CHAPTER - I EXECUTIVE SUMMARY - Ministry of Power

1.1 INTRODUCTION 

CHAPTER - I 

EXECUTIVE SUMMARY 

PFR STUDIES OF KALAI H.E. PROJECT 

The Kalai Hydroelectric Project located near village Kumblung in Lohit district 

of Arunachal State envisages utilization of the waters of the river Lohit, a 

tributary of Brahmaputra River for power generation on storage type 

development, harnessing gross head of about 235.0 m. 

The project with a proposed installation of 2600 MW (10x260 MW) would 

afford an annual energy generation of 10608.64 MU in a 90% dependable 

year. The tariff from the project at present day cost would be Rs. 0.88 /kWh 

(levellised). 

The Dam site is located at Latitude 27 o 56’ 30” N; Longitude 96 o 56’ 15” E. 

The dam site is approachable from Tezu, the district headquarter of Lohit by 

road and the site is at a distance of about 310 km from Tinsukhia. The 

nearest rail head is located at Tinsukhia in Assam (about 200 km from Tezu) 

and the nearest airport is located at Dibrugarh. 

1.2 SCOPE OF WORKS 

The Kalai HE project envisages construction of: 

• 241.0 m high Earth & Rockfill dam with chute spillway across the River 

Lohit to provide a live storage of 909.739 M cum with FRL at El 1160.0 

m and MDDL at El 1054.0 m; 

1-1


• 5 nos. Each 1.01 km long and 10.0 m dia (Horse-shoe shaped) head 

race tunnel terminating in a pressure shaft 

• 5 nos. Each 226 m long, 8.0 m dia pressure shaft bifurcated into 2 of 

5.6 m dia pressure shaft to feed two units each 

• an underground power house having an installation of 10 Francis 

Turbine driven generating units of 260.0 MW each operating under a 

rated head of 192.291 m; and 

• 5 nos. Each 1.76 km long tail race tunnel of 10.0 m dia (Horse-shoe 

Shaped) to carry the power house releases back to the river 

1.3 HYDROLOGY 

The river Lohit drains a catchment of area of about 16500.0 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 

inflow series for 17 years for the period 1983-84 to 1999-2000 for the sites. 

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

Studies. The design flood has been assessed as 11950 cumecs. 

1.4 POWER POTENTIAL STUDIES 

The computed 10-daily inflow series corresponding to 90% dependability has 

been utilised for assessment of power benefits from the project. An installation 

of 2600 MW comprising 10 generating units of 260 MW each 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 in a 90% dependable year : 10608.64 MU 

Annual Load Factor : 46.58% 

Generation during Lean Flow Season 

Energy output (MWc) : 509.44 MU 

Lean Period Load Factor : 19.59% 

A live storage of 909.739 M cum has been provided in the storage dam and 

the project would offer annual energy generation of 10608.64 MU and 

14508.77 MU in 90% & 50% dependable year respectively and the design 

energy has been computed as 10449.52 MU. 

1.5 POWER EVACUATION ASPECTS 

The 2600 MW power generated at 11 KV at Kalai HEP will be stepped upto 

400 KV by unit step transformers. The power will be tranmitted to the 

proposed Roing/Dambuk pooling point. The cost trans line is Rs. 412.50 

crores. 

1.6 ENVIRONMENTAL ASPECTS 

The project site is located in mixed forest area. The submergence area is 

1296.7 ha,. In addition, land will also be required for other project 

appurtenant structure. Based on assessment of environmental impacts, 

management plans have to be formulated for acquisition of land in mixed 

forest area, wildlife conservation, muck disposal, quarry stabilization, 

acquisition of private land and other environmental issues. These issues 

would be addressed during the investigation for DPR. 

1-3

1.7 ESTIMATES OF THE COST 


The project is estimated to cost Rs. 6225.17 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) 

1.8 FINANCIAL ASPECTS 

As indicated above, the Kalai HE Project, with an estimated cost (Generation 

only ) of Rs. 6225.17 Crores (including IDC of Rs. 1196.05 Crores) and 

design energy of 10449.52 MU in a 90% dependable year is proposed to be 

completed in a period of 7 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. 1.01 /kWh & Rs. 0.88/kWh respectively. 

1.9 CONCLUSIONS 

Civil Works : 3159.92 

Electro Mechanical Works : 1869.19 

Sub Total : 5029.12 

Interest During Construction : 1196.05 

Total (Generation) : 6225.17 

Transmission Works : 412.50 

Grand Total : 6637.67 

Kalai HE Project is located in a remote area and involves major civil works 

and could be completed in 7 years. The project would afford a design energy 

1-4


of 10449.52 MU in a 90% dependable year. The cost per MW installed works 

out to Rs. 1.93 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 


Arunachal Pradesh India’s land of rising sun’ attained its statehood on 20 th 

Feb 1987 and is the largest state area wise situated in the North East region. 

It is one of the most sparsely populated state in India, stretching from snow 

capped mountains in the North to the plains of Brahmaputra Valley in the 

South. It has a long international boundary with Bhutan in the West, China in 

the North and North East, Myanmar in the East and Assam in the South. 

Arunachal Pradesh is situated between Latitude 26 o 30’ 0” N and 29 o 30’ 0” N 

and Longitude 91 o 30’ 00” E and 97 o 30’ 00” E. It is mainly a hilly state 

interspersed among deep valleys, narrow gorges and deep green lush forests. 

It is bestowed with natural unspoilt scenic beauty and places of historical and 

tourist interest and exotic animals such as ‘Yak’ and ‘Mitten’ supporting 

richness of life forms and present a panorama of biological diversity. National 

Highways NH – 52 A and NH – 52 cover about 293 km length in the state. 

there is no railway head and airport in the state. The nearest rail head is at 

Tinsukhia in Assam which is about 200 kms from Tezu, district head quarter 

of Lohit. 

The geographical area of Arunachal Pradesh is 83,743 Sq. Km with Itanagar 

as its capital located at an altitude of about 530 m above MSL. It is named 

after Itafort, meaning fort of bricks built in the 14 th century, ‘Kangte’ is the 

highest peak in the state 7090 m about MSL in West Kameng district. The 

state is divided in thirteen administrative districts namely; Tawang, West 

Kameng, East Kameng, Lower Subansiri, Upper Subansiri, West Siang, East 

Siang, Dibang Valley, Changlong, Tirap, Papum Pare, Lohit and Upper Siang. 

2-1


The climate of Arunachal Pradesh is humid and sub tropical type. The area 

experiences heavy and long monsoon between May and September. The 

average annual rainfall is about 3800 mm. Winters are severe with thick 

mist formation and occasional rainfall. Summer season is hot and humid. The 

prolonged period of Monsoon has resulted is luxuriant forest growth over the 

hill slopes. 

The total population of Arunachal Pradesh is 1,091,117 (2001 census). The 

literacy rate on an average is 54.74%. Nearly 85% population of the state is 

engaged in Agriculture, 94%of the population of the state lives in rural belt. A 

section of the population however, is engaged in the small scale industries 

based on forest produce and mineral resources like coal etc. 

The main rivers system in the state are the Siang, Kameng, Subansiri, Kamla, 

Siyum, Dibang, Lohit, Noa-Dihing Kamlang and Tirap. 

Arunachal Pradesh has a huge potential to generate hydroelectric power. 

The state contains number of high head, mini and micro hydel projects in the 

country. Several major hydro power projects are being planned and 

investigated by NEEPCO, Meghalaya state Electricity Board, Brahmaputra 

Control Board and other State and Central Agencies. In view of severe 

power shortage in all the regions which is likely to increase further due to 

various developmental activities in the years to come, there does not appear 

any difficulty in evacuating the cheap hydro power of this region to other parts 

of the country thereby generating revenues to the concerned states and 

development activities in the country. 

The proposed project will play a major role in improving the overall economic 

development of the region and socio economic condition of the people of the 

region in particular and other neighbouring states in general. 

2-2

2.2 POWER SCENARIO IN NORTH EASTERN REGION 

2.2.1 Present Status 


The North Eastern Region comprises of the States of Arunachal Pradesh, 

Assam, Manipur, Meghalaya, Mizoram, Nagaland and Tripura. This region of 

India has been consistantly suffering from shortages in meeting the energy 

demand during the last decade. The shortfall of energy has become more 

aggravated since 1991. This situation might prevail for some year till more 

hydro Power Projects come up in the region. This will give an impetus to the 

industrial and financial growth of the State. 

The percentage pattern of actual utilisation of electric energy of the North 

Eastern states during 1997-98 and projected (2003-04) are given below in 

Table 2.1 (Ref. Sixteenth Electric Power Survey of India CEA) 

S. 

No. 

Table 2.1 

Percentage Utilisation (Sectorwise) 

Category Actual 

(1997-98) 

Projected 

(2003-04) 

1 Domestic 36.23 37.76 

2 Commercial 10.52 8.12 

3 Irrigation 2.91 3.94 

4. Industry 32.56 32.64 

5. Other 17.78 17.63 

6. Total 100.00 100.00 

Peak load (MW) 93.00 168.00 

The statewise energy requirement at Power Station Bus bars and energy 

consumption (Public Utilistion) as per estimate of 2004-05 are given as under 

2-3

S. 

No. 


in Table 2.2 a depicting overall energy deficit of 24.05% in the North Eastern 

Region. Table 2.2 b gives the peak load projections. 

State Requirement 

2004-05 

1. Arunachal 

Pradesh 

Table 2.2 (a) 

Energy Status (M KWh) 

Estimated 

Consumption 

(2004-05) 

Shortage/ 

surplus(-/+) 

% of value 

264.0 192.65 - 71.35 27.03 

2. Assam 4558.0 3528.50 - 1029.5 22.58 

3. Manipur 857.0 678.99 - 178.01 20.77 

4. Meghalaya 811.00 606.36 - 204.64 25.23 

5. Mizorun 433.00 307.50 - 125.5 28.98 

6. Nagaland 335.00 231.06 - 103.94 31.03 

7. Tripura 832.00 598.75 - 233.25 28.03 

Sl. 

NO. 

N.E.Region 8090.0 6143.81 (-) 1946.19 24.05 

State 

Table 2.2 (b) 

Peak Load Projections 

Peak Load Estimated (MW) 

1997-98 2003-04 2004-05 2011-12 2016-17 

1. Arunachal Pradesh 58 81 85 136 189 

2. Assam 473.0 793 853 1423 2034 

3. Manipur 86 189 208 406 651 

4. Meghalaya 93 157 168 293 430 

5. Mizorum 53 111 119 217 345 

6. Nagaland 50 80 85 141 200 

7. Tripura 77 193 211 396 616 

North 

Region 

Eastern 824 1485 1601 2789 4134 

2-4


2.3 NECESSITY OF HYDRO POWER DEVELOPMENT IN THE STATE 

2.3.1 Existing and Hydro Project Under Investigation 

The scenario of hydro-electric projects completed so far in Arunachal Pradesh 

is given in Table 2.3 and H.E projects under different stages of investigations 

is given in Table 2.4 

S. 

No. 

Table 2.3 

Projects completed 

Name of Project Capacity 

(MW) 

1. Ranganadi HE Projects 405 

Table 2.4 

Projects under different stage of investigation in 

Arunachal Pradesh 

Sr. 

No. 

Name of Project 

1. Subansiri Upper Hydro Power Project 

2. Subansiri Midde HydroPower Project 

3. Siang Middle Hydro Power Project 

4. Kawang Hydel Power Project 

5. Kambang Small Hydel Power Project 

6. Sippy Small Hydel Power Project 

7. Subansiri Lower HE Project 

2-5


2.3.2 Hydro Power Potential and Development of NE states 

Statewise details of Hydro Potential as existing and developed is given in 

Table2.5 

Table 2.5 

S. State Potential Assessed Potential Developed 

No. 

(MW) 

(MW) 

1 Aruanchal 

Pradesh 

50,328 281 

2 Assam 674 250 

3 Manipur 1,784 105 

4 Meghalaya 2,394 185 

5 Mizoram 2,196 0 

6 Nagaland 1,574 91 

7 Tripura 21 15 

8 Sikkim 4,286 84 

Total 63,257 1,011 

2.3.3 Hydro and Thermal Power Status 

Installed capacity of Power Projects, Peak generation and gross energy 

generation in 2000-01 in NE Region is given in Table 2.6. 

Table 2.6 

S. MW installed Capacity as on 31.03.2001 

No. State 

Agency 

Thermal Hydro Total 

Max. 

Generation 

(MW) 

Gross 

Energy 

Generation 

(MU) 

1. Aurnachal 

Pradesh 

15.80 23.60 39.40 - - 

2. Assam 620.70 2 622.70 218.31 1059.208 

3. Manipur 9.30 2.80 12.10 - - 

2-6

S. MW installed Capacity as on 31.03.2001 

No. State 

Agency 

Thermal Hydro Total 


Max. 

Generation 

(MW) 

Gross 

Energy 

Generation 

(MU) 

4. Mizoram 19.10 5.40 24.50 - - 

5. Nagaland 3.26 3.30 6.56 - - 

6. Meghalaya 00 185.20 185.20 184.80 657.519 

7. Tripura 70.60 16 86.6. 54.50 328.748 

Total in state 738.76 

sector 

Central Sector 

238.30 977.06 

A.NEEPCO 378.66 325.00 703.66 639.20 2559.063 

B.NHPC - 105.00 105.00 91.00 551.06 

Total in NE 

Region 

1117.42 

(62.58%) 

668.30 

(37.42% 

1785.72 

(100%) 

(The generations connected to the NE Grid are only shown here) 

2.3.4 State Power Statistics 

The projected Energy requirement & Peak load for Arunachal Pradesh at the 

end of 9 th and 11 th plan is indicated as below: 

Energy Requirement 

Peak Load 

(MU) 

(MW) 

Plan 2001-02 

End of 9 th 2011-12 

Plan End of 11 th 2001-02 

Plan End of 9 th 2011-12 

Plan End of 11 th Plan 

346 982 94 249 

The installed capacity available ( as on 29.2.2004) to state is as : 

Share in Central Sector 117.00 MW 

State Sector 45.43 MW 

Private Sector 0.00 MW 

Total 162.43 MW 

2-7


The present condition of Peak Demand/Peak Met of Arunachal Pradesh 

is as: 

Period Peak 

Demand 

(MW) 

Peak Met 

(MW) 

Surplus/Deficit 

(MW) (%) 

April-Feb. 2004 50 50 0 0 

Similarly, the actual power supply position of Arunachal Pradesh is as: 

Period Requirement 

(MU) 

Availability 

(MU) 


(-) MU 


(%) 

April-Feb. 2004 163 161 -2 -1.2 

2.4 BRIDGING THE GAP OF HYDRO POWER GENERATION 

With a view to priortise large number of identified Hydro Power schemes and 

to harness the vast untapped hydro potential in the country, the ranking 

studies have been carried out by Central Electricity Authority, Ministry of 

Power, Government of India to take up the Hydro Power projects in order of 

their attractiveness for implementation. Subsequently, after consultation 

process initiated by the Ministry of Power, with various state agencies, central 

public sector units etc., it was considered appropriate that Preliminary 

Feasibility Reports (PFRs) of selected hydro electric projects in Arunachal 

Pradesh be taken up so that feasibility of the individual schemes considered 

during ranking studies could been established. 

2-8


The list of Two Hydro Electric Project of Arunachal Pradesh for which 

Preliminary Feasibility Report Studies are proposed is given as under in Table 

2.7 

Table 2.7 

List of Projects for Prepartion of PFR’s in Arunachal Pradesh 

S. 

No 

Name of Scheme River 

1 Kalai HE Project Lohit 

2. Hutong HE Project Lohit 

In order to meet the growing energy demand of the state, it is essential to 

develop the hydro power potential of Arunachal Pradesh to give boost to the 

industrial growth in the state and accordingly this report presents the Pre 

Feasibility stage studies of the KALAI HE PROJECT located on the river 

Lohit in Lohit district of Arunachal Pradesh. 

2-9

3.1 GENERAL 

CHAPTER - III 

THE PROJECT AREA 


The Kalai H.E. project envisages creation of a storage reservoir on the Lohit 

river, a left bank tributary of Brahmaputra river with a view to utilise flows of 

Lohit river over large head available for hydro power generation. The Lohit 

Basin is the eastern most river basins of India with its catchment spreading 

across international border covering part of Tibet. The basin is bounded by 

China and part of Dibang valley, Chenglong district of Arunachal Pradesh in 

the north district of Arunachal Pradesh (Burhi Dihing sub-basin) in the South 

China and hills of Myanmar in East and Assam State and a part of Dibang 

district in the west. The Lohit river, a tributary of Brahmaputra river, rises at 

an EL 6190 m above MSL from the snow clad peaks in Eastern Tibet and 

enters India through Kibithoo area of the district. The Lohit river in the upper 

reaches is known as Krawnaon and after flowing westwards, joins tributary 

called Chalum Susning flowing from Indo-Burma Border. The combined flow 

is known as Tellu or Lohit river. 

The catchment area is mostly tropical wet season and support dense mixed 

forest. The area is characterized by hills with steep gorges and deep rugged 

valleys of dentritic pattern with streams feeding the tributaries of the Lohit river 

system of which Tidding is the major one. The rivers are Turbulent with steep 

gradients. Water falls and rapids are very common in these rivers. The 

catchment area of Lohit River including the Tibet region is 29,487 sq km. The 

catchment area in Tibet has been estimated as about 15,034 sq km and this 

is entirely in high altitude snow clad rain fed area. The total catchment area 

3-1


upto the proposed dam site is estimated as about 16,500 sq. km. The river 

bed level at the proposed dam site is around El 924.0 m. 

