Emini

CHAPTER 

TABLE OF CONTENTS 

DETAILS 

i 

Preliminary Feasibility Report 

Emini H E Project 4 X 125 MW 

PAGE 

NO. 

CHAPTER I Summary 1-12 

CHAPTER II Background Information 13-18 

CHAPTER III Project Area 19-20 

CHAPTER IV 

Topographic & Geo-technical 

Aspects 

21-32 

CHAPTER V Hydrology 33-52 

CHAPTER VI Conceptual Layout and Planning 53-70 

CHAPTER VII Power Potential Studies 71-96 

CHAPTER VIII Power Evacuation 97-99 

CHAPTER IX Environmental Aspects 100-118 

CHAPTER X Infrastructure 119-122 

CHAPTER XI Construction Planning & Schedule 123-128 

CHAPTER XII Cost Estimates 129-160 

CHAPTER XIII Economic Evaluation 161-168 

APPENDIX Plates / Drawings 169-185 

Annexures 186-263

CHAPTER 

NO 

TABLE 

NO 

LIST OF TABLES 

ii 



TITLE PAGE 

NO 

II 2.1 Power Position of North Eastern 

Region 

16 

II 2.2 Power Position of All India 17 

V 5.1 Observed Temperature and 

Humidity at Hunli 

V 5.2 Observed Temperature and 

Humidity at Elopa 

V 5.3 Maximum Temperature at Anini 39 

V 5.4 Minimum Temperature at Anini 39 

V 5.5 Status of rain gauge data in 

Dibang Basin 

40 

V 5.6 Average Monthly Rainfall In Dibang 

Basin (mm) 

V 5.7 Rainfall Correction Factor 44 

V 5.8 Flood Computed by Various 

Methods 

49 

V 5.9 Average 10 daily discharge 

(Cumec) at Dam site 

VII 7.1 Discharge Data 76 

VII 7.2 90% Dependable Year Flow for 

Power Generation 

VII 7.3 Reservoir Operation Report 78 

VII 7.3A Availability of Units in 90% 

Dependable Year 

VII 7.4 Reservoir Operation Study 80 

37 

38 

43 

52 

77 

79

VII 7.5 Power Potential in 90% 

Dependable Year. 

iii 



VII 7.6-7.20 Reservoir Operation Study 82-96 

XIII 13.1 IDC Calculation at Present Day 

Cost 

XIII 13.2 Unit Cost of Energy at Bus Bar at 

Current Price Level 

81 

164 

165 

XIII 13.3 Energy Rate with Present Cost 166 

XIII 13.2A Unit Cost of Energy at Bus Bar at 

Current Price Level without Free 

Power to Home State 

XIII 13.3A Energy Rate with Present Cost 

without Free Power to Home State 

167 

168

Chapter 

No 

Plate 

No 

PLATES / DRAWINS 

iv 



Title Page No 

II 2.1 Vicinity Map 169 

II 2.2 Cascade Development in Mathun 

Basin 

IV 4.1 Geological Plan Of The Project 

Area 

IV 4.2 Tentative Geological Section 

V 5.1 

along Dam Axis 

Hydroelectric projects proposed 

in Dibang Valley 

V 5.2 Catchment Plan of Emini H.E 

Project 

170 

171 

172 

173 

174 

V 5.3 Area Capacity Curve 175 

VI 6.1 General Layout 176 

VI 6.2 General Layout of Longitudinal 

Section 

177 

VI 6.3 Layout Plan of Dam Area 178 

VI 6.4 Dam Upstream Elevation 179 

VI 6.5 Dam Cross Sections 180 

6.6 Water Conductor System 

Cross Section 

181 

VI 6.7 Layout Plan of Power House 

Area 

182 

VI 6.8 X Section of Power House 183 

VIII 8.1 Single Line Diagram 184 

VIII 8.2 Dibang Basin- Power Evacuation 

System 

184A 

XI 11.1 Construction Schedule 185

LIST OF ANNEXURE 

v 



CHAPTER ANNEXURE TITLE PAGE 

IV 4.1 Information received from 

Geological Survey of India on 

general geology of Project Area 

V 5.1 The observations received from 

CWC vide letter No 4/330/2003 

Hyd NE/336-37 dated 

21/10/2003 and reply of NHPC 



Hyd NE/357 dated 21/10/2003 

and reply of NHPC 



Hyd NE/56-57 dated 03/02/2004 

and reply of NHPC 

VI 6.1 Excerpts from CEA’s 

VI 6.2 

reassessment study report 

Record note of discussion with 

CEA regarding vetting of layout 

VI 6.3 Comments of CMDD 

Directorate, CWD and reply of 

NHPC 

VII 7.1 Summary Record of discussion 

with CEA regarding power 

potential studies. 

VII&VIII 8.1 Comments of SP&PA Division, 

CEA vide UO no 82/18/2003- 

SP&PA dated 23.10.03 and 

reply of NHPC. 

IX 9.1 Report from NRSA, Hyderabad 

on satellite remote sensing based 

inputs for initial environmental 

studies for Agoline H.E. project 

site 

NO 

186-193 

194-204 

205-210 

211-215 

216-218 

219-222 

223-226 

227-230 

231-246 

247-263

GLOSSARY 

CEA Central Electricity Authority 

D/S Downstream 

EL Elevation 

FRL Full Reservoir Level 

FSL Full Supply Level 

G & D Gauge & Discharge 

GSI Geological Survey of India 

Ha Hectare 

IDC Interest during Construction 

km Kilometre 

km 2 

Square kilometre 

KW Kilo Watt 

kwh Kilo Watt Hour 

LR Lower Reservoir 

LS Lump Sum 

A.P. Arunachal Pradesh 

M 3 

Cubic Metre 

M 3 /s Cubic Metre per second 

MDD Maximum Dry Density 

MDDL Minimum Draw Down Level 

mm Millimetre 

Mm 3 

Million cubic metre 

MSL Mean Sea Level 

MW Mega Watt 

MWL Maximum Water Level 

vi 



NHPC National Hydroelectric Power Corporation Ltd. 

o C Degree Celcious 

GREF General Reserve Engineering Force 

P.A.F Project Affected People 

U/S Upstream

vii 



I. Summary

viii 



II. Background 

Information

ix 



III. Project Area

x 



IV. Topographic & 

Geo-technical 

Aspect

xi 



V. Hydrology

xii 



VI. Conceptual 

Layout & Planning

xiii 



VII. Power Potential 

Studies

xiv 



VIII. Power 

Evacuation

xv 



IX. Environmental 

Aspects

xvi 



IX. Infrastructure

xvii 



XI. Construction 

Planning & Schedule

xviii 



XII. Cost Estimate

xix 



XIII. Economic 

Evaluation

1.1 INTRODUCTION 

CHAPTER - I 

SUMMARY 

1 


Emini HE Project 4 X 125 MW 

Emini H.E. Project is located in a remote area of Dibang valley 

district of Arunachal Pradesh. The project envisages utilisation of 

water of river Mathun or Adzon. Mathun is a tributary of Dri or 

Dibang river. Dibang river is the tributary of river Brahmaputra. 

To exploit hydro potential and to derive benefits of flood 

moderation, DPR of Dibang multipurpose project (3000 MW) is 

under preparation by Brahmaputra board in association with CWC/ 

CEA . CEA has also identified ten number of schemes in Dibang 

basin in addition to Dibang Multi Purpose Project in their ranking 

studies. These ten additional projects in Dibang Basin (Arunachal 

Pradesh) are as a part of exercise for development of balance 

hydroelectric potential in the country and accorded priority for 

preparation of Preliminary Feasibility Report (PFR) so that these 

could be taken up for preparation of Detailed Project Report (DPR) 

and further development during the XI and XII Five Year Plans. 

The Emini project is one of the above ten schemes in Dibang basin. 

CEA’s reassessment study report envisaged construction of a 

diversion structure of a small height on the Mathun river at a site 

where the river bed level is +1200m and leading the water to a 

power house through a 6.5 km long channel. The scheme would 

utilise a gross head of 115 m and enable a firm power generation of 

39MW. With an optimum generating capacity 295MW, the scheme

2 



would enable energy generation of 1160 Gwh and 1333 Gwh 

respectively in 90% and 50% dependable years. 

Based on Topographical, Geological and Hydro meteorological 

studies of the area, a few modifications have been 

made in the layout of the project. The dam is proposed to 

be located downstream of confluence of Kanji rivulet with Mathun 

river at riverbed level of EL +1200 m. The power house is 

proposed with tail race bed level at EL+1118 m. Keeping in view 

of steep topography and river bend available, a Headrace tunnel of 

about 5 km in length has been proposed to be provided in place of 

the proposed open channel of 6.5 km length. Installed capacity of 

this project would be 500MW (4 X 125 MW) instead of 295 MW 

as indicated in reassessment studies of CEA. 

1.2 GENERAL PROJECT FEATURES 

The Emini HE Project envisages construction of: - 

> River diversion works comprising of one 12 m diameter 

horseshoe shaped diversion tunnel with u/s and d/s 

cofferdams. 

> 85 m high concrete gravity dam from deepest foundation level 

> To provide a gross storage of 47 Mcum at FRL of EL 1270 m 

and a gross storage of 34 Mcum at MDDL of EL 1260 m . 

> Spillway comprising of (a) low level orifice spillway - 5 nos 

of opening size 7 m X 10 m with crest elevation at EL 1230m 

and (b) crest type spillway - 2 nos of opening size 7.0 m X 

10.0m with crest elevation at EL 1260 m

3 



> 4 nos of Desilting chambers of length 350m (L) and size 

18 m (W)X 25 m (H) to remove silt particle of size 0.2mm 

and above. 

> 2 nos 5km long 8 m diameter horseshoe shaped headrace 

tunnel. 

> 2 nos 75 m high 25 m diameter surge shaft. 

> 2 nos 7.0 m diameter steel lined pressure shaft with vertical 

height 115 m. 

> An underground power house with an installation of 4 units of 

125 MW each having overall size 120 m (L) X 24 m (W) X 

45 m (H) . 

> 2 nos 8 m diameter horseshoe shaped tailrace tunnel to carry 

the power house release back to the river. 

1.3 SALIENT FEATURES 

1.3.1 LOCATION 

State : Arunachal Pradesh 

River : Adjon/ Mathun river 

Dam site : D/S of confluence of Kanji rivulet 

with Mathun river 

Nearest airport : Dibrugarh 

Nearest Railhead : Tinsukia 

1.3.2 

HYDROLOGY 

Catchment area : 2600sq.km. 

Location of catchment 

Latitude : 28 o 45'N, 29 o 30’N 

Longitude : 95 o 30'E, 96 o 10'E 

Average annual 

rainfall 

: 4023mm 

Formatted: Bullets and Numbering

4 



1.3.3 RESERVOIR 

Full reservoir level : 1270 m 

(FRL) 

Min.Draw Down Level 1260 m 

(MDDL) 

Gross storage 

-at FRL : 46.555 mcm 

-at MDDL : 

Area under 

34.060 mcm 

submergence at FRL : 166 ha 

1.3.4 DIVERSION TUNNEL 

Number : 1 

Size : 12 m 

Shape : Horse shoe 

Length : 700m 

Diversion discharge : 1600 cumec 

( assumed) 

U/s coffer dam : 25 m 

D/s coffer dam : 12 m 

1.3.5 DAM 

Type : Concrete Gravity 

Top elevation of dam : 1275 m 

Height of dam above : 85 m 

deepest foundation 

level 

Length of dam at top : 335 m 

River Bed level 1200 m 

1.3.6 SPILLWAY 

Design flood : 7000 Cumec 

Lower spillway 

Type : Orifice type 

Crest elevation : 1230m 

Number : 5 

Size of opening : 7 m x 10m

5 



Upper spillway 

Type : Crest type 

Crest elevation 1260 m 

Number : 2 

Size of opening : 7 m x 10 m 

Length of spillway : 105 m 

Energy dissipation 

: 

Ski jump with preformed 

plunge pool 

1.3.7 INTAKE 

Invert level : 1240 m 

Number : 2 

Size of gate opening : 7.9m x 9 m 

Trash rack : 19 x 20 m 

1.3.8 DESILTING CHAMBERS 

Number : 4 

Size : 18 m x 25 m 

Length : 350 m 

Design discharge : 135.6 each 

per chamber 

Particle size to be : 0.20 mm and above 

removed 

1.3.9 HEAD RACE TUNNEL 

Number : 2 

Size : 8 m 


Length : 5 km 

Design discharge 

per tunnel : 222cumec 

1.3.10 SURGE SHAFT 

Number : 2 

Size : 25 m dia 

Height 75 m 

1.3.11 PRESSURE SHAFT 

Number : 2 

Size : 7 m dia. steel lined 

Vertical height : 115 m

6 



1.3.12 POWER HOUSE 

Type : Underground 

Installed capacity : 500MW 

Number of units : 4 (125MW each) 

Power house cavern 

size 

: 120m(L)X24m(W)X45m(H) 

Type of turbine : Vertical Francis 

1.3.13 DRAFT TUBE GATE CUM TRANSFORMER CAVERN 

Cavern size 100m (L) X 20 m (W)X25m(H) 

Draft tube opening for : 11m X 5m with one 2 m wide 

each unit 

intermediate pier 

1.3.14 TAILRACE 

TUNNEL 

Number : 2 

Size : 8 m 


Length 

Design discharge per 

: 250 m 

tunnel 

: 

222 cumec 

River bed level 1118m 

Maximum TWL 1128 m 

1.3.15 POTHEAD YARD 

Size : 25m (W) X 60 m (L) 

1.3.16 POWER 

GENERATED 

Installed capacity : 500 MW 

Annual energy 

Generation in 90% 

dependable year : 1695.45 MU 

1.3.18 COST ESTIMATE & FINANCIAL ASPECT 

(Rs.Crores) 

Civil Works : 2246.39 

Electromechanical 

Works including 

: 492.82

transmission 

7 



Total (Hard Cost) : 2739.21 

Interest during 

construction 

: 327.99 

Grand total (including 

IDC) 

: 3067.20 

Tariff for first year 

With 12% free power 

to home state 

Without 12% free 

power to home state 

Levellised Tariff 

With 12% free power 

to home state 

Without 12% free 

power to home state 

1.4 STUDIES UNDERTAKEN 

: 

: 

: 

: 

Reconnaissance of the area for locating probable alternative 

sites of project component. 

Study of topoxraphic maps. 

Geological appraisal of the of the proposed project 

components. 

Study of regional geo-technical features / seimotectonic 

aspects. 

Power potential studies. 

Conceptual layout and project planning. 

3.99 

3.51 

3.24 

2.85

8 



Study of biotic environment, socio-economic environment 

for prediction of environmental impacts of the project. 

Water availability, design flood studies based on available 

meteorological/ hydrological data. 

Study of existing infrastructure. 

Cost benefit and Economic evaluation. 

1.5 RESULTS OF STUDIES AND INVESTIGATIONS: - 

1.5.1 GEOLOGY 

The Project area falls within the Diorite-Granodiorite-Granite 

complex of the Upper Dibang Valley. The granodiorite/diorite 

exposed in the area is medium to coarse grained, mesocratic, 

greenish-grey rock and consist of plagioclase, quartz, potash 

feldspar and several other mafic minerals (epidote, Biotite, 

amphibole, apatite, sphene, chlorite, etc.). Granodiorite grades into 

Granite with a gradual increase in quartz & K-feldspar content. It 

shows gneissocity in many areas. The rock is intruded by several 

quartz & pegmatite veins ranging in thickness from less than one 

meter to more than 10 meters. 

1.5.2 HYDROLOGY 

The river Mathun drains a catchment area of about 2600 sq.km. at 

the proposed dam site. The water availability for the project has 

been considered on the basis of 10-daily discharge series at Munli 

dam site for the period 1985-2001. The water availability at the 

Emini dam site has been derived from above data on the basis of 

catchment area proportion and applying an overall reduction factor

9 



of 15%. The computed inflow series worked out has been utilized 

for Power Potential Studies. The design flood has been assessed as 

7858 cumecs. 

1.5.3 POWER POTENTIAL STUDIES 

The computed inflow series for 16 years viz. 1985-86 to 2000-01 

has been considered in the assessment of a power benefits from the 

project. As per GOI notification for tariff the year 1994-95 

corresponds to 90% dependable year. An installation of 500 MW 

comprising 4 generating units of 125MW has been proposed. The 

energy availability from the project in a dependable and an average 

year has been summarized below : 

Particulars Dependable Year 

Annual Energy Generation 

Annual Energy Generation (GWh) 1695.45MU 

Annual Load Factor (%) 38.71% 

Generation during Lean Flow Season (Dec.-Feb.) 

Power Output (MWc) 118.19 MW 

Load Factor (%) 23.50% 

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

dependable year has been worked out at 1695.45 GWh. 

A live storage of 12.50 mcum has been provided which would 

enable the station to operate as peaking station. The live storage is 

equivalent to 3917.19MWh which sufficient to operate the station 

for 7.8 hours.

1.5.4 POWER EVACUATION SYSTEM 

10 



The power generated from the project would be evacuated through 

220 kV, double circuit lines to a pooling station near Anini to feed 

into the Grid, which in turn connected, to National Grid. 

1.5.5 ENVIRONMENTAL ASPECT 

Emini H.E project is a run of the river scheme. The climate of the 

foot hills is tropical while in the mountains , temperature decreases 

rapidly with altitude. The total area required for the project is 1251 

ha and the area coming under submergence is about 166ha. The 

land use pattern of the submergence and catchment area has been 

studied by NRSA, Hyderabad using LISS-III +PAN merged 

satellite data. Project area has fairly good forest cover and serves as 

habitat for many faunal species. Some of the species found in the 

area are Terminalia myriocarpa , Duabanga grandiflora, 

Bischofolia javanica, Bombax ceiba, Dillenia indica, 

Largestroemia speciosa and Albizzia sp. All the projects 

components are beyond 7 kms from Dibang Wild Life Sanctuary. 

Agriculture is the main occupation of the people. No village is 

likely to be affected by construction of this project. However 

detailed socio-economic survey would be carried out to ascertain 

the population affected (if any). The impact of the proposed Emini 

HE Project would be assessed in detail during environmental 

impact assessment studies. 

1.5.6 INFRASTRUCTURE 

Since the infrastructure development in the project area or its 

vicinity is not very encouraging, the project has to do meticulous 

planning for development of Infrastructure such as road

11 



communication network, residential/non-residential building, 

workshop, stores and explosive magazine, fueling station, 

construction power, telecommunication etc. required for the 

project. 

1.5.7 CONSTRUCTION SCHEDULE 

The Project has been planned to be constructed in 7.5 years 

including 1.5 years for infrastructure development during stage II 

activities. 

1.5.8 ESTIMATE OF THE COST 

The project is estimated to cost Rs. 3067.20 crores including IDC 

at June, 2003 price levels. The preliminary cost estimate of the 

project has been prepared as per guidelines of CEA/CWC. The 

break down of the cost estimates is given below : 

Civil works : Rs. 2246.39Crores 

Electro Mechanical Works 

including transmission : Rs. 492.82 Crores 

Total (Hard Cost) : Rs. 2739.21 Crores 

Interest During Construction : Rs 327.99 Crores 

Grand Total : Rs. 3067.20 Crores 

1.5.9 FINANCIAL ASPECT 

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

of Rs. 3067.20crores (including IDC of Rs. 327.99crores) and 

design energy of 1695.45 GWh in a 90% dependable year is 

proposed to be completed in a period of 7.5 years. The tariff has 

been worked out considering a debt-equity ratio of 70:30, 16%

12 



return on equity, annual interest rate on loan at 10% and 12% of 

energy as Free power to Home State available after losses. The 

tariff for first year and levellised tariff with free power to home 

state have been work out Rs. 3.99/kWh and Rs. 3.24/kWh 

respectively. The first year and levellised tarrif without free power 

to home state works out to be Rs. 3.51/KWh and Rs 2.85/KWh 

respectively. 

1.6 CONCLUSION 

Emini HE Project can be completed in 7.5 years (including 1.5 

years of stage II activities). The project would afford design energy 

of 1695.45 GWh in a 90% dependable year. The cost per MW 

installed capacity works out to Rs. 6.13 crores. The Preliminary 

Feasibility Report indicates that the scheme has the merit of 

consideration for taking up for Survey and Investigation and 

preparation of DPR. 

Deleted: 1.5 Cost and Financial 

Aspects 

 

The project is estimated to cost Rs 

2028.05 crore excluding IDC at 

June,2003 price level. The estimated 

IDC is as below. 

IDC with estimated present cost Rs 

215.12 crores. 

IDC with completed cost Rs 

235.96 crores. 

 

The levellised tariff of the project at 

present day cost and completion cost 

works out to be per Rs. 3.08 unit and Rs. 

3.51 per unit respectively at powerhouse 

bus bars.

CHAPTER-II 

BACKGROUND INFORMATION 

13 



2.1 GENERAL INFORMATION ABOUT THE AREA, 

RIVER/BASIN/SUB-BASIN. 

Emini HE project is located in a very remote area of Dibang valley 

District of Arunachal Pradesh (Refer Plate 2.1). The dam site is 

located at downstream of the confluence of Kanji rivulets with 

Mathun River near village Maron, which is below 9 km. point on 

Anini-Mipi road from Anini. Further 7 km road will be required to 

be constructed to reach the dam site. Cane bridges exist to cross to 

the right bank of the river. Villagers utilise it for going to the forest 

area and for cultivation purposes. 

Power house site is located on the right bank of Mathun River just 

upstream of confluence of Igu pani rivulet with Mathun River. The 

Power House site is approachable from 18 Km. point on Anini- 

Roing Road. About 10 kms roads is required to be constructed to 

reach the Power House location from 18 km point. Two bridges 

shall be required for crossing Dibang River and Igu pani Nallah. 

The main inhabitants of the area are Idu Mishmis and Adis. The 

hill areas and part of plains adjacent to the foothills are mainly 

occupied by Mishmis. Adis have migrated to the plains of the 

valley.

14 



About 42% of the people are literate. But majority of them depend 

mainly on Agriculture. The major agriculture crops are rice, millet, 

maize and wheat. 

Emini project is located on Mathun River, a major tributary of 

Dibang River. Mathun has a river length of about 80 km upto 

confluence with Dri and catchment area of 2600 sq km. at Emini 

Dam. It originates from high ranges of Himalayas. Mathun River 

as it flows down meets Andra River from right and several 

nallahs/streams like Kanji, Imu etc. before finally meeting with Dri 

R from right. The gradient of the river is sufficiently steep and 

flows through narrow valleys. The entire catchment lies in Indian 

territory and are subjected to heavy rainfall. Cascade Development 

of Mathun Basin has been enclosed as Plate 2.2. 

Area falls partly within the climatic zone-I and partly in zone III. 

Climate in zone I is generally tropical monsoon Climate. Rainfall 

normally occurs during May to October in the monsoon period 

while the months of November to February are generally dry. 

Occasional rainfall occurs during April and May. The climate in 

Zone-II can be classified as “Mountain climate”. 

2.2 POWER SCENARIO & EXISTING INSTALLATION 

The power system in India has grown from small, isolated stations, 

serving limited consumers in and around large cities, into large 

regional Grids. The generating capacity installed in the country has 

already grown to 107643.70 MW by March 2003. 

At present Arunachal Pradesh Electricity Board has its own hydel 

generation of 32.52MW and diesel generation of 23.64 MW.

15 



Share of Arunachal Pradesh in Central Sector Power Generation is 

around 117.0 MW which includes gas based power projects. 

The objective of the system development is to evolve self- 

sufficient regional grid catering to the individual regional power 

demands. It is also aimed at achieving the maximum benefits from 

integrated operation, through a proper mix of thermal and hydro 

generation and ultimately to tie the five regional grids together to 

form a Strong National Power Grid, providing even greater 

reliability. 

2.3 NECESSITY OF THE PROJECT & RELATED 

ASPECT 

The power position in the North Eastern region and all India power 

supply position have been summarized in Table-2.1 and Table-2.2. 

