 1106.37 38.265 9.184 5.700 6.840 7.980 8.724 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 9.184 

II 3.13 1106.37 30.245 7.259 5.700 6.840 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 7.259 

III 3.16 1106.37 30.535 8.061 6.270 7.524 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 8.061 

NOV I 3.14 1106.37 30.342 7.282 5.700 6.840 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 7.282 

II 2.60 1106.37 25.124 6.030 5.700 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 6.030 

III 2.32 1106.37 22.418 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 5.380 

DEC I 1.89 1106.37 18.263 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 4.383 

II 1.62 1106.37 15.654 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 3.757 

III 1.49 1106.37 14.398 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 3.801 

JAN I 1.33 1106.37 12.852 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 3.084 

II 1.27 1106.37 12.272 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 2.945 

III 1.21 1106.37 11.692 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 3.087 

FEB I 2.23 1106.37 21.548 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 5.172 

II 2.17 1106.37 20.969 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 5.032 

III 1.30 1106.37 12.562 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 2.412 

MAR I 1.23 1106.37 11.885 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 2.853 

II 1.76 1106.37 17.007 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 4.082 

III 1.63 1106.37 15.751 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 4.158 

APR I 2.37 1106.37 22.901 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 5.496 

II 2.22 1106.37 21.452 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 5.148 

III 2.36 1106.37 22.805 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 5.473 

MAY I 2.58 1106.37 24.930 5.983 5.684 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 5.983 

II 3.19 1106.37 30.825 7.398 5.700 6.840 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 7.398 

III 4.55 1106.37 43.966 11.607 6.270 7.524 8.778 10.032 11.027 11.607 11.607 11.607 11.607 11.607 11.607 11.607 11.607 11.607 11.607 11.607 11.607 

ENERGY OBTAINED ON 95% M/C AVAILABILITY 410.248 182.53 204.13 222.39 238.30 253.66 267.58 280.35 293.11 305.16 317.41 327.90 338.39 348.88 358.53 368.55 377.77 384.95 

FRL= EL 2966 

MDDL= EL 2963 

TWL= 1853 

Losses= 4 

Overall Efficiency= 89.30%

Net Head 1106.37 

m 

Table-7.4 (B) 

75 



POWER POTENTIAL STUDY OF 90% DEPENDABLE YEAR 1976-1977 WITH 95% MACHINE 

AVAILABILITY 

Period Inflow 

(Cume 

cs) 

JUNE 

JULY 

AUG 

SEPT 

OCT 

NOV 

DEC 

JAN 

FEB 

MAR 

APR 

MAY 

Restricted to 70 

MW 

Head 

(M) 

Unrestri 

cted 

Power 

In Mw 

Design Discharge 7.24 

cumecs 

Unrestric 

ted 

Energy 

(Mu) 

Power 

Restricted 

To 70 Mw 

Energy (Mu) At 

70 Mw With 

95% Machine 

Availability 

Overall efficiency 89.30% 

Energy 

During High 

Inflow Period 

Energy 

During 

Lean 

Inflow 

Period 

10 1-10 6.83 1106. 66.00 15.840 66.00 15.840 0.000 15.840 

10 11-20 13.33 1106. 37 128.81 30.914 70.00 15.960 15.960 0.000 

10 21-30 9.67 1106. 37 93.44 22.426 70.00 15.960 15.960 0.000 

10 1-10 12.36 1106. 37 119.43 28.664 70.00 15.960 15.960 0.000 

10 11-20 11.78 1106. 37 113.83 27.319 70.00 15.960 15.960 0.000 

11 21-31 8.97 1106. 37 86.68 22.883 70.00 17.556 17.556 0.000 

10 1-10 10.45 1106. 37 100.98 24.235 70.00 15.960 15.960 0.000 

10 11-20 11.39 1106. 37 110.06 26.415 70.00 15.960 15.960 0.000 

11 21-31 12.18 1106. 37 117.69 31.071 70.00 17.556 17.556 0.000 

10 1-10 11.10 1106. 37 107.26 25.742 70.00 15.960 15.960 0.000 

10 11-20 6.40 1106. 37 61.84 14.842 61.84 14.842 0.000 14.842 

10 21-30 4.67 1106. 37 45.13 10.830 45.13 10.830 0.000 10.830 

10 1-10 3.96 1106. 37 38.27 9.184 38.27 9.184 0.000 9.184 

10 11-20 3.13 1106. 37 30.25 7.259 30.25 7.259 0.000 7.259 

11 21-31 3.16 1106. 37 30.53 8.061 30.53 8.061 0.000 8.061 

10 1-10 3.14 1106. 37 30.34 7.282 30.34 7.282 0.000 7.282 

10 11-20 2.60 1106. 37 25.12 6.030 25.12 6.030 0.000 6.030 

10 21-30 2.32 1106. 37 22.42 5.380 22.42 5.380 0.000 5.380 

10 1-10 1.89 1106. 37 18.26 4.383 18.26 4.383 0.000 4.383 

10 11-20 1.62 1106. 37 15.65 3.757 15.65 3.757 0.000 3.757 

11 21-31 1.49 1106. 37 14.40 3.801 14.40 3.801 0.000 3.801 

10 1-10 1.33 1106. 37 12.85 3.084 12.85 3.084 0.000 3.084 

10 11-20 1.27 1106. 37 12.27 2.945 12.27 2.945 0.000 2.945 

11 21-31 1.21 1106. 37 11.69 3.087 11.69 3.087 0.000 3.087 

10 1-10 2.23 1106. 37 21.55 5.172 21.55 5.172 0.000 5.172 

10 11-20 2.17 1106. 37 20.97 5.032 20.97 5.032 0.000 5.032 

8 21-28 1.30 1106. 37 12.56 2.412 12.56 2.412 0.000 2.412 

10 1-10 1.23 1106. 37 11.89 2.853 11.89 2.853 0.000 2.853 

10 11-20 1.76 1106. 37 17.01 4.082 17.01 4.082 0.000 4.082 

11 21-31 1.63 1106. 37 15.75 4.158 15.75 4.158 0.000 4.158 

10 1-10 2.37 1106. 37 22.90 5.496 22.90 5.496 0.000 5.496 

10 11-20 2.22 1106. 37 21.45 5.148 21.45 5.148 0.000 5.148 

10 21-30 2.36 1106. 37 22.80 5.473 22.80 5.473 0.000 5.473 

10 1-10 2.58 1106. 37 24.93 5.983 24.93 5.983 0.000 5.983 

10 11-20 3.19 1106. 37 30.82 7.398 30.82 7.398 0.000 7.398 

11 21-31 4.55 1106. 37 43.97 11.607 43.97 11.607 0.000 11.607 

Energy obtained on 95% 37 machine availibility 317.41 146.83 170.58 

LOAD FACTOR 51.76 95.00 37.19

PERIOD 

90% 

DEPENDABL 

E FLOW 

(CUMECS) 

Table-7.5 

POWER GENERATION IN 90% DEPENDABLE YEAR 1976-77 

POWER IN MW ENERGY IN GWH 

RESTRICTED TO 

INSTALLED 

UN RESTRICTED 

UN RESTRICTED 

CAPACITY OF 70 

MW 

76 



RESTRICTED 

TO INSTALLED 

CAPACITY OF 70 

MW 

MONTHLY 

ENERGY 

IN GWH 

1 2 3 4 5 6 7 

1-10 6.83 65.998 66.00 15.840 15.840 

JUN 11-20 13.33 128.807 70.00 30.914 15.960 

47.76 

21-30 9.67 93.441 70.00 22.426 15.960 

1-10 12.36 119.434 70.00 28.664 15.960 

JULY 11-20 11.78 113.830 70.00 27.319 15.960 

49.48 

21-31 8.97 86.677 70.00 22.883 17.556 

1-10 10.45 100.978 70.00 24.235 15.960 

AUG 11-20 11.39 110.061 70.00 26.415 15.960 

49.48 

21-31 12.18 117.695 70.00 31.071 17.556 

1-10 11.10 107.259 70.00 25.742 15.960 

SEPT 11-20 6.40 61.843 61.84 14.842 14.842 

41.63 

21-30 4.67 45.126 45.13 10.830 10.830 

1-10 3.96 38.265 38.27 9.184 9.184 

OCT 11-20 3.13 30.245 30.25 7.259 7.259 

24.50 

21-31 3.16 30.535 30.53 8.061 8.061 

1-10 3.14 30.342 30.34 7.282 7.282 

NOV 11-20 2.60 25.124 25.12 6.030 6.030 

18.69 

21-30 2.32 22.418 22.42 5.380 5.380 

1-10 1.89 18.263 18.26 4.383 4.383 

DEC 11-20 1.62 15.654 15.65 3.757 3.757 

11.94 

21-31 1.49 14.398 14.40 3.801 3.801 

1-10 1.33 12.852 12.85 3.084 3.084 

JAN 11-20 1.27 12.272 12.27 2.945 2.945 

9.12 

21-31 1.21 11.692 11.69 3.087 3.087 

1-10 2.23 21.548 21.55 5.172 5.172 

FEB 11-20 2.17 20.969 20.97 5.032 5.032 

12.62 

21-28 1.30 12.562 12.56 2.412 2.412 

1-10 1.23 11.885 11.89 2.853 2.853 

MAR 11-20 1.76 17.007 17.01 4.082 4.082 

11.09 

21-31 1.63 15.751 15.75 4.158 4.158 

1-10 2.37 22.901 22.90 5.496 5.496 

APR 11-20 2.22 21.452 21.45 5.148 5.148 

16.12 

21-30 2.36 22.805 22.80 5.473 5.473 

1-10 2.58 24.930 24.93 5.983 5.983 

MAY 11-20 3.19 30.825 30.82 7.398 7.398 

24.99 

21-31 4.55 43.966 43.97 11.607 11.607 

ENERGY OBTAINED ON 95% MACHINE AVAILABILITY 317.41

Table-7.6 

77 



INCREMENTAL BENEFIT IN 90% DEPENDABLE YEAR 1976-77 

MW MU ? MU/? MW 

Load Factor 

(%) 

Annual Load Factor 

for additional capacity 

(%) 

25 182.53 83.35% 

4.32 

30 204.13 77.68% 49.33% 

3.65 

35 222.39 72.53% 41.68% 

3.18 

40 238.30 68.01% 36.32% 

3.07 

45 253.66 64.35% 35.07% 

2.78 

50 267.58 61.09% 31.78% 

2.55 

55 280.35 58.19% 29.15% 

2.55 

60 293.11 55.77% 29.15% 

2.41 

65 305.16 53.59% 27.51% 

2.45 

70 317.41 51.76% 27.97% 

2.10 

75 327.90 49.91% 23.95% 

2.10 

80 338.39 48.29% 23.95% 

2.10 

85 348.88 46.85% 23.95% 

1.93 

90 358.53 45.48% 22.04% 

2.00 

95 368.55 44.29% 22.88% 

1.84 

100 377.77 43.12% 21.04% 

1.44 

105 384.945 41.85% 16.39%

INCREMENTAL (DMU/DMW) 

4.504.32 

4.00 

3.50 

3.00 

2.50 

2.00 

1.50 

1.00 

3.65 

3.18 

RINGPI H.E.P. 

INCREMENTAL BENEFIT FOR 90% DEPENDABLE YEAR (1976-77) 

3.07 

2.78 

2.55 

2.55 

2.41 

2.45 

30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 

MW CAPACITY 

78 

2.10 

2.10 

2.10 

1.93 

2.00 

1.84 

1.44 


Ringpi HE Project, (2 x 35 MW)

Table-7.7 (A) 

79 



UNRESTRICTED ENERGY GENERATION IN YEAR 1976-77 

PERIOD INFLOW HEAD POWER UNRESTRICTED 

ENERGY 

CUMEC (M) (MW) (MU) 

JUNE I 6.83 1106.37 65.998 15.840 

II 13.33 1106.37 128.807 30.914 

III 9.67 1106.37 93.441 22.426 

JULY I 12.36 1106.37 119.434 28.664 

II 11.78 1106.37 113.830 27.319 

III 8.97 1106.37 86.677 22.883 

AUG I 10.45 1106.37 100.978 24.235 

II 11.39 1106.37 110.061 26.415 

III 12.18 1106.37 117.695 31.071 

SEPT I 11.10 1106.37 107.259 25.742 

II 6.40 1106.37 61.843 14.842 

III 4.67 1106.37 45.126 10.830 

OCT I 3.96 1106.37 38.265 9.184 

II 3.13 1106.37 30.245 7.259 

III 3.16 1106.37 30.535 8.061 

NOV I 3.14 1106.37 30.342 7.282 

II 2.60 1106.37 25.124 6.030 

III 2.32 1106.37 22.418 5.380 

DEC I 1.89 1106.37 18.263 4.383 

II 1.62 1106.37 15.654 3.757 

III 1.49 1106.37 14.398 3.801 

JAN I 1.33 1106.37 12.852 3.084 

II 1.27 1106.37 12.272 2.945 

III 1.21 1106.37 11.692 3.087 

FEB I 2.23 1106.37 21.548 5.172 

II 2.17 1106.37 20.969 5.032 

III 1.30 1106.37 12.562 2.412 

MAR I 1.23 1106.37 11.885 2.853 

II 1.76 1106.37 17.007 4.082 

III 1.63 1106.37 15.751 4.158 

APR I 2.37 1106.37 22.901 5.496 

II 2.22 1106.37 21.452 5.148 

III 2.36 1106.37 22.805 5.473 

MAY I 2.58 1106.37 24.930 5.983 

II 3.19 1106.37 30.825 7.398 

III 4.55 1106.37 43.966 11.607 

ENERGY OBTAINED 410.248

Table-7.7 (B) 


80 




ENERGY 


JUNE I 7.34 1106.37 70.926 17.022 

II 13.03 1106.37 125.908 30.218 

III 9.48 1106.37 91.605 21.985 

JULY I 10.83 1106.37 104.650 25.116 

II 12.47 1106.37 120.497 28.919 

III 15.26 1106.37 147.457 38.929 

AUG I 12.46 1106.37 120.400 28.896 

II 10.49 1106.37 101.364 24.327 

III 12.24 1106.37 118.275 31.225 

SEPT I 8.55 1106.37 82.618 19.828 

II 6.99 1106.37 67.544 16.211 

III 5.83 1106.37 56.335 13.520 

OCT I 7.12 1106.37 68.800 16.512 

II 4.49 1106.37 43.387 10.413 

III 3.58 1106.37 34.593 9.133 

NOV I 3.72 1106.37 35.946 8.627 

II 3.39 1106.37 32.757 7.862 

III 2.56 1106.37 24.737 5.937 

DEC I 2.31 1106.37 22.321 5.357 

II 2.45 1106.37 23.674 5.682 

III 2.77 1106.37 26.766 7.066 

JAN I 1.90 1106.37 18.360 4.406 

II 1.70 1106.37 16.427 3.942 

III 1.74 1106.37 16.814 4.439 

FEB I 1.76 1106.37 17.007 4.082 

II 1.72 1106.37 16.620 3.989 

III 1.58 1106.37 15.267 2.931 

MAR I 1.60 1106.37 15.461 3.711 

II 1.72 1106.37 16.620 3.989 

III 1.90 1106.37 18.360 4.847 

APR I 2.29 1106.37 22.128 5.311 

II 2.93 1106.37 28.312 6.795 

III 3.47 1106.37 33.530 8.047 

MAY I 3.95 1106.37 38.169 9.160 

II 8.10 1106.37 78.270 18.785 

III 9.46 1106.37 91.412 24.133 


Table-7.7 (C) 


81 




ENERGY 


JUNE I 10.85 1106.37 104.843 25.162 

II 11.38 1106.37 109.964 26.391 

III 14.39 1106.37 139.050 33.372 

JULY I 12.64 1106.37 122.140 29.314 

II 13.55 1106.37 130.933 31.424 

III 13.07 1106.37 126.295 33.342 

AUG I 15.47 1106.37 149.486 35.877 

II 13.08 1106.37 126.392 30.334 

III 9.82 1106.37 94.890 25.051 

SEPT I 8.14 1106.37 78.656 18.878 

II 10.60 1106.37 102.427 24.583 

III 7.97 1106.37 77.014 18.483 

OCT I 7.67 1106.37 74.115 17.788 

II 5.98 1106.37 57.784 13.868 

III 5.10 1106.37 49.281 13.010 

NOV I 4.08 1106.37 39.425 9.462 

II 3.04 1106.37 29.375 7.050 

III 3.00 1106.37 28.989 6.957 

DEC I 2.89 1106.37 27.926 6.702 

II 2.45 1106.37 23.674 5.682 

III 2.20 1106.37 21.259 5.612 

JAN I 2.03 1106.37 19.616 4.708 

II 1.87 1106.37 18.070 4.337 

III 1.84 1106.37 17.780 4.694 

FEB I 1.68 1106.37 16.234 3.896 

II 1.67 1106.37 16.137 3.873 

III 1.82 1106.37 17.587 3.377 

MAR I 1.87 1106.37 18.070 4.337 

II 1.96 1106.37 18.939 4.545 

III 2.41 1106.37 23.288 6.148 

APR I 3.55 1106.37 34.304 8.233 

II 3.53 1106.37 34.110 8.186 

III 4.43 1106.37 42.807 10.274 

MAY I 6.65 1106.37 64.259 15.422 

II 8.48 1106.37 81.942 19.666 

III 6.49 1106.37 62.713 16.556 


Table-7.7 (D) 


82 




ENERGY 


JUNE I 7.73 1106.37 74.695 17.927 

II 9.25 1106.37 89.382 21.452 

III 13.26 1106.37 128.131 30.751 

JULY I 13.77 1106.37 133.059 31.934 

II 13.17 1106.37 127.261 30.543 

III 14.76 1106.37 142.625 37.653 

AUG I 13.64 1106.37 131.803 31.633 

II 10.77 1106.37 104.070 24.977 

III 11.42 1106.37 110.351 29.133 

SEPT I 11.23 1106.37 108.515 26.044 

II 9.80 1106.37 94.697 22.727 

III 7.19 1106.37 69.477 16.674 

OCT I 11.98 1106.37 115.762 27.783 

II 8.18 1106.37 79.043 18.970 

III 6.13 1106.37 59.234 15.638 

NOV I 6.11 1106.37 59.041 14.170 

II 4.98 1106.37 48.122 11.549 

III 4.69 1106.37 45.319 10.877 

DEC I 4.46 1106.37 43.097 10.343 

II 3.68 1106.37 35.560 8.534 

III 3.54 1106.37 34.207 9.031 

JAN I 3.34 1106.37 32.274 7.746 

II 3.21 1106.37 31.018 7.444 

III 3.18 1106.37 30.728 8.112 

FEB I 3.06 1106.37 29.569 7.096 

II 3.20 1106.37 30.921 7.421 

III 3.41 1106.37 32.951 7.117 

MAR I 3.51 1106.37 33.917 8.140 

II 3.60 1106.37 34.787 8.349 

III 4.86 1106.37 46.962 12.398 

APR I 5.46 1106.37 52.760 12.662 

II 7.00 1106.37 67.641 16.234 

III 7.98 1106.37 77.110 18.506 

MAY I 7.61 1106.37 73.535 17.648 

II 6.51 1106.37 62.906 15.097 

III 6.94 1106.37 67.061 17.704 


Table-7.7 (E) 


83 



84 




ENERGY 


JUNE I 10.64 1106.37 102.814 24.675 

II 14.16 1106.37 136.828 32.839 

III 15.85 1106.37 153.158 36.758 

JULY I 16.77 1106.37 162.048 38.891 

II 17.17 1106.37 165.913 39.819 

III 17.99 1106.37 173.837 45.893 

AUG I 18.17 1106.37 175.576 42.138 

II 19.96 1106.37 192.873 46.289 

III 16.62 1106.37 160.598 42.398 

SEPT I 15.88 1106.37 153.448 36.827 

II 12.45 1106.37 120.304 28.873 

III 10.08 1106.37 97.403 23.377 

OCT I 7.88 1106.37 76.144 18.275 

II 6.77 1106.37 65.418 15.700 

III 6.31 1106.37 60.973 16.097 

NOV I 5.33 1106.37 51.504 12.361 

II 4.85 1106.37 46.865 11.248 

III 4.47 1106.37 43.193 10.366 

DEC I 4.15 1106.37 40.101 9.624 

II 3.77 1106.37 36.429 8.743 

III 3.43 1106.37 33.144 8.750 

JAN I 3.30 1106.37 31.888 7.653 

II 3.09 1106.37 29.859 7.166 

III 3.05 1106.37 29.472 7.781 

FEB I 2.84 1106.37 27.443 6.586 

II 2.92 1106.37 28.216 6.772 

III 3.53 1106.37 34.110 6.549 

MAR I 3.49 1106.37 33.724 8.094 

II 3.70 1106.37 35.753 8.581 

III 4.37 1106.37 42.227 11.148 

APR I 4.37 1106.37 42.227 10.135 

II 5.54 1106.37 53.533 12.848 

III 6.53 1106.37 63.099 15.144 

MAY I 8.01 1106.37 77.400 18.576 

II 8.65 1106.37 83.585 20.060 

III 8.39 1106.37 81.072 21.403 


Table-7.7 (F) 


85 




ENERGY 


JUNE I 9.24 1106.37 89.286 21.429 

II 11.05 1106.37 106.776 25.626 

III 15.00 1106.37 144.944 34.787 

JULY I 19.17 1106.37 185.239 44.457 

II 16.43 1106.37 158.762 38.103 

III 15.46 1106.37 149.389 39.439 

AUG I 15.07 1106.37 145.621 34.949 

II 15.91 1106.37 153.738 36.897 

III 15.46 1106.37 149.389 39.439 

SEPT I 14.80 1106.37 143.012 34.323 

II 12.69 1106.37 122.623 29.430 

III 10.11 1106.37 97.693 23.446 

OCT I 9.27 1106.37 89.576 21.498 

II 8.58 1106.37 82.908 19.898 

III 7.50 1106.37 72.472 19.133 

NOV I 6.39 1106.37 61.746 14.819 

II 5.10 1106.37 49.281 11.827 

III 4.22 1106.37 40.778 9.787 

DEC I 3.88 1106.37 37.492 8.998 

II 3.49 1106.37 33.724 8.094 

III 2.73 1106.37 26.380 6.964 

JAN I 2.51 1106.37 24.254 5.821 

II 2.79 1106.37 26.960 6.470 

III 2.75 1106.37 26.573 7.015 

FEB I 2.73 1106.37 26.380 6.331 

II 2.84 1106.37 27.443 6.586 

III 2.76 1106.37 26.670 5.121 

MAR I 2.87 1106.37 27.733 6.656 

II 3.22 1106.37 31.115 7.468 

III 3.83 1106.37 37.009 9.770 

APR I 4.82 1106.37 46.575 11.178 

II 4.81 1106.37 46.479 11.155 

III 5.33 1106.37 51.504 12.361 

MAY I 6.68 1106.37 64.549 15.492 

II 7.51 1106.37 72.569 17.417 

III 7.29 1106.37 70.443 18.597 


Table-7.7 (G) 


86 




ENERGY 


JUNE I 12.88 1106.37 124.459 29.870 

II 14.18 1106.37 137.021 32.885 

III 15.68 1106.37 151.515 36.364 

JULY I 13.77 1106.37 133.059 31.934 

II 15.42 1106.37 149.003 35.761 

III 18.19 1106.37 175.769 46.403 

AUG I 12.22 1106.37 118.081 28.340 

II 11.57 1106.37 111.800 26.832 

III 13.58 1106.37 131.223 34.643 

SEPT I 10.45 1106.37 100.978 24.235 

II 15.11 1106.37 146.007 35.042 

III 9.91 1106.37 95.760 22.982 

OCT I 7.02 1106.37 67.834 16.280 

II 5.89 1106.37 56.915 13.660 

III 5.68 1106.37 54.886 14.490 

NOV I 4.45 1106.37 43.000 10.320 

II 3.88 1106.37 37.492 8.998 

III 3.75 1106.37 36.236 8.697 

DEC I 3.32 1106.37 32.081 7.699 

II 3.02 1106.37 29.182 7.004 

III 2.90 1106.37 28.023 7.398 

JAN I 2.87 1106.37 27.733 6.656 

II 2.56 1106.37 24.737 5.937 

III 1.79 1106.37 17.297 4.566 

FEB I 1.63 1106.37 15.751 3.780 

II 1.62 1106.37 15.654 3.757 

III 2.25 1106.37 21.742 4.174 

MAR I 2.42 1106.37 23.384 5.612 

II 3.11 1106.37 30.052 7.212 

III 2.80 1106.37 27.056 7.143 

APR I 4.12 1106.37 39.811 9.555 

II 3.37 1106.37 32.564 7.815 

III 4.22 1106.37 40.778 9.787 

MAY I 6.79 1106.37 65.611 15.747 

II 8.14 1106.37 78.656 18.878 

III 10.83 1106.37 104.650 27.628 


Table-7.7 (H) 


87 




ENERGY 


JUNE I 13.61 1106.37 131.513 31.563 

II 13.21 1106.37 127.648 30.635 

III 18.43 1106.37 178.088 42.741 

JULY I 21.11 1106.37 203.985 48.956 

II 17.96 1106.37 173.547 41.651 

III 17.82 1106.37 172.194 45.459 

AUG I 14.59 1106.37 140.983 33.836 

II 15.47 1106.37 149.486 35.877 

III 18.07 1106.37 174.610 46.097 

SEPT I 14.52 1106.37 140.306 33.673 

II 16.33 1106.37 157.796 37.871 

III 18.84 1106.37 182.050 43.692 

OCT I 13.24 1106.37 127.938 30.705 

II 13.06 1106.37 126.198 30.288 

III 8.90 1106.37 86.000 22.704 

NOV I 7.28 1106.37 70.346 16.883 

II 6.68 1106.37 64.549 15.492 

III 5.51 1106.37 53.243 12.778 

DEC I 4.59 1106.37 44.353 10.645 

II 4.31 1106.37 41.647 9.995 

III 3.86 1106.37 37.299 9.847 

JAN I 3.44 1106.37 33.241 7.978 

II 3.39 1106.37 32.757 7.862 

III 3.02 1106.37 29.182 7.704 

FEB I 2.91 1106.37 28.119 6.749 

II 3.02 1106.37 29.182 7.004 

III 2.90 1106.37 28.023 6.053 

MAR I 6.40 1106.37 61.843 14.842 

II 7.15 1106.37 69.090 16.582 

III 7.03 1106.37 67.931 17.934 

APR I 7.39 1106.37 71.409 17.138 

II 7.88 1106.37 76.144 18.275 

III 7.88 1106.37 76.144 18.275 

MAY I 8.94 1106.37 86.387 20.733 

II 13.07 1106.37 126.295 30.311 

III 18.56 1106.37 179.345 47.347 


Table-7.7 (I) 


88 




ENERGY 


JUNE I 19.29 1106.37 186.398 44.736 

II 23.20 1106.37 224.181 53.803 

III 20.83 1106.37 201.279 48.307 

JULY I 23.98 1106.37 231.718 55.612 

II 24.06 1106.37 232.491 55.798 

III 25.43 1106.37 245.729 64.872 

AUG I 22.93 1106.37 221.572 53.177 

II 23.00 1106.37 222.248 53.340 

III 24.07 1106.37 232.587 61.403 

SEPT I 24.79 1106.37 239.545 57.491 

II 23.66 1106.37 228.626 54.870 

III 18.77 1106.37 181.374 43.530 

OCT I 15.81 1106.37 152.771 36.665 

II 20.05 1106.37 193.742 46.498 

III 15.45 1106.37 149.293 39.413 

NOV I 11.51 1106.37 111.221 26.693 

II 9.95 1106.37 96.146 23.075 

III 8.84 1106.37 85.421 20.501 

DEC I 5.67 1106.37 54.789 13.149 

II 5.58 1106.37 53.919 12.941 

III 5.60 1106.37 54.113 14.286 

JAN I 5.65 1106.37 54.596 13.103 

II 5.36 1106.37 51.793 12.430 

III 4.64 1106.37 44.836 11.837 

FEB I 5.08 1106.37 49.088 11.781 

II 4.64 1106.37 44.836 10.761 

III 5.62 1106.37 54.306 10.427 

MAR I 7.13 1106.37 68.897 16.535 

II 7.73 1106.37 74.695 17.927 

III 7.20 1106.37 69.573 18.367 

APR I 8.66 1106.37 83.681 20.083 

II 10.45 1106.37 100.978 24.235 

III 12.34 1106.37 119.241 28.618 

MAY I 8.88 1106.37 85.807 20.594 

II 10.31 1106.37 99.625 23.910 

III 14.36 1106.37 138.760 36.633 


Table-7.7 (J) 


