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PFR STUDIES OFCHHUNGER CHALHE PROJECT

CHAPTER I

EXECUTIVE SUMMARY

1.1 INTRODUCTION

The Chhunger Chal Hydroelectric Project located in Pithoragarh district of

Uttaranchal envisages utilization of the waters of the river Dhauliganga, a

tributary of Kali (Sarda), for power generation on a run of river type

development, harnessing a head of about 310 m.

The project with a proposed installation of 240 MW (2x120 MW) would affordan annual energy generation of 853.28 GWh in a 90% dependable year. The

tariff from the project at present day cost would be Rs. 0.92/KWh (levellised).

The diversion site is located at Latitude 30o 11 15 N; Longitude 80o 3430 E.

The dam site is approachable from Tankapur by road at a distance of 265

kms upto Khela and 35 kms from Khela by Kuchha road. The nearest rail

head is located at Tanakpur and nearest airport is located at Delhi.

1.2 SCOPE OF WORKS

The Chhunger Chal HE project envisages construction of:

a 78 m high Concrete Gravity diversion dam across river Dhauliganga

to provide a live storage of 1.49 M cum with FRL at 2780 m and MDDL

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a 81.0 m high 12 m dia surge shaft

400 m long, 4.6 m dia pressure shaft

an underground power house having an installation of 2 Vertical

Francis driven generating units of 120 MW each operating under a

rated head of 292.83 m; and

147 m long tail race tunnel to carry the power house releases back to

the river

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

D/C line to newly proposed 400/220 kV substation at Didi hat. The total

length of this line would be around 50 kms upto Didi hat.

1.3 HYDROLOGY

The river Dhauliganga drains a catchment area of about 840 sq. km at the

proposed dam site. The water availability for the project has been consideredon the basis of 10 daily discharge series at Pancheswar dam site for the

period 1962-92. The flow series for Chhunger Chal HE Project were derived

by carrying out runoff-runoff correlation between concurrent flows at Chirkila &

Pancheswar and subsequent reduction in proportion to the catchment area.

The computed inflow series worked out has been utilized for Power Potential

Studies. The design flood has been assessed as 4517.40 cumec.

1.4 POWER POTENTIAL STUDIES

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formulated for Catchment Area treatment, compensatory afforestation 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. 688.03 Crores including IDC at June,

2003 price levels. The preliminary cost estimate of the project has been

prepared as per guidelines of CEA / CWC. The break down of the cost

estimates is given below:

Civil Works : Rs. 366.20 Crores

Electro Mechanical Works : Rs. 213.22 Crores

Sub total : Rs. 579.42 Crores

Interest During construction: Rs. 108.61 Crores

Total (Generation) : Rs. 688.03 Crores

Transmission works : Rs. 37.50 Crores

Grand Total : Rs. 725.53 Crores

1.8 FINANCIAL ASPECTS

As indicated above, the Chhunger Chal HE project, with an estimated cost

(Generation only) of Rs. 688.03 Crores (including IDC of Rs. 108.61 crores)

and design energy of 845.12 GWh in a 90% dependable year is proposed to

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1.9 CONCLUSIONS

Chhunger Chal HE project involves simple civil works and could be completed

in 5 years and 9 months. The project would afford a design energy of

845.12 GWh in a 90% dependable year. The cost per MW installed work out

Rs. 2.41 Crores. The Preliminary Feasibility Report indicates that the scheme

merits consideration for taking up for Survey & Investigation and preparation

of DPR.

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PFR STUDIES OFCHHUNGUR CHALHE PROJECT

CHAPTER - II

BACKGROUND INFORMATION

2.1 GENERAL

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

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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 pose a serious challenge for 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 Requirement Availability Shortage(-)/Surplus (+)

%age

Chandigarh 1110 1108 (-) 2 0.2Delhi 19350 18741 (-)609 3.1Haryana 18138 17839 (-)299 1.6Himachal Pradesh 3293 3206 (+) 87 2.6Jammu & Kashmir 6635 5899 (-) 736 11.1

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

State Peak

Demand

Peak Met Shortage(-)/

Surplus (+)

%age

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

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

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

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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 entire capacity is from 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 the rising hydro power generation and improving efficiencies in

distribution of electricity, Uttaranchal hopes to offer energy at stable prices

for eco-friendly 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.

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

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i Tapovan Vishnugad (360

MW)

viii Karanprayag Dam (252 MW)

ii Bowala Nandprayag (132

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 Pala (520 MW) xii Chamgad Dam (400 MW)

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

vii Utyasu Dam (1000 MW)

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

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

that feasibility of the schemes 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 Chhunger Chal H.E. Project located in Pithoragarh

District, as detailed in the subsequent Chapters.

2.5.3 In view of the power scenario described above, the envisaged Chhunger Chal

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CHAPTER-III

PROJECT AREA

3.0 DHAULIGANGA RIVER BASIN

3.1 Dhauliganga river is the northernmost right bank tributary of river Kali and lies

entirely in the Pithoragarh district of Uttranchal state of India. The

Dhauliganga basin is bounded between latitude 290 55' - 30 0 35' N and

longitude 800 15' - 80 0 45' E. This is a glacial and snowfed river and

originates in the Lesser Himalayas from snow peaks at an elevation of 5,160

m and flows down as a small stream in a narrow valley, generally in NE SE

direction over a length of 85 km before joining the Kali river at an elevation of

approximate 1100.0 m. The average bed slope of the Dhauliganga river is

approximately 1 in 20 and can be termed as a fast flowing ferocious river.

The river valley is located in high mountain ranges on both banks over most of

its stretch. The river brings down a considerable amount of sediment load

particularly during snow-melt and flood season.

3.2 PROPOSED BASIN DEVELOPMENT

3.2.1 Currently under Execution

The available drop of about 2000 m from Bokang to the confluence of

Dhauliganga with Kali river was noticed and was under study by the UP

Irrigation Department since 1970 for utilsiation of its hydroelectric potential. A

proposal utilizing the combined flows of Dhauliganga and Goriganga was

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NHPC. This scheme is under execution by NHPC with a diversion dam nearChirkila village having an FRL at EL 1345.0 m. This following are the main

details of this project:

1 Reservoir level EL 1345.0 m

2 TWL EL 1034.1 m

3 Gross storage 6.2 M Cum

4 Dam height 56.0 m

5 Type of dam Rock fill

6 River bed level EL 1301.0 m

Installed capacity 4 x 65 MW

Energy Generation

(a) in 90% dependable year

(b) in 50% dependable year

1,187 Gwh

1, 354 Gwh

3.2.2 Future Development

The toposheets prepared by survey of India reveal that there is tremendous

scope of harnessing the hydro power potential available in upstream of

Dhauliganga Stage I HE project, under execution by NHPC, Central

Electricity Authority on their preliminary assessment in the Ranking studies

have identified the following projects with the FRLs & TWLs proposed by them

and as per WAPCOS investigation and studies:

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As per CEA As per WAPCOS

investigation

S.

No.

Name of Scheme

FRL

(m)

TWL

(m)

FRL

(m)

TWL

(m)

1 Bokang Bailing 3200 2840 3280 2780

2 Chhunger Chal 2800 2480 2780 2470

3 Sela Urthing 2480 2200 2470 2200

4 Urthing Sobala 2200 1620 N.A. N.A.

5 Sobala-Jhumrigaon 1620 1480 Dropped because of

Dhauliganga Stage II.

6 Dhauliganga Stage-

II

1597.0 1330.0

CEA has awarded the preparation of pre-feasibility Reports for schemes at Sl.

No. 1 to 5. Sobala Jhumrigaon (Sl. No. 5) has been dropped in

consultation with CEA because of the proposed Dhauliganga Stage II

downstream.

