Dibbin HE 100MW

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100 MW DIBBIN H.E. PROJECTARUNACHAL PRADESH

Preliminary Feasibility Report

July 2004

Government of India

Ministry of PowerCentral Electricity Authority

Consultant :


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50,000 MW HYDROELECTRIC INITIATIVES

100 MW DIBBIN H.E. PROJECTARUNACHAL PRADESH

Preliminary Feasibility Report

July 2004

North Eastern Electric Power Corporation Ltd.

(A Government of India Enterprise)

Government of India

Ministry of PowerCentral Electricity Authority

Consultant :


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FOREWORD ......................................................................................................... ..................................................... 1

SALIENT FEATURES .......................................................................................... .................................................... 2CHAPTER I ......................................................................................... ...........................EXECUTIVE SUMMARY

1.1 INTRODUCTION........... ............................................................................................................ ................. 5

1.2 SCOPE OF WORK................ ..................................................................................................... ................. 6

1.3 HYDROLOGY ......................................................................................................... .................................... 6

1.4 POWER POTENTIAL STUDIES...................................................................................... ........................ 6

1.5 POWER EVACUATION ASPECTS..... ................................................................................................. ... 7

1.6 ENVIRONMENTAL ASPECTS................................................................................................. ............... 7

1.8 FINANCIAL ASPECTS............................................................................................... ............................... 8

1.9 CONCLUSIONS ........................................................................................ .................................................. 8

CHAPTER II................................................................................................................PROJECT BACKGROUND

2.1 ARUNACHAL PRADESH .......................................................................................................... ............. 10

2.2 THE RIVER SYSTEM................................................................................................. ............................. 11

2.3 THE PROJECT...................... .................................................................................................... ................ 12

2.4 POWER SCENARIO ................................................................................................... ............................. 12

2.5 NECESSITY OF THE PROJECT ............................................................................................ ............... 14

2.6 INFRASTRUCTURE ................................................................................................... ............................. 15

2.7 PROSPECTS AND PROBLEMS................... .......................................................................................... 16

CHAPTER III ........................................................................................ ........................................PROJECT AREA

3.1 DESCRIPTION OF PROJECT INCLUDING RIVER SYSTEM.............. ......................................... 19

3.2 SOCIO ECONOMIC AND OTHER ASPECTS ................................................................................. 22

CHAPTER IV.....................................................................................TOPOGRAPHICAL & GEOTECHNICAL

4.1 INTRODUCTION........... .............................................................................................. ............................. 29

4.2 LOCATION .................................................................................................. .............................................. 29

4.3 GEOMORPHOLOGY/PHYSIOGRAPHY ........................................................................................... . 29

4.4 REGIONAL GEOLOGY OF EAST KAMENG DISTRICT ............................................................... 30

4.5 TECTONICS ................................................................................................... ........................................... 32

4.6 NEOTECTONICS, SEISMICITY & EARTHQUAKES ...................................................................... 34

4.7 SEISMICITY......... ........................................................................................................ ............................. 34

4.8 GEOTECHNICAL APPRAISAL ............................................................................................. ............... 34

4.9 CONSTRUCTION MATERIALS ........................................................................................................... 35

4.10 CONCLUSIONS AND RECOMMENDATIONS .................................................................................. 36

Table of Contents


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CHAPTER V ............................................................................................... ....................................... HYDROLOGY

5.1 GENERAL .................................................................................................... .............................................. 39

5.2 BASIN CHARACTERISTICS ...................................................................................................... ........... 395.3 METEOROLOGICAL PROPERTIES OF KAMENG BASIN........................................................... 40

5.4 PROJECT PROPOSAL .......................................................................................... .................................. 40

5.5 WATER AVAILABILITY STUDIES .............................................................................................. ....... 40

5.6 METHODOLOGY................................................................ ..................................................................... 43

5.7 DESIGN FLOOD STUDIES .......................................................................................... ............................. 44

CHAPTER VI...................................................................................... CONCEPTUAL LAYOUT & PLANNING

6.1 INTRODUCTION........... .............................................................................................. ............................. 52

6.2 RIVER DIVERSION WORK........................................................................................................ ........... 52

6.3 DIVERSION DAM................................................................................... .................................................. 54

6.4 DESILTING TANK...................................................................................................... ............................. 57

6.5 INTAKE CHANNEL AND POWER INTAKE.................................... .................................................. 58

6.6 HEAD RACE TUNNEL .......................................................................................... .................................. 58

6.7 SURGE SHAFT.................................... .................................................................................................. .... 59

6.8 PENSTOCKS........................................................... ................................................................................... 60

6.9 POWER HOUSE..................................................... ................................................................................... 60

6.10 ELECTRO-MECHANICAL EQUIPMENT ......................................................................................... . 61

6.11 TAIL RACE CHANNEL ............................................................................................. ............................. 61

6.12 FURTHER STUDIES ................................................................................................... ............................. 61

CHAPTER VII......................................................................................................................POWER POTENTIAL

7.1 INTRODUCTION........... ............................................................................................................ ............... 64

7.2 FIXATION OF FULL RESERVOIR LEVEL ............................................................................ ........... 64

7.3 FIXATION OF MINIMUM DRAW DOWN LEVEL........................................................................... 64

7.4 FIXATION OF TAIL WATER LEVEL .................................................................................. ............... 65

7.5 DISCHARGE DATA .................................................................................................... ............................. 65

7.6 OPERATING HEAD................................................................................... .............................................. 66

7.7 EFFICIENCY .................................................................................................... ......................................... 66

7.8 INSTALLED CAPACITY ........................................................................................... ............................. 66

7.9 ENERGY GENERATION ........................................................................................... ............................. 67

7.10 UNIT SIZE.................................................................................................. ................................................ 67

7.11 SUMMARY OF RESULTS ......................................................................................... ............................. 67

7.12 FURTHER STUDIES ................................................................................................... ............................. 68


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CHAPTER VIII ................................................................................... ............................. POWER EVACUATION

8.1 APPRAISAL OF EXISTING POWER EVACUATION FACILITIES.............................................. 70

8.2 PROPOSED EVACUATION SYSTEM TO NEAREST FACILITY................................................. . 70

CHAPTER IX................................................................................................................ENVIRONMENT ASPECT9.1 GENERAL INFORMATION............................................................................................. ...................... 74

9.2 SUBMERGENCE AREA...................................................................................... .................................... 74

9.3 RIVER SYSTEM .......................................................................................................... ............................. 75

9.4 SEISMICITY......... ........................................................................................................ ............................. 75

9.5 EXISTING LANDUSE/LANDCOVER AROUND THE PROPOSED DAM SITE .......................... 76

9.6 FOREST TYPES IN THE VICINITY OF PROJECT AREA ............................................................. 77

9.7 FAUNAL ELEMENTS AROUND THE PROJECT AREA................................................................. 79

9.8 EXISTENCE OF ANY PROTECTED AREA/ARCHAEOLOGICAL SITES..... ............................. 79

9.9 HUMAN SETTLEMENT ............................................................................................ ............................. 80

9.10 RELIEF AND REHABILITATION.................................................................................. ...................... 80

9.11 RECOMMENDATIONS AND MITIGATIVE MEAUSRES............................................................... 80

CHAPTER X ............................................................................................... ............................ INFRASTRUCTURE

10.1 THE PROJECT........ ..................................................................................................... ............................. 81

10.2 ACCESS ROADS .......................................................................................................... ............................. 82

10.3 IMPROVEMENT OF EXISTING STATE HIGHWAY ROAD.......................................................... 82

10.4 CONSTRUCTION OF NEW ROADS ................................................................................................... . 83

10.5 CONSTRUCTION FACILITIES................................................................................ ............................. 83

10.6 PROJECT ROADS ......................................................................................... ........................................... 83

10.7 PROJECT HEADQUARTERS, OFFICES AND COLONIES ............................................................ 84

10.8 EXPLOSIVE MAGAZINE ........................................................................................................ ............... 85

10.9 SCHOOL, PRIMARY HEALTH CARE, BANK, PETROL PUMP................................................... 85

10.10 CONSTRUCTION POWER........................ ............................................................................................. 86

10.11 TELE-COMMUNICATION.............................................................. ....................................................... 87

CHAPTER XI.............................................................................CONSTRUCTION PLANNING & SCHEDULE

11.1 INTRODUCTION................. ...................................................................................................... ............... 90

