GANGOTRI H.E. PROJECT 55 (1X55) MW - Ministry of Power

CHAPTERS 

GANGOTRI H.E. PROJECT 

55 (1X55) MW 

CONTENTS 

PFR STUDIES OF GANGOTRI HE PROJECT 

NAME Page No. 

Salient Features …………………………. i-iv 

I Executive Summary……………………… 1-1 to 1-5 

II Background Information…………………. 2-1 to 2-6 

III The Project Area…………………………. 3-1 to 3-3 

IV Topography and Geotechnical Aspects…… 4-1 to 4-9 

V Hydrology………………………………… 5-1 to 5-7 

VI Conceptual Layout and Planning…………. 6-1 to 6-12 

VII Power Potential Studies…………………… 7-1 to 7-4 

VIII Power Evacuation …………………………. 8-1 to 8-2 

IX Initial Environment Studies………………… 9-1 to 9-20 

X Infrastructure Facilities…………………….. 10-1 to 10-4 

XI Construction Planning & Schedule………… 11-1 to 11-5 

XII Cost Estimate………………………………. 12-1 to 12-2 

XIII Economic Evaluation……………………… 13-1 to 13-3 

1

APPENDICES 

1.1 

Observation of CWC on Hydrological 

Studies 

1.2 Replies on Observations 

1.3 Compliance of Hydrological Studies 

2.0 Drawings 

PFR STUDIES OF GANGOTRI HE PROJECT 

2

LOCATION 

GANGOTRI HE PROJECT (1x55=55 MW) 

SALIENT FEATURES 

PFR STUDIES OF GANGOTRI H.E. PROJECT 

State Uttaranchal 

District Uttarkashi 

River Bhagirathi 

Dam site 

Location About 2.5km d/s of Gangotri Shrine. 

Latitude 30 o 59’ 54” N 

Longitude 78 o 55’ 03” E 

Nearest Airport Dehradun 

Nearest rail head Rishikesh/Dehradun 

HYDROLOGY 

Catchment area at dam site 944 sq. km 

Maximum average discharge at dam site 94.2 cumec 

Minimum average discharge at dam site 4.7 cumec 

RESERVOIR 

Full Reservoir Level (FRL) El 2989.0 m 

Minimum Drawdown Level (MDDL) El 2984.0 m 

Gross storage at FRL 4.370 M cum 

Live storage 0.91 M cum 

Area under submergence at FRL 24.96 ha 

DIVERSION TUNNEL 

Number 1 

Size 4 m dia 

Length 400 m 

Diversion discharge (assumed) 50 cumecs 

i

DAM 

Type Concrete gravity 

Top elevation of dam El 2991.0m 

Height of dam above 

river bed level 26.0 m 

Length of dam at top 110.0 m 

River bed level El 2965.0 

SPILLWAY 

Design flood 2500 cumecs 

Type Ogee 

Crest elevation El 2975.0 

Number & Size 3 of 12.5 m x 14.0 m 

Length of spillway 49.5 m 

Energy dissipation Stilling basin 

INTAKE 

Size 2.75 m ф D-shaped 

Invert level El 2977.0 m 

Number 1 

Size of gate opening 3.0 m x 3.0 m 

Design discharge 21.83 Cumecs 

DESILTING CHAMBER 


Number 1 no 

Size 110.0 m x 8.0 m x 9.0 m 

Design discharge 21.83 cumecs 

Particle size to be removed 0.2 mm & above 

ii

HEAD RACE TUNNEL 

Number 1 

Size 2.5 m 

Shape D-shaped 

Length 5.2 km 

Rated Discharge 18.19 Cumecs 

SURGE SHAFT 

Number 1 

Size 6.0 m dia 

Height 92.0 m 

PRESSURE SHAFT 

Numbers 1 No. 

Size 2.0 m 

Length 315.0 m 

POWER HOUSE 

Type Underground 

Installed capacity 55 MW 

Number of units 1 

Power house cavern size 40 mx20.5mx30m 

Type of turbine Vertical Francis 

C.L. of turbine El 2634.50 

Rated Head El 336.33 m 

TAIL RACE 

Size 3.0 m 

Type D-Shape 

Length 450.0 m 

Design Discharge 18.19 cumecs 

River Bed Level El 2638.0 m 

Normal TWL El 2642.0 m 


iii

SWITCHYARD 


Size Gas Insulated Switchyard (GIS) on 

the floor above the transformer/s in P/H 

cavern 

POWER GENERATION 

Installed capacity 55 MW 

Annual energy generation 

i) 90% dependable year 264.76 GWh 

ii) Energy in 90% year 256.64 GWh 

on 95% availability 

COST ESTIMATES & FINANCIAL ASPECT (Rs. Crores) 

Civil Works 148.46 

Electro Mechanical Works 63.18 

Sub Total 211.64 

Interest During Construction 33.47 

Total (Generation) 245.11 

Transmission works 7.50 

Grand Total 252.61 

Tariff for first year Rs 1.62 Rs./kWh 

Levellised Tariff Rs 1.42 Rs/kWh 

CONSTRUCTION PERIOD 5 years 

iv

1.1 INTRODUCTION 

CHAPTER - I 

EXECUTIVE SUMMARY 


The Gangotri Hydroelectric Project located in Uttarkashi district of 

Uttaranchal envisages utilization of the waters of the river Bhagirathi river for 

power generation on a run of river type development, harnessing a head of 

about 347 m. 

The project with a proposed installation of 1 x 55 MW ( 55 MW) would afford 

an annual energy generation of 264.76 GWh in a 90% dependable year. The 

tariff from the project at present day cost would be Rs.1.42 kWh (levellised). 

The diversion site is located at Latitude 30 o 59’ 54”, Longitude 78 o 55’ 03” E. 

The dam site is approachable from Rishikesh/Dehradun road (via Tehri- 

Uttarkashi-Gangotri highway) at a distance of 267 km upto Bhaironghati and 

further 9 km from Bhaironghati to diversion site. The nearest rail head is 

located at Rishikesh and Dehradun nearest airport is located at Dehradun. 

1.2 SCOPE OF WORKS 

The Gangotri HE project envisages construction of : 

• a 26 m high concrete gravity dam across river Bhagirathi to provide a 

live storage of 0.91 M cum with FRL at El 2989 m and MDDL at El 

2984 m. 

• 1 no desilting chamber of length 110.0 (L) and size 8.0 m (W) 9 .0 m 

(H) to remove silt particles of size 0.2 mm and above; 

1-1


• a 5.20 km long and 2.5 m dia head race tunnel terminating in a surge 

shaft 

• a 92.0 m high, 6.0 m dia surge shaft 

• 315 m long, 2.0 m dia pressure shaft 

• an underground power house having an installation of one Francis 

turbine driven generating unit of 55 MW operating under a rated 

head of 336.33 m; and 

• 450 m long tail race tunnel to carry the power houses release back to 

the river. 

1.3 HYDROLOGY 

The river Gangotri drains a catchment area of about 944 sq km at the 

proposed dam site. The water availability for the project i.e. the dependable 

flows both for 90% and 50% dependable year have been assessed, based on 

Regional model incorporating glacial cover, snow and forest cover and 

incorporating data of 17 Gauge Discharge sites (13 CWC sites and 4 state 

Govt. sites) in the region utilising the available data for the period 1975-76 to 

2001-2002 for many of the sites. The computed inflow series worked out has 

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

assessed as 2500 cumecs (SPF). 

1.4 POWER POTENTIAL STUDIES 

The available data of water flows on 10 daily basis has been analysed. Water 

flows determined on 90% dependable year, have been utilised for computing 

power benefits. An installation of 55 MW comprising 1 generating units of 55 

MW has been proposed. The energy availability from the project in a 90% 

dependable year has been summarized below : 

1-2

Annual Energy Generation 

Annual Energy Generation (GWh) : 264.76 

Annual Load Factor (%) : 54.95 

Generation during Lean Flow Season 

Energy Output (MWc) : 10.28 

Load Factor (%) : 18.69 


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

been worked out as 256.64 GWh. 

A pondage of 0.910 Mcum has been provided in the diversion dam which 

would enable the station to operate as peaking station. The pondage is 

equivalent to 764.215 MWh which is sufficient to operate the station for 13.89 

hours. 

1.5 POWER EVACUATION ASPECTS 

The 55 MW power generated at 11 kV at Gangotri HEP will be stepped upto 

220 kV by unit step-transformers. The power would be transmitted to nearby 

Bhaironghati HEP. 

1.6 ENVIRONMENTAL ASPECTS 

The project site is located on river Bhagirathi. The submergence area is 24.96 

ha, of which 14.90 ha of land falls under the category of reserve forest area 

1-3


About 1.89 ha of barren land is coming under reservoir submergence. In 

addition, land will also be required for other project appurtenances. Based on 

assessment of environmental impacts, management plans have to be 

formulated for acquisition of forest land, wildlife conservation, muck disposal, 

quarry stabilization, and other environmental issues. These issues would be 

addressed during the investigation for DPR. 

1.7 ESTIMATES OF THE COST 

The project is estimated to cost Rs. 245.11 Crores including IDC at June,2003 

price level. The preliminary cost estimate of the project has been prepared as 

per guidelines of CEA/CWC. The break up of the cost estimates is given 

below : 

Particulars Rs. (in Crores) 

Civil Works : 148.46 

Electro Mechanical Works : 63.18 

Sub Total : 211.64 

Interest During Construction : 33.47 

Total (Generation) : 245.11 

Transmission Works : 7.50 

Grand Total : 252.61 

1.8 FINANCIAL ASPECTS 

As indicated above, the Gangotri HE Project, with an estimated cost 

(Generation only) of Rs. 245.11 Crores (including IDC of Rs. 33.47 Crores) 

and design energy of 256.64 GWh in a 90% dependable year is proposed to 

1-4


be completed in a period of 5 years. The tariff has been worked out 

considering a debt-equity ratio of 70:30, 16% return on equity and annual 

interest rate on loan at 10%. The tariff for first year and levellised tariff (at 

power house bus bar) have been worked out as Rs.1.62 /kWh & Rs. 

1.42/kWh respectively. 

1.9 CONCLUSIONS 

Gangotri HE Project involves simple civil works and could be completed in 5 

years. The project would afford a design energy of 256.64 GWh in a 90% 

dependable year. The cost per MW installed works out to Rs. 3.85 Crores. 

The Preliminary Feasibility Report indicates that the scheme merits 

consideration for taking up Survey & Investigation and preparation of DPR. 

1-5

2.1 GENERAL 

CHAPTER – II 

BACKGROUND INFORMATION 


In Nov.2000, Uttaranchal State was carved out of thirteen hill districts of 

Northern U.P. The state borders with Nepal and Tibet on the east, Central 

Himalayas on the north, Haryana and Himachal Pradesh on the west and 

northwest respectively. 

Geophysically the state has four Mountain Zones namely Foot hills, Lesser 

Himalayas, Greater Himalayas and Trans-Himalayas. The mountains are 

covered with perpetual snow and glaciers and has gifted the north India a 

perennial river system of the Ganga and its tributaries. The tributaries of 

Ganga, namely Alaknanda, Bhagirathi, Yamuna and Sarda originate from 

the foothills of snow capped peaks and glaciers in the Central Himalayas and 

incise their respective courses through the rugged terrain, splash and surge 

the steep gradients and most of the streams offer excellent potential for 

Hydro power development. 

The region is blessed with magnificent glaciers, majestic rivers, gigantic snow 

capped peaks, Valley of flowers, natural beauty and rich flora and fauna. 

Many holy shrines have blessed the state spiritually and given the name of 

“Dev Bhoomi” or “Land of Gods”. The seasonal influx of tourists, the seekers 

of peace for visit to the holy shrines and lovers of nature contribute to the 

state income. 

The state is divided into Kumaon and Garhwal Divisions with 13 districts, 

42 tehsils, 95 blocks, and 15689 inhabited villages and 73 towns. The 

2-1


State has a geographical area of 53119 sq. km which is 1.62% of the total 

area of the country and supports 84.8 lakh population which is 0.83% of 

the total population of India. The percentage of villages having population 

more than 500 is about 11.4% (1991 Census). The existing majority of 

smaller settlements of Uttaranchal poses a serious challenge for the 

economic, infrastructure and lack of services to the far flung places in the 

hilly terrain makes Uttaranchal as one of the extremely backward states of 

India. 

It has 76.1% electrified villages as compared to 75.3% of villages of U.P. 

The average per capita consumption of electricity is 245.57 kWh whereas 

Dehradun and Nainital consume 480.81 and 447.33 kWh respectively 

with a minimum consumption of 43.7 kwh in Uttarkashi. 

2.2 POWER SCENARIO IN NORTHERN REGION 

2.2.1 Present Status 

Most of the states in the Northern Region have been experiencing energy 

shortage as well as shortage of Peak Power of varying degree. Actual Power 

supply position in the Northern Region during the year 2001-2002 has been 

as under: 

Energy (in MU), year 2001-2002 

State Require- Availability Shortage(-)/ %age 

ment 

Surplus (+) 

Chandigarh 1110 1108 (-) 2 0.2 

Delhi 19350 18741 (-)609 3.1 

Haryana 18138 17839 (-)299 1.6 

Himachal Pradesh 3293 3206 (+) 87 2.6 

Jammu & Kashmir 6635 5899 (-) 736 11.1 

2-2


State Require- Availability Shortage(-)/ %age 

ment 

Surplus (+) 

Punjab 28780 27577 (-)1203 4.2 

Rajasthan 24745 24495 (-)250 1.0 

Uttaranchal-U.P 48332 43545 (-)4787 9.9 

Northern Region 150383 142410 (-)7973 5.3 

2.2.2 Peak Power (in MW), year 2001-2002 

State Peak Peak Met Shortage(-)/ %age 

Demand 

Surplus (+) 

Chandigarh 180 180 0 0.0 

Delhi 3118 2879 (-)239 7.7 

Haryana 3000 2900 (-)100 1.6 

Himachal Pradesh 562 562 0 0.0 

Jammu & Kashmir 1209 999 (-) 210 17.4 

Punjab 5420 4936 (-)484 8.9 

Rajasthan 3700 3657 (-)43 1.2 

Uttaranchal-U.P 7584 6887 (-)607 9.2 

Northern Region 24773 23000 (-)1773 7.2 

2.3 NECESSITY OF HYDRO POWER DEVELOPMENT IN UTTARANCHAL 

2.3.1 Hydro and Thermal Power Mix 

The main resources for generating electricity are by utilising the hydro 

potential available along the river drops besides the use of fossil fuel. 