3.3 DESCRIPTION OF CHHUNGER CHAL H.E. PROJECT

Chhunger Chal H.E. Project upstream of the proposed Sela Urthing H.E.

Project will harness the hydro-power potential of the river between EL 2780 m

and EL 2470.0 m.

The project envisages the construction of a concrete gravity dam with

overflow spillway just downstream of confluence of Horba Yankti with

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gate of size 4.0 m x 4.0 m. The inflow into each intake is collected byindividual intake tunnel of 4.0 m dia and is led to respective desilting

chamber which is designed to flush out all silt particles of 0.20 mm size and

above. A control gate shaft is proposed at the end of the desilting chamber

for purposes of desilting the chamber, when required. The desilting chamber

is provided with silt flushing gate, so that silt laden water can be flushed out to

a silt flushing tunnel (steel lined to withstand erosion) which brings the silt

laden waters back to the river downstream of diversion structure.

The silt-free waters from the desilting chamber is led to a 3.545 Km long

5.5 m dia horse-shoe shaped Head Race tunnel. Since the length of water

conductor is more than 5 times the head, a surge shaft is proposed in thisscheme and the flow is then fed into a pressure shaft of 4.6 m dia (steel lined)

which bifurcates near the underground power house to feed 2 x 120 MW

Francis turbines.

The underground power house complex consists of 2 separate caverns, one

for the generating units and another for the transformers etc. Both the

caverns are inter-connected by bus bar tunnels and a tunnel for repair of

transformer. The power house cavern will have an installed capacity of 2 x

120 MW vertical Francis turbines. The transformer cavern will house

transformers and GIS system. A cable cum ventilation tunnel has been

proposed for connection to a small out door switchyard. The power houseand transformer cavern will be approached from a road proposed outside by

means of a common 7.0 m dia D-shaped main access tunnel.

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3.4 SOCIO ECONOMIC PROFILE

The entire region has undulating topography with lofty mountains jutting out

that create a 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 landscape. Out

migration of able bodied persons is common. Subsistence level agriculture

based economy mostly prevails with marginal holdings. The infrastructural

development becomes very costly in such terrain.

Pithoragarh District has an area of 17.3% and supports 9.55% population as

compared to the state. The density of population is about 64 persons persq.km as against 116 persons per sq.km of the state. The literacy rate both

among males and females is lowest in the district standing at 59.0% and

38.37% as against the state average of 59.6% and 42.9% respectively. The

population of schedule castes is about 20.45% against state average of

16.7%.

The main work force, about 75%, is engaged in primary and secondary

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

70% of land is under forest and barren lands.

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

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CHAPTER-IV

TOPOGRAPHIC AND GEOTECHNICAL ASPECTS

4.1 INTRODUCTION

The proposed Chhunger Chal hydro-electric project on Dhauliganga river

( Lat. 300 11 15 N ; Long. 800 34 30 E) envisages construction of a 78 m

high concrete gravity dam downstream of the confluence of Horba Yankti with

Dhauliganga and about 1.3 km upstream of Chal village situated on the right

bank of the river. An underground power house with an installed

capacity of 240 MW(2 x 120 MW) is located inside the right bank hill

about 1 km upstream of Sela village. The other main components of the

project include a 3.545 Km long HRT, a Surge Shaft and a pressure shaft

etc.

4.2 PHYSIOGRAPHY

The area around the project is located in the inner part of lesser Himnalayas

and outer part of Great Central Himalayas. It represents an extremely rugged

topography with very high relief. The area is drained by a number of

streams (gads / Yanktis) which are tributaries of south-southeasterly flowing

river Dhauliganga which itself is a tributary of Kali river.

4.3 RAINFALL AND CLIMATE

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Munsyari is the nearest rainage station to the project area. The rainfall dataat Munsyari (El 2100.0 m) indicates that main months of rainy season

are July, August and September. The total monthly precipitation/rainfall

data of the years 19867-1988 for Munsyari raingauge station is given

below:-

Total Monthly Rainfall/Precipitation in mm

Year Jan Feb March April May June July Aug. Sept. Oct. Nov. Dec.

1986 NA NA NA NA NA 153.0 566.0 618.0 239.4 110.3 16.1 10.2

1987 52.6 35.0 5.3 70.8 173.8 87.2 751.6 858.8 278.8 65.0 0.0 55.2

1988 35.6 164.8 307.0 51.6 NA 384.2 NA 807.6 268.0 NA 32.4 148.0

The area witnesses cold temperate climate during summer and the winters

are cold with occasional snow falls in the project area.

4.4 REGIONAL GEOLOGICAL SETUP

The rocks occuring at and in the vicinity of the proposed dam site are

porphyroblastic gneisses and schists which are included in the Central

Himalayan Crystalline. The region is bounded by two major planes of

dislocations, the Main Central Thrust in the south while the Dar Martoli

Fault marks its northern limit with the rocks of the Tethyan Zone. The Main

Central Thrust is an important structural discontinuity in the area which

separates the rocks of the Garhwal group from those of central

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The Dar Martoli Fault demarcates the boundary between CentralHimalayan Crystallines and rocks of Tethyan Zone i.e. Budhi schists etc.

The regional trend of the fault is WNW ESE with high angle dip

towards North and is located far away from the project area.

4.5 GEO-TECHNICAL APPRAISAL

4.5.1 General

The geologic map of the area shows that the proposed project site is located

in the area which exposes the rocks belonging to Bogudiyar formation and the

lower and Middle Members of Dar Formation. These comprise garnetiferous,sillimainte and kyanite bearing schists, quartzite and various types of

gneisses. These rocks trend in WNN-ESE in general with moderate dips

towards north. The rocks are highly deformed and are folded and faulted.

The geological map of the Project Area is given at Plate I.

4.5.2 Geology at Dam Site

The site is proposed diversion structure is located across Goriganga near

Mapang village. The area exposes 3f Member of Bogudiyar Formation. The

rocks include garnetiferous mica schist, biotite schist, slate, quartzite and

phyllite. The over burden in the river is expected to be thick and needs to beascertained during detailed investigations.

4.5.3 Geology along Water Conductor System

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include biotite schist, gneisses, micaceous quartzite, calsilicate rock withbands of biotite schist and gneisses, quartzite with igneous intrusions,

quartzite, gneisses, biotite gneisses, (kyanite bearing) with bands of

micaceous quartzite. These rocks are traversed by ENE-WSW to E-W

trending fault likely to be intersected by the proposed HRT alignment. The

tunneling conditions are expected to be fair to good in general except for

reaches where shear/fault zones are encountered. Adequate rock cover has

to be ensured at drainage crossings. The surge shaft and pressure shaft will

also pass through the similar strata except that near the top the surge shaft

may open up in weak and disintegerated rock strata. Similarly the tailrace

tunnel near the outlet may encounter distintegerated rocks.

4.5.4 Geology at Underground Power House Site

The underground power house is located sufficiently inside the left bank

where, like water conductor system, rocks to be encountered are biotite

schist, gneisses, micaceous quartzite, calsilicate rock with bands of biotite

schist and gneisses, quartzite with igneous intrusions belonging to member 3c

of Bogudiyar formation.

4.6 SEISMICITY OF THE AREA

The area encompassed by the project falls in Zone V of the SeismicZoning Map of India (IS : 1893 1984 ). Clusters of epicentres of

medium to shallow earthquakes with magnitudes ranging between 5 and

6.5 are shown on the map of India (Appendix A of the Indian Standard

ti d b ) i d d th d j t Thi f t

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The Bajang (Nepal)- Dharchula earthquake (M = 6.1), which occurred on29th July 1980 had its epicentral tract in Dharchula area. A maximum

intensity of VIII was assigned to the earthquake. Therefore, a suitable

seismic factor would have to be adopted for designing the structures in

the area.