The river Lohit is a parental river with its main source being snow melts of 

Himalayan glaciers and other small sreams. During the lean season i.e. from 

November to March every year there is a drop in discharge. The Lohit river 

offers good sites for hydro power development. The regulated discharges 

from the storage at Kalai Dam on the Lohit river is diverted through tunnels 

back to the Lohit river in the same basin for utilizing a gross head of about 

235 m for hydro power generation. The dam is located at Lat. 27 o 56’ 30” N 

and Long. 96 o 58’ 15” E. 

The Gross and Live Storage of the Kalai Storage reservoir are 1160.43 M 

cum and 909.74 M cum with FRL at El 1160.0 m and MDDL at El 1054.0 m 

respectively. The Kalai dam on river Lohit shall be an Earth & Rockfill dam 

with gated chute spillway on the right bank and a separate diversion structure 

for diverting a regulated discharge of 1497 cumec through 5 nos. each1.0 km 

long 10.0 m dia Head Race Tunnel to the 8.0 m dia vertical shafts bifurcating 

to 5.6 m dia leading to the turbine generating 2600 MW power (10 x 260 M) in 

underground power stations located on the right bank of the Lohit river. 

3.2 CLIMATE 

The climate of the region varies with altitude. The climate of the Lohit basin in 

the lower elevation is highly humid and intense cold in the higher elevations. 

From late November to early March winter prevails whereas pre-monsoon 

season is from March to May. June to October months are monsoon period. 

The nearest meteorological observation centre is at Mohanbari Airport 

Diburgarh, Assam. The maximum and minimum temperature at TEZU, the 

district headquarter varies between 3 o C to 45 o C. The rainfall varies 

3-2


considerably in the basin. At Tidding, the average annual rainfall is maximum 

and is 4996 mm, but at Yatong it is the lowest and is only 2519 mm of the 

annual rain. The basin has an average rainfall of over 3800 mm. About 52% 

of the total annual rainfall occurs during monsoon. 

3.3 SOCIO-ECONOMIC PROFILE 

Arunachal Pradesh attained its statehood on 20 th Feb., 1987. The State is 

situated between snow capped mountains in the North to the plains of the 

Brahmaputra valley on the south. It is a hilly state interspersed among deep 

valleys & narrow gorges. Arunachal Pradesh has been bestowed with 

abundant rain fall, and natural unspoilt scenic beauty and deep green lush 

forest wealth. The undulating topography predominates the state with highest 

peak ‘KANGTE’ rising to El 7090 m in the west Kameng district. The rainfall is 

highly variable 

The geology, soil texture and climate are highly variable including the 

habitation pattern. The state has sparse and scanty population with small 

sized villages scattered on the hilly land scape. 

The State is divided into 13 administrative districts with 3237 villages spread 

over an area of 83,743 sq. km. More than two thirds of the area has forest. 

Substantial part of the state is covered by mountain except for the strip of 

land, most of which adjoins Assam. Arunachal Pradesh is an agricultural 

state with 85% population engaged in Agriculture, forest produce and mineral 

resources. Besides agriculture, the bulk of the economy in connected directly 

or indirectly with forests and forest produce. 

3-3


The population density is 13 persons per sq. kms, lowest in the entire north 

east region as compared to 324 persons / sq. km of all India. Schedule Tribe 

(ST’s) constitute 79% its population. 

The average literacy rate is 54.74%. The male literacy rate being 64.07% 

and female literacy rate only 44.24% of the population. The sex ratio is 901 

females to 1000 males. The per capita income by 1998-99 estimate at 1993- 

94 prices in Rs. 8401.0. 

As regards rural electrification about 2316 villages out of 3649 in habited 

villages have been electrified (1991 Census). The per capita energy 

consumption in Arunachal Pradesh is 68.61 units as compared to 354.75 units 

of the national average. 

3-4

CHAPTER-IV 


TOPOGRAPHIC AND GEOTECHNICAL ASPECTS 

4.1 TOPOGRAPHY AND PHYSIOGRAPHY 

Gently sloping alluvial plains of Brahmaputra with thickly covered terraces and 

alluvial fans occupy the southern part whereas towards north a rugged 

topography with NW-SE trending hills is discernible. The area is mainly 

drained by Tellu River and its tributaries of which Foti, Kulung Ti, Shangti and 

Tawang are the major ones. The rivers are turbulent with steep gradient and 

therefore offer poor facilities for communication. Water falls and rapids are 

very common. The drainage pattern in the area is sub-parallel to dendritic 

nature. 

4.2 REGIONAL GEOLOGY 

The present area of study forms geologically a critical zone of northeastern 

Himalayas, as it constitutes a part of the eastern syntaxial bend. The area is 

occupied by both para and ortho metamorphics. The Gondwana rocks and 

Tertiary Group of rocks which are present in the west i.e. the Dibang and 

Dihang valleys are absent in this area. Some recent terrace deposits along the 

banks of river Lohit or Tellu are noticed. The para and orthometamorphites 

represented chiefly by marble, hornblende schist, garnetiferous biotite gneiss, 

kyanite-sillimanite-garnet-biotite gneiss, biotite gneiss, augen gneiss, quartzo 

felspathic gneiss, dioritic gneiss, granodiorite, leuco gneiss and amphibolites. 

Dioritic gneiss occupies the major part of the area. It is intruded by norite, 

metabasics, amphibolite, ultramafics and by veins of quartz, aplite and 

pegmatite. Hornblende schist and gneisses occur as bands, lenses and rafts 

within the dioritic gneiss which indicates dioritic gneisses are intrusive in 

4-1


nature and younger than gneisses and hornblende schists. Specks and 

veinlets of basemetal sulphides are noticed in dioritic gneiss, and pegmatites. 

Strike of the rocks in the area is NW-SE, which is in harmony with the strike of 

the Himalayan ranges right from the Dihang, Brahmaputra to SE. 

Systematic Geological mapping carried out by Eshwara et al (1989) area 

revealed the following stratigraphic succession in the area. 

Terrace deposits 

Assorted to poorly sorted granules to boulders 

dominantly of granodiorite, dioritic complex 

gneiss and vein quartz. 

Intrusives Meta-norite, metabasics, amphibolite, 

ultramafics, pegmatite, aplite and quartz veins. 

Crystallines or Granodiorite diorite gneiss, leuco gneiss. 

Orthometamorphites 

Para Metamorphites 

biotite 

Marble, hornblende schist, garnetiferous 

Gneiss, kyanite, sillimanite garnet biotite gneiss, 

Quartzo felspathic gneiss augen gneiss. 

A total no of eight marble bands occurring within the diorite gneiss are 

recorded between Yasong and Walong. The maximum thickness of the band 

is 30m. and minimum is 5m with a cumulative thickness of 60m. The rock is 

massive, moderately hard and fine to coarse grained. The marble band south 

of Satti village shows sacchroidal texture. 

Metanorite is fine to medium grained purplish rock occurring as a big intrusive 

body in dioritic gneiss between Kuibang and Khrang and interpreted that it 

4-2


continues towards south east upto Walop. In the east its contact with diorite 

gneiss continues down southwards from Mitikunang. This body could not be 

seen around Halothrong. A number of its apophyses and tongues of variable 

dimensions are seen in the diorite gneiss. Its intrusive nature within the diorite 

gneiss is indicated by presence of xenolith of dioritic country rock within it and 

also its tongues and apophyses in the dioritic gneiss. 

Number of quartz, aplite and pegmatite veins of variable thickness are seen 

cutting across the rocks both ortho and parametamorphites. Mostly they are 

seen to follow the dominant foliation direction. The number of pegmatitic veins 

are found to be more concentrated between Yasong and Walong, east of 

Hawaii. Pegmatite mainly consists of quartz, feldspar with subordinate amount 

of muscovite. Some of these veins contain specks of pyrite along the 

peripheral margins. 

Terrace deposits of thickness upto 50m are seen on the both east and west of 

the Tellu river. These generally consist of sand, gravel and boulders derived 

from the older crystallines. 

Systematic geological mapping of the area reveals that the crystallines viz. 

dioritic gneiss and granodiorite are intrusive into metamorphities viz. 

Hornblende schist, Kyanite- sillimanite – biotite gneiss and marbles which is 

clearly evidenced by the presence of the latter within the crystallines as bands, 

lenses and rafts. Nandy et al who worked previously in this area considered 

crystallines to be older to metamorphites and also felt that these crystallines 

have overridden the parametamorphites to the southwest along a thrust, which 

they called it as Lohit thrust. 

Further during the coarse of their work in the present area mapped Nandy et 

al recorded two bodies of norite separated by a fault but the present study 

4-3


disproves existence of any such fault and considers the norite body to be a 

single one. Mapping of the present area also revealed the occurrence of leuco 

gneiss which are intruded gneiss and this is evidenced by the presence of 

dioritic gneiss as xenoliths in the leuco gneiss. Authors interpret that this may 

be the later phase of the main crystalline complex. 

Bedding planes are recognized in the present area in the form of colour 

banding mainly in quartzites. Besides colour banding layering in the ultramafic 

rocks in the form of primary layers. 

Planar structures developed in the area are schistosity, gneissosity, joints and 

shears. Schistocity: It is regionally developed both in para and ortho 

metamorphites. Schistosity is well developed in hornblende schist, diorite 

gneiss, Kyanite sillimanite-garnet schist and gneissosity in biotite gneiss. 

The general trend of schistosity and gneissosity is NW-SE with moderate to 

steep dips towards SW and NE. 

Joints:- Joints are well developed in both para and ortho-metamorphites. The 

general attitude of the four sets of joints recorded in the area is enumerated 

below: 

1. N65°E - S65°W / 40° SE. 

2. N40°W - S40°E / 35° SW 

3. E - W / 70° N 

4. N - S / vertical. 

N-S and E-W trending joints mainly control the drainage of the area. 

4-4


Shear Zones: The effect of shearing is very conspicuous both in ultramafics 

and gneisses which resulted in numerous active slide zones with NW-SW 

trend. In augen gneiss and dioritic gneisses crushing and gneisses which 

resulted in numerous active slide zones with NW-SE trend. In augen gneiss 

and dioritic gneisses crushing and shearing have also been noticed. 

Folds: The area under study appears to have undergone three phases of 

deformation. The first phase of deformation resulted in the development of 

tight to isoclinal fold with rounded hinge. These folds represent thick hinge and 

thin elongated limbs. Their reclined and recumbent nature has been observed 

in many places. 

F1 Folds: These generally trend NE-SW to NNW-SSE with steep plunge 

towards NNW and SSE. These folds are observed south of Mehao lake and 

around Chingwanty as tight isoclinal and reclined folds trending ENE-WSW 

plunging SW. 

F2 Folds: These are moderately tight asymmetrical in their geometry. They 

show co-axial in nature with F1 folds but one limb is always shorter than the 

other with a slightly broader trough. S2 planes are generally parallel to 

regional schistosity except at hinge portion of F2 folds. Development of pucker 

lineation and local steeping of foliation are related to F2 deformation. 

F3 folds: These are broad open type with sub-vertical axial planes. They 

generally trend NE-SW having axes gently plunging towards NE or SW. 

Superimposition of F3 folds on F2 folds has resulted in the formation of domal 

and basinal structure in the different parts of the area. As a result doubly 

plunging nature of F2 folds are also noticed at Mehao Lake. 

4-5


4.3 GEOLOGICAL FEATURES OF THE PROJECT COMPONENTS 

The original dam site of the Kalai H.E. Project passes through one of the 

major two marble dykes with in dionite complex rock system which offer 

contact zone and require elaborate treatment for making this as part of type of 

geology foundation and could be guided for structural stability of the dam. 

Accordingly the dam site is shifted by about 6.8 km downstream and the 

marble dykes shall be properly investigated and treated for water lightness as 

it pass thorugh the reservoir body. The dam body at the new location is 

located in the Dioritic comples work system in both the banks. However rock 

is jointed and folded. The foliation plaves are dipping 60 o NW–SE to 70 o NW- 

SE and joints are trending N 30 o E / S 30 o W to N 40 o W / S 40 o E. 

As regards the power house location alternate studies could be made to avoid 

long tunnel as per the original planning studies in the remote area near 

international borders. With an alternative study with high head dam the power 

house could be as dam toe power house or with in the body of the dam. 

4.4 SEISMOTECTONICS AND SEISMICITY 

This area is part of complex tectonic province displaying juxtaposition of two 

Tertiary mobile belts. The E-W trending Himalaya and the N-S trending 

Arakan Yoma belt developed as a consequence of collision between Indian 

and Eurasian Plates and subduction of Indian Plate below Burma Plate. The 

Archean- Proterozoic cratonic elements of Maghalaya and Mikir hills. overlain 

by Cretaceous to Recent shelf/platform sediments locate between these 

mobile belts. 

The area around the proposed project encompasses eastern part of Arunachal 

Pradesh. southern part of China and eastern part at Tibetan Plateau (Narula 

4-6


et al. 2000). Northern part of the area is occupied by the Trans-Himalayan 

Tactogen with late to post tectonic granitoid batholiths. This is followed 

towards south in western part by ophiolite and excretionary complex of 

Tsangpo Suture Zone (TSZ). Further south, the Main Himalayan Belt (MHB) 

starts with poorly metamorphosed cover sequence of Tethyan Belt which is 

tectonically underlain towards south successively by high and low 

9radeasse~es of Proterozoic age. This Proterozoic package is interlayered 

With the Paleozoic cover sequence alongwith Basic volcanics. The Lohit 

Thrust, separating moderately metamorphosed sequence from the Granitoid 

Massif of Tuting and the Mishmi Thrust separating meta sediments of 

Himalayan Orogenic Belt from the Assam Shelf Sediments and Tiding Thrust 

are important structural elements of Mishmi Block . 

The area constitutes seismically active zone where occurrence rate of low to 

moderate size earthquakes is very high. In the region up to 30 N. about 87 

seismic events have been witnessed in a period of 64 years between 1929 

and 1993 among which the events with magnitude ranging from 4-4.9 

predominate. About 70% of whole population have depth < 40 km. Major 

concentration of seismic events is restricted to north eastern part of the area 

with two main clusters around Po Chu fault zone. Besides these some of the 

events scattered around Bame, Siang, Lohit & Tiding faults/thrust have also 

been observed indicating recent movements along these. Keeping in view the 

high seismic status, the area has been assigned to zone-V as per map of 

India showing seismic! zones (IS-1893 (part 1): 2002). It is recommended 

that suitable seismic coefficient keeping in view the high seismic status of the 

area be included in the design of appurtenant structures of the project. 

4-7

4.5 GEOTECHNICAL APPRAISAL 


The area around the proposed project exposes granodioritic-dioritic gneiss 

with intrusive basic and ultramafic rocks. The regional foliation trends NW-SE 

with moderate to steep dips towards NE and SW. These rocks may provide 

good foundation material in general. However, the weathered and sheared 

zones in basic and ultramafic intrusives may require extensive treatment. The 

type of diversion structure and its location will have to be decided after 

detailed inspection of site and also estimating the thickness of overburden in 

the river bed as well as on the abutments. 

It is suggested that possibility of locating intermediate adits may be looked 

into so that construction activities are facilitated. If required alignment of HRT 

may be changed slightly for this purpose. The 16 km. Long HRT without any 

provision for an intermediate adit is expected to have excessive rock cover in 

the middle reaches where problems due to locked-up stresses could be 

encountered. 

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

Lohit River which exposes granodiorite-dioritic rocks. At places, these rocks 

are highly sheared and fractured. It is suggested that the underground 

powerhouse be located at a suitable place after proper investigation and 

adequate space for locating its appurtenant structures be ensured. This 

geotechnical appraisal is based on the regional geological set up. 

4-8


CHAPTER – V 

HYDROLOGY 


The state of Arunachal Pradesh is situated on the North Eastern tip of the 

country and covers an area of 83,743 sq. km. East. Lohit basin is the eastern 

most river basin with its catchment spreading across international border 

covering part of Tibet and India. The total catchment area of Lohit basin 

including Tibet is 29,487 sq.km. In Tibet, the river drains an area of 15,034 

sq.km. Out of the remaining catchment area 14,453 km 2 in India, 

approximately 12,286 sq.km. is hilly and lies in Tinsukia, Changlang and 

Dibang districts while the rest is plain area. An index map of the basin shown 

at plate 5.1. 

Arunachal Pradesh is divided into five river valleys; the Kameng, the 

Subansari, the Siang, the Lohit and the Tirap. All these are snow fed rivers, 

originate from Himalayas. Lohit basin is the easternmost river basin of India. 

The Lohit river rises from the snow covered peaks of the Nimbout Chcumbouri 

Nechi Gongra Tirap Phasi ranges in the Eastern Tibet at an elevation of 6190 

m. The Rongtho-chu is the principal source of Lohit and is joined by various 

tributaries namely Zayal-chu, and Krawnaon and Chalum Susning. The 

combined flow of these rivers are known as Tellu. It is joined by other major 

tributaries and the combined flow emerges out of the gorge at Brahmakunda 

in India. The Lohit River after crossing the Sadiya town in Assam is joined by 

Dibang and Dihang river near Kobo. The combined system flows are then 

known as Brahmputra river. The Lohit river has a length of 413 km from its 

source in Tibet to its confluence with the Dihang near Kobo. Out of 243 km 

5-1


length in India, 111km lies in the hilly terrain and the balance of 132 km lies in 

the plain. 

