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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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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