4.7 CONSTRUCTION MATERIAL

The river bed material may be sorted, crushed and utilised for construction

purposes. In addition, the excavated rocks from underground works may be

tested and used for construction. No clay or impervious materials are

available for a rock fill type dam having impervious core.

4.8 LUSIONS AND RECOMMENDATIONS

i) The rocks exposed at the proposed dam site are porphyroblastic

augen gneisses and chlorite schist belonging to Central

Himalayan Crystalline group.

ii) The overburden in the river section at site will have to be ascertained

with the help of geophysical surveys and further confirmed by drilling

during DPR stage.

iii) Large scale control plans shall have to be prepared for taking up the

detailed geological mapping of the proposed sites and forsuggesting sub-surface explorations at the detailed project report

stage.

iv) The project area falls in Zone V of the seismic zoning map of India,

h it bl i i f t ill h t b id d i th d i

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CHAPTER V

HYDROLOGY

5.1 WATER AVAILABILITY STUDIES

5.1.1 Catchment Area and River

The proposed Chhunger Chal dam site is located on the river Dhauliganga

which is located in Sarda Basin. The catchment area contains several

glaciers and permanent ice caps and the seasonal snow cover area in the

catchment is about 305.25 sq. km. The total catchment area of the riverMahakali upto Chhunger Chal is 840 sq. km. The catchment area map of

Chhunger Chal is shown as Plate-5.1

The elevation in the catchment ranges from 6000 m in the upper

reaches to around 2700 m near the dam site.

5.1.2 Data Availability

(a) Rainfall

There are no Raingauge / G & D stations established on the Mahakali

river The rainfall data in the Dhauliganga basin has been measured at

three raingauge stations by NHPC as given under in Table 5.1.

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Table 5.1Daily Rainfall data availability

Sl.

No.

Name of rainguage station Duration

1 Chirkila June 83 to Dec. 2002 with gaps

2 Nyu Jun.. 74 to Aug 80, Jan 84 toMay 89, July 89 to Dec 96,Jan 1999 to Dec 2002 withgaps.

3 Dugtu Jan 77 to Dec91 with severalgaps

The average annual basin rainfall is estimated as 2500 mm. Due to

intermittently missing rainfall data and its non-availability for later yearsit has not been possible to use the same for water availability studies in

the present studies.

(b) Gauge and Discharge Data

The discharge data observed by NHPC, CWC is available at three G

& D sites. The details are presented in Table-. 5.2 below:

Table 5.2

Gauge and Discharge data

Sl.No.

G & D Site Data availability

1 Chirkila Jan 85 to Dec 96, May.. 97 to Aug

2000, Oct 2000 to Jan 2001

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(c) Sediment Data

The sediment data at Chirkila G & D site is available for the period

Jan 1985 to Dec. 1996, Jan 1997 to Apr. 98 & Nov98 to Dec. 2002

5.1.3 Methodology

The Mean Monthly flows of river Mahakali at Pancheswar (CA 12100 sq. km.)

are available for the period 1962 1992 (31 years). The G&D data observed

by CWC at Tawaghat (C. A : 1372 Km) -which is 5.5 Km downstream of

Chirkila ( C.A: 1360 Km ) is available from 1977 to 1984. This series is

transposed to Chirkila site (located on Dhauliganga river, which is adjacent toMaha Kali) in proportion to catchment area.

In the absence of site specific flow data this 10-daily series at Chirkila has

been used as base data for extension of data series on catchment area

proportion basis. Hence using Pancheswar runoff data as base, the flows

series for Chirkila is extended by trying both linear and non linear runoff

runoff correlation on monthly basis. The regression equations are developed

between Pancheswar runoff series and Chirkila runoff series for concurrent 8

years flow data for the period 1977-84. Three different correlations between

the monthly flows have been established for three distinct periods of the year

as shown below keeping view of the predominant factor generating the runoff.

Finally these generated series are transposed to Chhunger Chal (C.A 840

Km2) on area proportion basis. The Pancheswar and Chirkila monthly flow

series are detailed in the Hydrology report Vol -III.

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(Snow melt phenomenon being causative factor of generation ofrunoff).

The correlation equations for the above mentioned periods for Chhunger Chal

are as follows:

(a) Monsoon Period (June to September)

(i) Non linear correlation equation

y = 5.3862 x 0.4713 (r = 0.824)

x = Monthly runoff in Cumecs for monsoon month atPancheswar

y = Monthly runoff in Cumecs at Chirkila

r = correlation coefficient

(b) Non monsoon period (October to February)

(i) Non linear correlation equation

y = 0.5345x0.7476

(y = 0.84)

(c) Snowmelt Period (March to May)

(i) Linear correlation equation

y = 0.195x - 1.804 (r = 0.889)

M thl ff f lt i d i C t

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1992. Thus a long term flow series from 1962 1992 at Chirkila hasbeen established.

The ratios between 10-daily flows & corresponding monthly flows have

been calculated . Accordingly, the monthly flow series for the extended

periods have been converted to 10-daily flow series.(calculation details

given in Hydrology report Vol III). The 10 daily flow series at Chirkila

has been transposed to Changer Chal in proportion of catchment area.

The integrated 10-daily flow series along with 50% and 90%

dependable year has been presented in Table 5.3 and have been

adopted for planning purpose. The 90% and 50% dependable year

correspond to 1967 and 1991 respectively.

5.1.4 Comparison of flow data between Tawaghat & Chirkila

Central Water Commission is maintaining G & D site on Dhauliganga river at

Tawaghat very close to Chirkila. A comparative statement of annual flows has

been prepared from 1981 to 1992 between the flows at Chirkila from NHPC

data and flows at Tawaghat with CWC data (ref. Hydrology Report Vol III).

It is observed that the annual observed flows of Tawaghat site downstream of

Chirkila based on CWC data are generally on the higher side. Therefore, the

flow series evolved based on NHPC data is on conservative side and appears

reasonable to be adopted for planning purpose.

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5.2 DESIGN FLOOD STUDIES

5.2.1 General

The design flood and highest flood level are very much essential for fixing the

water way and foundation depths of any hydraulic structure. For a diversion

structure, 100-year design flood or standard project flood value is considered

for hydraulic design and for storage projects, probable maximum flood or

1000 year return period flood should be considered based on following

methods.

(i) Hydro-meteorological approach (unit hydrograph method).

(ii) Flood frequency analysis.

5.2.2 Derivation of Unit Hydrograph

CWC in association with IMD and MOST has prepared Flood Estimation

Reports for small and medium catchments for efficient hydro meteorological

homogenous sub-zones. The present studies are based on CWCs Flood

Estimation Report for Western Himalayas Zone 7

The formulae for calculation of various physiographic parameters are given in

Table 5.4.

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Table 5.4Physiographic Parameter Calculations

Parameters Formulae Value

tp2.498

156.0

c

S

L.L

4.132 hrs.

qp 1.048 ( ) 178.0pt

0.81 cumec/sq. km.

W501.954

099.0

c

S

L.L

2.68 hrs.

W750.972

124.0

c

S

L.L

1.45 hrs.

WR50 0.189 ( ) 769.150W 1.087 hrs.

WR75 0.419 ( ) 246.175W 0.66 hrs.

TB 7.845 ( ) 453.0pt 14.92 hrs.QP qp.A 435.35cumecs

Where Tm = 63.42

113.4

2

tt rp =+=+ hrs.

The nomenclatures of the above parameters are the standard representation

of the values and detailed in Hydrology Report Vol.-III.

For the present study with a total catchment area of 840 sq. km, an area of

534.75 sq. km. is considered for the study as 305.25 sq. km. of the

catchment area is under snow and glacier cover (above 5000 m). The total

length of Mahakali river upto Chhunger Chal is 51.74 km. For the catchmentof Chhunger Chal, the value of Lc is 22.78 km. The equivalent slope of the

project area is 1 in 47.