The benefits from all schemes that have been cleared by CEA have 

been included. 

Even considering the co-ordinated operation of existing hydro, 

nuclear and thermal stations as well as benefits from ongoing 

projects and also from the scheme cleared by CEA and 

programmed for implementation in 10 th Plan, the regions are 

expected to face power deficit in 10 th five year plan. The regions 

will continue to remain in deficit in 11 th Five year plan also except 

in North-Eastern region as it is evident from Table-2.1 even if all 

the cleared projects till date are implemented. The surplus in 

North-Eastern region is planned to be exported to regions having 

deficit. However, country as a whole remains in deficit both in 

peak capacity and energy by the end of 11 th plan as shown in 

Table-2.2.

SPACE FOR TABLE 2.1 

16 


Emini HE Project 4 X 125 MW

SPACE FOR TABLE 2.2 

17 



CHAPTER III 

PROJECT AREA 

18 



3.1 DESCRIPTION OF PROJECT INCLUDING RIVER 

SYSTEM 

Emini HE project is located in Dibang valley District of Arunachal 

Pradesh. The district headquarter is at Anini which is around 230 

kms from Roing, the district headquarter of Lower Dibang Valley 

District. Roing is at about 108 kms from Tinsukia, the nearest 

Railhead. The nearest Airport is at Dibrugarh about 50 kms from 

Tinsukia. 

The dam site is located at downstream of the confluence of Kanji 

rivulets with Mathun River near village Maron, which is below the 

9 km. point on Anini-Mipi road from Anini. From road head point 

to dam area, about 7 kms road will be required to be constructed on 

the left bank of Mathun river. There are two families in Maron 

village. They will be required to be shifted to other suitable 

location. 

The river bed level at dam site area is 1200m. 

Power house site is located on the right bank of Mathun River just 

upstream of confluence of Igu pani rivulet with Mathun River. The 

Power House site is approachable from 18 Km. point on Anini- 

Roing Road. About 10 kms roads is required to be constructed to 

reach the Power House location from 18 km point.

19 



Emini project is located on Mathun River, a major tributary of 

Dibang River. Mathun has a river length of about 80 km upto 

confluence with Dri River and catchment area of 2600 sq km. It 

originates from high ranges of Himalayas. Mathun River as it flows 

down meets Andra River from right and several nallahs/streams 

like Kanji, Imu etc. before finally meeting with Dri River from left. 

The gradient of the river is sufficiently steep and flows through 

narrow valleys. The entire catchment lies in Indian territory and are 

subjected to heavy rainfall. 

3.2 SOCIO ECONOMIC AND OTHER ASPECTS 

Dibang Valley District is almost entirely hilly and covered mostly 

by forests which is almost 52% of the total geographical area of the 

valley. 

The main inhabitants of the area are Idu Mishmi and Adis. The hill 

areas and part of plains adjacent to foothills are mainly occupied by 

Mishmis. Adis have migrated to plains of the valley. The Idus have 

a rich culture and believe” Nani-Intaya”, the almighty Goddess. 

They also believe in the existence of “Khinu”, an evil spirit whom 

they propitiate to cure various types of illness. Women are expert 

weavers of exquisite qualities and the men have reputation of 

producing beautiful cane and bamboo products. ‘Reh’ is the 

festival of Idus celebrated in the month of February and March. 

This is observed by individuals for well being as well as for social 

prominence.

20 



About 42% of the population is literate but majority of it depend 

mainly on Agriculture. About 83% of the households live below 

poverty line with annual income less than Rs.20000/-. 

Some socio-economic upliftment schemes are under 

implementation in the area by State Govt. Also after coming up of 

hydropower projects in any area, the people in that locality and 

around will experience an economic and social upliftment with 

enhanced opportunities in employment, area development. 

Socio economic and other aspects such as population, literacy, 

agriculture, horticulture & small scale industries, education, 

medical &public health, trend of socio-cultural and religious 

changes during the last decade have been discussed in detail in 

chapter IX i.e., Environmental Aspects.

CHAPTER- IV 

21 



TOPOGRAPHIC AND GEOTECHNICAL ASPECTS 


The geological studies were conducted for the preparation of the 

pre-feasibility report of Emini Hydroelectric Project. The regional 

geology was gathered from Geological Survey of India and the 

available publications including publications of Geological Society 

of India. Reconnaissance survey of the project area was conducted 

to study the surface geology. GSI report on general geology of the 

Project is placed as Annexure 4.1. 

4.2 REGIONAL GEOLOGY 

Arunachal Pradesh and its contiguous territories exhibit 

tectonically distinct geological domains occurring in intimate 

spatial association. In this part of the state two young mobile belts 

E-W Eastern Himalaya and N-S Indo-Maynmar mobile belts meet 

almost at right angles to each other. The original character of the 

junction has been overprinted by NW trending Mishmi Block, 

which now, forms the orographic linkage between the mobile belts. 

The Emini Hydroelectric Project falls in this Mishmi Block and is 

located on river Mathun in Dibang District of Arunachal Pradesh. 

The distinctive techno-geological provinces of this part of the 

Arunachal Pradesh Himalayas can be divided into following four 

segments having well-defined stratigraphy and structures with 

major tectonic features/lineaments separating each segment.

1. Eastern Himalayan Mobile Belt: 

22 



Rises abruptly from the Brahamputra plain & merges with Tibetan 

plateau in the north; covers about 350km of eastern most part of 

Himalaya, referred to as Arunachal Himalaya and extends from 

eastern Nepal in the west to the West Siang district of Arunachal 

Pradesh in the east terminating against N-W trending 

parametamorphites and diorite-granodiorite complex of Mishmi 

Block of Lohit / Dibang district of Arunachal Pradesh. As 

epitomized elsewhere in western sector of the Himalayan mobile 

belt, the Eastern Himalaya mobile belt also embodies a succession 

of northerly dipping thrust sheets that amuse almost the whole of 

Arunachal Pradesh. Deep erosion along these thrust contact brings 

about the four well known E-W trending physiographic units of the 

Eastern Himalaya namely Sub-Himalaya, Lesser Himalaya Higher 

Himalaya and Tethyan belt or Tibetan Himalaya. North of it lies 

zone of Indus-Tsangpo suture. 

2. Mishmi Block: 

The Himalaya at its eastern end gets terminated along the Tidding 

Suture and meets another chain of mountains – the Mishmi Hills, 

which are the part of Mishmi Block mobile belt. These mountain 

ranges, trending northwest-southeast, are said to be a continuation 

of the hill ranges of northern Mayanmar (Burma), but are also 

considered to be in continuation of the Laddakh ranges lying to the 

north of the Indus-Tsangpo Suture. These are made up of NW-SE 

trending diorite-granodiorite complex with a frontal (southeastern) 

belt of high grade schist and migmatites, and inner (northeastern)

23 



belt of low grade schist with crystalline limestone and serpentinite 

lenses of Mishmi block which are collectively referred to Mishmi 

Complex or Lohit Complex and exist in the northeastern and 

eastern corner of Arunachal Pradesh. The Mishmi Block abuts 

against the Naga-Patkai ranges of Arakan-Youma mountains to the 

south along another tectonic plane – the Mishmi Thrust. Important 

tectonic elements in this block are Mishmi thrust, Tidding suture, 

Lohit thrust and Po Chu fault. 

3. Indo- Myanmar (Burmese) Mobile Belt: 

The Patkoi-Naga-Manipur-Chin Hills-Arakan Yoma region forms 

a westerly convex arcuate belt in the eastern part of the Arunachal 

Pradesh, which is an eastern portion of the Indo-Myanmar 

(Burmese) mobile belt and is made up of Paleogene-Neogene 

sediments. 

4. Brahmputra plain: 

This is an ENE-WSW trending relatively narrow valley bounded 

by two young mountain belts to the north and southeast, Mishmi 

Block to the northeast and Meghalaya Plateau to the south. The 

valley is filled by thick alluvium with a few inselbergs of basement 

rocks from Tezpur westward. Almost flat lying Tertiary shelf 

sediments overlie the basement whose thickness increases from 

south to north towards Himalaya. A brief southwest to northeast 

lithotectonic/ lithostratigraphic succession compiled from various 

literatures such as Acharyya, 1980, Singh, & Malhotra 1983, 

Gopendra Kumar, 1997, Nandi, 2001 etc. is given hereunder:

Group/ 

Formation 

Mishmi 

Massive 

Main Lithology 

Diorite-granodiorite 

24 



Medium to coarse grained 

diorite gneiss, hornblende 

granodiorite, coarse grained 

biotite leuco-granodiorite 

with hornblende schist, 

amphibolite, metadolerite, 

metanorite and minor 

xenoliths of high grade 

parametamorphic rocks and 

crystalline marble. 

-------------------------------------Lohit Thrust ----------------------------- 

Tidding 

Group 

Pale green, fine to 

medium grained, low 

grade metamorphic 

rocks 

Chlorite-epidote schist, 

serpentinites, crystalline 

limestone, chorite-biotiteactinolite 

schist, probably 

derived from the basic 

volcanics and volcanogenitic 

rocks. 

-----------------------------------Tiding Suture------------------------------- 

Lohit 

Group 

Predominantly 

metamorphosed 

argillaceous & 

arenaceous rocks 

partly migmatised, 

minor crystalline 

limestone and 

garnetiferous 

amphibolite 

Mica schist 

Garnetiferous amphibolite 

Impure crystalline limestone 

Coarse grained garnetiferous 

kyanite-staurolite 

(sillimanite) schist 

Garnetiferous graphite-schist 

Feldspathic micac. Quartzite 

Augen & lit-par-lit gneiss 

with calcsilicate boudins 

Quartz-garnet-schist 

Quartz-sericite-schist

4.3 GEOMORPHOLOGY 

25 



The area is characterised by rugged hills with steep gorges and 

deep valleys through which Mathun river the main tributary of 

Dibang river flows. Mathun river joins the other rivulet named as 

Dri river just downstream of the proposed power house location of 

the Emini H. E. Project and thereafter the river is named as Dri or 

Dibang river. The main rivers draining the area are Mathun & Dri/ 

Dibang. The drainage of this area is controlled mainly by structural 

features like joints, minor faults etc. The first order stream shows 

dendrite drainage pattern whereas second to higher order streams 

shows sub-parallel to trellis pattern. The mountain slopes are 

usually steep. 

4.4 GENERAL GEOLOGY OF THE PROJECT AREA 

The Project area forms a part of diorite granodiorite complex of 

Mishmi massive consisting of mainly granodiorite and diorite. 

Granodiorite which is present almost in entire project area is a 

medium to coarse grained, mesocratic greenish grey and consists of 

plagioclase, quartz, potash feldspar and other ferromagnesian 

minerals such as epidote, biotite, amphibole, apatite, sphene and 

chlorite. With gradual increase in quartz and K-feldspar content the 

granodiorite grades into granite also at places especially towards 

north. The diorite rock found in the area exhibits considerable 

variation in composition from highly mafic to felsic. At places rock 

exhibits strong gneissosity due to alignment of felsic and mafic 

minerals and hence expediently named as granodiorite

26 



gneiss/diorite gneiss/granite gneiss. At certain places mafic bands 

are also showing distinct layering. The gneissosity trends between 

065°N-245°N and 060°N-240°N in general and occasionally 

swerves to 020°-030°N-200°-210°N and dips northerly or 

southerly at moderate to high angles. 

4.5 STRUCTURE AND TECTONICS 

The rocks of the area have been subjected to extensive jointing. A 

number of joints sets are present. The following four sets of joints 

are recorded: 

010 0 -050 0 /75 0 -85 0 (Foliation) 

160 0 -180 0 /40 0 -50 0 

170 0 N-350 0 N/vertical or 060 0 -80 o /75-85 0 Prominent 

080 0 N-260 0 N/vertical or 350 0 -020 0 /70 0 -80 0 

Out of these four joint sets, two sets are vertical and nearly 

orthogonal to each other trending nearly N-S and E-W, 

respectively. The joint set trending 170 0 N-350 0 N i.e. almost N-S is 

very prominent. These two sets may be termed as the conjugate 

joints. The other two joint sets have an oblique relationship with 

each other. A number of other randomly such as 220 0 -240 0 /35 0 - 

60 0 oriented joints are also noted which are generally not very 

persistent. 

A number of quartz and pegmatite veins ranging in thickness from 

less than 1m to more than 10m are also noted cutting across the

27 



granodiorite/diorite rock mass. The pegmatites are composed of 

quartz, feldspar and mica and are mainly of zoned variety. Zoning 

is determined by symmetrical arrangement of quartz-feldspar rich 

rim with quartz rich core. Large porphyroblast of brown mica are 

common in quartz-feldspar rich parts. 

4.6 GEOTECHNICAL APPRAISAL OF THE PROJECT 

AREA 

The project envisages construction of 85m high concrete dam 

750m downstream of the confluence of Kanji rivulet with Mathun 

river near Maron village. The underground power house site is 

proposed on right bank of Mathun River just upstream of the 

confluence of Igu Pani rivulet near Emini village. A preliminary 

geological plan is prepared based on existing geological 

information and limited field traverses and is enclosed as Plate 4.1. 

However, due to the inaccessibility of the terrain, it was not 

possible to undertake geophysical investigations of the project site. 

The geological details w.r.t. major project component is as follows. 

4.6.1 DAM SITE 

The river valley is nearly U-shaped at the dam site . The right bank 

is steeper than the left bank’s gentler slope. The river bed level 

at the proposed dam site is about 1200m. The rock 

outcrop of granodiorite / granodiorite gneiss is available on the 

right bank right from the river water level upto +EL 1240m 

and from EL +1355m to EL +1400m. This outcrop extends 

further upstream for about 250-300 m. However, a deep 

weathering effect is anticipated as per observation of rock 

exposed in this area. The right bank is in general covered

28 



with 0.5m (or even more at places) thick humus layer at the top and 

rock is expected at shallow depth. The left bank is covered with 

slopewash/riverine/glacial material. The riverbed is filled with 

riverine deposits. The thickness of slopewash material/RBM 

deposit estimated to be about 7-15m. The bedrock is 

granodiorite/granodiorite gneiss, which in general is strong but 

jointed. The rock mass has 4 joint sets. The main foliation joints in 

the dam area trend almost across the river dipping towards 

upstream at 75 0 -85 0 . The deep weathering of the rock mass is 

observed at places in the area with a thickness ranging from 2m to 

5m. However, the depth of weathering and thickness of overburden 

deposits need to be ascertained through drill holes/drifts in the dam 

area during detailed investigation. The tentative geological section 

along the proposed dam axis is given in Plate 4.2. 

4.6.2 WATER CONDUCTOR SYSTEM: 

Two 5km long head race tunnels (HRT) are proposed on right bank 

of Mathun River. Through the alignment of HRT, medium strong 

to strong granodiorite-granitic gneiss is expected. The rock is 

closely to moderately foliated, medium strong to strong rock with 

number of joint sets all along the HRT alignment with sufficient 

lateral and vertical cover. In general, foliation along tunnel is 

expected to be almost across or slightly oblique to the tunnel 

alignment. The main foliation joints shows low to medium 

persistence and are generally quartz filled. Several quartz and 

pegmatite veins showing both concordant and discordant 

relationship with the host rock are also expected to be encountered 

during the tunnel excavation. In general HRT is expected to

29 



encounter the fair tunneling media except where basic and ultra 

basic bodies are weathered and may be water charged. Several such 

shear seams/fracture zones ranging in thickness between 0.5 to 

more than 5m are expected to intersect the HRT alignment. Almost 

similar geological conditions are expected for other appurtenant 

structures such as desilting chamber, pressure shaft, tail race tunnel 

etc of the water conductor system. 

4.6.3 POWER HOUSE AREA 

The Power House Complex is proposed to be underground in 

granodiorite granite gneiss rock. The location lies at the corner of 

the junction point of Igu Pani rivulet with the Mathun river. The 

area is relatively flat with moderate to gentle slope and is under the 

cover of overburden material mainly consisting of silty-clay layer 

(2-5 m thick) and slope wash material consisting mainly of semi- 

consolidated mass having boulder, cobble & pebble size, set in 

silty/clayey matrix. Below the overburden cover, the bed rock is 

slightly to moderately weathered, medium strong to strong, 

granodiorite/granitic gneiss and is closely to moderately foliated. 

Rock outcrops of granodiorite/granite gneiss are, however, partially 

exposed at river level just upstream of confluence of Mathun & Dri 

Rivers on right bank. 

The rock in this area is expected to be moderately foliated, slightly 

weathered, medium strong to strong granodiorite/granodiorite 

gneiss. Rock is traversed by several shear zones ranging in 

thickness from less than one meter to more than 5m.

30 



Just north of the confluence of Mathun and Dri rivers a SW-NE 

trending fault has been recognized by Geological Survey of India. 

This trend of the fault is almost parallel to the alignment of Dri 

river for some extent, then onwards it turns towards NE direction. 

The proposed location of underground power house seems to be 

sufficiently away from the said fault. This fault is dipping north or 

south is yet to be identified and hence requires detailed study in 

further investigations as it may have a considerable bearing on the 

underground power house. 

4.7 RESERVOIR AREA 

A Reservoir covering an area of 166ha up to FRL of 1270m will 

come up as a result of construction of 85m high concrete dam near 

Maron village on Mathun River. The valley is comparatively 

narrow at the dam site. Steep rock slopes (60 0 -75 0 ) are present on 

right bank. However, on left bank rock is available at higher 

elevation. The occurrences of several slides especially along steep 

slopes of adjoining nallahs and rivulets are noteworthy which will 

require further study during detailed study of the project. In general 

granodiorite/granitic gneiss rock is present in the reservoir area. In 

general reservoir falls within granodiorite/granodiorite gneiss bed 

rock and expected to render reservoir tightness. Nevertheless, no 

mining activity is reported in the area and no mineral of economic 

importance is found in the vicinity of the project area. Further 

confirmation in this respect will have to be obtained from the 

Directorate of Geology & Mining and Geological Survey of India.

4.8 SEISMOTECTONICS AND SEISMICITY 

31 



The area falls in seismic Zone–V as per Map of India showing 

seismic zoning (IS-1893 (Part I): 2002). The important structural 

elements of the area are Lohit Thrust, Tidding suture with 

dismembered ultramafic suite (which mark the boundary between 

low grade sediments of Himalayan Oroganic belt and moderately 

reworked metasedimentary belt) and Mishmi Thrust. These thrust 

systems trend NW-SE in contrast to NE-SE trend of Naga Fold 

Thrust Belt. Other important tectonic elements in the area are NW- 

SE trending fault system restricted to the Tibetan Domain Pochu 

Fault, which are active, and seismotectonic. Most of these faults 

have right lateral sense of movement. The Naga–Arakan–Yoma 

Arc another important tectonic feature is also located south of the 

area which is highly seismic. 

The magnitude class distribution pattern of earthquake events 

reveals preponderance of 4.0-4.9 magnitude events. Important 

earthquakes around the area include the Assam earthquake of 15 th 

August 1950 (Mb=8.0,Ms=8.6). The suitable seismic design 

parameter needs to got worked out while firming up the detailed 

design of the project components keeping in view the 

seismotectonic set up of the area and high incidence of seismicity 

in this and adjoining areas, 

4.9 CONSTRUCTION MATERIAL 

The river valley being narrow there are very few river shoal 

deposits present in the area which can be the source of construction

32 



material. Therefore major part of the construction material 

requirement have to be met through rock quarries which appears 

possible in the near by surrounding areas of the project. 

4.10 CONCLUSION 

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

is mostly inaccessible. Hence, the following aspects need to be 

taken up during the feasibility studies. 

• General geological study of the area is required to be carried 

out in detail, since during the present course of studies most 

of the area was inaccessible and it could not be completed. 

Also, detailed geological mapping of the project components 

needs to be taken up besides carrying out subsurface 

investigations involving drilling/drifting to ascertain bed 

rock depth & its characteristics. 

• Availability of suitable construction material is required to 

be studied in detail. 

• The economic mineral deposits if any falls within the project 

area especially within the reservoir of the project will have 

to be affirmed from the Directorate of Geology & Mining 

and Geological Survey of India during detailed study. 

• The suitable seismic design parameter needs to get worked 

out while firming up the detailed design of the project.

5.1 GENERAL 

CHAPTER – V 

HYDROLOGY 

33 



Emini H.E.Project is a run of the river scheme, proposed on river 

Mathun, a tributary of Dibang River, opposite of Maron Village, 

d/s of confluence of Kanji rivulet with Mathun River. The project 

envisages construction of 85 m high dam above deepest foundation 

level on Mathun River with a gross storage capacity of 46.56 

M.cum at EL 1270 m. The submergence area at FRL is estimated 

as 166 Ha whereas the reservoir length is measured as around 7.1 

km. 

The hydrological investigations and analysis have been carried out 

with a view to: 

• Assess the availability of water for power generation by 

establishing a long-term series of average 10-daily 

discharges at the project site. 

• Estimate the spillway design flood. 

• Determine the capacity of the reservoir and the area of 

submergence at different levels including FRL and MDDL. 

5.2 RIVER SYSTEM & BASIN CHARACTERISTICS 

The Mathun River, also known as Adzon River, is one of the major 

tributary of Dibang River. It originates at an altitude of around

34 



5355 m. total length of river is around 80 km up to confluence 

with Dri River. Enzon River, Yangyap Chu, Chunbun N, Dini Pani, 

Ema N, Agu Nala, Indo Pani, Ipul Nala, Kanji, Imu, Andra, Chalu 

N are some of the important tributaries of Mathun river. The river 

forms the northern most drainage of Dibang river system. 

The river Dibang is one of the major tributaries of the Brahmaputra 

river system. The river cuts through deep gorges and difficult 

terrain in its upper reach through the great Himalayan range in 

Dibang valley district of Arunachal Pradesh and finally meets the 

river Lohit near Sadia in Assam. The total catchment area of 

Dibang up to its confluence with Lohit is 12,015 sq.km. The river 

has a total length of about 216 km from its origin to its confluence. 

The main tributaries in the upper reach of the river are - Emra, 

Tangon and Mathun. Small tributaries like Ahi, Epipani, Deopani, 

Ashupani, etc. meet the river in its lower reach. Dri and Mathun 

being almost equal in size, the catchments of the Dibang river is 

comparatively wider in its upper reach. 

The said project is in highly mountainous terrain where NE-SW 

trending Himalayan ranges meets with the Arakan Yoma range in 

this part of Arunachal Pradesh marked by highly dissected 

topography having precipitous hills and deep comparatively narrow 

valleys. In isolated portion open valleys and wide terraces are also 

noteworthy.

5.2.1 CATCHMENT AREA 

35 



The Emini basin lies between Longitude 95 o 30′ E to 96 o 10′E and 

Latitude 28 o 45’ N to 29 o 30’ N. The catchment area up to the 

proposed dam site is about 2600 sq.km. The proposed dam site lies 

at Longitude 95 o 52′16’’ E and Latitude 28 o 49′52’’ N. Equivalent 

slope of river near proposed dam site is estimated as around 1:60. 

Survey of India toposheets covering catchment area of Emini 

H.E.Project are not available, therefore, the catchment plan has 

been prepared on the basis of Survey Of India, State map of 

Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, 

Nagaland and Tripura of scale 1:1,000,000. CEA has identified 10 

hydroelectric projects in Debang basin for preparation of pre- 

feasibility report. These projects are marked in the catchment plan 

of Debang basin as shown in Plate-5.1. The catchment plan of 

Emini basin is given in Plate-5.2. 

Further, due to non-availability of toposheets, it is not possible to 

estimate permanent snow cover. This snow cover has been 

estimated as 609 sq.km in Dibang basin, which is only 5.06% of 

total catchment area 12015 sq.km). Mathun river, being a tributary 

of Dibang River, will have very little possibility of significant 

snow cover, therefore, in the present study, rainfed area has been 

considered as equal to total catchment area.