11.2 BASIS OF STUDY ........................................................................................................ ............................. 9011.3 MAJOR COMPONENT .............................................................................................. ............................. 90

11.4 MATERIAL SOURCES......................................... ................................................................................... 91

11.5 BASIC CONSIDERATIONS........................................................................................................... ......... 91

11.6 CONSTRUCTION CONTRACTS........................................................................................... ................ 91

11.7 SCHEDULE OF WORKING HOURS................. ................................................................................... 92

11.8 CONSTRUCTION PERIOD ..................................................................................................... ............... 93

11.9 STAGE I ACTIVITIES................................................................................... .......................................... 93


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11.10 STAGE II ACTIVITIES .............................................................................................. ............................. 93

11.11 STAGE III ACTIVITIES........ ................................................................................................... ............... 94

11.12 RIVER DIVERSION WORK........................................................................................................ ........... 94

11.13 DIVERSION DAM................................................................................................. .................................... 9411.14 HEAD RACE TUNNEL .............................................................................................. .............................. 95

11.15 SURGE SHAFT............................... .......................................................................................................... . 95

11.17 PENSTOCKS............................................................... ............................................................................... 96

11.18 POWER HOUSE.................................................. ...................................................................................... 96

11.19 ELECTRO-MECHANICAL WORKS.................................................................................................... 96

11.20 SWITCHYARD...................................................................................................... .................................... 96

CHAPTER XII.............................................................................................................................COST ESTIMATE

12.1 INTRODUCTION................. ...................................................................................................... ............... 98

12.2 COST ESTIMATE................ ................................................................................................. .................... 98

CHAPTER XIII .......................................................................................... ...............ECONOMIC EVALUATION

13.1 GENERAL .................................................................................................. .............................................. 100

13.2 PROJECT BENEFITS ................................................................................................. ........................... 100

13.3 INPUTS DATA AND ASSUMPTIONS..................................................... ............................................ 100

13.4 ESTIMATED COST AND PHASING .................................................................................................. 101

13.5 DEPRECIATION........................................ ............................................................................................. 101

13.6 LOAN AMORTIZATION ........................................................................................... ........................... 102

13.7 WORKING CAPITAL REQUIREMENTS.................................................................................... ...... 102

13.8 ENERGY SALE PRICE.............................................................. ............................................................ 102

13.9 ESTIMATES OF WORKING RESULTS ............................................................................................ 103

13.10 INTERNAL RATE OF RETURN (IRR).................................................................................... ........... 103

13.11 DEBT SERVICE COVERAGE RATIO (DSCR)................................................................................. 103

13.12 PAYBACK PERIOD ............................................................................................... ................................ 104

13.13 CONCLUSION................................... ...................................................................................................... 104


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CHAPTER I ......................................................................................... ...........................EXECUTIVE SUMMARY

1.1 A vicinity map

1.2 A conceptual layout map

CHAPTER IV.....................................................................................TOPOGRAPHICAL & GEOTECHNICAL

4.1 Geological Map of East Kameng District

CHAPTER V ............................................................................................... ....................................... HYDROLOGY

ANNEXURES

5.1 Ten Daily Flow Series-Bichom

5.2 Ten Daily Flow Series - Dibbin

5.3 Calculation of Equivalent Slope5.4 Details of SUG Parameters

5.5 Calculation of Effective Rainfall Values

5.6 Details of Rainfall Excess5.7 Convolution of Design Flood Hydrograph

5.8 Copy of Comments on Hydrology Chapter and their replies

FIGURES

5.1 Synthetic Unit Hydrograph

5.2 100 year return period flood

PLATES

I Index Map

II Isohyetal MapIII Project Component Layout

IV Raingauge and Discharge Sites

CHAPTER VI...................................................................................... CONCEPTUAL LAYOUT & PLANNING

Drawing No. : NP-PFR-DB-601 Conceptual Layout

Drawing No. : NP-PFR-DB-602 Upstream view of Dam

Drawing No. : NP-PFR-DB-603 Details of Desilting Chamber

Drawing No. : NP-PFR-DB-604 Details of Intake ChannelDrawing No. : NP-PFR-DB-605 Details of Water Conductor system

Drawing No. : NP-PFR-DB-606 Cross Section of Tunnel

Drawing No. : NP-PFR-DB-607 Details of Surge ShaftDrawing No. : NP-PFR-DB-608 Cross Section of Turbine Hall

Drawing No. : NP-PFR-DB-609 Cross Section of Power House

Drawing No. : NP-PFR-DB-610 Cross Section of Coffer Dams

Annexure 6.1 Copy of the comments received from CWC and replies

CHAPTER VII......................................................................................................................POWER POTENTIAL

Annexure 7.1 Copy of Comments and their repliesTables 7.1-7.19 Power Potential Studies

List of Annexures


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CHAPTER VIII ................................................................................... ............................. POWER EVACUATION

Annexure 8.1 Power Map of North Eastern Region

Annexure 8.2 Single Line Diagram

Annexure 8.3 Power Evacuation systemAnnexure 8.4 Proposed Switchyard Layout

Annexure 8.5 Copy of the comments received on Power Evacuation

CHAPTER IX................................................................................................................ENVIRONMENT ASPECT

Annexure 9.1 Drainage Map of Tizu River of the Bishum Chu river of Dibbin Project

Annexure 9.2 Map showing Submergence Area due to reservoir of proposed projectAnnexure 9.3 Seismic zoning map of North East and Eastern Part of India showing

location of the proposed Dibbin HE scheme

Annexure 9.4 IRS-ID LISS III Scene of 7 km Radius area of the proposed project

Annexure 9.5 IRS-ID PAN Scene of 7 km Radius area of the proposed projectAnnexure 9.6 Landuse/Landcover Map of Submergence Area

CHAPTER XI.............................................................................CONSTRUCTION PLANNING & SCHEDULE

11.1 Construction Schedule

CHAPTER XII.............................................................................................................................COST ESTIMATE

12.1 Cost Abstract

CHAPTER XIII .......................................................................................... ...............ECONOMIC EVALUATION

Annexure 13.1 Inputs and Assumptions

Annexure 13.1A Year Wise Allocation of Project Cost

Annexure 13.2 General Breakdown of Scheme Cost

Annexure 13.3 Calculation of Interest During Construction (IDC)

Annexure 13.4 Calculation Depreciation including Advance Against Deprecation

Annexure 13.5 Loan AmortizationAnnexure 13.6 Calculation of Working Capital Requirements

Annexure 13.7 Calculation of Sale Price of Energy

Annexure 13.8 Estimates of Working ResultsAnnexure 13.9 Internal Rate of Return (Project)

Annexure 13.10 Debt Services Coverage Ratio

Annexure 13.11 Payback Period

List of Annexures & Drawings


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PMs 50,000 MW initiative 1

FOREWORDWith the objective of accelerating capacity addition and developing untapped hydro power potential

in India in a phased and systematic manner, the Central Electricity Authority (CEA) had conductedRanking Studies, based on inter-se-priority for their development, so as to have a shelf of prioritized

schemes. A noble initiative towards development of such potential has been initiated by the Honble

Prime Minister of India, on May 24, 2003 at Vigyan Bhawan, by launching the 50,000 MW hydro

electric initiative, to be taken up under the aegis of the Ministry of Power.

North Eastern Electric Power Corporation Ltd. (NEEPCO) has been entrusted by CEA to prepare

the Pre-Feasibility Reports for 18 hydro electric projects with an installed capacity of 4915 MW in

the States of Arunachal Pradesh and Nagaland.

In the first two stages of this ambitious programme, the Design & Engineering group ofNEEPCOhas prepared the Pre-Feasibility Reports of 12 projects with an installed capacity of 4100 MW. ThePre-Feasibility Reports of these twelve Hydro Electric Projects were submitted to CEA. Pre-

Feasibility studies of additional three projects in the Kameng river valley have now been taken up

by NEEPCO. The enclosed Pre-Feasibility report of Dibbin Hydro Electric Project (100 MW) has

been estimated at a cost of 371.52Crores (including IDC) at September 2003 price level, with a first

year tariff of Rs.2.53/kWh.