The Department of Power, Arunachal Pradesh have identified 18 Nos. of 

small/mini/micro power schemes in Lohit basin. The probable potential of 

these schemes is 32,327 KW and the capacity ranges from 150 KW to 7500 

KW. 

There is no existing major/medium irrigation scheme in the Lohit basin. 

However, there are 68 Nos of existing/ proposed minor irrigation schemes in 

the basin. The CCA of these schemes is 3908 ha while the utilisation of 

irrigation potential is 49% only. 

Some ground water schemes have also been identified in the basin whose 

details are not available at present. 

5.2 DATA AVAILABILITY 

5.2.1 Rainfall Characteristics 

The Lohit basin falls within the climatic zone-II and III consisting of North and 

North-East India, Tibet and southern parts of China. An area of 15,034 sq,. 

km. lies in China/Tibet and no hydrometeorological data (including snow 

bound area) is available for this part of the basin. For hydrological studies, 

only the data available within Indian territory has been taken into 

consideration. The average annual rainfall is over 3800mm. 

There are 16 raingauge stations in Lohit basin maintained by IMD (3 Nos) as 

well as by State Govt. (13 Nos.) whose data is available for varying periods. 

The rainfall data in respect of these stations have been collected from the 

5-2


respective sources / available reports. As indicated in the earlier paras, no 

information is available for rainfall details in Tibet region. The proposed Kalai 

H.E. Project lies in upper reaches where no raingauge station exists. The 

rainfall data, thus available do not represent the catchment rainfall for the 

project basin. 

5.2.2 Gauge and Discharge Data 

There are several G&D sites maintained by CWC in the Brahamputra basin. 

CWC has been requested to supply the 10-daily discharges for the following 

six sites along with the flood peak for carrying out the hydrological studies of 

the proposed Kalai H.E. Project. 

1. Hayuliang on Lohit River 

2. Teju on Lohit River 

3. Dhaula bazar in Lohit Basin 

4. Mompani on Lohit River 

5. Nepali Basti on Lohit River 

6. Walong on Lohit River 

The Brahamputra Board has also been observing the discharges of river Lohit 

and tributaries since 1984. The details of the data available are as under: 

S. 

No. 

Name of the Sites River/stream Data Availability 

1. Nepalibasti/Alubarighat Lohit Intermittent 

2. Mompani Lohit 1985 to 2000 

3. Hayuliang Lohit river 1984 to 94 

4. Walong Lohit River 1996 to 98 

5. 32 Mile 32 Mile Nallaha 1996 to 98 

5-3


S. 

No. 

Name of the Sites River/stream Data Availability 

6. Lohitpur Tapang Nallaha 1996 to 98 

7. Digaroo Digraoo River 1996 to 98 

8. Khrem Berang river 1996 to 98 

Since the data available for most of the sites are of very short duration and 

those at Alubarighat are intermittent and as such are not suitable for 

hydrological studies and hence has not been considered. However, data of 

Mompani and Hayuliang have been considered for the hydrological studies. 

The hydrological data requested from CWC because certain constraints could 

not be supplied so far. However, the G&D data for 2 G&D sites as indicated in 

the Table below has been taken from the project reports prepared earlier. 

Considering the priority for the PFR report preparation, the same is utilised 

for hydrological studies after checking the consistency and reliability. 

S. 

No. 

Station Name Period Catchment Area 

(sq. Km.) 

1. Hayuliang 1950-1962 to1983- 1994 19,100 

2. Mompani 1985-98 20,560 

5.3 UTILISATION 

Utilisation of surface water in Lohit Basin is for domestic and industrial use 

only. The utilisations in upper reaches of the proposed Kalai H.E. site are 

negligible and as such have not been accounted for while assessing the water 

availability for the proposed Kalai H.E. project. 

5-4

5.4 DATA ANALYSIS 

5.4.1 Check For Consistency Of Data 


The monthly catchment rainfall for Hayuliang and Mompani G&D stations 

together with the proposed project site could not be worked out because no 

rainfall details of raingauge stations in Tibet are available. The raingauge 

station data as available from IMD and State Government department does 

not represent the catchment rainfall even within the Indian Territory. 

Moreover, the location and distribution of raingauge stations in Indian Territory 

do not reflect fully the orographic characteristic of the basin. 

The observed concurrent discharges at Hayuliang and Mompani G&D sites 

were compared for their consistency and reliability. It was noticed that the 

annual specific yield at Hayuliang was 1.641 Mm 3 /sq. km. against 1.949 

Mm 3 /Sq.km at Mompani. The annual specific yield at Mompani is higher than 

Hayuliang due to the fact that Mompani intercepts an additional area of a 

major tributary originating in India and whose rainfall pattern is different from 

the rest of the Mompani catchment. The monthly and annual specific yields of 

both the G&D Sites are as under: 

Site 

Name 

Jan. Feb Mar April May June July Aug Setp Oct. Nov. Dec. Annual 

Hayuliang 0.048 0.043 0.067 0.111 0.183 0.238 0.286 0.226 0.173 0.129 0.080 0.057 1.641 

Mompani 0.053 0.055 0.099 0.147 0.221 0.263 0.297 0.247 0.198 0.184 0.111 0.074 1.949 

Further, The observed discharges at Hayuliang and Mompani were checked 

for their consistency based on double mass curve technique for the three 

season; viz monsoon, non-monsoon and on annual basis. From the mass 

curves, it can be inferred that the discharges observed at both G&D sites are 

consistent. Since the Hayuliang G&D site is close to the proposed Kalai 

Project site and its data is found to be consistent, it would be more 

5-5


appropriate to consider this data for hydrological studies for the proposed 

project. 

5.5 METHODOLOGY ADOPTED FOR YIELD ASSESSMENT 

The proposed Kalai H.E. Project intercepts an area of 16,500 sq.km out of 

which 15,034 sq.km lies in Tibet. As indicated in earlier paras, no hydrometeorological 

details are available for the catchment area lying in Tibet. It is 

presumed that most of the area in Tibet is snow bound which will yield run off 

when the snow melts and constitute the base flow for flood studies only. 

Since Hayuliang G&D site is nearer to the proposed Kalai H.E. project site 

and its data is consistent the same is considered for hydrological studies. 

Based on the consistency checks made in the run off data at Hayuliang and 

Mompani G&D sites, the following methodology has been adopted to compute 

the long-term yield series at Hayuliang and at proposed dam sites as under: 

a) As indicated earlier, the missing gaps in the monthly discharge data at 

Hayuliang G&D site has been filled using the standard procedure and 

maintaining the mean and standard deviation. 

b) The concurrent monthly discharge data of Mompani and Hayuliang 

G&D sites (1985-94) were utilised to extend the runoff data of 

Hayuliang G&D site for the period 1995-99 by developing the monthly 

correlation by Langbein’s method. The monthly run off series for the 

period 1983-99 has thus been developed at Hayuliang G&D site. 

c) The monthly run off series developed at Hayuliang G&D site for the 

period 1983 to 1999 has been transferred at the proposed Kalai H.E. 

Project on the catchment area proportion basis. The yield series 

obtained at Kalai H.E. Project site is given at Annexure 5.1. 

d) The dependable yield at Kalai H.E. site are as under:- 

5-6

5.6 DESIGN FLOOD 

90% Dependable yield =. 19018.2 MCM 

75% Dependable yield = 25737.3 MCM 

50% Dependable yield = 31982.4 MCM 

Average yield = 30179.9 MCM 


The proposed Kalai H.E. Project is a storage scheme located on Lohit River. 

The scheme intercepts an area of 16,500 sq.km. The short-term rainfall/storm 

and concurrent discharge data at proposed dam site or in the neighboring 

catchment is not available. As such, unit hydrograph based on the observed 

data cannot be developed. Further, peak flood discharges are not available at 

the proposed project site. The peak flood discharges for 1987 to 2000 (14 

years) are available at Mompani and from 1986-1994 (9 years) are available 

at Hayuliang G&D site on Lohit River. The flood frequency analysis has been 

made at Mompani G&D site (CA=20,560 km 2 ). It is also proposed to estimate 

the design flood based on unit hydrograph principle indicated in Flood 

Estimation report for South Brahamputra sub-zone 2(b), (revised) prepared by 

CWC. The flood estimation report for sub-zone 2(c) in which the proposed 

project is identified is not available hence the same could not be utilised. 

5.6.1 Unit Hydrograph Approach 

Central Water Commission had carried out regional flood estimation studies 

for major tributaries in South Brahmaputra Basin on the basis of discharge 

and storm rainfall data collected for the flood periods. The hydrological 

studies were carried out in 1984 and were based on rainfall run off data of 14 

catchments. Subsequently, additional data in respect of 5 sites were also 

collected and accordingly, CWC revised their studies in March, 2000. 

Representative unit hydrograph of one-hour unit duration have been 

5-7


developed at each gauge site. The physiographic parameters of the 

catchment and the parameters that describe the unit hydrograph have been 

correlated by regression analysis and the equation for synthetic unit 

hydrograph for 1-hour duration have been developed. The same parameters 

have been utilised for deriving synthetic unit hydrograph at Kalai H.E. site on 

Lohit river. 

The total catchments area of Lohit river above Kalai H.E. project site is 16,500 

km 2 and the snow fed area is 15,034 km 2 . The entire snow fed area lies in 

Tibet for which no data is available. For deriving the unit hydrograph at the 

Project site only the rainfed area 1466 km 2 is considered. The snow part 

contribution has been added to the base flow. 

5.6.2 DESIGN STORM 

Due to meager hourly rainfall data available, detailed storm analysis for Lohit 

river at Kalai H.E. project site is not possible at this stage. The same will be 

considered at DPR stage. 

However, 1-day, 2-day, 3-day maximum rainfall at 13 numbers of raingaugue 

stations of the sub-basin have been analysed according to the variation in 

intensity of rainfall. 

Yetong raingauge station is close to the catchment of the proposed Kalai H.E. 

Project. On examination of the storm rainfall data, it is seen that the 

maximum 1-day rainfall of 309 mm is recorded at Yetong raingauge station. 

Hence, the 1-day maximum rainfall of 309 mm is considered for the estimation 

of design flood. 

5-8


The clock hour correction 13% has been considered. In the absence of dew 

point data, the moisture maximisation factor could not be worked out. The 

factor has been assumed as 30% in the flood analysis for the propose of prefeasibility 

studies. The design loss rate of 3.5 mm per hour as recommended 

in the flood estimation report of the CWC has been adopted. 

The base flow in the snow fed area has been considered as 0.11 cumecs per 

sq. km while that in snow free area as 0.05 cumes per sq. km, 

5.7 FLOODS 

5.7.1 Standard Project Flood And Probable Maximum Flood 

Since the Kalai H.E. Project is a storage scheme, it envisages the 

construction of 70 m. high lifting dam. As per BIS code No. 11223-1985 the 

spillway is to be designed for a probable maximum flood or 1000 year flood, 

which ever is large. The probable maximum flood (PMF) of 7487 m 3 /sec. has 

been estimated taking into account the design loss rate, base flow and the 

moisture maximisation factor as indicated in the above paras. The Standard 

Project Flood (SPF) of 5965 m 3 /sec has also been estimated. The detailed 

computations in respect of the design flood by synthetic unit hydrograph 

method. 

5.7.2 Flood Frequency Analysis 

The flood Frequency analysis is one of the most important functions to 

interpret the past records of correlated hydrological events such as discharge, 

flood level etc. in order to evaluate the future probabilities of such 

occurrences. The estimation of the frequencies is essential for quantitative 

assessment of flood problems. The knowledge of the magnitude and 

5-9


probable frequencies of such flood is also required for the proper design and 

location of hydraulic structures and for other allied studies. 

The discharge data, which are random variable, follow the law of statistical 

distribution. After the study of distribution of random variables and its 

parameters e.g. mean, standard deviation, etc. using the theory of probability, 

one can reasonably predict the probability of occurrence of an event within 

given interval. The method of estimation of the parameters and the 

interference of the statistical distribution are very important in this regard. 

The flood frequency analysis at Mompani G&D site on Lohit river, using the 

flood peak data for 14 years from 1987 to 2000 has been carried out. 

Statistical checks such as outlier test, Chi-square test, Stationarity test and 

Randomness test have been made before using the data in the analysis. 

Based on the statistical checks made, it is seen that Gumbel’s distribution and 

Log-Pearson Type III distribution fit. As such, these two distributions have 

been used for estimating flood values for various return period. The flood 

values for 100 year, 500 year and 1000 year return period at Mompani site 

are given below: 

Return period 

Flood Value (m 3 /sec) 

Gumbel’s Distribution Log Pearson Type III 

distributions 

100 Yr. 9492 8304 

500 Yr. 10,900 9300 

1000 Yr. 11,736 9700 

5-10


The above flood values have been transferred to the Kalai H.E. Project site 

based on the catchment area proportion to the ¾ power (CA at the project 

site/CA at Mompani G&D site). The results are given below: 

Return period 

Flood Value (m 3 /Sec) 

Gumbel’s Distribution Log Pearsson Type III 

Distribution 

100 yr. 8048 7041 

500 YR. 9243 7886 

1000 YR. 9951 8226 

5.8 RECOMMENDATIONS OF DESIGN FLOOD 

Since the data observed at Mompani G&D site is available for 14 years only, 

which is not sufficient for the estimation of flood by Frequency Analysis, the 

above values have been enhanced by 20% for the purpose of pre-feasibility 

studies. The enhanced flood values for the various return periods are as 

under: 

5.9 SEDIMENTATION 

Return Period Flood Value 

(m 3 /Sec.) 

100 yr. 9660 

500 YR. 11,090 

1000 YR. 11,950 

Since the Kalai H.E. Project envisages the construction of 70 metre high dam 

and the gross storage capacity is more than 60 Mm 3 , the sedimentation 

studies are required to be carried out as per I.S.11223-1985 code. As per the 

5-11


code, the new zero elevation after 70 years of silting in the reservoir and the 

area capacity after 25 years of silting are required to be estimated. 

The sediment data observed at Mompani on Lohit river is available from 1977 

to 1987. Based on this observed sediment data, the average annual silt load 

works out to 210.647 ha.m. Considering the bed load as 15%, the average 

annual silt rate at Mompani is estimated of the order of 0.012 ha.m / sq.km. 

The gross storage capacity is 1160.43 Mm 3 at FRL 11160 m. The bed level at 

the dam is 924 m. The depth of reservoir vs capacity when plotted on log-log 

paper confirms the reservoir as Type-III (hill). The total catchment area 

above Kalai dam site is 16,500 sq.km and the snow area is 15,034 sq.km. In 

the absence of information about the sediment contribution from the snow 

area, it has been assumed that the sediment will flow in the river from the 

snow free area (1466 sq.km) only. However, the sedimentation studies have 

also been carried out considering the entire catchment area (16,500 sq.km). 

The results of studies for the two alternatives in respect of estimation of new 

zero elevation after 70 years of silting in the reservoir and the reduction in 

gross storage capacity after 25 years of silting in the reservoir are as under: 

Altternative I Snow Free Area 1466 Sq.km 

Bed level 924 m 

New Zero Elevation (70 years) 1001.3 m 

FRL 1160 m 

Gross storage capacity after 25 years silting 1110.94 Mm 3 

Original gross storage 1160.43 Mm 3 

The above studies are meant for pre-feasibility purposes. The entire 

sedimentation studies will be revised based on the sediment data collected at 

Kalai dam site, at the DPR stage. 

5-12

5.10 LIMITATIONS 


i) A G&D site needs to be established near the proposed Kalai H.E. project site. 

The daily gauge and discharge data alongwith the hourly gauges in the flood 

season for few years need to be observed for realistic assessment of water 

planning and the design flood. 

ii) A self-recording raingauge station and snow gauge needs to be established 

within the project area. 

iii) Hydrometeorological data, details of utilisation, land use characteristics, 

details of power development and Irrigation development for the catchment 

area lying in Tibet need to be collected for the realistic hydrological analysis at 

DPR stage. 

5.11 OBSERVATIONS OF CWC 

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

04. The observations received from CWC on the hydrological studies of this 

project & replies for above observations submitted by WAPCOS are enclosed 

as Appendix 1.1 – 1.2. 

5-13


CHAPTER-VI 


CONCEPTUAL LAYOUT AND PLANNING 

Kalai H.E. project envisages the construction of a 450 m long and 241m 

(above the deepest river bed level) high earth and rockfill dam located at 

longitude 96 o 58’ 15” E and latitude 27 o 56’ 30” N with FRL at 1160.0 m 

across Lohit river a tributary of Brahmaputra near village Kumblung on the 

left bank of the river. The river bed level at the proposed dam location is 924 

m (approx.). The under ground power house is proposed by the side of the 

power dam on the left bank of the river. The project envisages the utilization 

of the maximum gross head of 235 m and live storage of 909.74 M cum 

between MDDL & FRL to generate hydro-power with installed capacity of 

2600 MW (10x260 MW). 5 nos. Tailrace tunnels each of average length of 

1.76 km discharges the water back into the river Lohit. 

6.2 CEA ASSESSMENT STUDY 

As per re-assessment studies carried out in CEA, Kalai Lifting Dam Scheme 

forms the first hydro-electric project on the main Lohit river involving a 70 m 

high diversion dam at a site where the river bed level is +1030 m. The 

diverted waters are proposed to be taken through 16 km long tunnels to a 

power house located on the right bank of the river with tail race water level of 

+760 m and utilise the available gross head of 310 m for generation of 674 

MW of firm power. The optimum installed capacity of the power house 

proposed is 2550 MW. 

