CONTENTS CHAPTER 2 PROJECT DESCRIPTION CHAPTER-3 METHODOLOGY ADOPTED FOR THE EIA STUDY CHAPTER 4 HYDROLOGY

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1 CONTENTS CHAPTER-1 INTRODUCTION 1.1 Introduction Arunachal Pradesh and Its River Systems Power Potential Of Arunachal Pradesh Project Profile Project Developer - Bhilwara Energy Ltd Policy, Legal and Administrative Framework Scope of the EIA Study Stages in an EIA Study Outline of the Report 1-12 CHAPTER 2 PROJECT DESCRIPTION 2.1 Introduction Nyamjangchhu River Basin Justification of Various Project Alternatives Project Details Salient Features Land Requirement Infrastructure Facilities 2-17 CHAPTER-3 METHODOLOGY ADOPTED FOR THE EIA STUDY 3.1 Introduction Study Area Scoping Matrix Data Collection Summary Of Data Collection Impact Prediction Environmental Management Plan And 3-10 Cost Estimates 3.8 Resettlement And Rehabilitation Plan Catchment Area Treatment Plan Tribal Development Plan Environmental Monitoring Programme 3-11 CHAPTER 4 HYDROLOGY 4.1 Basin Description Water Availability Study Dependable Flow Analysis Design Flood Studies Discharge data measured at site Sediment data measured at site 4-20 i

2 CHAPTER-5 BASELINE SETTING FOR PHYSICO-CHEMICAL ASPECTS 5.1 General Meteorology Geology Geomorphology of The Project Area Seismicity Land Use Pattern Soils Water Quality Ambient Air Quality 5-27 CHAPTER-6 BASELINE SETTING FOR ECOLOGICAL ASPECTS 6.1 General Terrestrial Ecology Fauna Aquatic Ecology Fisheries 6-66 CHAPTER-7 BASELINE SETTING FOR SOCIO-ECONOMIC ASPECTS 7.1 General Demographic Profile of Arunachal Pradesh Demographic Profile of Twang District Demographic Profile of the Study Area Socio-Economic Survey For Project Affected Families Socio-Economic Profile of the Project Affected Families 7-9 CHAPTER-8 PREDICTION OF IMPACTS 8.1 General Impacts on Water Environment Impacts on Air Environment Impacts on Noise Environment Impacts on Land Environment Impacts on Biological Environment Impacts on Socio-Economic Environment Increase Incidence of Water-Related Disease 8-39 CHAPTER-9 CONSTRUCTION METHODOLOGY 9.1 General Basic Assessment of Construction Methodology Pre Construction Activities Approach Road and Bridge Basic Considerations Detailed Design and Construction Drawings Basic Assumptions for Equipment Planning Methodology of Construction for Various Activities Equipment Planning 9-14 ii

3 Annexure Annexure-I A copy of the TOR approved by MoEF Annexure-II Drinking Water Quality Standards Annexure-III National Ambient Air Quality Standards Annexure-IV Ambient Noise Standards Annexure-V List of Plant Species (With their Family and Local Names) Found in the Study Area iii

4 LIST OF FIGURES Figure-1.1 Major river system of the state Figure-1.2 Location of Tawang district Figure-1.3 Project location map Figure-2.1 Layout Plan Figure-3.1 Study area map Figure-4.1 Satellite image of Nyamjang Chhu catchment Figure-4.2 Catchment area map showing drainage network Figure-4.3 Rainfed and Snowfed catchment area Figure-4.4 Location of IMD stations in the region Figure-4.5 Flow duration curve Figure-5.1 Location of IMD stations at Bhalukpong and Dirang Figure-5.2 Annual rainfall at Bhalukpong and Dirang Figure-5.3 Monthly average rainfall at Bhalukpong and Dirang Figure-5.4 Seismic zoning map of India Figure-5.5 FCC image of the project area Figure-5.6 Classified image of the project area Figure-5.7 Sampling stations (Soil, Noise) Figure-6.1 Ecological sampling location (WAPCOS) Figure-6.2 Ecological sampling location (RSET) Figure-9.1 HRT Layout iv