I am highly indebted and thankful to Honble Union Minister of Power; Honble Union Minister of

State for Power; Shri R.V. Shahi, Secretary (Power), Government of India; and Shri H.L. Bajaj,

Chairman, CEA for the opportunity given to NEEPCO for undertaking the task and being a part of

the Mission 2012: Power for all. I also thank Messrs Premier Mott MacDonald for rendering

necessary support service to NEEPCO in preparation of the reports.

New Delhi S.C. SharmaJuly 2004 Chairman & Managing Director


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SALIENT FEATURES

LOCATION

State Arunachal Pradesh

River Bichom, tributary of Kameng riverLocation of dam

Longitude 92 31' 16" E

Latitude 27 27' 00" N

Access to the project By road from Tezpur (Assam) via Balipara Bhalukpongand Rupa

Nearest Rail head Bhalukpong

Airport Tezpur

HYDROLOGY

Catchment area at Dam Site 607 sq.kmMaximum average discharge at dam site 143.54 cumecs

Minimum average discharge at dam site 7.58 cumecs

DIVERSION DAM

Type Gated Dam

Full reservoir level (FRL) 1185 m

Minimum draw down level (MDDL) 1179 m

Deepest River Bed Level 1160 m

Total length at top of dam 143 m

SPILLWAY

Type Gated spillway

Width of spillway block 78 m

No. of bays 5 bays

Crest level of spillway 1171 m

Spillway gates 5 nos. 11.1m x 14 m

Energy dissipation system Stilling basin

Design flood 3740

SUBMERGENCE

Villages submerged Nil

Area submerged 6.4 Ha

RESERVOIR

Gross storage 0.26 Mcum

Live storage 0.21 Mcum


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INTAKE

Invert level of intake 1171 m

Intake gate size 5 m x 5 m

Trash rack Semi circularHEAD RACE TUNNEL

Size 5.0 m

Shape Modified horse shoe type section

Velocity 4.03 m/sec

Length 4430 m

SURGE SHAFT

Type Simple

Diameter 13.7 m

Height 60.33 m

Bottom Elevation 1135.67 m

POWER HOUSE

Installed Capacity 100 MW

Units 2 x 50 MW

Type of Turbine Francis

Design head 150 m

Annual Design Energy (90% dependable

year)335.72 GWh

Annual energy in 90% year on 95%

machine availability

332.00 GWh

Minimum TWL 1020 m

FINANCIAL ASPECT

Total Project Cost Rs. 371.52 crores

Tariff for 1st year

After considering 12% free power

Without considering 12% free power

Rs. 2.53 per kWh

Rs. 2.23 per kWh

Levelised tariff for 35 years

After considering 12% free power

Without considering 12% free power

Rs. 2.04 per kWh

Rs. 1.79 per kWhCost per MW installed Rs. 3.71 Crores

CONSTRUCTION PERIOD 4 years (excluding 30 months of Pre-constructionactivities)


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CHAPTER-I

Executive Summary


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1.1 INTRODUCTION

1.1.1 Dibbin HE Project is proposed on river Bichom, in its upper reaches, which is a

tributary of Kameng river in west District. The installed capacity of the project would

be 100 MW (2x50 MW) and the annual energy generation from the project in a 90%

dependable year is assessed as 335.72 MU.The levelised tariff at May 2004 price level

would be Rs. 2.53 per kWh with 12% free power and Rs 2.23 per kWh without 12%

free power. The scheme envisages construction of a gated dam 27 m high located just

downstream of the confluence of Ditya Bung river with Bichom river with its co-

ordinates at 9231'16"E and 2727'00"N to divert the river water Bichom into the water

conductor system.

1.1.2 The water conductor system shall comprise an intake channel, a surface desilting

chamber, a head race tunnel, a surge shaft, pressure shaft and penstocks.

1.1.3 The dam site of Dibbin H.E. Project is located in the upper reach of river Bichom

where the river bed level is EL 1160 m just downstream of confluence of Bichom Chu

with Difya Ru with its co-ordinates at 9231' 16" E and 2727'00" N. The dam site is

approachable through PWD road from Rupa upto Nafra and then a foot path of about

15 km upto Dibbin village. Power house site is located near Nachibin villagewith its

co-ordinates at 27024'36"N and 92

031'12"E. Nafra is connected to Rupa town by a

PWD road. UptoRupa town the road from Balipara is maintained by Border Roads

Task Force (BRTF) of the Government of India. Balipara, in turn is connected to

Tezpur on the National Highway No. 52. Tezpur which is the nearest airport for Dibbin

H.E. Project, is about 25 km from Balipara.

1.2 SCOPE OF THE PROJECT

1.2.1 DibbinHE Project envisages construction of:

A gated dam 27 m high located just downstream of the confluence of Ditya Bung

river with Bichom river.The length of the dam will be 143 mconsisting of 78 m of

overflow section and 32 m of non-overflow section on the left bank and 33 m on the

right bank. The reservoir upstream of dam will have a live storage of 0.21 Mcum to

enable operation of one unit for peaking for 2.0 hours during morning as well as

evening hours of non-monsoon period.


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A spillway with 5 bays of 11.1 m clear opening each and 4.5 m wide piers

controlled by 5 nos. radial gates each of size 11.1 m x 14 m.

An energy dissipation arrangement of stilling basin type of length 97 m.

A desilting tank 100 m long and 135 m wide divided into two compartments. A head race tunnel 5.0 m diameter and 4.43 km long.

A surge shaft at the outlet of the head race tunnel 13.7 m diameter and 60.33 m

height.

Two pressure shafts 3 m diameter and 50 m long and thereafter 2 surface penstocks

of 3.0 m diameter and 103 m length.

A surface power house located on the left bank of Bichom having installation of 2

units of 50 MW each with Francis type turbine designed for a net head of 150 m .

A short length of tail race channel to discharge the tail waters of Dibbin HE project

into Ditch Bru.

A vicinity map showing 13 projects in Kameng basin is placed at Annexure 1.1 and a

conceptual layout map at Annexure 1.2.

1.3 HYDROLOGY

The catchment area at Dibbin HE project dam site is a 607 sq. km. Dibbin project falls

in Bichom sub-basin. Within Dibbin project area, there is no hydro meteorological

network. However a G&D site is available at Bichom dam site and at this G&D site

Bichom flow series is available for 13 years. Catchment area of Bichom river at

Bichom G&D site is 2277 sq km. Therefore flow series for Dibbin HE project has been

arrived at on proportionate catchment area basis and is used for the PFR purpose of this

hydro electric project. The Bichom series has been transformed into 10 daily discharge

series for Dibbin dam site on catchment area proportionate basis and taking into

account rainfall variability 100 year design flood has been considered for design of

diversion structure. The probable 100 year flood works out to 3740 cumecs. The design

flood values have been estimated by Hydro-meteorological approach. The study needs

to be reviewed at the DPR stage when site specific short term rainfall-runoff data as

well as discharge data would become available.

1.4 POWER POTENTIAL STUDIES

1.4.1 The annual energy generation in 90% and 50% dependable years has been computed

using 10-daily discharge series generated for Dibbin HE project diversion dam site.


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Annual energies were calculated for different installed capacities and the optimum

capacity was determined as 100 MW for this scheme. The annual energy generation in

a 90% dependable year would be 335.72 MU as detailed below:

Particulars 90% Dependable Year

Annual Generation

Annual Energy Generation (GWh) 335.72

Annual Load Factor (%) 38.32

Generation during Lean Flow Season (Nov-Apr)

Power output (MW) 19.95

Lean Load Factor (%) 19.95

1.4.2 A live storage of 0.21 Mcum has been provided in the pondage to enable operation of

two unit of the power house for peaking for 2.0 hours during morning hours and 2.0

hours during evening hours during non-monsoon period. The power station will operate

as a base load station during the monsoon period.

1.5 POWER EVACUATION

The power generated at Dibbin HE project will be evacuated through LILO

arrangement of already approved 220 kV double circuit lines from Utung to the

switchyard of Kameng HE project (under construction). This power will be transmitted

to the Bhalukpong pooling point on 400 kV double circuit lines, which in turn, will be

transmitted to the National Grid.

1.6 ENVIRONMENTAL ASPECTS

1.6.1 The predominant landuse in the vicinity of project area is forest. The dense forests

constitute more than 48% of the total area and area under open forest and scrubs cover

about 16% and 13% area, respectively. Agricultural and settlements landuse/landcover

accounts for than 16% of the study area. Shifting cultivation also covers more than 7%

of the project area.