89 




ENERGY 


JUNE I 9.21 1106.37 88.996 21.359 

II 11.50 1106.37 111.124 26.670 

III 32.59 1106.37 314.916 75.580 

JULY I 25.70 1106.37 248.338 59.601 

II 33.53 1106.37 323.999 77.760 

III 28.20 1106.37 272.495 71.939 

AUG I 22.79 1106.37 220.219 52.853 

II 24.03 1106.37 232.201 55.728 

III 29.43 1106.37 284.381 75.077 

SEPT I 12.00 1106.37 115.956 27.829 

II 11.46 1106.37 110.738 26.577 

III 9.85 1106.37 95.180 22.843 

OCT I 8.26 1106.37 79.816 19.156 

II 7.24 1106.37 69.960 16.790 

III 6.20 1106.37 59.910 15.816 

NOV I 4.84 1106.37 46.769 11.224 

II 4.21 1106.37 40.681 9.763 

III 3.84 1106.37 37.106 8.905 

DEC I 3.17 1106.37 30.632 7.352 

II 2.87 1106.37 27.733 6.656 

III 2.70 1106.37 26.090 6.888 

JAN I 2.50 1106.37 24.157 5.798 

II 2.49 1106.37 24.061 5.775 

III 2.36 1106.37 22.805 6.020 

FEB I 2.38 1106.37 22.998 5.519 

II 2.45 1106.37 23.674 5.682 

III 2.81 1106.37 27.153 5.213 

MAR I 2.99 1106.37 28.892 6.934 

II 3.26 1106.37 31.501 7.560 

III 3.34 1106.37 32.274 8.520 

APR I 3.29 1106.37 31.791 7.630 

II 4.25 1106.37 41.068 9.856 

III 4.77 1106.37 46.092 11.062 

MAY I 4.47 1106.37 43.193 10.366 

II 4.75 1106.37 45.899 11.016 

III 5.01 1106.37 48.411 12.781 


Table-7.7 (K) 


90 




ENERGY 


JUNE I 6.09 1106.37 58.847 14.123 

II 10.33 1106.37 99.818 23.956 

III 15.30 1106.37 147.843 35.482 

JULY I 13.25 1106.37 128.034 30.728 

II 16.56 1106.37 160.019 38.404 

III 14.89 1106.37 143.881 37.985 

AUG I 13.22 1106.37 127.744 30.659 

II 11.36 1106.37 109.771 26.345 

III 12.58 1106.37 121.560 32.092 

SEPT I 11.04 1106.37 106.679 25.603 

II 13.72 1106.37 132.576 31.818 

III 11.17 1106.37 107.935 25.904 

OCT I 9.00 1106.37 86.967 20.872 

II 6.73 1106.37 65.032 15.608 

III 5.26 1106.37 50.827 13.418 

NOV I 4.83 1106.37 46.672 11.201 

II 4.30 1106.37 41.551 9.972 

III 3.71 1106.37 35.850 8.604 

DEC I 3.32 1106.37 32.081 7.699 

II 3.06 1106.37 29.569 7.096 

III 2.26 1106.37 21.838 5.765 

JAN I 1.97 1106.37 19.036 4.569 

II 1.86 1106.37 17.973 4.314 

III 1.74 1106.37 16.814 4.439 

FEB I 1.65 1106.37 15.944 3.827 

II 1.63 1106.37 15.751 3.780 

III 1.79 1106.37 17.297 3.321 

MAR I 1.67 1106.37 16.137 3.873 

II 1.99 1106.37 19.229 4.615 

III 2.50 1106.37 24.157 6.378 

APR I 4.55 1106.37 43.966 10.552 

II 3.18 1106.37 30.728 7.375 

III 4.20 1106.37 40.584 9.740 

MAY I 4.75 1106.37 45.899 11.016 

II 5.28 1106.37 51.020 12.245 

III 6.20 1106.37 59.910 15.816 


Table-7.7 (L) 


91 




ENERGY 


JUNE I 10.29 1106.37 99.432 23.864 

II 14.94 1106.37 144.365 34.648 

III 12.54 1106.37 121.174 29.082 

JULY I 14.38 1106.37 138.953 33.349 

II 13.75 1106.37 132.866 31.888 

III 15.38 1106.37 148.616 39.235 

AUG I 14.56 1106.37 140.693 33.766 

II 15.88 1106.37 153.448 36.827 

III 10.62 1106.37 102.621 27.092 

SEPT I 19.10 1106.37 184.563 44.295 

II 10.22 1106.37 98.755 23.701 

III 14.01 1106.37 135.378 32.491 

OCT I 8.70 1106.37 84.068 20.176 

II 6.48 1106.37 62.616 15.028 

III 5.54 1106.37 53.533 14.133 

NOV I 4.50 1106.37 43.483 10.436 

II 2.74 1106.37 26.477 6.354 

III 2.41 1106.37 23.288 5.589 

DEC I 2.27 1106.37 21.935 5.264 

II 2.08 1106.37 20.099 4.824 

III 1.90 1106.37 18.360 4.847 

JAN I 1.86 1106.37 17.973 4.314 

II 1.86 1106.37 17.973 4.314 

III 1.83 1106.37 17.683 4.668 

FEB I 1.80 1106.37 17.393 4.174 

II 1.88 1106.37 18.166 4.360 

III 2.09 1106.37 20.196 4.362 

MAR I 2.17 1106.37 20.969 5.032 

II 3.22 1106.37 31.115 7.468 

III 3.31 1106.37 31.984 8.444 

APR I 3.78 1106.37 36.526 8.766 

II 4.27 1106.37 41.261 9.903 

III 4.97 1106.37 48.025 11.526 

MAY I 5.08 1106.37 49.088 11.781 

II 7.61 1106.37 73.535 17.648 

III 10.08 1106.37 97.403 25.714 


Table-7.7 (M) 


92 




ENERGY 


JUNE I 8.13 1106.37 78.560 18.854 

II 11.76 1106.37 113.636 27.273 

III 12.89 1106.37 124.556 29.893 

JULY I 20.03 1106.37 193.549 46.452 

II 15.73 1106.37 151.998 36.480 

III 17.34 1106.37 167.556 44.235 

AUG I 17.21 1106.37 166.300 39.912 

II 15.79 1106.37 152.578 36.619 

III 23.96 1106.37 231.525 61.122 

SEPT I 11.44 1106.37 110.544 26.531 

II 7.72 1106.37 74.598 17.904 

III 8.63 1106.37 83.391 20.014 

OCT I 7.29 1106.37 70.443 16.906 

II 4.83 1106.37 46.672 11.201 

III 3.89 1106.37 37.589 9.923 

NOV I 3.21 1106.37 31.018 7.444 

II 2.89 1106.37 27.926 6.702 

III 2.70 1106.37 26.090 6.262 

DEC I 2.56 1106.37 24.737 5.937 

II 2.43 1106.37 23.481 5.635 

III 2.30 1106.37 22.225 5.867 

JAN I 1.41 1106.37 13.625 3.270 

II 1.37 1106.37 13.238 3.177 

III 1.36 1106.37 13.142 3.469 

FEB I 1.51 1106.37 14.591 3.502 

II 1.38 1106.37 13.335 3.200 

III 1.47 1106.37 14.205 2.727 

MAR I 1.67 1106.37 16.137 3.873 

II 1.70 1106.37 16.427 3.942 

III 1.75 1106.37 16.910 4.464 

APR I 1.82 1106.37 17.587 4.221 

II 2.18 1106.37 21.065 5.056 

III 2.61 1106.37 25.220 6.053 

MAY I 4.58 1106.37 44.256 10.622 

II 4.73 1106.37 45.706 10.969 

III 11.53 1106.37 111.414 29.413 


Table-7.7 (N) 


93 




ENERGY 


JUNE I 10.24 1106.37 98.949 23.748 

II 16.97 1106.37 163.980 39.355 

III 17.94 1106.37 173.353 41.605 

JULY I 18.27 1106.37 176.542 42.370 

II 17.97 1106.37 173.643 41.674 

III 16.73 1106.37 161.661 42.679 

AUG I 14.52 1106.37 140.306 33.673 

II 11.39 1106.37 110.061 26.415 

III 11.17 1106.37 107.935 28.495 

SEPT I 10.83 1106.37 104.650 25.116 

II 9.81 1106.37 94.794 22.750 

III 9.75 1106.37 94.214 22.611 

OCT I 7.70 1106.37 74.405 17.857 

II 6.55 1106.37 63.292 15.190 

III 5.33 1106.37 51.504 13.597 

NOV I 3.31 1106.37 31.984 7.676 

II 2.69 1106.37 25.993 6.238 

III 2.45 1106.37 23.674 5.682 

DEC I 2.13 1106.37 20.582 4.940 

II 1.85 1106.37 17.876 4.290 

III 1.62 1106.37 15.654 4.133 

JAN I 1.48 1106.37 14.301 3.432 

II 1.37 1106.37 13.238 3.177 

III 1.24 1106.37 11.982 3.163 

FEB I 1.22 1106.37 11.789 2.829 

II 1.15 1106.37 11.112 2.667 

III 1.11 1106.37 10.726 2.059 

MAR I 1.01 1106.37 9.760 2.342 

II 0.83 1106.37 8.020 1.925 

III 0.84 1106.37 8.117 2.143 

APR I 0.87 1106.37 8.407 2.018 

II 1.43 1106.37 13.818 3.316 

III 1.78 1106.37 17.200 4.128 

MAY I 2.62 1106.37 25.317 6.076 

II 4.62 1106.37 44.643 10.714 

III 5.32 1106.37 51.407 13.571 


Table-7.7 (O) 


94 




ENERGY 


JUNE I 11.23 1106.37 108.515 26.044 

II 10.97 1106.37 106.003 25.441 

III 12.82 1106.37 123.879 29.731 

JULY I 14.13 1106.37 136.538 32.769 

II 18.02 1106.37 174.127 41.790 

III 15.42 1106.37 149.003 39.337 

AUG I 13.13 1106.37 126.875 30.450 

II 13.34 1106.37 128.904 30.937 

III 11.84 1106.37 114.409 30.204 

SEPT I 11.36 1106.37 109.771 26.345 

II 10.88 1106.37 105.133 25.232 

III 7.58 1106.37 73.245 17.579 

OCT I 6.35 1106.37 61.360 14.726 

II 6.47 1106.37 62.519 15.005 

III 5.32 1106.37 51.407 13.571 

NOV I 3.26 1106.37 31.501 7.560 

II 2.43 1106.37 23.481 5.635 

III 2.03 1106.37 19.616 4.708 

DEC I 1.86 1106.37 17.973 4.314 

II 1.54 1106.37 14.881 3.571 

III 1.32 1106.37 12.755 3.367 

JAN I 1.34 1106.37 12.948 3.108 

II 1.32 1106.37 12.755 3.061 

III 1.30 1106.37 12.562 3.316 

FEB I 1.26 1106.37 12.175 2.922 

II 1.20 1106.37 11.596 2.783 

III 1.21 1106.37 11.692 2.245 

MAR I 1.29 1106.37 12.465 2.992 

II 1.47 1106.37 14.205 3.409 

III 1.55 1106.37 14.978 3.954 

APR I 4.08 1106.37 39.425 9.462 

II 2.32 1106.37 22.418 5.380 

III 2.46 1106.37 23.771 5.705 

MAY I 4.13 1106.37 39.908 9.578 

II 5.03 1106.37 48.605 11.665 

III 5.57 1106.37 53.823 14.209 


Table-7.7 (P) 


95 




ENERGY 


JUNE I 5.96 1106.37 57.591 13.822 

II 9.41 1106.37 90.928 21.823 

III 8.65 1106.37 83.585 20.060 

JULY I 9.88 1106.37 95.470 22.913 

II 9.63 1106.37 93.054 22.333 

III 10.49 1106.37 101.364 26.760 

AUG I 12.03 1106.37 116.245 27.899 

II 13.86 1106.37 133.929 32.143 

III 11.46 1106.37 110.738 29.235 

SEPT I 11.54 1106.37 111.511 26.763 

II 12.19 1106.37 117.791 28.270 

III 9.44 1106.37 91.218 21.892 

OCT I 7.54 1106.37 72.859 17.486 

II 5.98 1106.37 57.784 13.868 

III 4.91 1106.37 47.445 12.526 

NOV I 4.07 1106.37 39.328 9.439 

II 3.60 1106.37 34.787 8.349 

III 2.74 1106.37 26.477 6.354 

DEC I 2.31 1106.37 22.321 5.357 

II 1.77 1106.37 17.103 4.105 

III 1.56 1106.37 15.074 3.980 

JAN I 1.42 1106.37 13.721 3.293 

II 1.18 1106.37 11.402 2.737 

III 1.20 1106.37 11.596 3.061 

FEB I 1.27 1106.37 12.272 2.945 

II 1.22 1106.37 11.789 2.829 

III 1.17 1106.37 11.306 2.442 

MAR I 1.26 1106.37 12.175 2.922 

II 1.27 1106.37 12.272 2.945 

III 1.30 1106.37 12.562 3.316 

APR I 1.54 1106.37 14.881 3.571 

II 2.16 1106.37 20.872 5.009 

III 1.97 1106.37 19.036 4.569 

MAY I 1.94 1106.37 18.746 4.499 

II 2.25 1106.37 21.742 5.218 

III 2.26 1106.37 21.838 5.765 


Table-7.7 (Q) 


96 




ENERGY 


JUNE I 2.50 1106.37 24.157 5.798 

II 3.57 1106.37 34.497 8.279 

III 6.91 1106.37 66.771 16.025 

JULY I 5.94 1106.37 57.398 13.776 

II 6.01 1106.37 58.074 13.938 

III 6.82 1106.37 65.901 17.398 

AUG I 7.47 1106.37 72.182 17.324 

II 7.50 1106.37 72.472 17.393 

III 8.15 1106.37 78.753 20.791 

SEPT I 7.15 1106.37 69.090 16.582 

II 7.04 1106.37 68.027 16.327 

III 5.83 1106.37 56.335 13.520 

OCT I 4.40 1106.37 42.517 10.204 

II 3.16 1106.37 30.535 7.328 

III 2.69 1106.37 25.993 6.862 

NOV I 1.98 1106.37 19.133 4.592 

II 1.76 1106.37 17.007 4.082 

III 1.61 1106.37 15.557 3.734 

DEC I 1.59 1106.37 15.364 3.687 

II 1.38 1106.37 13.335 3.200 

III 1.27 1106.37 12.272 3.240 

JAN I 1.29 1106.37 12.465 2.992 

II 1.30 1106.37 12.562 3.015 

III 1.22 1106.37 11.789 3.112 

FEB I 1.18 1106.37 11.402 2.737 

II 1.26 1106.37 12.175 2.922 

III 1.21 1106.37 11.692 2.245 

MAR I 1.99 1106.37 19.229 4.615 

II 1.98 1106.37 19.133 4.592 

III 2.07 1106.37 20.002 5.281 

APR I 2.11 1106.37 20.389 4.893 

II 2.30 1106.37 22.225 5.334 

III 2.76 1106.37 26.670 6.401 

MAY I 3.50 1106.37 33.820 8.117 

II 3.15 1106.37 30.438 7.305 

III 3.19 1106.37 30.825 8.138 


Table-7.7 (R) 


97 




ENERGY 


JUNE I 4.10 1106.37 39.618 9.508 

II 5.23 1106.37 50.537 12.129 

III 6.73 1106.37 65.032 15.608 

JULY I 14.10 1106.37 136.248 32.699 

II 14.09 1106.37 136.151 32.676 

III 16.53 1106.37 159.729 42.168 

AUG I 18.54 1106.37 179.151 42.996 

II 17.57 1106.37 169.778 40.747 

III 16.83 1106.37 162.628 42.934 

SEPT I 17.71 1106.37 171.131 41.071 

II 14.92 1106.37 144.171 34.601 

III 14.10 1106.37 136.248 32.699 

OCT I 12.53 1106.37 121.077 29.058 

II 9.30 1106.37 89.866 21.568 

III 7.97 1106.37 77.014 20.332 

NOV I 6.61 1106.37 63.872 15.329 

II 5.83 1106.37 56.335 13.520 

III 5.34 1106.37 51.600 12.384 

DEC I 5.21 1106.37 50.344 12.083 

II 4.79 1106.37 46.286 11.109 

III 3.94 1106.37 38.072 10.051 

JAN I 3.71 1106.37 35.850 8.604 

II 3.45 1106.37 33.337 8.001 

III 3.49 1106.37 33.724 8.903 

FEB I 3.44 1106.37 33.241 7.978 

II 3.29 1106.37 31.791 7.630 

III 3.53 1106.37 34.110 6.549 

MAR I 3.25 1106.37 31.405 7.537 

II 2.93 1106.37 28.312 6.795 

III 3.71 1106.37 35.850 9.464 

APR I 3.60 1106.37 34.787 8.349 

II 4.51 1106.37 43.580 10.459 

III 4.14 1106.37 40.005 9.601 

MAY I 4.63 1106.37 44.740 10.737 

II 4.78 1106.37 46.189 11.085 

III 5.88 1106.37 56.818 15.000 


Table-7.7 (S) 


98 




ENERGY 


JUNE I 8.48 1106.37 81.942 19.666 

II 11.23 1106.37 108.515 26.044 

III 13.04 1106.37 126.005 30.241 

JULY I 11.15 1106.37 107.742 25.858 

II 11.82 1106.37 114.216 27.412 

III 12.04 1106.37 116.342 30.714 

AUG I 11.07 1106.37 106.969 25.673 

II 10.81 1106.37 104.457 25.070 

III 11.63 1106.37 112.380 29.668 

SEPT I 9.86 1106.37 95.277 22.866 

II 9.88 1106.37 95.470 22.913 

III 8.54 1106.37 82.522 19.805 

OCT I 6.68 1106.37 64.549 15.492 

II 5.94 1106.37 57.398 13.776 

III 5.43 1106.37 52.470 13.852 

NOV I 4.47 1106.37 43.193 10.366 

II 3.69 1106.37 35.656 8.558 

III 3.08 1106.37 29.762 7.143 

DEC I 2.97 1106.37 28.699 6.888 

II 2.72 1106.37 26.283 6.308 

III 2.57 1106.37 24.834 6.556 

JAN I 2.44 1106.37 23.578 5.659 

II 2.46 1106.37 23.771 5.705 

III 2.43 1106.37 23.481 6.199 

FEB I 2.41 1106.37 23.288 5.589 

II 2.41 1106.37 23.288 5.589 

III 2.42 1106.37 23.384 4.490 

MAR I 2.20 1106.37 21.259 5.102 

II 2.08 1106.37 20.099 4.824 

III 2.87 1106.37 27.733 7.321 

APR I 2.81 1106.37 27.153 6.517 

II 3.48 1106.37 33.627 8.071 

III 5.08 1106.37 49.088 11.781 

MAY I 7.41 1106.37 71.603 17.185 

II 11.44 1106.37 110.544 26.531 

III 11.05 1106.37 106.776 28.189 


Table-7.7 (T) 


99 




ENERGY 


JUNE I 12.83 1106.37 123.976 29.754 

II 13.72 1106.37 132.576 31.818 

III 13.90 1106.37 134.315 32.236 

JULY I 17.64 1106.37 170.455 40.909 

II 14.80 1106.37 143.012 34.323 

III 11.38 1106.37 109.964 29.031 

AUG I 12.43 1106.37 120.111 28.827 

II 12.54 1106.37 121.174 29.082 

III 11.14 1106.37 107.645 28.418 

SEPT I 10.05 1106.37 97.113 23.307 

II 9.00 1106.37 86.967 20.872 

III 8.66 1106.37 83.681 20.083 

OCT I 6.40 1106.37 61.843 14.842 

II 6.23 1106.37 60.200 14.448 

III 4.86 1106.37 46.962 12.398 

NOV I 3.16 1106.37 30.535 7.328 

II 3.61 1106.37 34.883 8.372 

III 3.63 1106.37 35.077 8.418 

DEC I 2.72 1106.37 26.283 6.308 

II 2.42 1106.37 23.384 5.612 

III 2.25 1106.37 21.742 5.740 

JAN I 1.94 1106.37 18.746 4.499 

II 1.93 1106.37 18.650 4.476 

III 2.04 1106.37 19.712 5.204 

FEB I 2.11 1106.37 20.389 4.893 

II 1.88 1106.37 18.166 4.360 

III 2.05 1106.37 19.809 4.279 

MAR I 2.09 1106.37 20.196 4.847 

II 2.41 1106.37 23.288 5.589 

III 2.57 1106.37 24.834 6.556 

APR I 2.37 1106.37 22.901 5.496 

II 2.30 1106.37 22.225 5.334 

III 5.12 1106.37 49.474 11.874 

MAY I 6.24 1106.37 60.297 14.471 

II 5.47 1106.37 52.856 12.686 

III 7.57 1106.37 73.149 19.311 


Table-7.7 (U) 


100 




ENERGY 


JUNE I 7.10 1106.37 68.607 16.466 

II 6.01 1106.37 58.074 13.938 

III 10.73 1106.37 103.684 24.884 

JULY I 11.93 1106.37 115.279 27.667 

II 12.84 1106.37 124.072 29.777 

III 11.43 1106.37 110.448 29.158 

AUG I 10.93 1106.37 105.616 25.348 

II 10.19 1106.37 98.466 23.632 

III 10.27 1106.37 99.239 26.199 

SEPT I 10.25 1106.37 99.045 23.771 

II 9.78 1106.37 94.504 22.681 

III 8.51 1106.37 82.232 19.736 

OCT I 7.48 1106.37 72.279 17.347 

II 6.86 1106.37 66.288 15.909 

III 6.13 1106.37 59.234 15.638 

NOV I 5.58 1106.37 53.919 12.941 

II 5.18 1106.37 50.054 12.013 

III 4.61 1106.37 44.546 10.691 

DEC I 3.17 1106.37 30.632 7.352 

II 2.87 1106.37 27.733 6.656 

III 2.70 1106.37 26.090 6.888 

JAN I 2.99 1106.37 28.892 6.934 

II 2.84 1106.37 27.443 6.586 

III 2.36 1106.37 22.805 6.020 

FEB I 2.88 1106.37 27.829 6.679 

II 2.87 1106.37 27.733 6.656 

III 2.25 1106.37 21.742 4.174 

MAR I 2.91 1106.37 28.119 6.749 

II 3.05 1106.37 29.472 7.073 

III 2.87 1106.37 27.733 7.321 

APR I 3.19 1106.37 30.825 7.398 

II 3.17 1106.37 30.632 7.352 

III 3.98 1106.37 38.459 9.230 

MAY I 3.81 1106.37 36.816 8.836 

II 4.38 1106.37 42.324 10.158 

III 6.48 1106.37 62.616 16.531 

ENERGY OBTAINED ON 95% M/C AVAILABILITY 506.387



CHAPTER – VIII 

POWER EVACUATION

8.1 GENERAL 

CHAPTER-VIII 

POWER EVACUATION 

101 



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 Ringpi 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 Ringpi Hydro Electric Project can be done through one no. 220 kV double 

circuit line to be connected at the pooling point which can be assumed to come up near 

Teesta (II)H.E. Project about a distance of 2.0 Km The length of this 220 kV double 

circuit line would be approximately 36 km.



CHAPTER – IX 

ENVIRONMENTAL ASPECTS


9.1.1 General 

CHAPTER - IX 

ENVIRONMENTAL ASPECTS 

102 



Ringpi H. E. Project is one of the various projects proposed in Teesta river basin in Sikkim 

(Fig 9.1). The National Hydroelectric Power Corporation proposes to construct a 40 m 

high concrete gravity dam on river Ringpi chu, just downstream to the confluence of 

Jhumthul chu and Kishong chu in the North District of Sikkim. The underground 

powerhouse with an installed capacity of 70 MW would be located just upstream to the 

reservoir of Lingza Hydroelectric scheme. A 7 km long Head Race Tunnel and 250 m 

long tailrace channel would be constructed. 

9.1.2 Location 

The proposed project is located downstream to the confluence of Jumthul chu and Kishong 

chu in North district of Sikkim between longitude 88°26’39’’E & 88° 27’ 09’’ and latitude 

27°40’35’’N & 27° 36’ 21’’. This is one of the highest altitude hydroelectric schemes 

proposed on this river. Located between 2900 m and 3000m above MSL. The project 

involves construction of a diversion dam immediately downstream to the confluence of the 

two streams Jumthul and Kishong (Fig. 9.2). The dam site is to be located near the Tolung 

village in Sakyong Pentong Revenue Block at the confluence of Jumthul chu and 

Kishong chu (Fig. 9.2). The powerhouse is located on the right bank of Ringpi chu about 

2 km upstream of Shabrung village. New Jalpaiguri is the nearest railhead and Bagdogra 

is the nearest airport. Location details of the project are as below: 

Town /Village : Tolung 

Revenue Block : Sakyong Pentong 

Sub-division : Mangan 

District : North Sikkim 

State : Sikkim

9.2 PHYSICAL ENVIRONMENT 

9.2.1 Climate/Meteorology 

103 



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

zones. For most of the period in the year, the climate is cold and humid as rainfall occurs 

in each month. Although there is a classification of various sorts of seasons in Sikkim, a 

very 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. The area experiences heavy rainfall due to its proximity 

to the Bay of Bengal. The general trend of decrease in temperature with increase in 

altitude holds good everywhere. 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 

Temperature varies with altitude and slope. The maximum temperature is recorded 

usually during July and August and minimum during December & January. Fog is a 

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

high altitude places in the winter months and snowfall is also common 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.

9.2.2 Topography 

104 



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

It is essentially a mountainous State without flat piece of land of any extent anywhere. 

The mountains rise in elevation northward. The northern portion of the State is deeply cut 

into steep escarpments and except in the Lachen and Lachung valleys, is not populated. 

Southern 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 southern. The trend of 

the mountain system is in general east-west direction. However, the main ridges run in a 

more or less north-south direction. The Rangeet and the Teesta, which form the main 

channels of drainage, run nearly north-south. The valleys cut by these rivers and their 

chief 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. 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 

105 



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 (

GROUP LITHOLOGY 

106 



Gondwana Grits, pebble cum boulder beds and carbonaceous 

shales with occasional coal seam, pegmatite and 

quartzite (tourmaline bearing) 

Daling Inter-bedded quartzite and chlorite sericite 

phyllite/schist 

Lingza granite. 

Quartzite/Biotite schist. 

Chungthang Interbedded quartzite and garnetiferous quartz 

Central Crystalline 

Gneissic complex 

(CCGC) 

biotite schist. 

Calc-silicate rock/marble. 

Garnet-kyanite-silimanite-biotite-quartz-schist 

Banded gneiss with augen gneiss and quartz-biotite 

gneiss. 

Augen gneiss 

The area falls within axial belt of Central Crystalline Zone of the North Sikkim 

Himalayas where the rock types are mainly high grade gneisses having inter-bands of 

meta-sedimentaries represented by calc-silicate/quartzite, high-grade schist and their fine 

inter laminations. The meta-sedimentaies occur as enclaves in the high-grade gneisses in 

the area around the proposed project. Discordant tourmaline bearing quartz veins and 

pegmatite often intrudes all these rock types. 

9.2.5 Seismicity 

Sikkim is a part of active Himalayan belt, which is tectonically young. The area has 

experienced mild tremours in the recent past. One earthquake of magnitude 6.0 in 

Richter scale was recorded on November 20 th , 1980. The project area falls in Zone IV of 

Seismic Zoning Map of India as per IS 1893 – 1984. Suitable seismic factors will be 

taken while designing the various components of the project.

9.2.6 Catchment Area 

107 



The catchment area of Ringpi Chhu up to the dam site is 126 sq km. It is heterogeneous 

in terms of climate, soil, landuse and vegetation. The entire area is covered with very 

deep valleys and steep hills with varying elevations. The hills consist of summits and 

ridges; slide slopes, narrow valleys, cliffs and precipitous slopes. In certain places the soil 

is shallow with huge formation of rocks covering the entire hillock. 

9.2.7 Drainage Pattern 

Ringpi Chu rises as Jumthul Chu from Jumthul Phuk glacier at the base of Siniolchu peak 

(6,888 m). Ringpi Chu is formed by two streams originating at high altitudes having 

snow/glacier catchment in their upper reaches from Jumthul Phuk glacier. Along its 

eastward course, Jumthul Chu is joined by Kishong Chu on its left bank to form Ringpi 

Chhu (Fig 9.3). Kishong Chu rises in the northern part of the catchment and drains at 

Kishong chho, a glacial lake and contributes significantly to Jumthul Chu. Jumthul Chu 

descends from an altitude of 4,000m to 2,940m upto dam site, within a distance of about 

7.5 km with a gradient of 140m/km. 

9.2.8 Land Use Pattern 

The landuse/landcover pattern within the 7 km radius of the proposed Ringpi 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 

first level classified landuse/landcover map generated from these two scenes coupled 

with ground truthing is given in Figure 9.6. Area covered by various landuse/lancover 

categories is given in Table 9.1 and the percent representation of each of the 

landuse/landcover type is shown in Figure 9.7. From the studies it is clear that the 

vegetation of the area concerned is typically that of high altitude Himalayan region. The 

predominant landuse of the area is a mixture of forests, alpine scrub, rockyland, rockfalls, 

moraines and snow and ice cover. The dense mixed forests, which are poorly represented

108 



in the catchment above dam site are restricted to a few patches on the two axes of 

Kishong Chhu and Jumthul Chhu. These dense forests occupy right and left bank slopes 

of the two streams, respectively. Overall the dense mixed forests occupy the lower 

portion of the catchment downstream of the dam site constitute about 24% of the land 

area, while alpine/ open scrubs constitute 19% of the total land area. Rockylands and 

rockfalls in the catchment cover an area of about 2190 ha (11%) of land. Similarly, large 

areas in the catchment are either under permanent ice cover/glaciers (9%) or snow cover 

(21%). In addition there are glacial moraines present in this part of the catchment which 

constitutes about 8% of the land area. There are no human habitation sites or any 

managed ecosystems like agricultural fields, etc. Entire area is covered by natural 

ecosystems and the landscape conditions in the area are also quite natural without any 

human disturbance. The dense forests are present along lower reaches of Jumthul and 

Khishong Chhu in the north. Towards southeast and southwest the forests are represented 

by Tolung Reserve Forest. These forests are mostly broad-leaf forests with occasional 

representation of bamboo in them, particularly in the warmer areas. The areas above 

these dense mixed forests are represented by alpine/open scrub type of vegetation. 