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available, the same point value has been adopted for the present study

purpose. The 25 year, 50 year and 100 return period precipitation

values (12cm, 14 cm & 15 cm respectively) are adopted from the

Isohyetal Maps.

b) Design Storm Duration The base period is of 15 hours, hence one

day design storm is considered.

c) Point to Areal Rainfall Ratios For 25 year, 50 year and 100 year

return period precipitation an areal reduction factor of 0.9113

corresponding to rainfed CA of 534.75 sq. km. is adopted The PMP

value of 33.41 cm considered for the study is an point value.

d) Clock Hour Correction A clock hour correction value of 1.15 is

adopted for PMF study for converting 1 day rainfall to 24 hr rainfall.

However the increase in one day value is limited to 50 mm.

e) Time Distribution Coefficients The Time Distribution Coefficients for

24 hours is given below:

Table 5.5

Distribution Coefficients

Time in

hours

Distribution

coefficient

Time in hours Distribution

coefficient

1 0.17 13 0.792 0.27 14 0.823 0.36 15 0.844 0.43 16 0.865 0.48 17 0.88

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f) Design Loss RateA design loss rate of 0.5 cm/hr. has been adopted.

g) Design Base Flow and Glacial MeltA base flow rate of 0.05 cumecs

/ sq. km. has been adopted. In addition a glacier melt runoff value of 50

cumecs has also been considered tentatively, keeping view of existing

number of glaciers at the upper catchment boundary.

h) Critical Sequence of Rainfall Excess The critical sequence of rainfall

excesses are based on rainfall increments into design hyetograph

arranged in the form of two bell (12 hours each per day).

5.2.4 Computation of Unit Hydrograph

Using the basic physiographic parameters, the unit hydrograph is plotted and

volume adjusted to 1 cm. With out changing the QP, Tm and TB . The surface

flow total flood hydrograph has been computed after the rainfall excess

increment arranged in a critical sequence along with additional component of

base flow and glacier melt.

The detailed calculations showing computation of equivalent slope,

physiographic parameters, rainfall excess, convolution and the flood ordinates

for PMP, 100 year, 50 year and 25 year return period for Chhunger Chal are

given in the Hydrology Report Volume-III.

A PMF value of 4517.40 cumec has been adopted for purpose of preliminary

project planning. The hydrograph showing peak flood for PMF, 100 year, 50

d 25 fl d i i i T bl 5 6 d l t d i Pl t 5 2

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Table 5.6

Chhungar Chal - Flood Ordinates

Return period Design floodpeak in cumecs

Remarks

25 year 972.6650 year 1235.72

100 year 1368.471000 year 4400.00 Projected from 25 year, 50 year& 100 year flood peaks usingGumbel probability papers.

PMF 4517.39

5.3 FLOOD FREQUENCY ANALYSIS

Flood frequency analysis provides a quick estimate of the design flood and is

also useful for checking the design flood values computed by other methods.

It is carried out in two methods viz The Annual Maximum method and the

Peak over Threshold (POT) method (also known as partial duration method).

The long term annual instantaneous peak flow series at project site is not

available. As such the 32-year annual peak discharge series of Pancheswar

dam site has been used for frequency analysis. The results obtained will be

transposed to Chhunger Chal site with due correlation for the variation of

catchment size. The available data will be subjected to randomness clock

stationary test, outlier test. Extreme value distribution also known as Gumbel

distribution and Log Pearson Type III distribution are used for the present

study. Chi square test for LPT-III distribution and Gumbel distribution is used

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Pancheswar are transposed to Garjia dam site using Dickens formula Q =

CA 3/4. The 10,000 year flood value for Pancheswar is 15041.36. Using this

relation, the 10000 year flood at Chhunger Chal is found to be 2034.26

cumecs.

5.4 RESERVOIR SEDIMENTATION STUDIES

5.4.1 General

The suspended sediment inflow data is available at Chirkila G&D site near

project site from January '1985 to 15 December '1996 observed by M/s

NHPC. The observations have been taken by Punjab Type Bottle Sampler

with grain size classification of coarse (greater than 0.2 mm), medium (0.025

mm to 0.2 mm) and fine (less than 0.075 mm).

The bed gradient of river (Maha kali) Dhauli ganga is steep ( 1in 47 upto

project site) and the river is also fed from mountaineous catchment with a

number of glaciers which bring down considerable sediment load during snow

melt and flood season.

There is no Sediment data available for river Mahakali. Hence the Sediment

Data of adjacent Dhauliganga and Goriganga basins have been taken into

account for computing sediment inflow rate. The sediment inflow estimate for

Dhauliganga catchment (which is based on 10 years of data ) is 0.14 ha m /

100 sq. km. / year including 15% bed load which was agreed upon by CWC

while clearing Dhauliganga reservoir sedimentation studies. This estimate is

bl ith dj t G i b i di t i fl f 0 15 h /100

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Technology is 1.65 mm/year for Himalayan rivers. As such the silt rate of

Pancheswar appears higher and more emphasis should be given towards

project specific observation data.

Since the above average annual rates are based on comparative shorter time

horizon an additional load of 15% is added for the adopted silt rate as to

make the silt rate representing a long time average. Hence a silt rate of

0.1725 ha-m / 100 sq. km./year (0.15 x 1.15) has been adopted for

sedimentation studies of Chhunger Chal Barrage.

5.4.2 Sedimentation Aspects

It is observed from the topo sheets that both Dhauliganga and Kali the

catchments contain number of glaciers in the upper reaches at higher

elevation in beyond the proposed scheme Bokang Bailing. There are few

reserved forests, dense mixed jungles of tansen , banj, deodar etc. open

scrubs, rockfall sites and moraine deposits carried by glaciers at relatively

lower stages near its confluence with the Kali. Major catchment area contains

bare rocks with little or no soil cover. The average annual sediment rate for

Chhunger Chal has been estimated to be 1.725 mm based on observed

sediment data of Goriganga at Tham for 5 years and of Dhauliganga at

Chirkila for 10 years. The break up of suspended sediment particles for the

month of August 1988 (severe monsoon month) based on observed data at

Chirkila on the Dhauliganga is coarse 24.76%, medium 17.37% and fine

57.89%.

It i i t t t t th t Hi l t h di t

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river bed level is expected to be fully encroached by the rolling bed load of

pebbles, boulders etc. within one or two years and the entire rolling bed load

would pass over the crest. This warrants proper protection measures against

the damage of downstream glacis.

5.5 CONCLUSION & RECOMMENDATION

(1) The 10-daily flow series of 31 years developed and extended tentatively on

the basis of runoff-runoff correlation with Pancheswar flows may be adopted

for preliminary project planning. However, the flow series need to be reviewed

when site specific observed flow series of longer periods would become

available from the observation agencies. Continuation of all hydro-

meteorological observation in the existing stations may be assured and

identification of new station may be under taken at DPR stage. A gauge,

discharge and silt observation site at/near Chhunger Chal barrage site should

be immediately installed on scientific basis.

(2) It is suggested that short interval rainfall-runoff observation should be initiated

at the project site to enable derivation of reliable unit hydrograph from

observed data. Similarly detailed storm studies are needed to be carried out

preferably by IMD in order to obtain reliable estimate of PMS at highly

orographic catchment with snow & glacier covers.

(3) The sediment rate adopted is based on observed suspended sediment data at

Dhauliganga and neighbouring Goriganga rivers for about 10 years only. The

bed load assumed to be 15% of suspended load is quite tentative. Therefore,

th di t t d t b i d ith d t d b d d t f l

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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 1.2 respectively.

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CHAPTER-VI

CONCEPTUAL LAYOUT AND PLANNING

6.1 INTRODUCTION

The Chhunger Chal HE project is the second uppermost scheme in the

cascade development of Dhauliganga basin. This project is proposed

downstream of the proposed Bokang Bailing HE Project.