36 



5.2.2 TEMPERATURE AND HUMIDITY 

The Dibang basin falls partly in climatic zone partly in Zone III 

and I. Zone I comprises of North and North Eastern part of India 

including Myanmar, Nepal, Bhutan, Bangladesh and part of 

Pakistan. Zone No.III comprises of China, Tibet and some part of 

North and North Eastern part of Arunachal Pradesh. Climate in 

Zone No.I is generally tropical monsoon climate. Rainfall 

generally occurs during May to October while the months of 

November to February are generally dry periods. The climatic 

Zone No.III can be classified as “Mountain Climate” because of 

atmospheric transparency isolation as mountains are stronger and 

richer in ultraviolet radiation than that at sea level. Mountain 

slopes exposed to the sun experience burning heat, while slopes in 

shadow may be quite cold. 

In general the temperature in the foothill region of the basin is very 

hot during summer with temperature rising up to 45°C and very 

cold in the places of high altitude with temperature dipping as low 

as 2°C. The meteorological observatory centre in the Dibang basin 

is located in Hunli and Elopa. Temperature and Relative humidity 

data are collected here since 1998. The monthly maximum and 

minimum temperature and humidity recorded since September’98 

to June’ 2000 are given in the Table 5.1 and 5.2 respectively. 

In addition to above, Maximum and Minimum temperature data is 

available at Anini near confluence of Mathun River with Dri River, 

for the period Dec 2000 to Aug 2003. The maximum temperature

37 



and minimum temperature observed at this station is 51°C and - 

3°C respectively. The monthly maximum and minimum 

temperature recorded since Jan 2001 to Aug 2003 are given in the 

Table 5.3 and 5.4 respectively. 

TABLE – 5.1 

OBSERVED TEMPERATURE AND HUMIDITY 

Month/Year Temperature 

Maximum 

( O C) 

DATA AT HUNLI 

Temperature 

Minimum 

( O C) 

Maximum 

Relative 

Humidity 

(%) 

Minimum 

Relative 

Humidity 

(%) 

September’98 26 10 92 81 

October 24 6 91 80 

November 19 4 90 76 

December 17 3 88 68 

January’99 16 2 88 66 

February 14 2 89 75 

March 18 7 89 75 

April 19 9 89 75 

May 25 12 91 89 

June 27 16 91 81 

July 30 17 92 74 

August 29 16 92 82 

September’99 27 11 91 61 

October 22 11 89 64 

November 16 8 88 52 

December 12 7 87 71 

January’2000 14 7 88 71 

February 19 8 89 49 

March 20 12 90 59 

April 33 14 92 34 

May 30 19 92 82 

June 31 18 92 78

TABLE – 5.2 

38 



OBSERVED TEMPERATURE AND HUMIDITY 

Month/Year Temperature 

Maximum 

( O C) 

DATA AT ELOPA 

Temperature 

Minimum 

( O C) 

Maximum 

Relative 

Humidity 

(%) 

Minimum 

Relative 

Humidity 

(%) 

June’98 92 76 

July 92 84 

August 92 92 

September 92 85 

October 93 83 

November 92 76 

December 92 65 

January’99 91 71 

February 30 19 92 41 

March 37 17 92 42 

April 32 17 91 44 

May 39 20 92 49 

June 39 22 92 52 

July 39 20 92 52 

August 37 22 92 70 

September’99 37 23 92 70 

October 36 20 92 61 

November 32 17 92 53 

December 28 13 89 19 

January’2000 26 13 91 20 

February 28 14 89 34 

March 35 16 85 51 

April 35 16 85 51 

May 37 21 92 53 

June 39 23 92 49 

July 31 18 92 48

TABLE – 5.3 

39 



MAXIMUM TEMPERATURE AT ANINI IN O C 

YEAR 2001 2002 2003 MAXIMUM 

JAN 16 16 18 18 

FEB 20 21 20 21 

MAR 21 25 23 25 

APR 26 28 22 28 

MAY 31 32 26 32 

JUN 32 34 40 40 

JUL 33 35 51 51 

AUG 37 33 32 37 

SEP 29 26 29 

OCT 27 25 27 

NOV 22 21 22 

DEC 18 18 

MAXIMUM 37 35 51 51 

TABLE – 5.4 

MINIMUM TEMPERATURE AT ANINI IN O C 

YEAR 2001 2002 2003 MINIMUM 

JAN -2 -3 0 -3 

FEB -1 -2 -1 -2 

MAR 6 2 3 2 

APR 7 7 9 7 

MAY 11 10 10 10 

JUN 9 16 14 9 

JUL 17 15 14 14 

AUG 10 16 18 10 

SEP 18 12 12 

OCT 10 6 6 

NOV 5 1 1 

DEC 0 0 

MINIMUM -2 -3 -1 -3

40 



5.2.3 PRECIPITATION CHARACTERISTICS 

There are 19 nos. of raingauge stations reported in the entire 

Dibang basin, out of which only 1 station has Self Recording 

Raingauge in addition to the Ordinary type. The Brahmaputra 

Boad maintains all R.G. stations. Although a few stations have 

data w.e.f. 1985-86, most of the stations have data only from 1997 

onwards. The reported status of raingauge data is given in the 

Table-5.5. 

Sl. 

No. 

TABLE – 5.5 

STATUS OF RAIN GAUGE DATA IN DIBANG BASIN 

Name of Data Availability 

Station From To 

1 Ahralin 6/98 2/01 

2 Jia Gaon 8/85 8/02 

3 Elopa 6/97 8/02 

4 Ipingu 4/98 2/01 

5 Anelih 8/97 8/02 

6 Dunli 9/97 8/02 

7 Mipiden 4/98 7/01 

8 Kronli 10/85 12/85 

9 Amarpur 11/85 9/87 

10 Anini 2/92 6/95 &1/00 to 6/02 

11 Angolin 9/85 4/86 

12 Tangon 2/86 4/86 

13 Epipani 10/85 2/91 & 94 to 96 

14 Chepakhowa 9/85 11/87 & 1/89 to 

7/96 

15 Etalin 8/97 7/01 

16 Roing 4/84 8/02 

17 Hunli 7/99 7/00 

18 Christian basti 6/98 7/99 

19 Nizamghat 6/98 3/00 

1 Hunli (SRRG) 10/98 5/00

41 



The rainfall in the basin is mainly influenced by the mountain 

system and occurs due to the South-West monsoon, which sets in 

by the 2 nd week of May and continues upto the middle of October. 

Major portion of the rainfall occurs during the period from June to 

August. 

Two distinct climatic conditions prevail over the entire Dibang 

Catchment. The Upper reach starts from the Indo-Tibet border upto 

Mayudia Hill range and the lower reach starts from Mayudia Hill 

range to the Confluence with Lohit. In the Upper catchment, 

rainfall is comparatively less and the region is very cool during 

winter and comfortable during summer. The lower part maintains 

tropical climate. Rainfall is very high and climate remains very 

humid. 

The rain gauge network in Emini basin is not as per standards. 

Only one rain gauge stations namely Mipidon is available in Emini 

basin. The average annual rainfall in Emini basin is estimated as 

around 4023 mm. 

5.3 WATER AVAILABILITY STUDY 

Gauge and discharge data is not available anywhere in Mathun 

basin. Due to difficult condition of communication, accessibility 

and terrain, despite continuous efforts, much information about the 

discharge pattern in the Mathun basin could not be obtained. In the 

absence of much data and information, the following methodology

42 



may be adopted to obtain water availability series at proposed dam 

site: 

1. First option is to develop a rainfall-runoff relationship for the 

basin. However, discharge data is not available in the Emini 

Basin, even for small concurrent period. Therefore, a rainfall 

runoff relationship established at Elopa by CWC for Dibang 

basin on the basis of rainfall data at 6 stations namely Dunli, 

Mipidon, Anelih, Elopa, Italin & Ipingo and observed 

discharges at Elopa for the period 1998-2001, for monsoon 

as well as non-monsoon period may be taken. The average 

monthly rainfall based on above 6 stations is placed as 

Table-5.6. 

Daily rainfall data at Mipidon is available for the period 

1998-2001. This rainfall data may be used to compute 

discharge in Emini basin using the rainfall-runoff 

relationship established at Elopa in Dibang Basin. However, 

this methodology could not be adopted due to lack of 

continuity in rainfall data at Mipidon. Further only one 

station i.e Mipidon cannot be considered as representative of 

entire Emini basin.

TABLE – 5.6 

43 



AVERAGE MONTHLY RAINFALL IN DIBANG BASIN 

Month Dunli 

(98-01) 

Anelih 

(98-01) 

(MM) 1998 TO 2001 

Elopa 

(98-01) 

Italin 

(98-01) 

Mipidon 

(98-01) 

Ipingo 

(98-01) Average 

JAN 157.03 113.28 46.43 107.60 19.67 119.40 93.90 

FEB 164.25 161.10 78.53 243.13 183.40 179.93 168.39 

MAR 205.95 203.23 201.36 374.88 163.40 122.20 211.84 

APR 406.18 401.08 385.31 609.85 411.47 419.60 438.92 

MAY 489.98 434.03 633.46 479.96 363.53 447.60 474.76 

JUN 855.82 843.90 850.25 779.45 757.33 1535.33 937.01 

JUL 791.00 822.75 1014.99 806.85 764.65 901.40 850.27 

AUG 707.00 868.89 681.29 789.15 737.02 889.93 778.88 

SEP 311.11 372.81 556.10 437.75 294.20 337.54 384.92 

OCT 260.28 313.79 264.40 252.23 259.90 310.33 276.82 

NOV 64.53 57.31 30.13 64.98 54.80 56.80 54.76 

DEC 34.88 22.56 27.80 32.83 13.90 29.30 26.88 

TOTAL 4448.014614.73 4770.05 4978.66 4023.27 5349.36 4697.35 

2. Second option is to transfer generated discharge series for 

the period 1985-2001 at Munli dam site on the basis of 

catchment proportion considering the two catchments as 

hydro-meteorologically homogeneous. Average annual yield 

for this assumption is worked out as 9199 Mcum, 

However as also mentioned previously that the rainfall in 

upper catchment is comparatively less than the lower

44 



catchment. Effect of rainfall variation should also be taken 

into account. Therefore in addition to catchment correction, 

a reduction factor of the order of 10-15% is thought off. A 

ratio of average rainfall in Emini Basin and Munli basin 

obtained to account for the same is shown in Table-5.7 

MONTH 

TABLE – 5.7 

RAINFALL CORRECTION FACTOR 

Average 

Rainfall In 

Emini Basin i.e 

Mipidon (mm) 

Average 

Rainfall In 

Munli 

Basin (mm) 

Rainfall 

Correction 

Factor 

JAN 19.7 93.90 0.21 

FEB 183.4 168.39 1.09 

MAR 163.4 211.84 0.77 

APR 411.5 438.92 0.94 

MAY 363.5 474.76 0.77 

JUN 757.3 937.01 0.81 

JUL 764.7 850.27 0.90 

AUG 737.0 778.88 0.95 

SEP 294.2 384.92 0.76 

OCT 259.9 276.82 0.94 

NOV 54.8 54.76 1.00 

DEC 13.9 26.88 0.52 

Applying this correction factor to the series obtained on catchment 

proportion based on monthly basis gives average annual yield 7862 

Mcum. The ratio of average annual yield with or without rainfall 

effect works out as 85.4%, which justifies previous assumption

45 



(reduction of 10-15%). As previously mentioned that Mipidon 

alone cannot be taken as representative of rainfall in entire 

catchment, therefore an overall reduction of 15% (almost equal to 

ratio of average annual yield with or without rainfall effect) may be 

applied to the discharge series obtained after considering catchment 

effect only. 

The average 10 daily flow series, so computed at proposed dam site 

has been placed as Annexure-5.1 Average annual yield of Emini 

Basin at dam site of the proposed discharge series has been 

computed as 7819 Mcum. 

After establishing gauging station on Mathun River with proper 

raingauge network in Emini basin, detailed water availability study 

need be conducted in feasibility stage. 

5.4 RESERVOIR ELEVATION AREA CAPACITY 

CURVE 

The reservoir elevation-area-capacity curve at proposed dam site 

has been obtained on the basis of 1:50000 toposheets at 40 m 

contour interval. Area under various contours at 40 m interval has 

been measured from the elevation of 1200 m to 1320 m. The 

volume between any two elevations is calculated using the conical 

formula : 

V = (A1+A2+A1A2)*H/3

Where 

V = The volume between two contours 

H = Contour interval 

A1 = Area at level of first contour 

A2 = Area at level of second contour 

46 



The incremental volumes thus obtained are added to obtain 

cumulative volume. The reservoir elevation-area-capacity curve at 

proposed dam site site is given in Plate 5.3. This curve is subjected 

to modification after availability of reservoir cross-sections or 

1:15000 scale contour maps for the reservoir area. 

3.4 DESIGN FLOOD 

Design Flood for a project can be estimated by following 

approaches: 

(i) Deterministic approach using Unit Hydrograph 

technique. 

(ii) Statistical approach using Flood frequency analysis 

(iii) Empirical methods 

(i) Deterministic Approach Using Unit Hydrograph 

Technique 

Due to non-availability of G&D data, short term rainfall, hourly 

gauges etc, design storm values in the proposed catchment, rating 

curves and observed flood hydrographs could not be obtained for 

computing the Unit Hydrograph and Design Flood hydrograph.

47 



(ii) Statistical Approach Using Flood Frequency Analysis 

Due to non-availability of long term, consistent G&D data near the 

proposed scheme, flood frequency analysis could not be performed 

at the project site. 

(iii) Empirical Methods 

The following empirical relationships have been used to estimate 

the design flood peak: 

• Dicken’s Formula 

Q = CA 3/4 

Where, 

C = Dickens constant with value between 11-14 for North- Indian 

Hilly catchment. A value of 14 has been adopted in present study. 

A = Catchment area in sq.km 

Therefore 

Q = 14 x 2600 ¾ 

= 5098 cumec 

• Kanwar Sain And Karpov's Regional Enveloping Curves 

For catchment area of 2600 sq.km, the peak flood is given as 

around 8000 cumec for northern and central Indian rivers in the 

above curve. 

• Fuller’s Formula 

Qmax = C.A 0.8 (1+0.8logT)*(1+2.66A -0.3 ) 

Where,

48 



C = constant varying between 0.026 to 2.77 (2 adopted) 

Qmax = Maximum 24-h flood with a frequency of T years in 

cumec 

A = Catchment Area in sq.km 

1000 year Flood 

Q1000 =2 * 2600 0.8 (1+0.8log(1000))*(1+2.66*2600 -0.3 ) 

= 4591 cumec 

• Ali Nawaz Jung Formula 

Q = C(0.386A) (0.925-1/14log0.386A) 

Where 

C = 49 to 60 (55 adopted) 

Q = 55* (0.386*2600) (0.925-1/14log(0.386*2600)) 

= 7469 cumec 

• Transferring design flood at Munli dam site of Dibang Basin on 

the basis of Dickens formula. Design flood of 22809 cumec 

estimated at Munli dam site has been transferred to Emini dam site 

by conversion factor of 0.344. The computed design flood is 7858 

cumec at proposed dam site. 

A comparative study of flood peak computed from various 

methods is placed as Table-5.8. For pre-feasibility stage study, a 

design flood of 7000 cumec has been recommended at proposed 

dam site.

S.No 

. 

TABLE- 5.8 

49 



FLOOD COMPUTED BY VARIOUS METHODS 

Method Flood Peak (cumec) 

1 Dickens Formula 5098 

2 Kanwar Sain And Karpov's 

Regional Enveloping Curves 

8000 

3 Fuller’s Formula 4591 

4 Ali Nawaz Jung Formula 7469 

5 Computation from Design 

Flood at Munli Dam Site on 

the basis of Dickens formula. 

7858 

On availability of more data/information, design flood need be 

estimated by deterministic approach using unit hydrograph 

technique and probabilistic approach using flood frequency 

analysis in feasibility stage. 

5.5 RESERVOIR SEDIMENTATION 

No suspended sediment observed data, either at dam site or at any 

other location on river Mathun is available. Under such 

circumstances, an attempt has been made for an approximate 

assessment based on sediment yield rate of some of the North bank 

tributaries, which are flowing through Arunachal Pradesh and 

where sediment rates were earlier worked out for designing

50 



respective projects. All these tributaries have nearly similar 

topographical, physiographical, geological and soil vegetation 

cover characteristics. The values worked out are as below 

(Including bed load) : 

(a) River Dihang at Passighat -0.055 ham/sq.km/year 

(b) River Ranganadi at -0.074 ham/sq.km/year 

Yazali Dam site 

(c) River Dibang at Munli -0.100 ham/sq.km/year 

dam site (adopted value) 

(d) River Subansiri At -0.057 ham/sq.km/year 

Chouldhowaghat 

Based on the above data and in absence of any observed data, a silt 

rate of 0.075 ham/sq.km/year may be adopted for river Mathun at 

the proposed dam site. 

Detailed reservoir sedimentation study need be done during 

feasibility stage with more observed data at the proposed site using 

a suitable method. 

5.6 RECOMMENDATIONS FOR FUTURE STUDIES 

The following are the improvements suggested for feasibility/DPR 

stage study: 

• Proper raingauge network along with Gauge-discharge-sediment 

observation sites on Mathun river need be established before taking 

up preparation of feasibility report /DPR.

51 



• After establishing gauge and discharge site on Mathun river 

with proper raingauge network in Emini sub-basin, detailed water 

availability study need be conducted in feasibility/DPR stage. 

• The reservoir elevation area capacity curve need be revised 

after availability of reservoir cross-sections or 1:25000 scale 

contour maps in feasibility/DPR stage study. 

• On availability of more data/information, design flood need 

be estimated by deterministic approach using unit hydrograph 

technique and probabilistic approach using flood frequency 

analysis in feasibility/DPR stage. 

• Detailed reservoir sedimentation study need be done during 

feasibility/DPR stage with observed data on Mathun River at the 

proposed dam site using a suitable method. 

• The observations of CWC along with reply of NHPC have been 

enclosed as Annexure-5.1 and 5.2 and need be referred during 

feasibility/DPR stage.

SPACE FOR TABLE 

52 



CHAPTER-VI 

53 



CONCEPTUAL LAYOUT AND PLANNING 

6.1 FINALISATION OF CONCEPTUAL LAYOUT 

6.1.1 CEA PROPOSAL 

Emini HE Project is a run of the river scheme. According to CEA:_ 

“The Adzon water can be utilised again for power generation by a 

run of river development by constructing a diversion structure of a 

small height on the river at a site where the level bed level is 

+1200m and by leading the waters to a power house through a 6.5 

km long channel,. The scheme would autilise a gross head of 115 

m and enable firm power potential of 39MW. With an optimum 

generating capacity of 295 MW the scheme would enable energy 

generation of 1160Gwh and 1333Gwh respectively in 90% and 

50% dependable years”.(Refer annexure – 6.1). 

6.1.1 NHPC PROPOSAL 

The proposed Emini HE Project site was inspected by NHPC 

officers. Based on the topographical input (SOI toposheet no. 82 

P/ 13 in 1 in 50,000 scale) and geological inputs as collected, the 

NHPC proposal is detailed as under: 

As per reassessment studies carried out in CEA (based on desk 

studies ) Emini H.E. Project envisaged construction of a diversion 

structure 6.5 km long channel , a power house with installed 

capacity of 295MW . NHPC has proposed alternative layout with 

4.5 km long head race tunnel instead of channel. NHPC may 

proceed further with preparation of PFR. 

Deleted: 6.1.1 

Deleted: ETALIN HYDRO 

ELECTRIC SCHEME (DRG. NO. 

HEPR-PS-BHM-876) 

Deleted: The Kurung-I and Kurung-II 

projects are amongst the new schemes 

identified by CEA in ranking study. As 

per CEA’s proposal details of the scheme 

are: 

Kurung – I HE Project 

Kurung Dam-I Hydroelectric Project 

envisaged construction of a 125m high 

storage dam across the Kurung river 

where river bed level is El 620 m and 

dam toe power house. As per CEA’s 

assessment, schemes would enable firm 

power of 78MW with optimum installed 

capacity of 200MW. Further schemes 

would give benefits of annual energy 

generation of 1020 GWh and 749 GWh 

respectively in 50% and 90% dependable 

year. 

Kurung – II HE Project 

Kurung-II Hydroelectric Project 

envisages a diversion dam/weir across tail 

race of Kurung – I powerhouse, 9km long 

open channel and power house with tail 

race level as El + 560 m. As per CEA’s 

assessment, schemes would enable firm 

power of 45 MW with optimum installed 

capacity of 115MW . Further schemes 

would give benefits of annual energy 

generation of 581 GWh and 427 GWh 

respectively in 50% and 90% dependable 

year (Refer annexure – 2.1).

54 



NHPC’s Officers were requested to make every effort to get 

toposheets as well as data required from concerned authorities to 

establish hydrology at above project sites. The hydrological aspects 

of the project would need to be finalised by NHPC on priority for 

assessment of power benefits and finalisation of the project 

parameters/features. CEA would also render all possible help in 

this regard. NHPC Officers also requested for site visit by a 

multidisciplinary team. The same would be finalised after 

discussion with CWC, GSI etc./development of design 

parameters/features. 

During discussions with CEA / CWC, the NHPC proposal was 

found to be in order and NHPC was advised to proceed with 

preparation of PFR. (Refer Annexure – 6.2) 

ALTERNATIVE STUDIES 

It may be mentioned that during survey undertaken by project , it 

was observed that river bed level at proposed tail race outlet is EL 

118.0 m and not EL 1085.0m as indicated during discussion with 

CEA/CWC . The same has been incorporated in the PFR. 

Alternative studies were undertaken for selecting type of structures 

particularly in case of water conductor system and accordingly site 

was visited by NHPC Officers. It was observed that as per 

topography and geology of the area , provision of tunnel appears to 

be better alternative than open channel . 

Deleted: 

 

Deleted: INTRODUCTION 

Deleted: Layout

55 



Based on the topographical details (toposheets no 83 P/14, 1: 

50,000 scale) & geological details project layout has been 

developed. . Various components of the project are: 

a) River diversion works comprising of a 12 m diameter 

horseshoe shaped diversion tunnel with u/s and d/s 

cofferdams. 

b) 85 m high concrete gravity dam from deepest foundation 

level. 

c) Water conductor system consisting of 

i) 2 nos Intake structure 

ii) 4 nos 350m(L) X 18m(W) X 25m (H) Desilting chamber 

iii) 2 nos 8.0 m diameter horseshoe shaped headrace tunnel. 

iv) 2 nos 25 m diameter surge shaft 

v) 2 nos 7.0 m diameter pressure shaft each to feed 2 units 

vi) 2 nos 8.0 m diameter horseshoe shaped tailrace tunnel. 

d) An underground power house consists of 

i) 120m(L) X 24 m (W) X45 m (H) powerhouse cavern 

ii) 100 m(L)X 20 m(W) X 25 m(H) transformer cum Draft Tube 

gates cavern 

e) Pothead yard 25 m x 60 m 

Proposed General layout plan and longitudinal section through 

water conductor system are enclosed as Plate-6.1 & Plate-6.2 

respectively. 

Deleted: & 

Deleted: G 

Deleted: geological 

Deleted: E/9 

Deleted: Kurung 

Deleted: Etalin HE Project envisages 

construction of 

Deleted: a 

Deleted: 2 nos of concrete gravity dam 

4 nos of HRT, 4 nos of HRT, 4 nos of 

surge shaft and 

Deleted: a 

Deleted: 2 nos of underground power 

Deleted: station 

Deleted: house 2500 mw (10 nos X 

250MW ) &1500 MW (6 nos X 250 MW 

) 

Deleted: of 330 MW having 3 units of 

110 MW each 

Deleted: 1 9 

Deleted: 140 

Formatted: Bullets and Numbering 

Deleted: 8.5 

Deleted: 7 

Deleted: three 

Deleted: 8.5 

Deleted: 24 

Deleted: 15 

Deleted: 25 

Deleted: 60 

Deleted: 1 

Deleted: 2 

Deleted: 2

6.2. PRELIMINARY DESIGN FEATURES 

6.2.1 RIVER DIVERSION WORKS 

56 



6.2.1.1 DIVERSION TUNNEL 

For the construction of concrete gravity dam and appurtenant 

works, the river diversion is proposed to be carried out through a 

12 m diameter concrete lined, horseshoe shaped diversion tunnel 

located on the left bank of the river. As no G&D data is available 

over river Mathun / Dri, the diversion tunnel has been designed for 

passing a assumed diversion discharge of 1600 cumec based on 

experience gained by NHPC in their projects. However during 

FR/DPR stage this needs to be firmed up. The length of diversion 

tunnel shall be about 700 m. 