Presently the ratio of thermal generation and Hydro-electric generation in 

Uttaranchal Power grid, is quite disproportionate. With the diminishing coal 

resources and difficult oil position all over the world, it is necessary that 

electric generation be aimed to achieve the economic balance of 40:60 

2-3


between the hydro and thermal generation of power, as against the existing 

25:75 ratio. 

2.4 BRIDGING THE GAP OF HYDRO POWER GENERATION 

The requirement of power in Uttranchal is very fluctuating because of many 

seasonal and other similar demands of industries. To improve the share of 

hydro-power generation it is essential to develop the hydroelectric power 

potential of state which is about 15110 MW, of which so far only 8% has been 

developed. 

The existing installed generating capacity in the 

State is about 1286 MW ( 2003 fig) and the whole is contributed by hydro 

generation. There is no thermal power generation in the state . The major 

hydro power stations under construction in the state are (i) Maneri Bhali, 

Stage-II (304 MW), (ii) Lakhawar Vyasi, Stage-I (300 MW), (iii) Lakhwari 

Vyasi, Stage-II (120 MW), (iv) Srinagar H.E. Project (330 MW), (v) 

Vishnuprayag Scheme (400 MW), (vi) Tehri Dam Project, Stage-I (1000 MW), 

(vii) Tehri Dam Project, Stage-II (1000 MW), (viii) Koteshwar Dam Project 

(400 MW), and (ix) Dhauliganga H.E. Project, Stage-I (280 MW). 

With rising hydro power generation and improving efficiencies in distribution 

of electricity, Uttaranchal hopes to offer energy at stable prices for ecofriendly 

industrial development. Though the state is more or less sufficient 

in its energy generation to meet its own requirement, there is an urgent need 

to develop its huge untapped hydro power potential in an early and efficient 

manner, manage efficiently the hydro generation capacity of existing power 

stations and to develop and promote new Hydro projects with the purpose 

of harnessing hydropower resources in the state for economic well being and 

growth of the people in the whole region. 

2-4


In order to meet the load demand satisfactorily, it is considered essential to 

maintain a minimum gross margin of about 30 per cent over the projected 

peak demand while planning for expansion of power supply facilities. 

To bridge the gap between the demand for power and the availability of 

power, some of the major hydro-electric schemes identified in Ganga Valley 

for development are indicated below : 

i Tapovan 

(360 MW) 

Vishnugad 

ii Bowala 

(132 MW) 

Nandprayag 

viii Karanprayag Dam (252 MW) 

ix Lata Tapovan (108 MW) 

iii Kishau Dam (600 MW) x Vishnugad Pipalkoti (340 MW) 

iv Pala Maneri (416 MW) xi Pancheshwar Dam 

v Loharinag 

MW) 

Pala (520 

xii Chamgad Dam (400 MW) 

vi Koth Bhel (1000 MW) xiii Dhauliganga, Stage-II 

vii Utyasu Dam (1000 MW) 

The location of H.E. Schemes are indicated in Plate-1 enclosed. 

2.5 PRESENT STUDIES 

2.5.1 With a view to prioritize the large number of identified schemes to harness 

vast untapped hydro resources in the order of their attractiveness for 

implementation, Ranking studies were carried out by CEA. Subsequently, 

after consultation process initiated by Ministry of Power with various state 

agencies, CPSUs etc., it was considered appropriate that Preliminary 

2-5


Feasibility Report (PFRs) of selected hydroelectric projects be taken up so 

that feasibility of the scheme considered in ranking studies could be 

established. 

2.5.2 In order to achieve the above objective the present preliminary feasibility 

stage report presents the Gangotri H.E Project located in Uttarkashi district, 

as detailed in the subsequent Chapters. 

2-6

3.1 GENERAL 

CHAPTER – III 

THE PROJECT AREA 


The Gangotri H.E. Project is located on Bhagirathi river, a tributory of the 

Ganga. The Ganga in this region has two major tributaries viz Bhagirathi and 

Alaknanda with their confluence at Dev Prayag. Bhagirathi originates at 

Gangotri glaciers and flows west wards.. It passes through the rugged terrain, 

incise its course through steep gradients. The Gangotri H.E. Project is the first 

H.E. project located on the Bhagirathi river for its development for hydro 

power in the cascade development. Immediately after Gangotri, Bhaironghati 

H.E. Project is envisaged after joining of the Jadhganga river. Gangotri 

H.E.Project utilise the river bedfall of about 327.0 m with the diversion 

structure located at bed level of 2965.0 m. 

Immediately down stream of Gangotri H.E. Project, another project 

Bhaironghati H.E. Project is proposed which utilises the river bed fall of about 

100.0 m. The Gangotri H.E. Project is a Run-off-the-River scheme. With the 

arrangement of dam and gates, a small diurnal storage is created. It is 

proposed to locate the diversion dam at bed level EL 2965 m which is about 

2.5 km downstream of Gangotri shrine where by Kedar Ganga river joins 

Bhagirathi river from the south in Uttarkashi District. The project intake is 

approached by railway upto Rishikesh further 267 km by road upto 

Bhaironghati via Tehri-Uttarkashi-Gangotri highway and further 9 km by road 

to Gangotri H.E. Project diversion site. The ratio discharge of about 18.19 

cumecs passes through a tunnel of 5.20 km length and 2.50 m dia (D-shaped) 

lead the discharge to the under ground power station proposed to be located 

at Lat 31 0 01’ 29” N and Long 78 0 52’ 17.5” E. The tail race lead the 

3-1


discharge back to the river. The power station utilises an average hydraulic 

head of about 347.0 m. 

3.2 CLIMATE 

The available IMD observatory is at Dehradun which hardly represents the 

Uttarkashi climate. However at Dehradun peak winter extend from Dec. to 

Jan. months where the temperature remains at 2 0 C and during May- June 

months the maximum temperature is around 40 0 C. Rainfall during monsoon 

period (June to Sept.) is about 2770 mm. Large climatic variations are 

experienced in the intra-sub basin of the tributaries of Ganga. Gangotri 

project is located in Bhagirathi basin the climate of which could be considered 

more synonymous to Badrinath Met-station (IMD). Here substantial snowfall 

occurs during winter months ( Dec.-April) with average seasonal snowfall is 

about 4600 mm. Although some snowfall is experienced in other months 

also except during June and July months. 

3.3 SOCIO ECONOMIC PROFILE 

The entire state has undulating topography with lofty mountains jutting out 

and create the rugged terrain with steep valleys. The geology, soil texture and 

climate are highly variable including the habitation pattern. It has sparse and 

scanty population, small sized villages, scattered on the hilly land scape. 

Out migration of able bodied person is common, subsistance level agriculture 

based economy mostly prevails with marginal holdings, the infrastructural 

development becomes very costly. 

Uttarkashi District has an area of 15.8% and supports 4% population as 

compared to the state. It has lowest density of population of about 30 

persons per sq. km. as against that of 116 persons per sqkm of the state. 

3-2


The litracy rate both among total and female is lowest in the district standing 

at 47.2% and 23.6% as against state average of 59.6 and 42.9% respectively. 

It has largest population of schedule casts of about 22.8% against state 

average of 16.7%. 

The main work force of about 75% are engaged in primary and secondary 

sectors and balance in allied sectors. As regards land use pattern about 70% 

of land is under forest and barran lands. 

About 64% of the inhabited villages are connected with road and the 

remaining villages suffer because of remoteness and higher altitudes. 

As regard rural electrification Uttaranchal has 76.1% electrified villages and 

the per capita consumption of electricity of the state is about 245.6 Kwh. 

However, Dehradun and Naintal have much higher consumption where as 

Uttarkashi has the least of 43.7 kwh consumption. 

3-3

CHAPTER - IV 


TOPOGRAPHY AND GEOTECHNICAL ASPECTS 

4.1 TOPOGRAPHY AND PHYSIOGRAPHY 

The terrain is highly undulating with jutting peaks, steep valleys the rivulets 

and tributaries cut across and negotiate the mountains with rapids and 

steep gradients. The major tributaries of Bhagirathi, Alakananda, 

Yamuna, Tons originate from the foot of glaciers and snow capped 

peaks. The pucca road network cover only 64% of the inhabitated 

villages and rest of the villages are not be covered by roads due to 

higher altitude and remoteness. Bhagirathi river on which Gangotri H.E. 

Project is located originates at the foot of the Gangotri glaciers and 

flow westwards further Jadhganga joins Bhagirathi from the north down 

stream of Gangotri H.E. Project. 

Present PFR studies do not envisage topographical surveys and hence 

this write up is confined to physiographical aspects only. 

4.2 REGIONAL GEOLOGY 

The topography of the area around the proposed scheme is located in inner 

parts of Lesser Himalayas and outer parts of Central Himalayan is extremely 

rugged. In Central Himalayan portion the E-W trending strike ridges are 

characterised by steep northerly dip slopes and southerly consequent 

escarpments. In the inner parts of Lesser Himalayan Zones, the trend of 

ridges has been modified and controlled by the folding of rocks. The main 

drainage of the area is Bhagirathi River which originates form Gangotri 

Glacier at Gaumukh. In the upper reach, the river is fed by numerous streams 

such as Jadhganga, Jalandra Gad and Siam Gad. These streams appear to 

4 -1


be subsequence to joints in granite. The drainage pattern in Central 

Crystalline country is rectangular. In the rock of Garhwal Group, the tributary 

streams are mainly transversal. 

The Bhagirathi Valley is characterized glacial and U shaped upstream of 

Sukhi Gaumukh. A rapid down cutting by the river has formed a deep narrow 

gorge between Gangotri & Jangal Bridge. Downstream of Jangla, up to 

Jhala Bridge, the narrow gorge has been filled by sand and gravel due to 

the silting connected with the damming of river at Sukhi by a landslide. 

Further downstream of Suklhi, the true profile of valley has been masked as a 

result of massive landslides. The rock of the area have been grouped in to 

Garhwal Group, Central Crystalline and the meta sedimentaries, possibly 

equivalent to Martloi Formation by Kumar, Agarwal and Mukerjee (1969-79). 

The tectonic sequence observed in the area is as follows: 

NORTH 

Meta-sedimentaaries Black slates, garnet mica schist, quartz-biotite 

schist, garnet-mica schist, banded augen gneiss 

(Martoli Formation) 

------------------- FAULT------------- 

Central Crystallines Kyanite-garnet-mica 

schist and inter bedded augen and porphyritic 

gneiss, banded augen gneiss and garnet mica 

schist containing tourmaline, migmatite zone of 

mica schist gneiss, granite, amphibolite and 

marble/calc-silicate. 

4 -2


- - - - - - - - - - - -MAIN CENTRAL THRUST (MCT)- - - - - - - - - - - - - 

Garhwal Group Upper massive quartzite, white to light grey and 

green coloured, fine grained to gritty, occasionally 

schistose, current and graded bedded. 

Metavolcanics- occasionally with pillow lava 

structure, lenticular limestone/dolomitewith slate 

and minor quartzite; Lower quartzite and slate. 

4.3 GEOLOGICAL FEATURES OF THE PROJECT COMPONENTS 

The Gangotri Hydro-electric scheme envisages utilisation of 18.19 cumec 

rated discharge and 327 m river bed drop available in the river Bhagirathi, 

downstream of the Gangotri shrine and a power house at a place near the 

confluence of Jadhganga. For this, it is proposed to construct a diversion 

dam of low height at a location about 2.5 Km downstream of the Gangotri 

shrine. For diverting water into a 5.20 Km long tunnel on the right bank of 

river Bhagirathi and a power house also on the same bank of the river, just 

upstream of the place near the confluence. 

At the proposed diversion site, located just about a Km downstream of the 

confluence of the Rudugaira gad, the river Bhagirathi flows in the direction 

from S 65 0 E to N 65 0 W direction through a very tight nearly “U”- 

Shaped gorge, carved through tourmaline granite traversed by pegmatite 

veins which is designated as Gangotri granite. The granite is generally white 

in colour with dark-coloured laths and specks of tourmaline seen very 

prominently. The granite are intruded into the granite gneiss of the Central 

Crystalline Group which is the country rock in the area. The contact 

between the two types of rock occurring in the area, i.e., the tourmaline 

4 -3


granite and the gneiss occurs downstream of the Jangla bridge about 10-12 

Km downstream of the proposed dam site. The diversion structure is located 

at bed level of EL 2965 m and , consequently may face problems of snow ice 

cover and avalanches during the winter months. 

The base width of the gorge of the river Bhagirathi at the proposed diversion 

site, which may be of the order of 30-40 m only is completely occupied by 

the river water and both the banks of the gorge rise very steeply upto about 

50-60m on the right bank and upto a little farther higher elevation on the left 

bank. Thereafter, both the banks are for some distance much gentler and 

occupied by detached/transported blocks of rocks mixed with soil and 

support a dense forest which continues farther higher up. This flatish break 

in the profile on the banks of the gorge appears to mark the pavement (floor) 

of the Gangotri glacier, which now terminates at Gaumukh, around 19 Km 

upstream of the proposed diversion site, but is believed to have extended in 

the past geological times to many kilometers downstream of the proposed 

barrage site. The pavement of the erstwhile glacier is clearly and 

continuously seen down to the Jangla bridge, 5-6 Km farther downstream 

of Bhaironghati. 