The Chhunger Chal hydro-electric project as planned envisages

construction of a 78 m high concrete gravity dam above the deepest

foundation level across the river Dhauliganga, downstream of confluence of

Horba Yankti with Dhauliganga river and about 1.3 km upstream of Chal

village. The water from the diversion dam will be led to an underground power

house located about 5 km downstream of dam site inside the right bank hills,

through a 3.545 km long head race tunnel, and a pressure shaft. The power

house is planned to have an installed capacity of 240 MW (2 x 120 MW)utilising a rated head of 292.83 m. The tail waters from the power house will

rejoin the river Dhauliganga through a tail race tunnel.

Central Electricity Authority in its planning for this project had envisaged a

diversion structure near Chhunger with FRL at 2800m, a 4 km long power

tunnel aligned on the right bank of the river with Power house located near

Chal with TWL 2480m. After detailed studies, a dam site downstream of the

confluence of Horba Yankti and about 1.3 km upstream of village Chal has

been selected where the river bed level is at about EL 2720 m The river

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The intake and a 3.545 km long HRT are planned on the right flank of the river

and the underground power house inside the right flank hill. The minimum

TWL at the power house is 2470 m which corresponds to FRL of the planned

sela Urthing H.E. project.

With the above changes in the location of dam, power house, TRT etc. and

the layout of the scheme including dam height, tail race and other features;

the potential of the project has been enhanced to 240 MW as against 145 MW

suggested by CEA.

The location of the dam and its height have been finalised considering

optimum power generation, topographical and geotechnical features, already

planned projects on the upstream and downstream, economy, submergence

and other relevant factors. The site is considered ideally suited for the

construction of a concrete gravity dam. Embankment type of dam was not

considered in view of non-availability of impervious materials and spillway

considerations.

The dam is 192 m long at the top and consists of overflow and non-overflow

blocks. The overflow blocks are designed as ogee control structures with a

crest level of 2759m and 21 m high radial gates. The FRL and MWL of the

dam are at EL 2780m and the top of dam is kept at EL 2783 m after allowing

for necessary freeboard. The MDDL is kept at EL 2769 m which will provide

the required peaking storage against the gates during the lean months and

also meet the requirement of power intake.

Th i t k HRT h ft d h ft l t d i it bl k

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The salient features of the project are included in the report. The details of the

major components of the project alongwith the design considerations are

given in subsequent paragraphs.

6.2 DIVERSION STRUCTURE

A 78 m high (above deepest foundation level) concrete gravity dam is

proposed downstream of the confluence of Horba Yankti with Dhauliganga

and 1.3 km upstream of village Chal on Dhauliganga river. The dam is

proposed at latitude 30o 1115 N and longitude 80o 3430 E. The concrete

dam will have FRL of 2780 m and MDDL of 2769 m. The MWL of the dam is

2780m and the top of the dam is kept at EL 2783 m after taking into account

the required freeboard.

The proposed dam will have a submergence area of 1,32,000 sq. m at FRL

(Refer Annexure-6.1) and all this area will be within the river gorge. The

reservoir storage for peaking purposes in the lean season between MDDL

and FRL is 1.49 M. Cum (Refer Annexure 6.2).

Overflow type of spillway blocks, two in number, with ogee control structures

have been planned to pass the design flood discharge of 4517.40 cumec.

For the spillway, ski jump bucket energy dissipators have been planned as

terminal structures with concrete apron protection beyond spillway bucket.

The dam will have seven number NOF blocks and two number overflow

blocks. The pier width for the spillways has been kept as 5 m. The choice of

ski jump energy dissipation works for this dam has been dictated by the tail

t diti A th i di t i it t tilli b i

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treatment measure, consolidation grouting throughout the entire base of the

dam to a depth of 10 m and one row of curtain grouting to a depth of h/2

where h is the height between FRL and deepest foundation level subject to a

minimum depth of 10 m have been provided. A grouting cum drainage

gallery has been provided at the bottom of the dam, through which the curtain

grouting as well as drainage hole works will be done.

All the hydraulic and structural designs for the dam, spillway and other

components of the dam have been done as per relevant BIS codes /

standards and the State of the art practices. The dam sections will also be

zoned with different grades of concrete in order to economise the cost without

sacrificing the stability and safety requirements.

The dam and underground power house will also be provided with measuring

devices as per BIS codes to observe and monitor the behaviour of these

structures.

The layout plan of the dam and other components of the project are shown in

drawing no. WAP/PFR/CHHUNGER CHAL/1001. The dam plan and elevation

are shown in drawing no. WAP/PFR/CHHUNGER CHAL/1003 and sectional

details of NOF and overflow blocks are shown in drawing no.

WAP/PFR/CHHUNGER CHAL/1004.

6.3 POWER INTAKE

The intake structure for diverting the design discharge of 114.0 cumec

(i l di ilt fl hi i t) i d th i ht b k f i

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The required flows for power generation are proposed to be diverted through

two intake structures of capacity 57.0 cumec with crest at EL. 2759 m. The

intake trashracks will have 5 spans of 5 m each separated by 4 no. piers of

1.5 m width each at center to center distance of 6.5 m. The total width of the

trashrack structure will, therefore, be 67 m. The trashracks will be in panels of

size 5 m x 0.75 m which can be easily lowered in inclined trashrack grooves.

The racks will be made out of steel flats of size 15 mm x 50 mm rounded at

inlet ends and shall be fixed vertically on each of these panels at a spacing of

100 mm c/c. Assuming 50% clogging, the velocity through the trashracks will

be restricted to 0.75 m/s.

The flow through the intake will be led to an intake tunnel with a bell mouth

entry. The vertical lift gate of size 4.0m x 4.0m will control the flow into the

intake tunnel. Stop Log has also been provided for the intake. For operation

of gates, a gate hoisting structure will be provided at EL. 2783 m. A vent

pipe of 200 mm diameter would also be provided just downstream of the

intake gate. Besides intake gate hoisting structure at EL 2783 m, a deck has

also been proposed at EL 2770 m to install / clear the trashracks when

reservoir level reaches MDDL. The details of intake structure are shown in

Drawing No. WAP/PFR/CHHUNGER CHAL/1005. The hill slope near each

intake will be stabilized with adequate slope protection measures like rock

bolts, shotcrete, benching, drainage holes etc. as necessary.

6.4 INTAKE TUNNEL

Two number intake tunnels have been proposed, one each for the two

i d d t i t k t t E h f th t l i d i d t

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a surge shaft. The length of each intake tunnel will vary to suit the merger

point with the headrace tunnel. To excavate these tunnels, rock support

system shall be provided to suit the geological conditions of the strata through

which these are excavated. The intake tunnels will be provided with 200 mm

thick PCC lining.

6.5 DESILTING CHAMBERS

It is proposed to provide desilting chambers to flush out all silt particles of

0.2 mm size and above.

Two no. trough type underground desilting chambers operating under

pressure flow conditions are proposed. These are fed by independent intake

tunnels. Each desilting chamber will be 12.5 m wide, 15 m deep and 266 m

long and will have smooth transitions at inlet and outlet ends to avoid eddy

formations.

The desilting chamber troughs will have 2 m x 2 m longitudinal drains at bedlevel. These drains will be covered with removable slabs having 250 mm to 25

mm dia holes at 4.0 m c/c through which the silt particles that settle will pass

to the silt collecting drains. At the end of desilting chambers, silt flushing gates

are provided in an underground hoist chamber to flush out silt laden waters in

the drains to a common silt flushing tunnel that takes the silt-laden waters

back to the river. These silt flushing gates of size 2.0 x 2.0 m can be

vertical/radial gates. An opening of about 20 cm height of these gates will

induce sufficient silt flushing velocity to flush out the accumulated silt in the

d i Th ilt fl hi di h i th h h t i ld

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6.6 HEAD RACE TUNNEL

A single horseshoe shaped headrace tunnel of 5.5 m finished diameter and

about 3.545 km length has been designed to carry the required flows

further upto the surge shaft. This tunnel is designed to carry a discharge of

91.2 m3/s. The head race tunnel passes under three deep nallahs along its

route. The tunnel alignment has been so fixed that it has adequate rock

cover at each nalla location. The tunnel will be provided with suitable rock

support system depending upon the geological strata / formations enroute.