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

radius of Ringpi H.E. Scheme 

Landuse/landcover Area (ha) 

Dense Mixed Forest 4699.35 

Alpine Scrub 3764.28 

Open Scrub 1554.39 

Rockyland 1067.04 

Rockfalls 1123.60 

Moraines 1506.93 

Ice/Glacier 1850.52 

Snow 4078

9% 

109 



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

radius of the proposed Ringpi H.E. Scheme 

9.2.9 Submergence 

The proposed dam is located at 2,960 m with riverbed level at 2,940m, dam top at 2,970 

m and full reservoir level (FRL) at 2,966 m. The project envisages construction of 40 m 

high dam, above the deepest foundation level, which would eventually result in 

inundation of 12.7 ha of land. The spread of reservoir is indicated in Figure 9.8. The 

predominant landuse in the submergence area is dense mixed forest (57%), followed by 

dense/ open alpine scrub (42%). The proposed project does not involve inundation of any 

village or human habitation. 

9.3 BIOTIC ENVIRONMENT 

9.3.1 Vegetation 

8% 

21% 

6% 

5% 

Dense Mixed Forest Dense Alpine Scrub Open Scrub Rockyland 

Rockfalls Moraines Ice/Glacier Snow 

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 

8% 

24% 

19%

110 



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 is found in Sikkim. 

9.3.2 Flora 

The dam site is located in alpine montane terrain and the area here is mostly barren with 

thin vegetation cover. However, other areas in the vicinity of the project are comprised of 

dense mixed forests along the river course and alpine and open scrub high up on the 

slopes. This area experiences cool summers and severe cold winters. Owing to good 

moisture conditions and cool temperatures throughout the year at these altitudes the 

vegetation is constituted mostly by the cold temperate evergreen plant species in lower 

reaches and alpine scrub vegetation in upper parts. The forests are mostly confined to 

lower slopes in the river valley and are represented by all the physiognomic forms – trees, 

shrubs and herbs. The woody elements in these mixed forests are represented by 

Rhododendron, Litsea doshia, Neolitsea sp., Prunus cerasoides and Quercus lineata, 

Euonymous pendulus, Lyonia ovalifolia, Macaranga denticulata and Rhamnus virgatus. 

These species are commonly met with in these riverine dense forests. In the higher slopes 

where scrub vegetation dominates species of Rhododendron, Salix, Viburnum and several 

members of Rosaceae and Ericaceae are seen growing predominantly in the region. The 

alpine meadows harbour several species of Primulaceae, Gentianaceae, Papavaraceae, 

Brassicaceae, Poaceae and Juncaceae. These areas harbour some of the important 

endemic and endangered medicinal plant species of Himalaya. Among these species 

Artemisia vulgaris, Podophyllum hexandrum, Aconitum spp., Saussurea spp., 

Nardostachys jatamansi, Picrorrhiza kurroa and Meconopsis spp. are noteworthy. 

9.3.3 Fauna and Wildlife 

As the project site falls within the Kanchendzonga National Park, there is a rich diversity 

of wildlife in and around the project site. The upper part of catchments of Ringpi chu and 

Tolung (Rangyong) chu harbour several faunal species like Himalayan brown bear

111 



(Selenarctos thibetanus), Great Tibetan sheep, Snow leopard (Panthera uncia), Bharal, 

Himalayan tahr (Hemitragus jemlahicus), Hoary-bellied squirrel (Callossciurus 

pygerithrus), Orange-bellied squirrel (Dremomys lokhriah), Assamese macaque (Macaca 

assamensis), Himalayan palm civet (Paguma larvata) and Stone marten (Martes foina). 

The upper reaches, i.e. the alpine areas of the catchment harbour mammalian species, 

which include Nayan, Bharal, Snow leopard, bear, Himalayan tahr, Barking Deer, 

Himalayan marmot and pikas. These animals however are not known to come down to 

lower altitudes i.e. 2,200 m or below. Among the various faunal species present in the 

catchment Panthera uncia, P. pardus, Neofelis nebulosa, Felis bengalensis, Macaca 

assemensis 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 

Fish fauna of the river is comprised mainly of snow trout and minor trouts. Some of the 

probable fish species of the area are Salmo trutta fario, Schizothrax richardsoni, 

Schizopyge progastus, Anguilia bengalensis, Pseudechensis sulcatus,Labeo pangusia, 

Glyptothorax sp. 

9.4 Existence of any Protected Area/Archaeological Sites 

The proposed project lies within the Kachendzonga National Park on its southeastern 

boundary. There is Tolung Gompa within the 7.0 km radius of the project. However, 

there are no sites or monuments of archaeological or national importance, which would 

be affected by the project activities directly or indirectly. 

9.5 PREDICTION OF ENVIRONMENTAL IMPACTS 

Based on above baseline data and project features, the potential impacts that are expected 

as a result of the proposed project are summarized as follows:

9.5.1 Impacts on land environment 

112 



Sufficient land would be required for the proposed project out of which 12.7 ha would 

come under submergence. The acquisition of land for various project activities would 

also lead to cutting of vegetation on these lands. With the acquisition of forestland, the 

local population, dependent on these forests, might get affected. Most of the 

environmental impacts resultant of construction work is temporary in nature rarely lasting 

beyond the construction period. All these issues are to be properly addressed so that the 

long-term effects, if any, can be minimized. 

9.5.2 Impacts on Water Environment 

The construction of a reservoir replaces the river eco-system by a lacustrine ecosystem. 

The vector of various diseases breeds in shallow areas not very far from reservoir 

margins. The breeding site for mosquitoes and other vectors in impounded water is in 

direct proportion to the length of the shoreline. The construction of the reservoir would 

increase the shoreline many times as compared to the pre-project shoreline of various 

rivers and tributaries under submergence. Thus the construction of the proposed 

reservoir may enhance the potential breeding sites for various disease vectors. 

9.5.3 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. 

9.5.4 Impacts on flora and fauna 

Due to construction of dam about 12.7 ha of 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. This may alter the local diversity of flora and also 

affect habitat available for fauna. Changes to, or loss of habitat will affect areas used for

113 



mating, breeding, nursing, moulting, feeding, and drinking for both resident and 

migratory wildlife. 

The extent and severity of these effects will vary according to the existing habitat and 

the particular species involved which would be known after detailed study is done on 

flora and fauna during the comprehensive EIA/EMP study and suitable mitigation 

measures would be formulated and implemented in consultation with the State Forest 

Department of Sikkim. 

9.5.5 Impacts on Avifauna 

The construction of the proposed dam will lead to formation of a reservoir, which will 

have a fluctuation in the water level, which precisely means the reservoir bank will 

remain wet throughout the year. Due to such reasons, some aquatic 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. 

9.5.6 Impacts on Fishes 

A dam will fragment and isolate upstream resident fish. The resident species may 

congregate in the tail water release site. Fish from upstream will occasionally sweep 

downstream during the monsoon, stay in the tail water or swim further downstream. A 

dam may obstruct the route of the long and mid-distance migratory fish. There may be an 

impact on the fish composition due to construction of dam. A detailed fishery study 

would be conducted during the EIA/EMP study to determine the likely impacts and 

suitable mitigatory measures would be adopted.

114 



9.6 Impacts on Socio-Economic Environment (Resettlement & Rehabilitation) 

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

coming under submergence. 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 socio-economic 

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. 

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.

115 



Based on the assessment of environmental impacts, following management plans will be 

formulated: 

Catchment Area Treatment 

Compensatory Afforestation 

Wildlife Conservation 

Resettlement and Rehabilitation 

Public Health Management System 

Muck Disposal 

Fishery Management 

Restoration of Construction Area 

Green Belt Development 

Free Fuel Provision 

Disaster Management



CHAPTER – X 

INFRASTRUCTURE

CHAPTER – X 

INFRASTRUCTURE 

10.1 EXISTING ACCESS AND INFRASTRUCTURE FACILITIES 

10.1.1 Road Communication 

122 



The project is approachable from Mangan to lingza road. The dam site is located just d/s 

of confluence of Jumthul chu and Kishong chu near the place called Tolung and is 

approachable by a foot path 17 Km from Lingza the road head . The Power house is 

located on the right bank of Ringpi Chu near the Place called Ishana . The Powerhouse 

is approachable from Lingza by a footpath of 6.0 km from the road head. Lingza is 17 

Km from Magan, the head quater of North Sikkim District of Sikkim, 62 Km from 

Singtam (NH31A), 162 Km from NJP railway station and 163 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 road are being maintained by state PWD. 

10.1.2 Housing And Community Facilities 

Ishna is the name of the place near to powerhouse and Tolung to Dam site where even 

basic facilities of health care, schooling, market, postal and telephone etc. are not 

available. It is therefore necessary to plan housing, office, recreation, store etc. for 

meeting the requirement of the project. 

10.1.3 Power Availability 

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 Chukha 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

123 



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 Mangan. Therefore , the necessary construction power shall be 

available for the execution of Ringpi H.E. Project from some where nearby Mangan but 

the exact location may be decided at the time of FR/DPR. 

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 Ringpi H.E. Project has been worked out. 

10.2.1 Improvement Of Existing Road And Bridges 

The Powerhouse is located near the place called Ishana. The state highway having a 

length of 17 km from Sanklan to Lingza connects the power house by a foot path of 6 

Km and dam site by a foot path of 17 Km. Since the Ringpi H.E. Project is on u/s of the 

Lingza H.E. Project, therefore it has been presumed that all the roads and bridges shall be 

ready upto damsite of Lingza H.E. Project. 

10.2.2 Construction Of Roads & Bridges 

The power house shall be approached from Mangan - Lingza road from left bank for 

which a new project road of 3.0 Km is to be constructed from the dam site of Lingza 

H.E. Project. The Dam site shall be approached from right . 

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 for Power house 

shall be Ishana at and for dam site near Tolung 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

124 



project has been worked out. Each personal would be provided with the accommodation 

as per the entitlement. Keeping in view the construction period and subsequent operation 

and maintenance of the project, it is proposed to construct about 50% of the buildings as 

the permanent and the remaining as temporary. This conclusion has been drawn on the 

basis that 50% of the staff strength would be required for maintenance and operation after 

the completion of the project. 

Requirement of built up accommodation has been worked out to 2148 Sq.m of permanent 

built up area and 2206 Sq.m of temporary builtup area would be required. Total plinth 

area for residential accommodation worked out to be 4354 Sq.m, 

10.2.4 Accommodation For Non-Residential Purposes 

The office complexes are proposed at Ishana and Tolung. Workshops, laboratories, 

stores, water supply, fire stations, electrical substations etc would be accommodated in 

the project area.. One 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 7166 

Sq.m of which about 50% would be permanent and rest will be temporary. 

10.3 TELECOMMUNICATION FACILITIES 

The different work sites of the project, offices, stores, laboratories, workshop and 

residences would be connected through a telecommunication network. The 

telecommunication facilities would also be provided between the projects and outside. 

Therefore, an internal telephone exchange would be provided at the project for 

communication within and outside the project. Most parts of Sikkim are presently 

connected with different parts of the world through satellite telecommunication network

125 



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 

The construction power for the project shall be available at the time of construction of 

the project and it is presumed that till the time some mega projects in the d/s i.e. Teesta 

(V), Teesta(III) and Teesta(IV) would have been commissioned and a transmission line 

of about 20Km may be required for arranging construction power.



CHAPTER – XI 

CONSRUCTION PLANNING & 

SCHEDULE


CHAPTER –XI 

CONSTRUCTION PLANNING & SCHEDULE 

126 



The Equipment Planning & Construction Methodology of Ringpi H.E. Project (2x35 

MW) in Teesta Basin Sikkim has been developed on following consideration. 

1. The project construction period has been considered as four years after 

completion of Stage I & II activities. 

2. Available Geological Data at PFR stage. 

3. Requirement of Construction Equipment has been planned to handle the quantities 

worked out on the basis of preliminary layout. 

4. Five months (May to September) rainy season has been considered while 

planning surface works. 

11.2 CONSTRUCTION METHODOLOGY: 

11.2.1 Infrastructure Works: 

The main infrastructure development is proposed to be carried out in period of 12 

months. During infrastructure period Land Acquisition, construction of approach roads, 

bridges& culverts, arrangement of construction power will be undertaken. Critical 

component of project would be started from 5 th month after construction of approach 

roads. Platform to accommodate batching plant, stores for construction material, site 

workshop, offices and other buildings (residential/ non residential) colonies will also be 

developed in infrastructure period. Crawler Dozer, Loader cum Excavator, Air 

compressor, Road Roller etc. are proposed for deployment during infrastructure stage. 

11.2.2 Diversion of River 

The construction of diversion tunnel 3.3 m finished dia., Horse shoe shaped 400 m long 

would be carried out by full face method. Excavation of Diversion Tunnel will be carried 

out by deploying single Boom drill jumbo, Jack hammers, 1.0 cum Conway mucker &

127 



10 T Tippers.. Excavation & concreting of diversion tunnel would be completed in 10 

months. The concreting equipment proposed are Concrete pump, Transit mixer, shotcrete 

machine, Grout pump, shutters etc. Concreting requirement would be catered by the same 

batching & mixing Plant and Aggregate processing Plant, being proposed for Dam . U/s 

& D/s Coffer dam would be constructed immediately after construction of diversion 

tunnel in 2 months to divert the river. River bed excavation would be taken up after 

completion of coffer dam. 

11.2.3 Concrete Dam 

Dam abutment stripping is proposed to be carried out in 13 months. The excavation of 

river bed & foundation treatment would be carried out in 3 months. Excavated material 

will be handled by 1.0 cum Hyd. Excavator and 10T Tippers/20 T Dumpers. Concreting 

of Dam & HM work would be carried out in further 23 months. Concreting would be 

done by deploying 2 Nos. Tower crane (4.5 T at 60 m radius), 1 No. 80 cum/hr 

Batching& Mixing plant and 150TPH Aggregate Processing plant. 

11.2.4 Intake Structure, Desilting Chamber , Silt Flushing tunnel & HRT 

Initially excavation of adits & approaches would be carried out in 4 months. 

Thereafter,1 No. Intake structure having gate size of 3.3 m x3.3m, 1 No. Dufour type 

Desilting chambers of size 50m X6mX9m and HRT of 3.3 m dia. would be excavated in 

24 months . Excavation of Desilting Chamber would be taken up from intake structure. 

Intake tunnel would be extended upto full length of Desilting Chamber. Thereafter it will 

be expanded side wise to the full width of desilting chamber resulting in desilting 

chamber dome. Mucking of excavated material would be done through the tunnel. After 

the excavation of desilting chamber, concreting will be carried out. Excavation of silt 

flushing tunnel & gate operation chamber would be a parallel activity. The equipment to 

be deployed are Jack hammers, wagon drills, air compressors, skid steer loader, tippers, 

concrete pump, transit mixers etc.

128 



Excavation of 7.0 km long, 3.3 m finished diameter horse shoe shaped Head Race Tunnel 

is proposed by full face drilling & blasting method. It will be excavated through 3 nos 

adits. Excavation would be carried out by deploying three set of equipment i.e single 

boom drill jumbo, 1.0 cum Conway mucker and 10 T tipper. Concreting will be carried 

out by deploying concreting equipment i.e. Concrete pump, Transit Mixer etc. Concreting 

requirement would be catered by Batching & Mixing Plant & aggregate processing plant 

installed at dam site. 

11.2.5 Surge Shaft : 

For Construction of 10m diameter, 40 m high Surge Shaft, an approach to surge shaft top 

would be constructed in four months. After the completion of approach, Excavation of 

surge shaft would be carried out manually in 16 months. Excavation would be carried out 

with the help of Jack hammers, motorized winch 10 T capacity etc.. Mucking will be 

done from the top. Concreting would be completed employing 2 m shutter, concrete 

pump, Transit Mixer & 30 cum/hr batching &mixing plant . Construction of surge shaft 

would be completed in 28 months. 

11.2.6 Pressure Shaft: 

Initially construction of approaches & adit would be done in 4 months. One no. 1300 m 

long 1.6 m dia. inclined pressure shaft, will be excavated in the same way as surge shaft 

by deploying Jack hammer, Motorized winch etc. However two nos. intermediate adit 

would be used to handle the muck. Steel liner erection & concreting will be carried out 

by deploying 10/20 t winches, Slipform liner etc. Construction of Pressure shaft would 

take around 31 months. 

11.2.7 Power House 

2 X 35 MW (70MW) underground power house (72 m X 18 m X 29 m size), 

Transformer Cavern & MIV would be excavated in 17 months. For excavation of Power 

House a construction adit would be excavated up to the crown of power house. Main

129 



access tunnel would also be excavated simultaneously. Construction adit would be 

extended up to full length of power House. Thereafter it will be expanded side wise to 

the full width of power house resulting in Power House Cavern. Mucking of excavated 

material would be done through the Construction adit. From Power House Cavern 2 

shafts of 2.0 m diameter would be excavated up to the bottom level of draft tube followed 

by benching of Power House cavern up to the bottom of Power House. Mucking will be 

carried out through Main access Tunnel/TRT. The equipment to be deployed for 

excavation are jack hammers, wagon drills, air compressors, loader, excavators, tippers, 

winches etc. Concreting of Powerhouse would be carried out in 20 months with the help 

of concrete pump, transit mixer etc. Concreting requirement would be catered by 

deploying 30 cum/hr batching & mixing plant and 50 TPH aggregate processing plant. 

Power house Installation & Testing of Machine would be undertaken in such a manner 

that Project get commissioned in 48 th month from the start of Project construction. 

11.2.8 Tail Race Tunnel: 

1 Nos. 250m long horse shoe shaped Tail Race Tunnel having 3.3 m finished diameter 

will be excavated by full face method. Excavation of Tail Race Tunnel would be carried 

out with single boom Drill Jumbo, Wagon drill, Conway mucker , 10 t tipper etc. The 

TRT will be excavated from 5 th month & will be completed in further 6 month. After the 

excavation of power house the TRT will be concreted with the help of concrete pump, 

Transit mixer, Batching & mixing plant & aggregate processing plant ( installed at Power 

house). 

11.3 CONSTRUCTION SCHEDULE 

The schedule for stage I & II activities upto CCEA clearance and construction schedule 

has been prepared in the form of bar chart and placed as annexure –11.1 & 11.2 

respectively.

S. No. 

Details of works 

1 Preparation of stage-I activity estimates 1 

2 Data collec./ application for clearance from MOEF 

3 MOEF clearance 1 

4 Essent. Temp. infra./access 6 

5 Estab. of G&D sites, Metrological 

obser. And Hydrological measurement 

6 Essential Geological & Geo-physical 

exploration, Topographical surveys 

7 Formulation of Feasibility Report, 

preparation of estimate for st-II activities 

8 EIA / EMP studies 15 

9 Commercial viability from CEA 1 

10 Vetting & sanction of st-II activity estimates 1 

11 Detailed Topogr./Geological/Hydro 

metero. & Construction material survey 

12 MOEF clearance 3 

13 Const. of resid./non resid. buildings,roads 

bridges and arrangement of const. Power 

14 Preparation of Detailed Project Report 

and its submission 

Duration 

15 Techno Economic Clearance 3 

16 Pre PIB delibrations 1 

17 PIB Clearance 1 

18 CCEA Clearance (Investment Sanction) 1 

2 

24 

11 

14 

14 

19 

14 

SCHEDULE FOR STAGE-I&II ACTIVITIES (UP TO CCEA CLEARANCE) 

MONTHS 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 

*This schedule is in accordances with three stage clearance policy of Ministry of Power ,Govt. of India vide no. 16/31/2000-DO(NHPC) dated 8/6/2001 

129 

Annexure-11.1 

Contd. 

Contd. 

Zero date for 

Construction



CHAPTER – XII 

COST ESTIMATE

CHAPTER –XII 

COST ESTIMATES 

132 



PRELIMINARY COST ESTIMATES FOR CIVIL, HYDRO-MECHANICAL, 

ELECTRO-MECHANICAL AND TRANSMISSION WORKS 

The estimate has been prepared to arrive at the capital cost of Ringpi H.E. Project and is 

of Pre-feasibility level of accuracy. The base date of the estimate is June 2003 Price 

Level and the cost is expressed in Indian Rupees. The Cost Estimate is divided into 

Civil, Electrical and Transmission Works. For Civil Works, the sub heads are as under: - 

12.1 I-WORKS 

Under this head, provision has been made for various components of the Project as 

detailed hereunder. 

A-PRELIMINARY 

Under this head, provision has been made for all surveys and investigations to be 

conducted to arrive at the optimum of the project components. 

B-LAND 

This covers the provision for acquisition of land for construction of the project colonies, 

offices and stores and compensation for trees and standing crops etc. 

C-WORKS 

This covers the cost of Diversion Tunnel , Coffer and Concrete Dam and Spillway along 

with associated hydro-mechanical equipment.

J-POWER PLANT CIVIL WORKS 

133 



This covers the cost of project components viz. Intake Structure, Headrace Tunnel, Power 

House and Transformer Cavern, Pressure Shaft, Surge Shaft, Tail Race Tunnel and other 

appurtenant works. 

The quantities indicated in the estimates for C - Works & J-Power Plant Civil Works 

(Civil & HM) are calculated from the Preliminary Engineering Drawings and as per 

experience of other on-going or commissioned projects. A provision has been made for 

contingencies. 

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 

Under this head provision for both residential and non-residential have been provided. 

Under the permanent category only those structures are included which will be 

subsequently utilized during the operation and maintenance of the project utilities. The 

costs are worked out on plinth area basis prevalent in the area for the type of construction 

involved. 

O-MISCELLANEOUS 

Provision under this head has been made for C & J works for the Capital & running cost 

of Electrification, Water Supply, Sewage disposal, Fire fighting equipments, Medical 

assistance, Recreation, Post Office, Telephone and Telegraph Office, etc. also the 

Provisions are made for the Security arrangements, inspection vehicles, schools, transport 

of labour, Laboratory testing, R&M of Guest House and transit camps, Community 

center, Retrenchment compensation, photographic instruments as well as their R&M 

charges etc.

134 



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 vehicles 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 cost of roads and bridges are based on the prevalent 

rate structure prevalent in the area of the Project, for the type of construction involved. 

X-ENVIRONMENT AND ECOLOGY 

Provision under this head has been taken as 2% of I Works towards Bio-diversity 

Conservation, Creation of Green belt, Restoration of Construction Area, Catchment Area 

Treatment, Compensatory Afforestation etc 

12.2 II-ESTABLISHMENT 

Provision for establishment has been made at 8% of I-works minus B-Land for civil 

works. 

12.3 III-TOOLS AND PLANTS 

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 

135 



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 provision, estimated recoveries by way of resale or transfer of equipment used 

in infrastructure works are provided for @ 75% of value booked under head Q-Special 

Tools and Plants. Also, the provision for recoveries on account of resale of DG Set and 

temporary buildings have been considered. 

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.

136 



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 4.91 

B - Land 13.86 

C - Works 93.05 

J - Power Plant Civil Works 159.34 

K - Buildings 9.34 

O - Miscellaneous 7.75 

P - Maintenance 2.93 

Q-Special Tools & Plants 2.84 

R - Communication 31.19 

X - Environment & Ecology 6.77 

Y - Losses on Stock 0.73 

Total of I-Works 332.72 

II - Establishment @ 8% of cost of I-Works less B-Land 25.51 

III - Tools and Plants @ 1% of cost of I-Works 3.33 

IV - Suspense 0.00 

V - Receipt & Recoveries (-) -2.06 

TOTAL DIRECT CHARGES 359.50 

2. INDIRECT CHARGES 

a) Capitalised Value of Abatement of Land Revenue 0.17 

b) Audit and Account Charges @1% of cost of I-Works 3.33 

TOTAL INDIRECT CHARGES 3.50 

TOTAL OF DIRECT & INDIRECT CHARGES 363.00 

ABSTRACT : 

A Civil Works 363.00 

B Electrical Works 83.88 

C Transmission Works 19.16 

TOTAL COST 466.04 

C IDC 53.23 

D Total Cost With IDC 519.27

Sl 

No. 

1 Prefeasibility 

1.1 Expenditure for preparation of 

Prefeasibility Report 

2.0 Preparation of Detailed Project Report 

2.1 Detail survey for final location of project 

componenets. 

2.2 Aerial survey, contour survey for reservoir 

basin including establishment of permanent 

benchmarks. 

2.3 Geological and geophyical surveys and 

investigation 

137 



A- PRELIMINARY 

Description of Work Unit 

Rs. In lakhs 

Qty Rate Amount 

LS 14.00 

LS 25.00 

LS 20.00 

I) Drifting M 500 0.10 50.00 

ii) Geophysical LS 15.00 

iii) Core drilling M 300 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 

testing 

2.6 Investigation for availability of 

construction materials. 

2.7 Construction of access roads to facilitate 

investigations 

LS 6.00 

LS 3.50 

LS 7.00 

2.8 Model experiment. LS 8.00 

2.9 Computer 

facilities. 

and telecommunication LS 3.00 

2.10 Vehicles for inspecting officers for site 

investigations 

LS 20.00 

2.11 Camping equipment LS 2.00 

2.12 Preliminary soil test, establishing soil 

testing laboratory. 

LS 6.00

2.13 Consultant’s fees including charges for 

preliminary design work or device 

2.14 Training of engineers during investigation 

and preparation of project reports 

138 



LS 15.00 

LS 6.00 

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 

Total( II) 250.50 

3.0 Pre-Construction Stage Investigations 

3.1 Topographical Surveys LS 15.00 

3.2 Geological Investigation 

i) Diamond Core Drilling M 150.00 0.1 15.00 

ii) Exploratory Drift M 150.00 0.1 15.00 

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 2.00 16.00 

3.4 Meteorological Data Collection 2 sites for 

4 years 

3.5 Construction material survey 

Year 8.00 0.40 3.20 

i) Topographical Survey LS 5.00 0.1 0.25 

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 15.00 

3.7 Seismological data collection for 4 years Year 4.00 1 4.00 

3.8 Survey for layout of colonies and roads 

I) Residential-cum-Office accomodation Sqm. 2.00 0.5 1.00 

ii) Batching Mixing Plant and Workshop Sqm. 1.00 0.5 0.50 

iii) Project and quarry site road Sqm. 0.50 0.5 0.25 

3.9 Workcharged establishment for unforseen 

works 

Year 4.00 2 8.00

4.0 Design & Consultancy 

4.1 Cost of Design Establishement including 

procurement of printing stationery and 

preparation of Completion Report, History 

of Project etc. 

139 



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 20.00 

Total (III) 226.95 

Grand Total 491.45

Sl. 

No. 

140 



B-LAND 

Rs. In lakhs 

Description Qty. Rate Unit Amount 

1.0 Private land Requirement 

Permanent residential and non residential 

buildings 

3.00 5.50 Ha 16.50 

Diversion tunnel 2.00 5.50 Ha 11.00 

Submerged in the reservior area 27.00 5.50 Ha 148.50 

Construction of dam/ wier 8.00 5.50 Ha 44.00 

Construction material 2.50 5.50 Ha 13.75 

Construction of approach Roads 74.00 5.50 Ha 407.00 

Power house 2.00 5.50 Ha 11.00 

Construction of adits 3.00 5.50 Ha 16.50 

Switch Yard 1.50 5.50 Ha 8.25 

Surge Shaft 1.00 5.50 Ha 5.50 

Land for Misc Purpose 1.00 5.50 Ha 5.50 

Sub Total (1) 

2.0 Forest land 

125.00 687.50 

River bed 10.00 0.00 Ha 0.00 

Underground 4.00 0.00 Ha 0.00 

Sub total (2) 

3.0 Other Compensation 

14.00 0.00 0.00 

i) Cost of crops standing on cultivated land 

required @ 30% of cultivated land 

80 1.65 Ha 132.00 

ii) Compensation for trees LS 10.00 

iii) Compensation for relocating electric and 

telephone poles 

2.00 

iv) Crop Compensation for submergence LS 200.00 

Sub total (3) 344.00 

4 Land on lease/ hire for 4 Years 

Dumping area 0.50 2.40 Ha 1.20 

Dumping area for batching and mixing 0.50 2.40 Ha 1.20 

plant 

Temporary Residential and Non- 

Residential buildings 

2.00 2.40 Ha 4.80 

Contractors Colony 2.00 2.40 Ha 4.80 

Contractors Construction facilities 2.00 2.40 Ha 4.80

141 



Railway Siding Facilities 1.00 2.40 Ha 2.40 

Electro - Mechanical Works 1.00 2.40 Ha 2.40 

Hydro -Mechanical Works 1.00 2.40 Ha 2.40 

Total (4) 24.00 

Total (1+2+3+4) 1055.50 

Interest charges on account of award for the 

period taking over possession of land and 

date of award @ 12% per year of 25% cost 

of land acquisition for two years 

41.25 

Solatium charges for compulsary 

acquisition of land @ 30% of the cost of 

private land 

Provision for legal charges @ 1% on total 

compensation 

Labour and material required for 

measurement and demarcation of land and 

properties @1% of land acquision 

Establishment charges @ 6.25% of cost of 

total compensation 

206.25 

10.555 

6.875 

65.97 

Total 1386.40

ABSTRACT OF COST OF C - WORKS 

142 



S. N. Description Amount (Rs. In Lakhs) 

Civil HM Total 

1. River Diversion Works 346.95 30.56 377.51 

2. Coffer Dam 648.22 648.22 

3. Concrete Dam 5055.33 5055.33 

4. Spillway & Plunge Pool 2599.91 441.95 3041.86 

Total 8650.42 472.50 9122.92 

Add works tax @ 2% 173.01 9.45 182.46 

GRAND TOTAL 8823.42 481.95 9305.37

S. 