6.2.2 COFFER DAM 

To facilitate river diversion, upstream and downstream cofferdams 

with a central impervious core shall be provided. These coffer 

dams shall be located about 100 m u/s and 250 m d/s of the 

proposed dam axis. The height of u/s and d/s cofferdams shall be 

25 m and 12 m respectively. As the diversion scheme has been 

designed to cater for non-monsoon flood, cofferdams may get 

damaged during monsoon period and as such, shall require 

rebuilding before undertaking works in subsequent working 

season. 

6.2.2 DAM 

6.2.2.1 DAM LOCATION 

Based on the site inspection by NHPC team, the dam axis has been 

proposed to be located downstream of confluence of Kanji pani 

with the river Mathun having river bed level as El. 1200 m.

57 



6.2.2.2 TYPE OF DAM 

The IS code stipulates consideration of 1 in 100 year monsoon 

flood for diversion in case of a embankment dam and 1 in 25 years 

non-monsoon flood for concrete dam. Further for effective 

reservoir flushing, requirement of low-level spillway necessitate 

provisions of concrete dam. 

In view of above pre-feasibility of the project has been examined 

with concrete gravity dam. However it may be mentioned that 

based on the topographical and geological data collected during 

feasibility stage, if required, type of the dam and its height shall be 

reviewed. 

6.2.2.3 FIXATION OF FULL RESERVOIR LEVEL 

(FRL) AND MDDL 

The bed level of tail race outfall of proposed Amulin H.E. 

Project located upstream is EL ±1280 , keeping the difference of 

about 10 m between tailrace outfall bed level of upstream project 

& FRL , the FRL for Emini H.E. Project has been proposed as EL 

1270 m. Needless to mention that during FR/DPR stage 

considering the finally adopted parameters of Amulin H.E. Project, 

FRL of Emini H.E. Project shall need to be optimized to minimize 

loss of head . MDDL has been fixed at El 1260 m considering 

proposed power intake level and on power potential studies. 

6.2.2.3 DAM ARRANGEMENT 

The dam has been divided in non-overflow blocks and overflow/ 

spillway blocks. The central 7 blocks shall be overflow / spillway 

Deleted: In the ranking study report, 

FRL of EL 745.0 M has been proposed. 

In order to avoid submergence of 

Koloriang Town located about 35 km 

upstream of the propose 

Deleted: u/s project 

Deleted: 

Deleted: the 

Deleted: TRL 

Deleted: 

Deleted: of preceding project 

Deleted: 7 

Deleted: 10 

Deleted: retained 

Deleted: 710 

Deleted: 

Deleted: 710

58 



blocks of 15 m width each, flanked by non-overflow blocks of 14 

m width on either side. 

SPILLWAY 

Spillway for concrete dam is proposed to be designed for a 

probable maximum flood (PMF) of 7000 cumec. Design discharge 

is proposed to be passed partly through low level and rest through 

upper level spillway. Provision for upper level spillway shall also 

facilitate in reservoir operation / regulation. Five nos. of lower 

level orifice type spillway (inclusive of 1 bay as emergency) is 

proposed with crest at EL 1230 m and spillway opening size 7.0 m 

x 10.0 m. In addition two nos. of Upper level spillways one on 

either side of lower spillway with crest at El 1260 m and opening 

of 7.0 m X 10.0 m have been proposed. Total length of spillway 

structure is 105 m. 

NON-OVERFLOW BLOCKS 

The non-overflow blocks have been provided with downstream 

slope of 1.1 H: 1V. An upstream slope of 1H: 4V has been 

provided below the level of El 1250 m. 

Proposed layout of dam area, upstream elevation & cross sections 

of dam are enclosed as Plate- 6.3, Plate- 6.4 and Plate- 6.5. 

6.2.2.4 ENERGY DISSIPATION ARRANGEMENT 

A ski-jump type energy dissipation arrangement has been provided 

downstream of spillway with flip bucket having lip angle of 30 0 . A 

preformed plunge pool of size 90 m (L) x 105 m (B) has been 

provided.

6.2.3 WATER CONDUCTOR SYSTEM 

59 



6.2.3.1 HEAD RACE TUNNEL INTAKE 

The water is led to headrace tunnel through two number intake 

structure with invert at El. 1240 m. The invert has been kept 10 m 

above the lower spillway crest to minimize silt entry in water 

conductor system. Intake shall be provided with gate opening of 

7.9 m x 9.0 m for each HRT. 

An inclined type trash rack structure is proposed at the entrance of 

the intake structure with single trash rack-cleaning machine and as 

such two intake structure shall be combined and aligned 

accordingly. 

6.2.3.2 DESILTING CHAMBER 

In order to remove particle having size more than 0.2 mm, desilting 

chamber in each HRT has been proposed. Each HRT shall have 

two Desilting chambers each of size 350 m (L) X 18 m (W) X 25 

m (H). A 9 m dia intake tunnel about 500 m long has been 

proposed between HRT intake and desilting chamber. The intake 

tunnel bifurcates into two 6.4 m dia feeder tunnel feeding each 

desilting chamber. Tunnel of size 5.7 m dia has been provided 

after each desilting chamber subsequently combining to 8 m dia 

HRT . 

For flushing out of accumulated silt, each desilting chamber has 

been provided with silt flushing tunnel of size 3.0 mn(W)X2.0m

60 



(H) . Each silt flushing tunnel combines to one SFT of size 3.75 m 

dia. 

6.2.3.3 HEAD RACE TUNNEL 

Two nos. 8 m diameter horseshoe shaped headrace tunnel have 

been proposed on the right bank of the river. The length of each of 

the tunnel shall be about 5Km. 3 nos of 6.5 m (D shaped) 

intermediate adit about 400 m in length (average) have been 

proposed to facilitate construction of the HRT. 

Rock bolts, shotcrete with wire mesh has been proposed as tunnel 

support system. Provision of steel rib support has also been kept to 

take care of poor rock strata wherever encountered. The tunnel 

shall be 600 mm thick concrete lined. 

6.2.3.4 SURGE SHAFT 

Keeping in view the long HRT, a 25 m diameter concrete lined and 

about 75 m high circular restricted orifice type surge shaft with 

gate has been proposed for each HRT. 

Rock bolts, shotcrete with wire mesh has been proposed as shaft 

support system. Surge Shaft shall be concrete lined (1000 mm 

thick). 

6.2.3.5 PRESSURE SHAFT 

From the downstream of each Surge Shaft, 7 m diameter steel lined 

pressure shaft with 115 m vertical drop has been proposed. In 

Deleted: 600 

Deleted: No observed sedimentation 

data is available at the Kurung dam site. 

In F 

Deleted: f 

Deleted: easibility stage, sedimentation 

study is proposed to be carried out. Based 

upon the study, suitable Desilting 

arrangement shall be provided, if 

required.

61 



pressure shaft, a 50 m horizontal portion at top and 125 m 

horizontal portion at bottom has been proposed. The centreline 

elevation of lower horizontal portion has been kept at El 1113 m 

i.e. centre line of turbine. The two pressure shafts, after horizontal 

portion at bottom, bifurcates into four penstocks suitably connected 

to main inlet valves to feed each unit of powerhouse. 

6.2.3.6 DRAFT TUBE AND TAIL RACE TUNNEL 

The water from turbine shall be discharged back to river through 

draft tubes and tailrace tunnels. The overall size of a draft tube 

opening shall be 11 m x 5 m with one 2 m wide intermediate pier. 

After the draft tube gates, opening shall be combined and thus 

discharge from two units shall be led to one horseshoe shaped 

concrete lined tail race tunnel of 8 m. Both TRT shall be about 250 

m long with suitable outlet arrangement. 

Rock bolts, shotcrete with wire mesh has been proposed as tunnel 

support system. Provision of steel rib support has also been kept to 

take care of poor rock strata wherever encountered. The tunnel 

shall be 600 mm thick concrete lined. 

Proposed cross sections of water conductor system are enclosed as 

Plate-6.6 . 

6.2.4 POWER HOUSE COMPLEX 

Based on topography and geological consideration (locating power 

house from fault as projected by geologist) underground 

powerhouse has been proposed. It may be mentioned that the 

location and orientation of power house shown in PFR is indicative 

Deleted: 2 

Deleted: 2

62 



only and shall need to be finalized during FR/ DPR stage based on 

collected detailed topography and geological data. 

6.2.4.1 POWER HOUSE CAVERN 

An underground powerhouse cavern has been proposed to house 

four units of 125 MW each with turbine centerline level at EL 1113 

m. The size of powerhouse cavern will be 24 m (W) x 120 m (L) x 

45 m (H). Four bus shafts, one for each unit, of 6 m x 6 m shall be 

provided connecting the powerhouse cavern to transformer cavern. 

Further, 8 m x 8 m D-shaped gallery is also proposed between 

powerhouse cavern to transformer cavern to facilitate toeing of 

transformers between service bay and transformer cavern. 

Rock bolts, shotcrete with wire mesh has been provided to support 

the roof arch and the wall of the cavern. 600 mm thick concrete 

lining in roof arch and 300 mm in wall , has been provided. 

MIV is proposed to be housed within powerhouse cavern. 

6.2.4.2 TRANSFORMER CUM DRAFT TUBE GATE 

CAVERN 

Transformer cavern been proposed on downstream of PH cavern to 

house the transformers. The size of cavern is proposed to be 20 m 

(W) x 100 m (L) x 25 m (H). Transformer cavern shall facilitate 

housing of (a) GIS and (b) draft tube gate hoisting arrangements.

63 



Rock bolts, shotcrete with wire mesh has been provided to support 

the roof arch and the wall of the cavern. In addition, 500 mm thick 

concrete lining in roof arch has been provided. 

Cable cum ventilation tunnel is proposed to connect the 

transformer cum Draft Tube gate cavern to pothead yard. The size 

of tunnel shall be 8 m D-shaped. 

Proposed layout of power house area and its cross section of its 

component are enclosed as Plate-6.7 & Plate-6.8respectively 

6.2.5 POTHEAD YARD 

Pothead yard is proposed on right bank. The size of pothead yard 

will be 25 m (W) x 60 m (L). 

6.2.6 HYDRO MECHANICAL EQUIPMENT 

Following hydro-mechanical equipments have been envisaged for 

Emini HE Project: - 

6.2.6.1 DIVERSION TUNNEL GATES AND HOISTS: 

For the diversion of water during construction stage it is proposed 

to provide one number horseshoe shaped diversion tunnels of 12.0 

m diameter. The diversion tunnel inlet is divided into two 

openings. After the construction of the dam, for the purpose of 

plugging the diversion tunnel, two numbers fixed wheel type gates 

of size 5.0 m x 12.0 m will be provided at inlet of tunnel. 

The gates shall be operated by means of electrically operated rope 

drum hoists of 150 T capacity. 

Deleted: 1 

Deleted: 2 

Deleted: 2

64 



6.2.6.2 UPPER SPILLWAY RADIAL GATES, HOISTS, 

STOPLOG AND GANTRY CRANE: 

The upper spillway consists of two bays of opening size 7.0 m x 

10.0 m with crest at EL 1260.0 m. Two radial gates for opening 

size of 7.0 m x 10.0 m shall be provided to control the discharge 

through the gated portion of the spillway. Each gate shall be 

operated by means of a hydraulic hoist consisting of two hydraulic 

cylinders of 45 T capacity each. The gate operation shall be done 

from a local control room as well as from remote control system 

located at the dam control room (DCR) with provision of gate 

position indication at Powerhouse. The operation from DCR shall 

be through a programmable computer based automatic reservoir 

measuring and control system located in the DCR. 

The inspection and maintenance of the radial gate shall be carried 

out by lowering one set of sliding type Stoplogs on the upstream 

side of these gates. The Stoplogs shall be operated under balanced 

head condition. It is proposed to operate the stoplogs by means of a 

common gantry crane of 130 T capacity provided for lower 

spillway on the top of the spillway deck 

The stoplog units will be stored in the storage vents provided in the 

dam area on both sides. 

One trolley mounted mobile gasoline engine powered power pack 

capable of operating one gate at 1/4th of the normal rated speed is 

also envisaged.

65 



6.2.6.3 LOWER SPILLWAY ORIFICE RADIAL 

GATES, HOISTS, BULKHEAD AND GANTRY CRANE: 

The lower spillway consists of five orifice type bays of opening 

size 7.0 m x 10.0 m with crest at EL 1230.0 m. Five submerged 

type radial gates for opening size of 7.0 m x 10.0 m shall be 

provided for reservoir flushing and to pass the design flood 

discharge through the gated portion of the spillway. Each gate shall 

be operated by means of means of a hydraulic hoist consisting of 

two hydraulic cylinders of 135 T capacity each. The gate operation 

shall be done from a local control room as well as from remote 

control system located at the dam control room (DCR) with 

provision of gate position indication at Powerhouse. The operation 

from DCR shall be through a programmable computer based 

automatic reservoir measuring and control system located in the 

DCR. 

The inspection and maintenance of the radial gate shall be carried 

out by lowering a bulkhead gate on the upstream side of these 

gates. One number wheeled type bulkhead gate has been 

envisaged to cater to the maintenance requirement of 5 nos. 

spillway radial gates. Steel Liner shall be provided in the water 

passage at the bulkhead gate grooves. The gate shall have upstream 

skin plate and downstream sealing. It is proposed to operate the 

bulkhead gate by means of a gantry crane of 130 T capacity with 

the help of a lifting beam. A separate storage vent shall be provided 

in the non-overflow section at the deck level for storing the 

bulkhead gate when not in use.

66 



On the underside of breast wall provision has been kept for high 

strength steel liner. 

One trolley mounted mobile gasoline engine powered power pack 

capable of operating one gate at 1/4th of the normal rated speed is 

also envisaged. 

6.2.6.4 POWER TUNNEL INTAKE GATE WITH HOIST, 

TRASH RACK AND RAKING MACHINE: 

A fixed wheel type gate for opening size 7.9 m x 9.0 m shall be 

provided just downstream of the each intake bell mouth. The sill of 

the gate is located at EL 1240.0 m. The gate shall be operated by 

means of dedicated electrically operated rope drum hoists of 145 T 

capacity located on the hoist platform installed over trestles. 

On upstream of the Intake an inclined trash rack (15° with 

vertical), shall be provided 

The cleaning of the trash rack shall be done by means of a trash- 

raking machine. 

6.2.6.5 DESILTING BASIN GATES: 

One number fixed wheel type gate for opening size of 6.4m X 6.4 

m is provided at the inlet of each desilting chamber. Each gate shall 

be operated by means of a dedicated rope drum hoist of 45 T 

capacity. 

To isolate the desilting basin for maintenance and inspection two 

sets of bulkhead gate for opening size 6.4m X 6.4 m has been 

proposed at the inlet and 5.7m X 5.7 m has been proposed at the 

outlet to isolate two basins at a time. The bulkhead gate shall be

67 



operated by means of EOT crane of 35 T capacity and lifting beam 

under balance head condition. 

6.2.6.6 FLUSHING TUNNEL GATES, HYDRAULIC 

HOISTS: 

Four set of flushing tunnel sliding type gates, one set for each 

flushing tunnel, comprising of one service gate (d/s) and one 

emergency gate (u/s) having a clear opening of 3.0 m x 2.0 m have 

been proposed. Bonnets and bonnet covers for both the gate 

grooves and hoist supporting structures for both the gates are 

required to be provided. 

Each gate shall be operated by means of an independent double 

acting hydraulic hoist of capacity 215 T. 

6.2.6.7 SURGE SHAFT GATE 

For isolating the pressure shaft a slide type gate is provided at the 

inlet of each pressure shaft. The gates shall be operated by means 

of electrically operated rope drum hoists of 120 T capacity. 

6.2.6.8 DRAFT TUBE GATE: 

The draft tube emerging out from each generating unit gets divided 

into two bays. Each bay is provided with one wheeled type gate of 

suitable size for the above opening to isolate the generating units 

from tail water. The gate will have an upstream sealing (pressure / 

tailrace side) and upstream skin plate. 

Each gate shall be operated by means of dedicated rope drum hoist 

of 35 T capacity.

6.2.6.9 TAIL RACE OUTLET STOPLOGS: 

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For the inspection and maintenance of the tailrace tunnels, one set 

of stoplog has been envisaged at outlet structure. The stoplog shall 

be designed for a head of corresponding to maximum Tail water 

level and operated under balanced head conditions. These stoplog 

shall be operated by means of a mobile crane. 

6.2.6.10 PRESSURE SHAFT LINER: 

Two no. Pressure Shaft of dia. 7000 mm fully steel lined will take 

off from d/s of concrete transition of surge shaft gate to feed the 

turbine placed in the powerhouse. It comprises horizontal & 

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

bifurcation and branch pipes for each pressure shaft to feed four 

turbines. 

The material of Pressure Shaft liner shall conform to ASTM A537 

Class 1. However bifurcation material shall conform to ASTM 

A517 Gr. F 

6.2.6.11 MISCELLANEOUS: 

6.2.6.11.1 RESERVOIR MEASURING AND REMOTE 

CONTROL SYSTEM 

One complete set of remote control system for the remote control 

operation of spillway gates, along with programmable 

computerized automatic reservoir monitoring control system is 

provided in the dam control room. The programmable reservoir 

monitoring and control system shall include all necessary

69 



instrumentation required for monitoring and control of reservoir 

including water level measuring systems, gate position indication 

transducers for spillway gates and intake gate discharge measuring 

devices. The indication of this system shall also be made available 

in the powerhouse. The communication system shall be through 

fiber optic cable. 

Provision shall be made for one no. filter unit to purify the 

hydraulic oil along with one unit contamination checking kit for 

checking of contamination level & one no. of low vacuum 

dehydration and degasification unit to remove water and gases 

from hydraulic oil. 

6.2.6.11.2 DIESEL GENERATING SET 

A three-phase synchronous type diesel generating set of 500 KVA, 

450 Volts, 50 Hz is envisaged for the emergency operations of the 

HM equipments at the dam site. The diesel generating set shall be 

located in the dam area and to provide back-up supply to gate 

operating equipments and to the computerized control system in 

case of power failure. 

6.3 FURTHER STUDIES REQUIRED 

Following are some of the studies required to be undertaken during 

the preparation of feasibility report / detailed project report: 

• Optimisation / finalisation of location of dam and its height 

based on topographical and geological inputs.

70 



• Optimisation / finalisation of layout of water conductor system 

based on topographical and geological inputs. 

• Optimisation / finalisation of location and orientation of 

powerhouse based on topographical and geological inputs 

• Evaluation of engineering properties of rock mass. 

• Transient analysis 

• Detailed design computation to fix size of various components 

of the project. 

• Integrated reservoir operation and power potential studies of 

Emini HE Project with other Dibang Basin projects. 

Comments of CMDD Directorate, CWC and para wise NHPC 

replies have been enclosed as Annexure 6.3.


CHAPTER - VII 

POWER POTENTIAL STUDIES 

71 



The Chapter contains the optimization of power potential of the 

project on the basis of the discharge data for the year June 1985 to 

May 2001 (16 Years). It is essentially a run-of-river with small 

pondage scheme. The installed capacity of Emini project has been 

proposed as 500 MW comprising of four units, each of 125 MW in 

the underground type power house. 

The salient features of the project are as follows: - 

Installed capacity = 500 MW 

No. & size of unit =4 units of 125MW 

Type of power house = underground type 

Net head = 125 meters 

Design discharge per unit = 110.80 cumec 

Type of switchyard = GIS 

Turbine type = Vertical Francis 

Speed of turbine = 214.3 rpm 

Generation voltage = 13.8 KV 

Transmission voltage = 400 KV 

GSU Transformer = 13 Nos., 47 MVA, 1-phase 

Energy generation in 90% 

dependable year with 95% = 1695.45 MU 

Machine availability

72 



7.2 AVAILABLE DATA 

The Power Potential studies have been carried out based on 

following data: - 

a) Discharge Data 

b) FRL, MDDL, TWL, Head losses and Area capacity curve. 

c) Due to non availability of evaporation loss, evaporation loss has 

not been accounted for in the power potential study. 

7.3 DISCHARGE DATA 

Inflow series of 16 years i.e.1985-1986 to 2000-2001 has been 

obtained and used for carrying out power potential and 

optimization studies. The 10-daily discharge data in cumecs for all 

16 years is shown in the enclosed Table-7.1. The criterion of 90% 

dependable flow is applied for conducting power potential studies 

and inflow of same is shown in Table-7.2. 

7.4 FIXATION OF FULL RESERVOIR LEVEL (FRL) 

As per the SOI toposheet no. 82 P/ 13 and site inspection, all 

villages/towns except village Maron are located above EL 1280 m. 

The lowest level of village Maron consisting of two houses, is EL 

1225.21 m. In view of above, FRL of EL 1270 m has been 

proposed with dam top at EL 1275 m. 

7.5 FIXATION OF MINIMUM DRAW DOWN LEVEL 

(MDDL) 

The choice of MDDL has mainly been based on firm power 

requirement, requirement of dead storage with regard to

73 



sedimentation, water cover to intake structure, minimum spillage 

and ensuring peaking support, the MDDL has been fixed at 

EL.1260.0 m. 

7.6 FIXATION OF TAIL WATER LEVEL (TWL) 

No observed G & D data over river Emini is available and as such 

no tail water rating curve could be developed. As per the survey 

details provided by the project, the river bed level at proposed TRT 

outlet is EL 1118 m. A water depth of 10 meters has been 

assumed to arrived at maximum Tail water level i.e. maximum 

TWL has been taken as EL 1128.0 m. 

7.7 OPERATING HEAD AND HEAD LOSSES 

Full Reservoir Level (FRL) and Minimum Draw Down Level 

(MDDL) are respectively at EL 1270.0 m and 1260.0m. while the 

maximum tail water level corresponding to 4 units running has 

been taken as 1128.0 m. Head losses in the water conductor system 

have been taken as 10% of the gross head. The net operating head 

for turbines has been calculated from the following formula, 

Net Operating Head: 

= MDDL + 2/3(FRL-MDDL) - Maximum Tail Water level – Head 

Losses 

Thus, by above-mentioned formula, net operating head works out 

to be 125.0 m. 

7.8 DEFINITION OF TERMS: - 

7.8.1 90% DEPENDABLE YEAR: 

This is the lower decile of the series of the corresponding monthly 

period of the record i.e. (N+1) x 0.90th year where N is the years

74 



for which hydrological data are available. 90% dependable year 

comes out as 1994-1995 as shown in the enclosed Table-7.3 

7.8.2 ANNUAL DESIGN ENERGY 

This is the yearly energy generation during the 90% dependable 

year 1994-1995 with 95% machine availability and after 

accounting the 20% release of discharge for silt flushing during 

month of May to September, which works out to be 1695.45 MU 

as shown in Table-7.4. It may be seen from Table-7.3 that the firm 

power is 100.04 MW corresponding load factor is 20.01%. 

Further it is also mentioned that the load factor during peak 

discharge i.e. March to Nov. and lean period i.e. Dec. to Feb. are 

43.68% and 23.50% respectively. 

7.8.3 INSTALLED CAPACITY 

The installed capacity of Power house has been selected based on 

the following considerations: - 

• Assessment of the energy generation with various 

installed capacities. 