Apart from the rock support system, the headrace tunnel will be provided with

a 300 mm thick plain cement concrete lining to reduce the head loss due to

friction.

The details of typical rock support system and the concrete lining of headrace

tunnel are shown in drawing no. WAP/PFR/CHHUNGER CHAL/1006.

6.7 SURGE SHAFT

To take care of pressure rise in case of sudden load rejection and to meet the

sudden demand of water in case of sudden load acceptance, a simple surge

shaft of 12 m diameter and maximum surge elevation of 2810 m has been

provided at the end of headrace tunnel. This proposed surge shaft will serve

the following functions:-

(i) To provide a free water surface close to the flow regulating

mechanism.

(ii) T li it th l th f i d t d it li bl t t

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(vi) To supply the additional flows required by the turbine during the load

acceptance until the headrace tunnel is accelerated to new steady

state value.

The bottom of surge shaft will be at EL 2734 m and the normal minimum

water level and maximum surge levels will be 2761 m & 2810 m respectively.

The top of surge shaft will be located at EL. 2815 m. In case during detail

design, it is found that minimum surge level comes lower than crown of HRT,

expansion chambers of suitable capacity can be considered.

The surge shaft is provided with adequate rock support system and a

reinforced concrete lining of 500 mm thickness upto maximum surge level.

Thereafter, upto the top level, only rock support system and 150 mm

shotcreting will be sufficient.

6.8 PRESSURE SHAFT

A single pressure shaft of 4.6 m diameter bifurcating to 2 numbers of 3.25diameter each near underground power house is proposed at centerline

elevation of turbine at 2463 m.

Flows to turbines will be controlled by independent butterfly valves placed in

the powerhouse cavern.

The pressure shaft shall be steel lined and shall be backfilled with 500 mm

thick M-20 grade concrete. The thickness of steel liner shall vary from 14 mm

i th b i i t 32 th h D i N

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6.9 UNDERGROUND POWER HOUSE COMPLEX

An underground power house is proposed for this project because river bank

at the tailrace outfall is very steep and there is no space where a surface

power house can be economically built. The geological strata at this location

comprises of upper member of Dar formations consisting of migmatites,

banded gneiss, schists with clacisilicates rocks and marble. These rocks aretraversed by migmatites veins and intruded by granite near contact with

Tethyan sequence. This geological strata is considered suitable for an

underground power house. The roof and sides of the power house and the

transformer cavities will be provided with suitable supporting system like

shotcrete, rock bolts etc. as necessary.

The underground power house complex comprises of two separate caverns

about 38 m apart. The main cavern of 21m width which will house generating

equipment is 89 m long, out of which 47 m length will house 2 units of 120

MW each and the remaining is occupied by a service bay of 22 m length and

a control block of 20 m length. The generator floor and service bay will be atEL 2474.5 m and the control block portion will be at higher elevation with a

workshop facility underneath. Besides the turbine & generators etc, this

cavern will house 2 no. main inlet valves, one for each unit. The centre line of

turbines with be at EL 2466.5 m. An EOT crane of suitable capacity will be

provided which will run from the beginning of service bay to the end of

machine hall.

The transformer cavern will be 14 m wide and would house transformers and

GIS A bl til ti t l ill b id d f thi t th

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The underground caverns will be approached by a common main access

tunnel of 7.0 m dia D-shaped starting from the existing road / path along the

right bank of river. This access tunnel will have a maximum gradient of 1 in

15 and will be concrete lined and properly electrified and ventilated.

The details of underground power house complex are shown in drawing no.

WAP/PFR/CHHUNGER CHAL/1007 and 1008.

6.10 ELECTROMECHANICAL WORKS

The proposed 240 MW Chhungur Chal Hydro-Electric Project would be Run

off the river type development. The installed capacity would be provided by

2 nos. Francis, Vertical axis turbine driven generating units of120 MW each

housed in an underground powerhouse. It is proposed to provide Inlet Valve

of spherical type for each turbine, which would be accommodated in the

powerhouse cavern.

The generation voltage of 11 kV would be stepped up to 220 kV through three45 MVA, 11/220/3 kV ODWF type single-phase transformers for each unit

located in Transformer cavern. The 11 kV-isolated phase phase busducts

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

transformers. The 220 kV bushings of the transformers would be connected

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

transformers in transformer cavern.

The arrangement of generating equipments, unit step up transformers, etc. is

i di t d i th f ll i d i

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The power generated would be evacuated through one 220 kV double circuit

transmission line. The single line diagram is enclosed given in Drawing NO.

WAP/PFR/ CHHUNGER CHAL/1009.

6.11 BRIEF PARTICULARS OF EQUIPMENTS

Turbine and Governor

The upstream levels, tailrace level and head available for power generation

are indicated below :

i) Upstream Levels

FRL EL 2780.0 M

MDDL EL 2769.0M

ii) Tailrace Levels

Maximum EL 2473.0M

Minimum EL 2470.0 M

iii) Heads

Maximum net head 298.0 M

Minimum net head 284.0 M

Rated head 292.83 M

The specific speed of the turbine determined as 104 RPM leads to the choice

of Francis turbine for this station. The turbine would be suitably rated to

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as not to increase the speed rise and pressure rise more than 45% and 30%

respectively under full load throw off condition.

6.12 MAIN INLET VALVE

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

line of defence in stopping the water flow to the turbine when due to governormalfunctioning, the generating units may tend to go to runaway speed.

During the time when the generating unit is under stand still 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.

6.13 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. Thegenerator 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 - 120 MW

ii) Power factor - 0.9 lag

iii) Speed - 300 RPM

iv) Class of Insulation of

stator and rotor winding - Class 'F'

) G ti V lt 11 kV

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6.14 UNIT STEP-UP TRANSFORMER

Three 45 MVA, 11/220/3 kV single-phase transformers, would be provided

for each generating unit with one spare transformer of same rating common

for all the units. The likely transport limitations have dictated the choice for

Single-phase transformers. The transformers would have Oil Directed Water

Forced (ODWF) type cooling arrangement. These transformers would be

located in the transformer cavern. The 11 kV bushing of the transformers

would be connected with 11 kV terminals of generator through 11 kV bus

ducts. The 220 kV bushing would be connected with 220 kV Gas Insulated

Switchgear located on the floor above the transformers in transformer cavern.

6.15 EOT CRANE

The heaviest equipment which the powerhouse cranes are 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 365tonnes.It is proposed to provide two EOT cranes of 200/20tonnes capacity each.

6.16 AUXILIARY EQUIPMENT AND SYSTEMS FOR THE POWER HOUSE

Following equipments for the auxiliary systems of the power house would be

provided:

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

t f t

S S O C G C A O C

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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

6.17 220 kV SWITCHYARD

Due to likely non-availability of flat space for outdoor switchyard it is proposed

to provide 220 kV Gas-Insulated Switchgear located on the floor above thetransformers in transformer cavern havingsix bays out of which two bays for

generator incoming, two bays for220 kV transmission lines, one bay for step

down transformer and one bay for bus coupler. The double bus bar

arrangement has been proposed which would provide flexibility and reliability

in the operation of the plant.