No. 

DIVERSION TUNNEL 

Description Unit Quantity Rate in 

Rs 

143 



Amount 

( Rs. in 

Lakhs) 

1 Surface Excavation 

1.1 Common excavation Cum 15,000 125 18.75 

1.2 Rock excavation Cum 2,500 300 7.50 

2 Underground excavation Cum 6,700 1000 67.00 

3 Rock Support System 

3.1 Rock bolts M 4,500 400 18.00 

3.2 Steel Supports T 40 42000 16.80 

3.3 Shotcreting Cum 450 4000 18.00 

3.4 Concrete lagging Cum 100 7000 7.00 

4 Concrete 

4.1 Cement concrete lining M-20 Cum 1,250 4000 50.00 

4.2 M15 Cum 1,000 2930 29.30 

4.3 M20 Cum 100 3390 3.39 

4.4 M25 Cum 1,000 3610 36.10 

5 Reinforcement Steel T 100 27000 27.00 

Sub Total (A) 298.84 

6 Miscellaneous and Ancillary 

Works 

6.1 Various Miscellaneous works like 

wire mesh/steel fibre reinforcement, 

drilling & grouting, PVC pipes for 

drainage, slope protection works 

etc.(7% - 8% of Sub Total (A) 

depending upon the site conditions & 

7.50% 22.41 

type of structure) 

Sub Total (B) 321.25 

7 Instrumentation 1% of Sub -Total (B) 1% 3.21 

8 Dewatering 2% of Sub -Total (B) 2% 6.43 

9 Contingencies 3% of Sub -Total (B) 3% 9.64 

10 Work Charged Establishment 2% of 

Sub -Total (B) 

2% 6.43 

Total 346.95

S. 

No. 

COFFER DAM 

DESCRIPTION UNIT QTY. Rate in 

Rs 

144 



Amount 

(Rs. in 

Lakhs) 


1.1 Common Excavation Cum 45,000 125 56.25 

2 Embankment Construction 

2.1 Earth / rock fill Cum 25000 518 129.50 

2.2 Impervious core Cum 11000 354 38.94 

2.3 Filter Cum 2500 901 22.53 

3 Concrete 

3.1 Concrete cut-off wall Sqm 1,750 20000 350.00 


4 Miscellaneous 

4.1 Various Miscellaneous works like, 

drilling & grouting etc.(0.0% - 0.5% 

of Sub Total (A) depending upon the 

site conditions & type of structure) 

0.50% 2.99 






2% 12.00 

Total 648.22

S. 

No. 

CONCRETE DAM 


Rs 

145 



Amount 

(Rs. in 

Lakhs) 



1.2 Rock Excavation Cum 25,000 300 75.00 


2.1 Rock bolts M 1,500 400 6.00 

2.2 Shotcrete Cum 500 4000 20.00 

3 Concrete 

3.1 M10 Cum 500 2560 12.80 

3.2 M15 Cum 120,000 2930 3516.00 

3.3 M20 Cum 15,000 3390 508.50 

3.4 M25 Cum 5,000 3610 180.50 




Works 


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% - 

3% of Sub Total (A) depending upon 

the site conditions & type of 

2.50% 113.12 

structure) 







2% 92.76 

Total 5055.33

S. 

No. 

SPILLWAY 


Rs 

146 



Amount 

(Rs. in 

Lakhs) 



1.2 Rock Excavation Cum 3,000 300 9.00 

2 Concrete 

2.1 M15 Cum 30,000 2930 879.00 

2.2 M20 Cum 2,000 3390 67.80 

2.3 M25 Cum 22,000 3610 794.20 

3 Reinforcement Steel T 2,000 27000 540.00 

4 Structural Steel T 150 42000 63.00 



Works 


drilling & grouting, PVC pipes, water 

stops, other steel works, slope 

protection works, bridge etc.(1% - 



structure) 

1.50% 35.58 







2% 48.15 

Total 2599.91

J -POWER PLANT APPURTENANCES (CIVIL WORKS) 

147 



S. Description Amount (Rs. in Lakhs) 

NO. Civil HM Total 

1 Intake Structure 351.45 100.70 452.14 

2 Desilting Chambers (Including S.F.T.) 236.41 63.63 300.04 

3 Adits 1533.20 16.07 1549.26 

4 Head Race And Tail Race Tunnel 4676.51 12.60 4689.11 

5 Surge Shaft 549.14 23.84 572.98 

6 Pressure Shafts And Penstocks 755.22 1771.35 2526.57 

7 Power House Complex 5007.41 5007.41 

8 Switchyard 523.74 523.74 

Total 13633.08 1988.18 15621.25 

Add works tax @ 2% 272.66 39.76 312.43 

GRAND TOTAL 13905.74 2027.94 15933.68

S. 

No. 

INTAKE STRUCTURE 


Rs 

148 



Amount 

(Rs. in 

Lakhs) 

1.0 Surface Excavation 



2.0 Underground excavation Cum 2,000 1000 20.00 

3.0 Supports System 

3.1 Rock bolts M 750 400 3.00 

3.2 Steel ribs Support T 15 42000 6.30 


3.4 Concrete Lagging Cum 75 7000 5.25 

4.0 Concrete 

4.1 M15 Cum 500 2930 14.65 

4.2 M25 Cum 4,000 3610 144.40 

5.0 Reinforcement Steel T 400 27000 108.00 


6.0 Miscellaneous and Ancillary 

Works 


drilling & grouting, 

wiremeshreinforcement, slope 

protection works, other steel works, 

etc.(1% - 2% of Sub Total (A) 



1.50% 4.85 


7.0 Instrumentation 1% of Sub -Total (B) 1% 3.28 

8.0 Dewatering 1% of Sub -Total (B) 1% 3.28 

9.0 Contingencies 3% of Sub -Total (B) 3% 9.85 

10.0 Work Charged Establishment 2% of 


2% 6.57 

Total 351.45

S. 

No. 

DESILTING CHAMBERS (INCLUDING S.F.T.) 


Rs 

149 



Amount 

(Rs. in 

Lakhs) 






3.1 Rock bolts M 8,000 400 32.00 



3.4 Concrete Lagging Cum 60 7000 4.20 

4 Concrete 

4.1 M15 Cum 1,000 2930 29.30 

4.2 M20 Cum 500 3390 16.95 

4.3 M25 Cum 500 3610 18.05 




Works 


wiremesh/steel reinforcement, 

drilling & grouting works, etc.(3% - 



3.50% 7.40 

structure) 







2% 4.38 

Total 236.41

S. 

No. 

ADITS 


Rs 

150 



Amount 

(Rs. in 

Lakhs) 




2 Underground excavation 

2.1 Excavation of adits Cum 50,000 1000 500.00 

3 Supports System 

3.1 Rock bolts M 30,000 400 120.00 


3.3 Shotcreting Cum 3,000 4000 120.00 

3.4 Concrete lagging Cum 1,000 7000 70.00 

4 Concrete 


4.2 M15 Cum 5,000 2930 146.50 

4.3 M20 Cum 2,000 3390 67.80 

4.4 M25 Cum 2,200 3610 79.42 




Works 




drainage etc.(3% -4% of Sub Total 

(A) depending upon the site 

3.50% 48.01 

conditions & type of structure) 

Sub Total (B) of 1 to 6 1419.63 






2% 28.39 

Total 1533.20

S. 

No. 

HEAD RACE AND TAIL RACE TUNNEL 


Rs 

151 



Amount 

(Rs. in 

Lakhs) 






3.1 Rock bolts M 95,000 400 380.00 



3.4 Concrete lagging Cum 1,700 7000 119.00 

4 Concrete 


4.2 M15 Cum 18,000 2930 527.40 

4.3 M25 Cum 1,000 3610 36.10 




Works 




drainage etc.(7% - 8% of Sub Total 

(A) depending upon the site 

7.50% 302.10 

conditions & type of structure) 







2% 86.60 

Total 4676.51

S. 

No. 

SURGE SHAFT 

DESCRIPTION UNIT QTY. Rate 

in Rs 

152 



Amount 

(Rs. in 

Lakhs) 


1.1 Common Excavation Cum 50000 125 62.50 

1.2 Rock excavation Cum 5000 300 15.00 

2 Underground excavation 

2.1 Surge shaft excavation Cum 5000 1,200 60.00 

2.2 Surge shaft excavation with raise borer Cum 140 1,500 2.10 

2.3 Concrete Lagging Cum 100 7,000 7.00 

3 Support System 

3.1 Rock bolts M 15000 400 60.00 

3.2 Steel ribs Support T 30 42,000 12.60 

3.3 Shotcreting Cum 600 4,000 24.00 

4 Concrete 

4.1 M-20 Cum 4000 3,390 135.60 

4.2 M-25 Cum 1500 3,610 54.15 

5 Steel Works 

5.1 Deformed Reinforcement Steel T 200 27,000 54.00 

5.2 Steel liner T 20 70,000 14.00 



6.1 Various Miscellaneous works like drilling & 

grouting,wiremesh reinforcement, airvent 

pipe, lift arrangement, other steel works 

etc.(1-2% of Sub Total (A) depending upon 

the site conditions & type of structure) 

1.50% 7.51 





10 Work Charged Establishment 2% of Sub - 

Total (B) 

2% 10.17 

Total 549.14

S. 

No. 

PRESSURE SHAFTS AND PENSTOCKS 


Rs 

153 



Amount 

(Rs. in 

Lakhs) 

1 Underground excavation Cum 13500 1200 162.00 


2.1 Rock bolts M 13,000 400 52.00 



3 Concrete 

3.1 M15 backfill concrete Cum 12,000 2930 351.60 


4 Miscellaneous and Ancillary works 


drilling & grouting,wiremesh 

reinforcement, swellex anchors 

etc.(2-3% of Sub Total (A) 



2.50% 17.215 







2% 14.12 

Total 755.22

S. 

No. 

POWER HOUSE COMPLEX 

DESCRIPTION UNIT QTY. Rate 

in Rs 

1 Under Ground Excavation 

1.1 Excavation of PH cavern, transformer cum 

MIV cavern and draft tube gate 

154 



Amount 

(Rs. in 

Lakhs) 

Cum 90,000 1000 900.00 


2.1 Rock bolts M 50,000 400 200.00 



3 Concrete 

3.1 M15 backfill concrete Cum 4,000 2930 117.20 

3.2 Concrete lining M20 Cum 1,700 3390 57.63 

3.3 M25 Cum 40,000 3610 1444.00 

4 Reinforcement steel T 5,000 27000 1350.00 

5 Structural Steel for roof trusses T 250 42000 105.00 

6 Masonry 

6.1 Stone Cum 500 2000 10.00 

6.2 Brick Cum 1500 2000 30.00 



7.1 Various Miscellaneous works like site 

clearance, drilling & 

grouting,wiremesh/steel reinforcement, 

flooring, water fpoffing system, swellex 

anchor, doors, window, painting, lift 

arrangement, architectural works , other 

metal works etc.(4-5% of Sub Total (A) 

depending upon the site conditions & type 

4.50% 199.66 

of structure) 


8 Instrumentation(1% of Sub -Total (B) 1% 46.365 



11 Work Charged Establishment 2% of Sub - 

Total (B) 

2% 92.73 

Total 5007.41

S. 

No. 

SWITCHYARD 


Rs 

155 



Amount 

(Rs. in 

Lakhs) 





2.1 Rock bolts M 1,000 400 4.00 


3 Earthwork in filling Cum 35,000 342 119.70 

4 Concrete 

4.1 M15 Cum 1,500 2930 43.95 

4.2 M20 Cum 1,500 3390 50.85 

4.2 M25 Cum 1,500 3610 54.15 

5 Deformed Reinforcement Steel T 125 27000 33.75 

6 Stone/Brick Masonry Cum 1,000 2000 20.00 

Sub Total (A) of 1 to 6 468.40 



site clearance, PVC pipes, control 

block building works like flooring, 

doors, windowsets including water 

supply and sewerage, boulder 

pitching, metal works, etc.(4-5% of 

Sub Total (A) depending upon the 

site conditions & type of structure) 

4.50% 21.08 




10 Work Charged Establishment2% of 


2% 9.7896 

Total 523.74

S. 

No. 

HYDRO MECHANICAL EQUIPMENT 

Detail of Items Unit Qnty. Rate 

in Rs. 

1 Diversion tunnel gate 

Gate (Fixed wheel type) including ballast (3.3m 

x 4m)- 1 No. 

156 



Amount 

in Lakh 

Rs. 

Ton 16 60000 9.60 

Embedded Parts - 1 Set Ton 5 50000 2.50 

Ropedrum hoist 40 T Capacity-1set Ton 12 100000 12.00 

Hoist Supporting structure and trestle - 1set Ton 10 50000 5.00 

2 Spillway structure 

a) Radial Gates (4m x 9.0m) - 3 Nos. Ton 120 100000 120.00 

b) Embedded Parts (including anchorages, hoist 

structure) including breast wall liners - 3 Set 

Ton 90 50000 45.00 

c) Hydraulic Hoist (One power pack + Two 

cylinders of 50T capacity/cylinder with 

provision of 25% pushing force) 

d) Portable oil filter unit along with 

Contamination checking kit & Low vacuum 

dehydration and degassification unit 

e) Portable trolley mounted gasoline engine 

operated power pack 

f) Spillway Stoplog ( Slide type) including ballast 

4.0m x 9 m -1 Set consisting 3 units 

Set 3 4500000 135.00 

Set 1 500000 5.00 

Set 1 750000 7.50 

Ton 24 60000 14.40 

g) Embedded Parts - 3 Set Ton 21 50000 10.50 

h) Gantry crane 20 T capacity Set 1 2000000 20.00 

i) Lifting Beam-1set Ton 2 50000 1.00 

3 Instruments and Remote Control Set 1 5000000 50.00 

4 D G Set 250 KVA Set 1 1250000 12.50 

5 Intake structure 

a) TrashRacks and Embedded parts (6m x 14m) - 

1 No. 

Ton 25 50000 12.50 

b) Trash rack cleaning machine Set 1 5000000 50.00 

c) Intake gate(fixed wheel type) including ballast 

(3.3m x 3.3m) - 1No. 

Ton 13 60000 7.80 

d) Embedded Parts - 1 Set Ton 4 50000 2.00 

e) Rope drum hoist 25T Cap.-1set Ton 10 100000 10.00 

f) Hoist platform and trestle-1set Ton 5 50000 2.50

g) Bulkhead Gate (Slide Type) including ballast 

3.3m x3.3m - 1 No. 

157 



Ton 6 60000 3.60 

h) Embedded Parts - 1 Set Ton 2 50000 1.00 

i) Rope drum hoist 15T Cap.-1set Ton 5 100000 5.00 

j) Hoist platform and trestle-1set Ton 3 50000 1.50 

6 Desilting Chamber Gates 

a) Desilting Chamber Gate (Slide Type) including 

ballast 3.3m x3.3m - 1 No. 

Ton 6 60000 3.60 

b) Embedded parts - 1 Set Ton 2 50000 1.00 

c) Rope drum hoist 15T Cap. Including Hoist 

flatform-1set 

Ton 7 100000 7.00 

7 Silt Flushing Gates (Slide Type) 

a) Gates (Service & Emergency) 1.5m x1.5m - 2 

Nos. 

Ton 4 100000 4.00 

b) Embedded parts (including bonnet, bonnet 

cover,gate body liner etc.)-2Set 

Ton 34 50000 17.00 

c) Hydraulic Hoist 65T Cap. (Two Double acting 

cylinder and one power pack) 

Set 1 2800000 28.00 

8 Surge shaft gate 

a) Gate(Slide Type) 3.3m x 3.3m - 1 No. Ton 12 60000 7.20 

b) Embedded parts - 1 Set Ton 10 50000 5.00 

c) Rope drum hoist 25T Cap.-1set Ton 8 100000 8.00 

d) Hoist platform and trestle-1set Ton 5 50000 2.50 

9 Tailrace Gate 

a) Gate (Fixed Wheel type) 3.3m x 3.3m - 1 No. Ton 5 60000 3.00 

b) Embedded Parts including Hoist supporting Ton 3 50000 1.50 

structure - 1 Set 

c) Monorail hoist 10T Cap. Set 1 750000 7.50 

10 Pressure shaft steel Liner 

a) Steel Liner - 1 No. (ASTM A 537 Cl. 1 ) Ton 2300 70000 1610.00 

b) Bifurcation (ASTM A 517 Gr. F ) - 1. Nos. Ton 100 77000 77.00 

11 Adit Gates 

a) Adit gates (2.5m x2.5m) - 3 Nos. Ton 18 60000 10.80 

b) Embedded Parts -3 Set Ton 9 50000 4.50 

2343.50 

12 contingency @ 5% For Spare parts,bypass 

valves etc 

5% 117.18 

Total 2460.68

Sl 

No 

158 



K-BUILDINGS 

Description Plinth Area(Sqm). 

Rs. In lakhs 

Rate Unit Amount 

1.0 Residential Buildings 

1.1 Residential permanent buildings 2148 0.075 Sqm 161.10 

Service Charges @ 31% 49.94 

1.2 Residential temporary buildings 

2206 0.065 Sqm 143.39 

Service Charges @ 27% 38.72 

Total (Residential) 4354 393.15 

2.0 Non-Residential Buildings 

2.1 Non residential permanent 

buildings 

3591 0.065 Sqm 233.42 

Service Charges @ 22.5% 52.52 

2.2 Non residential and other purposes 

temporary buildings 

3575 0.055 Sqm 196.63 

(Sl No. 1,3&4) 

Service Charges @ 20.5% 40.31 

Total( Non-Residential) 7166 522.87 

Grand Total 11520 916.01 

Add for WORKS TAX @ 2% 18.32 

Grand Total 934.33

Sl 

No 

O-MISCELLANEOUS 

Description Quantity 

1.0 CAPITAL COST 

1.1 Purchase of Diesel Generator Sets (25 

KVA) including anciliary equipments 

etc. 

1.2 Cost of transmission line for 

construction power 

1.3 Water Supply, purification & 

distribution arrangements including 

purchase of water tankers,filters, cost of 

tanks & chlorination. 

1.4 Providing sewage disposal and storm 

water drains in office and residential 

complexes. 

159 

Rate 

(Rs.) 



Rs. In lakhs 

Unit Amount 

(Rs.) 

4.00 2.50 Nos 10.00 

10.00 10.00 km 100.00 

LS 25.00 

LS 25.00 

1.5 Providing & fixing of fire fighting equipments. LS 15.00 

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 1 243.00 

2.0 MAINTENANCE & SERVICE 

CHARGES 

2.1 R&M of Diesel Generator sets 4 Nos. 

for four years. 

16.00 4.00 Nos 64.00 

R&M of Transmission line for four 10.00 4.00 km 40.00

years. 

2.2 R&M of water supply facilities to the 

staff and labour colonies for four years 

2.3 R&M of sanitation and drainage 

facilities for office and residential 

compllex and labour colonies. 

160 



LS 10.00 

LS 8.00 

2.4 R&M of fire fighting equipments. LS 4.00 

2.5 Maint. Of telecommunication system 

and post offices. 

LS 20.00 

2,6 R&M of hospitals. LS 16.00 

2.7 Maint. of parks and welfare centres, 

clubs and school. 

LS 10.00 

2.8 R&M of Rest houses and field hostels. LS 8.00 

2.9 R&M of research & quality control 

laboratories 

LS 8.00 

2.10 Labour welfare compensation and 

retrenchment benefits. 

LS 30.00 

2.11 Providing Security & Policing LS 10.00 

2.12 R&M of Inspection vehicles and staff 

cars (15 nos) for four year 

15*4 2.50 year 150.00 

2.13 R&M of school buses, Ambulance Car 

etc. (4 nos) for for four year 

4*4 1.80 year 28.80 


3.0 MISCELLANEOUS 

3.1 Foundation stone laying ceremony, 

inaguration and visit of Dignitaries. 

LS 10.00 

3.2 Railway siding LS 20.00 

3.3 Installation and maintenance of 

Petrol/Diesel Pumps 

LS 16.00 

3.4 Providing anti malarial measures LS 2.00 

3.5 Procurement of technical leterature. LS 2.00 

3.6 Model Exhibits LS 4.00 

3.7 Canteen facilities and co-operative 

stores. 

LS 20.00 

3.8 Photographic and Cinemagraphic 

equipment and their maintenance 

LS 8.00 

3.9 Group insurance LS 15.00 

3.10 Publication and pamplets LS 2.00

161 



3.11 Creches LS 2.00 

3.12 Compensation for accident LS 8.00 

3.13 Training of personnels aboard includig 

study course and visit 

LS 15.00 

3.14 Award to workers LS 1.50 


Grand Total 775.30

Sl.No. Description of equipment 

1 Loader cum Excavator, 

1.0/0.25 cum. 

Q-Spl T&P for Infrastructure Development 

162 



Unit Quantity 

Rs in Lacs 

Rate 

Amount 

Nos 1 18.00 18.00 

2 Mini excavator 0.3 cum Nos 1 25.00 25.00 

3 Multi utility (Skid Steer loader) Nos 1 40.00 40.00 

4 Front End loader 2 cum Nos 1 24.00 24.00 

5 Crawler Dozer, 100 FHP Nos 1 50.00 50.00 

6 Wheel Dozer, 130 FHP Nos 1 58.00 58.00 

7 Diamond Core Drill 

(Mechanical) 

Nos 1 15.00 15.00 

8 Diamond Core Drill (Hyd) Nos 1 60.00 60.00 

9 Air Track/Wagon Drill Nos 1 15.00 15.00 

10 Jack Hammer/Pavement 

Breaker 

Nos 5 0.35 1.75 

11 Compressed Air(cfm) Nos 1200 0.0125 15.00 

12 Mobile Crane, 10 t Pick & 

Carry 

Nos 1 10.00 10.00 

13 Mobile Crane, 20 t (rough Nos 1 70.00 70.00 

Terrain) 

14 Road Roller, 8/10 t Nos 1 10.00 10.00 

15 Dewatering Pump L.S L.S 5.00 5.00 

16 Snow cutter Nos 1 50.00 50.00 

17 Tipper 4.5/6.0 cum. Nos 4 9.50 38.00 

18 Truck, 8/10 t Nos 2 7.50 15.00 

19 Low Bed Tractor Trailor, 20 t Nos 1 30.00 30.00 

20 Concrete Mixer, 14/10 cft Nos 2 1.50 3.00 

21 Explosive Van, 5/7 t Nos 1 10.00 10.00 

22 Water Tanker/Sprinkler, 10 KL Nos 1 12.00 12.00 

23 Petrol/Diesel Tanker, 10 KL Nos 1 12.00 12.00 

24 Bus/Mini Bus Nos 4 8.00 32.00 

25 Car/MUV Nos 2 4.00 8.00 

26 Jeep (Petrol/Diesel) Nos 15 4.00 60.00 

27 Ambulance Nos 2 8.00 16.00

163 



28 Workshop Equipt. L.S L.S 15.00 15.00 

29 Fire Tender Nos 1 15.00 15.00 

30 Recovery Van Nos 1 5.00 5.00 

31 Pick up Van/L.C.V Nos 1 5.00 5.00 

Total 742.75 

DISTRIBUTION OF COST UNDER HEAD Q - SPECIAL T & P AND V - 

RECEIPT & RECOVERIES 

Cost of equipments excluding inspection 

vehicles 

Cost of inspection vehicles (Item 24 to 27 

& 29) 

Cost Q R&R 

(Rs. In 

lakhs) 

611.75 152.94 114.70 

131.00 131.00 26.20 

Provision under head Q - Spl. T&P 742.75 283.94 

Recoveries to be shown under V- Receipt 

and Recoveries 

140.90

SI 

NO. 

164 



R - COMMUNUCATION 

Rs. In lakhs 

Description Unit Quantity Rate Amount 

1 Proposed new roads 

Approach road to dam site, DT, Top of Dam Km 23.0 80.00 1840.00 

Approach road to power house site Km 2.0 80.00 160.00 

Switch yard Km 1.0 80.00 80.00 

Surgeshaft,Adit I,II,III Km 9.0 80.00 720.00 

Colony Roads Km 2.0 75.00 150.00 

2 Proposed new bailey bridges Cl 30 

At dam site M 30.0 2.25 67.50 

3 Proposed Culverts 

Culverts ( 4nos) M 40.0 1.00 40.00 

Total 3057.50 

Add for WORKS TAX 2% 61.15 

Grand Total 3118.65

S. 

No. 

V - RECEIPT & RECOVERIES 

Item Amount 

165 



(Rs. In Lakhs) 

1. Recovery from the Sale of Equipments 140.90 

2 Recovery from the DG sets 2.00 

3 Recovery from Temporary Buildings 62.86 

Total 205.76

COST ESTIMATE OF E&M WORKS 

Generator, Turbine and Accessories 

166 



Annex-I (page 1 of 2) 

S.No. Item Particulars Qty Unit Rate Amount Excise Duty* 

Total 

(Rs Rate Amount (Rs 

Lakhs) 

Lakh) 

1 2 3 3(a) 4 5 6 7 5+7 

1 (a) Generating units and 

Bus Ducts 2x35 MW, 

1000 rpm, Head 1106.37 

meters 

2 Step up transformer 

11/220 KV, 15MVA, 

3 

single phase 

Auxiliary Electrical 

Equipment for Power 

Stations (Except 

Transformer) (5% of item 

1) 

3 no. 3400 

Rs/KW 

7 no. 250 

Rs/KVA 

3570.00 16 571.20 4141.20 

262.5 16 42 304.5 

178.5 16 28.56 207.06 

4 Auxiliary Equipment & 

178.5 16 28.56 207.06 

Services for Power 

stations (5% of Item 1) 

XLPE Cable (220 kV) 2750 m 0 Rs/m 0.00 16 0.00 0.00 

5 

XLPE Cable termination 

Kit 

Switchyard (220KV) 5 

6 Spares (5% of item 1 and 

3% of item 2 to 5 ) 

20 no. 0 each 0.00 16 0.00 0.00 

132 660.00 16 105.60 765.60 

bays lacs/bay 

178.5 38.39 216.89 16 34.70 251.59 

7 Subtotal(1-6) 5877.01 

8 Central Sales tax** 4% of 

item 7 

202.66 235.08 

9 Transportation 

Insurance 6% of item 7 

& 

10 Erection & commissioning 

8% of item 7 except spares 

352.62 

450.03 

11 Subtotal (7-10) 

Total of FC (XLPE Cable 

6914.74 

12 

and Termination kit) in 

INR (As per Annexure-II) 

710.90

13 

14 

15 

16 

17 

18 

Custom Duty @22% of 

item 12 

Marine frieght and 

insurance @6% Approx of 

12 

included in above item 12 

167 



42.65 

Inland Frieght and 

insurance 6% of item 12 42.65 

Erection & commissioning 

8% of item 12 excluding 

spares 

Subtotal of FC ( item 12- 

16 in INR) 

Subtotal of item no 

11+17(Foreign plus indian 

component) 

19 Establishment, 

Contingency, other 

charges 11% of Item 18 

Excluding duties 

GRAND TOTAL (In 

Lakhs) 

*Custom duty in case of imported Items 

**Not applicable for Imported Items 

55.85 

852.06 

7766.80 

621.42 

8388.22 

*** The cost of 220kV switchyard has been taken as Rs.150 lacs per bay taking into consideration high 

altitude of the project

COST ESTIMATE OF E&M WORKS 

Power Evacuation system 

S.No. Item Particulars Qty Rate Amount Excise Duty* 

168 



Annex-III (page 1 of 1) 

Total 

(Rs (Rs % Amount (Rs 

Lakhs) Lakhs) 

Lakh) 

1 2 3 4 5 6 7 5+7 

1 1 no 220kV Double 

Circuit line (of 

approximately 36 kms) 

36 km 35 

lacs/km 

1260.00 16 201.60 1461.60 

2 Spares ( 3% of 1) 37.8 16 6.048 43.85 

3 Subtotal(1) 1505.45 

4 Central Sales tax 4% of 

item 3 

51.91 60.22 

5 Transportation & 

Insurance 6% of item 3 

7 Erection & commissioning 

8% of item 3 except spares 

90.33 

116.93 

8 Subtotal(2) 1772.92 

9 Establishment, 

Contingency, other 

charges 11% of Item 3 

excluding duties 

142.76 

GRAND TOTAL (In 

Lakhs) 

1915.68



CHAPTER – XIII 

ECONOMIC EVALUATION

13.1 GENERAL 

CHAPTER – XIII 

ECONOMIC EVALUATION 

169 



The Project has been contemplated as a run-off the river scheme on river Ringpi. The 

project is estimated to cost Rs. 466.04 crores excluding IDC at June 2003 Price Level. 