• Maximum utilization of the available inflow. 

• Incremental value of energy generation with the 

increased installed capacity. 

• Annual Load factor. 

The power potential study has been carried out for different 

installed capacities ranging from 365 MW to 590 MW with an 

increment of 15 MW, as shown in Table-7.5. Based on the above-

75 



mentioned parameters, the installed capacity of the power plant has 

been selected as 500 MW. 

7.8.4 SIZE OF GENERATING UNITS 

The power load demand in India is increasing at a very rapid rate, 

and both hydro electric and thermal (including nuclear) power 

potential in the country are being developed not only to meet the 

overall requirements, but simultaneously also to provide a proper 

hydro and thermal power for optimum operation of the system. 

Keeping this in view current practice is to opt for largest size hydro 

units permissible within the parameters of economy, operating 

efficiency, maintenance, optimum utilization of available water, 

transport limitations etc. Based on above-mentioned parameters, 4 

No. Units of 125 MW each have been proposed for this project. 

7.8.5 ANNUAL ENERGY GENERATION 

The restricted energy generations in the 90% dependable year i.e. 

(1994-1995) are shown in the enclosed Table-7.4. It may be seen 

from this table, that the total energy generation in 90% dependable 

year with 95% machine availability restricted to an installed 

capacity of 500 MW and after accounting the 20% release of 

discharge for silt flushing during monsoon is 1695.45 MU.

SPACE FOR TABLE 

76 



77 



78 



79 



80 



81 



82 



83 



84 



85 



86 



87 



88 



89 



90 



91 



92 



93 



94 



95 



96 




CHAPTER - VIII 

POWER EVACUATION 

97 



The 500 MW Emini H.E. Project is envisaged for installation of 

four generating units of 125 MW, each operating under a rated net 

head of 125.0m housed in an underground powerhouse. The 

generation voltage is proposed to be 13.8 KV. This voltage will be 

stepped up to 400KV voltage level by Generator step-up 

transformers. HV side of the Generator step-up transformers will 

be further connected to 400 KV Gas Insulated Switchgear (GIS) 

located above the transformers, both housed in the underground 

cavern. Gas Insulated Switchgear will be connected to outdoor 

potyard through 400 KV XLPE cables. The power from Emini 

H.E. Project would be fed to the North-Eastern Grid to be 

ultimately connected to the National Grid through EHV/HVDC 

transmission lines. Provision of two outgoing bays has been kept in 

GIS for 500 MW power evacuation from this project. 

8.1 EXISTING POWER EVACUATION FACILITIES 

Power system network is controlled by the Electricity boards/ 

Departments/Corporations of the states of Assam, Meghalaya, 

Arunachal Pradesh, Nagaland, Manipur, Mizoram and Tripura. 

Power System Networks of PSUs located in the region are two 

400KV line going to Balipara from Dikrong (Ranga Nadi) power

98 



station and two 132KV line are also emanating from Dikrong 

Switchyard and feeding to Along and Nirjuli areas. 

8.2 PROPOSED EVACUATION ARRANGEMENT 

It is proposed to bring the power from Emini H.E. Project to 

Pooling substation being planned near Anini through 400KV 

double circuit transmission line. Accordingly, provision for two 

outgoing bays have been kept at Emini H.E. Project. Further, the 

power from Amulin H.E. Project will also be brought at 220KV 

level to Emini power house. This power would be stepped up to 

400KV level by providing stepup power transformer at Emini. 

Then, power from Emini at 400 KV voltage level will be pooled to 

Anini pooling station. Power from Mihundon & Agoline H.E. 

projects would also be pooled to Anini pooling point at 220KV 

voltage level. At Anini pooling point substation, there would be 

two voltage levels i.e 220 KV and 400KV. The power at 220 kV 

level would be stepped up to 400 KV level through step-up power 

transformer. Further, this power would be pooled to pooling point 

planned near Roing/Dambuk at 400 KV voltage level. For this, one 

D/C outgoing 400KV transmission line with “Quad Moose 

Conductor’’ is proposed. The power from the pooling point shall 

be ultimately connected to National Grid through EHVAC/HVDC 

transmission line. Further, the cost for transmission network of 

about 10Km distance from Emini power house to Anini pooling 

point substation and cost of other end equipment at Anini pooling 

substation have been considered. The space for 220/400 KV power

99 



transformer and 220KV GIS with two bays have been kept at 

Emini Power station. 

Single Line Diagram of switchyard of Emini HE Project 

and Power Evacuation System in Dibang Basin has been 

enclosed as Plate 8.1 and Plate 8.2 respectively.

CHAPTER -IX 

100 



ENVIRONMENTAL ASPECTS 

9.1. INTRODUCTION: 

The proposed Emini HE Project envisages construction of a dam 

on river Mathun near Maron village 9 km from Anini on the Anini- 

Roing road in Arunachal Pradesh.- the land of rising sun, The State 

lies between 26° 28’ and 29° 30’ North latitude and 90°30’ and 

97°30’ East longitude. Mc-Mohan Line bounds it in the north, in 

the east by China and Burma (Myanmar), in the south by the states 

of Assam & Nagaland and in the west by Bhutan. Most of 

Arunachal Pradesh is mountainous. Its terrain consists of lofty, 

haphazardly aligned ridges that separate deep valleys and rise to 

the peaks of the Great Himalayas. The state’s main rivers are the 

Brahmaputra known in Arunachal Pradesh as the Siang, and its 

tributaries, the Tirap, the Dibang, the Lohit (Zayu Qu), the 

Subansiri and the Bhareli. The project lies in the seismic zone V. 

9.1.1 LOCATION 

The dam site of the proposed project is located across river Mathun 

near Maron village which is below the 9 km from Anini on Anini- 

Mipi road, having Latitude 28°49’52”N and Longitude 95°52’16” 

in Dibang Valley district of Ar. Pradesh. The river bed level near 

the dam site is 1200m. The powerhouse site is located at a distance 

of 25 km (18 km by road and 7km by foot track) from Anini near 

village Emini. 

9.2 PHYSICAL ENVIRONMENT

101 



9.2.1 CLIMATE/METEOROLOGY 

The Mathun basin falls within climate Zone-III comprising of 

China, Tibet, North and North Eastern part of Ar. Pradesh. 

Rainfall generally occurs during May to October while the months 

of Nov. to Feb are generally dry. Occasional rainfall occurs during 

March and April . The climate of Zone-III can be classified as 

“Mountain Climate” because of atmospheric transparency 

isolation, as mountains are stronger and richer in ultraviolet 

radiation than at sea level. Mountain slopes exposed to the sun 

experience burning heat while slopes in shadow may be quite cold. 

Rainfall is very high and the climate remains very humid. In 

general, the temperature is very cold in the places of high altitude 

with temperature dipping as low as 2° C. 

The climate of the foothills is subtropical; in the mountains, 

temperatures decrease rapidly with altitude. Rainfall averages 

between 2000 and 5000mm in Dibang valley in a year. 

9.2.2 TOPOGRAPHY 

The entire territory forms a complex hill system with varying 

elevations ranging from 300m in the foothills and gradually 

ascending to about 6000m, traversed throughout by a number of 

rivers and rivulets.The topography of the area is rugged with deep 

gorges and high hills. The slopes in the valley are very steep with 

thick vegetation. Some of the areas are inaccessible. Many streams 

cut across the valley slopes. The area is marked by characteristic

102 



periglacial topography with sharp crested ridges and sculptured 

‘whale back’ hill slopes and marginal glacial features. The area is 

marked by typical U-shaped valleys and presence of terminal and 

lateral morains, which suggest an early quaternary glaciation in the 

area. Fluvial sediments are more prevalent in Mathun river valley 

than Dri river valley. The main terminal morain seen in this valley 

is at Amini. 

9.2.3 SOILS 

The general and average soil character of cultivable land in the 

district is mainly alluvial and composed of a mixture of sand 

(coarse to fine) and clay in varying proportions. Soils in the area 

are results of degradation and weathering of rocks as well as 

depositional features in the form of river terraces. The soil on the 

slopes is mainly composed of silt and support good vegetation. The 

rocks exposed in the area are prone to weathering due to heavy 

rainfall and their mineral constituents. The clayey soils formed on 

river terrace due to river deposits are fertile and has been 

developed into paddy fields by the local inhabitants. 

9.2.4 GEOLOGY 

The project area falls within the Diorite -Granodiorite –Granite 

complex of the Upper Dibang valley. The granodiorite/diorite 

exposed in the area is medium to coarse grained, mesocratic, 

greenish-grey rock and consist of plagioclase, quartz, potash 

feldspar and several other mafic minerals (epidote, Biotite, 

amphibole, apatite, sphene, chlorite etc). Granodiorite grades into

103 



Granite with a gradual increase in quartz & K-feldspar content. It 

shows gneissocity in many areas. The rock is intruded by several 

quartz & pegmatite veins ranging in thickness from less than one 

meter to more than 10 meters. 

9.2.5 SEISMICITY 

The entire north east region has been classified in zone-V of the 

seismic zoning map of India. Though MBT and MCT associated 

with the tectonic activity are located at a far distance from the 

project area and the proposed project area has not experienced any 

major earthquake shocks in the recent past, adequate seismic 

design parameter will have to be determined for safe design of the 

civil structures. 

9.2.6 CATCHMENT AREA 

The project is located in the Mathun basin, which is a part of the 

greater Dibang basin situated in the North Eastern part of India 

with its catchment area entirely in Indian territory bordering Tibet. 

The total catchments are of the Mathun river at the dam site is 2600 

sq.km. The entire catchment area is in the hilly terrain. The 

northern most past of the catchment area lies in the snow belt. 

Most of the discharge contribution of the river comes from rainfall. 

9.2.7 RIVER SYSTEM 

River Dri confluences with Mathun River near Amboli after which 

it is known as Dri/Dibang River. River Dibang meets Lohit River 

at Sadia and the combined flow meets river Brahmaputra near 

Kobo Chapari. The River originates form the southern flank of the

104 



Great Himalayan ranges and very close to the Indo-Tibet border. 

The river cuts through deep gorges and difficult terrain throughout 

its journey from North to South in Dibang Valley district till it 

meets the Dri river. 

9.2.8 LAND USE PATTERN 

Total land requirement for the construction of various project 

components is about 1251 ha out of which 456 ha is private land. 

Most of the land falls under the category of Forest land. The land 

use pattern of the submergence and 7 Km radius from the dam site 

has been studied using satellite data. These studies have been 

conducted by NRSA, Hyderabad by using IRS-1D LISS-III & 

PAN merged satellite data and using ERDAS Imagine image 

analysis software. The detailed report prepared by NRSA is 

enclosed as Annexure 9.1. 

9.2.9 WATER QUALITY 

The river Mathun flows through forest areas in its entire course. 

Population density along the reservoir length is very thin. Industry 

or other such establishments are absent. The low cropping density 

coupled with negligible agro-chemical loading also means that 

pollution load due to agrochemicals is quite low. Hence in the 

absence of any major anthropogenic and other industrial 

establishments in the area, it can be concluded that there are no 

major source of water pollution in the area. Thus water quality of 

the river is generally expected to be very good. However water 

quality analysis (Physico-Chemical analysis) of river water would

105 



be conducted as a part of the EIA & EMP Study for the proposed 

project to determine the quality of river water. 

9.3 BIOTIC ENVIRONMENT 

9.3.1 VEGETATION 

In Ar. Pradesh, forest are constitutes about 82% of the total 

geographical area (83,743 sq.km.). The favourable rainfall, 

temperature, high humidity, undulated topography with lofty hill 

ridges and deep valley and soils have resulted in varied ecology 

diversity which subsequently influenced a very rich and 

fascinating vegetation in the North Eastern states. Among the seven 

northeastern states, Ar. Pradesh is the largest and it exhibits the 

riches types in terms of biodiversity. Vegetation of Ar. Pradesh can 

be classified into the following major categories: 

1. Tropical 

2. Sub-tropical 

3. Temperate 

4. Sub-Alpine & Alpine 

9.3.2 FLORA 

The forest type varies with altitude. There are mainly three types 

of forests in Dibang Valley district 

1) Sub-tropical 

2) Temperate 

3) Sub-alpine & Alpine. 

Some of the floral species reported in the area are as under:

Sl.No. Botanical Name 

1 Terminalia myriocarpa 

2 T.bellireca 

3 T.chebula 

4 Altingia excelsa 

5 Laluma phellocarpa 

6 Albizia lucida 

7 Albizia procera 

8 Acacia caesia 

9 Mesua ferrea 

10 Canaruim strictum 

11 Largerstromia flostregina 

12 Duabanga grandiflora 

13 Magnolia Sp. 

14 Kedia calycina 

15 Bombax ceiba 

16 Michalia champaca 

17 Dillenia indica 

106 



9.3.3 FAUNA 

Fauna reported in the region is rich in variety and number. 

Important species of wildlife reported in the area are detailed 

below: 

(I) MAMMALS 

Sl.No. Common Name Zoological Name 

1 Leopard Panthera pardus 

2 Jungle Cat Felis chaus 

3 Fishing Cat Felis Viverrina 

4 Goral Nemorhaedus goral 

5 Musk deer Muschus 

mochiferus

107 



6 Gaur Bos gaurus 

7 Sambur Cervus unicolor 

8 Wild bear Sus scrofa 

9 Indian hare Ispus nigricaulis 

10 Wild dog Cuon alpinus 

11 Red Panda Aliurus fulgens 

(ii) BIRDS 

Important birds reported in the region are Satyr tragopan, 

Temminck’s tragopan, Monal pheasant, owl, eagle, dove, hornbill, 

woodpecker, three toed forest kingfisher etc. 

(iii) SNAKES 

Snakes reported in the region are both poisonous and non- 

poisonous. Banded krait (Bagrarus bagraus), King cobra (Naja 

bannah), Cobra (Naja naja), Coral snakes (Callrphris 

macalicellerdi), Python (Python nolurus) are few of the poisonous 

snakes reported in the region. Common Indian Black snake, Whip 

snake, Himalayan cat snake, Himalayan keel back etc. are few of 

the non-poisonous snakes reported in the region. 

9.3.4 AQUATIC FAUNA 

The principal fish species are in the river system of Dibang Valley 

are:

Sl No. Common Name Zoological Name 

1 Mahseer Tot tor; T putitora 

2 Snow trout Schizothorax sp 

3 Carps Labeo sp. 

4 Cat fish - 

5 Garra Spp - 

108 



Mahaseer is the migratory fish species that is found in Dibang 

valley. Acrossochcilus hexagonolepsis is found upto an altitude of 

1500m. It is commonly known as Chocolate mahaseer. 

Schizothorax sp is found in the higher altitude and is a cold-water 

fish and often young ones are found in the lower stretches of river 

during winter months. 

9.3.5 EXISTENCE OF ANY PROTECTED AREA IN THE 

PROJECT VICINITY 

Dibang wild Life sanctuary is located in the area, which is approx. 

27 Km upstream of the proposed damsite as per information 

collected by NRSA.. All the project components and the proposed 

colonies are much beyond 7 km radius from the wild life sanctuary. 

The sanctuary involves approximate 414900 ha. It was notified in 

November 1991 under Wildlife (Protection) Act, 1972. The 

sanctuary falls under moist temperate and alpine forest zone. In the

109 



northeastern side of the sanctuary run the international Indo-China 

boundary. 

9.4 SOCIO-ECONOMIC ENVIRONMENT: 

9.4.1 POPULATION 

Total area of Dibang valley district is 9129 sq.km with its head 

quarter at Anini. As per provisional population, census 2001 total 

population of the district is 7152. Out of which male population is 

4167 and female population is 2985. Density of population per sq. 

km. is 1 ( Approx.) and the sex ratio is 716 females per 1000 

males. The population belongs to mainly Idu-Mishimi tribal group. 

9.4.2 LITERACY 

Dibang valley district has the literacy rate of 42.24% Literacy rate 

of male and female population in the district is 46.32% and 36.55% 

respectively. 

9.4.3 AGRICULTURE 

Agriculture is one of the major occupation of the locals in the area. 

The main agricultural products are Paddy, Maize, Millet, Potato, 

Cabbage, Tomato, Beans, Brinjals, Green Chilly and Lai. The 

people have their own permanent agricultural field for cultivation. 

In addition people also practice Jhum (Shifting cultivation). This 

shifting cultivation is also known as flash and burn agriculture in 

which trees and grasses are burnt in a patch of land mostly forest so 

that a crop may be raised for a few seasons and after that it is 

shifted to a new place.

110 



9.4.4 HORTICULTURE AND SMALL SCALE INDUSTRIES 

The department of horticulture has encouraged people to grow fruit 

of Citrus variety. Pine apples and Citrus fruits grow in abundance. 

Main horticulture crop of the area are Plum, Orange, Banana, Peas, 

Apple, Walnut, and Chestnut. People have also started small scale 

industries with locally available material like cane, bamboo etc. 

9.4.5 EDUCATION: 

To cater the educational needs of the local populace, the district 

administration has constructed several schools in the region. The 

district has 1 Higher Secondary Schools, 5 Middle Schools, 10 

Primary School and 1 Pre-primary School. 

9.4.6 MEDICAL AND PUBLIC HEALTH 

For providing medical and health services, following medical 

facilities are available in the district. 

Sl.No. Facility Number 

1 District Hospital 1 

2 Community Health 

Centre 

3 Health Sub Centre 3 

4 Medical Centre 1 

5 Leprosy Unit 1 

1

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9.4.7 TREND OF SOCIO-CULTURAL AND RELIGIOUS 

CHANGES DURING THE LAST DECADE 

The Dibang Valley District is an abode of one main tribal 

population group namely the Idu Mishmis. It has been found that 

prominent tribe i.e. Idu Mishmis has been undergoing a steady 

transformation in the field of socio-cultural, economic and to some 

extent in religious aspect. Improvement in agriculture and 

horticulture practices, extension of administration, implementation 

of various developmental schemes particularly in the field of 

education, agriculture, health care, industries and also in the power 

sector during the last decade have radically changed the socio 

economic profile of the people from traditional to modern. 

However, the people who are still in the interior village are not 

much exposed to modern life style. Younger generations are more 

susceptible to change than the older generation. Most of the people 

are migrating to urban areas in order to have a permanent 

settlement for better living, in search of government job. Business, 

for better education and health facilities and so on. This trend has 

been observed particularly at Anini, being an urban area of the 

District for last one decade. 

The traditional system with regard to marriage, divorce, inheritance 

of property, festivals, kinship system, performance of birth and 

death ritual and other religious and practices are still being 

observed as per traditional norms, with great zeal and vigour. But 

as far as religion is concerned most of the tribes seem to have

112 



embraced Christianity; side by side the traditional religion ‘Doni 

Poloism’ is also in vogue. 

9.5 PREDICTION OF ENVIRONMENTAL IMPACTS 

The impact of the proposed Emini HE Project would be assessed in 

details during environmental impact assessment studies. Impact 

would be assessed in the light of construction of various project 

components, permanent and temporary housing and labour 

colonies, activities like quarrying, dumping and other related works 

vis-a-vis environment ( terrestrial & aquatic) and socio-economic 

aspects. 

9.5.1 IMPACTS ON LAND ENVIRONMENT 

Total submergence area including riverbed is 166 

ha. As per the Landuse map prepared by NRSA for Submergence 

area, 94.85% of the area is under various categories of Forest Land 

including river cource and dry river bed, where as 3.5 % is open 

scrub category , 1.59% is barren rock outcrop and 0.06% is 

settlement. No Agriculture land and negligible Human Settlements 

is observed in the area. As such no major impact is anticipated on 

the land environment. The land required for the project is primarily 

forestland. The direct impact of construction activity of a water 

resource project in a hilly terrain is generally limited to the vicinity 

of the construction sites. Submergence of forest area in primary 

impact zone may not reduce the availability of resources for the 

local people as this region has less population. This would result in 

significant changes at the structural resource level in forest. The

113 



acquisition of land for various project activities would also lead to 

cutting of vegetation on these lands. Most of the environmental 

impacts resultant of construction work are temporary in nature 

rarely lasting beyond the construction period. All these issues are 

to be properly addressed in the EIA/EMP of the project so that the 

long term effects, if any, can be minimized. Landslides are also 

severe in the Dibang Valley due to adverse geological situation and 

seismo-tectonic activities. This aspect will also be studied in detail 

in EIA study and accordingly feasible remedial measures shall be 

proposed for restoration of the landslide areas. 

9.5.2 IMPACT ON WATER ENVIRONMENT: 

The construction of a reservoir replaces the river eco-system by a 

lacustrine ecosystem. The vectors of various diseases breed in 

shallow areas not very far from reservoir margins. In the proposed 

project area, malaria is the prominent vector borne disease. There 

are chances that its incidence may increase due to the above- 

mentioned reason. 

Because of the regulated flow of water some changes is also likely 

in the aquatic environment in the downstream areas of the project. 

The important changes that are likely to happen in this area are: 

reduction in flow rate, changes in water temperature, reduction in 

population of stenothermal species (species adapted to small 

temperature range) and increase in population of eurythermal 

species (species adopted to higher temperature range). During the 

construction phase there may be some instances of excavated and 

quarried material getting washed away along with the rain water

114 



that may cause turbidity or sedimentation downstream. Natural 

sedimentation emanating from severely degraded catchment area is 

one of the important issues to be addressed. Also the problems of 

waste disposal and management (human excreta and domestic 

sewage) due to congregation of large population of migrant 

labourers may be encountered. Proper waste management 

measures are required to be implemented during the construction 

phase of the project so as to protect water body from pollution. 

9.5.3 IMPACTS ON AIR AND NOISE ENVIRONMENT: 

Impacts on the air environment is only limited to the construction 

period of a hydropower project. The major sources of air pollution 

during construction phase are emission from crushers, DG sets, 

construction equipments etc. Thus local air pollution (including 

dust and odour) will result from the operation of plant machinery 

and traffic. Noise and vibration due to construction activities (e.g. 

blasting, machinery and traffic) may disturb local wildlife and 

human populations. However, there will be only short-term 

increase in emissions like SO2 and Suspended Particulate Matters 

(SPM) during the construction period of the project. The level of 

noise would also decrease substantially once the construction phase 

is over. Hence no major impact is anticipated on this account. 

9.5.4 IMPACTS ON FLORA AND FAUNA 

The direct impact of construction activity of a water resources 

project in a hilly terrain is generally limited to the vicinity of the 

construction sites. This may alter the local diversity of flora and 

also affect habitat available for fauna. Changes to, or loss of habitat

115 



will affect areas used for mating, breeding, nursing, moulting, 

feeding, and drinking for both resident and migratory wildlife. 

The extent and severity of these effects will vary according to the 

existing habitat and the particular species involved which would 

be known after detailed study of flora and fauna is done during the 

comprehensive EIA/EMP study and suitable mitigation measures 

would be formulated and implemented in consultation with the 

State Forest Department of Arunachal Pradesh. Although there is 

one wildlife sanctuary located within 7 km. radius from the 

periphery of the proposed reservoir, the project will not involve 

any portion of this sanctuary. However, detailed study with respect 

anticipated impacts if any on the wildlife Sanctuary shall also be 

undertaken during EIA studies to access the impact of the project 

especially during construction phase. 

9.5.5 IMPACTS ON AVIFAUNA 

The construction of the proposed dam will lead to formation of a 

reservoir, which will have a fluctuation of 8-10 m in the water 

level, which precisely means the reservoir bank will remain wet 

throughout the year. Due to such reasons, some aquatic grasses 

may grow along the reservoir banks. Such conditions are generally 

ideal for various kinds of birds, especially water birds. However 

because of the presence of a good habitat it is quite likely that 

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

cold climatic areas could also use this area during the winter 

season.

116 



9.5.6 IMPACTS ON FISHES 

There are a few migratory fish species reported in the Dibang river. 

A dam will fragment and isolate upstream resident fish. The 

resident species may congregate in the tail water release site. Fish 

from upstream will occasionally sweep downstream during the 

monsoon, stay in the tail water or swim further downstream. A dam 

may obstruct the route of the long and mid-distance migratory fish. 