6-1


The proposal of CEA was studied in detailed and found that the water 

conductor system is about 19.685 km against 16 km as envisaged by CEA in 

their proposal. Since Lohit river carries high discharges even during lean 

period, so the number of tunnels to carry the design discharge for power 

generations are supposed to be of the order of 6 to 8 numbers that too with 8 

to 10 m dia tunnels. Also 3 nos adits are required to be constructed having 

length 9 to 10 km each to approach the HRT. This may result in construction 

problem. So, WAPCOS made an alternative comprehensive studies to arrive 

at a best suited proposal to tap the maximum power generation on Lohit river. 

6.3 ALTERNATIVE STUDIES 

Alternative studies were carried at three different locations for diversion dam, 

namely alternative 1, 2, & 3 on Lohit river with corresponding different 

alignment for each of these sites were identified. The layouts of diversion sites 

No. 1,2 & 3 along with , tunnel alignments and power houses are shown in 

Plate No. 6.1. The details of the above alternatives are discussed as under:- 

6.3.1 Alternative-I 

In this alternative four different studies with various dam heights ranging 

between 45 m and 180 m were carried out for a site where the river bed level 

is 995 m. The power house is kept at the same location as in CEA’s 

reassessment studies with tail-race water level of + 760 m. However, the 

water is proposed to be diverted to the powerhouse through 8 nos. of tunnels 

each of 25.0 km in length (approx) (total length 200 km approx.). 5 nos. 

construction adit tunnels are proposed to execute the work of water conductor 

system. 

6-2

i) Study-I 


A storage dam 105 m high above river bed level with FRL and MDDL at 1100 

m and 1055 m respectively has been considered. This will provide a live 

storage capacity of 150 M cum between FRL and MDDL. The available gross 

head under this proposal is 325 m and would generate firm power of 568 MW. 

ii) Study-II 

A storage dam 150 m high above river bed has been considered which will 

provide a live storage capacity of 425 M cum between FRL and MDDL kept at 

1150 m and 1055 m respectively. The available gross head under this 

proposal is 359 m and would generate firm power of 731 MW. 

iii) Study-III 

A storage dam 180 m high above river has been considered which will provide 

a live storage capacity of 650 M cum between FRL and MDDL kept at El 1175 

m and El 1055 m respectively. The available gross head under this study 

would be 375 m to generate firm power of 836 MW. 

iv) Study- IV 

A run-of-river type diversion dam with maximum height of 45 m above river 

bed has been considered. The FRL and MDDL has been kept at 1040 m and 

1026 m respectively providing a live storage capacity of 17 M cum. The 

available gross head under this study is 279 m to generate firm power of 480 

MW. 

6-3


The alternative-I and its four no. studies carried out are not feasible as there is 

a fault zone near this alternative and also the length of tunnels are very large 

about 200 km long (8 nos. 25 km each throughout) 

Another alternative study was carried out by shifting the dam site down 

stream and power house site upstream to reduce the length of water 

conductor system. 

6.3.2 Alternative-II 

The alternative-II is located about 6.8 km downstream site no. 1 near Kryl 

spring where the river bed level is at El 924 m. The powerhouse location has 

been shifted about 7.8 km upstream with respect to site under alternative I 

studies, to a place near Matrong village. Two studies were carried out with 

different dam heights of 150 m & 180 m at this location. The water is 

proposed to be diverted to the power house through 8 no. tunnels each of 

14.0 km (approx) in length (total length 112 km approx). Under this proposal 2 

nos. construction adit tunnels have been considered to execute the work of 

water conductor system. The tailrace water level at the powerhouse under this 

study has been computed as 795 m. 

i) Study-I 

A storage dam 150 m high with FRL and MDDL at El 1075 m and El 985 m 

respectively has been considered. The live storage capacity between FRL 

and MDDL is 425 M cum. The available gross head under this proposal is of 

the order of 250 m and would generate firm power of 435 MW. 

6-4

ii) Study-II 


A storage dam 180 m high with FRL and MDDL at El 1105 m and El 985 m 

respectively has been considered. The live storage capacity between FRL 

and MDDL is 650 M cum. The available gross head is of the order of 255 m to 

generate firm power of 568 MW. 

Another alternative study was carried out by shifting the further Downstream 

to reduced the length of water conductor system. 

6.3.3 Alternative-III 

In this alternative the diversion site is located about 6.6 km further 

downstream of alternative 2 near Menjang village where the river bed level is 

at El 885 m. Two studies were carried out with dam heights of 150 m and 180 

m respectively. The water is proposed to be diverted to the power house 

through 8 nos. tunnels each of 9.0 km in length (Total length 72 km). For 

execution of water conductor system only one adit tunnel has been 

considered. The power house location and tail water level under this study are 

same as proposed in alternative-II. 

i) Study-I 

A storage dam 150 m high above river bed with FRL and MDDL at El 1035 m 

and 935 m respectively has been considered. The live storage capacity 

between FRL and MDDL is 425 M cum. Available gross head under this 

proposal is 207 m and would generate 473 MW of firm power. 

6-5

ii) Study- II 


At this site, a storage dam 180 m high with FRL and MDDL at El 1065 m and 

935 m respectively has been considered providing a live storage capacity of 

650 M cum. The gross head under this study is 227 m which would generate 

firm power of 518.23 MW. 

6.4 CONCLUSIONS 

Perusal of the above studies indicate, that if project features as mentioned 

under alternative-I are adopted with dam height of 150 m / or 180 m, the 

optimum installed capacity at the powerhouse will vary between 3600 MW to 

3800 MW. However, the length of water conductor system with 8 nos. of 

tunnels of 25 km each running parallel from diversion site to powerhouse will 

be very high (amounting to total length of 208 kms). Such an exorbitant length 

of tunnels will not only be costly and time consuming but may also face 

serious construction problems. Besides the dam site is also located very close 

to a fault zone comprising two major marble dykes with its dionile complex 

rock system and may require elaborate foundation treatments. As such these 

proposals are not found feasible. 

If project feature as indicated under alternative-II are adopted i.e. shift the 

dam site 6.8 km downstream from its location as considered under 

alternative-I and shift the powerhouse 7.8 km upstream from its earlier 

location, the length of water conductor system will reduce by about 44% as 

compared to Alternative I but loss in gross head may be of the order of 30% 

and thus reducing the generation by the same amount i.e. installed capacity 

ranging from 2500 MW to 2700 MW. 

6-6


Finally, if project features of alternative-III are adopted, i.e. shift the diversion 

site further 6.6 km downstream from the location under Alternative-II, but 

retain the power house location as per study 2, the length of water conductor 

system will reduce by 64% as compared to length of tunnels indicated under 

Alternative I, but loss of gross head would be of the order of 40%. The 

optimum installed capacity will range between of 2200 MW and 2300 MW. 

Keeping in view the topography and geological conditions, it can be inferred 

that a high storage dam can safely be constructed to tap the hydro-electric 

potential at a site. (Close to Alternative II) & hence a dam toe u/G power 

house at dam site-II is finally adopted. 

6.5 The features of above various conceptual planning were discussed with the 

Chief Engineer (HP&I) and other officers of CEA on 10 June 2004, and it 

was decided that as tunnel alternatives involve very large lengths of water 

conductor system, it will be advisable to plan for a high dam and underground 

power house. This will reduce the length of tunnels to a large extent. During 

the discussion it was decided that the total head available at Kalai & Hutong 

HE Scheme be suitably tapped by construction of two nos rock fill dam. 

6.6 Accordingly the studies are carried out for a dam and underground power 

house increasing dam ht. to 241.0 m and utilizing a firm head of 192.29 m. 

This scheme is very attractive as it reduces the tunnel length to negligible as 

compared to tunnel length of 200 km, 112 km, & 72 km of 8.0 m dia for 

alternative I, II & III & generate firm power of 509.44 MW with Installed 

Capacity 2600 MW planning of the proposed scheme is discussed here 

under. 

6-7

6.7 RIVER DIVERSION WORKS 


6.7.1 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. 

6.7.2 Five diversion tunnels of 9.0 m diameter horse shoe type and about 2.2 km 

are proposed along right bank to divert the discharge of 9660 cumecs (in 100 

years return period flood) for the construction of dam & appurtenant works. 

The diversion tunnel inlet is proposed to be provided with a gate of size 9.5 m 

x 9.5 m which will be operated by means of a rope drum hoist for purposes of 

closure of the diversion tunnel. 

The upstream coffer dam is proposed as earth and rockfill of appr. 41 m high 

and will have 10 m top width, and u/s slope 2.5 (H): 1(V) and d/s slope 1:8 (H) 

: 1(v), with a central impervious core extended up to top of the coffer dam. 

The upstream coffer dam is planned in such away that during execution of the 

main earth and rock fill dam, the u/s slope will match with the main dam slope 

and subsequently this coffer dam shall be come a part of the main dam. 

The down stream coffer dam is at about 750 m d/s of main dam axis and will 

be of 20 m high in earth and rock and rock fill section. 

6-8

6.8 DIVERSION DAM 

6.8.1 General 


A 241 m high (above deepest river bed level) earth & rockfill dam is proposed 

as the storage structure near Kryle village on river Lohit. The dam is proposed 

to be located at Latitude 27 o 56’ 30” N and Longitude 96 o 58’ 15” E. The 

length of dam is 450 m with 96 m with chute spillways of length 800 along with 

one tunnel spillway of 10 m dia and one morning glory of 7 m dia. 

The proposed dam shall have FRL at El 1160.0 m maximum water level at El 

1163.0 and MDDL at El 1054.0 m. The top of dam is kept at EL 1165.0 m with 

provision for computed freeboard of 5.0 m above FRL. The proposed dam 

shall have a submergence area of 1296.7 ha at FRL and a live storage of 

909.74 M cum between FRL and MDDL. 

6.8.2 Earth & Rock fill Dam 

About 480 m length of the main dam will be earth & rockfill section with an 

inclined imperious core and a maximum height of 241 m provided across the 

main river. The upstream slope of 2.5 (H) :1(V) from EL 924.0 m to EL 1100 m 

and 2.25 (H) : 1( (V) beyond EL 1100 m to top of dam. The down stream 

slope is 2.2 (H) : 1(V) from EL 924.0 m to EL 1100 m and 1.8 (H) : 1(V) 

beyond EL 1100 m to top of dam. 

The top level of earth and rockfill dam has been kept at El 1165 m. The top 

width is kept as 10 m. considering the limitations of availability of impervious 

material in the project area an inclined impervious core with upstream and 

downstream slopes of 1.65 (H) to 1(V) and down stream slopes 1.25 (H) to 

1(V) is proposed with top width of 7.0 m. The top of core section is kept 1.0 m 

6-9


above the MWL. A graded inclined filter 2.0 m thick is provided in the 

upstream & downstream face of impervious core followed by horizontal filter 

near the base to drain seepage water through the longitudinal drain at the toe 

of the section. 

Upstream face is proposed to be protected by 2.0 m thick riprap of well 

graded blasted rock material on the u/s slope of main dam. 

The earthen core section has been provided with two rows of curtain grouting 

in addition to any special treatment works for geological discontinuities 

encountered, if any. 

The maximum section has been checked for stability in accordance with the 

relevant Indian standards. The earth and rockfill dam will be provided with 

requisite instrumentation network. The details of Earth & rockfill dam section 

are indicated in Drg. No WAP/PFR/KALAI /1004(R1). 

6.8.3 Chute Spillway 

A chute spillway of width 96 m and 800 m length has been proposed on the 

right bank on Lohit river to pass the design flood of 9500 cumecs. At the 

intake of chute spillway 5 nos gates of size 16 m to 15 m which is inclusive of 

one gate for additional factor of safety on consideration of 10% gates 

inoperative as per codal requirement. Radial gates will be operated by means 

of hydraulic hoist, provision of stop log gates with gantry crane is also made. 

Energy dissipation is proposed through trajectry buckat as tail water depth fall 

short of post jump depth requirement during high discharges. Trajectory 

bucket with lip angle of 30 o would throw the jet of water through the air into the 

6-10


plunge pool. The details are shown a drawing No. 

WAP/PFR/KALAI/1005(R1). 

6.8.4 Tunnel spillway 

A tunnel spillway of size 9.0 m dia at EL 1000 m has been provided to pass a 

discharge of 2000 cumecs. This is provided to check the siltation and 

enhance the live storage of the project during operation. This tunnel will be 

connected through the lined diversion tunnel No.1 by a vertical shaft 

connection. Plugging of the diversion tunnel by concrete at U/s of the junction 

of tunnel spillway & diversion tunnel is proposed to pass the design discharge 

during operation. The details of tunnel spillway shaft & its connection to 

diversion tunnel are proposed to be finalized based on the results of model 

studies at the next stage of studies. The details of tunnel spillway are shown 

in drawing No. WAP/PFR/KALAI/1006(R1). 

6.8.5 Morning Glory Spillway 

Since Lohit river carries heavy discharges even during lean season. Frequent 

gate operation of chute spillway may not be possible some times and to pass 

the nominal discharge coming above FRL are proposed to be diverted 

through morning glory spillway (Ungatted). The release of morning glory 

spillway will be passed through a shaft of 7.0 m dia and then through a tunnel 

of 7.0 m dia discharging the additional water to chute spillway. To finalise the 

details of morning glory spillway model studies are proposed at the next stage 

of studies. The details of Morning glory spillway arrangements are shown in 

drawing No. WAP/PFR/KALAI/1006(R1). 

6-11

6.9 INTAKE 


6.9.1 One intake structures is proposed on the left bank of the river upstream of 

the Diversion structure with its invert at El 1010.0 m i.e. 8.0 m above the new 

zero elevation to avoid entry of rolling debris into the water conductor system 

during floods. Five Nos. intake tunnel of 10 m dia (Horse shoe) are proposed 

on the left bank to carry design discharge of 1497.03 cumecs. A trashrack is 

proposed at the entry so that debris /particles exceeding 75 mm do not enter 

the water conductor system. 

6.10 HEADRACE TUNNEL 

6.10.1 The design discharge of 1497.03 cumecs is carried through 5 nos, 10 m dia, 

horse shoe shaped headrace tunnels, 1.1 km long (average) to meet the 

Vertical pressure shaft of 8 m dia. The alignment of the tunnel has been 

optimally fixed to provide adequate rock cover below the nallah crossings. 

6.10.2 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 30% 

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

remaining reach Good/Fair rock conditions are met. A 500 mm thick PCC 

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

for contact grouting & consolidation grouting has also been made. Since the 

length water conductor system is less than five times the head, therefore, 

provision of surge shaft has not been considered. 

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

WAP/PFR/KALAI/1007(R1). 

6-12

6.11 PRESSURE SHAFT 


6.11.1 Five nos. vertical pressure shafts of size 8.0 m diameter are proposed 

downstream of HRT keeping in view the adequacy of horizontal and vertical 

rock cover as per codal requirement. Pressure shaft drops from El 1005.0 m 

to El 917.6 m in line with the center line of distributor. The horizontal portion 

of pressure shaft is bifurcated into 2 feeders each of 5.6 m dia to feed to 10 

units of 260 MW each. 

The pressure shaft liner is designed taking into account 20% rock participation 

and 40% as water hammer head. High tensile steel conforming to grade A- 

517 is proposed for liner so as to restrict the liner thickness to reasonable 

limits to obviate the need for stress relieving. Liner thickness varies from 28 

mm to 45 mm in the pressure shaft reach velocity through pressure shaft is 

approx. 6.1 m/sec. 

6.12 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 two separate caverns. The main machine 

cavern is 24.0 m wide, it houses 10 units of 260 MW each along with 25 m 

long service bay. The generator floor level is kept at EL 930.0. Centre line of 

units is at EL 917.6 m and invert level of draft tubes is kept at EL 905.6 m. 

EOT crane of 350/35 tonnes capacity shall be provided at crane beam level at 

EL 944.0 m and travel up to service bay end also. The ten main inlet valves, 

one for each unit, are also provided. The transformer cavern is 15 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 in the 

6-13


transformer cavern. The tail race tunnel of 5 nos, 10 m dia (horse shoe type) 

of length 1.76 km each shall have reverse slope to meet the river bed level to 

discharge water back into the river Lohit. The details of PH are shown in 

drawing Nos. WAP/PFR/KALAI/1008(R1) & 1009(R1). 

6.13 ELECTRO - MECHANICAL WORKS 

The proposed 2600 MW KALAI Hydro-Electric Project would have Under 

ground type powerhouse. The installed capacity would be provided by 10 

nos. Vertical Axis Francis turbine driven generating units of 260 MW each. It 

is proposed to provide Inlet Valve of butterfly type for each turbine, which 

would be accommodated in the powerhouse cavern. 

The generation voltage of 11 kV would be stepped up to 400 kV through 3 

sets of single phase 97 MVA, 11/ 400/ √3 kV ODWF type unit step up 

transformers for each unit located in Transformer cavern. The 11 kV isolated 

bus ducts would connect the 11 kV generator terminals with 11 kV bushings 

of step up transformers. The 400 kV terminal of the transformers would be 

connected with 400 kV Gas Insulated Switchgear (GIS) located on the floor 

above the transformers in transformer cavern. 

The layout of generating equipments, unit step up transformers, switchyard 

etc. is indicated in the drawings Nos. WAP/PFR/KALAI/1008(R1) & 1009(R1). 