The granite occurring at the proposed diversion site is profusely jointed and 

many of the joints are distinctly open. In regard to the depth of overburden is 

the river section at the proposed dam site, it is very difficult to guess a 

hazard. Nevertheless, in view of the well-known past glacial history of the 

river, the depth of overburden therein may be considerable. It is suggested 

that for the present, especially for the purpose of the PFR studies, the depth 

of overburden in the river bed at the dam site may be assumed to be of 

the order of over 10-15 m. 

4 -4


The steep gorge of the river at the diversion site is being continuously 

undercut by the river Bhagirathi. Cutting/erosion at the toe of the gorge 

results is gravitational adjustments along divisional planes in the rocks on 

the banks. This phenomenon is commonly referred to as slumping. It is 

feared that on both the banks of the river at the diversion site, The extent of 

slumping would be considerable, as is also indicated by the presence of 

open joints on the banks. 

In order to tie the diversion structure on to the firm rock, the slumped 

rock on both the banks would have to be stripped. The stripping may be of 

the order of 10-15 m at the HFL of the river and around 25-30 m at the 

crest level of the spillway. This operation would have to be undertaken with 

simultaneous planning for stabilization of bank above the stripped section. 

The stripping of the banks of the river in the gorge would, no doubt, increase 

its width and provide some additional space at the base of the gorge. 

However, it would still remain quite narrow and may not permit the 

sedimentation / de-silting structure to be located on the surface. Therefore, 

the structure may have to be located underground on the right bank. The 

highly jointed nature of the granite would necessitate consolidation as well 

as certain grouting in the bed and banks of the river for controlling 

foundation and abutment leakage. 

The 5.20 Km long HRT from the diversion structure to the surge shaftpower 

house is aligned in the direction S60 0 E - N60 0 W direction. It is likely 

to be driven through the highly jointed Gangotri granite in its entire length. 

It is hoped that the granite occurring at the tunnel – grade would have lesser 

number of joints that are seen on the surface. Further evaluation of likely 

rock condition along the proposed tunnel would have to be undertaken 

during the next stage of the project planning. 

4 -5


The power house of the scheme is proposed to be located on the right bank of 

river Bhagirathi, just upstream of the Jadhganga confluence. At the 

proposed location gorges of both the rivers Bhagirathi and Jadhganga are 

very narrow and steep. Consequently, there is no space for locating the 

power house on the surface. Therefore, the structure would have to be 

located underground in the Gangotri granites, which occurs in the area. 

The granite is traversed by several well-developed joints. The orientation of 

the joints will have to be studied in detail and a suitable orientation for 

locating the power house cavity would have to decided. The orientation of 

the tail race tunnel from the power house would also have to be decided in a 

similar fashion. On the basis of a preliminary evaluation of the joints is the 

granite, it appears that a NE – SW Orientations of the power house and the 

tail race channel would be a favorable direction with respect, to the joints is 

the granite. However, this would have to be confirmed/revised on the basis 

of joints actually encountered in an exploratory drift which could be made at 

the power house site during the next stage of studies for the scheme. 

4.4 GEOTECHNICAL APPRAISAL 

The head on Bhagirathi up to its confluence with Jadhganga is proposed to be 

utilized through the proposed Gangotri Hydroelectric project which is 

upstream most project on Bhagirathi River, followed by Bhairoghati and 

Harsil projects. The project envisages construction of diversion structure 

across Bhagirathi just downstream of confluence of Bhagirathi and Rudiguira 

Gad. The river in this reach flows through granitic rock which have intruded in 

to Martoli and Ralen Formations. The river has cut a deep gorge in this reach. 

The valley widens near Jangla, probably due to change in lithology. The 

granite is mainly biotite granite and tourmaline granite. These - have been 

correlated with Tourmaline Granite of Badrinath. The granites are jointed and 

intruded by pegmatite, aplite and quartz veins. The valley is narrow and 

4 -6


typical V-shaped near the diversion site. The thickness of overburden in the 

river bed and stability of abutment may be assessed before finally locating the 

diversion site. The water conductor system envisages the construction of 

5.20 km long head race tunnel. It is expected to be excavated through biotite 

granite which is intruded by aplite, pegmatite and silica veins. The biotite 

granite is expected to provide fair to good tunneling media in general except 

for reaches where joints are closely spaced and shear and local faults are 

encountered. The problem may be become more acute if these zones are 

water charged. The powerhouse is proposed to be located near the 

confluence. It is suggested that the structure be located in the area where 

adequate space for locating the structure and its appurtenance is available 

otherwise it may be designed as an underground structure. This geotechnical 

appraisal is based on the regional geological set up. 

4.5 SEISMOTECTONICS AND SEISMICITY 

Seismotectonically, the project are is located in Main Himalayan 'Seismic 

Zone demarcate by the Main Boundary Thrust (MBT) in south and downdip 

influence zone of the Main Central Thrust (MCT) in north, demonstrating 

predominantly thrust type of fault plane mechanism. It has been interpreted by 

Narula (1991) that the strain buildup in different sectors in this, domains takes 

place at different locales and in Utarkashi-Kumaon sector, this is concentrated 

around the MCT as evidenced by the clustering of the seismic events in this 

subdomain to be around this structural dislocation. The seismic status of MCT 

has been a subject of interest for quite some time, though direct geological 

evidences of neotectonic activity have not been recorded in the area. 

According to Narula (1991), the project area falls in Garhwal Seismic Block 

which, is constrained by Alaknanda tectonic flux fault in the east and Kautir or 

Kinnaur Faults in west. This domain contains another tectonic flux fault which 

is located in the project area. 

4 -7


MBT & MCT are the two major dislocation features of significance in the 

project area located about 20 km to 35 km in the southern direction. 

Seismically the project area traverses through highly active Himalayan 

seismic belt and falls in seismic zone V of the seismic zoning map of 

India [ IS 1893 (Part-I): 2002]. Therefore, a suitable seismic factor would 

have to be adopted for designing the structures in the area. 

4.6 SEISMIC REFRACTION SURVEY 

The seismic refraction survey was conducted along the dam axis to ascertain 

thickness of overburden and quality of bedrock. The both the Banks are 

massive rock in nature and almost as a vertical cliff. To investigate the 

overburden in river portion, as per the requirements of the investigations, it 

was considered mandatory to carry out one seismic spread along the river, to 

have maximum depth penetration. Due to massive rock and high slopes, and 

an extremely narrow width of river, the normal spreads fails to provide 

adequate penetration below riverbed. 

The seismograph used was Model BISON, GALILEO with liquid crystal 

display, graphic plotter, 3.5 inch disk drive, 486 CPU, IFP amplifiers and 16 bit 

A/D converters and RS – 232 interface. Moving-coil type digital grade vertical 

geophones, natural frequency 14 Hertz were used as sensors. 

The processing involves picking the first arrivals, input of data with geophone 

elevations and first arrivals, and final interpretation for velocity model. Latest 

sodtware SeisOptPocket was used for picking the first arrivals. Latest 

advanced software has been used for interpretation and velocity model 

computation of data obtained. 

4 -8


The velocity model has been developed using information from both the 

spreads and velocity measurements carried out on the rock face. The findings 

duly interpreted from velocity model are given as section. 

Seismic Refraction Survey conducted at Gangotri site depicts the presence 

of rock line at shallow depth near the banks but the rock line goes below 

upto 5-10 meters from the river bed. 

Based on velocity model three broad layers can be classified, a thick 

alluvium, an intermediate layer and rock with different units of subsurface 

layers (Plate-4.1). 

4 -9

5.1 GENERAL 

CHAPTER - V 

HYDROLOGY 


The Ganga river is one of the holiest rivers in India and many temples and 

religious places are situated on its banks right from its origin to its confluence 

near Sagar Island with Bay of Bengal. It drains an area of 8.61 lakh sq km 

and the basin is one of the most fertile basins of the country. 

Bhagirathi and Alaknanda are the two major tributaries of Ganga which 

originates from Gangotri and Kamet glaciers in Uttarkashi and Chamoli 

districts respectively of Uttaranchal state. Bhagirathi originates at an 

elevation of 7010 m while Alaknanda rises at an elevation 7800m. Both the 

Bhagirathi and Alaknanda rivers join at Deoprayag and thereafter it is known 

as Ganga. Jadhganga is the first major tributary of Bhagirathi originating 

near Tagala at an elevation 5300m and joins Bhagirathi at Bhaironghati. The 

river has very steep slopes in upper reaches and most of the area is covered 

by permanent snow and glaciers. Due to steep slopes and area covered by 

snow, there exists considerable quantity of perennial flow and as such have a 

large potential for hydropower development, though irrigation may not be 

feasible due to non existence of command area. CEA had identified several 

hydro electric sites in the basin. The Gangotri Hydro-Electric Project 

(CA=944sq km) is the first project identified on Bhagirathi river. The 

catchment area map of the project is shown in Plate No. 5.1 

This report contains the results of the Hydrological studies made for Gangotri 

H.E. scheme. The detailed studies in respect of water availability and Design 

5-1


flood are available in the report “ Hydrological studies – volume I, Ganga 

basin” September, 2003. 

5.2 HYDROMETEOROLOGICAL DATA 

No rainfall and discharge data at Gangotri site is available. However, 

observed discharges from 1971 – 72 at Uttarkashi (CA=4504 sq km) are 

available. The site is maintained by CWC. Discharge data for longer periods 

are available at 17 G&D sites (13 CWC sites and 4 States Governments) in 

the region, which are much downstream of Gangotri site. The data availability 

is given as under which has been utilised for developing the Regional Model. 

Table -1 

Sl. Name of River Organisation Period 

No Station 

1 Tehri Bilanganga CWC 1975-76 to 2001-02 

2 Joshimath Alakananda CWC 1975-76 to 2001-02 

3 Tehri Bhagirathi CWC 1975-76 to 2001-02 

4 Deoprayag Ganga CWC 1975-76 to 2001-02 

5 Maror Nayar CWC 1975-76 to 2001-02 

6 Deoprayag Bhagirathi CWC 1975-76 to 2001-02 

7 Rudraprayag Mandakini CWC 1975-76 to 2001-02 

8 Rishikesh Ganga CWC 1975-76 to 2001-02 

9 Rudraprayag Alakananda CWC 1975-76 to 2001-02 

10 Nandkesri Pinder CWC 1994-95 to 2001-02 

11 Chandrapuri Mandakini CWC 1976-77 to 2001-02 

12. Karnprayag Pindar CWC 1976-77 to 2001-02 

5-2


Sl. Name of River Organisation Period 

No Station 

13 Uttarkashi Bhagirathi CWC 1971-72 to 2001-02 

14 Raiwala Ganga State Govt. 1946-47 to 1983-84 

15 Maneri Bhagirathi State Govt. 1964-65 to 1984-85 

16 Lambagarh Alakananda State Govt. 1969-70 to 1990-91 

17 Tapovan Alakananda State Govt. 1973-74 to 1981-82 

Long term flood peaks are available at Raiwala on Ganga (1901 to 1992), 

Tehri on Bhagirathi (!963 to 1978), Maneri at Bhagirathi (1964 to 84) besides 

at G&D sites on Alaknanda, Sarda, Tons and Yamuna rivers. 

5.3 ESTIMATION OF WATER AVAILABILITY 

5.3.1 Regional Model 

The proposed Gangotri site is in high altitude area whose major portion of the 

catchment (a small fraction of the nearest observed G&D catchment area) 

area is covered by snow and glaciers. As such the traditional method of 

rainfall run off or run off-run off model may not be feasible due to non 

availability of requisite data. A regional model has been developed on 10 daily 

basis utilising the 10 daily flows of each 17 G&D sites (CWC and State 

Government) together with the mean annual catchment rainfall and the 

percentage of area intercepted by glacier, snow and forest. The general 

format of the linear model for the G&D site is as under: 

q = K + a * s + b * g + c * f + d * (RF) 

or Q = K * (CA) + a * (SA) + b * (GA) + c * (FA) + d * (RF) * (CA) 

Where, q = Average specific yield of G&D site 

5-3


Q = Average yield of G&D site 

CA = Total catchment area in sq. km 

GA = Total area under glacier in sq.km 

SA = Intermediate area between glacier and permanent 

snow line in sq.km 

FA = Total forest area in sq.km 

RF = Mean annual catchment rainfall in mm 

K, a, b, c, d = Constant of the model 

s = percentage of net snow area to total catchment 

area 

g = percentage of glacier area to total catchment area 

f = percentage of forest area to total catchment area 

The linear regional model was developed for Bhagirathi and Alaknanda basin. 

After studying the physical parameters responsible for run off for each 

catchment upto G&D site, the one parameter, two parameter, three parameter 

and four parameter linear models have been developed for each 10 daily 

block period. The one parameter model considers the specific yield of G&D 

sites Vs catchment area, whereas the remaining models consider the 

catchment area, glacier area, forest area, net snow area, mean annual 

catchment rainfall and the specific yield. After attempting the various 

permutations and combinations, the model which gives the maximum 

correlation coefficient was selected for estimating the dependable flows at 

Gangotri site. 