Sale price of energy generated at powerhouse bus bars has been worked out as 3.61 Rs. 

per unit with free power to home state (Table 13.2) & Rs. 3.17 per unit without free 

power to home state (Table 13.2-A). 

13.2 ECONOMIC JUSTIFICATION: 

The energy generation of the project with an installed capacity of 2 X 35 MW has been 

estimated at 317.41 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 5.5 years including 1.5 years for Infrastructure works. 

The estimated Present Day Cost of the project is Rs. 466.04 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.

170 



The phasing of expenditure without IDC for present day cost is shown as below: 

Year Estimated Cost at June 2003 P.L. 

(Rs. in Crores) 

1 st 46.60 

2 nd 65.25 

3 rd 

93.21 

4 th 130.49 

5 th 93.21 

5.5 th 37.28 

Net Cost 466.04 

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 for estimated 

Present Day cost of the project. 

The estimated IDC with estimated present cost is Rs. 53.23 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

171 



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. 2.93 Per Unit 

with free power to home state (Table 13.3) & Rs 2.58 per unit without free power to 

home state. (Table 13.3-A).

172 



STATEMENT SHOWING IDC CALCULATION AT PRESENT DAY COST (JUNE 2003 LEVEL) 

PRESENT DAY COST 466.04 Crs. 

Civil Works 363.00 Crs. Electrical Works 83.88 Crs. 

INTEREST RATE PER ANNUM 10% Transmission cost 19.16 Crs. 

(Rs. in Crs.) 

Present Day Amount Receivable I.D.C Loan Outstanding Amount Receivable 

Year Cost Equity Loan at the end of Equity Loan 

year (for the year) 

1 2 3 4 5 6 7 8 

1 46.60 46.60 46.60 

2 65.25 65.25 65.25 

3 93.21 43.93 49.28 1.30 50.58 43.93 50.58 

4 130.49 130.49 11.58 192.65 142.07 

5 93.21 93.21 23.93 309.79 117.13 

5.5 37.28 37.28 16.42 363.49 53.70 

Total 466.04 155.78 310.26 53.23 155.78 363.49 

IDC 53.23 Crs. Equity 155.78 Crs. 

Net cost of the project 519.27 Crs. Loan 363.49 Crs. 

Table-13.1

173 



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 70 MW 

2 Cost of the Project (Net) Rs. 466.04 Crores 

3 Interest During Construction Rs. 53.23 Crores 

4 Total Cost of Project Rs. 519.27 Crores 

(Including IDC) 

a) Equity 30% Rs. 155.78 Crores 

b) Loan 70% Rs. 363.49 Crores 

5 Annual Energy Generation 317.41 MU 

6 0.7% As Auxiliary Consumption of No. 5 0.70% 2.22 MU 

7 Energy Available After Auxiliary Consumption 315.19 MU 

8 0.5% As Transformer Loss of No. 7 0.50% 1.58 MU 

9 Energy Available After Transformer Loss 313.61 MU 

10 Free Power to Home State 12% 37.63 MU 

11 

Energy Available After Allowing Free 

Power 275.98 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 34.83 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

30.29 Crores 

B) Energy Charges 

SUB-TOTAL 65.12 Crores 

a) O&M Charges 1.50% 7.79 Crores 

b) Return on Equity 16.00% 24.93 Crores 


c) Interest on Working Capital 10.00% 1.72 Crores 

I) O&M Charges for 1 month 0.65 

II) 2 Months Average Billing 16.59 

TOTAL Rs. 99.56 Crores 

13 Sale Price at Bus Bar/Unit 3.61 Rs. 

14 Cost of Generation at Bus Bar/Unit 2.38 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.

174 



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 70 MW 

2 Cost of the Project (Net) Rs. 466.04 Crores 

3 Interest During Construction Rs. 53.23 Crores 

4 Total Cost of Project Rs. 519.27 Crores 

(Including IDC) 

a) Equity 30% Rs. 155.78 Crores 

b) Loan 70% Rs. 363.49 Crores 

5 Annual Energy Generation 317.41 MU 

6 0.7% As Auxiliary Consumption of No. 5 0.70% 2.22 MU 

7 Energy Available After Auxiliary Consumption 315.19 MU 

8 0.5% As Transformer Loss of No. 7 0.50% 1.58 MU 

9 Energy Available After Transformer Loss 313.61 MU 

10 Free Power to Home State 0% 0.00 MU 

11 

Energy Available After Allowing Free 

Power 313.61 MU 

12 Fixed and Running Charges 

A) Capacity Charges 

a) Interest on Loan 10.00% 34.83 Crores 

b) Depreciation Charges 

(Limited to 1/12 th of Loan Amount) 

30.29 Crores 

B) Energy Charges 


a) O&M Charges 1.50% 7.79 Crores 

b) Return on Equity 16.00% 24.93 Crores 


c) Interest on Working Capital 10.00% 1.72 Crores 

I) O&M Charges for 1 month 0.65 

II) 2 Months Average Billing 16.59 

TOTAL Rs. 99.56 Crores 

13 Sale Price at Bus Bar/Unit 3.17 Rs. 

14 Cost of Generation at Bus Bar/Unit 2.38 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.

CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION 

175 



TABLE-13.3 

Annual Generation in a 90% dependable year 

Annual Generation after allowing losses & free 

power to home state in a 90% dependable year 

Total cost including IDC 

Equity 30% 

Loan 70% 

Rs. 

Rs. 

Rs. 

317.41 

275.98 

519.27 

155.78 

363.49 

MU 

MU 

Crores 

Crores 

Crores 

O&M Charges 

Rate of increase of O&M Charges after 1st Year (Compounded) 

Interest rate on Loan 

Interest rate on Working Capital 

Return on Equity 

Discounting rate 

1.50% 

6% 

10.0% 

10.00% 

16% 

12% 

Year 

Out- 

Capacity Charges 

(Rs.in Cr.) (Rs.in Cr.) 

O&M Interest on 

Charges Per Unit 

(Rs. per Unit) 

Discounting 

Factor 

Discounted 

Tariff 

standing Interest Depre- Total Return O&M for1 Working Capital Total Capacity Energy Total (Paisa per 

Loan(Rs.in 

on 

2 months 

Cr.) on loan ciation 

equity Charges month Average Billing Interest charges charges Unit) 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 

1 363.49 34.83 30.29 65.13 24.93 7.79 0.65 16.59 1.72 34.44 2.36 1.25 3.61 1.0000 3.61 

2 333.20 31.81 30.29 62.10 24.93 8.26 0.69 16.16 1.68 34.87 2.25 1.26 3.51 0.8929 3.14 

3 302.91 28.78 30.29 59.07 24.93 8.75 0.73 15.73 1.65 35.32 2.14 1.28 3.42 0.7972 2.73 

4 272.62 25.75 30.29 56.04 24.93 9.28 0.77 15.31 1.61 35.81 2.03 1.30 3.33 0.7118 2.37 

5 242.33 22.72 30.29 53.01 24.93 9.83 0.82 14.89 1.57 36.33 1.92 1.32 3.24 0.6355 2.06 

6 212.04 19.69 30.29 49.98 24.93 10.42 0.87 14.48 1.53 36.88 1.81 1.34 3.15 0.5674 1.79 

7 181.74 16.66 30.29 46.95 24.93 11.05 0.92 14.07 1.50 37.47 1.70 1.36 3.06 0.5066 1.55 

8 151.45 13.63 30.29 43.92 24.93 11.71 0.98 13.67 1.46 38.10 1.59 1.38 2.97 0.4523 1.34 

9 121.16 10.60 30.29 40.89 24.93 12.41 1.03 13.28 1.43 38.77 1.48 1.40 2.89 0.4039 1.17 

10 90.87 7.57 30.29 37.86 24.93 13.16 1.10 12.89 1.40 39.48 1.37 1.43 2.80 0.3606 1.01 

11 60.58 4.54 30.29 34.83 24.93 13.95 1.16 12.51 1.37 40.24 1.26 1.46 2.72 0.3220 0.88 

12 30.29 1.51 30.29 31.81 24.93 14.79 1.23 12.14 1.34 41.05 1.15 1.49 2.64 0.2875 0.76 

13 0.00 0.00 4.52 4.52 24.93 15.67 1.31 7.67 0.90 41.50 0.16 1.50 1.67 0.2567 0.43 

14 0.00 4.52 4.52 24.93 16.61 1.38 7.83 0.92 42.46 0.16 1.54 1.70 0.2292 0.39 

15 4.52 4.52 24.93 17.61 1.47 8.00 0.95 43.48 0.16 1.58 1.74 0.2046 0.36 

16 4.52 4.52 24.93 18.67 1.56 8.18 0.97 44.57 0.16 1.61 1.78 0.1827 0.32 

17 4.52 4.52 24.93 19.79 1.65 8.37 1.00 45.71 0.16 1.66 1.82 0.1631 0.30 

18 4.52 4.52 24.93 20.97 1.75 8.57 1.03 46.93 0.16 1.70 1.86 0.1456 0.27 

19 4.52 4.52 24.93 22.23 1.85 8.79 1.06 48.22 0.16 1.75 1.91 0.1300 0.25 

20 4.52 4.52 24.93 23.57 1.96 9.02 1.10 49.59 0.16 1.80 1.96 0.1161 0.23 

21 4.52 4.52 24.93 24.98 2.08 9.26 1.13 51.04 0.16 1.85 2.01 0.1037 0.21 

22 4.52 4.52 24.93 26.48 2.21 9.52 1.17 52.58 0.16 1.91 2.07 0.0926 0.19 

23 4.52 4.52 24.93 28.07 2.34 9.79 1.21 54.21 0.16 1.96 2.13 0.0826 0.18 

24 4.52 4.52 24.93 29.75 2.48 10.07 1.26 55.93 0.16 2.03 2.19 0.0738 0.16 

25 4.52 4.52 24.93 31.54 2.63 10.38 1.30 57.76 0.16 2.09 2.26 0.0659 0.15 

26 4.52 4.52 24.93 33.43 2.79 10.70 1.35 59.70 0.16 2.16 2.33 0.0588 0.14 

27 4.52 4.52 24.93 35.44 2.95 11.05 1.40 61.76 0.16 2.24 2.40 0.0525 0.13 

28 4.52 4.52 24.93 37.56 3.13 11.41 1.45 63.94 0.16 2.32 2.48 0.0469 0.12 

29 4.52 4.52 24.93 39.82 3.32 11.79 1.51 66.25 0.16 2.40 2.56 0.0419 0.11 

30 4.52 4.52 24.93 42.20 3.52 12.20 1.57 68.70 0.16 2.49 2.65 0.0374 0.10 

31 4.52 4.52 24.93 44.74 3.73 12.64 1.64 71.30 0.16 2.58 2.75 0.0334 0.09 

32 4.52 4.52 24.93 47.42 3.95 13.09 1.70 74.05 0.16 2.68 2.85 0.0298 0.08 

33 4.52 4.52 24.93 50.27 4.19 13.58 1.78 76.97 0.16 2.79 2.95 0.0266 0.08 

34 4.52 4.52 24.93 53.28 4.44 14.10 1.85 80.06 0.16 2.90 3.06 0.0238 0.07 

35 4.52 4.52 24.93 56.48 4.71 14.64 1.93 83.34 0.16 3.02 3.18 0.0212 0.07 

TOTAL 9.1566 26.80 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax etc. Levellised Tariff =(B)/(A) 2.93

176 



TABLE-13.3 A 

CALCULATION OF ENERGY RATE WITH PRESENT COST (JUNE 2003 PRICE LEVEL) AS PER TARIFF NOTIFICATION (Without free power to home state) 

Annual Generation in a 90% dependable year 

Annual Generation after allowing losses 

in a 90% dependable year 

Total cost including IDC 

Equity 30% 

Loan 70% 

Rs. 

Rs. 

Rs. 

317.41 

313.61 

519.27 

155.78 

363.49 

MU 

MU 

Crores 

Crores 

Crores 

O&M Charges 

Rate of increase of O&M Charges after 1st Year (Compounded) 

Interest rate on Loan 

Interest rate on Working Capital 

Return on Equity 

Discounting rate 

1.50% 

6% 

10.0% 

10.00% 

16% 

12% 

YEAR 

Out- 

Standing 

CAPACITY CHARGES 

(Rs.in Cr.) (Rs.in Cr.) 

O&M Interest on 

CHARGES PER UNIT 

(Rs. per Unit) 

Discounting 

Factor 

Discounted 

Tariff 

Loan Interest Depre- Total Return O&M for1 Working Capital Total Capacity Energy Total (Paisa per 

1 

(Rs.in Cr.) 

2 

on loan 

3 

ciation 

4 5 

on equity 

6 

Charges 

7 

month 

8 

2 months 

Average Billing 

9 

Interest 

10 11 

charges 

12 

charges 

13 14 15 

Unit) 

16 

1 363.49 34.83 30.29 65.13 24.93 7.79 0.65 16.59 1.72 34.44 2.08 1.10 3.17 1.0000 3.17 

2 333.20 31.81 30.29 62.10 24.93 8.26 0.69 16.16 1.68 34.87 1.98 1.11 3.09 0.8929 2.76 

3 302.91 28.78 30.29 59.07 24.93 8.75 0.73 15.73 1.65 35.32 1.88 1.13 3.01 0.7972 2.40 

4 272.62 25.75 30.29 56.04 24.93 9.28 0.77 15.31 1.61 35.81 1.79 1.14 2.93 0.7118 2.08 

5 242.33 22.72 30.29 53.01 24.93 9.83 0.82 14.89 1.57 36.33 1.69 1.16 2.85 0.6355 1.81 

6 212.04 19.69 30.29 49.98 24.93 10.42 0.87 14.48 1.53 36.88 1.59 1.18 2.77 0.5674 1.57 

7 181.74 16.66 30.29 46.95 24.93 11.05 0.92 14.07 1.50 37.47 1.50 1.19 2.69 0.5066 1.36 

8 151.45 13.63 30.29 43.92 24.93 11.71 0.98 13.67 1.46 38.10 1.40 1.21 2.62 0.4523 1.18 

9 121.16 10.60 30.29 40.89 24.93 12.41 1.03 13.28 1.43 38.77 1.30 1.24 2.54 0.4039 1.03 

10 90.87 7.57 30.29 37.86 24.93 13.16 1.10 12.89 1.40 39.48 1.21 1.26 2.47 0.3606 0.89 

11 60.58 4.54 30.29 34.83 24.93 13.95 1.16 12.51 1.37 40.24 1.11 1.28 2.39 0.3220 0.77 

12 30.29 1.51 30.29 31.81 24.93 14.79 1.23 12.14 1.34 41.05 1.01 1.31 2.32 0.2875 0.67 

13 0.00 0.00 4.52 4.52 24.93 15.67 1.31 7.67 0.90 41.50 0.14 1.32 1.47 0.2567 0.38 

14 0.00 4.52 4.52 24.93 16.61 1.38 7.83 0.92 42.46 0.14 1.35 1.50 0.2292 0.34 

15 4.52 4.52 24.93 17.61 1.47 8.00 0.95 43.48 0.14 1.39 1.53 0.2046 0.31 

16 4.52 4.52 24.93 18.67 1.56 8.18 0.97 44.57 0.14 1.42 1.57 0.1827 0.29 

17 4.52 4.52 24.93 19.79 1.65 8.37 1.00 45.71 0.14 1.46 1.60 0.1631 0.26 

18 4.52 4.52 24.93 20.97 1.75 8.57 1.03 46.93 0.14 1.50 1.64 0.1456 0.24 

19 4.52 4.52 24.93 22.23 1.85 8.79 1.06 48.22 0.14 1.54 1.68 0.1300 0.22 

20 4.52 4.52 24.93 23.57 1.96 9.02 1.10 49.59 0.14 1.58 1.73 0.1161 0.20 

21 4.52 4.52 24.93 24.98 2.08 9.26 1.13 51.04 0.14 1.63 1.77 0.1037 0.18 

22 4.52 4.52 24.93 26.48 2.21 9.52 1.17 52.58 0.14 1.68 1.82 0.0926 0.17 

23 4.52 4.52 24.93 28.07 2.34 9.79 1.21 54.21 0.14 1.73 1.87 0.0826 0.15 

24 4.52 4.52 24.93 29.75 2.48 10.07 1.26 55.93 0.14 1.78 1.93 0.0738 0.14 

25 4.52 4.52 24.93 31.54 2.63 10.38 1.30 57.76 0.14 1.84 1.99 0.0659 0.13 

26 4.52 4.52 24.93 33.43 2.79 10.70 1.35 59.70 0.14 1.90 2.05 0.0588 0.12 

27 4.52 4.52 24.93 35.44 2.95 11.05 1.40 61.76 0.14 1.97 2.11 0.0525 0.11 

28 4.52 4.52 24.93 37.56 3.13 11.41 1.45 63.94 0.14 2.04 2.18 0.0469 0.10 

29 4.52 4.52 24.93 39.82 3.32 11.79 1.51 66.25 0.14 2.11 2.26 0.0419 0.09 

30 4.52 4.52 24.93 42.20 3.52 12.20 1.57 68.70 0.14 2.19 2.33 0.0374 0.09 

31 4.52 4.52 24.93 44.74 3.73 12.64 1.64 71.30 0.14 2.27 2.42 0.0334 0.08 

32 4.52 4.52 24.93 47.42 3.95 13.09 1.70 74.05 0.14 2.36 2.51 0.0298 0.07 

33 4.52 4.52 24.93 50.27 4.19 13.58 1.78 76.97 0.14 2.45 2.60 0.0266 0.07 

34 4.52 4.52 24.93 53.28 4.44 14.10 1.85 80.06 0.14 2.55 2.70 0.0238 0.06 

35 4.52 4.52 24.93 56.48 4.71 14.64 1.93 83.34 0.14 2.66 2.80 0.0212 0.06 

TOTAL 9.1566 23.58 

(A) (B) 

Note: The charges per unit is exclusive of water cess, spares, incentive & Income Tax etc. Levellised Tariff =(B)/(A) 2.58



PLATES

DIVERSION 

BED LEVEL : 1055 m. 

PANAN 

POWER HOUSE 

T.R.L. : 1060 m. 

AV.GROSS HEAD : 740 M 

FIRM POWER : 19.7 MW 

INST. CAPACITY : 160 MW 

PANAN H.E. SCHEME 

LAVEN 

POWER HOUSE 

LINGZA 

T.R.L. : 780 m. 




LINGZA H.E. SCHEME 

DIVERSION 


POWER HOUSE 

T.R.L. : 1800 m. 




RINGPI H.E. SCHEME 

DIVERSION 


N 

SCALE- 1:50000 

PLATE - 1 

MAY, 1983 

PANAN, LINGZA & RINGPI 

H.E. SCHEMES 

ON TOLUNG RIVER 

(TISTA RIVER SYSTEM) 

DRG.NO. HEPR-PS-BHM-784

ELEVATION IN METERS 

SCHEMATIC DIAGRAM SHOWING CASCADE DEVELOPMENT OF TEESTA RIVER BASIN (SIKKIM) 

3500 

3000 

2500 

2000 

1500 

1000 

500 

000 

TEESTA PROJECT 

STAGE -VI 

SALENTFEATURES:- 

1. CATCHMENT AREA 4874sqkm 

2. DISCHARGE(Dependable) 93CUMECS 

3. F.R.L. 341m. 

4. TYPE OF DAM(Conc.GravityDam) 

5. T.W.L. 253.5om. 

6. AVERAGE GROSS HEAD 84.50m. 

7. LENGTH OF TUNNEL 3.50km. 

8. FIRM POWER 55.50MW. 

9. PROPOSED INSTALLED 

CAPACITY 360MW. 

11O 

UNDER CONST.BY NHPC 


STAGE -V 


1. CATCHMENT AREA 4336sqkm 

2. DISCHARGE(Dependable) 60cumecs 

3. F.R.L. 579m. 

4. TYPE OF DAM-Conc.GravityDam 

5. T.W.L. 359.5m. 

6. AVERAGE GROSS HEAD 216.73m. 

7. LENGTH OF TUNNEL 18km. 

8. FIRM POWER 100mw. 


CAPACITY 510mw. 

100 90 80 70 


STAGE -II 


1. CATCHMENT AREA 1772sqkms 

2. DISCHARGE(Dependable)9.29cumecs. 

3. F.R.L. 2287m. 


5. T.W.L. 1592m. 

6. AVERAGE GROSS HEAD 683m. 


8. FIRM POWER 57.38mw. 




STAGE -III 


1. CATCHMENT AREA 2787sqkm. 

2. DISCHARGE(Dependable)31cumecs 

3. F.R.L. 1585m. 

4. TYPE OF DAM(Conc.GravityDam) 

5. HEIGHT OF DAM 103m. 

6. T.W.L. 779m. 


8. LENGTH OF TUNNEL 12.93m. 

9. FIRM POWER 180mw. 



60 50 

DISTANCE IN KILOMETER 


STAGE-IV 


1. CATCHMENT AREA 3859sqkms 

2. DISCHARGE(Dependable)56cumecs. 

3. F.R.L. 722m. 


5. T.W.L. 589m. 


7. LENGTH OF TUNNEL 11km. 




40 

LACHEN PROJECT 


1. CATCHMENT AREA 1604sq.km. 

2. DISCHARGE(Dependable)9.25 cumecs. 

3. F.R.L. 2650m. 


5. T.W.L. 2290m. 






30 20 


STAGE -I 


10 0 

3500 

3000 

2500 

1. CATCHMENT AREA 1461sq.km. 

2. DISCHARGE(Dependable)10.8 cumecs. 

3. F.R.L. 3258m. 

4. TYPE OF DAM(Conc.GravityDam) 2Nos. 

5. T.W.L. 2675m. 






500 

000 

2000 

1500 

1000 

PLATE-2

27° 

45' 

40' 

35' 

27° 

30' 

88° 15' 

6200 

6200 

6400 

5200 

4200 

5000 

4600 

88° 15' 

6539 

4800 

4000 

6671 

3720 

4850 

4600 

4400 

4000 

4400 

4800 

5485 

4000 

5000 

RUKEL CHHU 

4000 

3690 

4565 

4600 

5215 

5508 

4400 

4890 

4600 

5000 

4600 

5000 

4340 

3400 

3200 

4200 

4600 

4440 

4200 

4425 

3000 

3600 

3800 

4000 

RUKEL H.E PROJECT 

F R L 2395 

R B L 2355 

M D D L 2385 

3800 

4525 

5288 

4600 

3190 

3400 

3800 

4000 

4400 

4200 

4400 

3000 

6888 

2810 

2600 

3000 

DAM AXIS 

4000 

6345 

5259 

8425 

2800 

3200 

20' 25' 

UMRAM CHHU 

RANGYONG H.E PROJECT 

F R L 1845 

R B L1795 

M D D L1825 

RANGYONG CHHU 

T W L 1845 

AVG. GROSS HEAD 541.1 

P.H. CAPACITY 3 X 11 

4200 

4600 

2600 

2800 

6065 5643 

3800 

3000 

5600 

5718 

3800 

3600 

3400 

3200 

3000 

3580 

5200 

4800 

5000 

5200 

4600 

4800 

3775 

2600 

4934 

4000 

3200 

4180 

4000 4200 

3400 

4400 

3800 

5070 

4200 

4600 

4800 

4390 

4885 

DAM AXIS 

3200 

4200 

5200 

4000 

4925 

4600 

PASSAM CHHU 

CANE BRIDGE 

T W L 1098 

JUMTHUL CHU 

F R L 1845 

R B L1795 

M D D L1825 

DAM AXIS 

2200 

2400 

2800 

4200 

2000 

4000 

4400 

POKHRAM CHU 

AVG GROSS HEAD 738.2 


3800 

4660 

3400 

2600 

4800 

4600 

2800 

3600 

3000 

4800 

3580 

2600 

2400 

5000 

4135 

5000 

4115 

1800 

2800 

3000 

3200 

3400 

RINGPI H.E PROJECT 

F R L 2966 

R B L 2940 

M D D L2933 

4640 

LINGZA H.E PROJECT 

F R L 1850 

M D D L 1830 

R B L 1795 

RINGYONG CHU 

3370 

2600 

2400 

2600 

RGVINGRUM CHU 

2000 

2400 

4940 

1400 

2800 

2200 

2400 

3000 

1800 

3200 

3355 

2900 

2600 

2800 

2600 

2800 

3000 

4060 

KISHONG CHU 

DAM AXIS 

1600 

2200 

DAM AXIS 

PANAN H.E PROJECT 

F R L 1095 

R B L 1050 

M D D L 1085 

3000 

2800 

2600 

2400 

4000 

4235 

DAWATHANG CHHU 

RINGPI CHHU 

RANGYONG CHHU 

LUDUI CHHU 

PEGAR CHHU 

T W L 1095 

AVG. GROSS HEAD 746 


DAM AXIS 

1200 

1800 

4200 

4200 

2000 

1600 

4400 

3000 

1400 

2200 

4400 

1200 

2200 

2400 

4600 

4600 

2725 

1800 

1600 

2800 

4800 

5000 

3200 

KONGCHA CHU 

ZONG CHHU 

2600 

2800 

3000 

3200 

1200 

1000 

4965 

2400 

2503 3065 

5060 

3000 

3400 

88° 30' 

3600 

4600 

4800 

3000 

3200 

SUSPENSION BRIDGE 

1800 

2600 

2400 

5615 

4400 

4460 

4195 

2200 

2000 

TW L 770 

27° 

30' 

3400 

3800 

2008 

88° 30' 

1800 

4600 

3400 

3600 

3400 

3200 

3800 

3400 

3200 

2800 

2600 

2200 

1400 

1600 

27° 

45' 

TW L 1853 

AVG GROSS HEAD 1110 


2400 

1600 

1400 

1400 

1000 

1600 

AVG. GROSS HEAD 322 

1200 

2400 

TOLUNG CHU 

1000 

2485 

1000 

1200 

800 

800 

2000 

1000 

RAHI CHU 

1000 

1400 

TEESTA RIVER 

TEESTA H.E. PROJECT 

(STAGE-IV) 

1200 

DAM AXIS 

1400 

1600 

1430 

1800 

2845 

2000 

3200 

3400 

3000 

2800 

2600 

2400 

2200 

1800 

1800 

1600 

1400 

1200 

1000 

1000 

1200 

1400 

1600 

1800 

2000 

NOTES 

1. NO DIMENSION SHALL BE MEASURED FROM 

THIS DRAWING . 

2. CONTOURS AND OTHER FEATURES HAVE 

BEEN TRACED FROM THE S.O.I. TOPO-SHEET 

NO. 78A/6 & 78A/10 (SCALE:- 1:50000). 