The GIS would accommodate 14 bays, 10 for generator incomings, 2 for 

outgoing 400 kV transmission lines, 1 for bus coupler and 1 for step down 

transformer. The power generated would thus be evacuated through 2 nos. 

400 kV D/C transmission lines. The single line diagram given in drawings 

Nos. WAP/PFR/KALAI/1010(R1). 

6-14

6.14 BRIEF PARTICULARS OF EQUIPMENTS 

6.14.1 Turbine and Governor 


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

are indicated below : 

i) Upstream Levels 

• FRL EL 1160.0 m 

• MDDL EL 1054.0 m 

ii) Tailrace Levels 

iii) Heads 

• Maximum EL 928.0 m 

• Minimum EL 925.0 m 

• Maximum net head 229.13 m 

• Minimum net head 122.85 m 

• Rated head 193.21 m 

Francis type turbine is considered appropriate choice considering the capacity 

of the generating units and head available for power generation. The turbine 

would be suitably rated to provide 260 MW at generator terminals at rated 

head of 193.21 m. The speed of turbine has been determined as 166.7 rpm. 

The centerline of turbine runner has been set at EL 917.6 M, 7.4 metres 

below the minimum TWL which is at EL 925 m. The governor would be 

electro-hydraulic 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. 

6-15

6.14.2 Main Inlet Valve 


It is proposed to provide an Inlet Valve of the Butterfly type for each turbine as 

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

governor malfunctioning, 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. 

6.14.3 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 - 260 MW 

ii) Power factor - 0.9 lag 

iii) Speed - 166.7 rpm 

iv) Class of Insulation of 

stator and rotor winding - Class 'F' 

v) Generation Voltage - 11 kV 

The generators would be provided with static excitation equipment and 

voltage regulator. Necessary power for excitation would be provided by 

tapping the generator terminals. 

6-16

6.14.4 Unit Step-up Transformer 


Three single phase 97 MVA, 11/ 400/√3 kV 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. 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 

400 kV bushing would be connected with 400 kV Gas Insulated Switchgear 

located on the floor above the transformers in transformer cavern. 

6.14.5 EOT Crane 

The heaviest equipment which the power house 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 685 tonnes. 

It is proposed to provide 2 Nos. EOT cranes of 350/35 tonnes capacity each. 

6.14.6 Auxiliary Equipment And Systems For The Power House 

Following equipments for the auxiliary system 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 

6-17


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 220V 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 

6.14 400 KV SWITCHYARD 

It is proposed to provide 400 kV, Gas Insulated Switchgear having 16 bays in 

which 10 bays are for generator incomings, 2 bays for 400 kV transmission 

lines, 1 bay for step down transformer and 1 bay for bus coupler. The double 

bus bars arrangement has been proposed which would provide flexibility and 

reliability in the operation of the plant. 

6.15 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. 

6-18

7.1 GENERAL 

CHAPTER-VII 

POWER POTENTIAL STUDIES 


The power potential studies have been carried out for Kalai Hydel Scheme 

located in Arunachal Pradesh. The execution of this project would help in 

reducing the gap between supply and demand of power in other 

neighbouring areas also. 

7.2 TYPE OF DEVELOPMENT 

The project has been planned as storage based development. The 

features of the scheme would be as follows: 

- FRL EL 1160 m 

- MDDL EL 1054 m 

- Storage at FRL 1160.429 Mcum 

- Storage at MDDL 250.692 Mcum 

- Live Storage 909.737 Mcum 

The FRL has been fixed to provide maximum feasible storage and keeping 

in view the submergence. The level v/s capacity characteristics for this 

alternative are indicated in Annex. 7.1. 

7.2.1 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 considered as EL 925 m. The 

Maximum TWL at 928 m corresponds to discharge with all the units running 

7-1


at full load. The FRL of downstream project called as Hutong HEP has 

been fixed as 920 M. The releases of Kalai HEP would be utilized for 

Hutong HEP. The FRL of downstream project called as Hutong HEP has 

been fixed as 920 m. The releases of Kalai HEP would be utilised to 

Hutong HEP. 

7.3 WATER AVAILABILITY 

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

Chapter No. 5 on “hydrology”. Inflow series for 17 years from 1983-84 to 

1999-2000 has been utilized for power potential studies and are indicated 

in Annex-7.2. 

7.4 TYPE OF TURBINE 

Francis type turbine is considered the appropriate choice based on the 

rated head of 193.21 m and capacity of generating units. The following 

efficiencies pertaining to Francis turbine driven generating unit have been 

considered in power potential studies: 

- Efficiency of Turbine - 93.50% 

- Efficiency of Generator - 98.00% 

- Combined efficiency of 

turbine and generator 

- 91.63% 

7.5 90% AND 50% DEPENDABLE YEARS 

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

generation for all the 17 years has been computed with unlimited installed 

capacity. Annual energy generation is tabulated in descending order and 

7-2


indicated in Annex-7.3. The 90% and 50% dependable years have been 

determined on the following basis, where ‘N’ is the no. of years for which 

unrestricted energy generated have been calculated. 

90% year - (N+1) x 0.9 - 16 th year 

50% year - (N+1) x 0.5 - 9 th year 

Based on above, 1992-93 Year and 1993-94 Year work out to be 90% and 

50% dependable years respectively. 

7.6 INSTALLED CAPACITY AND ANNUAL ENERGY BENEFITS 

7.6.1 The power potential has been computed in 90% dependable year and 

results are indicated in Annex. 7.4. The head in this case has been varying 

with the level in the reservoir. Losses in water conductor system have been 

considered as 2.5% which works out to 5.875 m. The study indicates firm 

power as 509.44 MW continuous. Considering 4 hours peaking, the 

installed capacity required would be around 3000 MW. 

For optimization of installed capacity, annual energy generation (KWh), 

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

Incremental installed capacity have been computed for 90% dependable 

year ranging from 2400 MW to installed capacity of 2850 MW in steps of 

50 MW and these are indicated in Annex 7.5. 

The analysis of Incremental energy and incremental installed capacity 

indicate that the ratio d(KWh)/d(KW) drops very steeply for increase in 

installed capacity at 2600 MW (Annex 7.5) and thus justify installed 

capacity of 2600 MW. 

7-3


Keeping in view the system requirement and reservoir simulation studies 

the installation of 2600 MW is considered optimum. The load factor of 

operation would be 19.59 % corresponding to more than 4 hours of 

peaking. 

7.6.2 No. of Generating Units 

The size of generating units has been chosen as 260 MW considering 

transport limitations and economic considerations. Accordingly 10 units of 

260 MW each have been chosen. 

The turbine would be suitably rated to provide 260 MW at generator 

terminals. The speed of the generating unit has been determined as 166.7 

rpm. 

7.7 RESULTS OF STUDIES 

Annual energy generation in 90% and 50% dependable years have been 

computed for installed capacity of 2600 MW and are indicated in Annex. 

7.4 and Annex. 7.6 respectively. The studies have been carried out on 

annual basis and live storage of 909.739 Mcum has been utilized for 

augmenting the flows of lean period. 

Parameters 90% dependable 50% dependable 

year 

year 

Energy generation (GWh) 10608.64 14508.77 

Firm Power (MW) 509.44 1065.56 

Lean Period L.F 19.59% 40.98% 

Annual L.F 46.58% 63.70% 

7-4


Design energy has been computed as 10449.52 GWh and computations 

have been indicated in Annex. 7.7. Summary of Power Potential Studies 

for 17 years (1983-84 to 1999-2000) is given as Annex. 7.8. 

7.8 CONCLUSION 

Kalai H.E. Project is proposed to be a storage-based development. 

Installation of 2600 MW comprising of ten units of 260 MW each, would be 

necessary to derive optimum benefits. The project would afford annual 

energy generation of 10608.64 GWh in 90% dependable year. 

7.9 RECOMMENDATIONS FOR FURTHER STUDIES 

The following additional studies would need to be carried out at DPR stage: 

i) Based on data available of topographic survey, tailrace-rating curve 

should be evolved, so that in energy computation, the head utilized for 

power generation is corrected with the change in TWL. 

ii) The storage at FRL and MDDL should be computed with more 

accuracy based on the data of topographic survey. 

iii) The size of generating unit would need to be optimized considering the 

transportation limitation. 

iv) FRL would need to be optimized considering the submergence of 

inhabited/ agricultural/ forest areas. 

7-5

8.1 ABOUT THE PROJECT 

CHAPTER - VIII 

POWER EVACUATION 


The Kalai HE Project is proposed on river Lohit in the Arunachal Pradesh 

State. The dam site is located at latitude of 27.963 (D-M-S) North and 

Longitude of 96.96 (D-M-S) East. 

8.2 Power Scenario in Arunachal Pradesh 

The state electricity utility of Arunachal Pradesh is responsible for the coordinated 

development of generation, transmission and distribution of 

electricity in the state. As part of power reforms in line with the national 

policy, the government is taking several initiatives such as generation capacity 

addition, strengthening of T&D network, participation of private sector etc. in 

order to improve the overall situation in the state. 

The share of power sector outlay in the state has kept as 19.40% in the eighth 

plan, of total outlay towards power requirements. Out of total 3649 inhibited 

villages (1991 census), 2316 villages are electrified. The per capita energy 

consumption in Arunachal Pradesh is 68.61 kWh which is much lower than all 

India average of 354.75 kWh. 

8.3 STATE POWER SECTOR STATISTICS 

The projected Energy requirement & Peak load for Arunachal Pradesh at the 

end of 9 th and 11 th plan is indicated as below : 

8-1

Plan 2001-02 

End of 9 th 

Energy Requirement 

(MU) 

Plan 

2011-12 

End of 11 th Plan 


2001-02 

End of 9 th Plan 

Peak Load 

(MW) 

2011-12 

End of 11 th 

Plan 

346 982 94 249 

The installed capacity available ( as on 29.2.2004) to state is as: 

Share in Central Sector 117.00 MW 

State Sector 45.43 MW 

Private Sector 0.00 MW 

Total 162.43 MW 

The present condition of Peak Demand/Peak Met of Arunachal Pradesh 

is as: 

Period Peak 

Demand 

(MW) 

Peak Met 

(MW) 


(MW) (%) 

April-Feb. 2004 50 50 0 0 

Similarly, the actual power supply position of Arunachal Pradesh is as : 

Period Requirement 

(MU) 

Availability 

(MU) 


(-) MU 


(%) 

April-Feb. 2004 163 161 -2 -1.2 

The transmission network of Arunachal Pradesh is given at Annexure 8.1. 

8-2


8.4 ARRANGEMENT FOR EVACUATION OF POWER FROM KALAI HEP 

The 2600 MW power generated at 11 kV at Kalai HEP will be stepped upto 

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

proposed Roing/Dambuk pooling point. Proposed line from Kalai HEP for 

evacuation of power is shown at Annexure-8.2. 

8.5 ROUTE LENGTH AND COSTING OF 400 KV TRANSMISSION LINE FOR 

EVACUATION OF POWER FROM KALAI HEP. 

The power of this project is intended to be evacuated by proposed 400 kV two 

quad lines using moose conductor size to proposed Roing/Dambuk pooling 

point with estimated distance of 110 km (2x400 kV D/C with quad moose 

conductor) from Kalai HEP to proposed Roing/Dambuk pooling point. The 

cost of 2x110 = 220 km D/C lines is estimated as Rs. 412.5 Crores. 

8-3

CHAPTER - IX 


INITIAL ENVIRONMENTAL EXAMINATION STUDIES 


The Initial Environmental Examination of the proposed Kalai hydroelectric 

project, has following objectives which are proposed to be covered during 

various phases of 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 undergo significant changes 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 EIA 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 

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

part of next level of environmental study. 

9-1

9.2 ENVIRONMENTAL BASELINE SETTING 


The study area 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-ecological aspects. 

9.2.1 Physio-Chemical Aspects 

a) Water Quality 

The proposed hydroelectric project is located on Lohit river. The population 

density in the project area as well as the catchment area intercepted at the 

diversion structure site is low. Mainly traditional form of agriculture 

characterized by low agro-chemical dosing and absence of mechanization 

ensures that the pollution loading in agricultural runoff is also quite low. There 

are no water polluting industries in the area. Thus, it can be concluded that 

apart from sewage generated from settlements, there are no major sources of 

pollution in the project area. Even during lean season, sufficient water is 

available for dilution of pollutants. In such streams, water quality is 

characterized by high DO and low BOD levels. Various cations and anions 

too are well within the permissible limits, specified for meeting drinking water 

requirements. 

The major sources of water in the area are various streams and nallahs 

flowing adjacent to various settlements. The water is conveyed to the point of 

consumption under gravity. The sewage so generated too is disposed without 

any treatment in natural streams and channels. Due to availability of sufficient 

9-2


water for dilution, and lack of pollution loading, no adverse impact on water 

quality is observed. 

b) Landuse 

The submergence area is 1296.7 ha, which comprises of dense mixed forest, 

open forest, scrub land and agricultural land. Additional land will be required 

for siting of various project appurtenances as well. It is recommended that 

detailed studies be conducted to ascertain the ownership status of land to be 

acquired for various project appurtenances. Based on the type of land to be 

acquired, appropriate compensatory measures can be recommended. 

9.2.2 Ecological Aspects 

a) Vegetation 

Vegetation in the Project as well as study area is categorized as sub-tropical 

Pine forest. Pine is the dominant tree species. The two varieties of Pine 

reported in the area are Pinus roxburghii and Pinus wallichiana. The other 

associates include Alnus nepalensis, Rhus japanica, Altingia excelsa 

Pterospermum acerifolium, Castanopsis indica, Chisocheton paniculata. 

Ferns and orchids are also present. The biodiversity is generally poor and the 

forest becomes mixed on warmer, southern aspects. 

Within the project and study area, settlements at few locations are also 

observed. The forest in and around such area has remnant vegetation with 

dense undergrowth, comprising of trees of standard growth belonging to 

Quercus sp. Rhododendrons, sp. Betula utilis, etc. 

The major floral species observed in the study area is given in Table-9.1. 

9-3

Table-9.1 

Major floral species observed in the study area 

Common Name Scientific Name 

Trees 

Pine Pinus roxburghii 

Pine Pinus wallichiana 

Utis Alnus nepalensis 

Rhus javanica 

Jutuli Altingia excelsa 

Hathi paila Pterospermum acerifolium 

Hingori Castanopsis indica 

Banderdima Chisocheton paniculata 

Undergrowth 

Jati Bambusa tulda 

Bamboo Dendrocalamus sp. 

Jhang Calamus erectus 

Bijuli Bambusa pallida 

b) Fauna 


Patches of dense mixed forests are observed in and around the project area 

including study area. The population density is low. However, Forest area 

close to settlements within the study area have been cleared, for Jhum 

Cultivation or permanent cultivation. In undisturbed forests, faunal population 

is reported. However, in degraded forest, faunal population is virtually absent. 

Based on the review of secondary data and interaction with the Forest 

Department, major faunal species reported in the forests of the project and 

study area include leopard cat, Monkey, Jungle cat, mole rat, fox etc. 

Amongst the avi-fauna, the commonly observed species included Indian Koel, 

Red turtle dove, jungle crow Labwing etc. Likewise, krait, Cobra, King cobra, 

Viper, etc. are the major snake species observed in the study area. 

The list of faunal species observed in the study area is outlined in Table-9.2. 

9-4

TABLE-9.2 

List of faunal species observed in the study area 

Common Name Zoological Name 

Mammals 

Leopard cat Felis bengalensis 

Monkey Muntiacus muntjack 

Jungle cat 

Wolf Canis lupus 

Molerat Bandicota bengalensis 

Indian fox Vulpes bengalensis 

Cervus unicolor 

Reptiles 

Common krait Bungarus caerules 

King cobra Naja hannah 

Russel’s viper Vipera russelli 

Common garden lizard Calotes versicular 

Avi -fauna 

Jungle crow Corvus macrohynchos 

Red turtle dove Streptopelia tranqueberica 

Myna Sturnus malabaricus 

Lapwing Vanellus vanellus 

Kind Fisher Ceryle lugubusis 

c) Fisheries 


The proposed project lies on Lohit river. Based on the climatic and 

topographical settings, it is quite likely that Snow trout, and Mahaseer which 

are migratory fish species could be present in the river. 

As a part of the EIA study, it is recommended that a detailed fisheries survey 

be conducted in Lohit river and its tributaries coming under submergence to 

ascertain the presence of various species and distribution in various seasons 

of the year. 

9-5

9.2.3 Socio-economic Aspects 


The ST population is the dominant caste group, followed by General Castes. 

The SC population is virtually negligible in the project area. The literacy rate in 

the study area is quite high, i.e. of the order of 60%. The male and female 

literacy rates are more or less equal, which is a typical feature of many areas 

in the north-eastern part of the country. 

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 

Sufficient quantity of coarse and fine aggregate is required for construction of 

a hydroelectric project. The fine aggregates are generally available as river 

shoal deposits. During excavation of clay material, particles are likely to get 

entrained, which can increase the turbidity of the water body. This may 

9-6


marginally affect the primary productivity of the river. However, this scenario is 

likely to last only during the time for which material is being excavated. The 

water quality is likely to return to its original turbidity levels, few days after the 

cessation of excavation operations. The depressions so created after 

excavation of the construction material is likely to be filled up by the 

sediments/silts brought down by the river from which the material is being 

excavated. Thus, no specific management measures are required for 

extraction of clay material from shoal deposits. 