5.3.2 Dependable flows 

Using the most suitable regional model developed for each 10 daily block, the 

90%, 50% dependable flows and the average flows have been computed for 

the Gangotri project site (CA=944 sq. km) as under: 

5-4


Units:m 3 Items June I June II 

/sec 

June III July I July II July III Aug I Aug II Aug III 

90% 25.2 33.0 42.6 38.6 46.3 46.2 35.8 34.9 38.7 

50% 47.7 62.3 75.8 73.1 91.5 68.8 66.6 57.6 63.6 

Average 51.7 63.7 80.6 80.3 94.2 72.0 67.1 58.2 64.9 

Sep I Sep II Sep III Oct I Oct II Oct III Nov I Nov II Nov III 

90% 27.9 21.9 14.3 12.1 7.9 8.0 6.4 5.9 5.3 

50% 52.1 40.3 23.2 18.7 13.1 12.7 10.7 9.5 8.2 

Average 54.7 42.2 24.9 19.7 14.6 13.7 11.6 10.0 8.8 

Dec I Dec II Dec III Jan I Jan II Jan III Feb I Feb II Feb III 

90% 4.8 4.5 3.4 4.2 3.7 3.4 3.2 2.8 2.6 

50% 7.9 7.5 6.5 6.3 6.0 5.3 4.9 4.6 4.6 

Average 8.4 8.1 7.1 6.5 6.1 5.4 5.2 4.7 4.7 

Mar I Mar II Mar III Apr I Apr II Apr III May I May II May III 

90% 3.6 3.4 3.7 3.5 3.5 6.1 10.6 12.9 18.7 

50% 6.0 6.2 6.7 6.2 7.6 12.4 18.6 25.1 33.4 

Average 6.4 6.7 7.0 6.5 7.9 13.3 19.9 27.4 35.1 

5.4 ESTIMATION OF DESIGN FLOOD 

Since the continuous discharge data for rainy season and concurrent rainfall 

is not available, it is not possible to estimate the design flood by unit 

Hydrograph method. 

The peak flood discharge at Gangotri site has been estimated based on the 

methodology indicated in the Flood Estimation Report for Western Himalayas, 

Zone 7 of CWC and Regional Frequency analysis (based on 5 and 10 G&D 

sites) and Synthetic unit hydrograph approach based on Snyder’s method. 

The results of the study are as under: 

5-5


Methodology Return Period 

100 years/ SPF 

(m 3 /Sec) 

i) Flood Estimation Report, CWC 

2452 

ii) Regional Frequent Analysis (5 G&D sites). 

Iii) Regional Frequency Analysis (10 G&D sites). 

iv) Snyder’s Method 

v) Recommended Design flood value. 

1824 

2280 

1592 

2500 

As furnished above design flood (SPF) of 2500 m 3 /sec is recommended for 

studies. 

5.5 SEDIMENTATION 

Since Gangotri site HE scheme is identified as run of the river scheme, the 

sedimentation studies are not considered necessary as in the case of storage 

structures. However, based on the experience gained at various Power 

Stations in that valley, it is proposed to exclude silt particles of size 0.20 mm 

and above from the water before it enters the power house. This aspect will 

be considered while designing the civil structures. 

5-6

5.6 Observations of CWC 


The draft report of this project was submitted to CEA for perusal during 

October 03. The observations received from CWC on the Hydrological studies 

of this project and the replies for above observations, submitted by WAPCOS 

are enclosed as Appendices 1.1 and 1.3. 

5-7


CHAPTER – VI 


CONCEPTUAL LAYOUT AND PLANNING 

Gangotri H.E. Project is proposed as Run-off-the river scheme on the river 

Bhagirathi to tap its hydropower potential. The diversion structure is located 

1.0 km downstream of confluence of Rudugar Gad from the left bank or 2.5 

km before the holy Gangotri shrine in Uttarkashi district. The project 

envisages to divert the water of Bhagirathi into water conductor system by 

means of a diversion structure (a concrete gravity dam) across the river. The 

water conductor system comprises of an intake, underground desilting 

chambers followed by a 5.2 km long head race tunnel of 2.5 m diameter 

(D-shaped), a surge shaft of 6 m diameter, a pressure shaft of 2.0 m dia to 

feed one unit of 55 MW housed in an underground power house. A 450 m 

long tail race tunnel discharges the water back into the river Bhagirathi just 

upstream of another proposed Bhaironghati H.E. scheme head works. 

6.2 LAYOUT STUDIES 

6.2.1 The Bhagirathi river rises at EL 7010 m and falls steeply untill Gaumukh at EL 

4000 m to Gangotri, the river bed fall is about 1000 m in 50 km stretch. 

Thereafter, it runs in a gentle to steep slopes in various stretches and is joined 

by Jadhganga at EL 2625.0 m. 

As per CEA re-assessment studies the hydro-potential of river Bhagirathi is 

proposed to be exploited by potential schemes in a cascade development and 

the projects serially planned are Gangotri, Bharion Ghati and Harsil Schemes 

now proposed for PFR studies. 

6-1


6.2.2 The entire stretch of river between proposed diversion site of Gangotri 

scheme to power house site was inspected and it was observed that both the 

banks of Bhagirathi at a reach 2.5 kms d/s of the Gangotri shrine are occupied 

by massive steep rocky slopes. The pondage created at this site selected 

shall be within safe levels at the Gangorti Shrine. 

6.2.3 As per CEA proposal, the diversion site for Gangotri H.E. scheme is proposed 

about 2.5 km d/s of Gangotri shrine at bed level 2960.0 m. After inspection 

the site for diversion site was planned to be shifted upstream as much as 

possible so that additional head could be utilized for power generation without 

effecting the Gangotri Shrine. The site selected was at river bed level EL 

2965.0 and 50 m further up stream of the earlier CEA site. 

6.3 RIVER DIVERSION WORK 

6.3.1 The aspect of isolating the site for construction activity in the deep river valley 

portion was examined for two scenarios i.e. with and without the provision of 

diversion tunnel through abutment. As the diversion site is located in a 

narrow valley it was not found practical to isolate the construction area without 

the provision of diversion tunnel. 

6.3.2 A diversion tunnel of 4m diameter circular and 400 m long is proposed along 

right bank to divert flood of 50 cumecs for the construction of dam & 

appurtenant works. However, during monsoon season, excess discharges 

beyond the capacity of diversion tunnel is expected to pass over the coffer 

dam and the constructed portion of the dam. The tunnel inlet is proposed to 

be provided with a gate of size 4.50 m x 4.50 m which will be operated by 

means of a rope drum hoist at the time of plugging the diversion tunnel. 

Suitable coffer dams located approximately 100 m u/s & 150 m d/s of the 

dam axis are proposed. The u/s coffer dam will be 7 m high with 7.0 m base 

6-2


width while the d/s coffer dam will be 6 high with base width of 6.0 m. These 

structures are proposed of masonry type with colcrete. 

6.4 DIVERSION DAM 

6.4.1 The type of dam to be adopted i.e Earth dam or concrete dam is governed by 

the topographical, geotechnical and availability of construction materials 

considerations. The requisite construction materials for Earth dam alternative 

are not expected to be available in the vicinity of project area and also not 

possible for the narrow gorge. In view of the rock exposures along steep 

valley on both the banks of the river and shallow thickness of overburden in 

the river bed are anticipated. Accordingly a concrete gravity structure with a 

spillway in the deeper gorge portion is proposed at this site. Concrete dam, 

26 m high above the deepest river bed (El 2965.0 m) 110.0 m long comprises 

of 7 blocks. Three overflow blocks in the deeper gorge portion are provided to 

pass the design flood. A foundation gallery running all along the abutment is 

also proposed from drainage, grouting and maintenance considerations. A 

downstream slope of 0.8:1 is proposed for the dam section keeping in view 

the seismicity of the area (zone V, as per BIS 1893) 

6.4.2 Reservoir 

Keeping in view the storage characteristics of the valley upstream, the crest of 

spillway is proposed at El 2975.0 m. The crest of power intakes are kept 7.0 

m lower then the MDDL of El 2984.0 m. This is to ensure minimum water 

cushion requirements above the intake tunnels from air entrainment 

considerations. Storage to meet the diurnal peaking requirements has been 

provided between MDDL and FRL as it is a Run-off the River type 

development. Accordingly, MDDL and FRL are proposed at El 2984.0, and El 

2989.0 m respectively which provide live storage of around 0.91 M cum. 

6-3

6.4.3 Spillway & Energy Dissipation 


An ogee spillway with radial gates and breast wall is proposed to pass the 

design flood of 2500 cumecs corresponding to SPF. Three bays, each with 

clear opening of size 12.5 m x 14.0 m (height) are proposed to cater to design 

flood discharge which is inclusive of one gate for additional factor of safety in 

consideration of 10% of gates inoperative as per codal requirement. Radial 

gates will be operated by means of hydraulic hoists. Provision of stoplog 

gates with gantry crane is also made. 

Since this project is located in high altitude area (about EL 3000 m above 

MSL) and most of the time the reservoir water surface will be under sub zero 

temperature. To generate power for maximum period and for smooth running 

of the power plant, de-iceing arrangements are proposed to be provided. 

Energy dissipation is proposed through stilling basin of 35 m length. 

Protection works in the form of stone pitching are provided immediately 

downstream of stilling basin from considerations of scour and water depth. 

The Layout details of Dam and Spillway are shown in Drg 

No.WAP/PFR/GANGOTRI/1003 (R1) &1004 (R1). 

6.5 INTAKE AND DESILTING CHAMBER 

6.5.1 One intake structure is proposed on the right bank of the river upstream of 

the Diversion structure with its invert at El 2977.0 m i.e. 2.0 m above the 

spillway crest level to avoid entry of rolling debris into the water conductor 

system during floods. One no. intake tunnel, 2.75 m dia (D-shaped) is 

proposed on the right bank to carry design discharge of 21.83 cumec 

(including 20% flushing discharge). A trashrack is proposed at the entry so 

6-4


that debris /particles exceeding 75 mm do not enter the water conductor 

system. 

6.5.2 One underground desilting chamber is provided about 120.0 metre 

downstream of intake structure to remove particles of size 0.2 mm and above 

to protect the turbine parts against erosion. The chamber proposed is of size 

110 m x 8 m x 9 m (depth) and is designed to achieve 90% efficiency for silt 

removal. The chamber is designed to pass design discharge of 21.38 cumec 

and is provided with a gate on downstream end to isolate for routine 

maintenance. The bed of the trough is provided with a longitudinal duct of 2.0 

m dia to remove the silt laden water through a silt flushing tunnel to the river 

downstream. 

6.6 HEADRACE TUNNEL 

6.6.1 The design discharge of 18.19 cumecs is carried downstream of desilting 

chamber through 2.5 m dia D-shaped headrace tunnel, 5.20 km long to 

meet the surge shaft. The alignment of the tunnel has been optimally fixed to 

provide adequate rock cover below the nallah crossings. 

6.6.2 The excavated tunnel section is proposed to be provided with suitable support 

system depending upon the type of rock strata met. Accordingly, the entire 

tunnel reach has been tentatively divided into 4 categories depending upon 

the type of rock i.e. Good, Fair, Poor and Very Poor. It is presumed that 20% 

of the tunnel reach encounters poor/very poor rock conditions while in 

remaining reach Good/Fair rock conditions are met. A 300 mm thick PCC 

lining of M20 grade concrete is proposed for the headrace tunnel. Provision 

for contact grouting & consolidation grouting has also been made. 

6-5


The details of the Rock support system are shown in Drg. No 

WAP/PFR/GANGOTRI/1005 (R1). 

6.7 SURGE SHAFT & PRESSURE SHAFT 

6.7.1 An 6.0 m dia and 92.0 m high simple surge tank is proposed at the end of 

headrace tunnel to release the effect of mass oscillations in the tunnel and to 

provide immediate storage requirement near the power house in case of 

sudden acceptance of load. The bottom elevation of surge tank has been so 

fixed as to provide adequate water cushion below the minimum down surge 

level. Similarly, it is ensured that maximum upsurge level is contained within 

the surge shaft. 

The surge shaft is likely to be excavated in tourmaline granite rock formations. 

It is proposed to provide 75 mm thick shotcrete with 4m long rock bolt at 

suitable intervals. Reinforced concrete lining (M25 grade) 1.0m thick, is 

proposed in the deeper reaches reducing to 0.6 m thickness in the upper 

portion. Provision for consolidation grouting & contact grouting is also made 

to ensure proper consolidation of rockmass around the surge shaft. 

6.7.2 A vertical pressure shaft of size 2.0 m diameter is proposed downstream of 

surge shaft keeping in view the adequacy of horizontal and vertical rock cover 

as per codal requirement. Pressure shaft drops from El 2928.0 m to 

El 2634.50 m in line with the center line of distributor. The horizontal portion 

of pressure shaft is to feed to 1 unit of 55 MW. 

The pressure shaft liner is designed taking into account 30% rock participation 

and 40% as water hammer head. High tensile steel of grade A-517 is 

proposed for liner so as to restrict the liner thickness to reasonable limits to 

6-6


obviate the need for stress relieving. Liner thickness varies from 8 mm to 20 

mm in the pressure shaft reach. 

6.8 POWER HOUSE 

The underground power house is proposed as the river banks are steep and 

there is paucity of space for surface power house. The underground power 

house complex comprises of one cavern of 20.5 m width. The machine 

cavern is 20.5 m wide, it house 1 unit of 55 MW along with 15 m long service 

bay and 40 m x 6 m auxiliary room. The generator floor level is kept at EL 

2642.0 Centre line of units is at EL 2634.50 m and invert level of draft tubes 

kept at EL 2629.50 m. EOT crane of 150/20 tonnes capacity shall be 

provided at crane beam level at EL 2650.0 m and travel up to service bay end 

also. One main inlet valve is also provided. The transformer bay is inside the 

power house cavern and is 6 m wide to accommodate transformer and GIS. 

A cable carriage is provided from this cavern to the outdoor switchyard at the 

roof level. The draft tubes shall be provided with a draft tube gate operated 

by a gantry crane installed inside the main power house cavern. The TRT of 

3.0 dia (D-shaped) of length 450.0 m shall have reverse slope to meet the 

river bed level. The power house cavern shall be approached by a main 

access tunnel starting from the main road. 

6.9 ELECTRO - MECHANICAL WORKS 

6.9.1 General 

The installed capacity would be provided by one no. Vertical Axis Francis 

turbine driven generating unit of 55 MW. It is proposed to provide spherical 

type Inlet Valve for each turbine, which would be accommodated in the 

powerhouse cavern. 