1.6.2 The proposed diversion structure is 27 m high, the proposed reservoir would lead to

submergence of only 6.4 ha of land, which is comprised mainly of barren waste land

and degraded forests on the left bank slopes and open forest on the right bank hence it

would not lead to the submergence of any human habitation.


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1.7 ESTIMATES OF THE COST

The project is estimated to cost Rs. 371.52 crores including IDC at May 2004 price

level. 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 216.22 crores

E&M works 104.62 crores

Sub-Total (Generation) 320.84 crores

Transmission works Not included

Total (Hard Cost) 320.84 crores

Interest During Construction 50.68 crores

Grand Total 371.52 crores

1.8 FINANCIAL ASPECT

Dibbin HE project, with an estimated cost of Rs. 371.52 crores (including IDC of 50.68

crores) and design energy of 355.72 GWh in a 90% dependable year is proposed to be

completed in a period of 4 years (excluding 30 months of pre-construction activities).

The tariff has been worked out considering a debt-equity ratio of 70:30, 16% return on

equity, and annual interest rate on loan at 10%. The tariff at the power house busbars

for the first year has been worked out to Rs. 2.53/kWh (with 12% free power) and Rs.

2.23/kWh (without free power) and levelised tariff for 35 years have been worked outto Rs. 2.04 / kWh (with 12% free power) and Rs 1.79/kWh (without 12% free power).

1.9 CONCLUSION

Dibbin Hydro Electric Project involves simple civil works and could be completed in

4 years (excluding 30 months of pre-construction activities). The project would afford

design energy of 335.72 GWh at the power house busbars in a 90% dependable year.

The cost per MW installed work out Rs. 3.71 crores. The Preliminary Feasibility Report

indicates that the scheme merit consideration for taking up detailed Survey,

Investigation and preparation of DPR.


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CHAPTER - II

Project Background


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2.1 ARUNACHAL PRADESH

2.1.1 Arunachal Pradesh the Land of the Rising Sun with an area of 83,743 sq. km. is the

largest state in the North eastern region sharing international boundaries with Bhutan inthe west, China in the north and Myanmar in the east. The states of Assam and

Nagaland flank its Southern and South eastern borders. Forest covers about 82% area of

the State and numerous turbulent streams, roaring rivers, deep gorges, lofty mountains,

snow clad peaks and rich diversity of flora and fauna characterize the landscape. The

climate varies from sub-tropical in the south to temperate and alpine in the north with

large areas experiencing snowfalls during winter. The heights of the mountain peaks

vary, the highest peak being Kangte (7090 above MSL) in West Kameng District. The

major rivers that drain the area with their numerous tributaries are Siang, Kameng,

Subansiri, Kamla, Lohit, Dibang, Noa - Dehing and Tirap. The State is administratively

divided into 15 districts. The state capital is at Itanagar at an altitude of 530 m above

MSL. It is named after the brick fort built by Ahom King of Assam in the 14th

century.

2.1.2 A wide variety of altitudinal gradients and climatic conditions have given rise to varied

eco-systems which form the habitat of diverse plant wealth and wild life in the State.

Due to its high species diversity, the region has been identified as a global hot spot for

bio-diversity conservation. The pre-dominant forest types occurring in the state are

Tropical Semi Evergreen, Tropical Wet Evergreen, Sub-tropical, Pine, Temperate and

Sub-Alpine / Alpine Forests. There are also degraded forests and grass lands.


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2.1.3 The State harbors a rich variety of wildlife which includes four major cats namely tiger,

leopard clouded leopard and snow leopard. The region is home to seven species of

primates, large mammals like elephants, gaur and wild buffalo. High altitude animals

include musk deer, bharal, Himalayan black bear, red panda etc. The State animal is

Mithun (Bos Frontails) existing both in wild and semi-domesticated form. This animal

has religious significance and intimate relation with socio-cultural life of the people.

The bird fauna of the State include more than 500 species. This is the richest state for

pheasants with some species found at different altitudes. The rivers contain a wealth of

fishes. The State also abounds in a variety of reptiles and amphibians.

2.1.4 The forests of the State cover about 82% of the States geographical area of which 960

sq.km. have been set aside as protected area comprising two national parks (Namdapa

and Mouling) and nine wildlife sanctuaries.

2.1.5 The population of Arunachal Pradesh is 1091117 (2001 census). The people are of

Mongoloid stock with heritage of arts and crafts, enchanting folk songs with their own

distinct and diverse culture, dialects and lifestyles. There are 20 major tribes in the

State namely Adi, Nyishi, Apatani, Bugun, Galo, Hrusso, Koro, Meyor, Monpa, Tagin,

Mishmi, Sajolang, Sartang, Tai Khamti, Yobin, Singpho, Sherduken, Khamba,

Tangshang and Memba. The State has a literacy rate of 54.74%.

2.2 THE RIVER SYSTEM

2.2.1 The Kameng river which is also known as Jia - Bhareli in its lower reaches originates in

the upper Himalayan ranges at an elevation of about 4800 m. The river has a total

length of about 198 km. and drains about 12,500 sq. km. of catchment area into the

Brahmaputra river about 10 km upstream of Tezpur town in Assam. During the course

of its long journey it is joined by several major tributaries namely Bichom, Digien,

Tenga, Pachuk and Pakke which originate at high altitudes. Map of Kameng River

Basin is attached as Annexure 8.2.

2.2.2 The rainfall in the basin is quite high and varies from about 1000 mm in higher reaches

to about 5750 mm in the foot hills spread over 8-9 months excepting the dry days in

winter. The upper regions also receive precipitation from snow clad mountains which

contribute to the river flow during lean period. On this account fairly high perennial

discharge continues to be available in the river all the year around. Such a favorable

river discharge pattern and the fact that a total fall of more than 3000 m is available in


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the river system make it very attractive for developing a series of hydro-electric power

stations on the main river and its tributaries. A 600 MW hydro electric project is

currently being constructed by NEEPCO which will bring waters from Bichom and

Tenga rivers through a tunnel to a power station at Kimi with tail race discharging into

Kameng river.

2.3 THE PROJECT

2.3.1 Dibbin H.E. Project is located in the upper reach of river Bichom which is a major

tributary of Kameng river. It envisages construction of a gated dam 21m high near

village Dibbin where the river bed level is at EL 1160 m and is situated in West

Kameng District. The waters of river Bichom will be diverted through a tunnel to a

surface power house on the right bank of Bichom river near Nachibin village. Installed

capacity planned for the power house is 100 MW.

2.3.2 The proposed reservoir would lead to submergence of 6.4 ha of land which is mainly

under barren waste land and degraded forests / scrub. Very little submergence area is

under dense forest.

2.3.3 The human settlements in the project area are scattered.

2.3.4 There are no monuments of archeological or national importance which would be

affected by project activities directly or indirectly.

2.4 POWER SCENARIO

2.4.1 The per capita power consumption of Arunachal Pradesh is below 100 kWh as

compared to the national average of 373 kWh. The State plans to harness its enormous

natural resources like forests and hydro power and exploit its mineral wealth to usher in

an era of economic development and raise the per capita electricity consumption to 500

kWh by the end of Eleventh Five year Plan period i.e. 2012. The States generating

capacity was only 32.03 MW hydro and 28.63 MW diesel till now which has increased

substantially with the completion of 405 MW Ranganadi hydro power project. 600 MW

Kameng hydro project and 1600 MW Subansiri Project are under construction and

these projects will provide electricity not only to Arunachal Pradesh and other states in

the north-eastern region but also to other power starved regions of the country.