The coarse aggregates need to be extracted from various quarry sites in and 

around the project area. Efforts need to be made to ensure that existing 

quarries, if any, in the area be utilized to the extent possible. Normally 

quarrying is done along the hill face, using semi-mechanized methods. With 

passage of time, rock from the exposed face of the quarry under the action of 

wind and other erosional forces, get slowly weathered and after some time, 

they may become potential source of landslide. Thus, it is necessary to 

implement appropriate slope stabilization measures to prevent the possibility 

of soil erosion and landslides in the quarry sites. If new quarries have to be 

opened, then they can be located over non-forest land so as to minimize 

adverse impacts on flora and fauna. 

Operation of construction equipment 

During construction phase, various types of equipment will be brought to the 

site. These include crushers, batching plant, drillers, earthmovers, rock 

bolters, etc. The siting of construction equipment would require significant 

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

construction materials as well. In addition, land will also be temporarily 

acquired, i.e. for the duration of project construction for storing the quarried 

material before crushing, crushed material, cement, rubble, etc. The storage 

9-7


site needs to be so selected that it is far away from human habitations and 

faunal population. Such sites can be selected in consultation with the Forest 

Department, so that they are not located along the migratory routes of faunal 

species. 

Soil erosion 

The runoff from the construction sites will have a natural tendency to flow 

towards Lohit river or its tributaries. For some distance downstream of major 

construction sites, such as dam, power house, etc. there is a possibility of 

increased sediment levels which will lead to reduction in light penetration, 

which in turn could reduce the photosynthetic activity to some extent of the 

aquatic plants as it depends directly on sunlight. This change is likely to have 

an adverse impact on the primary biological productivity of the affected stretch 

of the water body. Based on experience in other projects, significant impacts 

on this account are not expected to be significant for the main river. However, 

for small tributaries, which are seasonal in nature, such impacts could be 

significant. 

Problems of muck disposal 

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

operations, construction of roads, etc. Normally, muck disposal sites are 

cleared of vegetation before disposing the material. Trees are cut before 

muck disposal, however, shrubs, grass or other types of undergrowth on 

which muck is disposed perishes. 

In many projects, it has been observed that the muck generated by various 

sources is disposed along the river valleys. The boulders are stacked along 

the river bank, and during the next monsoons, the boulders can flow along 

9-8


with the runoff, and ultimately find their way into the river and finally into the 

plains. Hence, in the proposed project adequate measures, such as retaining 

walls, etc. need to be implemented to ameliorate the likely adverse impacts. 

These aspects need to be covered as a part of the EIA study. 

Construction of roads 

The project construction would entail significant vehicular movement for 

transportation of large construction material and heavy construction 

equipment. Most of the roads in the project area would require widening. 

Many new roads would have to be constructed. 

The construction of roads can lead to the following impacts: 

• Removal of trees on slopes and re-working of the slopes in the 

immediate vicinity of roads can encourage landslides, erosion gullies, 

etc. With the removal of vegetal cover, erosive action of water gets 

pronounced and accelerates the process of soil erosion and formation 

of deep gullies. Consequently, the hill faces are bared of soil and 

vegetal cover and enormous quantities of soil and rock can move down 

the rivers, and in some cases, the road itself may get washed out. 

• Construction of new roads increases the accessibility of a hitherto 

undisturbed area resulting in greater human interference and 

subsequent adverse impacts on the ecosystem. 

Measures for mitigating the above mentioned adverse impacts needs to be 

covered as part of the EIA study. 

9-9

) Operation phase 


The area coming under reservoir submergence is about 1296.7 ha. A large 

portion of the submergence area is forest land belonging to dense mixed 

forest (mainly pine), open forest and scrub lands. Additional area will be 

required for siting of project appurtenances, infrastructure, etc. The ownership 

category of such land needs to be ascertained, once project layout is finalized 

as a part of DPR preparation. Based on the type of land being acquired 

appropriate management measures shall be formulated. 

The major land use category in the project area and its surrounding is forest 

area. Efforts should be made to the extent possible that minimal forest land is 

acquired. Project appurtenances such as colonies, labour camps, and other 

appurtenances, which are not site-specific, can be located over government 

land to ensure that there is minimum acquisition of forest and private land. For 

project related infrastructure, e.g. labour camps, project colonies, office, etc. 

forest land should be avoided. 

9.3.2 Impacts on Water Resources 

The construction of dam 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 dam site up to the confluence point of tail race 

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

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

impact. However, reduction in flow from the dam site up to the confluence of 

these rivers is likely to have a minor impact on riverine ecology as the 

discharge during lean flow is significantly less. As a part of EIA study, 

requirement for release of minimum flow for sustenance of riverine fisheries 

needs to be assessed. 

9-10

9.3.3 Impacts on Water Quality 

a) Construction phase 

Effluent from labour camps 


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 

through open drains, where ultimately it will find its way into Lohit river. The 

disposal of untreated sewage could have adverse impacts on river water 

quality, especially during lean season flow. Thus, it is recommended to 

commission adequate sewage treatment facilities in the labour camps. 

It is a common practice during construction phase to commission low cost 

sanitation treatment units, as such units are required only during the project 

construction phase. Similar measures are recommended for the proposed 

project as well. 

Effluent from crushers 

During construction phase, at least one crusher each will be commissioned at 

the dam and power house sites. Water is required to wash the boulders and 

to lower the temperature of the crushing edge. About 0.1 m 3 of water is 

required per tonne of material crushed. The effluent from the crusher would 

9-11


contain high suspended solids. The effluent, if disposed without treatment can 

lead to marginal increase in the turbidity levels in the receiving water bodies. 

However, no major adverse impacts are anticipated due to small quantity of 

effluent and availability of sufficient water for dilution. The severity of impacts 

would vary from season to season with variations in water availability of 

dilution. It is recommended to provide a settling tank to treat the effluent from 

crushers before disposal. 

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 aerated lagoon 

and secondary settling tank need to be commissioned for this purpose to 

ameliorate the marginal impacts. 

Impacts on reservoir water quality 

The flooding of forest and agricultural 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. Since, in the 

proposed project, significant area under forests and agriculture is likely to be 

submerged, it is recommended that a detailed water quality modeling study be 

conducted as a part of EIA study to assess the impacts on reservoir D.O. 

levels. 

9-12

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. As 

a part of the proposed project, command area development is not envisaged. 

Eutrophication problems, 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. The project area 

and its surroundings has dense forests. Such areas may be adversely 

affected, if alternate fuel sources are not provided to workers involved in 

project construction. It is recommended that the contractor involved in 

construction activities to provide alternate source of fuel to the labour 

population and their families involved in construction activities. Alternatively, 

9-13


community kitchens using Kerosene or LPG as fuel can be run for the benefit 

of labour population and their families. 

b) Operation Phase 

Acquisition of forest land 

The reservoir submergence is 1296.7 ha entailing submergence of dense 

mixed forest open forest and scrub land. The acquisition of forest land is to be 

compensated by compensatory afforestation as per the measures outlined in 

Forest (Conservation) Act, 1980, which stipulates: 

- if non-forest land is not available, compensatory plantations are to be 

established on degraded forest lands, which must be twice the forest 

area affected or lost, and 

- if non-forest land is available, compensatory forest are to be raised 

over an area equivalent to the forest area affected or lost. 

Additional land will also be required for siting of construction equipment, 

storage of construction material, muck disposal, widening of existing roads, 

construction of new project roads, infrastructure development, etc. The 

information on ownership status of land to be acquired for other project 

appurtenances needs to be collected as a part of EIA study. For acquisition of 

forest land irrespective of their vegetal cover, compensatory afforestation to 

be done as per the guidelines of Forest (Conservation) Act, 1980. It is also 

recommended that project appurtenances, which are not site-specific, should 

be located over non-forest land. 

It is recommended that as a part of the EIA study, a detailed ecological survey 

be conducted to ascertain the ecological characteristics, floristic composition 

9-14


of the area. The presence of rare/endangered species, if any needs to be 

ascertained, and if their presence is confirmed, then appropriate conservation 

measures need to be implemented. 

9.3.5 Impacts on Terrestrial Fauna 


As mentioned earlier, faunal population could be present in the project area, 

which could be adversely affected as a result of acquisition of forest land 

under reservoir submergence and acquisition of land for other project 

appurtenances. Specific measures in the form of increased surveillance need 

to be recommended to ensure that there are no significant impacts on fauna 

in the forests of the study area. In addition to above, specific wildlife 

conservation measures need to be recommended as a part of the EIA study. 


Impacts due to increased accessibility 

During project operation phase, accessibility to the area will improve due to 

construction of roads, which in turn may increase human interference leading 

to marginal adverse impacts on the terrestrial ecosystem. Since significant 

increase in human population is not anticipated during project operation 

phase, adverse impacts due to such interferences is likely to be very 

marginal. 

9-15

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. 


Data on fish species observed in Lohit river is not available. However, based 

on studies conducted on other rivers in the region traversing in similar 

settings, some of the migratory species e.g. Snow trout, i.e. Schizothorax 

richardsonii, and Mahaseer (Tor sp.). could be present in Lohit river. It is 

recommended that a detailed fisheries survey be conducted as a part of EIA 

study in the project area to ascertain the presence and distribution of various 

migratory fish species, and also to assess the impacts due to disruption of 

hydrologic regime in the river stretch downstream of diversion structure site to 

rail race disposal site. 

9-16

9.3.7 Impacts on Noise Environment 


Increased noise levels are anticipated only during construction phase due to 

operation of various equipment, increased vehicular traffic and blasting etc. 

Increased noise level, especially blasting could scare away wildlife from the 

area. Since, settlements with human population and dense forests with 

wildlife population are reported in the area, hence, there could be adverse 

impact on this account. Thus, it is recommended that as a part of EIA study, a 

detailed noise modeling study be conducted to quantify such impacts. 

9.3.8 Air Pollution 

Pollution due to fuel combustion in various equipment 

The operation of various construction equipment requires combustion of fuel. 

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 

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 dam and the power house sites. During 

crushing operations, fugitive emissions comprising of the suspended 

9-17


particulate will be generated, which could lead to some adverse impacts on 

settlements close to the site. 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. 

Job opportunities will improve significantly in this area. At present most of the 

population sustains by cultivation and allied activities. The project will open a 

large number of jobs to the local population. 

As a part of the EIA study, it is recommended to conduct a detailed 

Ethnographic study to assess the impacts of immigrating labour population on 

the local population and their cultural practices. 

b) Project operation phase 

Acquisition of private land 

Private land or homesteads are likely to be acquired under reservoir 

submergence. The list of project affected villages is given in Table-9.3. 

Additional land will be acquired for other project appurtenances need to be 

9-18


acquired which could entail acquisition of private land. A socio-economic 

survey is recommended to be conducted as a part of the EIA study for the 

private land to be acquired for various project appurtenances. Based on the 

findings of the survey, a detailed R&R plan, can be formulated for Project 

Affected Families. 

TABLE-9.3 

List of Project affected villages due to 

reservoir submergence 

Left Bank Right Bank 

Village Kalen Village Hala 

Village Chik Village Vavlong 

Village Wati Village Salti 

Village Situ Village Shetaticamp 

Industrialization and urbanization 

The commissioning of a hydro-electric project provides significant impetus to 

economic development in the area being supplied with power. Likewise, in the 

project area, commissioning of a hydro-electric project would lead to 

mushrooming of various allied activities, providing employment to locals in the 

area. 

9.4 SUMMARY OF IMPACTS AND EMP 

A summary of impacts and recommended management measures are 

summarized in Table-9.4. 

9-19


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 

construction material 

from various quarry 

sites. 

quarry site 

• Temporary acquisition • No specific 

of land for siting of management 

construction equipment 

& material, waste 

material 

measures are required. 

• Generation of muck due • Disposal at designated 

to tunnelling operations sites and provision of 

and construction of suitable management 

roads. 

measures including 

bio-engineering 

treatment measures 

Operation 

phase 

• Acquisition of forest 

and private land 

• Compensatory 

measures to be 

implemented based on 

type of land to be 

acquired 

2. Water resources 

Operation 

phase 

3. Water quality 

Construction 

phase 

Operation 

phase 

• River stretch from 

diversion structure site 

to tail race outfall will 

have reduced flow 

during lean season. 

• Water pollution due to 

disposal of sewage 

from labour colonies. 

• Deterioration of water 

quality in the dry stretch 

of river due to reduced 

flow during the lean 

season. 

• In case downstream 

nallahs do not 

contribute lean flows, 

minimum flow will be 

released to maintain 

the riverine ecology. 

• Provision of community 

toilets and septic tanks 

• No significant impact is 

anticipated 

9-20

S. 

No. 



4. Terrestrial flora 

Construction 

phase 

Operation 

phase 

5. Terrestrial fauna 

Construction 

phase 

Operation 

phase 

6. Aquatic Ecology 

Construction 

phase 

• Disposal of sewage 

from project colony. 

• Eutrophication 

problems. 

• Cutting of trees for 

meeting fuel wood 

requirements by labour. 

• Acquisition of forest 

land 

• Significant impact on 

wildlife due to operation 

of various construction 

equipment is not 

anticipated. 

• Disturbance to wildlife 

due to increased 

accessibility in the 

area. 

• Marginal decrease in 

aquatic productivity due 

to increased turbidity 

and lesser light 

penetration. 

• Provision of 

adequate sewage 

treatment facilities 

including aerated 

lagoon and 

secondary settling 

tank. 

• Management 

measures are not 

required, as no 

impacts are 

anticipated on this 

account. 

• Provision of community 

kitchen by the 

contractors engaged in 

project construction. 

• Compensatory 

afforestation as per 

the Indian Forest 

Conservation Act 

(1980). Conservation 

Plan to be formulated, 

if required. 

• Noise control 

measures to be 

implemented. 

• Specific management 

measures e.g. 

increased surveillance 

to be implemented. 

• Marginal impact, hence 

no specific 

management 

measures are 

suggested. 

9-21

S. 

No. 



Operation 

phase 

7. Noise Environment 

Construction 

phase 

8. Air Environment 

Construction 

phase 

• Reduction in river flow 

in stretch downstream 

of dam site up to tail 

race outfall 

• Increase in noise levels 

due to operation of 

various construction 

equipment. 

• 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. 

• Loss of private land and 

homestead. 

• Increased power 

generation 

• Greater employment 

opportunities 

• Provision of release of 

minimum flow in case 

downstream nallahs 

do not contribute to 

lean flows, and 

adverse impacts on 

water quality and 

aquatic ecology are 

anticipated. 

• Marginal impact, hence 

no management 

measures are 

suggested. 

• Cyclones will be 

provided in crushers 

installed at various 

construction sites. 

• Formulation of 

Resettlement and 

Rehabilitation Plan 

- 

- 

- 

9-22

9.5 SATELLITE IMAGERY 


Satellite imagery of the project area & submergence area are placed in Fig- 

9.1 and 9.2 respectively. 

9.6 CONCLUSIONS AND RECOMMENDATIONS 

The following aspects need to be studied in detail as a part of next phase of 

environmental studies: 

- Impacts due to acquisition of dense forest land. 

- Impediment to migratory fish species as a result of construction of dam. 

- Impacts on ethnographic aspects 

- Proper stabilization of quarry and muck disposal sites 

- Management of pollution sources from labour camps. 

- Formulation of Resettlement and Rehabilitation Plan for Project 

Affected Families. 

9-23


CHAPTER – X 

INFRASTRUCTURE FACILITIES 


The Kalai HE Project envisages construction of a storage dam near village 

Karooti for diversion of water of Lohit River, a major left bank tributary of 

Brahmaputra river with a view of utilize flows over large head available on the 

same river downstream for hydro power development. The project involve 

construction of a 241.0 m high earth & rockfill dam, with chute spillway located 

on the right bank and an underground power house on the left bank of the 

river. The water shall be carried by 5 head race tunnels each 1.10 km long 

and 10.0 m diameter (horse shore shaped) to the underground power house 

located on the left bank. After which water will be carried through 5 nos tail 

race tunnels each 1.76 km long 10.0 m dia (horse shoe shaped) back to the 

river after generation of 2600 MW power (10 x 260 MW). 

The Lohit river originate on elevation about EL 6190.0 m above MSL from the 

snow lad peaks in Eastern Tibet and enters India through Kibithoo area. The 

Lohit river has total length of 413 km from the source in Tibet to its confluence 

point with Dihang near Kobo with 170 km length in Tibet and 243 km length in 

India. 

The major infrastructure facilities needed for the project are described in the 

following paragraph. 

10.2 COMMUNICATIONS 

There is no rail head in Arunachal Pradesh. The nearest rail head for the 

project is at Tinsukhia (Assam) which is a broad gauge line and connected to 

10-1


Tezu by road the district head quarter of Lohit by National Highway No. 37. 

The distance between Tezu and Tinsukhia via the RCC bridge (on 

completion) at Brahmakund will be about 200 km. The Kalai H.E. Project site 

is located near village Kumblung at a distance of 101 km length of unmetalled 

motorable road from Tezu via Brahmakund and Chingwinti. The distance from 

Chingwinti to the dam site is about 9.0 km. 

There is an airport for small aircraft which is located at Tezu from where state 

owned crafts and Pawan Hans fly to the nearest Town Dibrugarh, Itanagar 

Trekking route and unmetalled roads shall require extensive improvement, 

widening and hill slopes stabilization measures including widening and 

improvement of bridges on river Lohit and 9 bridges on the right bank 

tributaries joining the Lohit river. In addition 11 new bridges require to be 

constructed on the tributary of Lohit river joining from the right bank for 

transportation of heavy construction equipment and machinery. 