6-7


The generation voltage of 11 kV would be stepped up to 220 kV through three 

single phase 20 MVA, 11/220 kV ODWF type unit step up transformers 

located in powerhouse cavern. The 11 kV phase isolated phase busducts 

would connect the 11 kV generator terminals with 11 kV bushings of step up 

transformer. The 220 kV terminals of the transformer would be connected 

with 220 kV Gas Insulated Switchgear (GIS) located on a floor above the 

transformer in powerhouse cavern. 

The arrangement of generating equipment, unit step up transformer, etc. is 

indicated in Drgs. No. WAP/PFR/GANGOTRI/1007 (R1) & 1008 (R1). 

The GIS would accommodate 4 bays in which 1 for generator incoming, 2 for 

outgoing 220 kV transmission lines and one for step down transformer. The 

power generated would thus be evacuated through 2 nos. 220 kV 

transmission lines. The single line diagram is shown in Drg. No. 

WAP/PFR/GANGOTRI/1009 (R1). 

6.10 BRIEF PARTICULARS OF EQUIPMENTS 

6.10.1 Turbine and Governor 

The upstream levels, tailrace levels and heads available for power generation 

are indicated below : 

i) Upstream Levels 

• FRL EL 2989.0 M 

• MDDL EL 2984.0 M 

ii) Tailrace Levels 

• Maximum EL 2643.0 M 

• Minimum EL 2641.0 M 

6-8

iii) Heads 

• Maximum net head 339.00 M 

• Minimum net head 332.00 M 

• Rated head 336.33 M 


For this project there is a choice in selection of type of turbine to be used. The 

turbine could be either Francis or Pelton type. One of the important aspect 

which dictates the choice of turbine is the need of part load operation of the 

generating units. In the run of the river scheme without any pondage, Pelton 

wheel would be preferred as the generating units would need to be operated at 

part load operation depending upon the discharge available. This project is run 

of the river type with pondage for peaking purpose therefore both Pelton and 

Francis type turbine are suitable with reference to above aspect. However, based 

on the following main advantages, Francis type turbine, is chosen for this project : 

1. Francis turbine is cheaper as compared to Pelton wheel because of high 

speed. 

2. Peak efficiency of Francis turbine is higher 

3. Pelton wheel runner is set 3 to 4 metres above the maximum tail water 

level as such there is permanent loss of head in power generation. 

4. The silt erosion of the runner is lesser there by requiring less frequent 

maintenance / replacement of runner and the repair of silt eroded turbine 

components is easier in case of Francis turbine. This is an important 

aspect for the stations located in Himalayas. 

The turbine would be suitably rated to provide 55 MW at generator terminals 

at rated head of 336.33 M. The speed of turbine has been determined as 600 

RPM. The centerline of turbine runner has been set at EL 2634.5 M whereas 

the minimum TWL is at EL 2641.0. The governor would be electro-hydraulic 

6-9


digital PID type suitable for fully automatic control. The closing time of wicket 

gates would be so adjusted so as not to increase the speed rise and pressure 

rise more than 45% and 30% respectively under full load throw off condition. 

6.10.2 Main Inlet Valve 

It is proposed to provide an Inlet Valve of spherical type for turbine as second 

line of defence in stopping the water flow to the turbine when due to governor 

malfunctioning, the generating unit may tend to go to runaway speed. During 

the time when the generating unit is under standstill condition, it would help in 

minimizing the water leakage through the wicket gates of the turbine. The 

opening of the valve would be achieved through pressurized oil servomotor 

and closing through counter weight. 

6.10.3 Generator and Excitation System 

The generator shaft would be directly coupled with the turbine shaft. The 

bearing arrangement would be semi-umbrella type with combined thrust and 

guide bearings below the rotor and one guide bearing above the rotor. The 

generator would be of the closed air circuit water-cooled type. The main 

parameters of the generator would be as indicated below: 

i) Rated out put - 55 MW 

ii) Power factor - 0.9 lag 

iii) Speed - 600 RPM 

iv) Class of Insulation of 

stator and rotor winding - Class 'F' 

v) Generation Voltage - 11 kV 

6-10


The generators would be provided with static excitation equipment and 

voltage regulator. Necessary power for excitation would be provided by 

tapping the generator terminals. 

6.10.4 Unit Step-Up Transformer 

Three single phase 20 MVA, 11/ 220 kV transformers, would be provided for 

generating unit. This transformer would be located in powerhouse cavern. 

The 11 kV bushings of the transformer would be connected with 11 kV 

terminals of generator through 11 kV busduct. The 220 kV bushing would be 

connected with 220 kV Gas Insulated Switchgear. 

6.10.5 EOT Crane 

The heaviest equipment which the powerhouse crane is required to handle 

during erection and subsequently during maintenance is the generator rotor. 

The weight of the generator rotor has been estimated to be about 131.5 

tonnes. It is proposed to provide EOT crane of 150/ 20 tonnes capacity. 

6.10.6 Auxiliary Equipments and Systems For The Power House 

Following equipments for the auxiliary systems of the powerhouse would be 

provided: 

i) Cooling water system for turbines, generators, unit step up 

transformers etc. 

ii) Drainage System 

iii) Dewatering system 

iv) High pressure compressed air equipment for governor and MIV etc. 

v) Low pressure compressed air equipment for station services 

6-11


vi) 415 V LTAC supply system comprising station service transformers, 

unit auxiliary transformer, station service board, unit auxiliary boards 

etc. 

vii) D.C. supply system comprising 220 V DC battery, chargers, DC 

distribution boards etc. 

viii) Ventilation system for the power house 

ix) Air conditioning system for control room, conference room etc. 

x) Illumination system 

xi) Earthing system 

xii) Oil handling system 

xiii) Power and control cables 

xiv) Fire protection system 

6.11 220 KV SWITCHYARD 

It is proposed to provide 220 kV, Gas Insulated Switchgear located in power 

house cavern having 4 bays. 1 bay for generator incoming, 2 bays for 220 kV 

transmission lines and 1 bay for step down transformer. Double bus bar 

arrangement at 220 kV has been proposed. 

6.12 OBSERVATIONS OF CEA & CWC 

The Draft Report of this project was submitted to CEA for perusal during 

October 03. The observations from the various directorates of CWC and CEA 

on the civil and electrical aspects have been considered and taken care in this 

report. The detailing has been kept to the possible extent as the report 

pertains to the preliminary feasibility stage studies. 

6-12

7.1 GENERAL 

CHAPTER-VII 

POWER POTENTIAL STUDIES 


The power potential studies have been carried out for Gangotri Hydel 

Scheme. The projected power supply position for 11 th Plan also indicated 

that there would be shortage of peak power in Uttranchal State as well as 

in Northern region. The execution of this project would help in reducing 

the gap between supply and demand of power. 

This is a Run of river type development with diurnal storage for peaking 

purpose and would utilize a rated head of water of 336.33 m. The power 

house would be of Under ground type. 

7.2 Fixation Of FRL/MDDL 

The FRL of the pondage has been fixed at EL 2989.0 m so as to get 

adequate storage capacity for peaking operation of the plant during lean 

period. The MDDL of EL 2984.0 m has been fixed keeping the 

requirement of minimum cushion of water above the headrace tunnel 

(HRT) to rule out the air entrainment into the HRT. The storage at FRL is 

computed as 4.370 million cubic metres whereas the storage at MDDL is 

estimated as 3.460 million cubic metres, thus making available live storage 

of 0.910 million cubic metres. The levels v/s capacity characteristics of the 

pondage are indicated in Annex 7.1. 

7.3 FIXATION OF TAIL RACE WATER LEVEL (TWL) 

The minimum tail water level which corresponds to discharge of one 

generating unit at 10% load has been determined as EL 2641 m. The 

Maximum TWL at EL 2643 m corresponds to all the generating units 

running at full load. 

7-1


These levels, however, would need to be verified when it would be possible 

to prepare tail rating curve. 

7.4 WATER AVAILABILITY 

The available data of water flows on 10 daily basis has been analysed in 

Chapter No. 5 on “hydrology”. Water flows determined in 90% dependable 

year and in 50% dependable year, have been utilized for computing power 

benefits. 

7.5 TYPE OF TURBINE 

The specific speed of the turbine at the head 336.33 m works out to be 86 

which lead to the choice of Francis Turbine to be used for this station. The 

following efficiencies applicable for Francis turbine driven generating unit 

have been considered for power potential studies. 

- Efficiency of Turbine 93.5% 

- Efficiency of Generator 98.0% 

- Combined efficiency of Turbine 

and Generator 91.63% 

7.6 INSTALLED CAPACITY 

7.6.1 The power potential with different installed capacities from 30 MW to 80 

MW in 90% dependable year is indicated in Annex-7.2. The simulation 

studies have been carried out with FRL at 2989 m, MDDL at El 2984 m, 

losses in water conductor system as 9 m and average TWL at 2642 m. The 

study indicated that the firm power is 10.28 MW continuous. Considering 

four hours peaking, the installed capacity required would be about 61.68 

MW. 

7.6.2 For optimization of Installed Capacity, annual energy generation (kWh), 

Incremental Energy generation d (kWh), and ratio of Incremental energy 

and Incremental Installed Capacity d (kWh) /d (kW) have been computed 

for 90% dependable year for installed capacity varying from 30 MW to 80 

7-2


MW. The results are indicated in Annex-7.3. It would be seen there from 

that d (kWh) /d (kW) drops steeply for increase in installed capacity from 55 

MW to 60 MW. 

7.6.3 Keeping in view the system requirements and analysis of Incremental 

energy and Incremental installed capacity, the installed capacity of 55 MW 

is considered optimum. With installation of 55 MW, the load factor of 

operation during lean flow period works out to be 18.69 % corresponding to 

4.49 hrs of peaking. 

7.6.4 Three are two options for number of generating units to be installed i.e. 

1x55 MW 

2x27.5 MW 

The station is to be connected with large power system of Northern region 

and therefore outage of this station would have negligible effect on the 

stability of the system. Further as the scheme is provided with durinal 

storage, requirement of part load operation would be minimum. Further 

installation of one unit would be more economical as compared to two 

units. Considering the above, it is decided to install only one unit of 55 MW. 

The turbine would be suitably rated to provide 55 MW at generator terminal 

at rated head of 336.33 M. The speed of the turbine is determined at 600 

RPM. 

7.7 RESULTS OF STUDIES 

Annual energy generation in 90% dependable year (Design energy) and in 

50% dependable year have been computed for installed capacity of 55 MW 

(1x55 MW) and are indicated in Annexures 7.2 and 7.4 respectively. The 

results are also briefly indicated below. 

7-3

Particulars 90% dependable 

year 


50% dependable 

year 

Annual Energy Generation (Gwh) 264.76 327.7 

MW continuous 10.28 17.0 

Average annual load factor 54.95 68.02 

Load factor in lean flow months 18.69 % 30.91 % 

The design energy computation have been carried out and indicated in 

Annexure 7.5. The design energy 256.64 GWh would be considered for 

financial evaluation. The live storage available with FRL at EL 2989.0 m and 

MDDL at 2984.0 m would be 764.215 MWh (0.91 Million cubic meters) 

whereas the storage required for peaking operation works out 246.72 MWh. 

Thus sufficient storage is available for peaking operation of the station. 

7.8 CONCLUSIONS 

The power potential studies carried out indicate that installed capacity of 55 

MW comprising one unit of 55 MW would be required for this Hydel scheme to 

derive optimum power benefits. This station would afford generation of 

264.76 Million units in a 90% dependable year. 

7.9 RECOMMENDATIONS FOR FURTHER STUDIES 

7.9.1 At DPR stage, based on the data available of topographic survey, tail race 

rating curve should be evolved so that in energy computations the head 

utilized for power generation is corrected with the change in tail race level 

corresponding to discharge. In the present study, tailrace level was 

considered constant. 

7.9.2 The storage at FRL and MDDL should be computed with more accuracy 

based on the data of topographic survey. 

7-4

CHAPTER VIII 

POWER EVACUATION 


8.1 APPRAISAL OF EXISTING POWER EVACUATION FACILITIES 

The Project is located at latitude 31-01-29 (D-M-S) North and longitude 78- 

52-17.5 (D-M-S) East. The installed capacity of Uttaranchal State is 1286.15 

MW as on March 2003. Its peak demand has been estimated as 771 MW 

whereas the met peak is 705 MW in the present scenario. This amounts to 

deficit of 66 MW (8.56%). Accordingly, energy requirement is 3774 MU 

against the available energy of about 3670 MU. This depicts deficit of 104 

MU (2.8%). For the purpose of evacuation of power pooling has been 

proposed for various Hydro Electric Power Projects. As per the geographical 

locations the following proposed Hydel Projects lie between the longitude 

78.5 o N to 79.5 o N namely Harsil, Bhaironghati, Gangotri, Jadhganga, Karmoli 

Hydro Power Projects. The next group of Hydro Electric Projects which lie 

between longitude 79.3 o N to 80 o N are Badrinath, Gohana Tal, Rishiganga II, 

Rishiganga I, Jelum Tamak, Deodi, Devasari Dam and Malari Jelum. 

Whereas in the next series the Hydro Electric Projects which lie between 

longitude 80 o to 81 o N are Mapang Bogudiyar, Sirkari Bhyol Bogudiyar, Sirkari 

Bhytol Rus Bagar, Khasiya Barah, Khartoli Lumti Talli, Kalika Dantu, Garba 

Tawaghat, Sobala Jhimrigaon, Sela Urthing, Chhanger Chal, Bokang Beiling. 

The power map of Uttranchal as on 1/1/2002 is shown at Annex-8.1. 

8.2 PROPOSED EVACUATION SYSTEM TO NEAREST FACILITY 

A map has already been prepared indicating various proposed Hydro Electric 

Projects for the purpose of preparation of prefeasibility report (PFR) indicating 

their locations which may be seen at Annex-8.2. 

8-1


8.3 ARRANGEMENT FOR EVACUATION OF POWER FROM GANGOTRI HEP 

The 55 MW power generated at 11 kV at Gangotri HEP will be stepped upto 

220 kV by unit step-transformers. The power would be transmitted to nearby 

Bhaironghati HEP. Proposed line from Gangotri HEP for evacuation of power 

is shown at Annexure - 8.3. 