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Energy and Peak Load Shortages

7.5

10.78.6

19.1

14.4

3.1

7.87.9

-0.7 -1.6

13

-1.6

-5

0

5

10

15

20

25

NR WR SR ER NERs Overall

Supply Shortages Peak Deficit

2.4.2 The power scenario has therefore to be viewed in the national perspective. According to

50000 MW Hydropower Initiative of the Ministry of Power, the energy requirement of

the country in 2002-03 was 5,45,674 MkWh of which only 4,97,589 MkWh were

available, leaving a shortfall of 8.8%. While the peaking requirement was 81,492 MW,

a peak of only 71,547 MW could be met leaving a shortage of 12.2%. The regionwise

shortage of energy and peaking capacity is depicted in the following graph:

Source: Blue print for Power Sector Development MoP 2001

2.4.3 Against the present installed generating capacity of 1,07,973 MW, the share of hydro,

with 26,910 MW capacity, is only 25%. Thermal (coal, gas and diesel) accounts for the

maximum share of 71% with 76,607 MW. Nuclear capacity is about 2.5% with 2720

MW and wind 1,736 MW i.e. 1.6%. This is graphically depicted below:

Source : 50000 MW Hydro-electric

Initiative May 2003

Shares in Installed Capacity - March, 2003

58%

3% 2%

1%

11%

25%

Hydro, 26910 MW

Gas, 11633 MW

Diesel, 1173 MW

Wind, 1736 MW

Nuclear, 2720 MW

Coal, 63801 MW


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2.4.4 Most of the regions of the country are suffering from power shortages leading to

irregular and unreliable supply. The problem becomes acute during peak hours. Based

on the projections made in the 16th

Electric Power Survey, an additional generating

capacity of over 100,000 MW needs to be added to ensure Power on Demand by

2012. This, in effect, means doubling the existing capacity which has been created in

the last half a century in the next ten years. Not only has the capacity to be added but

also the present hydro-thermal imbalance of 25:75 has to be corrected and brought to

40:60 to meet the peak load requirements, achieve frequency and voltage stability and

provide system operating flexibility under changing seasonal and diurnal load pattern.

For achieving a 40:60 hydro thermal ratio in an installed capacity of around 200,000

MW the total requirement of hydro capacity will be 80,000 MW which means that

53,000 MW additional hydro capacity has to be created in the next 10 years.

2.5 NECESSITY OF THE PROJECT

2.5.1 According to categorization of schemes by CEA the Category A schemes in different

river basins all over India total to 7800 MW as shown in the table below:

River Basin-wise Summary of Categorisation of the Schemes Ranked by CEA

Category A Category B Category C TotalS.No. River System

Nos MW Nos MW Nos MW Nos MW

1. Indus 11 4088 51 8811 17 6080 79 189792. Ganga 20 2023 54 9616 1 600 75 12239

3. Central Indian 3 283 9 1425 1 186 13 1894

4. East Flowing 11 1412 26 6469 2 88 39 7969

5. West Flowing 1 35 10 958 14 1508 25 2501

6. Brahmaputra 52 7800 97 42574 19 12954 168 63328

Source: 50000 MW Hydro-electric Initiative May 2003

2.5.2 The entire Category A schemes needs to be taken up for completion by 2012. Out of

the above, Arunachal Pradesh has 31 schemes with a total installed capacity of 5047

MW against which NEEPCO has been allotted 15 schemes with a total installed

capacity of 3220 MW. There is therefore scope for development of all these projects

subject to their technical and economic feasibility. NEEPCO has already carried out

pre-feasibility studies for six projects totaling to 2460 MW and has now taken up

similar studies for six more projects as per directive of the Government of India.


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Construction of 100 MW Dibbin H.E. Project on high priority is justified on the basis

of pre-feasibility studies carried out by NEEPCO.

2.6 INFRASTRUCTURE

2.6.1 Power Evacuation

A 400 kV sub-station for evacuation of power from Rangnadi project has been

constructed. Power will be transported to 400 kV Balipara substation already

constructed by PGCIL from where it will be taken to other regions. A 400 kV

substation is also planned at Khuppi for transmission of 600 MW power from Kameng

hydro electric project power to Balipara and onwards to other regions. A power map

of North-eastern region and Sikkim prepared by PGCI is attached as Annexure 8.1 in

Chapter VIII. The State government has also taken steps to construct a state grid at 132

kV covering all the districts and to electrify all villages up to the inter-state and

international borders. The power evacuation facilities will need to be upgraded and

augmented substantially as new projects are taken up.

A number of major hydro electric power stations are planned in the Kameng Valley. As

only a small portion of the power generated at these stations will be utilized in

Arunachal Pradesh itself, it will be appropriate to interconnect these stations and take

the pooled power to Bhalukpong sub-station for being exported to other regions of thecountry. Scheme for evacuation of power from Dibbin HE Project is given in Chapter

VIII Power Evacuation.

Communications

2.6.2 The State has a network of about 15,000 km of roads including border roads for access

to all areas of the State.

2.6.3 The dam site of Dibbin H.E. Project is located in the upper reach of river Bichom

where the river bed level is EL 1160 m just downstream of confluence of Bichom Chu

with Difya Ru with its co-ordinates at 9231' 16" E and 2727'00" N. The dam site is

approachable through PWD road from Rupa upto Nafra and then a foot path of about

15Km upto Dibbin village. Power house site is located near Nachibin village. Nafra is

connected to Rupa town by a PWD road. UptoRupa town the road from Balipara is

maintained by Border Roads Task Force (BRTF) of the Government of India. Balipara,

in turn is connected to Tezpur on the National Highway No. 52. Tezpur which is the

nearest airport for Dibbin H.E. Project, is about 25 km from Balipara.


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2.6.4 The state highway from Rupa to Nafra is metalled and black topped, but considerable

portion of the road needs improvement. Beyond Nafra, a new road of about 15 Km is

required to be constructed for movement of mechanized equipment and transport of

heavy electro-mechanical equipment for Dibbin H.E. Project right upto power house

site as well as to dam site.

2.6.5 Telecommunication facilities in the State comprise 94 telephone exchanges, 70 of

which have STD facilities. In addition 695 PCOs have STD facilities. Internet

connections are also available.

2.6.6 Central assistance is being provided for infrastructural development in the State and is

being utilized for accelerated development.

2.7 PROSPECTS AND PROBLEMS

2.7.1 Arunachal Pradesh is very rich in natural resources. The state has a strong base for

mainstream and downstream industries based on:

(a) Abundant resources of hydro power potential, biodiversity of rich forests,

tourism, horticulture and floriculture.

(b) Access to the large markets in south-east Asian countries if traditional trade

routes are re-established and developed.

2.7.2 Rich Natural Resources

Rich natural resources of the state can be converted into real goods if limitations, which

the State is confronted with, are overcome. A study commissioned by the State

Government has listed various limitations to the development. The important ones are:

(i) Gestation period of the projects is much higher as compared to other States of

the country.

(ii) Prolonged rainy season leading to less effective working time per year for

building infrastructure.

(iii) Higher cost due to long distance of transportation.

(iv) Inadequate industrial infrastructure, lack of industrial experience and non-

availability of technical expertise.

(v) Reluctance of investors.

(vi) Prohibitive cost of laying power line for longer distances.

(vii) Inadequate investment in exploration of untapped natural resources.


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2.7.3 The State is fully seized of these problems and has taken various steps to encourage

investment. The industrial policy encourages establishment of industries in the private

and cooperative sectors for the accelerated development of the State. The incentives

include:

Central capital investment subsidy scheme;

Transport subsidy scheme;

Central interest subsidy scheme;

Comprehensive insurance scheme, etc.

2.7.4 Incentives have also been announced by the State government to encourage private

sector participation (both Indian and foreign) in the development of hydro-electric / gas

based power projects. The state is thus poised for accelerated development and is an

attractive destination for investment.


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CHAPTER - III

Project Area


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3.1 DESCRIPTION OF PROJECT INCLUDING RIVER SYSTEM

River System

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

Siang, the Lohit and the Tirap. All these are fed by snow from the Himalayas and

countless rivers and rivulets. Kameng river basin covers almost the entire West

Kameng and East Kameng districts as also a part of Lower Subansiri district. A number

of tributaries like Bichom, Tenga, Pachi, Papu and Pachuk contribute to River Kameng

before it joins River Brahmaputra about 10 kms upstream of Tezpur. The river acquires

the name Jia-Bhareli in the last 50 km before it joins River Brahmaputra.

3.1.2 The Bishum Chu originates in the glaciated areas in the Greater Himalayan range at an

altitude of about 5,650m. It drains a number of glacial lakes in the upper reaches.

Bishum Chu flows generally in the southward direction and is joined by a number of

streams both on left and right banks up to the proposed project site. Kachho Bung is the

first major left bank tributary of Bishum Chu. Further downstream it is joined by

another stream named Sama Bung. Chang Dimung Chu and Mijung Chu are main right

bank tributaries of Bishum Chu. Immediately upstream of the proposed dam site

Bishum Chu is joined by Deyang Bung on its left bank. The catchment area of Bishum

Chu up to the proposed dam site is 607 sq km. Total length of the river from its origin

up to dam site is about 44 km.