The impact of the dam on fish particularly migratory fish species 

would be studied in detail during comprehensive EIA study and 

based on it the suitable mitigatory measures would be suggested. 

9.5.7 IMPACTS ON SOCIO-ECONOMIC 

ENVIRONMENT: 

One village, Maron having 2 houses will be fully submerged due to 

the proposed project. As a part of the Environmental Impact 

Assessment Study, a detailed socio-economic survey would be 

carried out to determine the following: 

Information on various aspects of the affected population 

viz; demographic details, socio-economic and cultural 

characteristics, enumeration of personal properties of the affected 

population, education level and occupational profile etc. 

Enumeration of social infrastructure and community 

property resources in the submergence area. 

Ethnographic assessment of PAFs.

117 



At present, there are small business and little employment facilities 

in the project area. However with the construction of the project 

new business and employment opportunities will open up for the 

local people which are likely to improve the economic conditions 

of the local people. Further, there will be development of 

infrastructure facilities as housing, water supply, medical facilities, 

schools, transportation and communications During the 

construction of the project the basic problem relates to 

management of large population that migrates to the area in search 

of jobs and other allied activities. Thus migration of a population 

having different cultural, ethnic and social backgrounds has its own 

advantages and disadvantages. Exchange of ideas, cultures between 

various groups of people would result in a healthy bonding 

amongst the population at large. A new culture having a distinct 

socio-economic status with an entity of its own would develop. As 

a result of this project there would be all-round development of the 

region. Project is not causing any impact on the sites of 

archaeological and religious importance. 

9.6 ENVIRONMENTAL MANAGEMENT PLANS 

Based on the findings of the Environmental Impact Assessment 

study, following Environmental Management Plans shall be 

formulated to mitigate the adverse impacts and to maximize the 

positive impacts of the project construction on the environment: 

Catchment Area Treatment Plan. 

Restoration of landslide areas.

Resettlement and Rehabilitation Plan. 

Biodiversity conservation plan. 

Compensatory Afforestation 

Restoration of quarry sites / dumping areas. 

Fish Management Plan. 

Health Management Plan. 

Solid waste Management Plan 

Disaster Management Plan. 

Water Quality Management Plan. 

118 



CHAPTER X 

INFRASTRUCTURE 

119 



10.1 IDENTIFICATION OF THE BROAD 

INFRASTRUCTURE REQUIREMENT FOR 

IMPLEMENTATION OF THE PROJECT. 

Emini Project is located in Dibang Valley District of Arunachal 

Pradesh. The nearest town is Anini, the district head quarter of 

Dibang valley district. The dam site location is below 9 km point 

on Anini-Mipi metalled road from Anini near Maron Village and 

Power house is located near village Emini which is approachable 

from 18 km point on Anini-Roing road from Anini. 

Since the infrastructure development in the project area or its 

vicinity is not very encouraging, the project has to do meticulous 

planning in development of Infrastructure such as Road 

communication network, Residential/non-residential building, 

Workshop, Stores and Explosive magazine, Fueling station, 

Construction power, Telecommunication etc required for the 

project. The land requirement for its development has to be seen 

with regard to its availability. There may not be much land 

available for infrastructural development at dam site of the project. 

It may therefore be planned to have the main colony for the project 

at Anini and temporary accommodation/field hostels etc at the dam 

site. some residential accommodation can be developed at 16 km 

(GREF camp) i.e. about 7 km from the dam site location on Anini- 

Mipi road. Some residential colony can be developed at Power

120 



house site also. The infrastructure facilities required for the project 

is explained hereunder: 

10.1.1 ROAD COMMUNICATION NETWORK 

The road to dam site is already there but this needs further 

development for plying of heavy equipments. The main road from 

Roing to Anini though a State highway being maintained by 

Boarder Road Organisation will require further 

widening/development. Other roads required for the project are as 

under: 

Bifurcation road to dam site from Anini-Mipi road at about 9km 

location, Road from dam site to Power house site on the right bank 

of Mathun river, Road head to Power house at 18 Km point of 

Anini-Roing road, Quarry roads at Power house/Dam site, Internal 

colony roads etc. 

10.1.2 RESIDENTIAL/NON-RESIDENTIAL 

COMPLEX 

Residential colony can be developed at Anini for the dam site and 

HQ of the project can also be established at Anini only. 

Non-residential building may include Admn. Building, School, 

Hospital, Bank, Post office, Field hostel, guest houses, Clubs, 

auditorium, stores etc.

10.1.3 WORKSHOP 

121 



Workshop facility for the project has to be developed at suitable 

location at dam and Power house sites separately. This may involve 

facilities like engine repairs, overhauling, transmission related 

electrical shop Machine shops, OTR Tyre repair shop, fabrication 

shops, office and canteen etc. a Parking yard has to be created 

within the workshop complex. 

10.1.4 STORES AND EXPLOSIVE MAGAZINE 

Explosive magazine near to Dam site and Power house site 

locations has to be developed based on project requirements. 

Central store can be created near Power House site for cement, 

steel and other miscellaneous items. 

10.1.5 FUELING STATION 

A fueling station also need to be established for project vehicles 

and construction equipments with storage capacity of at least 20 

KL of Petrol and 30 KL of HSD. 

10.1.6 CONSTRUCTION POWER 

Dibang Valley District has about 1.85 MW of Power supply 

through Mini/Micro establishment, which is not even sufficient to 

meet to their local domestic demand and thus the State Govt. has 

DG sets also to feed the shortfall in demand. There is no Power 

available in the region, therefore the project has to make its own 

arrangement of Power supply for its construction activities as well

122 



as domestic need and thus nearly 10-12 MW of power through DG 

Sets has to be arranged to meet the project demand. 

10.1.7 TELECOMMUNICATION 

Like other essential amenities available in the region, the 

telecommunication network is also not that dependable and as such 

the provision for V Sat connection, LDST connection from MTNL 

exchange Delhi, local wireless communication etc have to be kept. 

OFC connection between BSNL telephone exchange at Anini and 

project site has also been planned together with one hi-tech PABX 

of 400 lines for office, residence and project sites.

CHAPTER - XI 

123 



CONSTRUCTION PLANNING & SCHEDULE 


The equipment planning & construction methodology of Emini 

H.E. project (4x125MW) has been developed on following 

considerations. 

1. The project construction period has been considered as six 

years after completion of Stage-I & Stage-II activities. 

2. Available Geological Data at PFR stage. 

3. Requirement of Construction Equipment has been planned to 

handle the quantities worked out on the basis of preliminary layout. 

4. Five months (from May to September) rainy season has been 

considered while planning surface works. The progress will 

considerably slow down during rainy season. 

Construction schedule has been placed at Plate 11.1 

11.2 CONSTRUCTION METHODOLOGY 

11.2.1 INFRASTRUCTURE WORKS 

The main infrastructure development is proposed to be initiated in 

during stage II activities and completed in a period of 12 months 

during stage III activities. During infrastructure period Land 

Acquisition, construction of approach roads, bridges & culverts, 

Deleted: (A)

124 



arrangement of construction power will be undertaken. Platform to 

accommodate batching plant, stores for construction material, site 

workshop, offices and other buildings (residential/ non residential) 

colonies will also be developed in infrastructure period. Crawler 

Dozer, Loader cum Excavator, Motor Grader, Air compressor, 

Road Roller etc. are proposed for deployment during infrastructure 

stage. 

11.2.2 DIVERSION OF RIVER 

The excavation of 12 m finished diameter, Horse shoe shaped 

600m long diversion tunnel would be carried out by heading & 

benching method from 7 th month. Excavation of Diversion Tunnel 

will be carried out with 2 Boom drill jumbo, Air Track/ wagon 

drill, jack hammer, 2.5Cum Side dump Loader, 25T LP dumper 

etc.. Excavation & concreting of Diversion tunnel would be 

completed in 21 months. The concreting equipment proposed are 

120 cum/hr Batching & Mixing plant, Concrete pump, 4.0/ 6.0Cum 

Transit mixer, shotcrete m/c, Grout pump and shutters. U/s & D/s 

Coffer dam would be constructed immediately after construction of 

diversion tunnel within a period of 8 months to divert the river. 

Construction of Coffer dam would be carried out by 1.0 /3.0 cum 

Hyd. Excavator, 35T Rear dumper & Crawler Dozers etc. 

11.2.3 CONCRETE DAM 

After construction of coffer dam and river diversion, the excavation 

of river bed will be taken up. The excavation & foundation 

treatment of Dam would be carried out in 7 months. Excavated

125 



material will be handled by 3.0 cum Hyd. Excavator and 35t Rear 

dumpers. Concreting of Dam & HM work would be carried out in 

further 28 months. Concreting would be done by 2x15T Cable 

ways, 1 No. 150 cum/hr Batching& Mixing plant and 300TPH 

Aggregate Processing plant. 

11.2.4 INTAKE STRUCTURE & DESILTING 

CHAMBER 

4 Nos. desilting chambers of size 350mx18mx 25m each would be 

excavated in 21 months. For excavation of desilting chamber, 

2Nos. intake structures would be excavated first in about 3 months. 

The branch of intake tunnels would be extended upto the full 

length of desilting chamber. Thereafter, it will be expanded side 

wise to the full width of desilting chamber resulting in desilting 

chamber dome. Mucking of excavated material would be done 

through the intake. After the excavation of desilting chamber 

concreting will be carried out. The construction of all the four 

desilting chambers will be taken up simultaneously with four sets 

of equipment. Excavation of silt flushing tunnel & gate operation 

chamber would be a parallel activity. The equipment to be 

deployed are Jack hammers, wagon drills, air compressors, loader, 

excavators, Dumpers, concrete pump, transit mixers etc. 

11.2.5 HEAD RACE TUNNEL 

Construction of 2Nos. 5 km long, 8m finished diameter horse shoe 

shaped Head Race Tunnel is proposed by heading & benching 

method. The excavation of adits would be carried out in 6 months.

126 



Excavation of HRT would be carried out by 2 boom drill jumbo, 

Air track /wagon drill, 2.5Cum Side Dump Loader and 25T L.P. 

Dumpers. Concreting will be carried out by Concrete pump, 

Concrete shutters, 4.0/6.0cum Transit Mixer etc. The total 

construction period for the HRT will be 54 months. 

11.2.6 SURGE SHAFT 

Construction of 2 Nos. 25m dia. 75m high Surge shaft would be 

taken up from top of surge shaft. Excavation of Surge Shaft would 

involve pilot hole drilling, reaming of pilot hole & enlargement of 

reamed hole. Raise borer, Wagon drill, Jack Hammer, L.P. 

Dumpers etc. will be deployed for excavation of Surge shaft. 

Concreting would be completed employing 2 m shutter. 

Construction of surge shaft would be completed in 46 months. 

11.2.7 PRESSURE SHAFT 

7.0 m diameter, two nos. pressure shaft will be excavated in the 

same way as surge shaft by deploying Raise borer , Jack hammer 

etc. Steel liner erection & concreting will be carried out by 

deploying 10/20 t winches, Slipform liner etc. Construction of 

Pressure shaft & erection of penstocks would take around 44 

months. 

11.2.8 POWER HOUSE 

4 X 125 MW (500 MW) underground power house cavern (120m 

(L) X 24m (w) X 45m(H) ) & transformer cavern (100m(L) x 

20m(W) x 25m(H)) would be excavated in 18 months. For

127 



excavation of Power House Main Access Tunnel & adits would be 

excavated in about 6 months. A branch from this Main Access 

Tunnel would be extended upto the crown of power house 

followed by extension of this extended MAT upto full length of 

power House. Thereafter, it will be expanded side wise to the full 

width of power house resulting in Power House Cavern. Mucking 

of excavated material would be done through the adit. From Power 

House Cavern 4 shafts of 2.0 m diameter would be excavated up to 

the bottom level of draft tube followed by benching of Power 

House cavern upto the bottom of Power House. Mucking will be 

carried out through TRT. The equipment to be deployed for 

excavation are jack hammers, wagon drills, air compressors, 

loader, excavators, dumpers, winches etc. Concreting of 

Powerhouse would be carried out along-with Machine erection in 

30 months. Installation & Testing of Machine would be undertaken 

in such a manner that Project get commissioned in 72 nd month from 

the start of Project construction. 

11.2.9 TAIL RACE TUNNEL 

2 Nos. 250m long horse shoe shaped Tail Race Tunnel having 8 m 

finished diameter will be excavated by heading & benching 

method. Excavation of Tail Race Tunnel would be carried out with 

2 boom Drill Jumbo, Wagon drill, 2.5 cum. Side Dump Loader & 

20/25 t LP Dumper etc. The TRT excavation will be completed in 

12 months. After the completion of TRT, mucking of power house 

would be carried out through TRT. After the excavation of power

128 



house the TRT will be concreted with the help of concrete pump, 

Transit mixer, Batching & mixing plant etc.

CHAPTER -XII 

COST ESTIMATE 

129 



12.1 PRELIMINARY COST ESTIMATE FOR CIVIL, 

HYDRO-MECHANICAL, ELECTRO-MECHANICAL & 

TRANSMISSION WORKS : 

The estimate has been prepared to arrive at the Capital Cost of 

Emini H. E. Project and is of Pre-feasibility level of accuracy. The 

base date of the estimate is June 2003 and the Cost is expressed in 

Indian Rupees. The Cost Estimate is divided into Civil, Electrical 

and Transmission Works. For Civil Works, the sub heads are as 

under: - 

12.1.1 I-WORKS 

Under this head, provision has been made for various components 

of the Project as detailed hereunder:- 

12.1.2 A-PRELIMINARY 

Under A-Preliminary, provision has been made for all surveys and 

investigations to be conducted to arrive at the optimum of the 

Project Components. 

12.1.3 B-LAND 

This covers the provision for acquisition of land for construction of 

the Project, colonies, offices and stores and compensation for trees 

and standing crops etc. This head also contains the provision for

130 



Rehabilitation and Resettlement measures for Project Affected 

People. 

12.1.4 C-WORKS 

This covers the cost of Diversion Tunnel, Coffer dam and Concrete 

Dam including Spillway and Plunge pool along with associated 

Hydro-mechanical works. 

12.1.5 J-POWER PLANT CIVIL WORKS 

This covers the cost of project components viz. Intake Structure, 

Desilting Chamber, Headrace Tunnel and TRT, Power House and 

Transformer Cavern, Pressure Shaft, Surge Shaft and other 

Appurtenant Works along with associated Hydro-mechanical 

works. 

The quantities indicated in the estimates for C - Works & J-Power 

Plant Civil Works (Civil & HM) are calculated from the 

preliminary Engineering drawings and as per experience of other 

on-going or commissioned projects. 

The unit rates for various items are taken as per the Guidelines 

issued by CEA for preparation of PFRs. It has been assumed that 

the quarry is available at a distance of 10 Kms from the work site. 

12.1.6 K-BUILDINGS 

Buildings, both residential and non-residential have been provided 

under this head. Under the permanent category only those

131 



structures have been included which shall be subsequently utilized 

during the operation and maintenance of the project. The costs are 

worked out on plinth area basis prevalent in the area for the type of 

construction involved. 

12.1.7 O-MISCELLANEOUS 

Provision under this head has been made @ 4% of I- works for the 

Capital & running cost of Electrification, Water Supply, Sewage 

Disposal, Fire Fighting Equipments, Medical Assistance, 

Recreation, Post Office, Telephone and Telegraph Office, etc. The 

Provisions have been made for the security arrangements, 

inspection vehicles, schools, transport of labour, laboratory testing, 

R&M of guest house and transit camps, community center, 

retrenchment compensation, photographic instruments as well as 

R&M charges etc. 

12.1.8 P-MAINTENANCE DURING CONSTRUCTION AND 

Y-LOSSES ON STOCK 

A provision of 1% and 0.25% of C-Civil works, J-Power Plants, K- 

Buildings & R-Communications has been made for maintenance of 

works during construction period and losses on stock respectively. 

12.1.9 Q-SPECIAL TOOLS AND PLANT 

It is assumed that the work will be carried out through Contracts 

and not through departmental construction. Accordingly, provision 

for general purpose equipment and inspection vehicle only has 

been made as per CWC guidelines.

132 



12.1.10 R-COMMUNICATION 

Provision under this head covers the cost of new roads, 

widening/improvement of roads and strengthening of bridges. The 

costs of roads and bridges are based on the rate structure prevalent 

in the area of the Project, for the type of construction involved. 

12.1.11 X-ENVIRONMENT AND ECOLOGY 

Provision under this head has been taken as 2% of I -Works 

towards bio-diversity Conservation, creation of Green Belt, 

Restoration of Construction Area, Catchment Area Treatment, 

Compensatory Afforestation etc 

12.1.12 II-ESTABLISHMENT 

Provision for establishment has been made at 8% of I-works minus 

B-Land for civil works. 

12.1.13 III-TOOLS AND PLANTS 

This provision is distinct from that under Q-Special T&P and is 

meant to cover cost of survey instruments, camp equipment and 

other small tools and plants. The outlay is provided at 1% of cost 

of I-works. 

12.1.14 IV-SUSPENSE 

No provision has been made under this head as all the outstanding 

suspense are expected to be cleared by adjustment to appropriate 

heads at completion of the project.

133 



12.1.15 V-RECEIPTS AND RECOVERIES 

Under this head, provision has been made for estimated recoveries 

by way of resale or transfer of equipment used in infrastructure 

works. 

12.1.16 ELECTRICAL WORKS AND GENERATING PLANT 

The cost of Generating Plant and Equipment is based on 

indigenous sources. The prices of auxiliary equipment and services 

are based on prevailing market prices/costs incurred at other 

ongoing or commissioned projects.

134 



135 



136 



137 



138 



139 



140 



141 



142 



143 



144 



145 



146 



147 



148 



149 



150 



151 



152 



153 



154 



155 



156 



157 



158 



159 



160 



13.1 GENERAL 

CHAPTER - XIII 

ECONOMIC EVALUATION 

161 



The Project has been contemplated as a run-off the river scheme 

on river Adjon/Mathun. The project is estimated to cost Rs. 

2739.21 crores excluding IDC at June 2003 Price Level. Sale 

price of energy generated at powerhouse bus bars has been 

worked out as Rs. 3.99 per unit.(Table 13.2) with free power to 

the home state and Rs.3.51 per unit (Table 13.2 A) without free 

power to home state . 

13.2 ECONOMIC JUSTIFICATION: 

The energy generation of the project with an installed capacity of 

4 x 125 MW has been estimated at 1695.45 MU in a 90% 

dependable year. 

13.3 COST ESTIMATES AND PHASING OF 

EXPENDITURES 

The cost of construction of the project has been estimated at June 

2003 price level with a construction schedule of 7.5 years including 

1.5 years for Infrastructure works. 

The estimated Present Day Cost of the project is Rs2739.21 Crores 

without IDC at June 2003 Price level.

162 



13.4 PHASING OF EXPENDITURE 

The phasing of expenditure has been worked out on the basis of 

anticipated construction programme. 

The phasing of expenditure without IDC for the present cost is 

shown as below: 

Year Estimated Cost at June 2003 P.L. 

1 st 

2 nd 

3 rd 

4 th 

5 th 

6 th 

7 th 

7.5 th 

(Rs. in Crores) 

109.57 

219.14 

246.53 

356.10 

410.88 

602.63 

493.06 

301.31 

Net Cost 2739.21 

13.5 INTEREST DURING CONSTRUCTION (IDC) 

Based upon above phasing of expenditure the interest during 

construction (IDC) have been calculated with 70:30 debt equity 

ratio and 10.0% interest on loan. (Table 13.1) 

The estimated IDC with estimated present cost is Rs.327.99Crores.

13.6 COST OF ENERGY GENERATION 

163 



The cost of energy generation has been calculated for the annual 

energy generation in a 90% dependable year based upon following 

assumptions. 

1. Debt-equity ratio 70 : 30 

2. Annual interest rate on loan 10.0% 

3. Return on equity 16% 

4. Annual interest rate on working capital 10.0% 

5. O&M Charges 1.5% of Project Cost 

6. Free power to Home State 12% of the energy 

available after losses 

7. Depreciation considered 1/12 th of loan amount 

during loan repayment 

period. 

The levellised tariff of the Project at present day cost works out to 

be Rs. 3.24 Per Unit. (Table 13.3) with free power to the home 

state and Rs. 2.85 per unit (Table 13.3 A) without free power to 

home state.

PLATE 4(A) 

PLATE 4(A) 

GSI REPORT 

164 



15 

16 

49 

50 

133 

134 

135 

136 

137 

138 

139 

140 

141 

144 

145 

146 

147 

148 

149 

150 

151 

152 

153 

154 

155 

160 

142 

143 

165 



166 



TABLE 2.2 

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

Installed Capacity MW 107644 113411 121137 125981 142842 157124 164485 171105 174095 176915 

Peak availability MW 71547 75380 80516 83735 94942 104435 109327 113727 115715 117589 

Peak requirement MW 81492 86650 92135 97968 104169 110930 118129 125795 133960 142653 

Peak Surplus(Deficit) MW -9945 -11270 -11620 -14232 -9227 -6495 -8801 -12068 -18245 -25064 

Peak Surplus(Deficit) % -12.20% -13.50% -13.00% -15.00% -9.00% -6.00% -7.50% -10.00% -14.00% -18.00% 

Energy availability MU 497589 524250 559964 582355 660297 726314 760341 790942 804763 817799 

Energy requirement MU 545674 580324 617175 656366 698045 741882 788472 837988 890614 946545 

EnergySurplus(Deficit) MU -48085 -56075 -57211 -74010 -37748 -15568 -28132 -47046 -85850 -128745 

EnergySurplus(Deficit) % -8.81% -10.00% -9.50% -11.50% -5.50% -2.50% -4.00% -6.00% -10.00% -14.00% 

CAPACITY CONSIDERED TO BE ADDED 

IN RESPECTIVE YEAR OF 10TH AND 

11TH PLAN 

SOURCE: 

2) Web Sites - 

www.cea.nic.in 

www.nhpcindia.com 

www.ntpc.co.in 

NORTH-EASTERN REGION 

1) Power on Demand by 2012 

EASTERN REGION 

NORTHERN REGION 

WESTERN REGION 

SOUTHERN REGION 

A & N ISLANDS 

LAKSHADWEEP 

POWER SUPPLY POSITION OF ALL INDIA 

WITHOUT EMINI HE PROJECT 

10th Plan 11th Plan 

48 MW 38 MW 160 MW 407 MW 80 MW 300 MW 600 MW 2000 MW 1500 MW 





5 MW 

Rangat Bay 

(DG) 

Total 0 MW 5768 MW 7726 MW 4844 MW 16861 MW 14282 MW 7361 MW 6620 MW 2990 MW 2820 MW 

1.Installed capacities are based on summation of installed capacities of all the regions and 69.27 Mw for A&N Islands and Lakshadweep Islands. 

2. Energy availability for the year 2003-2004 onwards have been estimated on the basis of ratio of Energy availability to Installed capacity for the year 2002- 

3. Peak availability for the year 2003-2004 onwards have been estimated on the basis of ratio of Peak availability to Installed capacity for the year 2002-2003. 

4. Energy requirement and peak requirement for the year 2003-2004 onwards is based on the annual increments given at page -117 and 118 of "Sixteenth 

Electric Power Survey of India". 