8.4 ROUTE LENGTH AND COSTING OF 220 KV TRANSMISSION LINE FOR 

EVACUATION OF POWER FROM GANGOTRI HEP 

The power of this project is intended to be evacuated by proposed 220 kV 

D/C line to Bhaironghati HEP. The length of line has been estimated as 10 

km (220 kV D/C line) from Gangotri to Bhaironghati HEP. The cost of this line 

is estimated as Rs. 7.50 Crores. However it is proposed to keep spare 

space/provision for second outgoing 220 kV transmission line but its cost has 

not been included in E & M estimates. 

8-2

CHAPTER – IX 


INITIAL ENVIRONMENTAL EXAMINATION STUDIES 


The Initial Environmental Examination of the proposed Gangotri hydroelectric 

project, has following objectives, which need to be considered during various 

phases of the development : 

• provide information on baseline environmental setting; 

• preliminary assessment of impacts likely to accrue during construction 

and operation phases; 

• identify key issues which need to be studied in detail during 

subsequent environmental studies 

It is essential to ascertain the baseline status of relevant environmental 

parameters that could be significant changes as a result of construction and 

operation of the project. In an 

Initial Environmental Examination (IEE) study, baseline status is ascertained 

through review of secondary data, reconnaissance survey and interaction with 

the locals. 

The Preliminary Impact Assessment conducted as a part of IEE Study, is 

essentially a process to forecast the future environmental scenario of the 

project area that might be expected to occur as a result of construction and 

operation of the proposed project. The key environmental impacts which are 

likely to accrue as a result of the proposed developmental activity are 

identified. Various impacts, which can endanger the environmental 

9-1


sustainability of a project, are highlighted for comprehensive assessment as a 

part of next level of environmental study. 

9.2 ENVIRONMENTAL BASELINE SETTING 

The study area covered as a part of IEE study includes the area within 7 km 

radius of various project appurtenances. The data was collected through 

review of existing documents and various engineering reports and 

reconnaissance surveys. The various parameters for which baseline setting 

has been described have been classified into physio-chemical, ecological and 

socio-economic aspects. 

9.2.1 Physio-Chemical Aspects 

a) Water Quality 

The proposed Gangotri hydroelectric project is located in a relatively 

inaccessible area, with low population density. Such areas are characterised 

by absence of pollution sources, which is also reflected in excellent water 

quality. 

The present population in the catchment area intercepted at the diversion site 

has only one village, i.e. Gangotri. The total population of the village, as per 

1991 census was 123. Considering the decadal population growth rate as 

25% to 30%, the present population is of the order of 160-170. The sewage 

so generated, too outfalls into various streams or nallahs flowing adjacent to 

the settlements and ultimately reaches river Bhagirathi. The total BOD loading 

from domestic sources in the catchment area is of the order of 7 kg/day. The 

quantity of BOD loading is insignificant to cause any adverse impact on water 

quality, even for the minimum flow in the river. There are no industries in the 

9-2


area. The area under agriculture is quite low in the catchment area. Use of 

various agro-chemicals too is negligible. Thus, the pollution loading in the 

area is quite low, which is reflected in excellent water quality. 

b) Landuse 

The landuse pattern of the submergence area was ascertained using satellite 

and the details are outlined in Table-9.1. The landuse pattern as per the 

satellite data is appended as Figure-9.1. The satellite imagery (IRS 1D, LISS- 

III + PAN) of the study area is given as Figure-9.2. 

9.2.2 Ecological Aspects 

a) Vegetation 

Table-9.1 

Landuse pattern of the area to be 

acquired for the project 

S. 

No. 

Landuse / Land cover Area (ha) 

1. Dense forest 14.90 

2. Barren land 1.89 

3. Water bodies 8.17 

Total 24.96 

The proposed project site lies in western Himalayas. The nature and type of 

vegetation occurring in an area depends upon a combination of various 

factors including prevailing climatic conditions altitude, topography, slope, 

biotic factors, etc. 

The proposed project area lies between EL 2,600 m to EL 3,000 m and the 

vegetation in the area can be broadly categorised as Himalayan moist 

temperate forests. The project area lies in Patangani reserve forest. The 

9-3


major tree species observed in the area is Pine (Pinus roxburghii) and Deodar 

(Cedrus deodara). The other tree species observed in the area include Kail 

(Pinus wallichiana), Spruce (Picea smithiana), Bhojpatra (Betula utilis). The 

submergence area lies in Patangani Reserved Forest. 

In the study area elevation ranges from 3000 m to 4500 m. Dense forest is 

observed up to an elevation 3,600 m. However, at higher altitudes, dense 

vegetation gives way to Himalayan Dry Temperate Forest. The major tree 

species observed in these forests are Deodar and Kail. At even higher 

elevations, Moist Alpine scrub is observed. The tree species observed in 

these areas are Buransh (Rhododendrom arboreum), Junifer (Junifer sp.), 

etc. Amongst the shrubs, Barbaris, Lonisera, Pontitella species are observed. 

In the study area, downstream of the tail race disposal site, dense mixed 

forest is observed. The major tree species observed in this forest is deodar. 

The major floral species observed in the study area is given in Table-9.2. 

Table-9.2 

Major floral species observed in the study area 

Local Name Scientific Name 

Trees 

Deodar Cedrus Deodar 

Pine Pinus roxburghii 

Spruce Picea smithiana 

Bhojpatra Betula utilis 

Kail Pinus wallichiana 

Padam Prunus carasoides 

Buransh Rhododendrum arboreum 

Junifer Junifer sp. 

Kharsu Quercus semicarpifolia 

Morinda Abies pindrow 

Local Name Scientific Name 

Gugal 

Juniperus srumata 

9-4

Chiraita Swestia chirayita 

Bhatkunda Lonisera quinquelacularis 

Vazradanti Potentilla fulgens. 


b) Fauna 

As mentioned earlier, project area lies in reserve forest area. The forest in and 

around the diversion structure site is quite dense and serves as habitat for 

various faunal species. Based on the review of secondary data and interaction 

with the Forest Department, major faunal species observed in the project area 

and the study area include Bharal, Snow leopard, Barking deer, Wild goat and 

Wild cat. Apart from lizards, no major reptile species was observed in the 

area. Amongst the avi-fauna, the commonly observed species were vulture, 

parrot, dove, blue rock piegon, monal, etc. 

The list of faunal species observed in the study area including project area is 

outlined in Table-9.3. 

Table-9.3 

List of faunal species observed in the study area including project area 

Common Name Zoological Name Schedule as per 

Wildlife Protection 

Act 

Mammals 

Snow leopart Panthera uncia Schedule – I 

Goral Nemorhaedus goral Schedule – II 

Wild boar Sus scrofa 

Jungle Cat Felis chaus 

Wild goat Pseudois nayaur Schedule I 

Serrow Capricornis sunatrensis Schedule I 

Leopard Panthera pardus Schedule I 

Avi-fauna 

Vulture Gyps fulvus 

Indian Ringed dove Streptopelia decoacto 

Rufous Turtle dove Streptopelis orientalis 

Blue rock piegon Columba livia 

Reptiles 

Lizard Hemidactyles brooki 

9-5


It is observed, that quite a few species belonged to Schedule-I & Schedule II 

category. As per Wildlife Protection Act (1972), such species are akin to rare 

and endangered species and need to be protected. Thus, it is recommended 

detailed studies are conducted as a part of EIA study to ascertain impacts on 

such species, as a result of the proposed project. 

c) Fisheries 

The major water body in the project area is river Bhagirathi, which is a 

perennial river. Normally in such rivers several fish species are observed. The 

project area lies at an altitude of nearly 3,000 m. At this elevation, water 

temperature gets so low, that even cold water fisheries find it difficult to 

survive. Thus, at the diversion structure site large scale riverine fisheries are 

not expected. However, elevation at the proposed tail race disposal site is 

around 2600 m to 2700 m, where riverine fisheries could be present. 

Based on the interaction with the local Fisheries Department, fish species 

such as Brown trout and Mahaseer could be present in river Bhagirathi at the 

project site especially near power house site. It is recommended that a 

detailed fisheries survey be conducted in the river as a part of EIA study to 

ascertain the spatio-temporal occurrence of Mahaseer or other riverine fish 

species in the project area. Tank or pond fisheries are not observed in the 

project area and its surroundings. 

9.2.3 Socio-economic Aspects 

It is imperative to study socio-economic characteristics including demographic 

profile of the project area and the study area. The proposed project lies in 

tehsil Bhatwari of district Uttarkashi. The submergence area is likely to 

submerge forest area which comes under the Patangani reserve forest. 

9-6


The entire study area, too lies within tehsil Bhatwari of district Uttarkashi. 

Within the study area, only one village namely Gangotri is observed. As per 

1991 census, the average family size in the village Gangotri is about 2.5, with 

a total population of 240. Considering a decadal growth rate of 25 – 30%, the 

present population is around 300-310. The Scheduled Castes Population 

accounts for less than 4% of the total population. The literacy rate in the 

village is around 50%. There is vast difference in the male (95%) and female 

literacy rates (3.4%). 

9.3 PREDICTION OF IMPACTS 

Based on the project details and the baseline environmental status, potential 

impacts as a result of the construction and operation of the proposed project 

have been identified. As a part of IEE study, impacts on various aspects listed 

as below have been assessed: 

- Land environment 

- Water resources 

- Water quality 

- Terrestrial flora 

- Terrestrial fanna 

- Aquatic ecology 

- Noise environment 

- Ambient air quality 

- Socio-economic environment 

9.3.1 Impacts on Land Environment 

a) Construction phase 

Quarrying operations 

A hydroelectric project requires significant amount of construction material, 

which needs to be extracted from various quarry sites in and around the 

9-7


project area. Normally quarrying is done along the hill face, and generally left 

untreated after extraction of the required construction material. These sites 

can become permanent scar on the hill face and can become potential source 

of landslides. This aspect needs to be covered as a part of the EIA study and 

suitable measures for quarry site stabilization be recommended. It is 

recommended that the quarry sites be located over non-forest land. 

Operation of construction equipment 

During construction phase, various equipment will be brought to the site. 

These include crushers, batching plant, drillers, earth movers, rock bolters, 

etc. The siting of these construction equipment would require significant 

amount of space. Similarly, space will be required for workshop, storing of 

other construction equipment and materials, etc. In addition, land will also be 

temporarily acquired, for storage of the quarried material before crushing, 

rubble sand, crushed material, cement, spare parts yard, fuel storage, guard 

room, parking area for light and heavy vehicles, petrol, diesel pumps, 

temporary & permanent residential colonies for government and contractor’s 

labour, water supply and switch yard for construction purposes, etc. Various 

storage sites need to be earmarked for this purpose. The storage site should 

be selected in such a way that it leads to minimal impacts on human 

population, wildlife and vegetation in the area. Since, the proposed project 

sites lies in reserved forest, it is recommended that to the extent possible the 

above facilities be located over non-forest land to minimize the adverse 

impacts. 

Problems of muck disposal 

A large quantity of muck is expected to be generated as a result of tunneling 

operations, construction of access roads, etc. The muck so generated needs 

9-8


to be properly disposed otherwise it can lead to significant adverse impacts on 

environment. Normally muck is disposed along the river bank which ultimately 

finds it way into the water body, leading to adverse impacts on riverine 

ecology. 

The other option is to dispose muck over low lying areas. Efforts need to be 

made so that the site selected for muck disposal has minimum vegetation. 

After disposal of muck, the site needs to be stabilized using bio-engineering 

measures. Muck disposal sites need to be located over non-forest land. 

Specific site specific management measures can be suggested as a part of 

EIA study. 

Construction of roads 

The topography of the project area has steep to precipitous slopes which 

descends rapidly into narrow valleys. Construction of roads in such area can 

give rise to erosion hazards due to net downhill movement of soil aggregates, 

if adequate protection measures are not undertaken. The project construction 

would entail significant vehicular movement for transportation of large 

construction material, heavy construction equipment. Most of the roads in the 

project area, would require widening. Many new roads also shall be 

constructed. Construction of new roads may lead to removal of trees on 

slopes and re-working of the slopes in the immediate vicinity of road, which 

may lead to landslides, soil erosion, gully formation, etc. Adequate 

management measures need to be implemented to ameliorate such impacts. 

b) Operation phase 

The area coming under reservoir submergence is 24.96 ha (considering FRL 

as 2989 m). The entire land to be submerged lies in Patangani reserved 

9-9


forest. In addition to above, an area of 50-55 ha will be required for siting of 

project appurtenances, infrastructure, etc. The ownership category of such 

lands can be ascertained, once project layout is finalized as a part of DPR 

preparation. 

9.3.2 Impacts on Water Resources 

The construction of barrage as a part of the proposed project, diversion of 

discharge for hydropower generation would lead to reduction in flow for a river 

stretch downstream of the barrage site up to the confluence point of tail race 

discharge. Since there are no users in the intervening stretch, hence, 

reduction in flow in lean season and is unlikely to lead to any significant 

impact. However, reduction in flow is likely to have marginal impact on riverine 

ecology as the discharge during lean flow is significantly less, it is 

supplemented by intervening nallahs and streams do supplement the 

minimum flows in the intervening stretch . 

9.3.3 Impacts on Water Quality 


The project construction is likely to last for a period of 4-5 years apart from 

investigation stage. About 2000 workers and 500 technical staff are likely to 

work during project construction phase. The construction phase, also leads to 

mushrooming of various allied activities to meet the demands of the immigrant 

labour population in the project area. Thus, the total increase in labour 

population during construction phase is expected to be around 5000-6000. 

The total quantum of sewage generated is expected to be of the order of 0.4 

mld. The BOD load contributed by domestic sources will be about 270 kg/day. 