FEB.2004 

PLATE-3 

F/DCE730/01/02

SCHEMATIC DIAGRAM SHOWING CASCADE DEVELOPMENT 

OF TOLUNG RIVER BASIN (SIKKIM) 

ELEVATION IN METERS 

3000 

2750 

2500 

2250 

2000 

1750 

1500 

1250 

PANAN HE PROJECT 

LINGZA HE PROJECT 

o 2 4 6 8 

RANGYONG HE PROJECT 

DISTANSE IN KILOMETER 

RINGPI HE PROJECT 

RUKEL HE PROJECT 

10 12 14 16 18 20 22 

3000 

2750 

2500 

2250 

2000 

1750 

1500 

1250 

PLATE-4

RINGPI H.E. SCHEME - SIKKIM 

PLATE 4.1

TALAM HYDRO ELECTRIC PROJECT 

( 2 X 35 MW ) 

RINGPI HYDRO ELECTRIC PROJECT 

( 2 X 35 MW ) 

RANGYONG HYDRO ELECTRIC PROJECT 

( 3 X 47 MW ) 

RUKEL HYDRO ELECTRIC PROJECT 

( 3 X 11 MW ) 

N E P A L 

LINGZA HYDRO ELECTRIC PROJECT 

( 3 X 40 MW) 

YANGSS CHHU 

RAMAM OR 

RANGBONG KHOLA 

C H I N A 

CHAUNRIKHIANG 

TIKIPCHHU 

RIYONG KHOLA 

RIMBI CHHU 

T I B E T 

PHUTHUNG CHHU 

TONGSHIONG GLACIER 

TALUNG GLACIER 

CHOKCHURANG CHHU 

PREK CHHU 

LAMBI 

KHUNGME 

RATHANG CHHU 

KALEJ KHOLA 

TINGCHEN KHANG 

REFLI CHHU 

RISHI KHOLA 

GOMA CHHU 

RUKEL CHHU 

RONGDUNG CHHU 

GEZING 

REATHOK KHOLA 

SOMBARE NAYA BAZAR 

KHORA CHHU 

LUNGMA CHHU 

UMMRAM CHHU 

RANGYONG CHHU 

RANGIT RIVER 

KAYAM CHHU 

NAMCHI 

RINGYONG CHHU 

RANGPO CHHU 

GREAT RANGIT RIVER 

NACHUNGTHANGKHA 

THANG CHHO 

NAKU CHHU 

LANGBO CHHU 

THOMPHYAK CHHU 

POKE CHHU 

LHONAK CHHU 

RINGPI CHHU 

MONMU CHHU 

RANGPHAP CHHU 

ZEMU CHHU 

TOLUNG CHHU 

RUN CHHU 

SINGTAM 

TEESTA RIVER 

MANGKHA 

SIRWANI 

RONGNI CHHU OR RANI K 

TEESTA RIVER 

RAHI CHHU 

LASHA CHHU 

KALEP 

MANGAN 

DIKCHU 

TEESTA RIVER 

GYAMTHANG CHHU 

BURUM CHHU 

GEY CHHU 

TEESTA RIVER 

RANGPO CHHU 

RANGPO 

CHHU 

TARUM CHHU 

RABOM CHHU 

RI CHHU 

RISHI KHOLA 

BAKCHA 

DIK CHHU 

YUMRHANG CHHU 

CHUNGTHANG 

GANGTOK 

CHAKUNG CHHU 

CHHU 

RORA CHHU 

TAKCHOM CHHU 

RANGLI KHOLA 

W E S T B E N G A L 

DONGKYA CHHU 

TOKLUNG CHHU 

RATE CHHU 

BYU CHHU 

SEBOZANG CHHU 

LUNGZE CHHU 

RANGPO CHHU 

C H I N A 

T I B E T 

B H U T A N 

PANAN HYDRO ELECTRIC PROJECT 

(4 X 50MW) 

RONGNI STORAGE PROJECT 

( 3 X 65 MW) 

NOTES 

1. NO DIMENSION SHALL BE MEASURED FROM THIS DRAWING. 

PRE- FEASIBILITY REPORT DRAWING 

VICINITY MAP 

PLATE NO.- 6.1 

TEESTA HYDRO ELECTRIC PROJECT(STAGE-I) 

( 4 X 80 MW ) 

LACHEN HYDRO ELECTRIC PROJECT 

( 3 X 70 MW ) 

TEESTA HYDRO ELECTRIC PROJECT(STAGE-V) 

( 3 X 170 MW ) 

DIKCHU HYDRO ELECTRIC PROJECT 

( 3 X 35 MW ) 

LEGEND 

INTERNATIONAL BOUNDARY 

STATE BOUNDARY 

RIVER 

TRIBUTARY 

ROAD 

DAM SITE 

F/DCE730/01/02

88° 

27' 30'' 

3800 

3600 

3400 

4000 

KISHONG KISHONG CHU CHU 

3600 

3800 

U/S COFFERDAM 

3200 

3800 

3000 

DESILTING CHAMBER 

(50M X 5M X 7.5M) 

DAM AXIS 

JHUMTHUL CHU 

3600 

3400 

27° 40' 00'' 

3200 

RINGPI CHU 

DIVERSION TUNNEL 3.3 M Ø 

HORSE SHOE SHAPED 

D/S COFFERDAM 


ADIT-I 

3200 

3000 

2800 

2600 

2600 

2600 

2400 

HEAD RACE TUNNEL 3.3 M Ø 


ADIT-2 

2400 

2200 

3400 

3800 

2200 

2600 

INCLINED PRESSURE SHAFT 1.5 M Ø 

SURGE SHAFT 10 M Ø 

3200 

ADIT-3 

30002800 

2200 

T.R.T. 3.3 M Ø 

H.S.SHAPE 

TRANSFORMER 

CAVERN 

SWITCHYARD 

2400 

2600 

2600 

2800 

3000 

2800 

POWER HOUSE 

3200 

3200 

M.A.T. 

NOTES 

3000 

ISHANA 

2400 

LB 

3200 

2200 

2000 

3200 

3000 

2800 

1800 

2600 

2200 

2000 

1600 

1600 

2400 

1800 




THIS DRAWING 


NO. 78A/6 (SCALE:- 1:50000) 


LAY-OUT PLAN 

F/DCE730/01/02

3200 

KISHONG CHU 

3000 

U/S COFFERDAM 


(50M X 5M X 7.5M) 

JHUMTHUL CHU 

DAM AXIS 

DIVERSION TUNNEL 3.3 M Ø 


D/S COFFERDAM 

RINGPI CHU 

ADIT-I 


0.75M.X 1.5M. D-SHAPE 

27° 

40' 00'' 

3000 

H.R.T.3.3M.Ø H.S. SHAPE 

NOTES 


THIS DRAWING 



NO. 78A/6 (SCALE:- 1:50000) 



DAM AREA 

LAY-OUT PLAN 

F/DCE730/01/02

88° 27' 30'' 

2000 

2200 

2400 

2600 

2800 

3000 

ADIT-3 

H.R.T. 3.3M.Ø H.S.SHAPE 

2000 

INCLINED PRESSURE SHAFT 1.5 M Ø 

SURGE SHAFT 10 M Ø 

RINGPI CHU 

3000 

SWITCHYARD 

(150M. X 115M.) 

T.R.T. 3.3 M Ø 

H.S.SHAPE 

TRANSFORMER 

CAVERN 

2800 

2600 

POWER HOUSE 

2400 

M.A.T. 

2200 

2000 

2400 

2200 

1800 

1800 

2000 

NOTES 


THIS DRAWING 



NO. 78A/6 (SCALE:- 1:50000) 



POWER HOUSE AREA 

LAY-OUT PLAN 

F/DCE730/01/02

FRL2966.00 

MDDL 2963.00 

EL 2955.00 

EL 2950.00 

TRESTLE 

EL 2970.0 

? 

? 

? 


(50M. X 5M.X7.5M.) 

? 

GATE OPERATION 

CHAMBER 

EL 2970.00 


(0.75M.X1.5M. D-SHAPE) 

STEEL LINED PRESSURE SHAFT 1.5M. Ø 

? 

HRT 3.3M. Ø H.S.SHAPE 

EL 2975.00M. 

SURGE SHAFT 

10M. Ø ? 

ADIT TO P.S. 

3.3M.Ø D-SHAPE 

EL 2926.60 

1 

250 

ADIT TO P.S. 

3.3M.Ø D-SHAPE 

EL. 1854.63 

? 

18000 

EL.1883.00 

BUS DUCT 

30000 

? 

POWER HOUSE CAVERN 

14000 

? 

TRANSFORMER CAVERN 

CABLE TUNNEL 

EL.1866.00 

T.R.T. 3.3M.Ø H.S.SHAPE 

C.C. BLOCKS 

NOTES: 


MAR.04 

TWL1853.00 

COFFERWALL 

1 ALL DIMENSIONS ARE IN MILLIMETERS AND LEVELS IN METERS. 

WATER CONDUCTOR SYSTEM 

L-SECTION 

PLATE NO.-6.5 

2 NO DIMENSION SHALL BE MEASURED FROM THIS DRAWING. 

F/DCE730/01/02

L8 

L7 

? 

L6 

? 

L5 

144000 30000 126000 

3000(TYP.) 

4000(TYP.) 

L4 

L3 

DAM TOP EL 2970.00 

? 

L2 

L1 

300000 

S3 

? 

S2 

S1 

UPSTREAM ELEVATION 

R1 

R2 

RADIAL GATE 4000 X 7000 

? 

NSL 

ANTICIPATED ROCK PROFILE 

R3 R4 R5 R6 

? 

NOTES: 

1 ALL DIMENSIONS ARE IN MM AND LEVELS IN METRES. 


MAR.04 

RAILING 

DAM 

UPSTREAM ELEVATION 

PLATE NO.-6.6 

2. NO DIMENSION SHALL BE MEASURED FROM THIS DRAWING. 

R7 

? 

F/DCE730/01/02

1 

1 

FRL EL. 2966.00 

MDDL EL. 2963.00 

STOPLOG GANTRY 

CRANE 

DAM TOP EL. 2970.00 

STOPLOG GATE GROOVE 

EL ±2930.00 

STEEL LINER 

CREST EL 2950.00 

RBL ±EL 2940.00 

GROUT CURTAIN HOLES 

? 

DAM AXIS 

ROAD 

FOUNDATION 

GALLERY 

DRAINAGE HOLE 

BREAST WALL 

AIR VENT PIPE 

EL. 2957.00 

RADIAL GATE(4M. X 7M.) 

HIGH PERFORMENCE CONC. 

BUCKET INVERT EL 2943.00 

TRUNION BEAM 

? ? ? ? ? 

SPILLWAY- MAXIMUM SECTION 

1 

1 

NORMAL T W L 

7000 LONG ROCK ANCHORS 

@1500 c/c STAGGERED 

1 

1 

CONCRETE APRON 

MAX. T W L 

COMPACTED BACKFILL 

DAM TOP EL 2970.00 

FRL EL 2966.00 

MDDL EL 2963.00 

1 

EL. VARIES 

0.1 

? 

DAM AXIS 

NON- OVERFLOW SECTION 

NOTES: 

1 ALL DIMENSIONS ARE IN MM AND LEVELS IN METRES. 


MAR.04 

0.8 

? ? 

2 NO DIMENSION SHALL BE MEASURED FROM THIS DRAWING. 

1 

DAM 

SPILLWAY & NON-OVER FLOW 

CROSS-SECTION 

PLATE NO.-6.7 

F/DCE730/01/02

HRT3.3 M. Ø 

Ø3300 

Ø10000 

TYP. SECTION - SURGE SHAFT 

2000 LONG 25 Ø ROCK BOLTS/ 

ANCHORS 1000 c/c 

Ø1650 

Ø3300 

TYP. SECTION - HRT 

CONC. LINING 225 THK. 

50 THK. 

SHOTCRETE 



100 THK. SHOTCRETE 

WITH WIREMESH 

CONC.LINING 750 THK. 

PRESSURE SHAFT 

7500 

5000 

SECTION - DESILTING CHAMBER 

Ø1500 

1.5 

1 


ANCHORS 1000 c/c(IF REQUIRED) 

32Ø 5000 LONG ROCK BOLTS / 

ANCHORS @ 2000 c/c 

BACK FILL 750 THK. 

STEEL LINER 

50THK. 

SHOTCRETE 

100 THK. SHOTCRETE 

WITH WIREMESH 

R.C.C. LINING 300 THK. 

32Ø 5000 LNG ROCK BOLTS/ 

ANCHORS @ 1500 c/c 

TYP. SECTION - DIVERSION TUNNEL 

NOTE :- 

1 ALL DIMENSIONS AREIN MILIMETRES AND LEVELS 

IN METRE UNLESS OTHERWISE SPECIFIED. 

2 NO DIMENSION SHALL BE MEASURED FROM THIS 

DRAWING. 

PRE-FEASIBILITY REPORT DRAWING 

TYPICAL CROSS SECTION 

OF CONSTITUENTS OF WATER 

TYP. SECTION - PRESSURE SHAFT CONDUCTOR SYSTEM & DIVERSION TUNNEL 

Ø3300 



Ø1650 

Ø3300 

MAR.2004 

CONC. LINING 225 THK. 

50 THK. 

SHOTCRETE 


00 

F/DCE/730/01/02

220KV 

BUS1 

BUS CVT-1 

220kV 

BUS-II 

BUS CVT-2 

FUTURE 

CVT 

EX. Tr. 

NGT 

UNIT -II 

S.A. 

XLPE CABLE 

GSU Tr. 

SC 

SA 

G-II 

PT 

PT 

UAT 

64G1 

64G2 

TO 220KV 

FEEDER-1 

PTSP 

CVT 

BUS 

COUPLER 

EX. Tr. 

NGT 

UNIT -I 

S.A. 

XLPE CABLE 

GSU Tr.1Ø,15 MVA 

11/ 220/ 3 KV 

64G1 

64G2 

TO 220KV 

FEEDER-2 

UAT 

11 / 0.415KV,500KVA 

SC PTSP 

SA 

PT 

PT 

G-I 

35 MW,11 KV 

FOR 

METERING & 

PROTECTION 

FOR 

DVR DUPLICATE 

PROTECTION 

CVT 

SA 

S.A. 

VED PAL 

JAN, 2004 

SINGLE LINE DIAGRAM 

BHU DEV 

V.K.SINGH 

NH/DEM/RIN/SLD/01 

PLATE 8.1 

00



ANNEXURES

Annexure 4.1 

GEOLOGY OF THE AREA AROUND THE PROPOSED RINGPI 

HYDROELECTRIC PROJECT, TEESTA BASIN, SIKKIM 

INTRODUCTION 

The Central Electricity Authority (CEA), as a part of an exercise to 

estimate the balance hydroelectric potential in the county have identified 399 

schemes with installed capacity of about 1,50,000 MW in various river basins. 

The schemes thus identified were subjected to ranking studies applying different 

parameters. On the basis of ranking studies 162 schemes with probable 

installed capacity of 50,600 MW spread over 16 States have been selected for 

preparation Pre-Feasibility Reports (PFR’s) in first phase. The schemes found 

feasible are proposed to be taken up for further development during X and XI 

Five Year Plans. 

The proposed Ringpi Hydroelectric Project is one of the ten schemes 

located in Teesta Basin in Sikkim. As per the layouts provided by National 

Hydroelectric Power Corporation (NHPC), this run river scheme includes 

construction of diversion dam / weir across Ringpi Chhu downstream of Tolung 

(27 O 40’ 35” N: 88 O 26’ 37”E, 78 0/6), a water conductor system including 7.2 km 

long head race tunnel (HRT) and powerhouse with probable installed capacity 

of 160 MW located on the right bank of Ringpi Chhu upstream of Myong (27 O 37” 

21’ N: 88 O 27” 09’ E, 78 0/6 ). 

REGIONAL GEOLOGY 

The area around the proposed project is located in North Sikkim in Central 

Crystalline axial region and is characterised by sharp crested snow bound 

mountains. The ridges trend both in E-W and N-S directions. Teesta River,

main draining agency of Sikkim flows almost N-S in the area. The important 

tributaries of Teesta are Lach Chhu, Toloung Chhu Chakung Chu, Ringpi Chu 

and their numerous tributaries. The valleys of rivers are U-shaped and small 

streams have formed deep gorges. Vegetation is observed up to EI . 3.900 m 

and many lakes are present at high altitudes. 

The area around the proposed project has been mapped by Raina (1966) 

Chakraborti and Banerjee (1982), Kumar et al (1984), Neogi et al (1984) and 

Neogi et al (1986). The stratigraphic sequence established by the officers of GSI 

on the basis of geological mapping is given below: 

GROUP LITHOLOGY 

Gondwana Grits, pebble cum boulder beds 

2 

and carbonaceous shales with 

occasional coal seams, pegmatite, 

quartzite (Tourmaline bearing) 

Daling Inter bedded quartzite and chlorite 

sericite phyllite / schist. 

Lingza Granite 

Quartzite/Biotite schist 

Chungthang Interbedded quartzite and 

Central Crystalline Gneissic 

Complex 

garnetiferous quartz biotite schist . 

Calc – silicate rock / marble. 

Garnet – kyanite – sillimanite – 

biotite – quartz – schist. 

Banded gneiss with augen gneiss 

and quartz – biotite gneiss. 

Augen gneiss

The area falls within axial belt of Central Crystalline Zone of the North 

Sikkim Himalayas where the rock types are mainly high grade gneisses (CCGC) 

having interbands of metasedimentaries represented by calc – silicate / 

quartzite, high grade schists and their fine inter laminations. The 

metasedimentaries occur as enclaves in the high-grade gneisses in the area 

around the proposed project. All these rock types are often intruded by 

discordant tourmaline bearing quartz veins and pegmatite. 

The higher grade gneisses belonging to the Central Crystalline Gneissic 

Complex (CCGC) Group vary in composition from a gneiss in which feldspar is 

predominant with respect to quartz to quartz biotite gneiss in which feldspar is 

almost absent (Chakraborti & Banerjee, 1982 and Neogi et al, 1986) with 

frequent association of garnet, tourmaline and sillimanite / kyanite depending up 

on bulk chemical composition. While the former type is well foliated with streaks 

of biotite, the latter is compact and poorly foliated. The different types of these 

gneisses occurring at different structural levels are banded gneiss, augen gneiss 

and streaky gneiss. A gradual passage from one type to other type, both 

vertically and laterally, is rather common. The banded type is characterized by 

alternate bands of quartz feldspar and biotite. These bands are at places 

stretched giving rise to augens which are composed predominantly of single 

grains of feldspar or occassionally quartz or their aggregate. The latter may be 

the result of metamorphic differentiation. The augens are both deformed or 

undeformed and are invariably warped around by biotite flakes defining the 

gneissic – foliation. The augens are stretched in the direction of regional 

schistosity. The high grade gneisses are often intruded by tourmaline granite at 

places and are associated with interbands of calc silicate – quartzite and 

garnetiferous biotite schist and various other schists belonging to Chungthang 

Group. These have locally been mapped as Kanchendzonga Gneiss, 

Chungthang Gneiss and Darjeeling Gneiss by various workers earlier. According 

to Neogi et al (1986), there exists a complete gradation both laterally and in down 

dip direction amongst above mentioned gneisses. Their repetition is due to 

3

normal morphological variation and unlinked with folding and thrusting. Various 

structura/textural types of these gneisses stated above have also been observed 

in all the so called gneissic groups of Central Crystalline axial region and have 

been referred as “High Grade Gneisses” of Central Crystalline Belt which are 

also comparable to Darjeeling Gneisses of Lesser Himalayas. 

The metasedimentaries of the area belonging to the Chungthang Group 

are represented by a sequence of lithounits varying from calcareous to 

arrnaceous and argillaceous lithofacies. These comprise calc silicate rocks, 

quartzite, high grade micaceous schists occasional amphibolites and their fine 

grained interlaminations. 

Neogi et al (1986) have clubbed together calc silicate rocks and quartzites 

as these invariably occur together. Prominent bands of these rocks have been 

observed near Be and Myong, north of Talung gompa and near Phygn and south 

of Kishong. These have NE-SW trend are locally folded. Calcareous bands are 

easily identified by their greenish colour within banded calc silicate / quartzite 

assemblage. Apart from carbonates and quartz, stumpy diopside and needle 

shaped tremolite have also been observed in these. Garnet is generally leached 

giving rise to ferruginous staining. The quartzite is sericite quartzite. Thin 

laminations of biotite are observed in quartzite at places. The rocks are 

occasionally boudinaged. Carbonaceous biotite schist is found associated with 

southern west calc silicate / quartzite band. Tourmaline bearing silica veins and 

pegmatites have been observed occasionally intruding these rock types. 

Daling Series of Raina (1966) having two zones viz phyllite zone and 

schistose zone has been mapped as low grade metamorphites of Daling Group 

by Kumar et al (1984). Daling Group comprises quartz – chlorite – sericite schist 

phyllite, quartz – sericite schist, quartz chlorite phyllite often associated with thin 

interbands of quartzite. The low grade sedimentaries belonging to Daling 

Series from southern part of the area structurally underlie the Lingtze Granite 

4

Gneiss. Near Gyathang and at some other places, the frequency of presence of 

garnet is slightly higher and its grain size is controlled by the original bulk 

composition of the rock. According to Kumar et al (1984) these 

metasedimentaries typically resemble the Gorubathan Formation of Daling Group 

and hence been named “low Grade Daling” . 

The granite gneiss which crops out near north of Senkhalang with an E-W 

trend and northerly dips is also observed NW of Kendong and north of Karsang 

to form the western limb of major antiformal closure. It occupies a unique 

position between low-grade and high-grade metasedimentaries and is 

conformable to both. This granite is a well foliated, coarse grained, sheared 

streaky biotite gneiss and occasionally contains garnets. At places, augens of 

quartz and felspar stretched parallel to the foliation plane are recorded within 

this unit. 

Tourmaline and biotite bearing granites are the younger granites having 

discordant relationship with high-grade gneisses and high-grade 

metasedimentaries. Compositionally, these are mainly quartz-feldspar rich 

leucogranite varying from coarse grained to fine grained aplitic variety and shows 

disseminated flakes of biotite. Tourmaline grains are observed generally in 

structural highs. 

Gondwanas, according to Raina (1966) include grits, pebble cum boulder 

beds and carbonaceous shales with ocassional coal seams. Pebble cum boulder 

bed forms the marker horizon for Gondwana. Arkosic sandstone (felspathic grit) 

forms the other main rock type. It is light yellow to dark grey coloured and is 

infolded within pebble beds. 

5

STRUCTURE AND TECTONICS 

The area exposes a sequence of gneissic rocks and associated 

metasedimentary rocks of Central Crystalline Belt of North Sikkim and the 

structural fabric elements observed pertain to features in the area predominated 

by high grade litho-facies which have undergone polyphase deformation and 

metamorphism. The primary structures include compositional banding. The 

gneisses show lithological banding which can be attributed to metamorphic 

differentiation. Bedded characters are observed only in calc silicate – quartzite 

multilayers. The high-grade schists also show compositional banding of alternate 

quartz rich and calc silicate rich bands. There is no evidence however to indicate 

that these bandings are relict of primary sedimentary banding. However, broad 

parallelism of the bandings and later imposed pervasive planes, S2, indicates 

that these could be transposed. 

The secondary structures include planar surfaces like gneisses foliation, 

schistosity which include bedding schistosity (S1), regional schistosity (S2) and 

fracture cleavage (S3). Bed Gneissic foliation forms the most prominent fabric 

element of high grade metamorphic tectonics. These ‘S’ surfaces are marked by 

parallel lithological layering and preferred dimensional orientation of minerals. 

The gneissic foliation in the area generally trends NE-SW with moderate NW 

dips. 

The metasedimentaries associated with the gneisses show a pervasive 

schistosity where lithological layering is absent. The fabric is defined by 

preferred orientation of tabular mica crystals. Bedding schistosity (S1) is 

incipient and is parallel to the compositional banding in metasedimentaries. This 

‘S’ surface could not be related to any tectonic structure in the area and could be 

described as another inherited fabric element along with bedding. The regional 

schistosity (S2) is most pervasive structural element in metasedimentaries. The 

axial plane schistosity is symmetrically oriented with respect to axial planes of 

6

folds (F1). The trend of regional schistosity is parallel to the gneissic foliation. 

The fracture cleavage (S3) is defined by discrete parallel fractures and are also 

axial plane cleavages related to F2 crenulation. Due to varying styles of the F2 

folds the orientation of the S3 surfaces varies with respect to regional schistosity 

‘S2’. The linear structurs include striping lineation, pucker axis lineation and 

mineral lineation. 

The area comprises a sequence of high-grade metasedimentaries and 

gneisses that show evidence of having undergone polyphase deformation with 

complex pattern of folds due to repeated super-imposition of successive fold 

forms. Grouping of different generations of folds on the basis of styles and 

spatial attitudes has not been possible due to their complex forms. Broadly three 

generations of fold movement could be deciphered. F1 folds, the earliest 

recognizable folds have compositional banding and bedding schistosity as their 

form surface and are of tight isoclinal reclined to inclined folds. Their style and 

spatial orientation as observed in the area is comparable to these observed in 

Daling Group of rocks exposed south of present area. The F2 folds have 

involved all the above mentioned surfaces. These show a variety of styles 

ranging from appressed isoclinal folds to open warps, small-scale chevron folds 

or multi-hinged disharmonic folds. The calc silicate / marble quartzite bands 

show regional warps along NW-SE axis due to this phase of folding. The effects 

of F3 folds have been observed mainly on regional scale. On macro scale they 

are of the nature of minor broad warps that have folded the weakly developed S3 

planes. No planar surface related to this phase of folding are apparent. F3 warps 

are only locally developed in high-grade metasedimentaries and have N-S 

oriented axis. 

Zones of intense mylonitisation have been observed in the gneisses but 

there is no basis to conclude that these could represent planes of thrusting on 

the basis of evidence like distinct truncation of lithounits reorientation of major 

folds (F2), development of small scale faults etc.. Chakraborty and Banerjee 

7

(1982) have marked NNW-SSE trending thrust near Manual and NW-SE trending 

thrust near Naga. Neogi et al (1984) observed minor slips and faults occurring 

commonly within gneisses and metasedimentaries along S3 planes near hinge 

zone of F2 folds. The slips are more common where folds are tight. A meso 

scale normal vertical fault trending N-S has been found with in low grade 

metasedimentaries about 2 km north of Brang village. Silicification, chloritization 

and mylonitization are found along this fault plane. 

SEISMOTECTONICS AND SEISMICITY 

Seismotectonically the area under reference is located in Axial Belt of 

Central Crystalline Zones of North Sikkim. According to Narula at al (2000) the 

northern part of the area is occupied by poorly metamorphosed sequence 

(Tethyan) folded during Himalayan Orogeny. Similar tectonic pockets 

representing Gondwana sequence crop out within Rangit Window as well as 

lenticular tectonic wedge along the Main Boundary Thrust (MBT). The northern 

Tethyan Belt is followed successively to the south by high-grade complex of 

Central Crystallines and low-grade complex of Lesser Himalayan rock worked 

during Himalayan Orogeny. The latter packet is exposed within tectonic windows 

as well as linear belt between Main Central Thrust (MCT) and MBT. South of 

MBT the foot hill region is occupied by sequence of frontal belt affected by the 

terminal phase of the Himalayan Orogeny. Adjacent Peninsular tract is covered 

by Quaternary alluvial fill along the foredeep. In the southwestern part, 

Peninsular element is represented by small inliers of gneissic complex and 

Rajmahal Trap. The basement gneissic complex, representing a part of Shillong 

massif along with marine transgressive cover are present in south eastern part. 

Like other parts of Himalayas, this area is the high grade Central Crystallines 

from comparatively lower grade Lesser Himalayan packages which are 

separated from the Siwalik Belt by MBT. At places, particularly towards east, 

several subsidiary thrust are presented between MCT and MBT. Besides these, 

several approximately N-S trending gravity faults are present particularly within 

8

northern Tethyan Belt and the southern foot hill belt. Within northern Tethyan 

Belt these N-S faults define some well knows graben structures, viz. Pum Qu 

Graben and Yadong Gulu Graben. In the former, the faults affecting the 

Quaternary glacial deposits are clearly evident. The latter graben is considered 

to be longest one in Tibetan Plateau and is segmented into several N-S smaller 

grabens. The foredeep tract east of Munger – Saharsha Ridge is known as 

Purnia Basin where Gondwana sequence has developed over the rifted 

basement. The structural configuration of this foredeep region is architectured by 

a set of almost N-S trending faults resulting in development of alternate horst and 

graben structures. The westernmost is the Munger – Saharsha Ridge which 

alternates towards east by Purnia Basin. The western and eastern boundaries of 

Purnia Basin are defined by the Munger - Saharsha Ridge Morginal Fault 

(MSRF) and Malda Kishanganj Fault (MKF). The former fault known as Sainthia 

– Brahmani Fault further south, along which cluster of earthquakes have been 

recorded by the Geological Survey of India, has been found seismically active. 

Further east the prominent tectonic feature is the Rangpur Ridge bound by MKF 

and Jangipur – Goribandha Fault, Teesta Fault and Katihar – Nailphamari Fault. 

Several subsidiary faults, parallel to Teesta Fault forming grabens are reported 

from ridge. Gondwana sequence is found to have developed within these 

grabens. Along with transverse faults, several lineaments cutting across the 

Himalayan belt are also present. These exhibit NE and NW trends. The NE 

trending Azun Lineament considered to be trace of northern extension of East 

Patna Fault, Kanchanjunga Lineament and NW-SE trending Teesta and Purnia 

lineaments are other prominent transverse lineaments. The basement contours 

corroborate the presence of Purnia Saddle and Rangpur Ridge. 

Most of the earthquakes in this area are shallow focus (

subdued seismicity. Of the 51 seismic events recorded in the region over a 

period of 58 years between 1935 and 1993, five had magnitude more than 5.5 

i.e. ranging between 5.5 and 6.0 and rest 46 had magnitude between 4.5 and 5.5 

and 8 events with depth of focus >40 km. The depth of focus for one event, that 

of 21.05.1935, has been interpreted to be 140 km. As such observed seismic 

events are mostly concentrated in Main Himalayan Belt. Keeping in view the 

seismotectonic set up and seismicity, the area has been kept in Zone – IV as per 

Map of India Showing Seismic Zones (IS - 1893 (part –I) : 2002). 

GEOTECHNICAL APPRAISAL 

The geological map of the area indicates that the proposed project would 

be located in the Axial Belt Central Crystalline Zone of North Sikkim. The area 

exposes banded gneiss with augen gneiss and quartz biotite gneiss belonging to 

Central Crystalline Gneiss Complex having associated interbands of calc silicate 

rock / marble and quartzite / biotite quartz schist belonging to high grade 

metasedimentaries of Chungthang Group. The foliation is well developed and 

trends in NNW-SSE to NNE-SSW direction. The rocks are jointed and traversed 

by joints and shared / mylonitised zones. 

The site of the proposed diversion structure across Ringpi Chhu is located 

downstream of Tolung and exposes banded gneiss with augen gneiss and quartz 

biotite gneiss. The foliation trends N-S and dips steeply towards east. It is 

recommended that the final location and type of the structure be decided after 

assessing the extent of overburden in river bed and on abutments and availability 

of suitable site for locating intake structure for water conductor system. The 

proposed water conductor system comprising 7.2 km long head race tunnel 

(HRT) is envisaged on the right bank of Ringpi Chhu. The HRT is likely to 

encounter the gneisses belonging Central Crystalline Gneiss Complex in the 

major portion and bands of calc silicate rock / marble in some reaches. These 

rocks are likely to be good to fair tunneling media except for reaches where 

10

mylotinised / shear zones are encountered. The conditions in such zones are 

likely to be fair to poor. The preliminary layout of the project shows that there is 

no possibility of having an intermediate construction adit if the present alignment 

of HRT is retained. It is suggested that if required, possibility of having one 

construction adit may be looked into by giving a kink in the alignment and shifting 

the HRT towards valley in the middle reaches. However, the adequacy of the 

rock cover has to be ensured while carrying out such an exercise. The proposed 

powerhouse with installed capacity of 160 MW is envisaged on right bank of 

Ringpi Chhu upstream of Ishong. The area exposes gneisses belonging to 

CCGC. The foliation trends NE-SW with moderate dips towards NW. Keeping 

in view the topography and rock types present in the area it is suggested that the 

structure be designed as an underground one. The project area is located in 

Zone –IV as per Map of India Showing Seismic Zones (IS – 1893 (part-I) : 2002). 