5 CHAPTER-1 INTRODUCTION 1.1 INTRODUCTION India s installed capacity in the hydropower sector is presently estimated at around MW out of total installed capacity of MW. Only about 20% of the economically feasible hydropower potential has been exploited. The economic development in the country in recent times has resulted in widening of the gap between the demand and the supply of power. In order to make power available to all by 2012, the total installed capacity is planned to be increased to about MW. The development of hydropower potential can significantly help to bridge the gap between power demand and supply. The central government alongwith various state governments have taken significant initiatives for development of power projects in both public as well as private sectors. Special emphasis is being made for development of hydropower potential of the country to keep a balanced mix of thermal and hydro power generation. Arunachal Pradesh, with an area of km 2, is the largest state in the northeast region in terms of land area. The state is endowed with mighty rivers with an estimated feasible hydropower potential of about 57,000 MW. The hydropower development in Arunachal Pradesh has been identified as a key area by both the government of India and the state government of Arunachal Pradesh as one of the key areas for meeting the country s increasing energy requirements. Fast track development of hydropower potential in the state both in public and private sector is being pursued by Government of Arunachal Pradesh (GoAP). The state government has signed Memoranda of Understanding (MoU) with 25 developers for development of over MW of hydropower potential in the state. The Government of Arunachal Pradesh has awarded the work of development of the hydropower potential in the Nyamjang Chhu Basin in Tawang district to Bhilwara Energy Limited (BEL). A memorandum of agreement in this regard was signed between GoAP and BEL at Itanagar on the 27 th October, The project is designed as a run-of-the river scheme having a diversion barrage near the Zimithang village with powerhouse near the confluence of the Tawang Chhu with the Nyamjang Chhu. WAPCOS Limited 1-1

6 1.2 ARUNACHAL PRADESH AND ITS RIVER SYSTEMS Profile 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 in the West, China in the North and Myanmar in the East. The States of Assam and Nagaland flank it s Southern and South Eastern borders. The state of Arunachal Pradesh is situated between latitudes 26 30' N and ' N and longitudes 91 30' E and 97 30' E. Arunachal Pradesh is divided in thirteen administrative districts namely; Tawang, West Kameng, East Kameng, Lower Subansiri, Upper Subansiri, West Siang, East Siang, Dibang Valley, Changlang, Tirap, Papum Pare, Lohit and Upper Siang. The main rivers in the State are the Siang, Kameng, Subansiri, Kamla, Siyom, Dibang, Lohit, Noa-Dihing Kamlang and Tirap. 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 subtropical 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 (7,090m above msl) in West Kameng District. The major rivers draining the area with their numerous tributaries from west to east are Tawang, Kameng, Subansiri, Siang, Dibang, Lohit, Kamlang, Noa - Dihing and Tirap. Climate The climate of Arunachal Pradesh varies with elevation. Areas at high elevations in the Upper Himalayas, close to the Tibetan border are subject to a Tundra-type climate, while areas in Middle Himalayas have a temperate climate. The sub- Himalayan and sea-level elevation areas generally experience a humid subtropical climate, along with hot summers and mild winters. The annual average rainfall in various parts of Arunachal Pradesh varies between 2000 mm and 4000 mm. The area experiences high precipitation during the monsoon period between May and September. The prolonged period of Monsoon has resulted in lush forest growth over the hill slopes. The mountain slopes are covered with Alpine, Temperate and Subtropical forest of dwarf rhododendron, Oak, Pine, Maple and Fir. Juniper, Sal and Teak are the main economic species. During winters, WAPCOS Limited 1-2

7 especially months of December to February, the area experiences severe fog with thick mist formation and occasional rainfall. The summer season is hot and humid. Flora Arunachal Pradesh has a rich diversity of flora and fauna and the state is entirely covered with hills and forests. Nearly sq. km of the total land area of sq. km is covered with forests. Forest products are the most significant sector of economy next to agriculture. These forests are home to a sizeable population of various tribes who extract resources from them for their livelihood. The forests of Arunachal Pradesh include some 5000 species of plants, about 85 terrestrial mammals, over 500 birds and a large number of butterflies, insects and reptiles. The vegetation of the state falls under four broad climatic categories and can be classified in five broad forest types which are: tropical forests, sub-tropical forests, pine forests, temperate forests and alpine forests. Rivers There are five major river basins in the State, namely Kameng, Subansiri, Siang, Dibang and Lohit River basin. Almost all the major river systems flow from North to South and ultimately drain into the Brahmaputra. Apart from the major rivers, the State has many small rivulets which are perennial in nature and provide ideal condition for developing projects in the category of micro/mini and small HEP. The major river system of the state are shown in Figure-1.1. Figure-1.1: Map of River Systems WAPCOS Limited 1-3