The sewage generally shall be disposed in nearby streams or channels under 

9-10


gravity through open drains, where ultimately it will find its way into river 

Bhagirathi. The inadequate sewage treatment and disposal facilities could 

lead to increased incidence of water-borne diseases. Thus, it is recommended 

to commission adequate sewage treatment facilities in the labour camps. 

Normally during construction phase, higher level of sewage treatment plants 

with secondary treatment facilities are not provided, as they are rendered 

useless, once the construction phase is over. Low cost sanitation systems are 

commissioned for treatment of sewage generated from labour camps. Similar 

sewage treatment measures are recommended during the construction phase 

of the proposed project as well. 

b) Operation phase 

Effluent from project colony 

In the operation phase, about 200 families will be residing in the area which 

would generate about 0.15 mld of sewage. The quantum of sewage 

generated is not expected to cause any significant adverse impact on riverine 

water quality. Adequate sewage treatment facilities including secondary 

treatment facilities need to be commissioned for this purpose to ameliorate 

whatever marginal impact that is expected to occur. 

Impacts on reservoir water quality 

The flooding of forest land in the submergence area increases the availability 

of nutrients resulting from decomposition of vegetative matter. Enrichment of 

impounded water with organic and inorganic nutrients at times become a 

major water quality problem immediately on commencement of the operation 

and is likely to continue in the initial years of operation. However, in case of 

Run-off-the-river schemes, the submerged area is negligible. The above 

9-11


referred impact is not expected to be significant. To ascertain the quantum of 

reduction in D.O. levels in initial years of reservoir operation, it is 

recommended that detailed modelling study be done as a part of EIA study. 

Eutrophication risks 

The fertilizer use in the project area is nil, hence, runoff at present does not 

contain significant amount of nutrients. During post-project phase too, use of 

fertilizers in the project catchment area is not expected to rise significantly. 

Thus, problems of eutrophication, which are primarily caused by enrichment 

of nutrients in water are not anticipated in the proposed project. 

9.3.4 Impacts on Terrestrial Flora 


Increased human interferences 

As mentioned earlier, about 2,500 technical staff, workers and other group of 

people are likely to congregate in the area during the project construction 

phase. The total increase in population is expected to be about 5000-6000. 

Workers and other population groups residing in the area may use fuel wood, 

if no alternate fuel is provided. On an average, the fuel wood requirements will 

be of the order of 2500-2700 m 3 . Thus, every year, fuel wood equivalent to 

about 800-900 trees will be cut, which implies that every year on an average 

about 1 ha of dense forest area will be cleared for meeting fuel wood 

requirements, if no alternate sources of fuel are provided. It is recommended 

that contractor involved in construction activities to either provide alternative 

source of fuel or run community kitchens, in which LPG or kerosene is used 

as fuel. 

9-12

) Operation Phase 

Acquisition of forest land 


About 14.9 ha of forest area, mainly under reservoir submergence needs to 

be acquired, which lies in reserved forest area. In addition to above about 50- 

55 ha land will also be required for siting of construction equipment, storage of 

construction material, muck disposal, widening of existing roads and 

construction of new project roads, infrastructure development, etc. In addition 

to compensatory afforestation, conservation plan, outlining measures for 

development of floral species in areas similar to the one being affected needs 

to be formulated. 

It is recommended that a detailed ecological survey be conducted as a part of 

EIA study to assess the density and diversity of flora in the area, based on 

which appropriate management measures can be formulated. 

9.3.5 Impacts on Terrestrial Fauna 

The forest area, in the project area and its surroundings provides habitat to 

various faunal species, quite a few which are categorised as Schedule-I or 

Schedule-II as per the Wildlife Protection Act (1972). The Wildlife Protection 

Act clearly lays specific guidelines for projection of Schedule-I & II faunal 

species. 

During construction phase, there will be considerable human interferences, 

and disturbance due to various construction and related activities. A detailed 

study needs to be conducted as a part of EIA study to assess the impacts on 

various faunal species due to such activities. Based on the findings of the 

survey, detailed management measures including surveillance need to be 

suggested to minimize the adverse impacts to the extent possible. 

9-13

) Operation phase 


During project operation phase, accessibility to the area will improve due to 

construction of roads, which in turn may increase human interference leading 

to adverse impacts on the terrestrial ecosystem. The increase in human 

population will not be much, hence, significant adverse impacts are not 

anticipated. 

Perusal of various faunal species observed in the project area, indicates that 

there are no migratory faunal species observed in the area. River Bhagirathi 

in the project area, even in the pre-project phase, acts as a barrier to wildlife 

movement. Thus construction of the reservoir as a part of the proposed 

project , is not expected to cause any additional barrier to wildlife movement 

in the project area. 

9.3.6 Impacts on Aquatic Ecology 


During construction of a river valley project, huge quantity of muck is 

generated at various construction sites, which if not properly disposed, 

invariably would flow down the river during heavy precipitation. Such condition 

can lead to adverse impacts on the development of aquatic life, which needs 

to be avoided. 

The increased labour population during construction phase, could lead to 

increased pressure on fish fauna, as a result of indiscriminate fishing by them. 

Adequate protection measures at sensitive locations, identified on the basis of 

fisheries survey in the EIA study need to be implemented. 

9-14

) Operation phase 


Amongst the aquatic animals, it is the fish life which would be most affected. 

Based on the literature review, large scale riverine fisheries are not 

anticipated at the proposed project site. However, in rivers flowing in setting 

similar to Bhagirathi, Mahaseer, a migratory fish species could be present in 

the project area. A detailed fisheries survey needs to be conducted to 

ascertain the severity of impacts on Mahaseer and other riverine fish species, 

as a result of the proposed project. 

9.3.7 Impacts on Noise Environment 

Increased noise level are anticipated only during project construction phase 

due to operation of various equipment, increased vehicular movement and 

blasting etc. The project area has dense vegetation, which will attenuate noise 

levels to a large extent. Since, there are no settlements close to the project 

site, no significant impact on human beings is anticipated. However increased 

noise level, especially blasting could scare away wildlife from the area. It has 

been observed during construction phase of similar projects, that wildlife 

migrates from such areas and returns after the cessation of construction 

activities. Similar phenomenon is expected in the proposed project site as 

well. It is recommended that a noise modelling study be conducted as a part 

of EIA study to assess the impacts as a result of increased noise level. 

9.3.8 Air Pollution 

Pollution due to fuel combustion in various equipment 

Normally, diesel is used in construction equipment. The major pollutant, which 

gets emitted as a result of diesel combustion, is SO2. The SPM emissions are 

9-15


minimal due to low ash content in diesel. Model studies conducted for various 

projects with similar level of fuel consumption indicate that the short-term 

increase in SO2, even assuming that all the equipment are operating at a 

common point, is quite low, i.e. of the order of less than 1µg/m 3 . Hence, no 

major impact is anticipated on this account. 

Emissions from various crushers 

The operation of the crusher during the construction phase is likely to 

generate fugitive emissions, which can move even up to 1 km along the 

predominant wind direction. During construction phase, one crusher each is 

likely to be commissioned at the diversion structure site and the power house 

site. During crushing operations, fugitive emissions comprising of the 

suspended particulate will be generated. Since, there are no major 

settlements close to the diversion structure site, no major adverse impacts on 

this account are anticipated. However, it is recommended that the labour 

camp be situated at least 1 km away from the construction sites and that too 

on the leeward side of the pre-dominant wind direction in the area. 

9.3.9 Impacts on Socio-Economic Environment 

a) Project construction phase 

The construction phase will last for about 4-5 years. Those who would migrate 

to this area are likely to come from various parts of the country mainly having 

different cultural, ethnic and social backgrounds. Due to longer residence of 

this population in one place, a new culture, having a distinct socio-economic 

similarity would develop which will have its own entity. It is recommended that 

the labour camps and project colonies and other infrastructure be located over 

non-forest area, so that not only the land requirements are minimal, but 

9-16


adverse impacts due to human interferences are reduced to the extent 

possible. 

b) Project operation phase 

The entire land to be acquired for reservoir submergence is forest land and no 

private land or homesteads are to be acquired. However, some of the land to 

be acquired for various project appurtenances, which are proposed to be 

located over non-forest land could entail acquisition of private land. A detailed 

R&R plan, if required could be formulated as a part of EIA study. 

9.4 SUMMARY OF IMPACTS AND EMP 

A summary of impacts and recommended management measures are 

summarized in Table-9.4. 

Table-9.4 

Summary of Impacts and suggested management measures 

S. 

No. 

Parameters Impact Management Measures 

1. Land Environment 

Construction • Soil erosion due to the • Proper treatment of 

phase 

extraction of 

quarry site and location 

construction material of such sites over non- 

from various quarry 

sites. 

forest area. 

• Efforts to be made to 

ensure that minimal 

forest land is acquired. 

• Temporary acquisition 

of land for siting of 

construction equipment 

& material, waste 

material, etc. 

• Generation of muck due 

to tunnelling operations 

& roads. 

• Disposal at designated 

sites and provision of 

suitable management 

measures including 

bio-engineering 

treatment measures 

9-17

S. 

No. 



Operation 

phase 

2. Water resources 

Operation 

phase 

3. Water quality 

Construction 

phase 

Operation 

phase 

• Acquisition of 14.9 ha of 

forest land. 

• River stretch from 

diversion structure site 

to tail race outfall will 

have reduced flow 

during lean season. 

• Moderation of 

hydrologic 

regime. 

• Water pollution due to 

disposal of sewage 

from labour colonies. 

• Disposal of sewage 

from project colony. 

• Eutrophication 

problems. 

4. Terrestrial flora 

5. Terrestrial fauna 

Construction • Disturbance to wildlife 

phase 

due to operation of 

various construction 

equipment. 

Operation 

phase 

• Disturbance to wildlife 

due to increased 

accessibility in the 

area. 

The site should be 

located over non-forest 

area. 

• Compensatory 

afforestation & 

formulation of 

Conservation plan 

• In case downstream 

nallahs do not 

contribute to lean 

flows, minimum flow 

will be released to 

maintain the riverine 

ecology. 

- 

• Provision of community 

toilets and septic tanks 

• Provision of adequate 

sewage treatment 

facilities 

• No major impact 

expected 

• Increased surveillance 

to ensure minimum 

human activity in the 

national park. 

- 

9-18

S. 

No. 



6. Aquatic Ecology 

Construction 

phase 

Operation 

phase 

7. Noise Environment 

8. Air Environment 

Construction 

phase 

• Marginal decrease in 

aquatic productivity due 

to increased turbidity 

and lesser light 

penetration. 

• Obstruction in the path 

of migratory fishes. 

• Proliferation of species 

adapted to the 

lacustrine environment. 

• Drying of river stretch 

downstream of dam up 

to tail race outfall 

• Increase in air pollution 

due to use of machinery 

and other civil activities. 

9. Socio-economic Environment 

Construction 

phase 

Operation 

phase 

• Increase in employment 

potential. 

• Increased power 

generation 

• Greater employment 

opportunities. 

• Marginal impact, hence 

no specific 

management 

measures are 

suggested. 

• Development of 

hatchery for artificial 

seed production and 

stocking of reservoir 

and the affected river 

stretch 

• Provision of release of 

minimum flow, in case 

downstream nallahs do 

not contribute 

significant flows 

• Provision of release of 

minimum flow 

• Cyclones will be 

provided in crushers 

operating at various 

construction sites. 

- 

- 

- 

9-19

9.5 CONCLUSIONS AND RECOMMENDATIONS 


The project lies in reserve forest area providing habitat to various wildlife 

species. The following aspects need to be studied in detail as a part of next 

phase of environmental studies: 

- Impacts due to siting of various project features requiring temporary 

and permanent land acquisition on flora and fauna in reserved forest 

area. 

- Impediment to migratory fish species as a result of construction of 

diversion structure 

- Proper stabilization of quarry and muck disposal sites 

- Management of pollution sources from labour camps 

9-20


CHAPTER –X 

INFRASTRUCTURE FACILITIES 


The Gangotri Hydroelectric project across the river Bhagirathi envisages 

construction of a 26 m high gravity dam (above river bed level), an intake with 

short tunnels to the under ground desilting basins, a 5.20 km long HRT, 

pressure shaft, an underground power house with an installed capacity of 55 

MW and a tail race tunnel. The gravity dam is located at a distance of about 

2.5 km before Gangotri shrine. The major infrastructure facilities needed are 

described in the following paragraphs. 

10.2 COMMUNICATIONS 

10.2.1 The nearest rail head available to the project is Rishikesh which is about 276 

km from the intake site. 

From Rishikesh upto Gangotri via Dunda, Uttarkashi and Bhaironghati a wide 

black topped road exists. From Bhaironghati to existing main road near 

Gangotri HE Power house Site a motorable road exists but this requires 

extensive improvement, widening and hill slope stability measure for carry 

construction machinery & equipment. From existing main road onwards up to 

intake site a new approach road is required to be constructed 

10.2.2 Roads in the Project Area 

Apart from improvement of existing Bhaironghati – Gangotri road, an 

approach road is required to be built to the proposed Dam site (3 km). 

10-1


Other permanent roads to be constructed include a road from existing main 

road to Power House (about 4 km),access tunnel, project colony, work adits, 

and other Power House Complex requirements like road to switch yard, 

Power House Colony etc. 

Construction roads are also required from intake / power house site to quarry 

sites, and plant and machinery workshops etc. 

Considering the existing road facilities, lengths of permanent and temporary 

roads that are needed will not be large. 

10.2.3 Railways 

The nearest railway station is Rishikesh on the broad gauge line. Railway 

siding for unloading heavy machineries and equipment is to be provided at 

Rishikesh. 

10.3 CONSTRUCTION POWER 

The power demand for the construction activities is estimated to be about 5 

MW taking capacity of electric driven equipment and lighting which are to 

work within the target time for consideration. The initial requirement in the first 

two years could be 2 MW and this subsequently has to be increased to 5 MW 

The power requirement can be met with by procuring the supply from 

Uttaranchal authorities. For making the power available at project site 

required 33/11 kV substation and alongwith new power lines about 8 km to 

route from Bhaironghathi is proposed. 