Therefore, seismic coefficient as required for the area will have to be 

incorporated in the designs of appurtenant structures of the project. This 

preliminary geotechnical appraisal is based on regional geological set up of the 

area without field visit to the project site. 

REFERENCES 

Chakraborti, B., and Banerjee, H., (1982). Geology and Structure of the Area 

around Chungthang - Mangan – Tolung, North Sikkim. Unpubl. Prog. Rep. 

Geological Survey of India, F.S. 1980-81. 

Kumar, J.P., and Mitra, P.K. (1984). Geology and Structure of the Area Around 

Sakkyong, Mangan, Dikchu, Lingi and Mangka Covering Parts of North South 

and East Sikkim. Unpubl. Prog. Rep. Geological Survey of India, F.S. 1982-83. 

Narula, P.L. Acharayya, S.K., and Banerjee, J., (Eds) (2000). Seismotectonic 

Atlas of India and its Environs, GSI Publication. 

11

Neogi S., Purkaint, B. and Samaddar, A.K. (1984). Geology of the Area Around 

Tashiding – Lapdang – Maidang La-Karshang – Lampokhari – Khungre, West 

District, Sikkim. Unpubl. Prog. Rep. Geological Survey of India, F.S. 1982-83. 

Neogi, S., Kumar, J.P., Mitra, N.D., Samaddar, A.K. and Dawande, A.K. (1986). 

Geology of the Area Around Tolung – Thijp, - Kishong, North Sikkim District, 

Sikkim. Unpubl. Geological Survey of India Prog. Preg., F.S. 1983-84. 

Raina, U.K. (1966). Geological Mapping in the western part of Sikkim. Unpubl. 

Geological Survey of India, Rep., F.S. 1965-66. 

12

1 

Annexure-4.2 

TECHNICAL REPORT ON SEISMIC HISTORY AND SEISMICITY OF THE 

TEESTA BASIN OF SIKXKIM COVERING PROPOSED SITES FOR 

HYDROELECTRIC SCHEMES 

Historical and instrumentally recorded data on earthquakes show that the whole area of 

the proposed sites for hydroelectric schemes at Dikchu, Rongni Storage, Panan, 

Namlum, Zedang, Teesta St-I, Ringpi, Lingza, Rukel and Rangyong in Sikkim lies in a 

region liable to damage due to moderate to great earthquakes. Noteworthy earthquakes 

which affected the region in the past are (i) the Cachar earthquake of 10.01.1869 

(Magnitude= 7.5 on Richter scale), (ii) the Shillong plateau earthquake of 12.06.1897 

(Magnitude= 8.7), (iii) the Dhubri earthquake of 02.07.1930 (Magnitude= 7.1), (iv) the 

Bihar-Nepal Border earthquake of 15.01.1934 (Magnitude= 8.3), (v) the Assam 

earthquake of 15.08.1950 (Magnitude= 8.5) and (vi) the Nepal-India Border earthquake 

of 21.08.1988 (Magnitude= 6.4). The 1897 earthquake had its epicentral tract in and 

around Shillong where there was considerable damage to lives and property, in addition 

to other effects of very strong ground shaking. One of the significant observations made 

on this earthquake was that boulders were thrown out vertically upwards from their 

original places showing that the force of earthquake motion exceeded the force due to 

gravity, at least momentarily. The earthquake was followed by a large number of 

aftershocks. 

In addition to the above significant earthquakes, the region has experienced 

several earthquakes of lesser intensity originating within a radius of 450 km around 

Shillong and neighbouring regions. A list of important earthquakes from I.M.D. 

catalogue occurred in the region bounded by Lat. 25.00 to 30.00°N and Long. 86.00 to 

91.00°E for the period 1505 to 2001 is enclosed. 

The occurrence of earthquakes in Sikkim region is broadly associated with the 

tectonic activity along the well-known faults in the Himalayas such as the Main 

Boundary Thrust (MBT) and the Main Central Thrust (MCT). Besides, earthquakes 

occurring along some other faults namely Malda-Kishanganj Fault, Tista Fault, Purnia- 

Everest Lineament, Katihar-Nailphamani Fault, Dhubri Fault etc. have also affected the 

region. 

In the seismic zoning map of India prepared by a committee of experts under the 

auspices of Bureau of Indian Standards (BIS: 1893: Part I 2002), the entire area of 

Sikkim has been placed in the zone IV. The seismic zone IV is broadly associated with 

a seismic intensity VIII on Modified Mercalli (MM) scale. It may be mentioned that the 

seismic intensity VIII corresponds to a horizontal ground acceleration range of 51- 

350cm/sec 2 or an average acceleration of 172cm/sec 2 in any direction. The ground 

acceleration and hence the intensity of an earthquake at a place depends on magnitude 

of earthquake, distance from the focus, duration of earthquake, type of underlying soil 

and its damping characteristics and liquefaction potential. The damage to the buildings

founded on sandy soil is higher than that in the similar type of buildings having their 

foundation on hard bedrock. Also, the damage will be higher for higher magnitude and 

long duration earthquakes, less epicentral distance soft soil conditions and area with 

high liquefaction potential. 

Presently, there is no scientific technique available anywhere in the world to predict 

occurrence of earthquakes with reasonable degree of accuracy with regard to space, 

time and magnitude. It is, therefore suggested that appropriate steps may be taken to 

ensure that the dwellings and other structures in the region are designed and constructed 

as per guidelines laid down by Bureau of Indian Standards (BIS) to minimize the losses 

caused by earthquakes. Suitable seismic design parameters may be adopted as per 

recommendations of National Committee on Seismic Design Parameters (NCSDP) 

for designing and engineering Hydroelectric Projects. 

EXPLANATION OF COMPUTER OUTPUT (IMD CATALOGUE) 

1. “O” – Time means time of Origin of Earthquake in UTC. 

2. “Depth” means Focal Depth in Kilometers. If depth is reported as 33, it means 

that the earthquake is located in the crust but its focal depth could not be 

determined. 

3. “MAG” means magnitude on Richter scale. 

4. “Zero” under any column means that the parameters have not been determined. 

2

MODIFIED MERCALLI INTENSITY SCALE (ABRIDGED) 

CLASS OF REMARKS 

EARTHQUAKE 

I Not felt except by a very few under specially favourable circumstances. 

II Felt only by a few persons at rest, specially on upper floors of buildings; and 

delicately suspended objects may swing. 

III Felt quite noticeably indoors, specially on upper floors of buildings but many 

people do not recognize it as an earthquake; standing motor cars may rock 

slightly; and vibration may be felt like the passing of a truck. 

IV During the day felt indoors by many, outdoors by a few, at night some 

awakened; dishes, windows, doors disturbed; walls make creaking sound, 

sensation like heavy truck striking the building; and standing motor cars rocked 

noticeably. 

V Felt by nearly everyone; many awakened; some dishes, windows, etc. broken; a 

few instances of cracked plaster; unstable object overturned; disturbance of 

trees; polls and other tall objects notices sometimes; and pendulum clocks may 

stop. 

VI Felt by all, many frightened and run outdoors; some heavy furniture moved; a 

few instances of fallen plaster or damaged chimneys and damaged slight. 

VII Everybody runs outdoors, damage negligible in buildings of good design and 

construction; slight to moderate in well built ordinary structures; considerable 

in poorly built or badly designed structures; and some chimneys broken, noticed 

by person driving motor cars. 

VIII Damage slight in specially design structures; considerable in ordinary but 

substantial buildings with partial collapse; very heavy in poorly build structures; 

panel walls thrown out of framed structured; falling of chimney, factory stacks, 

columns, monuments and walls; heavy furniture overturned, sand and mud 

ejected in small amounts; changes in well water; and disturbs person driving 

motor cars. 

IX Damage considerable in specially designed structures: well designed framed 

structures thrown out of plumb; very heavy in substantial buildings with partial 

collapse; buildings shifted off foundations; ground cracked conspicuously; and 

underground pipes broken. 

3

X Some well built wooden structures destroyed; most masonry and framed 

structures with foundations destroyed; ground badly cracks; rails bent; 

landslides considerable from river banks and steep slopes; shifted sand and mud; 

and water splashed over banks. 

XI Few, if any, masonry structures remain standing; bridges destroyed; broad 

fissures in ground, underground pipelines completely out of services; earth 

slumps and landslips in soft ground; and rails bent greatly. 

XII Total damage; waves seen on ground surfaces; lines of sight and levels distorted; 