5. Micro/mini hydel projects under construction have not been considered in this study. 

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

18

TABLE 2.1 

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

Installed Capacity MW 2309 2357 2395 2555 2962 3042 3342 3942 5942 7442 

Peak availability MW 1135 1159 1177 1256 1456 1495 1643 1937 2920 3658 

Peak requirement MW 1209 1307 1412 1526 1649 1785 1933 2092 2265 2452 

Peak Surplus(Deficit) MW -74 -148 -235 -270 -193 -290 -290 -155 655 1205 

Peak Surplus(Deficit) % -6.12% -11.50% -17.00% -18.00% -12.00% -16.50% -15.50% -7.50% 29.00% 49.50% 

Energy availability MU 6195 6324 6426 6855 7946 8161 8966 10575 15940 19964 

Energy requirement MU 6350 6871 7436 8046 8707 9416 10184 11014 11911 12882 

EnergySurplus(Deficit 

) 

EnergySurplus(Deficit 

) 

MU 

% 

-155 

-2.44% 

-548 

-8.00% 

-1010 

-14.00% 

-1191 

-15.00% 

-760 

-9.00% 

-1255 

-13.50% 

-1218 

-12.00% 

-438 

-4.00% 

4029 

34.00% 

7082 

55.00% 

25 MW 38 MW 

KOPILI II 

60 MW 280 MW 80 MW 90 MW 600 MW 2000 MW 1500 MW 

LAKWA 

WH 

TUIRIAL 

TRIPURA 

GAS(MONAR 

BAIRABI LOKTAK 

HYDRO D/S 

KAMENG 

HEP 

SUBANSIRI LOWER TIPAIMUKH 

23 MW 

BAIRABI 

(THERM 

100 MW 

KARBI LANGPI 

84 MW 210 MW 

MPP 

MYNTDU(LI 

10th Plan 

11th Plan 

POWER PLANT 

CONSIDERED TO BE 

ADDED IN RESPECTIVE 

YEAR OF 10TH AND 11TH 

PLAN 

SKA) 

20 MW 

Dhansiri HEP 

23 MW 

Dimapur 

TUIVAI 

HEP 

SOURCE: 

1) Power on Demand by 2012 

2) Web Sites - 

www.cea.nic.in 

www.nhpcindia.com 

www.ntpc.co.in 

DGPP 

NOTE: 

1) Projects shown cleared by 

CEA on CEA web site have only 

been considered. 

2) Projects cleared but not 

programmed for implimentation 

for 10th plan have been 

considered to come up in 11th 

POWER SUPPLY POSITION OF NORTH-EASTERN REGION 

WITHOUT EMINI HE PROJECT 

Total MW 0 MW 48 MW 38 MW 160 MW 407 MW 80 MW 300 MW 600 MW 2000 MW 1500 MW 

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

2. Energy availability for the year 2003-2004 onwards have been estimated on the basis of ratio of Energy availability to Installed capacity for the year 2002-2003. 

3. Peak availability for the year 2003-2004 onwards have been estimated on the basis of ratio of Peak availability to Installed capacity for the year 2002-2003. 

4. Energy requirement and peak requirement for the year 2003-2004 onwards is based on the annual increments given at page -117 and 118 of "Sixteenth Electric Power Survey of 

India". 

5. Micro/mini hydel projects under construction have not been considered in this study. 

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

17

REPLY OF CWC OBSERVATIONS RECEIVED VIDE LETTER NO. 

Consis 

tency 

of data 

4/330/2003 Hyd NE/336-37 dated 21.10.2003 

CWC Observations Reply of NHPC 

(i) Brahmaputra Board in its 

report on Dibang dam had 

mentioned of G&D stations 

existing U/S of the Munli dam 

site. Efforts may be made to 

collect the site specific/more 

realistic discharge data and 

catchment rainfall. 

(ii) A detail contour map of 

Dibang basin to the scale of 

1:2,50,000 showing all the 

details like sub basin 

boundaries, rainfall stations, 

discharge observation sites, 

existing/ongoing projects etc. 

may be furnished. 

(iii) A complete list of all 

(i) Lot of efforts has been 

made to collect all available 

data in the basin, and all 

rainfall and discharge data 

collected and available has 

been given in the data status. 

Efforts are still being made to 

collect more data and the 

same will be used during 

feasibility and DPR stage. 

(ii) The information required 

by CWC cannot be given due 

to unavailability of toposheets 

of 1:2,50,000 scale, covering 

catchment area of Subansiri 

basin. However a catchment 

plan of Dibang Basin as given 

in Brahmaputra Board report 

will be incorporated in PFR if 

desired by CWC. 

(iii) Rainfall and discharge 

stations lying in the entire

Water 

availa 

bility 

studie 

s 

rainfall and discharge stations 

of Dibang basin may be 

furnished. 

(i) The catchment conversion 

factor is very low and efforts 

may be made to collect site- 

specific data or at least 

catchment proportioning 

should be reasonable apart 

from hydro meteorological 

similarity. 

(ii) The series of Munli dam 

site adopted by the project 

authorities for generating the 

yield series at Mihundon dam 

site is the old series supplied 

to Brahmaputra Board by 

CWC. CWC have issued a 

revised series in March 2003, 

which has been incorporated 

in the Draft DPR for Dibang 

project being prepared by 

Brahmaputra Board. In the 

absence of site-specific data, 

the revised series may be 

obtained for generating the 

Dibang basin are not relevant 

for the present projects. 

However, rainfall availability 

status is given in the report. 

(i) As catchment correction 

factor is very low, to make it 

more reasonable rainfall 

variation effect has also been 

taken into account while 

transferring the discharge 

series at Munli Dam site. 


site adopted for generating the 

yield series at proposed dam 

site is taken from table 1.21A 

of latest report made available 

to us vide letter no. 20/7/2002- 

Emb(E&NE)/177 dt.27 th June 

2003. The water availability 

series is based on 17 years of 

data (1985-2001), which is 

reasonable for PFR studies.

Desig 

n 

Flood 

yield series only for the 

purpose of PFR. The yield 

series may be submitted for 

vetting. The water availability 

need to be reviewed based on 

observed rainfall and 

discharge data and series may 

be generated for minimum 20 

to 25 years. 

Short interval data may be 

collected from NHPC 

observation site and the 

design flood may be 

estimated using unit 

hydrograph based on 

observed data. The 

approximate design storm 

may be obtained from IMD 

and 2 bells per day may be 

used in UH approach. In the 

absence of short interval 

concurrent rainfall-runoff 

data the relevant subzonal 

report of CWC may be used 

to calculate the design flood 

and submitted for vetting. 

For such detailed studies as 

suggested for this stage i.e 

PFR, neither the database is at 

all sufficient nor necessacity 

felt by us. During feasibility 

stage, 

deterministic/probabilistic 

approach will be used, based 

on more observed data. 

Regarding the 2-bell theory, it 

is pertinent to mention that 

NHPC has already explained 

its stand in earlier discussions 

with CWC officials during the 

clearance of Teesta Low Dam 

Stage-III and Subansiri Basin 

projects and also vide our 

letter no. NH/DD/HYD/564

Sedim 

entatio 

n 

(i) The sedimentation rate for 

the region is about 0.1765 

Ham/Sq.km/year as per CWC 

studies published in the 

Compendium on silting of 

reservoirs in India, which is 

higher than the rate proposed 

for the project. As stated in 

the report more detail study is 

required. Data may also be 

collected from the completed 

projects of the basin. 

(ii) New zero elevation after 

70 years may be evaluated 

(iii) Revised area elevation 

capacity table after 25 years 

may be incorporated. 

As per the terms of 

preparation of PFRs and as 

emphasized in the meetings 

dt. 4.2.03. Again vide our 

letter no. NH/DD/HYD/2656 

dt 17.7.03 we have stated this 

fact along with the letter 

received from IMD (ref. HS- 

DS(Dam)302/II dt.2 nd July 

2003. 

We are aware of the findings 

of CWC studies published in 

the Compendium on silting of 

reservoirs in India. As per that 

report, the sediment rate 

varies from 0.05658 to 0.2785 

Ham/Sq.km/year for Indus, 

Ganga and Brahmaputra 

basin. The silt rate adopted in 

the present study is based on 

silt rate of Ranganadi, 

Subansiri and Siang basin, 

which looks to be more site 

specific. 

The necessity of detailed 

sedimentation study showing 

the new zero elevation, 

revised area capacity curve 

etc. is not felt during PFR 

stage.

Gener 

al 

conducted by CEA 

sedimentation studies are 

required to be carried out and 

incorporated in the PFRs. 

The PFR must bring out the 

limitations of the hydrological 

studies carried out for the 

PFR and suggest 

improvements, specific 

recommendations for opening 

new hydrological stations, 

method of observations, data 

to be collected etc. may be 

given which will help us as 

guidance to the agency taking 

up the detail 

investigations/DPR must 

review the network in 

consultation with HSO, 

CWC. 

The hydrological studies for 

the PFR may be revised 

incorporating the above 

observations and resubmitted. 

The PFR has pointed out the 

limitation of the studies after 

each study and establishment 

of G&D site, rainfall stations 

etc. are also highlighted in the 

PFR.

REPLY OF CWC OBSERVATIONS RECEIVED VIDE LETTER NO. 

Consis 

tency 

of data 

4/330/2003 Hyd NE/336-37 dated 21.10.2003 

CWC Observations Reply of NHPC 

(i) Brahmaputra Board in its 

report on Dibang dam had 

mentioned of G&D stations 

existing U/S of the Munli dam 

site. Efforts may be made to 

collect the site specific/more 

realistic discharge data and 

catchment rainfall. 

(ii) A detail contour map of 

Dibang basin to the scale of 

1:2,50,000 showing all the 

details like sub basin 

boundaries, rainfall stations, 

discharge observation sites, 

existing/ongoing projects etc. 

may be furnished. 

(iii) A complete list of all 

(i) Lot of efforts has been 

made to collect all available 

data in the basin, and all 

rainfall and discharge data 

collected and available has 

been given in the data status. 

Efforts are still being made to 

collect more data and the 

same will be used during 

feasibility and DPR stage. 

(ii) The information required 

by CWC cannot be given due 

to unavailability of toposheets 

of 1:2,50,000 scale, covering 

catchment area of Subansiri 

basin. However a catchment 

plan of Dibang Basin as given 

in Brahmaputra Board report 

will be incorporated in PFR if 

desired by CWC. 

(iii) Rainfall and discharge 

stations lying in the entire

Water 

availa 

bility 

studie 

s 

rainfall and discharge stations 

of Dibang basin may be 

furnished. 

(i) The catchment conversion 

factor is very low and efforts 

may be made to collect site- 

specific data or at least 

catchment proportioning 

should be reasonable apart 

from hydro meteorological 

similarity. 


site adopted by the project 

authorities for generating the 

yield series at Mihundon dam 

site is the old series supplied 

to Brahmaputra Board by 

CWC. CWC have issued a 

revised series in March 2003, 

which has been incorporated 

in the Draft DPR for Dibang 

project being prepared by 

Brahmaputra Board. In the 

absence of site-specific data, 

the revised series may be 

obtained for generating the 

Dibang basin are not relevant 

for the present projects. 

However, rainfall availability 

status is given in the report. 

(i) As catchment correction 

factor is very low, to make it 

more reasonable rainfall 

variation effect has also been 

taken into account while 

transferring the discharge 

series at Munli Dam site. 


site adopted for generating the 

yield series at proposed dam 

site is taken from table 1.21A 

of latest report made available 

to us vide letter no. 20/7/2002- 

Emb(E&NE)/177 dt.27 th June 

2003. The water availability 

series is based on 17 years of 

data (1985-2001), which is 

reasonable for PFR studies.

Desig 

n 

Flood 

yield series only for the 

purpose of PFR. The yield 

series may be submitted for 

vetting. The water availability 

need to be reviewed based on 

observed rainfall and 

discharge data and series may 

be generated for minimum 20 

to 25 years. 

Short interval data may be 

collected from NHPC 

observation site and the 

design flood may be 

estimated using unit 

hydrograph based on 

observed data. The 

approximate design storm 

may be obtained from IMD 

and 2 bells per day may be 

used in UH approach. In the 


concurrent rainfall-runoff 

data the relevant subzonal 

report of CWC may be used 

to calculate the design flood 

and submitted for vetting. 

For such detailed studies as 

suggested for this stage i.e 

PFR, neither the database is at 

all sufficient nor necessacity 

felt by us. During feasibility 

stage, 

deterministic/probabilistic 

approach will be used, based 

on more observed data. 

Regarding the 2-bell theory, it 

is pertinent to mention that 

NHPC has already explained 

its stand in earlier discussions 

with CWC officials during the 

clearance of Teesta Low Dam 

Stage-III and Subansiri Basin 

projects and also vide our 

letter no. NH/DD/HYD/564

Sedim 

entatio 

n 

(i) The sedimentation rate for 

the region is about 0.1765 

Ham/Sq.km/year as per CWC 

studies published in the 

Compendium on silting of 

reservoirs in India, which is 

higher than the rate proposed 

for the project. As stated in 

the report more detail study is 

required. Data may also be 

collected from the completed 

projects of the basin. 

(ii) New zero elevation after 

70 years may be evaluated 

(iii) Revised area elevation 

capacity table after 25 years 

may be incorporated. 

As per the terms of 

preparation of PFRs and as 

emphasized in the meetings 

dt. 4.2.03. Again vide our 

letter no. NH/DD/HYD/2656 

dt 17.7.03 we have stated this 

fact along with the letter 

received from IMD (ref. HS- 

DS(Dam)302/II dt.2 nd July 

2003. 

We are aware of the findings 

of CWC studies published in 

the Compendium on silting of 

reservoirs in India. As per that 

report, the sediment rate 

varies from 0.05658 to 0.2785 

Ham/Sq.km/year for Indus, 

Ganga and Brahmaputra 

basin. The silt rate adopted in 

the present study is based on 

silt rate of Ranganadi, 

Subansiri and Siang basin, 

which looks to be more site 

specific. 


sedimentation study showing 

the new zero elevation, 

revised area capacity curve 

etc. is not felt during PFR 

stage.

Gener 

al 

conducted by CEA 

sedimentation studies are 



The PFR must bring out the 

limitations of the hydrological 

studies carried out for the 

PFR and suggest 

improvements, specific 

recommendations for opening 

new hydrological stations, 

method of observations, data 

to be collected etc. may be 

given which will help us as 

guidance to the agency taking 

up the detail 

investigations/DPR must 

review the network in 

consultation with HSO, 

CWC. 

The hydrological studies for 

the PFR may be revised 

incorporating the above 

observations and resubmitted. 

The PFR has pointed out the 

limitation of the studies after 

each study and establishment 

of G&D site, rainfall stations 

etc. are also highlighted in the 

PFR.

REPLY OF CWC OBSERVATIONS RECEIVED VIDE LETTER 

Data & 

Consistency 

Checks 

Water 

availability 

studies 

NO.4/330/2003 HYD NE/357 DT. 14-11-2003 

CWC Observation Reply from NHPC 

Though site specific observed 

data is not available, the 

reliability of the data being 

transferred to the sites need to 

be established. 

The need for water availability 

studies based on observed data 

need not be emphasized. In the 

absence of site-specific data 

also, the reliability of the series 

transposed need to be 

established. 

The series of Munli dam site 

adopted by the NHPC for 

generating the yield series at 

the three dam sites are the old 

series supplied to Brahmaputra 

The discharge series 

considered for transfer 

have been taken from 

CWC report. The series 

had been derived after 

performing required 

studies to establish the 

reliability of the series. 

The discharge series 

considered for transfer 

have been taken from 

CWC report. The series 

had been derived after 

performing required 

studies to establish the 

reliability of the series. 

The series of Munli dam 

site adopted for generating 

the yield series at 

proposed dam site is taken 

from table 1.21A of latest

Board by CWC. The same has 

been pointed out to NHPC in 

the earlier comments. The 

series was revised by CWC 

after field inspection. NHPC 

has not collected and used the 

revised series. They have not 

submitted details of any studies 

done on their own to establish 

the reliability of the series 

used. Hence, the reliability of 

the series submitted by NHPC 

in the PFRs for power studies 

can not be commented upon 

and CWC has no further 

comments 

Design Flood Four to five years concurrent 

rainfall runoff data base can be 

utilized to calculate design 

floods by unit hydrograph 

approach. However, in the 


concurrent rainfall runoff data 

the design flood may be 

calculated using relevant sub 

zonal report of CWC taking 

report made available to 

us vide letter no. 

20/7/2002- 

Emb(E&NE)/177 dt. 27 th 

June 2003. The water 

availability series is based 

on 17 years of data (1985- 

2001), which is reasonable 

for PFR studies. The 

revised discharge series, if 

any, may kindly be sent to 

us. 

It is worth mentioning 

here that although 

deterministic approach of 

design flood computation 

has not been used directly 

in the present study for 

proposed projects, 

however, this approach 

has been used indirectly 

along with Emperical

into account the 

recommendations of 1993 

workshop and by collecting 

PMP/SPS values from IMD. 

Results may be compared 

before recommending the 

design floods. The design 

flood studies done by NHPC 

are too empirical to be relied 

upon. 

Sedimentation As per the terms of preparation 

of PFRs and as emphasized in 

the meetings conducted by 

CEA sedimentation studies are 



However such studies have not 

been given to HSO, CWC for 

vetting. 

The PFRs must bring out the 

various limitations of the 

hydrological studies carried out 

for the PFRs and suggest 

method, as the design 

flood at Munli dam site 

had been computed by 

deterministic approach 

only. 


sedimentation study 

showing the new zero 

elevation, revised area 

capacity curve etc. is not 

felt during PFR stage. 

Detailed sediment study 

need be done during 

feasibility stage with more 

observed data at the 

proposed site using a 

suitable method. 

The report points out the 

limitation of the studies 

after each study and 

establishment of G&D

improvements. Specific 

recommendation for opening 

new hydrological and hydro 

meteorological stations, 

method of observations, data to 

be collected etc. may be given, 

these will help as guidance to 

the agency undertaking 

detailed investigations. The 

agency taking up the detail 

investigations/DPRs must 

review the networks in 

consultation with HSO, CWC. 

site, rainfall stations etc. 

are also highlighted in the 

PFR, however, as 

suggested during different 

meetings held at CWC, the 

specific recommendations 

has been incorporated at 

the end of the chapter.

Elevation 

(metre) 

Reservoir 

Area (Ha) 

Reservoir 

Capacity 

(Mcum) 

1200 0.43 0.00 

1240 62.43 9.07 

1280 200.52 59.05 

1320 346.86 167.20 

-----> Elevation (m) 

1320 

1300 

1280 

1260 

1240 

1220 

1200 

1180 

200 

Plate 5.3 

EMINI H.E.PROJECT (DIBANG BASIN) 

RESERVOIR ELEVATION AREA CAPACITY CURVE 

180 

160 

Capacity Curve 

140 

120 

Area Curve 

Area (Ha) 

250 300 350 400 

80 

60 

40 

20 

0 

1320 

1300 

1280 

1260 

1240 

1220 

1200 

1180 

-----> Elevation (m)

Table 5.9 

EMINI H.E. PROJECT 

AVERAGE 10-DAILY DISCHARGE (CUMEC) AT DAM SITE 

PERIOD 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Average 

I 102.58 94.46 89.60 106.15 114.09 145.22 137.69 107.03 104.68 108.71 104.76 111.42 98.45 87.00 91.43 107.14 96.53 106.29 

JAN II 102.27 94.17 89.33 105.82 113.74 144.78 137.27 106.70 104.36 108.38 104.44 111.08 98.15 86.74 91.15 106.81 96.23 105.97 

III 98.64 90.83 86.16 102.07 109.71 139.64 132.40 102.92 100.66 104.54 100.74 107.14 94.67 83.66 87.92 103.02 92.82 102.21 

I 119.86 122.55 132.62 122.14 122.01 197.72 125.83 130.32 116.80 125.83 110.03 105.79 186.70 100.63 85.61 105.57 87.41 123.38 

FEB II 119.62 122.31 132.35 121.90 121.76 197.32 125.57 130.06 116.57 125.57 109.81 105.57 186.32 100.43 85.44 105.36 87.24 123.13 

III 130.57 133.50 144.46 118.27 132.90 215.38 137.07 126.19 127.23 137.07 119.85 102.43 203.37 109.62 93.26 102.22 95.22 131.09 

I 119.54 109.08 140.04 107.42 168.40 147.78 107.62 118.68 97.12 111.81 144.26 108.66 113.49 162.86 88.48 119.33 114.42 122.29 

MAR II 112.27 102.45 131.52 100.89 158.16 138.80 101.08 111.46 91.21 105.01 135.49 102.06 106.59 152.96 83.10 112.07 107.46 114.86 

III 133.38 121.71 156.25 119.86 187.90 164.89 120.08 132.42 108.36 124.75 160.96 121.24 126.63 181.72 98.72 133.14 127.67 136.45 

I 115.75 117.00 121.12 118.05 147.00 204.75 115.31 118.05 73.10 95.94 168.18 98.82 79.27 227.33 172.28 279.12 137.10 140.48 

APR II 180.68 182.63 189.05 184.27 229.46 319.60 179.99 184.27 114.10 149.76 262.52 154.25 123.73 354.84 268.92 435.69 214.00 219.28 

III 198.45 200.59 207.64 202.39 252.03 351.03 197.69 202.39 125.32 164.49 288.33 169.42 135.90 389.73 295.37 478.53 235.04 240.84 

I 282.13 372.54 362.07 292.59 423.09 274.26 277.42 292.59 242.72 225.49 242.26 262.26 470.78 305.47 348.19 325.30 171.83 304.18 

MAY II 245.20 323.78 314.68 254.29 367.71 238.36 241.11 254.29 210.94 195.97 210.55 227.93 409.16 265.48 302.61 282.72 149.34 264.36 

III 327.66 432.67 420.51 339.81 491.38 318.52 322.20 339.81 281.89 261.88 281.36 304.59 546.76 354.77 404.38 377.80 199.57 353.27 

I 444.02 478.11 646.36 479.15 841.14 553.83 479.15 479.15 342.01 407.11 642.07 291.92 421.40 443.81 368.99 597.86 243.94 480.00 

JUNE II 521.30 561.32 758.85 562.54 987.5 650.22 562.54 562.54 401.53 477.96 753.80 342.72 494.73 521.04 433.21 701.91 286.39 563.54 

III 520.85 560.84 758.20 562.05 986.7 649.66 562.05 562.05 401.19 477.55 753.16 342.43 494.31 520.60 432.84 701.31 286.14 563.05 

I 492.25 435.17 747.03 472.71 753.36 665.22 385.46 220.17 412.13 185.92 289.85 908.33 305.36 806.80 386.13 425.97 331.04 483.70 

JULY II 474.97 419.89 720.81 456.12 726.91 641.87 371.93 212.44 397.67 179.40 279.67 876.44 294.65 778.48 372.58 411.02 319.42 466.72 

III 440.77 389.66 668.91 423.27 674.57 595.65 345.15 197.14 369.03 166.48 259.53 813.33 273.43 722.42 345.75 381.42 296.42 433.11 

I 319.20 431.42 541.89 483.06 398.44 460.87 426.47 200.80 371.52 285.07 433.50 301.92 169.16 691.82 273.84 394.87 305.37 381.72 

AUG II 402.59 544.14 683.46 609.27 502.54 581.28 537.89 253.26 468.58 359.55 546.76 380.80 213.35 872.56 345.38 498.03 385.15 481.45 

III 372.48 503.43 632.33 563.69 464.94 537.79 497.65 234.31 433.52 332.65 505.85 352.31 197.39 807.28 319.54 460.77 356.34 445.43 

I 376.51 392.23 390.85 397.34 674.33 570.84 436.79 310.36 235.47 214.15 444.25 387.43 400.96 500.12 254.56 413.70 392.14 399.53 

SEP II 212.37 221.23 220.46 224.12 380.35 321.98 246.37 175.05 132.82 120.79 250.57 218.53 226.16 282.09 143.59 233.34 221.18 225.35 

III 159.95 166.63 166.04 168.80 286.47 242.50 185.56 131.85 100.03 90.97 188.72 164.59 170.34 212.46 108.14 175.75 166.59 169.73 

I 259.95 210.84 196.05 181.48 491.27 324.84 256.86 142.92 182.19 258.30 255.14 235.10 122.26 247.73 150.73 213.89 185.67 230.31 

OCT II 213.71 173.34 161.18 149.20 403.88 267.06 211.17 117.50 149.78 212.35 209.76 193.28 100.52 203.66 123.91 175.84 152.64 189.34 

III 234.52 190.22 176.87 163.72 443.21 293.06 231.74 128.94 164.37 233.03 230.19 212.10 110.30 223.49 135.98 192.96 167.51 207.78 

I 100.12 103.56 101.34 102.46 149.96 97.58 102.75 95.58 105.30 141.46 98.33 105.30 99.05 126.97 128.87 113.10 150.28 113.06 

NOV II 96.78 100.10 97.96 99.04 144.95 94.32 99.32 92.39 101.78 136.74 95.05 101.78 95.75 122.73 124.56 109.32 145.26 109.28 

III 91.22 94.35 92.33 93.35 136.62 88.90 93.62 87.08 95.93 128.88 89.59 95.93 90.25 115.68 117.41 103.04 136.92 103.01 

I 99.62 91.86 101.76 92.49 103.60 93.37 93.78 90.46 94.07 92.68 95.31 94.07 91.80 104.28 113.70 98.91 129.85 98.92 

DEC II 101.07 93.21 103.25 93.84 105.11 94.73 95.15 91.78 95.44 94.04 96.71 95.44 93.14 105.80 115.37 100.36 131.75 100.36 

III 93.32 86.05 95.33 86.64 97.05 87.47 87.85 84.74 88.12 86.82 89.29 88.12 86.00 97.69 106.51 92.66 121.64 92.66 

Average 233.78 246.33 299.41 246.12 358.12 308.64 243.54 192.44 198.82 189.64 254.18 244.29 209.17 318.63 208.29 271.38 192.32 247.95 

52

ANNEXURE 6.3 

Reply to the comments of CMDD Directorate, CWC issued vide CWC 

U.O. No. 20/2/2003/CMDD(E&NE)/229 dated 08.01.2004 

Emini H.E. Project (4x125MW) 

Sl. 