10.3 ROADS IN THE PROJECT AREA 

National Highway no. 37 runs along the left bank of Brahmaputra river joining 

Tinsukhia (Assam) with Brahmakund. This road is being maintained by BRTF 

and would need improvement for transportation of heavy machinery and 

equipment required for the project. Besides 115 km of roads would be 

required to be constructed for approaching the dam, power house, rock 

quarries. various adits to tunnels, power house, colonies and internal roads 

etc. 

10.4 RAILWAYS 

There is no rail head in Arunachal Pradesh. The nearest rail head is at 

Tinsukhia (Assam) which is a broad gauge line and is about 200 km from 

Tezu, the district head quarter of Lohit. Railway siding for unloading 

10-2


machinery & equipment and generating plant of the project is to be provided 

at Tinsukhia. 

10.5 CONSTUCTION POWER 

The requirement of Power for various activities of the project is estimated to 

about 12.0 MW and is required for (i) infrastructural works such as project 

colony, street lighting, roads etc, and (ii) For construction activity of major 

works such as tunnels, Adits, Dam area, and power house complex. As there 

is no grid power available in the region the total requirement of power has to 

be met by Diesel Generating sets. In the initial period of about 2 years the 

requirement would be about 5.0 MW and this subsequently has to be 

increased to 12.0 MW when the construction activity picks up. 

10.6 TELECOMMUNICATION 

To ensure efficient execution at various sites, adequate and reliable 

telecommunication net work is necessary. An electronic private Automatic 

Exchange with a capacity of about 50 lines is proposed. There is a telephone 

exchange of BSNL at Tezu, the district headquarter of Lohit district. 

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. 

10.7 PROJECT COLONIES/BUILDINGS 

10.7.1 The main project colony for the dam is proposed near Kumblung about 1.0 

km from the dam site and power house complex. Facilities such as school, 

post office, police station, market, primary health centre will have to be 

10-3


established at Kumblung besides fire fighting arrangement, canteen, 

recreation facility and administrative building. About 50 family quarters and a 

hostel are proposed to be built at Kumblung for the dam and for the power 

house. 

10.7.2 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. 

10.8 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, penstocks etc. will have to be identified near the 

work sites. 

10.9 EXPLOSIVE MAGAZING 

Two explosive magazines one for the works at dam site and rock quarries and 

another for the underground works are to be built. 

10-4

10.10 FUEL STATION 


One number fueling station for providing POL to the project vehicle / 

equipment is proposed to be located at village Kumblung. 

10.11 WATER SUPPLY AND SANITATION 

For drinking purposes in the colony areas, suitable water treatment plants for 

treating water drawn from the river Lohit 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. 

10-5


CHAPTER – XI 

CONSTRUCTION PLANNING & SCHEDULE 


The Kalai H.E. Project is located at an altitude of about 924.0 m above mean 

sea level near village Kumblung across the Lohit river, a left bank tributary of 

Brahmaputra river in Lohit district of Arunachal Pradesh. The climate is highly 

humid in lower elevations and in the valleys and intensely cold in the higher 

elevations. The winter prevails during the months from late Nov. to early 

March. Period from March to May is the pre monsoon season. It is followed by 

monsoon from June to October. The climate of the Lohit basin is 

characterized by torrential rains caused mainly by monsoon from June to 

October and 52% of the total annual rainfall occurs during the monsoon 

period. However, for construction purposes the working season could be 

considered from November to May months. 

The area has rugged hills with steep gorges and deep valleys through which 

the river Lohit flows and has steep gradients. The river swells into torrents, 

during the rainy season. The river has floods during June to October with 

peaks mostly occurring in July to September. A period of 30 months has been 

provided for preparation of Detailed Project Report and necessary statutory 

clearances and approvals. Thereafter 30 months’ have been provided for preconstruction 

activities of field investigations, sub-surface explorations and 

creating infrastructure facilities, construction power, land acquisition, 

engineering design, drawings, and tender engineering etc. The construction 

phase includes all the pre construction activities. A construction period of 7 

years has been considered for completion of the project. Considering the 

topography, location of the project and remoteness of the area. This could be 

11-1


further optimised in the event other projects are also taken up simultaneously 

in the same river basin in Arunachal Pradesh. 

11.2 PROJECT IN BRIEF 

The Kalai H.E. Project envisages construction of 241 m high earth and rockfill 

dam with chute spillway across the Lohit river, about 101.0 km from Tezu the 

district headquarter of Lohit. The scheme with a gross storage of 1160.43 

Mcum at FRL and live storage of 909.739 Mcum is proposed to be created 

by construction of a 241.0 m Earth & Rockfill dam and gated chute spillway 

on the right bank. The dam comprises of 450.0 m long earth & rockfill dam 

and 800 m long chute spillway on the right bank of the river Lohit. The chute 

spillway is designed for Maximum Flood value of 9500.0 cumecs. A design 

discharge of 1497.03 cumecs is proposed to be diverted through 5 nos. Head 

Race tunnels each 1.0 km long and 10.0 m dia (horse shoe shaped) to the 

vertical pressure shaft bifurcating to feed two units each in underground 

power house proposed on the left bank of the dam. An underground tail race 

tunnels of 10 m diameter, Horse shoe shaped each and each of 1.76 km 

length, discharge the water back to the river. 

11.3 CONSTRUCTION MATERIAL SOURCES 

The topography reveals that the river valleys being narrow there are very few 

rivers shoales present in the area. Therefore, the required construction 

material for the various components of the project viz. concrete Earth & 

Rockfill dam, and chute spillway section, power house etc. have to be met 

through rock quarries in the vicinity of the area. The requirement of core 

material, filter material, sand and aggregate materials will have to brought to 

site from the nearby areas and from approved quarry sites nearby and can be 

met by crushing the rocks from the nearby rocks quarry sites. 

11-2

11.4 CONTRACT PACKAGES 

The contracts packages shall mainly consist of the following: 


a) Earth & rockfill dam, Coffer dams, flood protection works, river training 

work, Chute spillway, river diversion tunnels etc. 

b) Intake structure, and HRT work including adits 

c) Pressure shaft, Power house, and tail race tunnel 

d) Hydro mechanical works 

e) Hydro Electrical & electro Mech Works 

The eligibility of the contractors shall have to be suitably fixed based on 

working experience under similar conditions. The auxiliary works of river 

diversion, coffer dams, penstock fabrication and switchyard shall be part of 

the civil works package. However, the work of providing basic site facilities 

like storage sites for material, approach roads, minimal construction 

equipment, testing laboratory, staff colony, water supply, field offices at power 

house etc. 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. 

11.5 SCHEDULE OF WORK 

The project area is located in a remote area and experiences heavy rainfall 

during monsoon. As such the working period has been limited to 240 days in 

a year with 25 working days in a month and 8 working hours per shift in a day. 

Two shift working is proposed in the working season for expeditious 

11-3


completion of the project, third shift could also be planned based on progress 

of work and constraints due to remoteness of the site. 

11.6 CONSTRUCTION ACTIVITIES 

After the financial arrangements for construction of the project are decided, 

Notice Inviting Tender for fixing the civil contractor can be invited within 6 

months on ICB basis. 

a) Diversion of river 

As the river section at the storage dam site is narrow, five diversion tunnels 

on the right bank are proposed before construction of the dam. U/s and d/s 

coffer dams would be constructed immediately after construction of diversion 

tunnels to divert the river. Thereafter river bed excavation is proposed to be 

taken up after completion of the coffer dams. The diversion tunnel invert level 

is kept at minimum flow level and will be completed during the non-monsoon 

period before the river water starts rising due to onset of monsoons. Work on 

the stripping of dam abutment and excavation of foundation, consolidation 

grouting and curtain grouting for the dam foundation in the river bed level 

completed upto the planned level before the start of next flood season. 

b) The concreting of the chute spillway and appurtenant works including 

hydro mechanical works are proposed to be completed latest by the end of 6 th 

year of the construction programme. 

11-4

c) Intake Structure and Head Race Tunnel 


The Intake structure excavation including the HRT portal will be taken-up first. 

Thereafter excavation of HRT will be carried out. The tunneling of 10.0 m 

diameter horse shoe shaped each of 1.0 km length will be excavated from 

both faces on HRT’s. Tunnels excavation shall be based on conventional 

drilling & blasting supported by ribs where essential, and supporting the 

excavated rock face by shot creting. Before undertaking the construction of 

the pressure shafts the approach and adits to Power House cavern will be 

completed. Construction of HRT, pressure shafts and errection of penstocks 

is proposed to be completed in the 60 th months. 

d) Power House 

The underground power house cavern accommodates 10 units of 260 MW 

each (2600 MW). The excavation of the power house cavern, transformer 

cavern and draft tube cavern etc. is proposed to be undertaken by the 

conventional methods, shall be accomplished through main access tunnel / 

TRT by deploying equipments and mucking devices after machine erection 

and installation is achieved. Testing of Machines and project commissioning 

would be taken up and planned to be achieved in the 72 nd month from the 

starting of the construction of the project. Approach to the power house shall 

be from the road on the left bank. 

e) Tail Race Tunnel 

The excavation of 10 diameter and 1.76 m long Horse-shaped tail race 

tunnels will be carried out from the outlet end of Tail Race Tunnel starting for 

the 18 th months and completion achieved in a period of 30 months. 

11-5


A period of 60 months has been kept for power house cavern transformer 

cavern and draft tube cavern etc. excavation and concreting. The construction 

schedule at PFR stage studies is given in the enclosed Plate 11-1. 

f) Testing Commissioning 

The testing commissioning of the power house will short phase wise after 60 th 

month from the start of work and units will be commissioned in three steps i.e. 

2 units, 3 units and 5 units respectively. 

11-6


CHAPTER – XII 

COST ESTIMATES 


Kalai Hydro Electric Project is located in Arunachal Pradesh State. The type 

of the scheme has been conceived as storage type having 241.0 m high rock 

fill dam with chute spillway and underground power house. The FRL of the 

project is kept at EL 1160.0 m. The diversion flood during construction is 

proposed to carry out 3 no. diversion tunnels having 9.0 m φ. It is proposed to 

have 10 nos. of units each having an installed capacity of 260 MW totaling to 

2600MW installed capacity, at rated discharge of 1497.03 cumecs. The 

scheme would provide energy benefits of 10608.64 GWh per annum. 

12.2 The Project is estimated to cost Rs. 5029.11 crores at June, 2003 price level 

the break down of cost is given below : 

Item Estimated Cost 

( Rs. crores ) 

Civil Works 

Electrical Works 

Sub Total (Generation) 

3159.92 

1869.19 

5029.11 

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 

enclosed as Annexure 12.1. The cost of various Electro-Mechanical works 

are placed at Annexure 12.2. The above cost does not include the cost of 

transmission. 

12-1


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 C- Works 

No. 

& J - Power Plant Civil Works 

1 A. Preliminary 2% 

2 K. Buildings 4% 

3 O. Miscellaneous 4% 

4 P. Maintenance 1% of C – Works, J - Power Plant 

- Civil Works, K - Building & R - 

Communication 

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

SCHEME NAME -KALAI 

COST ESTIMATE OF ELECTRO-MECHANICAL WORKS FOR PRE - FEASIBILTY REPORT 

Sl.NO. ITEM Qty. Unit Rate Unit Amount 

(In Rs. Lakhs) 

Annexure 12.2 

Excise Duty Total Amount 

(In Rs. Lakhs) 

Rate Amount 

(In Rs. 

Lakhs) 

1 2 3 4 5 6 7 8 9 10 

1 Generating Unit and Bus Duct 260 MW,166.7RPM, 

Rated Head 193.21 M 

10 Nos. 0.036 Rs./kW 93600 16% 14976 108576.00 

2 Step up transformer 11/400/ √ 

3 kV, 97 MVA ,Single 

Phase 

31 Nos. 230 Rs./kVA 6916.1 16% 1106.576 8022.68 

3 Auxiliaries Electrical Equipment for power Stations 

( 5% of item 1) 

4680 16% 748.8 5428.80 

4 Auxiliary Equipment and services for power stations 

(5% of item 1) 

4680 16% 748.8 5428.80 

5 Switchyard (kV)-400 kV-GIS 20 bays 600 Rs. Lakhs/bay 12000 16% 1920 13920.00 

6 Spares( 5% of 1 and 3% of 2-5) 5528.283 5528.28 

7 Sub- total(1) 127404.383 19500.176 146904.56 

8 Central Sales Tax @ 4% of item 7 5876.18 

9 Transportation & Insurance @ 6% of item 7 8814.27 

10 Erection and Commissioning @ 8% of item 7 

Except Spares 

11310.10 

11 Sub- total(2) 172905.12 

12 Establishment, Contingency, other Charges @ 11% of 

item 7excluding duties 

14014.48 

GRAND TOTAL 186919.60

13.1 GENERAL 

CHAPTER – XIII 

ECONOMIC EVALUATION 


The economic and financial evaluation of the Kalai 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 10608.64 GWh in a 

90% dependable year. For assessing the tariff, design energy generation of 

10449.52 GWh , calculated with 95% capacity availability in a 90% 

dependable year, has been adopted. The project would provide 2600 MW of 

peaking capacity benefits. 

13.3 CAPITAL COST 

The project cost has been estimated at Rs. 5029.12 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 3159.92 Crores 

2. Cost of Electrical/Mechanical works = Rs 1869.20 Crores 

Total = Rs 5029.12 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 7 years period in all respect with 

full benefit available after 7 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. 6225.17 Crores considering the Interest 

during construction. 

ii) Annual energy generation of 10608.64 GWh in 90% dependable year 

and Design energy of 10449.52 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. 

13.7 CONCLUSION 

First Year 

Tariff Period 

Levellised Tariff 

TABLE – 13.2 

Tariff 

(Rs./KWh) 

1.01 

0.88 

The sale rate of energy indicated above shows that the energy generated 

from the project is financially viable and economically attractive. 

13-3

KALAI HYDEL SCHEME ( Underground Power House ) 

Calculation of Interest During Construction 

Debt : Equity 70 : 30 

Interest rate @ 10 % 

(INR crores) 

Annexure 13.2 

Year Project Equity Loan 

ITERATION - I GRAND TOTAL 

cost component component Cummulative IDC Equity for Loan for TOTAL Capitalised 

(30%) (70%) loan 10.0% IDC IDC IDC IDC cost 

(Civil & E&M) 

(6) x 0.30 (6) x 0.70 10.0% 

1 2 3 4 5 6 7 8 9 10 11 

1 502.91 502.91 0.00 0.00 0.00 0.00 0.00 0.00 0.00 502.91 

2 1005.82 1005.82 0.00 0.00 0.00 0.00 0.00 0.00 0.00 1005.82 

3 1257.28 0.00 1257.28 1257.28 62.86 18.86 44.00 2.20 65.06 1322.34 

4 754.37 0.00 754.37 2011.65 163.45 49.03 114.41 10.12 173.57 927.94 

5 502.91 0.00 502.91 2514.56 226.31 67.89 158.42 23.76 250.07 752.98 

6 502.91 0.00 502.91 3017.47 276.60 82.98 193.62 41.36 317.97 820.88 

7 502.91 0.00 502.91 3520.38 326.89 98.07 228.82 62.49 389.38 892.29 

Total 5029.12 1508.74 3520.38 1056.12 316.83 739.28 139.94 1196.05 6225.17


Phasing of Expenditure 

Year Civil cost E & M cost Total cost 

1 315.99 186.92 502.91 

2 631.98 373.84 1005.82 

3 789.98 467.30 1257.28 

4 473.99 280.38 754.37 

5 315.99 186.92 502.91 

6 315.99 186.92 502.91 

7 315.99 186.92 502.91 

Total 3159.92 1869.20 5029.12 

Annexure -13.1 

INR crores


TARIFF CALCULATIONS WITH PROJECTED COMPLETION COST 

Annexure - 13.3 

Debt:Equity Ratio 7.0 : 3.0 

Yr 1 Yr 2 Yr 3 Yr 4 Yr 5 Yr 6 Yr 7 Yr 8 Yr 9 Yr 10 Yr 11 Yr 12 

BASIC PARAMETERS 

Capacity (MW) 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 

Capital Cost (INR crores) 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 

Capital Cost with IDC . 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 

Equity Portion (%) 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

Debt Portion (%) 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 

Capital Cost/MW (INR crores) 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 

Interest rate for WC (%) 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 

Tax rate (%) 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

Interest rate on loan from Financial Institutions (%) 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 

Total annual energy (GWh) 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 

Design energy with 90% dependibility (GWh) 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 

Saleable Energy after aux. (GWh) 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 

consumption & transformation losses 

FINANCIAL PACKAGE (INR crores) 

LOAN % of % of Intt. AMOUNT EQUITY % of % of AMOUNT 

Loan Component 4357.6 total project Rate (INR total project (INR 

loan cost (%) crores) equity cost crores) 

Fin. Institutions 4357.62 

Equity component 1867.55 Fin. Institutions 100.00 70.00 10.00 4357.62 Equity 100.00 30.00 1867.55 

1867.55 6225.2 

Period Repayment Moratorium Installment/yr. 