and objects thrown upward 

4

LIST OF EARTHQUAKES FROM IMD CATALOGUE OCCURING BETWEEN LAT25 . 00 TO 30 . 00 

DEG. AND LONG 86 . 00 TO 91 . 00DEG. E FOR THE PERIOD 1505 TO 2001 

DATE 

O-TIME LAT LONG DEPTH MAG 

Y M D Hr Mn Sec Deg-N Deg-E Km 

1833 8 26 0 0 . 0 27 . 50 86 . 50 0 . 7 . 5 

1834 7 8 0 0 . 0 25 . 80 89 . 40 0 . 6 . 3 

1834 7 21 0 0 . 0 25 . 80 89 . 40 0 . 6 . 0 

1842 2 5 21 15 . 0 25 . 00 87 . 00 0 . 5 . 5 

1842 11 11 0 0 . 0 25 . 00 90 . 00 0 . 6 . 5 

1843 8 10 0 0 . 0 27 . 00 88 . 30 0 . 5 . 5 

1849 2 27 0 0 . 0 27 . 00 88 . 30 0 . 6 . 0 

1852 5 0 0 0 . 0 27 . 00 88 . 00 0 . 6 . 5 

1897 6 12 11 6 . 0 25 . 90 91 . 00 0 . 8 . 7 

1899 9 25 0 0 . 0 27 . 00 88 . 30 0 . 6 . 0 

1909 2 17 0 0 . 0 27 . 00 87 . 00 0 . 5 . 0 

1918 2 4 17 54 49 . 0 29 . 60 87 . 80 0 . 6 . 0 

1923 4 24 22 3 6 . 0 29 . 60 87 . 80 0 . 5 . 5 

1923 9 9 22 3 42 . 0 25 . 30 91 . 00 0 . 7 . 1 

1926 12 4 11 15 23 . 0 29 . 60 87 . 80 0 . 6 . 0 

1930 7 2 21 3 34 . 0 25 . 80 90 . 20 0 . 7 . 1 

1930 7 3 0 19 5 . 0 25 . 80 90. 20 0 . 5 . 5 

1930 7 4 18 54 44 . 0 25 . 80 90 . 20 0 . 5 . 5 

1930 7 4 21 34 . 0 25 . 80 90. 80 0 . 5 . 5 

1930 7 8 4 32 24 . 0 25 . 80 90 . 80 0 . 5 . 5 

1930 7 8 9 43 . 0 25 . 80 90. 80 0 . 5 . 5 

1930 7 13 14 0 12 . 0 25 . 80 90 . 80 0 . 5 . 5 

1932 3 24 16 8 44 . 0 25 . 80 90 . 20 0 . 5 . 5 

1932 3 25 4 29 32 . 0 30 . 00 89 . 20 0 . 5 . 5 

1933 3 6 13 5 38 . 0 25 . 70 90 . 50 0 . 5 . 8 

1934 1 15 8 43 25 . 0 26 . 60 86. 80 0 . 8 . 3 

1934 1 16 4 59 22 . 0 28 . 00 86 . 00 0 . 5 . 6 

1934 7 21 0 0 . 0 25 . 80 89 . 40 0 . 5 . 5 

1935 5 21 4 22 31 . 0 28 . 80 89 . 30 140 . 6 . 3 

1936 5 30 7 8 38 . 0 25 . 70 90 . 50 0 . 5 . 3 

1936 6 9 0 2 42 . 0 27 . 50 87 . 00 0 . 5 . 5 

1936 6 18 14 56 27 . 0 26 . 60 90 . 30 0 . 5 . 8 

1936 9 7 2 30 49 . 0 27 . 50 87 . 00 0 . 5 . 7 

1937 8 15 11 36 48 . 0 30 . 00 90 . 00 0 . 5 . 8 

1938 1 29 4 13 8 . 0 27 . 50 87 . 00 0 . 5 . 8 

1938 2 26 12 10 43 . 0 28 . 00 90 . 50 0 . 5 . 7 

1938 4 13 1 10 17 . 0 26 . 00 91 . 00 0 . 5 . 2 

1939 6 4 22 36 . 0 28 . 50 86 . 50 0 . 5 . 7 

5

1940 8 2 3 3 59 . 0 28 . 00 90 . 50 0 . 5 . 2 

1945 5 19 5 2 53 . 0 25 . 10 90 . 90 0 . 6 . 1 

1949 12 10 19 37 14 . 0 26 . 00 89 . 00 0 . 6 . 0 

1950 2 26 3 35 48 . 0 28 . 00 90 . 50 0 . 6 . 0 

1951 4 7 20 29 12 . 0 25 . 90 90 . 50 0 . 6 . 8 

1951. 5 28 15 59 19 . 0 29 . 00 87 . 00 0 . 6 . 0 

1952 3 6 9 11 23 . 0 29 . 60 90 . 80 0 . 5 . 5 

1952 11 19 10 23 28 . 0 29 . 80 86 . 60 0 . 6 . 0 

1955 3 27 14 38 43 . 0 29 . 90 90 . 20 0 . 6 . 3 

1958 11 23 20 15 48 . 0 28 . 79 86 . 94 0 . 5 . 5 

1959 6 10 4 25 15 . 0 30 . 00 91 . 00 0 . 5 . 7 

1960 7 29 10 42 44 . 6 26 . 90 90 . 30 11 . 6 . 5 

1960 8 21 3 29 4 . 9 27 . 00 88 . 50 29 . 5 . 5 

1961 9 29 22 36 30 . 0 28 . 00 87 . 00 0 . 5 . 5 

1961 12 25 11 19 10 . 0 27 . 00 90 . 00 0 . 5 . 5 

1963 2 22 1 32 30 . 0 27 . 20 87 . 10 0 . 5 . 2 

1964 2 1 11 28 19 . 2 27 . 30 87 . 78 33 . 4 . 8 

1964 3 27 23 3 41 . 1 27 . 13 89 . 36 29 . 5 . 0 

1964 4 13 3 19 57 . 3 27 . 52 90 . 17 1 . 5 . 2 

1964 8 30 2 35 7 . 3 27 . 36 88 . 21 21 . 5 . 1 

1964 11 9 16 12 51 . 9 29 . 53 86 . 04 33 . 5 . 0 

1965 1 12 13 32 24 . 1 27 . 40 87 . 84 23 . 5 . 8 

1965 1 12 13 55 18 . 1 27 . 31 87 . 68 18 . 5 . 2 

1967 3 2 11 47 13 . 0 28 . 70 86 . 38 20 . 4 . 8 

1968 8 18 14 18 58 . 0 26 . 42 90 . 62 22 . 5 . 1 

1968 10 28 17 48 30 . 1 27 . 57 86 . 03 37 . 4 . 9 

1969 11 5 20 25 13 . 7 27 . 66 90 . 24 13 . 5 . 0 

1970 7 25 1 35 26 . 0 25 . 72 88 . 58 32 . 5 . 1 

1971 10 24 8 59 6 . 3 28 . 30 87 . 19 57 . 4 . 8 

1971 10 31 15 54 48 . 2 26 . 18 90 . 65 33 . 4 . 7 

1971 12 4 8 38 . 2 27 . 92 87 . 95 29 . 5 . 2 

1972 8 21 14 4 34 . 2 27 . 33 88 . 01 33 . 4 . 5 

1972 11 6 10 56 13 . 5 26 . 88 88 . 43 59 . 4 . 4 

1973 3 22 1 6 57 . 4 28 . 12 87 . 15 33 . 5 . 0 

1973 8 1 14 5 15 . 5 29 . 59 89 . 17 63 . 4 . 9 

1974 3 24 14 16 1 . 1 27 . 66 86 . 00 0 . 5 . 4 

1974 3 24 16 17 35 . 3 27 . 63 86 . 01 3 . 4 . 7 

1975 1 23 1 37 42 . 6 27 . 44 88 . 37 33 . 4 . 5 

1975 2 6 6 39 48 . 7 27 . 95 87 . 67 63 . 4 . 7 

1975 4 24 1 35 51 . 2 27 . 44 87 . 04 26 . 4 . 9 

1975 6 24 15 38 28 . 1 27 . 74 87 . 50 33 . 4 . 8 

1975 11 21 13 49 27 . 9 26 . 96 86 . 54 0 . 4 . 9 

1975 11 26 15 2 31 . 1 28 . 15 87 . 80 33 . 5 . 0 

1976 9 14 6 43 51 . 6 29 . 81 89 . 57 75 . 5 . 4 

1977 6 5 19 21 37 . 4 26 . 07 88 . 43 0 . 4 . 7 

1978 10 14 18 48 48 . 9 27 . 66 87 . 33 0 . 4 . 8 

1978 10 23 14 36 50 . 4 28 . 56 86 . 78 33 . 4 . 4 

1979 4 2 1 16 46 . 5 26 . 46 90 . 68 33 . 4 . 4 

1979 4 11 16 8 12 . 6 25 . 98 88 . 84 33 . 4 . 7 

1979 6 19 16 29 8 . 4 26 . 74 87 . 48 1 . 5 . 2 

6

1979 10 17 1 44 22 . 2 27 . 97 87 . 62 33 . 4 . 6 

1979 11 16 19 17 27 . 4 27 . 95 88 . 69 39 . 4 . 6 

1980 6 11 5 25 15 . 4 25 . 79 90 . 31 68 . 4 . 9 

1980 11 19 19 0 44 . 5 27 . 40 88 . 80 1 . 6. 0 

1980 12 22 4 36 8 . 0 26 . 67 89 . 59 33 . 4 . 4 

1980 12 26 5 19 44 . 9 29 . 08 88 . 88 66 . 4 . 5 

1981 2 9 15 49 21 . 6 27 . 20 89 . 76 16 . 4 . 9 

1981 11 21 4 25 5 . 6 29 . 52 89 . 12 50 . 4 . 8 

1982 1 28 7 18 7 . 6 25 . 47 90 . 89 33 . 4 . 4 

1982 2 26 0 5 47 . 5 25 . 79 90 . 62 48 . 4 . 6 

1982 4 5 2 19 41 . 1 27 . 38 88 . 84 9 . 5 . 0 

1982 6 20 15 29 19 . 8 26 . 24 89 . 97 33 . 4 . 5 

1982 7 6 6 13 32 . 0 25 . 88 90 . 31 8 . 5 . 0 

1982 8 18 18 1 7 . 6 27 . 04 89 . 26 51 . 4 . 6 

1983 10 16 22 3 14 . 5 29 . 51 90 . 31 33 . 4 . 5 

1983 12 16 15 15 40 . 1 28 . 37 86 . 65 116 . 4 . 2 

1983 12 23 19 35 44 . 2 25 . 87 87 . 91 33 . 4 . 3 

1984 1 25 23 49 44 . 6 27 . 49 86 . 10 11 . 4 . 6 

1985 5 25 0 28 18 . 7 27 . 60 88 . 48 33 . 4 . 6 

1985 6 7 18 23 59 . 0 26 . 87 90 . 21 33 . 4 . 8 

1985 6 17 21 52 49 . 0 25 . 65 90 . 20 22 . 4 . 6 

1985 10 2 16 33 50 . 3 27 . 19 89 . 73 45 . 4 . 4 

1986 1 7 20 20 . 4 27 . 40 88 . 43 41 . 4 . 7 

1986 1 10 3 46 30 . 9 28 . 65 86 . 56 63 . 5 . 5 

1986 2 2 0 13 50 . 7 27 . 92 86 . 45 33 . 4 . 5 

1986 2 10 12 56 23 . 0 28 . 15 87 . 86 87 . 4 . 7 

1986 4 12 12 44 2 . 2 28 . 63 86 . 57 33 . 4 . 8 

1986 10 25 21 25 30 . 4 26 . 12 88 . 26 33 . . 0 

1986 12 1 19 14 29 . 0 28 . 30 87 . 80 10 . . 0 

1987 4 23 9 5 56 . 8 27 . 93 87 . 01 48 . 4 . 7 

1987 4 25 22 13 47 . 0 25 . 30 88 . 46 10 . . 0 

1987 5 10 5 10 42 . 3 28 . 99 87 . 26 33 . 4 . 5 

1987 6 22 23 6 53 . 5 28 . 40 87 . 17 33 . 4 . 1 

1987 9 25 23 16 29 . 0 29 . 84 90 . 37 19 . 5 . 1 

1987 9 26 1 3 3 . 0 29 . 82 90 . 45 33 . 4 . 4 

1987 9 29 17 30 28 . 3 29 . 91 90 . 41 33 . 4 . 6 

1987 9 29 21 12 30 . 0 29 . 70 90 . 41 46 . 4 . 5 

1987 10 6 22 18 17 . 2 29 . 90 90 . 42 10 . 4 . 7 

1987 10 22 21 23 56 . 0 27 . 07 89 . 06 19 . 4 . 2 

1987 11 25 19 20 40 . 0 27 . 70 86 . 17 33 . 4 . 5 

1987 12 6 23 29 44 . 0 27 . 00 88 . 52 42 . . 0 

1987 12 11 6 39 40 . 0 26 . 04 90 . 92 57 . 4 . 6 

1987 12 12 5 49 . 0 29 . 80 90 . 40 45 . 4 . 8 

1988 1 10 6 18 35 . 0 29 . 75 90 . 29 50 . 4 . 7 

1988 1 10 6 31 42 . 7 29 . 89 90 . 44 10 . 4 . 7 

1988 1 19 11 23 51 . 0 27 . 80 88 . 80 33 . 4 . 3 

1988 3 27 5 56 30 . 0 27 . 10 88 . 42 70 . 4 . 1 

1988 4 9 12 57 55 . 7 29 . 84 86 . 87 33 . 4 . 4 

1988 4 20 6 40 25 . 8 27 . 02 86 . 72 55 . 5 . 4 

1988 4 25 16 4 3 . 7 26 . 90 86 . 54 79 . 4 . 7 

7

1988 5 10 7 16 16 . 1 25 . 32 90 . 88 33 . 4 . 4 

1988 5 26 16 30 5 . 5 27 . 45 88 . 61 42 . 4 . 7 

1988 5 28 23 13 12 . 0 28 . 00 89 . 70 33 . . 0 

1988 8 20 23 9 10 . 1 26 . 72 86 . 63 65 . 6 . 4 

1988 8 20 23 38 56 . 0 26 . 90 86 . 70 38 . . 0 

1988 8 22 11 34 34 . 7 26 . 61 86 . 74 33 . 4 . 3 

1988 8 24 9 55 34 . 3 26 . 77 86 . 44 41 . 4 . 7 

1988 8 29 12 12 17 . 0 26 . 39 87 . 50 33 . 4 . 5 

1988 9 1 22 4 11 . 3 26 . 80 86 . 53 33 . 4 . 5 

1988 9 2 6 35 34 . 3 26 . 56 86 . 48 33 . 4 . 3 

1988 9 27 19 10 10 . 0 27 . 19 88 . 37 28 . 5 . 0 

1988 12 10 15 24 31 . 4 26 . 38 86 . 68 33 . . 0 

1988 12 13 6 29 17 . 3 27 . 14 87 . 97 52 . 4 . 4 

1988 12 24 13 32 22 . 0 26 . 90 88 . 00 41 . 4 . 4 

1988 12 27 2 56 1 . 8 27 . 98 87 . 86 38 . 4 . 6 

1989 2 12 23 44 57 . 0 30 . 00 89 . 86 53 . . 0 

1989 4 9 2 31 36 . 3 29 . 11 90 . 02 10 . 5 . 1 

1989 4 16 0 2 33 . 0 29 . 20 89 . 70 33 . . 0 

1989 5 10 23 20 34 . 0 27 . 70 87 . 20 33 . . 0 

1989 5 22 19 24 31 . 0 27 . 38 87 . 86 4 . 5 .0 

1989 6 11 13 42 45 . 7 26 . 39 90 . 70 50 . 4 . 5 

1989 7 30 21 4 44 . 0 30 . 00 90 . 50 33 . . 0 

1989 10 10 4 10 56 . 0 28 . 36 87 . 49 38 . 4 . 7 

1989 11 19 22 11 34 . 0 29 . 00 89 . 70 33 . 4 . 4 

1990 1 9 2 29 21 . 8 28 . 15 88 . 11 35 . 5 . 7 

1990 1 10 23 1 21 . 7 26 . 52 86 . 67 66 . 4 . 4 

1990 2 18 18 12 48 . 3 29 . 39 89 . 95 10 . 4 . 5 

1990 2 22 13 33 16 . 6 29 . 14 90 . 02 54 . 4 . 9 

1990 2 23 14 25 19 . 3 29 . 38 90 . 02 10 . 4 . 3 

1990 3 1 18 47 28 . 0 28 . 70 88 . 40 33 . 4 . 2 

1990 5 6 10 30 9 . 0 29 . 99 89 . 98 33 . 4 . 2 

1990 5 19 2 18 57 . 0 25 . 40 90 . 93 33 . . 0 

1990 7 13 11 50 11 . 0 28 . 20 86 . 90 33 . 4 . 5 

1990 10 29 12 6 28 . 0 27 . 60 89 . 10 33 . . 0 

1991 1 5 14 50 8 . 0 28 . 90 87 . 92 33 . . 0 

1991 3 4 0 55 38 . 0 28 . 10 89 . 20 33 . . 0 

1991 3 15 4 28 18 . 2 28 . 34 87 . 55 64 . 4 . 7 

1991 6 8 18 59 57 . 8 26 . 30 90 . 37 33 . 4 . 0 

1991 8 7 11 36 29 . 1 25 . 27 88 . 66 10 . 4 . 7 

1991 8 19 22 28 41 . 0 26 . 80 90 . 70 10 . . 0 

1991 9 25 19 26 49 . 3 26 . 70 88 . 40 33 . . 0 

1991 9 27 11 56 40 . 8 29 . 90 90 . 40 33 . . 0 

1991 10 30 13 13 57 . 0 26 . 00 88 . 60 33 . . 0 

1991 12 21 19 52 45 . 1 27 . 79 87 . 96 65 . 4 . 7 

1992 3 7 22 41 50 . 8 29 . 40 89 . 40 113 . 4 . 3 

1992 4 1 13 41 3 . 9 27 . 40 87 . 10 33 . 4 . 3 

1992 4 4 17 43 20 . 7 28 . 10 88 . 00 33 . 4 . 9 

1992 4 20 19 22 59 . 7 25 . 80 90 . 60 55 . 4 . 2 

1992 7 24 6 24 17 . 6 29 . 30 90 . 20 33 . 4 . 8 

1992 7 30 8 24 46 . 6 29 .60 90 . 20 14 . 5 . 9 

8

1992 7 30 9 7 39 . 1 29 . 90 90 . 30 33 . 4 . 2 

1992 7 30 13 36 42 . 0 29 . 80 90 . 30 33 . 4 . 4 

1992 7 30 17 28 53 . 9 30 . 00 90 . 40 33 . 4 . 5 

1992 7 30 19 6 13 . 3 29 . 80 90 . 20 33 . 4 . 3 

1992 8 4 22 50 3 . 0 29 . 90 90 . 40 10 . 4 . 2 

1992 8 8 19 50 42 . 6 29 . 90 90 . 30 33 . 4 . 3 

1992 8 9 22 34 46 . 4 28 . 70 86 . 50 37 . 4 . 3 

1993 2 15 14 29 40 . 8 25 . 90 87 . 50 30 . 5 . 0 

1993 3 3 5 17 31 . 0 25 . 40 90 . 20 33 . 4 . 5 

1993 3 20 14 51 59 . 7 29 . 10 87 . 30 12 . 5 . 8 

1993 3 20 21 26 39 . 4 29 . 00 87 . 40 21 . 5 . 0 

1993 3 31 13 44 10 . 1 29 . 10 87 . 30 20 . 5 . 1 

1993 7 3 2 0 22 . 2 28 . 30 86 . 60 33 . 4 . 7 

1993 7 9 16 23 17 . 3 26 . 80 86 . 00 33 . 4 . 6 

1993 9 5 6 5 54 . 6 27 . 20 87 . 30 33 . 4 . 5 

1993 12 14 2 27 44 . 4 28 . 40 86 . 80 33 . 4 . 8 

1993 12 14 2 27 44 . 4 28 . 40 86 . 80 33 . 4 . 8 

1994 1 16 14 22 38 . 3 26 . 40 89 . 10 33 . 3 . 9 

1994 4 15 14 28 48 . 7 25 . 90 90 . 50 33 . 4 . 2 

1994 5 25 7 38 53 . 7 26 . 60 87 . 80 48 . 4 . 6 

1995 1 1 19 36 13 . 6 27 . 80 87 . 60 33 . 4 . 9 

1995 1 12 23 39 51 . 0 29 . 40 88 . 20 33 . 4 . 9 

1995 8 8 16 52 48 . 8 26 . 40 90 . 40 33 . 4 . 4 

1995 12 6 0 50 33 . 0 25 . 20 91 . 00 33 . 4 . 5 

1995 12 11 9 49 36 . 0 27 . 60 87 . 50 33 . 4 . 0 

1996 1 25 7 15 19 . 3 28 . 00 87 . 00 33 . 5 . 2 

1996 1 25 7 15 13 . 0 28 . 40 86 . 90 33 . 4 . 4 

1996 3 23 16 7 34 . 2 27 . 20 88 . 30 33 . 4 . 0 

1996 4 26 16 31 3 . 0 27 . 80 87 . 60 33 . 5 . 2 

1996 5 10 9 7 1 . 8 30 . 00 88 . 10 0 . 4 . 8 

1996 5 11 3 58 50 . 2 29 . 90 88 . 10 0 . 4 . 8 

1996 5 11 7 27 11 . 2 29 . 90 88 . 10 0 . 4 . 3 

1996 5 14 5 41 8 . 9 29 . 70 87 . 90 0 . 4 . 1 

1996 7 3 7 0 28 . 9 29 . 90 88 . 10 0 . 4 . 1 

1996 7 3 10 10 33 . 8 29 . 90 88 . 20 0 . 5 . 0 

1996 7 3 10 19 42 . 9 30 .00 88 . 20 0 . 4 . 3 

1996 7 3 10 49 50 . 5 29 . 90 87 . 80 0 . 4 . 1 

1996 7 4 18 11 4 . 6 30 . 00 88 . 10 0 . 4 . 9 

1996 7 6 8 12 39 . 4 29 . 90 87 . 90 0 . 3 . 8 

1996 7 13 8 29 4 . 0 29 . 90 88 . 10 0 . 4 . 3 

1996 7 22 15 54 7 . 0 30 . 00 88 . 00 0 . 4 . 5 

1996 8 3 7 12 6 . 0 30 . 00 88 . 20 0 . 4 . 1 

1996 8 18 2 48 . 0 25 . 80 90 . 10 0 . 4 . 4 

1996 9 13 3 41 8 . 6 27 . 00 88 . 20 33 . 4 . 5 

1996 9 25 17 41 17 . 2 27 . 40 88 . 50 33 . 5 . 0 

1996 10 3 1 29 3 . 1 28 . 20 87 . 50 33 . 4 . 5 

1996 10 14 14 49 12 . 7 29 . 90 88 . 20 33 . 4 . 4 

1996 12 30 11 8 18 . 9 27 . 43 86 . 63 37 . 5 . 0 

1996 12 30 15 16 29 . 5 27 . 23 86 . 50 33 . 3 . 6 

1997 1 22 11 12 4 . 4 25 . 60 90 . 30 33 . . 0 

9

1997 1 25 20 8 28 . 7 30 . 00 88 . 00 33 . 4 . 4 

1997 3 3 9 29 40 . 0 27 . 24 86 . 00 45 . 4 . 7 

1997 3 22 21 16 4 . 8 29 . 89 88 . 15 33 . 4 . 4 

1997 4 4 10 8 41 . 0 25 . 50 90 . 80 33 . 3 . 8 

1997 4 7 13 0 42 . 0 27 . 40 86 . 50 33 . 4 . 4 

1997 5 26 0 45 32 . 1 27 . 70 86 . 90 33 . . 0 

1997 7 5 6 22 53 . 5 28 . 80 86 . 86 33 . 4 . 8 

1997 7 8 21 16 49 . 8 29 . 83 88 . 31 33 . 3 . 7 

1997 7 9 7 18 52 . 9 29 . 90 88 . 40 33 . 4 . 1 

1997 7 12 23 41 9 . 7 29 . 90 88 . 40 33 . . 0 

1997 8 10 11 53 17 . 2 29 . 16 89 . 49 33 . 3 . 4 

1997 8 17 20 3 32 . 8 28 . 13 87 . 56 33 . . 0 

1997 9 18 7 37 10 . 0 28 . 87 86 . 15 33 . 4 . 6 

1997 10 11 10 11 10 . 3 27 . 70 86 . 40 33 . 4 . 3 

1997 10 12 19 45 25 . 8 30 . 00 88 . 00 33 . . 0 

1997 10 30 2 2 52 . 0 29 . 50 89 . 70 33 . 5 . 3 

1997 10 30 20 3 . 0 29 . 20 89 . 40 0. 4 . 9 

1997 11 14 12 30 23 . 9 25 . 30 87 . 70 33 . . 0 

1997 11 27 16 11 57 . 0 27 . 60 87 . 34 33 . 5 . 1 

1997 11 27 16 55 52 . 1 27 . 70 87 . 76 33 . 4 . 2 

1997 12 8 2 3 55 . 8 27 . 48 87 . 17 33 . 5 . 0 

1997 12 8 6 37 57 . 8 27 . 48 87 . 16 33 . . 0 

1998 1 16 18 6 42 . 5 30 . 00 86 . 00 33 . 4 . 0 

1998 2 1 17 32 48 . 2 28 . 10 87 . 10 33 . 4 . 5 

1998 2 12 2 40 29 . 1 26 . 50 88 . 10 33 . 4 . 6 

1998 2 28 4 59 30 . 7 27 . 00 87 . 50 33 . 4 . 4 

1998 3 15 20 35 29 . 3 28 . 55 86 . 88 33 . 4 . 4 

1998 3 16 10 35 2 . 0 26 . 90 89 . 68 33 . 3 . 8 

1998 3 18 18 12 18 . 9 27 . 36 88 . 33 33 . 4 . 0 

1998 5 13 1 24 55 . 6 28 . 18 89 . 80 10 . 4 . 9 

1998 7 31 17 50 18 . 3 28 . 01 87 . 73 33 . 4 . 1 

1998 8 18 4 10 20 . 6 27 . 55 90 . 98 22 . 5 . 2 

1998 8 24 7 32 21 . 5 30 . 00 87 . 92 33 . . 0 

1998 8 25 9 43 6 . 0 29 . 99 88 . 09 33 . 4 . 1 

1998 8 25 9 56 44 . 0 29 . 83 87 . 91 33 . 4 . 4 

1998 8 25 10 25 6 . 0 29 . 98 88 . 10 33 . 4 . 4 

1998 8 25 12 43 4 . 3 29 . 96 88 . 09 33 . 4 . 4 

1998 8 25 13 39 49 . 5 29 . 92 88 . 12 33 . 3 . 8 

1998 8 25 15 16 2 . 7 29 . 97 88 . 10 33 . 4 . 4 

1998 8 30 3 49 48 . 1 29 . 90 87 . 98 33 . 4 . 0 

1998 9 3 18 15 56 . 5 27 . 85 86 . 94 33 . 5 . 6 

1998 9 3 18 22 19 . 2 27 . 97 87 . 04 33 . . 0 

1998 9 3 18 51 38 . 6 27 . 65 86 . 80 33 . 4 . 4 

1998 9 3 21 0 53 . 5 27 . 72 86 . 88 33 . 4 . 1 

1998 9 3 23 2 28 . 3 27 . 60 86 . 73 33 . 4 . 6 

1998 9 4 0 36 17 . 9 27 . 45 86 . 46 33 . 4 . 1 

1998 9 4 1 10 18 . 4 27 . 77 86 . 79 33 . 4 . 2 

1998 9 4 21 16 13 . 7 27 . 65 86 . 72 33 . . 0 

1998 9 6 21 35 49 . 4 27 . 86 86 . 89 33 . 4 . 6 

1998 9 10 22 57 16 . 9 27 . 20 88 . 34 33 . 4 . 7 

10

1998 9 12 5 8 52 . 1 27 . 85 86 . 90 33 . 4 . 2 

1998 9 21 23 24 40 . 6 29 . 94 88 . 00 33 . 4 . 1 

1998 9 26 20 48 44 . 1 27 . 52 86 . 13 33 . 3 . 9 

1998 9 30 2 29 55 . 1 29 . 94 88 . 11 33 . 5 . 1 

1998 10 11 22 0 49 . 9 26 . 35 86 . 40 90 . 4 . 4 

1998 10 13 14 47 51 . 9 29 . 74 87 . 88 33 . . 0 

1998 10 16 14 17 16 . 7 30 . 00 88 . 19 33 . . 0 

1998 11 26 10 14 27 . 6 27 . 75 87 . 89 73 . 5 . 1 

1998 12 1 5 35 9 . 2 27 . 93 87 . 64 33 . 4 . 8 

1999 1 28 16 10 33 . 9 28 . 22 87 . 31 41 . 4 . 0 

1999 3 25 5 4 54 . 3 28 . 51 88 . 28 33 . 3 . 8 

1999 3 25 20 47 57 . 4 28 . 50 87 . 63 13 . 4 . 2 

1999 3 31 22 32 57 . 8 28 . 57 86 . 81 21 . . 0 

1999 4 10 20 42 39 . 7 28 . 04 87 . 85 33 . 4 . 2 

1999 5 7 17 53 52 . 3 27 . 22 90 . 64 33 . . 0 

1999 5 9 8 8 57 . 7 27 . 40 89 . 45 15 . . 0 

1999 6 13 7 38 6 . 4 28 . 14 86 . 64 33 . 4 . 4 

1999 7 4 6 5 15 . 2 25 . 42 90 . 28 33 . 3 . 8 

1999 8 1 8 24 51 . 2 28 . 37 86 . 79 40 . 5. 0 

1999 9 5 2 28 22 . 8 28 . 07 87 . 53 33 . 4 . 5 

1999 9 8 18 8 27 . 9 27 . 90 87 . 91 19 . 3 . 7 

1999 9 16 12 20 9 . 8 27 . 55 87 . 71 33 . . 0 

1999 9 20 7 28 5 . 6 27 . 24 87 . 98 23 . 4 . 1 

1999 9 21 13 54 39 . 8 25 . 16 88 . 86 2 . 3 . 9 

1999 10 15 7 33 1 . 0 29 . 61 90 . 06 33 . 4 . 4 

1999 10 18 16 12 55 . 7 26 . 68 87 . 22 33 . . 0 

1999 11 5 15 57 21 . 4 28 . 59 87 . 08 23 . 3 . 7 

1999 11 17 5 27 14 . 0 28 . 09 89 . 18 33 . 3 . 6 

1999 1 28 16 10 33 . 9 28 . 22 87 . 31 41 . 4 . 0 

1999 3 25 5 4 54 . 3 28 . 51 88 . 28 33 . 3 . 8 

1999 3 25 20 47 57 . 4 28 . 50 87 . 63 12 . 4 . 2 

1999 4 10 20 42 39 . 7 28 . 04 87 . 85 33 . 4 . 2 

1999 6 13 7 38 6 . 4 28 . 14 86 . 64 33 . 4 . 4 

1999 7 4 6 5 15 . 2 25 . 42 90 . 28 33 . 3 . 8 

1999 8 1 8 24 51 . 2 28 . 37 86 . 79 40 . 5 . 0 

1999 9 5 2 28 22 . 8 28 . 07 87 . 53 33 . 4 . 5 

1999 9 8 18 8 27 . 9 27 . 90 87 . 91 19 . 3 . 7 

1999 9 20 7 28 5 . 6 27 . 24 87 . 98 22 . 4 . 2 

1999 9 21 13 54 39 . 8 25 . 16 88 . 86 2 . 3 . 9 

1999 10 15 7 33 1 . 0 29 . 61 90 . 06 33 . 4 . 4 

1999 11 5 15 57 21 . 4 28 . 59 87 . 08 23 . 3 . 7 

1999 11 7 5 11 57 . 6 27 . 10 89 . 13 14 . 3 . 8 

1999 11 17 5 27 13 . 8 28 . 04 89 . 22 33 . 3 . 3 

2000 1 20 12 54 27 . 5 27 . 78 86 . 02 33 . 5 . 0 

2000 1 25 12 7 33 . 3 29 . 94 89 . 72 0 . 5 . 0 

2000 2 21 18 21 43 . 2 28 . 36 86 . 56 33 . 4 . 7 

2000 3 13 20 44 38 . 3 27 . 43 87 . 85 108 . 4 . 1 

2000 4 18 7 53 45 . 2 26 . 55 90 . 26 33 . 3 . 3 

2000 6 20 7 16 43 . 8 26 . 04 90 . 31 33 . 4 . 3 

2000 9 6 7 19 8 . 9 28 . 52 86 . 86 33 . 4 . 2 

11

2000 10 3 17 8 22 . 4 26 . 88 89 . 8 33 . 2 . 8 

2001 1 16 8 6 57 . 4 26 . 42 90 . 24 33 . . 0 

2001 2 9 10 20 55 . 7 27 . 24 89 . 67 13 . 3 . 9 

2001 2 27 1 46 7 . 0 26 . 48 90 . 55 20 . 4 . 7 

2001 2 27 16 21 25 . 6 28 . 38 86 . 97 33 . 4 . 9 

2001 4 3 23 8 38 . 0 27 . 74 86 . 13 33 . 4 . 6 

2001 4 3 23 26 4 . 4 27 . 82 86 . 18 18 . 3 . 5 

2001 4 8 18 35 49 . 3 28 . 16 88 . 57 20 . 3 . 9 

2001 4 20 18 35 2 . 7 26 . 13 90 . 67 33 . 4 . 6 

2001 4 28 10 37 59 . 1 28 . 55 87 . 14 33 . 5 . 0 

2001 4 29 10 39 9 . 1 28 . 70 87 . 14 33 . 4 . 5 

2001 5 3 16 2 59 . 6 27 . 63 90 . 47 33 . 3 . 8 

2001 5 21 21 55 7 . 8 28 . 54 86 . 72 33 . 3 . 8 

2001 6 12 10 47 46 . 6 28 . 46 86 . 57 20 . 3 . 9 

2001 7 3 19 16 18 . 4 26 . 15 89 . 20 6 . 3 . 6 

2001 7 6 23 4 3 . 4 27 . 65 88 . 64 10 . 2 . 7 

2001 8 6 6 23 32 . 7 27 . 47 87 . 47 9 . 4 . 3 

2001 9 4 22 8 3 . 7 25 . 37 90 . 96 15 . 3 . 7 

2001 9 27 22 40 11 . 1 26 . 99 87 . 76 2 . 4 . 1 

2001 12 2 22 41 14 . 8 27 . 18 88 . 33 15 . 4 . 8 

NO. OF EARTHQUAKES = 358 

12

PRELIMINARY RANKING STUDY REPORT- BY CEA 

Ringpi Hydro Electric Scheme (Org. No. HEPR-PS-BHM-784) 

Annexure 6.1 

The Ringpi Chhu is one of the sub-tributaries of Talung Chhu and intercepts as substantial 

catchment area. It if formed by two streams originating at high elevations having snow 

catchment in their upper reaches. The river has substantial flows and has steep gradient. A 

scheme can be developed involving construction of a diversion structure immediately 

downstream of confluence of the two at a site where the river bed level is +2950 m., a 

tunnel about 7 Km. in length and a power house with a tailrace level of + 1800 m. The 

scheme would utilize a gross head of 1150 m. enabling a firm power output of about 20 

MW. With an optimum generating capacity of 160 MW, the scheme would enable annual 

energy generation of 716 GWH and 780 GWH respectively in 90% and 50% dependable 

years.

1 

Annexure 6.2 

SUMMARY RECORD OF DISCUSSION OF MEETING TAKEN BY 

CHIEF ENGINEER (HP&I), CEA WITH NHPC OFFICERS ON 

18.12.2003 REGARDING PFRS OF RINGPI HE PROJECT IN SIKKIM 

(Letter No. 7/9/NHPC/2003/HP&I/1572 dated 22.12.03) 

Conceptual planning of Ringpi hydroelectric project in Sikkim was discussed 

with officers of NHPC on 18.12.2003. Subsquently necessary 

information/drawing were submitted on 19.12.2003. As per reassessment 

studies carried out in CEA (based on desk studies) Ringpi HE Project envisaged 

construction of a diversion structure, 7 km. long head race tunnel and a power 

house with installed capacity of 160 MW. The river bed level at diversion site 

was +2950 m. and tail water level was +1800 m. NHPC officers indicated that 

there was some discrepancy in the level indicated in CEA studies of diversion 

structure. Actual river bed level at diversion site would +2940 m. NHPC has 

proposed the tail water level of the Ringpi scheme as +1850 m. which 

corresponds to FRL of proposed Lingza HE scheme for which PFR is being 

prepared. It was pointed out that in the proposed Ringpi HE scheme, due to high 

head available, pelton type of turbine would be installed. Accordingly, 

difference between tail water level of Ringpi HE project and FRL of Lingza HE 

project should be around +3 m. NHPC has been advised to proceed with the 

preparation of PFR of Ringpi HE scheme keeping in view the above suggestion. 

NHPC however, may discuss various alternatives considered by them in PFR.

TITLE 

ANNEXURES 6.3 

Summary of Discussions on Power Potential 

studies 



No. 

1-2 

Reply on CWC’s Comments on Hydrology 3-6 

Reply on Comments of SP&PA Division CEA 7-8 

Reply on comments on CMDD(E&NE), CWC 9

1 

Annexure 6.3 

SUMMARY RECORD OF DISCUSSIONS OF MEETING TAKEN BY 

DIRECTOR (HP&I), CEA WITH NHPC ON 24.12.2003 REGARDING 

POWER POTENTIAL STUDIES OF PFRS OF RINGPI & 

RANGYONG HE PROJECTS IN SIKKIM. 

(Letter No. 7/9/2003/HP&I/1581-1582 dated 24.12.2003) 

Power potential studies of Ringpi & Rangyong H.E. Projects in Sikkim were 

discussed in detail and summarized as under : 

1 Ringpi HE Project : 

i. Only power potential studies without any write up was presented by 

NHPC officers and the same was discussed. 

ii. Hydrology may be got cleared by CWC. 

iii. NHPC have furnished studies considering FRL at +2940 m. and tail 

water level of +1853 m. (+3 m. above the FRL of proposed Lingza HE 

Project). NHPC Officers indicated that sufficient pondage is 

available for peaking operation. NHPC was advised to furnish basis of 

FRL, MDDL and tail water level in the concerned chapter of PFR. 

iv. Based on the studies presented by NHPC an installed capacity of 70 

MW was considered to be in order subject to approval of 

hydrology by CWC. It was suggested that two units of 35 MW each 

could be installed in case there is no problem of transportation. 

v. NHPC may prepare summary of the studies indicating yearly inflow, 

annual energy generation, load factor of operation during monsoon and 

lean flow period. 

vi. NHPC may indicate recommendation for further studies at the time of 

FR/DPR. 

2. Rangyong HE Project : 

i. Only power potential studies without any write up was presented by 

NHPC officers and the same was discussed. 

ii. Hydrology may be got cleared by CWC.

iii. NHPC was advised to keep the tail water level of the project about 3 m. 

above FRL of the downstream project. NHPC Officers indicated that 

sufficient pondage is available for peaking operation. NHPC was 

advised to furnish basis of FRL, MDDL and tail water level in the 

concerned chapter of PFR. 

iv. NHPC has proposed an installation of 150 MW. The power potential 

studies presented by NHPC are generally in order subject to 

compliance of the above comment and approval of hydrology by 

CWC. 

v. NHPC may prepare summary of the studies indicating yearly inflow, 

annual energy generation, load factor of operation during monsoon and 

lean flow period. 

vi. NHPC may indicate recommendation for further studies at the time of 

FR/DPR. 

2

REPLY ON CWC’s COMMENTS ON HYDROLOGY OF 

RINGPI HE PROJECT 

In reference to letter no. 7/9/(NHPC)/2003/HPI/1500 dt. 20-1-2004, point wise reply to the 

CWC observations are placed as below: 

Data 

availability 

Consistency of 

data 

Water 

availability 

studies 

CWC Observations Reply of NHPC 

Rainfall - The report has quoted the 

paper of Sh. Biswas and Bhadram in 

which data of 42 raingauge stations, 24 

of which is equipped with SRRG have 

been stated to be available. However 

rainfall data has not been furnished in 

the report and only the period of data 

availability of 11 raingauge stations 

located u/s of the Teesta-V HEP is given 

in the report. 

(i) Though the rainfall data of 11 

raingauge stations available with NHPC 

could not be utilized in the study due to 

the reason that none of the stations are 

within the project catchment, the project 

authorities may put in their effort to verify 

whether any of the remaining stations as 

mentioned in the report lies in the project 

catchment and to explore the 

possibilities of utilization of the data in 

the study. 

(ii) A complete list of all rainfall and 

discharge stations of Teesta Basin may 

be furnished. 

(i) Only graphical presentation 

comparing the avg. 10-daily discharges 

of the four methodologies has been 

furnished in the report. The data and the 

3 

As explained in earlier meetings and 

correspondences, the paper of Biswas and 

Bhadram has been quoted in the report to 

explain the precipitation characteristics. At 

present, NHPC has rainfall data of only the 

11 raingauge stations whose data availability 

status is shown in the report. As desired, the 

annual rainfall at these 11 stations for the 

available period is enclosed as Annexure-I. 

(i) None of the raingauge stations out of the 

remaining 31 raingauges as mentioned in the 

report of C.V.V Bhadram are located in the 

sub-basin under consideration. 

(ii) The list of rainfall and discharge stations 

lying upto the catchment of Teesta-V has 

already been shown in the data availability 

status given in report. Rainfall and discharge 

stations lying in the entire Teesta basin are 

of not relevant for the present projects. 

The available average 10-daily series at 

Lachen has already been sent along with the 

replies of Rukel and Rangyong projects. 

Tolung Chu data has not been used as the

analysis of Lachen adopted for the 

project has not been furnished without 

which checking is not possible. In the 

absence of site-specific data, the use of 

Tolung Chu data would be more reliable. 

The snowfed area covers a major portion 

of the project catchment and without 

establishing hydro-meteorological 

similarity transfer of data from other sub- 

basin would be unjustified. Before 

discarding Tolung Chu data the project 

authorities are advised to verify whether 

any of the remaining 31 rain gauges are 

located in the sub-basin and to utilize the 

same after applying consistency checks 

and results incorporated. Rainfall-runoff 

factor based on Tolung Chu data may be 

evaluated before discarding the data. 

The results obtained may be compared 

with the series obtained from Lachen 

before recommending the yield series. 

Efforts may be made to collect site 

specific data and water availability 

studies may be reviewed based on 

observed data. 

(ii) The basis of deriving the catchment 

reduction factor is not given. 

(iii) A series of projects is being planned 

in Teesta Basin and Integrated studies 

on water availability need to be done 

4 

series obtained using this data was on a 

much higher side as compared to other three 

series and no consistency checks could be 

applied to check the reliability of the data. 

Hence for the time being Lachen G&D data 

has been used. 

It has been verified that none of the 

raingauge stations out of the remaining 31 

raingauges as mentioned in the report of 

C.V.V Bhadram are located in the sub-basin 

under consideration. 

(ii) The catchment reduction factor has been 

obtained on the basis of rainfed area at both 

the sites. Rainfed catchment of Lachen site 

is 574 Sq.km and of Ringpi is 63 Sq.km. 

Using these areas the catchment reduction 

factor comes out to be 0.11 and this factor 

has been used for converting the Lachen 

series to proposed dam site. The factor 0.22 

has been wrongly mentioned in the report 

and is a typing error. 

(iii) Cascade development need to be done 

at a later stage.

incorporating the likely releases from the 

u/s power house and independent 

catchment contributions. 

Design Flood (i) The design flood studies done by 

NHPC are too empirical to be relied upon 

even for PFR. The project authorities 

may also calculate the PMF value using 

SUH approach as suggested in North 

Brahmaputra Basin (Sub Zone-2(a) 

report published by CWC by obtaining 

the PMP/SPS value and temporal 

distribution of rainfall from IMD and 

following 2 bell per day approach and 

incorporate this value also in the 

comparative study to get a more realistic 

value. 

(ii) Short interval data may be collected 

and the design flood should be reviewed 

based on observed data. 

Sedimentation The sedimentation rate for the region is 

about 0.1765 Ham/Sq.km/year as per 

CWC studies published in the 

Compendium on Silting of Reservoirs In 

India which is higher than the rate 

proposed for the project. As stated in the 

report more detail study is required. Data 

may also be collected from the 

completed projects of the basin. 

As per the terms of preparation of PFRs 

and as emphasized in the meetings 

conducted by CEA sedimentation studies 

are required to be carried out and 

incorporated in the PFRs. 

General The PFR must bring out the limitations of 

the hydrological studies carried out for 

the PFR and suggest improvements, 

specific recommendations for opening 

5 

(i) As already explained in our earlier replies 

also, for such detailed studies as suggested 

for this stage i.e PFR, neither the database is 

at all sufficient nor necessity felt by us. 

During feasibility stage, deterministic/ 

probabilistic approach will be used, based on 

more observed data. 

(ii) It is not felt necessary to perform such 

detailed study during PFR stage. 

We are aware of the findings of CWC studies 

published in the Compendium on silting of 

reservoirs in India. As per that report, the 

sediment rate varies from 0.05658 to 0.2785 

Ham/Sq.km/year for Indus, Ganga and 

Brahmaputra basin. But the silt rate adopted 

for this particular project has been calculated 

on the basis of observed sediment data at 

Dikchu and is more region specific than that 

given in “Compendium on silting of reservoirs 

in India”. 

The necessity of detailed sedimentation 

study showing the new zero elevation, 

revised area capacity curve etc. is not felt 

during PFR stage. 

The PFR has pointed out the limitation of the 

studies after each study and establishment of 

G&D site, rainfall stations etc. are also 

highlighted in the PFR.

new hydrological stations, method of 

observations, data to be collected etc. 

may be given which will help us as 

guidance to the agency taking up the 

detail investigations/DPR must review 

the network in consultation with HSO, 

CWC. 

The hydrological studies for the PFR 

may be revised incorporating the above 

observations. 

6 

Moreover, all the CWC comments along with 

their replies are also being appended in the 

PFR’s for future reference.

REPLY ON COMMENTS OF SP&PA DIVISION ON DRAFT 

PFR OF RINGPI HE PROJECT 

(CEA Letter No.7/9/(NHPC)/2003/HP&I/111 dated 20.01.2004 ) 

Sr.No. Comments Reply 

6.1 

General 

6.2 

6.3 

Ringpi HEP is a run of the river typr 

hydro project situated in the Dzongu 

area of North district of Sikkim. The 

project envisages construction of 40m 

high concrete dam, a 7km long head 

race tunnel and an underground power 

house. 

Construction Power 

The construction power for the project 

shall be available through about 20km 

transmission line from Teesta-III,IV 

and V under construction project. 

Switchyard 

No details are given. 

6.4 Power Evacuation: 

Power will be generated at 11KV and 

stepped up to 220KV through 7no 

11/220KV 15MVA single phase 

transformers. The power generated 

from this project would be evacuated 

through 220KV double circuit line to 

a pooling station proposed near 

Teesta-II HEP to feed in to the grid 

which in turn is connected to national 

grid, which is in order. 

7 

It is general description of the 

project and no reply is required. 

This is already discussed in Chapter 

–X of the PFR 

5 nos. of bays have been taken at 

switchyard which have been 

indicated in the cost estimate based 

on the tentative scheme envisaged at 

this stage. However, 6 nos of bays 

have been envisaged in dimension of 

150 X 115m switchyard taking into 

account one future bay. Further 

details of switchyard are normally 

worked out during FR/DPR stage. 

No reply is required.

6.5 Cost: 

According to PFR 5 no of 220KV line 

bays has been taken: 

Generator bays -2 

220KV line bays – 2 

Bus Coupler bays – 1 

Which is in order. 

8 

No reply is required.

REPLY ON COMMENTS OF CMDD DIRECTORATE, CWC ON PFR OF RINPI 

HE PROJECT 

(Letter No CWC P.U. No. 20/2/03-CMDD(E&NE)/136 dated 26.2.2004) 

Comments of CEA/CWC 

1. As per cl 6.2.1 the location of dam 

has been made keeping in view of 

the topography, geology and 

maximum water availability at the 

proposed site. But the favorable 

characteristics of topography and 

geological features, which led the 

selection of dam site, should be 

incorporated in PFR. 

2. It should be mentioned in the 

report that the PMF value has been 

vetted by hydrology (NE)Dte. 

CWC. 

3. The report should contain 

geophysical information about the 

project site. 

4. Though the drawing shows a ski 

jump type of energy dissipater, 

nothing has been written in the 

submitted PFR regarding the 

energy dissipation arrangements. 

9 

Replies of Design Division 

The study on alternative layouts and 

alternative locations has been included in 

further studies during FR/DPR stage 

when more information on topography, 

geology, construction material etc. shall 

be available. 

Hydrology adopted is as per decisions 

taken in progress review meeting with 

CEA. 

The dam site is located in remote area, 

where proper approach was not available, 

therefore the geo-physical survey could 

not be conducted. The power house area 

is having sufficient rock exposures, 

hence the geo-physical survey was not 

required at this stage. 

These details shall be worked out during 

FR/DPR stage.

Ringpi - Ministry of Power

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