No. 

COMMENTS of CWC REPLY of NHPC 

1 The reports should indicate Scheme has primarily been 

alternative layouts and alternative conceived from CEA’s outline 

locations of project components scheme incorporating some 

examined during the preparation change in project features as 

of PFR to bring out their merits prima facie considered essential 

and demerits of each including based on site visits of NHPC 

that finally adopted in PFR. The officers & discussion with 

reasons for rejecting the particular CEA/CWC(as detailed in para 

alternative should also be 6.1 of PFR) Alternative layouts 

elucidated justifying the rejection. and site selection process can be 

optimised only when detailed 

topographical and geological 

investigations are carried in 

FR/DPR stage. 

2 The report should incorporate All the necessary drawings for 

following drawings: 

estimation of civil work 

a) Layout of scheme on quantities at pre-feasibility stage 

appropriate scale 

has been annexed in the PFR. 

b) Layout of river diversion 

arrangement 

c) Layout & typical L section and 

appropriate c/s of the water 

diversion/storage structure on 

appropriate scale 

Moreover, it should be noted that 

the drawings which has been 

provided in PFR are inadequate 

for estimation purposes for the 

dam structure as well as the 

diversion works. Necessary 

dimensioning should be done to 

make the drawings complete. 

3 Preliminary survey should be 

made to ensure the quality and 

quantity availability of 

construction materials. 

Already included vide para 

4.12, Chapter 4 on 

“Topographic and Geotechnical 

Aspects”

ANNEXURE 6.3 

4 The PFR should include some 

geophysical information about the 

dam location & which should be 

ensured by field study. 

5 The available contour map of 

Survey of India should be 

digitized and blown up to locate 

the different components of the 

project. 

6 Reasons for providing 2 nos. of 

upper level openings should be 

incorporated in PFR. 

7 For river diversion purposes nonmonsoon 

flood of 1600 cumecs 

has been considered. But the 

reason for considering this value 

has not been furnished. 

8 The levellised tarrif of the project 

at present day cost works out to be 

Rs3.13 per unit which seems to be 

on higher side. This aspect may be 

looked into. 

No geophysical investigation of 

site was possible due to 

inadequate time and logistics. 

1:50000 scale, SOI toposheet 

duly digitalized with various 

components marked on it are 

already included in PFR. 

The flood release has been 

considered partly through upper 

spillway and partly through 

lower spillway. Provision of 

upper spillway shall also 

facilitate reservoir operation 

/regulation. The arrangement 

can be reviewed at FR/DPR 

stage, if required. 

As indicated in PFR no G&D 

data is available of river Mathun 

as well as river Dri. As such 

value of Diversion Flood has 

been assumed. 

1.Project is located in very 

remote area and further cost has 

been worked out as per 

CWC/CEA guidelines for PFR 

preparation. 

2. Ater optimisation of project 

features during FR/DPR stage, 

efforts can be made to reduce 

the levellised tariff.

ANNEXURE 8.1 

Reply to the comments of HP&I Division, CEA vide letter no 

7/9(NHPC)/2003/HP&I/1287, November 2003 

Emini HE Project -500 MW (4x125 MW) 

Sl. 

COMMENTS OFCEA 

No. 

(SP&PA DIVISION) 

i) Emini HE Project across Mathun river (a tributary of 

Dibang river) in Dibang basin is among one of the 10 

schemes excluding the Dibang Multipurpose Project 

identified by CEA. 

ii) Location 

Emini HEP a run of river scheme in Dibang basin is 

proposed on river Mathun/Adzon (a major tributary of 

Dibang river) opposite of Maron village, downstream 

of confluence of Dri river with Mathun river, which is 

below 9 kms point on Anini-Mipi road from Anini in 

Dibang valley district of Arunachal Pradesh 

iii) Cost of the project 

The project is estimated to cost Rs. 2759.58crores 

(excluding IDC) at June, 2003 price level. The 

levellised tariff of project at present day cost and 

completed cost works out to be Rs313 paisa/kWh and 

363paise/kWh respectively at power house bus bars. 

iv) Power House 

Emini power house is located on the right bank of 

Mathun river just upstream of confluence of Dri river 

with Mathun river. Emini HEP which would be an 

underground power house, envisages installation of 4 

units of 125MW each. Power is proposed to be 

generates at 13.8kV and stepped up to 400kv through 

13 nos 47MVA 13.8/400kV single phase step up 

generator transformer. The generator step up 

transformers would be further connected to 400kV 

GIS located above the transformers. This is in order. 

v) Power Evacuation 

In order to evacuate 500MW of power from Emini 

HEP a 400kV D/C transmission line 50 kms in length 

from Emini HEP to Anini pooling point has been 

proposed as stated under para 8.3 of chapter 8. 

Accordingly, provision for two 400kV outgoing line 

REPLY of 

NHPC 

It is a statement. 




The single line 

diagram of the 

Switchyard is 

included in the 

final PFR. The

ANNEXURE 8.1 

bays have been kept in the Emini HEP switchyard. 

This is in order. Single line diagram of the switchyard 

has not been furnished. 

vi) Anini and Roing pooling points 

Further, it has been stated that power from nearby 

HEPs namely Amulin & Mihumdon including 

Agoline-375MW, for which PFRs has already been 

submitted would also be pooled at Anini pooling 

point. From Anini pooling point , this power would be 

pooled to pooling point planned near Roing/Dambuk 

at 400kV voltage level. The power from this pooling 

point shall be ultimately connected to national Grid 

through EHVAC/HVDC transmission line. The 

capacities of nearby HEPs namely Amulin & 

Mihumdon and their distances from Anini pooling 

point and Emini HEP has not been furnished in the 

absence of which it can not be stated whether power 

from Amulin HEP would be connected with Emini 

HEP or Mihumdon HEP power would be pooled at 

Anini HEP, as stated under para 8.3 on page 94 of 

PFR. A SLD showing the proposed transmission 

system up to Anini pooling point and Roing/Dambuk 

pooling point from Emini HEP, Amulin HEP, 

Mihumdon HEP & Agoline HEP and their 

interconnections/ distances has not been furnished. 

vii) Construction Power 

There is no grid power available near the project. 

Construction power of the order of 10-12MW for the 

project would be met by DG sets. 

viii) Cost of Transmission Works 

It has been stated under para 8.3 of chapter 8 that the 

cost of 400kV D/C transmission line from Emini HEP 

to Anini pooling point and other end equipments at 

Anini pooling point has been included in the cost of 

this project. The cost of electrical works including 

transmission works has been given as Rs 5723. 37 

crores under the abstract of cost of works of 

Appendix- I. The details of cost of transmission works 

may be furnished. However, if the works of 

transmission line is not to be executed by NHPC, the 

length of the line 

has been revised 

from 50km to 

10km 

The single line 

diagram showing 

the proposed 

transmission 

system up to 

Anini pooling 

point and 

Roing/Dambuk 

pooling point 

from Emini HEP, 

Amulin HEP. 

Mihumdon HEP 

& Agoline HEP 

and their 

interconnections 

/distances is 

enclosed. 


Details of cost of 

transmission 

work of Rs. 

14.36 crores has 

been separately 

enclosed in final 

PFR .

ANNEXURE 8.1 

cost estimates of transmission line works and cost of 

equipment at other end of the line be excluded from 

the cost estimates and only cost of switchyard and line 

bays at generating station end of the line be included 

in the cost estimate. 

ix) GENERAL COMMENTS 

(a) It may be stated that the benefits from these projects 

may not be fully absorbed from NE Region and needs 

to be exported to other regions. In long term 

perspective for evacuating bulk power from we may 

need to adopt a combination of HVDC/EHVAC 

transmission system which requires least transmission 

corridor, because of limited corridor in the chickenneck 

area taking into account the various power 

projects likely to be developed in NER in foreseeable 

future. We may need to plan an integrated 

transmission system from the pooling points in NER 

and phase out the implementation schedule suitably. 

(b) The transmission system as proposed for above 

schemes is tentative. The final transmission system 

would be determined by detailed power system 

studies on the basis of total power to be transmitted 

from NER, which may require a change in the voltage 

levels or configuration of the transmission system 

taking into consideration the mountainous terrain. 

thick forest area and right of way problems. 

(c) Beneficiaries States/ Regions along with their 

tentative shares from these projects have not been 

identified so far nor the time frame of the projects has 

been given 

(d) The possibility of establishing pooling point at 

DAMBUK in place of Roing pooling point as 

suggested by Chief Engineer NHPC may also be 

explored. 

Observations with regard to Switchyard Costs 

Cost Estimates for GIS 

In the pre feasibility report the following estimates at 

June 2003 PL for GIS switchyard have been 

indicated: 




The possibility of 

establishing 

pooling point at 

Dambuk instead 

of Roing would 

be explored at 

the DPR stage.

ANNEXURE 8.1 

S.no 

Rs 

1 

2 

3 

4 

5 

6 

7 

9 

Item Particulars 

400kV GIS for 7 

bays (3 Generator 

bays, 2 line bays, 

1Bus Coupler bay. 

XLPE cable 

400kV(7x300meters) 

with cable 

termination 

Spares 

Sub Total-1 

Custom Duty @ 

22% on item 1,2 and 

3 

Sub Total-2 

Central Sales Tax @ 

4% on Sub Total 2 

Transportation and 

insurance @ 3% of 

Sub Total-2 

Erection & 

Commissioning @ 

8% excluding spares. 

Sub total-3 

Establishment 

Contingencies other 

charges @ 8% of sub 

Total-3 

Total for GIS 

Qty 

7 

bays 

2.1km 

Rate 

Rs 

600 

lakh 

per 

bay 

184 

lakhs 

per 

km 

Total Rs 

(Lakhs) 

4200.00 

386.40 

91.73 

4678.13 

1029.188 

5707.318 

228.29 

171.2 

447.63 

6554.438 

524.36 

7078.798 

Cost estimate has 

been revised as 

per the CEA 

comments and 

enclosed in final 

PFR.

ANNEXURE 8.1 

Our observations with regard to the 

cost estimates for switchyard are as 

under: 

1. Since both GIS and XLPE cable 

are imported equipment Sales Tax 

is not applicable and hence needs to 

be deleted. 

2.freight and insurance has been 

taken on the basic cost of equipment 

plus custom duty component. 

Freight and insurance should be 

only on the basic cost of equipment. 

3.Contingencies Establishment and 

other charges @ 8% have been 

adopted . It is noted that these 

charges have also been taken on 

custom duty component. Custom 

duty component should be excluded 

from Establishment charges. Instead 

a handling charge of 2% on custom 

duty component may be taken. 

Transmission line and bay extension works at 

pooling point 400kV Anini 

In the pre feasibility report an estimate of Rs 5723.37 

lakh towards 50km 400kV D/C line from Emini to 

Anini and for bay extension works has been 

estimated. From the details enclosed it is noted that 

for estimates the project authorities have taken rate of 

Rs 70lakhs per km for 400kV line and Rs2.00lakh per 

bay towards bay extension works. Over and above 

this Excise duty @ 16%, CST @ 4%, Spares@ 2%, 

Transportation and Insurance @ 3% , Erection and 

Commissioning@ 8%, Establishment @ 8% have 

been taken. The per km cost of transmission line in 

plain including Excise Duty and CST is of the order 

of 55 lakhs per km and in hilly terrain (non snow 

bound) the rate is about 25% higher. The estimates for 

transmission line therefore appear to be on higher 

side. The rate of 70 lakh per km for 400klV D/C line 

Cost of 

Transmission 

line has been 

taken as 50lakh 

per km excluding 

Excise Duty and 

CST and Cost 

estimate has been 

revised 

accordingly.

ANNEXURE 8.1 

should include Excise Duty and CST or alternatively a 

rate of Rs 60Lakh per km may be taken It needs to be 

noted that detailed breakup of the cost of 

transmission line may be included the time of 

preparation of feasibility report and also detailed 

break up of estimates for bay extension works. 

COMMENTS OF CEA (HP&I DIVISION) 

A- GENERAL COMMENTS 

1. An Executive Summary may also be incorporated in 

the PFR as per format given at Annex -IV. 

2. It may be ensured that the Initial Environmental 

studies incorporated in the PFR are as per scope of 

work for PFR. 

3. The Financial Parameters may be taken as per 

guidelines sent vide our Lr. No. 7/9/HPI-2003/1118- 

1123, dated 21st October, 2003. 

4. The Cost Estimates may be prepared taking into 

account the Guidelines sent vide our Lr. No. 

7/9/HP&I/2003/1163-1172, dated 24.10.2003. 

5. NHPC may indicate recommendations for further 

studies required wherever necessary in the relevant 

chapters of PFRs for consideration during Feasibility 

Report/DPR stage. 

6. It is presumed that geological inputs of the area are as 

per information supplied by GSI. The report of GSI 

may also be included in the PFR. 

Executive 

summary as per 

the prescribed 

format has been 

incorporated in 

the final PFR. 

Initial 

Environmental 

studies have been 

carried out by 

NRSA which has 

been enclosed in 

final PFR. 

Guidelines have 

been followed in 

final PFR. 

Cost estimates 

have been 

prepared as per 

the guidelines 

Recommendation 

for further 

studies have been 

incorporated in 

the relevant 

chapter of final 

PFR. 

The report of 

GSI has been 

included in final 

PFR.

ANNEXURE 8.1 

7. It may be ensured that the Installed Capacities & 

assessment of power benefits takes into account 

various comments and advise given in this regard. 

8. It may be ensured that the water availability adopted 

for power potential studies is approved by CWC. 

9. The power evacuation arrangements considered in the 

PFR should take into account views and suggestions 

of SP&PA Division of CEA. 

B- POWER POTENTIAL STUDIES 

vii. In the year wise summary table, the load factor of 

operation during monsoon and lean flow period may 

be indicated for all years. 

Comments of the 

various agency 

have been taken 

into 

consideration. 

The water 

availability 

adopted for 

power potential 

studies has been 

examined by 

CWC & their 

comments and 

reply of NHPC 

have been 

appended in the 

final PFR. 

For power 

evacuation 

arrangement 

views and 

suggestion of 

SP&PA division 

has been 

considered while 

preparing of final 

PFR. 

The load factor 

of operation 

during monsoon 

& lean flow 

period for Emini 

H.E Project is 

indicated in the 

Reservoir 

operation 

report(Table 7.3) 

& is enclosed for 

inclusion in the 

final PFR.

space for page 

Table 5(H) 

EMINI H.E. PROJECT 

AVERAGE 10-DAILY DISCHARGE (CUMEC) AT DAM SITE 

PERIOD 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 Average 

I 102.58 94.46 89.60 106.15 114.09 145.22 137.69 107.03 104.68 108.71 104.76 111.42 98.45 87.00 91.43 107.14 96.53 106.29 

JAN II 102.27 94.17 89.33 105.82 113.74 144.78 137.27 106.70 104.36 108.38 104.44 111.08 98.15 86.74 91.15 106.81 96.23 105.97 

III 98.64 90.83 86.16 102.07 109.71 139.64 132.40 102.92 100.66 104.54 100.74 107.14 94.67 83.66 87.92 103.02 92.82 102.21 

I 119.86 122.55 132.62 122.14 122.01 197.72 125.83 130.32 116.80 125.83 110.03 105.79 186.70 100.63 85.61 105.57 87.41 123.38 

FEB II 119.62 122.31 132.35 121.90 121.76 197.32 125.57 130.06 116.57 125.57 109.81 105.57 186.32 100.43 85.44 105.36 87.24 123.13 

III 130.57 133.50 144.46 118.27 132.90 215.38 137.07 126.19 127.23 137.07 119.85 102.43 203.37 109.62 93.26 102.22 95.22 131.09 

I 119.54 109.08 140.04 107.42 168.40 147.78 107.62 118.68 97.12 111.81 144.26 108.66 113.49 162.86 88.48 119.33 114.42 122.29 

MAR II 112.27 102.45 131.52 100.89 158.16 138.80 101.08 111.46 91.21 105.01 135.49 102.06 106.59 152.96 83.10 112.07 107.46 114.86 

III 133.38 121.71 156.25 119.86 187.90 164.89 120.08 132.42 108.36 124.75 160.96 121.24 126.63 181.72 98.72 133.14 127.67 136.45 

I 115.75 117.00 121.12 118.05 147.00 204.75 115.31 118.05 73.10 95.94 168.18 98.82 79.27 227.33 172.28 279.12 137.10 140.48 

APR II 180.68 182.63 189.05 184.27 229.46 319.60 179.99 184.27 114.10 149.76 262.52 154.25 123.73 354.84 268.92 435.69 214.00 219.28 

III 198.45 200.59 207.64 202.39 252.03 351.03 197.69 202.39 125.32 164.49 288.33 169.42 135.90 389.73 295.37 478.53 235.04 240.84 

I 282.13 372.54 362.07 292.59 423.09 274.26 277.42 292.59 242.72 225.49 242.26 262.26 470.78 305.47 348.19 325.30 171.83 304.18 

MAY II 245.20 323.78 314.68 254.29 367.71 238.36 241.11 254.29 210.94 195.97 210.55 227.93 409.16 265.48 302.61 282.72 149.34 264.36 

III 327.66 432.67 420.51 339.81 491.38 318.52 322.20 339.81 281.89 261.88 281.36 304.59 546.76 354.77 404.38 377.80 199.57 353.27 

I 444.02 478.11 646.36 479.15 841.14 553.83 479.15 479.15 342.01 407.11 642.07 291.92 421.40 443.81 368.99 597.86 243.94 480.00 

JUNE 

II 521.30 561.32 758.85 562.54 987.5 650.22 562.54 562.54 401.53 477.96 753.80 342.72 494.73 521.04 433.21 701.91 286.39 563.54 

III 520.85 560.84 758.20 562.05 986.7 649.66 562.05 562.05 401.19 477.55 753.16 342.43 494.31 520.60 432.84 701.31 286.14 563.05 

I 492.25 435.17 747.03 472.71 753.36 665.22 385.46 220.17 412.13 185.92 289.85 908.33 305.36 806.80 386.13 425.97 331.04 483.70 

JULY II 474.97 419.89 720.81 456.12 726.91 641.87 371.93 212.44 397.67 179.40 279.67 876.44 294.65 778.48 372.58 411.02 319.42 466.72 

III 440.77 389.66 668.91 423.27 674.57 595.65 345.15 197.14 369.03 166.48 259.53 813.33 273.43 722.42 345.75 381.42 296.42 433.11 

I 319.20 431.42 541.89 483.06 398.44 460.87 426.47 200.80 371.52 285.07 433.50 301.92 169.16 691.82 273.84 394.87 305.37 381.72 

AUG II 402.59 544.14 683.46 609.27 502.54 581.28 537.89 253.26 468.58 359.55 546.76 380.80 213.35 872.56 345.38 498.03 385.15 481.45 

III 372.48 503.43 632.33 563.69 464.94 537.79 497.65 234.31 433.52 332.65 505.85 352.31 197.39 807.28 319.54 460.77 356.34 445.43 

I 376.51 392.23 390.85 397.34 674.33 570.84 436.79 310.36 235.47 214.15 444.25 387.43 400.96 500.12 254.56 413.70 392.14 399.53 

SEP II 212.37 221.23 220.46 224.12 380.35 321.98 246.37 175.05 132.82 120.79 250.57 218.53 226.16 282.09 143.59 233.34 221.18 225.35 

III 159.95 166.63 166.04 168.80 286.47 242.50 185.56 131.85 100.03 90.97 188.72 164.59 170.34 212.46 108.14 175.75 166.59 169.73 

I 259.95 210.84 196.05 181.48 491.27 324.84 256.86 142.92 182.19 258.30 255.14 235.10 122.26 247.73 150.73 213.89 185.67 230.31 

OCT II 213.71 173.34 161.18 149.20 403.88 267.06 211.17 117.50 149.78 212.35 209.76 193.28 100.52 203.66 123.91 175.84 152.64 189.34 

III 234.52 190.22 176.87 163.72 443.21 293.06 231.74 128.94 164.37 233.03 230.19 212.10 110.30 223.49 135.98 192.96 167.51 207.78 

I 100.12 103.56 101.34 102.46 149.96 97.58 102.75 95.58 105.30 141.46 98.33 105.30 99.05 126.97 128.87 113.10 150.28 113.06 

NOV II 96.78 100.10 97.96 99.04 144.95 94.32 99.32 92.39 101.78 136.74 95.05 101.78 95.75 122.73 124.56 109.32 145.26 109.28 

III 91.22 94.35 92.33 93.35 136.62 88.90 93.62 87.08 95.93 128.88 89.59 95.93 90.25 115.68 117.41 103.04 136.92 103.01 

I 99.62 91.86 101.76 92.49 103.60 93.37 93.78 90.46 94.07 92.68 95.31 94.07 91.80 104.28 113.70 98.91 129.85 98.92 

DEC II 101.07 93.21 103.25 93.84 105.11 94.73 95.15 91.78 95.44 94.04 96.71 95.44 93.14 105.80 115.37 100.36 131.75 100.36 

III 93.32 86.05 95.33 86.64 97.05 87.47 87.85 84.74 88.12 86.82 89.29 88.12 86.00 97.69 106.51 92.66 121.64 92.66 

Average 233.78 246.33 299.41 246.12 358.12 308.64 243.54 192.44 198.82 189.64 254.18 244.29 209.17 318.63 208.29 271.38 192.32 247.95 

Annexure-I

5980.56 

4784.45 

Annexure-I

space for page 

Elevation 

(metre) 

Reservoir 

Area (ha) 

Reservoir 

Capacity 

(Mcum) 

1180 0.00 0.00 0 1290 

1200 0.43 0.03 3400 1290 

1240 62.43 9.10 

1280 200.52 59.08 

1320 346.86 167.23 


1320 

1300 

1280 

1260 

1240 

1220 

1200 

1180 

200 

EMINI H.E.PROJECT (DIBANG BASIN) 

RESERVOIR ELEVATION AREA CAPACITY CURVE 

180 

160 

Capacity Curve 

140 

120 

Area Curve 

Area (Ha) 

250 300 350 400 

80 

60 

40 

20 

0 

1320 

1300 

1280 

1260 

1240 

1220 

1200 

1180 


Figure-I

Emini

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