Financial Inst. 10 0 1 

Repayment Amount/year 

Financial Institutions 435.76 

Construction Period (Yrs.) 5 

Total 100.00 70.00 4357.62 Total 100.00 30.00 1867.55 

1/12






NORMATIVE PARAMETERS Year 1 2 3 4 5 6 7 8 9 10 11 12 

O & M Charges incl. Insurance (%) 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 

O & M Inflation rate (%) 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 

Rate of return on equity (%) 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 

Rate of Depreciation (ES Act) (%) 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 

Rate of Depreciation (IT Act) (%) 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 

Spares for 1 yr -1/5th C.S 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

Auxiliary consumption (%) 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 

Transformation Losses (%) 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 

SCHEDULE OF LOAN REPAYMENT 

AGENCY Year 1 2 3 4 5 6 7 8 9 10 11 12 

FINANCIAL INSTITUTIONS 

Outstanding Term loan 4357.62 3921.86 3486.10 3050.33 2614.57 2178.81 1743.05 1307.29 871.52 435.76 0.00 0.00 

Term loan installment 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 0.00 0.00 

Cum. Loan Repaid 435.76 871.52 1307.29 1743.05 2178.81 2614.57 3050.33 3486.10 3921.86 4357.62 4357.62 4357.62 

Interest on Term loan 413.97 370.40 326.82 283.25 239.67 196.09 152.52 108.94 65.36 21.79 0.00 0.00 

Total Yearly installment 849.74 806.16 762.58 719.01 675.43 631.85 588.28 544.70 501.13 457.55 0.00 0.00 

LOAN SERVICING 

Outstanding Term loan 4357.62 3921.86 3486.10 3050.33 2614.57 2178.81 1743.05 1307.29 871.52 435.76 0.00 0.00 

Loan Repayment Installment 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 0.00 0.00 

Sources of Funds for Repayment 

- Depreciation (ES Act) 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 0.00 0.00 

- Advance Depreciation 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

- Additional sources (ROE ) 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 0.00 0.00 

COMPUTATION OF TARIFF COMPONENTS 

INTEREST ON CAPITAL 

Interest on Term loan 413.97 370.40 326.82 283.25 239.67 196.09 152.52 108.94 65.36 21.79 0.00 0.00 

Total Yearly Installment 849.74 806.16 762.58 719.01 675.43 631.85 588.28 544.70 501.13 457.55 0.00 0.00 

2/12






RATE OF RETURN 

Equity amount 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 

Return on Equity 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 

O & M EXPENSES 93.38 98.05 102.95 108.10 113.50 119.18 125.13 131.39 137.96 144.86 152.10 159.71 

INTEREST ON WORKING CAPITAL 

WORKING CAPITAL 

O & M Expenses - 1 month 7.78 8.17 8.58 9.01 9.46 9.93 10.43 10.95 11.50 12.07 12.68 13.31 

Spares 1 year - 1/5th cap spares 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

Receivables for 2 months 

DEP(ES Act) 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 

Interest 69.00 61.73 54.47 47.21 39.94 32.68 25.42 18.16 10.89 3.63 0.00 0.00 

Return on Equity 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 

O&M 15.56 16.34 17.16 18.02 18.92 19.86 20.86 21.90 22.99 24.14 25.35 26.62 

I.Tax 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 6.07 38.75 

Interest on W.C. 2.33 2.25 2.18 2.11 2.03 1.96 1.89 1.82 1.75 1.69 1.74 2.16 

Total Working capital 193.23 187.06 180.95 174.90 168.92 163.00 157.16 151.39 145.70 140.10 144.40 179.40 

Interest on Working Capital 18.84 18.24 17.64 17.05 16.47 15.89 15.32 14.76 14.21 13.66 14.08 17.49 

DEPRECIATION (ES ACT) (INR crores) 

Total Depreciable Amount 5602.65 5384.77 5166.89 4949.01 4731.13 4513.25 4295.37 4077.49 3859.61 3641.72 3423.84 3205.96 

Opening Depreciation Fund 0.00 -217.88 -435.76 -653.64 -871.52 -1089.40 -1089.40 -1089.40 -1089.40 -1089.40 -1089.40 -871.52 

Yearly Depreciation (ES Act) 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 

Cumulative Depreciation Fund 217.88 0.00 -217.88 -435.76 -653.64 -871.52 -871.52 -871.52 -871.52 -871.52 -871.52 -653.64 

Loan Repayment Installment 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 435.76 0.00 0.00 

Advance Dep. for loan Repayment 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

Return on Eq. for loan Repayment 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 0.00 0.00 

Closing Cummulative Dep. Fund -217.88 -435.76 -653.64 -871.52 -1089.40 -1089.40 -1089.40 -1089.40 -1089.40 -1089.40 -871.52 -653.64 

Total Depreciation 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 

Net Depreciable Amount 5602.65 5384.77 5166.89 4949.01 4731.13 4513.25 4295.37 4077.49 3859.61 3641.72 3423.84 3205.96 

DEPRECIATION (IT ACT) (INR crores) 

Sum at charge 6225.17 4668.88 3501.66 2626.24 1969.68 1477.26 1107.95 830.96 623.22 467.41 350.56 262.92 

Depreciation (IT Act) 1556.29 1167.22 875.41 656.56 492.42 369.32 276.99 207.74 155.80 116.85 87.64 65.73 

Dep.limited to 90% of capital cost 1556.29 1167.22 875.41 656.56 492.42 369.32 276.99 207.74 0.70 0.00 0.00 0.00 

3/12






TAX LIABILITY (INR crores) 

Yearly Profit/loss -1039.60 -650.53 -358.73 -139.87 24.27 147.37 239.70 308.95 515.99 516.69 516.69 516.69 

Cummulative Profit/loss (+/-) -1039.60 -1690.13 -2048.86 -2188.73 -2164.46 -2017.09 -1777.39 -1468.44 -952.45 -435.76 80.93 597.62 

Tax liability 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 36.42 232.51 

CAPACITY AND ENERGY CHARGES 

Annual Capacity Charge (INR crores) 631.85 588.28 544.70 501.13 457.55 413.97 370.40 326.82 283.25 239.67 217.88 217.88 

Annual Energy Charge (INR crores) 411.03 415.09 419.40 423.96 428.78 433.88 439.27 444.96 450.98 457.33 501.41 708.52 

Total Annual Charge (INR crores) 1042.88 1003.37 964.10 925.08 886.33 847.85 809.66 771.78 734.22 697.00 719.29 926.40 

Average Tariff (INR/kWh) 1.01 0.97 0.93 0.90 0.86 0.82 0.78 0.75 0.71 0.68 0.70 0.90 

Average Tariff for 5 years (INR/kWh) 0.93 0.75 0.87 

Discount rate (%) 12.00 / Year 1 2 3 4 5 6 7 8 9 10 11 12 

Discounted Average Tariff (INR/kWh) 1.01 0.87 0.74 0.64 0.55 0.47 0.40 0.34 0.29 0.24 0.22 0.26 

Levellised Eq.Avg. Tariff (INR/kWh) 0.88 

4/12


Capacity (MW) 

Capital Cost (INR crores) 

Capital Cost with IDC . 

Equity Portion (%) 

Debt Portion (%) 

Capital Cost/MW (INR crores) 

Interest rate for WC (%) 

Tax rate (%) 

Interest rate on loan from Financial Institutions (%) 

Total annual energy (GWh) 

Design energy with 90% dependibility (GWh) 

Saleable Energy after aux. (GWh) 



Loan Component 4357.6 


Equity component 1867.55 

1867.55 6225.2 











2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 

5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 

6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 

30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 

2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 

9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 

30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 

10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 

10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 

10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 

5/12

NORMATIVE PARAMETERS Year 

O & M Charges incl. Insurance (%) 

O & M Inflation rate (%) 

Rate of return on equity (%) 

Rate of Depreciation (ES Act) (%) 

Rate of Depreciation (IT Act) (%) 

Spares for 1 yr -1/5th C.S 

Auxiliary consumption (%) 

Transformation Losses (%) 


AGENCY Year 


Outstanding Term loan 

Term loan installment 

Cum. Loan Repaid 

Interest on Term loan 

Total Yearly installment 



Loan Repayment Installment 


- Depreciation (ES Act) 

- Advance Depreciation 

- Additional sources (ROE ) 




Total Yearly Installment 






13 14 15 16 17 18 19 20 21 22 23 24 

1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 

5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 

16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 

3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 

25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 

12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 

0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 

13 14 15 16 17 18 19 20 21 22 23 24 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

6/12


Equity amount 

Return on Equity 

O & M EXPENSES 



O & M Expenses - 1 month 

Spares 1 year - 1/5th cap spares 


DEP(ES Act) 

Interest 


O&M 

I.Tax 

Interest on W.C. 

Total Working capital 

Interest on Working Capital 


Total Depreciable Amount 

Opening Depreciation Fund 

Yearly Depreciation (ES Act) 

Cumulative Depreciation Fund 


Advance Dep. for loan Repayment 

Return on Eq. for loan Repayment 

Closing Cummulative Dep. Fund 

Total Depreciation 

Net Depreciable Amount 


Sum at charge 

Depreciation (IT Act) 

Dep.limited to 90% of capital cost 






1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 

298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 

167.69 176.08 184.88 194.13 203.83 214.02 224.72 235.96 247.76 260.15 273.15 286.81 

13.97 14.67 15.41 16.18 16.99 17.84 18.73 19.66 20.65 21.68 22.76 23.90 

12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 36.31 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 

27.95 29.35 30.81 32.35 33.97 35.67 37.45 39.33 41.29 43.36 45.53 47.80 

38.75 38.75 38.75 38.75 38.75 38.75 38.75 38.75 38.75 38.75 38.75 38.75 

2.18 2.21 2.24 2.27 2.29 2.33 2.36 2.39 2.43 2.47 2.51 2.55 

181.42 183.55 185.77 188.11 190.57 193.15 195.86 198.70 201.68 204.82 208.11 211.57 

17.69 17.90 18.11 18.34 18.58 18.83 19.10 19.37 19.66 19.97 20.29 20.63 

2988.08 2770.20 2552.32 2334.44 2116.56 1898.68 1680.80 1462.92 1245.03 1027.15 809.27 591.39 

-653.64 -435.76 -217.88 0.00 217.88 435.76 653.64 871.52 1089.40 1307.29 1525.17 1743.05 

217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 

-435.76 -217.88 0.00 217.88 435.76 653.64 871.52 1089.40 1307.29 1525.17 1743.05 1960.93 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

-435.76 -217.88 0.00 217.88 435.76 653.64 871.52 1089.40 1307.29 1525.17 1743.05 1960.93 

217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 

2988.08 2770.20 2552.32 2334.44 2116.56 1898.68 1680.80 1462.92 1245.03 1027.15 809.27 591.39 

197.19 147.89 110.92 83.19 62.39 46.79 35.10 26.32 19.74 14.81 11.10 8.33 

49.30 36.97 27.73 20.80 15.60 11.70 8.77 6.58 4.94 3.70 2.78 2.08 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

7/12


Yearly Profit/loss 

Cummulative Profit/loss (+/-) 

Tax liability 


Annual Capacity Charge (INR crores) 

Annual Energy Charge (INR crores) 

Total Annual Charge (INR crores) 

Average Tariff (INR/kWh) 

Average Tariff for 5 years (INR/kWh) 

Discount rate (%) 12.00 / Year 

Discounted Average Tariff (INR/kWh) 

Levellised Eq.Avg. Tariff (INR/kWh) 






516.69 516.69 516.69 516.69 516.69 516.69 516.69 516.69 516.69 516.69 516.69 516.69 

1114.31 1630.99 2147.68 2664.37 3181.06 3697.75 4214.44 4731.13 5247.82 5764.51 6281.20 6797.89 

232.51 232.51 232.51 232.51 232.51 232.51 232.51 232.51 232.51 232.51 232.51 232.51 

217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 217.88 

716.70 725.29 734.31 743.78 753.73 764.17 775.14 786.65 798.74 811.43 824.76 838.76 

934.58 943.17 952.19 961.67 971.61 982.05 993.02 1004.53 1016.62 1029.32 1042.64 1056.64 

0.91 0.91 0.92 0.93 0.94 0.95 0.96 0.97 0.98 1.00 1.01 1.02 

0.95 1.01 

13 14 15 16 17 18 19 20 21 22 23 24 

0.23 0.21 0.19 0.17 0.15 0.14 0.13 0.11 0.10 0.09 0.08 0.08 

8/12


Capacity (MW) 

Capital Cost (INR crores) 

Capital Cost with IDC . 

Equity Portion (%) 

Debt Portion (%) 

Capital Cost/MW (INR crores) 

Interest rate for WC (%) 

Tax rate (%) 

Interest rate on loan from Financial Institutions (%) 

Total annual energy (GWh) 

Design energy with 90% dependibility (GWh) 

Saleable Energy after aux. (GWh) 



Loan Component 4357.6 


Equity component 1867.55 

1867.55 6225.2 







7.0 : 3.0 

Yr 25 Yr 26 Yr 27 Yr 28 Yr 29 Yr 30 Yr 31 Yr 32 Yr 33 Yr 34 Yr 35 

2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 2600.00 

5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 5029.12 

6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 6225.17 

30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 70.00 

2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 2.39 

9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 9.75 

30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 30.00 

10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 10.00 

10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 10608.64 

10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 10449.52 

10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 10324.49 

9/12

NORMATIVE PARAMETERS Year 

O & M Charges incl. Insurance (%) 

O & M Inflation rate (%) 

Rate of return on equity (%) 

Rate of Depreciation (ES Act) (%) 

Rate of Depreciation (IT Act) (%) 

Spares for 1 yr -1/5th C.S 

Auxiliary consumption (%) 

Transformation Losses (%) 


AGENCY Year 



Term loan installment 

Cum. Loan Repaid 


Total Yearly installment 





- Depreciation (ES Act) 

- Advance Depreciation 

- Additional sources (ROE ) 




Total Yearly Installment 


7.0 : 3.0 


25 26 27 28 29 30 31 32 33 34 35 

1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 1.50 

5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 5.00 

16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 16.00 

3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 3.50 

25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 25.00 

12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 0.70 

0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 0.50 

25 26 27 28 29 30 31 32 33 34 35 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 4357.62 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

10/12


Equity amount 


O & M EXPENSES 



O & M Expenses - 1 month 

Spares 1 year - 1/5th cap spares 


DEP(ES Act) 

Interest 


O&M 

I.Tax 

Interest on W.C. 

Total Working capital 

Interest on Working Capital 


Total Depreciable Amount 

Opening Depreciation Fund 

Yearly Depreciation (ES Act) 

Cumulative Depreciation Fund 


Advance Dep. for loan Repayment 

Return on Eq. for loan Repayment 

Closing Cummulative Dep. Fund 

Total Depreciation 

Net Depreciable Amount 


Sum at charge 

Depreciation (IT Act) 

Dep.limited to 90% of capital cost 


7.0 : 3.0 


1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 1867.55 

298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 

301.15 316.21 332.02 348.62 366.05 384.35 403.57 423.75 444.94 467.19 490.54 

25.10 26.35 27.67 29.05 30.50 32.03 33.63 35.31 37.08 38.93 40.88 

12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 12.45 

36.31 25.94 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 49.80 

50.19 52.70 55.34 58.10 61.01 64.06 67.26 70.63 74.16 77.86 81.76 

38.75 34.08 22.41 22.41 22.41 22.41 22.41 22.41 22.41 22.41 22.41 

2.59 2.45 2.04 2.09 2.15 2.20 2.26 2.32 2.39 2.46 2.53 

215.20 203.78 169.71 173.91 178.32 182.95 187.82 192.92 198.28 203.91 209.82 

20.98 19.87 16.55 16.96 17.39 17.84 18.31 18.81 19.33 19.88 20.46 

373.51 155.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

1960.93 2178.81 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 

217.88 155.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

2178.81 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

2178.81 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 2334.44 

217.88 155.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

373.51 155.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

6.25 4.68 3.51 2.64 1.98 1.48 1.11 0.83 0.63 0.47 0.35 

1.56 1.17 0.88 0.66 0.49 0.37 0.28 0.21 0.16 0.12 0.09 

0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

11/12


Yearly Profit/loss 

Cummulative Profit/loss (+/-) 

Tax liability 


Annual Capacity Charge (INR crores) 

Annual Energy Charge (INR crores) 

Total Annual Charge (INR crores) 

Average Tariff (INR/kWh) 

Average Tariff for 5 years (INR/kWh) 

Discount rate (%) 12.00 / Year 

Discounted Average Tariff (INR/kWh) 

Levellised Eq.Avg. Tariff (INR/kWh) 


7.0 : 3.0 


516.69 454.44 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 298.81 

7314.58 7769.01 8067.82 8366.63 8665.44 8964.25 9263.05 9561.86 9860.67 10159.48 10458.29 

232.51 204.50 134.46 134.46 134.46 134.46 134.46 134.46 134.46 134.46 134.46 

217.88 155.63 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

853.45 839.38 781.84 798.85 816.71 835.46 855.16 875.83 897.54 920.34 944.27 

1071.33 995.01 781.84 798.85 816.71 835.46 855.16 875.83 897.54 920.34 944.27 

1.04 0.96 0.76 0.77 0.79 0.81 0.83 0.85 0.87 0.89 0.91 

0.82 0.87 

25 26 27 28 29 30 31 32 33 34 35 

0.07 0.06 0.04 0.04 0.03 0.03 0.03 0.03 0.02 0.02 0.02 

12/12

CHAPTER - I EXECUTIVE SUMMARY - Ministry of Power

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?