BED SLOPE OF BICHOM RIVER

0

1000

2000

3000

4000

5000

6000

1 2 3 4 5 6 7 8 9 10 11 12

Distance (KM)

Elevation(M)


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3.1.3 Bhareli/Kameng River in its total route of about 200 km carries the discharge of all its

major and minor tributaries and drains a total catchment of about 8,540 sq.km. upto

Bhareli II proposed dam site. The catchment area extends across international border

and some of the tributaries have origin in Bhutan/ Tibet. About 20% of the total

catchment area in the upper reaches remains snow bound throughout the year and keeps

contributing to the river flow during the lean months in the form of glacial melt. The

remaining catchment area of about 80% is rain fed. The basin receives varying amounts

of rainfall, ranging from a minimum of 1000 mm in the upper reaches to about 5700

mm in the foot hills annually and the average rainfall is fairly high. The river flow in

the Kameng river system is, therefore, quite large and the variation in river flows in

different months is not as large as in the case of purely rain fed rivers. Comparatively

less variation in flow and high discharge and bed slope make the river suitable for

setting up a number of hydro electric schemes.

3.1.4 The catchment is covered by thick forest which gives the advantage of maximum

runoff of the rain water into the river and also ensures minimum inflow of silt. The

Kameng river system passes through a thick forest cover having rich bio-diversity. The

area has a number of species of flora and fauna and abundant aquatic life in the river.

3.1.5 The Kameng in its upper reaches generally flows in north-south direction. Taking large

turns in its course, Kameng River flows in narrow valleys upto Seppa town, the head

quarters of East Kameng District after which it widens out. In the reach upto Seppa

town, the river is joined by a number of tributaries viz Para, Pachi, Pache, Pachuk etc.

About 18 km downstream of Seppa town, the river is joined by one of its major

tributaries, the Bichom. The combined river then takes a turn and flows in the westerly

direction. About 35 km downstream of the confluence of Bichom, the Kameng river

takes a U bend and starts flowing in the easterly direction. Downstream of confluence

of Dikhu Nala, the Kameng River takes a north south course and finally meets River

Brahmaputra about 10 kms. upstream of Tezpur.

3.1.6 The Kameng basin spreads over an area of 12500 sq.km. The tributaries/ sub-tributaries

drain catchment areas ranging from 4600 sq.km. to 280 sq.km. The drop in elevation

from the origin to the confluence with the main river is from about 4800 m to about 120

m. The major tributaries of Kameng River, namely Bichom, Digien, Tenga, Pakke,


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3.1.12 Dibbin Hydro Electric project is envisaged as a run of the river scheme with 27 m high

dam. The dam is expected to have the deepest foundation at EL 1160 m. The crest level

of the dam is kept at EL 1171 m. The length of the dam at top would be around 143 m.

In order to provide a little storage to meet the diurnal variation in the demand of water

of turbines in the power station during lean months, the dam would be provided with

five numbers of radial gates of size 11.1 m x 14 m.

3.1.13 The water conductor system would comprise a desilting basin to eliminate silt particles

above 200 microns size, a tunnel intake, 4.43km long head race tunnel of 5 m diameter,

a surge shaft and two penstock of 3 m diameter 143 m long. A surface power house

with an installed capacity of 2 x 50 MW is proposed on the right bank of Bichom river

near Nachibin village.

3.2 SOCIO ECONOMIC AND OTHER ASPECTS

3.2.1 On 15th August 1947 when India became an independent nation, North East Frontier

Agency (NEFA) became a Union Territory and acquired the name of Arunachal

Pradesh. In 1975 it acquired a legislature and finally on 20th

February 1987 it became

the 25th

State of the Union of India. The State has an area of 83,743 sq. km and a

population of 1, 09,117 (according to 2001 census) giving an average density of just 13

people per sq. km.

The State has been developing steadily through Five Year Plans with emphasis on

development of infrastructure such as roads and bridges, buildings, educational

institutions, hospitals and health care units etc. The economy of the State is largely

agrarian. Other areas important to the economy of the state are horticulture, forest and

small and medium scale industries.

3.2.2 The state of Arunachal Pradesh is bestowed with rich natural resources which include

rich forest area, mineral resources like dolomite, limestone, graphite, marble etc.Development of hydro projects will give ample scope for development of agro- based

industries and industries with basic mineral resources. Other socio-economic benefits to

the people, from these projects will include employment to workers, development of

communications, markets and other benefits consequent to large scale construction

activity.


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3.2.3 The Gross State Domestic Product of the State during 2000-01 as per quick estimates was

estimated as follows:

(Rs. in lakhs)

Particulars At current prices At constant prices

Primary Sector 65,186 39,062

Secondary Sector 36,796 24,919

Tertiary Sector 76,318 46,598

GSDP 178,300 1,10,579

The per capita income during 2000-01 at current prices was Rs. 16,343 and at constant

prices Rs. 10,136. The share of primary sector has come down from 46.19% in 1990-91

to 35.33% in 2000-01 while that of tertiary (services) sector has increased from 32.25%

to 42.14% during the same period. The share of the secondary sector (manufacturing,

construction etc.) has remained almost the same. Transport, tourism and public

administration has contributed to the increase in the tertiary sector.

3.2.4 Arunachal Pradesh is largely rural with 94 percent of its population living in villages

scattered all over the state. The indigenous people are tribes with rich and glorious

heritage of arts and crafts. The State has 20 major tribes and a number of sub-tribes

having their own ethos, dialects and cultural identities which present a unique scenario

of unity in diversity. Most of the tribal communities are ethnically similar having

derived from an original common stock but their geographical isolation from each other

has brought amongst them certain distinctive characteristics in language, dress and

customs.

3.2.5 The total literacy in the State has risen from 41.57% in 1991 to 54.74% in 2001. The

State has 12 towns and 3649 villages. As against the decadal (1991-2001) growth rate

of 21.34% at the national level, population of the State has grown by 26.21%. The sex

ratio of Arunachal Pradesh at 901 female to 1000 males is lower than the national

average of 933.

Tribes

3.2.6 There are about 20 major tribes with a number of sub-tribes in Arunachal Pradesh.

Larger tribes are Adi, Akas, Apatanis, Buguns, Singhpos, Membas, Mishmis, Mijis,

Thongsas, Hrusso, Monpas, Nyishi, Sherdukpens, Tagins, Khamti, Yobin, Wanchos,

Noctes.


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Cultural Group

3.2.7 The people of Arunachal Pradesh may be divided into three cultural groups on the basis

of their socio-religious activities.

(i) The Monpas and Sherkukpens of Tawang and West Kameng districts follow the

lamaistic tradition of Mahayana Buddhism. These communities have richly

decorated Buddhist temples called Gompas. They practice terrace cultivation

and also breed herds of Yak and mountain sheep. Membas and Khambas living

in northern borders are culturally similar. Khamtis and Singphos inhabiting the

eastern part of the State are Buddhists of Hinayana sect.

(ii) The Adis, Akas, Apatinis, Bangnis, Nishis, Mishmis, Mijis, Thongsas, etc.

worship Sun and Moon Gods (Donyi-Polo and Abo-Tani), and are the original

ancestors for most tribes. They traditionally practice Jhumming or shifting

cultivation and paddy-cum-pisiculture.

(iii) Noctes and Wanchos adjoining Nagaland practice elementary form of

Vaishnavism

Social Structure

3.2.8 The tribals of Arunachal Pradesh have highly ordered and organized system of

functioning in their village. All matters relating to the community as a whole are

decided at the village level. The traditional village Panchayat of an Adi Village islocally known as Kebang. It is a judicio-administrative body consisting of mature

and influential elders and looks after the administration of justice in the society by

settling all matters of dispute. Similar self-governing institutions exist among other

tribes. They are variously called as Jong among the Sherdukpens, Mel among the

Akas, Buliang among the Apatanis etc.