10-2


In addition to tapping grid supply, it is also proposed to provide supplemental 

power aggregating to 2 MW as a stand by in case of interruptions in grid 

supply. 

10.4 TELECOMMUNICATION 

To ensure efficient execution at various sites, adequate and reliable 

telecommunication network is necessary. An electronic private Automatic 

Exchange with a capacity of about 50 lines is proposed. 

A VHF system is also proposed to link project Head Quarters with clients 

head-quarters. 

Suitable number of mobile phones / walky talkies are also proposed. 

10.5 PROJECT COLONIES / BUILDINGS 

10.5.1 The main project colony is proposed near Gangotri about 5-6 km from intake 

site and 12 km from power location. Facilities such as school, post office, 

police station, market, primary health centre, fire fighting arrangement, 

canteen and recreation facility are already available at Gangotri town which is 

very near to intake Site. Administrative building and 30 family quarters and a 

hostel are also proposed. 

Two more small colonies one near dam site and another near Power House 

location are also to be built with other facilities. 

10-3

10.5.2 Contractor’s Colony and Labour Colony 


Contractors colonies and two or three labour colonies with all amenities are to 

be located at sites near the major works. 

10.6 WORKSHOPS STORES, FABRICATION YARDS AND MAGAZINES 

Workshops for maintaining the plant and equipment used for construction, 

stores for construction materials, hydro-mechanical and electro-mechanical 

equipments etc. will be built and maintained by the contractor. However, a 

small workshop is planned for repair and maintenance facilities of project 

transport vehicles and minimum essential equipment will be built by the client. 

Areas for fabrication yards for the hydro – mechanical equipment, viz the 

various gates and hoists, pressure tunnel liners, penstocks etc. will have to be 

identified near the work sites. 

Two explosive magazines one for the works at dam site and rock quarries and 

another for the underground works are to be built. 

10.7 WATER SUPPLY AND SANITATION 

For drinking purposes in the colony areas, suitable water treatment plants for 

treating water drawn from the river Bhagirathi will be used. For construction 

purposes, water directly pumped from the river and stored will be used. 

Suitable sanitation and sewerage treatment facilities will have to be made at all 

the project and labour colony areas. 

10-4


CHAPTER – XI 


CONSTRUCTION PLANNING & SCHEDULE 

The Gangotri H.E. Project is located in the higher altitudes of about EL 2965 

m in the Himalayas and within the region heavy snow is experienced. At 

Badrinath (IMD Station) located on the Alaknanda valley snow is experienced 

5 months from December to April. The climatic parameters vary considerably 

within the basin also as such the project area has a limited working season 

as regards surface works are concerned. A period of 24 months has been 

provided for preparation of field investigations, subsurface exploration as 

required for Detailed Project Report preparation including statutory clearance/ 

approvals. Thereafter 24 months’ have been provided for pre-construction 

activities of surveys, infrastructure facilities, construction power, decision on 

accounts of development funds / agencies for execution engineering design, 

approach roads, tender engineering etc. The construction phase includes all 

the pre construction activities. A construction period of 5 years has been 

considered based on location of the project in higher altitude and remoteness 

of the area. The initial 24 months period for DPR preparation could be 

optimised incase other potential projects on the basin are taken up 

simultaneously. 

11.2 CONSTRUCTION METHODOLOGY 

Gagotri H.E. Project is envisaged as Run-off-the-River scheme across the 

Bhagirathi river. Diurnal gross Storage of about 4.37 Mcum with live storage 

of 0.91 M cum shall be created by a dam and gates arrangements, a 

discharge of 18.19 cumecs flow is proposed to be diverted through a tunnel 

11-1


of 2.5 m dia, D-shaped and 5.2 Km long to the underground power house and 

thereafter tailrace tunnel leading the discharges back to the river. 

11.3 MATERIAL SOURCES 

During the site visit by the WAPCOS Team which included a geologist, 

reconnaissance visit reveal that sand is not available in the nearby area and 

has to be transported from down below or produced by crushing stones 

similarly coarse aggregate shall have to be crushed from the nearby quarry 

sites. 

11.4 CONTRACT PACKAGES 

The contracts packages shall be mainly in the following packages : 

a) Headworks including Hydro mechanical 

b) Intake, tunneling work including adits and desilting chambers. 

c) Power house, pressure shaft, surge shaft, tailrace tunnel. 

d) Hydro mechanical. 

e) Hydro Electrical 

The eligibility of the contractors shall have to be suitably fixed based on 

working experience under similar condition. The auxiliary works of river 

diversion, coffer dam, penstock fabrication shall be part of the civil works 

package. However, for basic site facilities storage sites for contractor, 

approach roads, construction equipment, testing laboratory, staff colony, field 

offices at power house and intake sites could be taken up departmentally to 

enhance the pace of work of the contractor and cost recovered from the 

contractor. The packages could be contracted earlier so that by the time civil 

contractors mobilize the site facilities are made available. 

11-2

11.5 SCHEDULE OF WORK 


As envisaged the underground works could progress and may not be 

hampered by restricted working season but with lower rate of progress. The 

surface work shall be limited to about 150 days in a year with 25 working days 

in a month and 8 working hours. For the subsurface works the seasonal 

effect will be felt on the progress of work due to low temperatures restricted 

and reduced supplies as such reduction of progress in snowy period is 

considered and about 200 days could be utilized. Two shift working is 

considered economical due to shortage of working season, but third shift 

could be planned based on progress of work and seasonal constraints. 

11.6 CONSTRUCTION ACTIVITIES 

After the financial terms for construction are decided, NIT for fixing the civil 

contractor can be invited within 6 months on ICB basis. 

a) Diversion of river 

As the river gorge is narrow a diversion tunnel on the right bank is 

proposed before construction of the dam. The diversion tunnel invert 

level is kept at minimum flow level and completed in first three 

months immediately after snowing period ends and before the river 

water starts rising due to rise of temperature from June onwards and 

the excavation of diversion tunnel will be carried out by conventional 

drilling and blasting method. After the next floods recede a masonry 

coffer dam shall be constructed in parts and foundation works in river 

bed level completed upto the planned block level before the next floods 

are allowed to over top the concrete block. After the dam and 

appartment works are completed the diversion tunnel shall be plugged. 

11-3


The river bed excavation shall be handled by 3.0 cum Hydraulic 

Excavator and Rear Dumpers (25t). 

b) The construction of the dam and appurtenant works shall be completed 

in 30 months period. 

c) Intake tunnel and Desilting Chamber 

The intake structure and the intake tunnel of 2.75 m dia D-shaped and 

the desilting chamber of size 110 m x 8.0 m x 9.0 m are planned to be 

excavated by Conventional method of drilling and blasting and will be 

completed in 24 months. 

d) Tunnelling 

The head race tunnel finished dia is 2.5 m, D-shaped and 5.2 Km long 

and the excavation will be approach to the underground power house 

from the existing highway is proposed to be constructed upto the 

power house adit and also going further to the surge shaft. One Adit 

each at power house and surge shaft shall be provided. As both the 

banks of the river are under dense mix Forest with Deodar trees as 

such no additional adit is proposed and approach roads to Surge shaft, 

Power House and intake structure shall be minimum from the existing 

highway. There shall be only two faces for working on the HRT and 

one face each from Surge shaft are proposed Tunnel excavation shall 

be based on conventional drilling and blasting and supported by ribs 

where essential and supporting the excavated rock face by shotcreting 

and bolting. A period of 39 months has been kept for tunnel and 42 

months for power house excavation and concreting. The pressure 

shaft and Surge shaft shall be excavated through Alimak Raise 

11-4


Climber. The construction schedule at PFR stage studies is given in 

the enclosed Plate 11-1. 

e) Power House 

The under ground Power house accommodates 1 x 55 MW units. The 

excavation of the power house cavern shall be by conventional drilling 

and blasting method deploying air track, jack hammers and mucking 

shall be through trolleys mounted on rails as the working space in the 

tunnel shall be limited. Approach to the power house cavern shall be 

from the highway on the right bank leading from Bhaironghati by a 

small additional approach road and access tunnel from the same bank. 

11-5


CHAPTER - XII 

COST ESTIMATE 


Gangotri H.E. Project is proposed as run of the river scheme on the river 

Bhagirathi to tap its hydropower potential. The diversion structure is located 

2.5 downstream of the Gangotri Shrine in district Uttarkashi. The project 

envisages to divert the water of Bhagirathi into water conductor system by 

means of a diversion dam 26 m high (above river bed level) across the river. 

The water conductor system comprises of an intake, underground desilting 

chambers followed by a 5.20 km long head race tunnel of 2.5 m diameter 

(D-shaped), a surge shaft of 6 m diameter, a pressure shaft to feed one unit 

of 55 MW housed in an underground power house. A 450 m long tail race 

tunnel discharges the water back into the river Bhagirathi just upstream of 

another proposed Bhaironghati H.E. scheme head works. 

12.2 ABSTRACT OF COSTS 

The Project is estimated to cost Rs. 211.64 Crore at June 2003 price level 

the break down of cost is given below : 

Item Estimated Cost 

(Rs. Crore) 

Civil Works 148.46 

Electrical Works 63.18 

Sub Total (Generation) 211.64 

The project estimate has been prepared on the basis of “ Guidelines for 

preparation of cost estimates for River Valley projects” published by Central 

Water Commission, New Delhi. The abstract of cost of civil works is 

12-1


enclosed as Annexure 12.1. The above cost does not include the cost of 

transmission. However cost of power evacuation for this project under 

construction has been arrived as Rs. 7.5 Crores. Cost of Electromechanical 

is enclosed as Annexure 12.2 

The estimate for civil & Hydro mechanical works have been prepared based 

on the as average rates for major items of works made available by CWC in 

the “guidelines for estimating the civil cost for the preparation of PFR”. 

The electro mechanical rates have been adopted on the basis of enquiry 

floated to various reputed manufactures / supplier. The rates are inclusive of 

excise duty & taxes. 

The phased programme of construction has been given in the relevant 

chapter with this report. 

Cost provisions for the various items mentioned below has been made on 

lump sum percentage basis of C-Works & J – Power Plant Civil Works for 

working out the total cost of project at pre - feasibility stage. 

S. 

Items Provisions of % of 

No. 

C-Works & J-Power Plant Civil 

Works 

1 A. Preliminary 2% 

2 K. Buildings 4% 

3 O. Miscellaneous 4% 

4 P. Maintenance 1% of (C+J+K+R) 

5 R. Communication 4% 

6 X. Environment & Ecology 2% 

7 Y. Losses on Stock 0.25% of C – Works, 

J - Power Plant - Civil Works, 

K- Building & R - Communication 

12-2

13.1 GENERAL 

CHAPTER – XIII 

ECONOMIC EVALUATION 


The economic and financial evaluation of the Gangotri H.E project have been 

carried out considering the standard guidelines issued by Central Electricity 

Authority and the norms laid down by the Central Electricity Regulatory 

Commission (CERC) for Hydro projects. 

13.2 PROJECT BENEFITS 

13.2.1 The scheme would afford on annual energy generation of 264.76 GWh in a 

90% dependable year. For assessing the tariff, design energy generation of 

256.64 GWh, calculated with 95% capacity availability in a 90% dependable 

year, has been adopted. The project would provide 55 MW of peaking 

capacity benefits. 

13.3 CAPITAL COST 

The project cost has been estimated at Rs. 211.64 Crores without IDC based 

on the criteria for “Adoption of Rates and Cost for preparation of PFRs of 

hydro-electric projects” issued by CEA and is as given below: 

1. Cost of civil works = Rs. 148.46 Crores 

2. Cost of Electrical/Mechanical works = Rs. 63.18 Crores 

Total = Rs.211.64 Crores 

13-1

13.4 MODE OF FINANCING 


The project is proposed to be financed with a debt equity ratio of 70:30. An 

interest rate of 10% on the loan component has been considered for the 

financial analysis of the project. The interest on the working capital is taken 

as 9.75%. 

13.5 PHASING OF EXPENDITURE 

The project is proposed to be completed in 5 years period in all respect with 

full benefit available after 5 years. The detailed year wise phasing of 

expenditure based upon the above construction programme for Civil & 

Electrical works is given in Annexure 13.1. 

13.6 FINANCIAL ANALYSIS 

13.6.1 BASIC AND NORMATIVE PARAMETERS 

The following basic parameters have been adopted for working out the 

financial analysis of the project. 

i) Estimated capital cost of Rs. 245.11 Crores considering the Interest 

during construction. 

ii) Annual energy generation of 264.76 GWh in 90% dependable year and 

Design energy of 256.64 GWh. 

iii) Operation & maintenance expenses (including insurance) @ 1.5% of 

the project cost in the first year with 5% escalation every year. 

iv) Depreciation @ 3.5 % has been considered on an average basis. 

v) Auxiliary consumption @ 0.7 % of the energy generated. 

vi) Transformation loss @ 0.5% of the energy generated. 

13-2


vii) Interest on working capital @ 9.75%. 

viii) Interest during construction has been worked out based upon the 

interest rates as mentioned above. The computations are given in 

Annexure 13.2 for present day capital cost. 

ix) Corporate tax @ 30%. 

x) Return on equity @ 16%. 

13.6.2 Assessment of Tariff 

Based upon the parameters given above, the sale rate of energy at bus bar 

has been computed in Annexure 13.3. The sale rate applicable in the first 

year and levellised tariff is indicated below. 

Tariff Period 

First Year 

13.7 CONCLUSION 

Levellised Tariff 

TABLE – 13.2 

Tariff 

(Rs./KWh) 

1.62 

1.42 

The sale rate of energy indicated above shows that the energy generated 

from the project is financially viable and economically attractive. 

13-3

GANGOTRI H.E. PROJECT 55 (1X55) MW - Ministry of Power

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