6.17 OBSERVATIONS OF CEA & CWC

Th D ft R t f thi j t b itt d t CEA f l d i

PFR STUDIES OF CHHUNGUR CHAL HE PROJECT

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CHAPTER-VII

POWER POTENTIAL STUDIES

7.1 GENERAL

The power potential studies have been carried out for CHHUNGUR CHAL

Hydel Scheme, which is located in Uttranchal State. The projected power

supply position for 11th Plan indicate 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 off the river development with diurnal storage for peaking

purpose. The powerhouse would be of Under Ground type.

The scheme is located down stream of Bokang Bailing HE Project which

has been planned as storage based scheme. Therefore, this scheme has

been planned considering regulated discharges from Bokang Bailing.

Benefits have also been determined for an alternative scheme with

unregulated inflows received.

7.2 FIXATION OF FRL/MDDL

The FRL of the pondage has been fixed at EL 2780.0 M so as to get

adequate storage capacity for peaking operation of the plant during lean

flow period (January, February and March). The FRL has also been


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estimated as 2.240 million cubic metres, thus making available live storage

of 1.490 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 onegenerating unit at 10% load has been considered as EL 2470 M. The

Maximum TWL at EL 2473 M corresponds to all the units running at full

load. The minimum TWL has also been coordinated with FRL of

downstream Sela Urthing HEP which is at EL 2470 M.

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 inChapter No. 5 on hydrology. Water flows series for 30 years (1962-63 to

1991-92) has been utilized for power potential studies and is indicated in

Annex-7.2.

7.5 TYPE OF TURBINE

Based on rated head of 292.83 M and capacity of generating units, Francis

turbine is considered optimum choice for this station. Following efficiencies

t i i t F i t bi d i ti it h b tili d f


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7.6 90% AND 50% DEPENDABLE YEARS

For determining 90% and 50% dependable years, Annual energy

generation for all the 30 years (1962-63 to 1991-92) has been computed

with unlimited installed capacity. The year wise power potential and energy

generation is indicated in Annex-7.3 & 7.4 respectively. Annual energy

generation is tabulated in descending order and indicated in Annex-7.5.The 90% and 50% dependable years have been determined in the

following basis, where N is the no. of years for which inflow series is

available.

90%

year

- (N+1) x 0.9 - 31x0.9 - 28th

year

50%

year

- (N+1) x 0.5 - 31x0.5 - 16th

year

Based on above, 1976-77 and 1969-70 work out to be 90% and 50%

dependable years respectively.

Analysis of flow in lean period indicated in Annex 7.2, however, reveals

that lean period flow is maximum in 1976-77. The installation determined

on this basis would be very optimistic figure. It would thus be more

appropriate in this case to determine 90% dependable year based on lean

flow discharge. The energy generation in lean flow period has been

computed and tabulated in descending order in Annex 7.5. Based on

energy generation in lean period, 90% dependable year comes out to be


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discharges released from Bokang Beiling plus the discharge from inter-

mediate catchment. The computations of total inflows are indicated in

Annex 7.6 for 90% year and in Annex 7.9 (A) for 50% dependable year.

The energy computations for various Installed capacities (180 MW to 280

MW) are indicated in Annex 7.7 and Annex 7.9 (B) for 90% and 50%

dependable years respectively.

7.7 INSTALLED CAPACITY

7.7.1 The power supply demand scenario projected for 11 th five-year plan

indicated that there would be shortage of power during peak hours in

Uttranchal as well as in Northern Region. The peak period is about four

hours.

7.7.2 The power potential in a 90% dependable year with different installed

capacities (180 MW to 280 MW) is indicated in Annex-7.7. The studies

have been carried out with rated head of 292.83 M and friction loss in water

conductor system as 12.0 m. The study indicates that the firm power is40.21 MW continuous. Considering four hours peaking, the installed

capacity required would be about 241.0 MW.

7.7.3 For optimization of Installed Capacity, annual energy generation (KWh),

Incremental Energy generation d(KWh) and ratio of Incremental energy to

Incremental Installed Capacity d(KWh)/d(KW) have been computed for

90% dependable year for installed capacity up to 280 MW varying in steps

of 10 MW. The results are indicated in Annex-7.8. It would be seen there

f th t d(KWh)/d(KW) h t d f i i i t ll d it


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7.7.4 Keeping in view the system requirements and analysis of Incremental

energy and Incremental installed capacity, the installed capacity of 240 MW

is considered optimum. With the installation of 240 MW the load factor of

operation during lean flow period would be 16.75% corresponding to 4.02

hours of peaking.

7.7.5 Regarding number of generating units to be installed, there are threeoptions:

1 x 240 MW

2 x 120 MW

3 x 80 MW

Installation of one unit of 240 MW would be most cost effective. However,

the width of underground powerhouse cavern required for this size of unit

would not be feasible from geological considerations. Further there may be

difficulties in transportation of equipment in hilly terrain. Installations of two

units would provide increased reliability of power supply from the stationand more flexibility for peak load operation. Installation of 3 units would

have all the advantages applicable with the installation of 2 units, however,

it would result in increased capital cost of the project. Considering the

above it has been decided to install 2 units of 120 MW each. The Francis

turbine would be suitably rated to provide 120 MW at generator terminals at

rated head of 292.83 meters. The speed of the generating unit has been

determined as 300 rpm.

7 8 RESULTS OF STUDIES


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Parameters 90% dependable year 50% dependable year

Annual Energy

Generation (Gwh)

853.28 987.95

MW continuous 40.21 50.29

Average annual load

factor

40.59% 46.99%

Load factor in lean flow

months

16.75% 20.95%

The design energy computations have been carried out and indicated in

Annex-7.10. The design energy of 845.12 GWh would be considered for

financial evaluation.

The live storage capacity of the pondage at FRL of EL 2780 M and MDDL at

EL 2769 M has been computed as 1089.46 MWh (1.490 million cubic meters).

The storage capacity required for peaking operation works out to 965.04 MWh

(1.319 million cubic meters) against 1.49 million cubic metre available. Thus,

storage available is sufficient for peaking operation.

7.9 ALTERNATIVE SCHEME UTILIZING UN-REGULATED INFLOWS

Power Potential Studies have also been carried out considering un-

regulated inflows. The energy benefits determined in 90% and 50% years

are indicated in Annex. 7.11 & 7.14 respectively. The installed capacity

has been determined to be 190 MW as indicated in Annex 7 12 Design


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Parameters Scheme based on

regulated discharge

Scheme based on un-

regulated discharge

Installed capacity (MW) 240 190

Firm Power (MW) 40.21 31.08

Load Factor (Lean flow) 16.75% 16.36%

Energy Generation(GWh)

i) 90% dependable year

ii) 50% dependable year

853.28

987.95

773.63

884.24

Design Energy (GWh) 845.12 752.66

It would be seen from above, that use of regulated inflows result in

increase in firm power generation which consequently leads to higher

installed capacity and increase in annual energy generation, design energy

etc. Therefore, the alternative utilizing regulated inflows has been

selected.

7.10 CONCLUSIONS

The power potential studies carried out indicate that installed capacity of 240

MW comprising of 2 generating units of 120 MW each would be required for

this HEP to derive optimum power benefits. The project would afford energy

generation of 853.28 Gwh in a 90% dependable year.


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level corresponding to discharge. In the present study, tail race water level

was considered constant.

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

based on the data of topographic survey.

7.11.3 As the benefits from the project gets increased by utlising regulated inflows, itis recommended that construction of this project should be planned after

implementation of Bokang Bailing.