Economic Development

3.2.9 Arunachal Pradesh could be justifiably called the power house of India with a total

untapped hydro power potential of 49,126 MW from 89 identified schemes. The State

and Central Governments encourage private sector participation (both Indian and

Foreign) in the development of hydro-electric power projects. National Hydro-electric

Power Corporation (NHPC) a Government of India enterprise and North East Electric

Power Corporation (NEEPCO) also a Government of India enterprise for power

development in the north-eastern region have been entrusted with the task of

developing hydro as well as gas based power projects. NEEPCO has recently


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completed 405 MW Ranganadi hydro-electric power project and NHPC has taken up

the construction of 1600 MW Subansiri project. NEEPCO is developing 600 MW

Kameng Hydro-electric power project from the waters of Bichom / Tenga rivers which

are tributaries of Kameng river. In addition 31 schemes with power potential of 5047

MW which have been identified as Category A schemes are being investigated in

Arunachal Pradesh. Out of these, 15 schemes with a power potential of 3945 MW are

being investigated by NEEPCO. All these schemes are on Kameng river system. All

these projects are planned to be completed by the year 2012. The state is therefore

poised to become a major exporter of power to other regions of the country.

3.2.10 The state has also prepared its own State development plan and proposes to increase the

present per capita consumption of about 100 kWh of electricity to 500 kWh by the time

the above mentioned hydro projects are completed. The State is already in the process

of creating 132 kV State power grid with distribution centres in every district. 400 kV

lines and switchyards will also be constructed for evacuation of power from hydro

electric projects to various distribution centres and also outside the Sate for which the

Power Grid Corporation of India is preparing a plan of action. The State Government

has decided to electrify all its villages by conventional or non-conventional energy by

the year 2012 and provide electricity to all.

3.2.11 Dibbin Hydro Electric Project will have an installation of 2 x 50 MW to generate

335.72 MU of electricity in a 90% dependable year. The project would provide benefits

of free power to Arunachal Pradesh amounting to 12% power generated. The

development of project will enhance the quality of life of the people living in and

around the project by way of development of roads and communication, availability of

reliable, dependable, un-interrupted power for development of small/medium

industries, development of tourism etc.

3.2.12 The State has rich tourism potential with high snow clad mountains, numerous

turbulent streams, roaring rivers, deep gorges, endless variety of flora and fauna and

places of scenic beauty. Being conscious of the importance of tourism as a vehicle of

economic development the State has recognized tourism as a thrust area and has opened

up a number of tourist circuits including the Tawang monastery on the Indo-China

border.


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v) Ornaments are mostly made of beads. Notches and Wanchos weave them into

attractive designs. Silver ornaments are a specialty of the Mishmis.

vi) Wood carving unique and artistic articles are produced in Tirap, Upper and

West Siang, Lohit and Tawang.

3.3 Dibbin Hydro Electric Project will thus provide the much needed infrastructure to the

State for its all round development and improvement in the quality of life of its people.

The project will also be a valuable source of hydro power to the rest of the country.


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Chapter IV

Topographical and Geotechnical Aspects


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subdivided into Inner Lesser Himalaya and Outer Lesser Himalaya, the former lying to

the south of the Higher Himalaya comprises mainly of Paleoproterozoic - The Bomdila

Group and Ziro Gneises and Mesoproterozoic - The Dirang Formation. The Outer

Lesser Himalaya is the zone that lies immediately to the north of the Sub-Himalaya. It

is made-up of Early Permian rocks Lower Gondwana Group. It is characterised by

dendritic drainage with broad V-shaped valleys at places filled by Quaternary deposits

forming terraces.

4.3.3 The Higher Himalaya is a narrow zone that lies between the Lesser Himalaya in the

south and the Tethys Himalaya in the north. It is chiefly made up the Archaean-

Paleoproterozoic sequence constituting the Central Crystalline and Mesoproterozoic -

the Dar formation, which forms the basement for the Phaenerozoic succession of theTethys Himalaya, this physiographic region is also referred to as the Himadari or

Greater Himalaya (Singh, 1971). The southern limit is defined by the MCT while in the

north imperceptibly passes into the Tethys Himalaya. This zone is characterised by

highly rugged topography with some snow-bound high peaks.

4.3.4 Drainage : The Kameng River (also known as Bhareli) is one of the principal

tributaries of the mighty Brahmaputra River of the district draining about 9,860 km2

of

western Arunchal Himalaya through its network of smaller streams such as Tenga,

Bichom, Papu, Pacha, Pachi, Para, Wacha rivers. It originates from the southeastern

slopes of Higher Himalaya and drains the Dafla Hill in the Lesser Himalaya, and cuts

deep gorge through the Siwalik rocks of the Sub-Himalaya. It enters the Brahmaputra

Plain near Bhalukpong. The Kameng (Bhareli) River and its tributaries are transverse

rivers excepting small stretches where it is subsequent to the structural weak planes

such as MBF.

4.4 REGIONAL GEOLOGY OF EAST KAMENG DISTRICT

4.4.1 The generalised stratigraphy as worked out by Kumar (1997) in the East Kameng

district, Arunachal Pradesh, is given in Table 1. There is no record of Archaean rocks

from this part. The Sela Group is oldest poly-phase deformed sequence of

metasediments, which is tenatively considered to be of Early Paleoproterozoic age. Its

southern limit is defined by a major tectonic plane-the Main Central Thrust (MCT),

which separates it from the Dirang Formation (Mesoproterozoic). The Bomdila Group

comprises low to medium-grade metasediments, which includes quartzite with


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Age Group Formation Member Lithology

A Oligomictic conglomerate

containing grit to cobble sizerounded to subrounded clasts of

quartzite, pinkish to greyish white

coloured.

Cambrian Deed Biotite granite (500+19Ma)

Granite gneiss

Mesoproterozoic Dirang Low-grade metasediments

comprising garnet-muscovite-biotite schist, phyllite, sericite

quartzite, calc-silicate, tremolite-

actinolite marble.

Mafic sills & dykes

Ziro Geneisses (Biotite grantie

gneiss 1914+25Ma & Tourmaline

bearing leuco-granite 1676+122Ma) Ultramafic dykes and sills.

Niumi Crystalline limestone, dolostone/

dolomite, quartzite & green

phyllite, carbonaceous phyllite,

chlorite/ actinoalite-hornblendephyllite with thin beds of marble.

Chilliepam

Kabak Dolomite, with black phyllite.

Oligomictic conglomerate with

clasts of quartzite.

Jameri Quartzite with thin bands of

phyllite.

Tenga

Along Mafic metavolcanics, drab greenchlorite phyllite.

Bomdila

Khetabari Quartzite schistose to massive,

garnet mica sachist, para-

amphibolite

Schistose quartzite, acid tuff,phyllite, carbonaceous &

graphitic phyllite, marble & calc-silicate.

Galensiniak Kyantite-sillimanite+stanurolite

gneiss and schist, quartzite,

migmatite.

Paleoproterozoic

Se La

Taliha Calc-silicate marble, graphitic

schist, amphibolite, sillimanite

gneiss.

4.5 TECTONICS

4.5.1 Taking into consideration the stratigraphy and structure, the Arunachal Himalaya has

been divided into two broad tectonic divisions, viz. the Frontal Fold Belt (FFB) made

up of Siwalik Group and forming the Sub-Himalaya, and the Main Himalayan Belt

(MHB) comprising Paleoproterozoic to Middle Eocene sediments and associated acid

magmatic rocks forming the Lesser Himalaya and Higher Himalaya. The two belts are

separated by the MBF (Kumar, 1997). The MHB is further subdivided into two zones-

zone I and Zone II, the former forming the Higher Himalaya and the latter Lesser

Himalaya.


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4.5.2 Within MHB, the data on structures within Zone I is scanty, while the rock sequences

of Zone II shows structures related to 4 or 5 (D1,2,3,4,5) deformational episodes. Of these,

the first three deformations (D1,2,3) are restricted to the Bomdila group and associated

acidic intrusions, and Dirang Formation. The first two deformations (D1,2) have been

related to the Luliangian and Zhongyuean orogenic movements during Late

Paleoproterozoic, and the latter (D3) to Mesoproterozoic deformation. The oldest

deformation (D1) is restricted to the Khetabari Formation only. The folds (F1) related to

deformation (D1) are isoclinal to reclined often rootless with angular to subangular

thick hinges, straight attenuated limbs. It is accompanied with metamorphism (M1) of

almandine-amphibolite facies and development of schistosity parallel to bedding. the

folds (F2) developed during deformation (D2) are superimposed over F1 and are of

regional dimensions. These are moderately tight to open asymmetrical, trend in ENE -

WSW direction where not re-oriented and are accompanied with development of strong

schistosity, matamorphism (M2) of green schist facies, and acidic intrusions of

Proterozoic age. The deformation (D3) is post Dirang Formation but pre sedimentation

of the Lower Gondwana Group, and the folds (F3), where not re-oriented, are isoclinal,

reclined or asymmetrical with axial plane striking NNE-SSW to NE-SW and plunging

towards north. Fourth deformation (D4) gave rise to large scale asymmetrical upright to

overturned folds (F4) having ENE-WSW trending axial plain dipping towards north.

Since this deformation has folded not only the Lower Gondwana sequence into an

overturned isoclinal syncline but also the Yinkiong Formation (Paleocene-Early

Eocene) it marks the initiation of the Himalayan Orogeny (HOM-1) related to strong

compressional orogenic movements due to collision of the Gondwana Plate with Asian

Plate along the Indus-Tsangpo Suture. The deformation (D5) refolded all the earlier

doformational structures. The associated folds (F5) are generally open broad,

asymmetrical with axial plane trending NNW-SSE. This deformation is related to

collision of the Central Burmese Plate with the Gondwana and Asian Plate along the

Tidding Suture in the eastern part of Arunachal Pradesh but before the development of

Foredeep.

4.5.3 The folds (F6) are restricted to FFB and are post Kimin Formation (Upper Siwalik) but

pre-Older Alluvium and are thus related to deformation (D6) during last phase of the

Himalayan Orogeny (HOM 4) in early Middle Pleistocene which resulted in the


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development of the Sub-Himilaya. The folds are doubly plunging trending in ENE-

WSW to NE-SW.

4.6 NEOTECTONICS, SEISMICITY & EARTHQUAKES

4.6.1 It is under continuous stress field and still undergoing crustal adjustments since the last

phase of Himalayan Orogeny about 45 millions years ago. these Crustal

adjustments/movements - the Neotectonic activity, is identifiable in the form of block

movements resulting in reactivation of some existing major tectonic movements and

development of cross-faults, and release of stress waves causing earthquakes.

4.6.2 In the area of the two cross - the Bomdila Fault (Nandi, 2001) and the Roing Fault

(Kumar, 1997) have been recorded which post date Himalayan Orogeny and have

affected the sedimentation of the Quarternay sediments in the Brahmaputra Plain and

continue in the area of three proposed hydroelectric schemes, East Kameng District viz.

Dibbin, Phanchung and Tarang Warang in the East Kameng District Arunachal

Himalaya.

4.7 SEISMICITY

4.7.1 The Arunachal Pradesh in the northeastern region of India, situated at the tri-junction of

three plates, viz. Indian Indo-Burmese and Eurasian, falls in seismic zone-V. Seismicity

in the Eastern Himalaya is relatively sparse, and earthquake events are more

concentrated in areas traversed by cross-faults/lineaments (Nandi, 2001). They occur in

diffused pattern having post-collisional intracratonic characteristics. The earthquakes

events (total 974), occurring between 1964-1993, having magnitude > 4 have shallow

focal depth i.e. < 70 km. except for few events. The earthquake of 1947 (epicentre at

280

30' : 940

00') having magnitude M=7.5 was recorded from this domain. Nandi

(2001) has also related microseismicity of Zero area to a deep seated N.W. trending

fault running parallel to the Bomdila and Roing Fault.

4.8 GEOTECHNICAL APPRAISAL

4.8.1 In the project area the rocks exposed belong to the Zero Gneisses (Bomdila Gneiss,

Kaura and Basu Roy, 1981) and the Dirang Formation (MAP-

DIB4-1). The Zero Gneisses include undifferentiated augen gneiss, quartz-biotite

gneiss intrusive in the Tenga Formation of the Bomdila Group. It encloses enclaves of

quartzite of the Tenga Formation. The Dirang Formation comprises a basal unit of

garnetiferous mica schist, quartzite and phyllite at the base and an upper unit of ochre


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from identified potential sources for complete range of physical parameters like

abrasion, impact, crushing values, alkali aggregate reaction, flakeness index, elongation

index, specific gravity, water absorption, fineness modulus, silt and clay contents and

organic impurities. Further a portion of excavated rock from the tunnel is also proposed

to be used for construction. River sand deposits would be tested for its suitability for

use as fine aggregate in concrete and crushed sand may also be used to obtain well-

graded sand.

4.10 CONCLUSIONS AND RECOMMENDATIONS

4.10.1 The Dibbin H.E. Project involves, construction of a 27m high diversion dam on Bishum

River, an approximately 4.43 km. long Head Race Tunnel (H.R.T.) and a power house

for the generation of 100MW of power utilizing a gross head of 165m Prefeasibility

stage studies have been carried out on the basis of field traverses and available

geological data.

4.10.2 The project is located in Lesser Himalayas with complex, geological and geotectonic

setting and in Zone V as per the seismic Zoning Map of India prepared by Indian

Standard Institution (IS : 1893 - 1984). The rocks exposed in the Project Area belong to

Zero Gneisses and the Dirang Formation. The Zero

4.10.3 Gneisses include undifferentrated augen gneiss, quartz-biotite gneiss intrusive in the

Tenga Formation of the Bomdila Group. the Dirang Formation includes, at the base

ganetiferous mica schist, quartzite, and phyllite and an overlying unit of ochre schist

carb schist, laminated flaggy quartzite, calc schist, marble and phyllite.

4.10.4 At the proposed 27m high dam site, the inferred bed rock is quartz-biotite schist with

occasional bands of quartzite. The site appears prima-facie suitable. To fix the dam axis

detailed geological mapping would be required and drilling of two or three shallow

holes to determine the depth to fresh and sound rock.

4.10.5 The approximately 4.43 km. long H.R.T. shall encounter predominantly schist and

quartzite of Dirang Formation. These rocks, generally shall not pose tunnelling problem

except when shear zones charged with water would be encountered. The rock cover

over the tunnel shall vary from 100m to 500m. The drainage patterin the the H.R.T.

alignment area is 'Radial' which would require detail field studies to evaluate its

implication on tunnelling.


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4.10.6 The power house site is located on the left bank of Ditchi Bru close to the confluence

with Bishum Chu, on river terrace material. Drilling of one hole has been suggested at

this site.


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CHAPTER-V

Hydrology


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5.1 GENERAL

5.1.1 The hydrological inputs play a very vital role in planning, execution and operation of

any water resources development project. The hydrological studies are carried out at all

the stages of project development starting from the pre-feasibility stage and are

continued even during the operation of the project. Hydrological studies usually cover

the assessment of quantities of available water and its time variation, estimation of

design flood usually required for the hydraulic design as well as safety of the structure

and sedimentation studies, important from life point view of the project as well as its

effect on the live storage.

5.1.2 The river Brahmaputra is one of the biggest river in the world. The total length of

Brahmaputra river in India is 885 km and its drainage basin in India is 1,95,000 sq. km.

There are 25 principal north bank tributaries of this river. The major one are Subansiri,

the Manas, the Dibang, the Dhansiri, the Torsa, and the Teesta etc. The kameng is one

of these 25 principal north tributaries of this river. The State of Arunachal Pradesh is

enriched with tributaries like Tawang Chu, Kameng, Subansiri, Dihang etc. which

originates from the mighty Himalayas. These are perennial in nature and carry them

floods almost every year during monsoon and as such have huge-hydro potential. The

Kameng river is one of the river system and its drainage area lies in India

approximately between longitudes 92-00-00" to 93-20-55" E and latitudes 26-38-

00 to 28-59-50" N. The drainage area of the Kameng is about 10,777 sq. km. The

river Pachu, Bichom, Papu and Pakhe are the main tributaries of the Kameng. The

Kameng originates at an elevation of 6000 m. The Central Electricity Authority (CEA)

has identified about 31 probable potential sites in the Kameng basin. An index map of

the some of the identified hydro electric potential is shown in Plate-I.

5.2 BASIN CHARACTERISTICS

The topography of the Kameng Basin in upper reaches divides itself in to two distinct

zones i.e. Greater Himalayas and Lower Himalayas. The Greater Himalayas abounds

with Glaciers and mostly are covered with permanent snow above elevation 5000 m

while lower regions in Himalayas are generally rain fed. The topography of the basin is

hilly with steep slopes in u

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Dibbin HE 100MW