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CHAPTER - VIII

POWER EVACUATION

8.1 APPRAISAL OF EXISTING POWER EVACUATION FACILITIES

The Project is located between latitude 29-30-00 (D-M-S) East to latitude

31-30-00 (D-M-S) East and longitude 78.5o N to 81o N. 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 78.5o

N to 79.5o

N namely Harsil, Bhaironghati, Gangotri,

Jadhganga, Karmoli Hydro Power Projects. The next group of Hydro Electric

Projects which lie between longitude 79.3o

N to 80o

N are Badrinath, Gohana

Tal, Rishiganga II, Rishiganga I, Jelum Tamak, Deodi, Devasari Dam and

Malari Jelam. Whereas in the next series the Hydro Electric Projects which lie

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

Bogudiyar, Sirkari Bhytol Rus Bagar, Khasiya Bada, 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


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8.3 ARRANGEMENT FOR EVACUATION OF POWER FROM CHHUNGUR

CHAL HEP

The 240 MW power generated at 11 kV at Chhungur Chal HEP will be

stepped upto 220 kV by unit step-up-transformers. The power will be taken to

newly proposed 400/220 kV Substation at Didi hat. Proposed line from

Chhungur Chal to Didi hat for evacuation of power is shown at Annexure-8.3.

8.4 ROUTE LENGTH AND COSTING OF 220 KV D/C TRANSMISSION LINE

FOR EVACUATION OF POWER FROM CHHUNGUR CHAL HEP

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

D/C line to newly proposed 400/220 kV substation at Didi hat. The totallength of this line would be around 50 kms upto Didi hat. The cost of this

portion of line is estimated as Rs.37.50 crores.


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CHAPTER IX

INITIAL ENVIRONMENTAL EXAMINATION STUDIES

9.1. INTRODUCTION

The Initial Environmental Examination of Chhunger Chal hydroelectric project

has following objectives through various phases of development which are

proposed to be covered.

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 undergo 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


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9.2 ENVIRONMENTAL BASELINE SETTING

The study area covered 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 project is located in an 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 structure site is of the order of 400. The major source of

water in the project area are rivers or nallahs which flow adjacent to the

habitations, which are conveyed to the consumers. The sewage so

generated, too outfalls into various streams or nallahs flowing adjacent

to the settlements. The total BOD loading from domestic sources in the

catchment area is of the order of 18 kg/day. The effluent ultimately

reaches river Goriganga through various streams/channels outfalling

into the river. The quantity of BOD loading is insignificant to cause any

d i t t lit f th i i fl i th i


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b) Landuse

The landuse pattern of the project area was studied using satellite

data. The submergence area was superimposed on the satellite data,

and the landuse pattern was ascertained, which is given in Table-9.1.

The satellite imagery (IRS 1C, LISS-III + PAN Data) of the study area is

given as Figure-9.1.

Table-9.1Landuse pattern of the submergence area

S. No. Landuse / Land cover Area (ha)

1. Dense forest 8.10

2. Grass land 1.35

3. Water bodies 4.05

Total 13.5

The submergence area is 13.5 ha. The major portion of the

submergence is the forest land (8.1 ha), which accounts for 60 % of the

total submergence area. The other major landuse category is water

bodies (3.60 ha). The area under grasslands is 1.35 ha.

As a part of next phase of Environmental study, it is recommended that

detailed studies be conducted to ascertain the ownership status ofthese lands, i.e. whether the land belongs Forest Department or is it a

non-forest government land. The pasture land could still be

categorized as forest land as far as ownership status is concerned In


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submergence area lies in Askot Wildlife sanctuary, the entire area

irrespective of its land cover is to considered as forest land.

9.2.2 Ecological Aspects

a) Vegetation

The proposed project site is located in Askot wild life Sanctuary, about

2 km upstream of the confluence of Dhauliganga with Nagling gad. The

power house is proposed to be constructed at about 1.5 km

downstream of Chal village on the right bank of Dhauliganga. The

forests in the area can be categorized as temperate forest with

Kharsu-Oak forest being the dominant forest sub-type. The dominant

floral species observed in the project area are Kharsu (Quercus

semicarpifolia) with associates such as Kathboj (Baular aloides),

Buransh (Rhododendron arboreum) and Bhojpatra (Betula utilies). The

proposed site is located in deep gorge, where fairly dense oak forest

was observed on south facing hill slops, while on the right bank

vegetation can be categorised as open forests. The hill top are

generally barren with scattered trees mainly consisting of Bhojpatra,

Tuner and Kathbhoj. Vegetation in the vally near project site include

Ringal, Thumer, Timla, Akhrot and Kail. Due to the high elevation and

cold climate several herbs of medicinal importance have also been

reported in this area. Dominant species of herbs are Ghingaru

(Pysectautha crenulata), Hinsalu (Rubus ellipticus), Kutki (Pierotchiza

kurroa), etc.


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Table 9.2

Major floral species observed in the study area

Local Names Scientific Names

A. TreesBhojpatra Betula utiliesTansen Tsuga demosaThuner Taxus bacataAkhrot Juglans regia

Timla Ficus auriculataBurans Rhododendron arboriumKail Pinus racuburghilKathbhoj Baula aloides

B. Shurbs

Hinsalu Rubus ellipticusKutki Picrotchiza

Ghingaru Rysectsantha CrenulataKilmora Berberis asiaticaBankakri Podophyllum emodiKapoor Kachari Hedychinum spieatumChirayata Swartia onirataHans Ray Curculigo orchioidesJatamashi Nardostachys grandifolia

b) Fauna

As mentioned earlier, the proposed project is located in Askot wildlife

Sanctuary. The same was formed in July 1986 for protection of Musk

deer. The project area has fairly good forests on hill slopes but major

portion of the catchment is snow bound. The forests in the project area

does not represent good habitat for wildlife. Some mammals who

prefer cooler area have been reported in the project area.


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Reptiles are not very common in the area> The only reptilian species

noticed during field study was common lizard (Himidectyles brooki).

Amongst avi fauna, monal (Zophophorus impejanus), snow partridge

(Lerwa lerwa) and Crow (Corvus macrorhnchus) are the dominant

species.

The major faunal species reported in this area are given in Table-9.3.

Table 9.3Major faunal species reported in the study area

Local Name Scientific Name Scientific as per wildlife act

Mammals

Kasturi Mrig Moschus Moschifirus Schedule ISnow Leopard Panthera uncia - do Barking deer Muntiacus Muntjark - do Goral Nemarhaeus goral - do Black Bear Selevactos thibetanus - do

Reptiles

Common lizard Himidectyles brookiAvi fauna

Monal Zophophorus impyanusBlue rock pigion Colimba liviaHill lpatridge Arbasophila torquotaCrow Corvus macrorhchus

Snow patridge Lerwa lirwaSnow cock Tetraogallus himalayensisSnow pigeon Columba leuconota


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the primary and secondary productivity is very low. The temperature

and natural biota are main factors which govern the growth of fish in

the waters body. Two type of fish i.e. snow Trout and Mahaseer are

reported in river Dhauliganga. However these groups are reported only

near the confluence of river Dhauli with river Kali. 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 fishes. Tank

or pond fisheries is not in vogue in the project area.

9.2.2 Socio-economic aspects

There are a total 9 villages observed in the study area. The average family

size in the study area is 3.7 with a total population on 1008. The number of

females per 1000 male is about 938. The SC and ST population in the area is

13% and 84% of the total production respectively. The male and female

literacy rates are 48.5% and 19.5% respectively. The overall literacy rate in

the study area villages is 34.4%. The demographic profile of the study area

villages is given in Table 9.4.

Table 9.4Demographic profile of study area villages

Population LiteratesS.No

Village No. ofhouseholds Male Female Total

SC ST

Male Female

1. Bauling 29 58 71 129 25 103 25 82. Nagling 40 101 78 179 53 105 50 173. Sela 26 54 50 104 18 86 21 74. Chal 28 63 42 105 13 91 30 25. Baling 34 70 64 134 6 127 46 126 Dugtu 49 85 100 185 0 185 33 31


C O O C S

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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 fauna- 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 project

Documents

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