8 1.3 POWER POTENTIAL OF ARUNACHAL PRADESH Arunachal Pradesh has a huge potential to generate hydroelectric power. The state has number of large, medium, mini and micro hydel projects. The Government of Arunachal Pradesh began planned development of the hydropower potential of the state and invited private developers to invest in the hydropower sector for the economic growth of the state and to decrease the energy deficit in the country. The details of projects being developed in Arunachal Pradesh are indicated in Table 1.1. S. No. TABLE -1.1 BASINWISE HYDRO POWER PROJECTS UNDER DEVELOPMENT IN ARUNACHAL PRADESH Basin Name of Project Probable IC (MW) 1 Tawang Tawang-I 750 NHPC 2 Tawang Tawang-II 750 NHPC Allotted to 3 Tawang Nykcharongchu 96 SEW Energy 5 Tawang Mago Chu 96 SEW Energy 6 Tawang Nyamjungchhu 900 Bhilwara Energy Ltd. TOTAL OF TAWANG BASIN Kameng Kameng-I 1120 NEEPCO 2 Kameng Kameng-II 600 Mountain Fall India Pvt. Ltd. 3 Kameng Kameng Dam 600 KSK Electricity Financing India Pvt. Ltd. 4 Kameng Gonri 90 Patel Engineering Ltd. 5 Kameng Saskang 7 Patel Engineering Ltd. 6 Kameng Talong 160 GMR Energy Ltd. 7 Kameng Phanchung 60 Indiabull Real Estate Ltd. 8 Kameng Utung 100 KSK Energy Ventures Ltd. 9 Kameng Nazong 60 KSK Energy Ventures Ltd. 10 Kameng Dibbin 125 KSK Electricity Financing India Pvt. Ltd. 11 Kameng Khuitam 29 Adishankar Power Pvt. Ltd. 12 Kameng Pichang 31 Indiabull Real Estate Ltd. 13 Kameng Tarang Warang 30 Indiabull Real Estate Ltd. 14 Kameng Sepla 46 Indiabull Real Estate Ltd. WAPCOS Limited 1-4

9 S. No. Basin Name of Project Probable IC (MW) Allotted to 15 Kameng Jameri 50 KSK Energy Ventures Ltd. 16 Kameng Tenga 8 ECI Engineering & Const. Company Ltd. 17 Kameng Dimijin 20 KSK Energy Ventures Ltd. 18 Kameng Dinchang 90 KSK Energy Ventures Ltd. 19 Kameng Dinen 10 KSK Energy Ventures Ltd. 20 Kameng Dikhri 15 KSK Energy Ventures Ltd. 21 Kameng Nafra 96 SEW Energy 22 Kameng Pakke Bung-I 15 Energy Development Company Ltd. 23 Kameng Pakke Bung-II 15 Energy Development Company Ltd. 24 Kameng Pachuk-I 60 Energy Development Company Ltd. 25 Kameng Pachuk-II 60 Energy Development Company Ltd. 26 Kameng Majingla 60 Energy Development Company Ltd. 27 Kameng Dengzi 18 Satyam (North East) Hydro Power Ltd. 28 Kameng Lower Ngorgum 18 Satyam (North East) Hydro Power Ltd. 29 Kameng Upper Ngorgum 9 Satyam (North East) Hydro Power Ltd. TOTAL OF KAMENG BASIN Subansiri Par 65 KVK Energy & Infrastructure Ltd. 2 Subansiri Dardu 60 KVK Energy & Infrastructure Ltd. TOTAL OF SUBANSIRI BASIN Dikrong Pare 110 NEEPCO 2 Dikrong Turu 90 ECI Engineering & Const. Company Ltd. TOTAL OF DIKRONG BASIN Siang Tato-II 700 Reliance Energy Ltd. 2 Siang Naying 1000 D.S.Construction 3 Siang Siang Lower 1600 Jaiprakash Associates Ltd. 4 Siang Siang Middle (Siyom) 1000 Reliance Energy Ltd. WAPCOS Limited 1-5

10 S. No. Basin Name of Project Probable IC (MW) Allotted to 5 Siang Pauk 50 Velcan Energy Ltd. 6 Siang Heo 90 Velcan Energy Ltd. 7 Siang Hirong 500 Jaiprakash Associates Ltd. 8 Siang Tato-I 80 Velcan Energy Ltd. 9 Siang Simang-I 67 Adishankar Power Pvt. Ltd 10 Siang Simang-II 39 Adishankar Power Pvt. Ltd 11 Siang Simang-III 44 Adishankar Power Pvt. Ltd 12 Siang Hirit 84 Velcan Energy Ltd. 13 Siang Barpu 70 Raajratna Metal Industries 14 Siang Kangtangshiri 35 Raajratna Metal Industries 15 Siang Ropum 40 Raajratna Metal Industries 16 Siang Rego 70 Tuff Power Pvt. Ltd. 17 Siang Yamne Stage-I 60 Abir Const. Pvt. Ltd. 18 Siang Yamne Stage-II 60 Abir Const. Pvt. Ltd. 19 Siang Simen 21 Satyam ( North East) Hydro Power Ltd. TOTAL OF SIANG BASIN Dibang Etalin 4000 NTPC 2 Dibang Emra-II 390 Athena Energy Venture Pvt. Ltd 3 Dibang Agoline 375 Bhilwara Energy Limited 4 Dibang Malinye 335 Bhilwara Energy Limited 5 Dibang Emra-I 275 Athena Energy Venture Pvt. Ltd 6 Dibang Attunli 500 NTPC 7 Dibang Sissiri 222 Soma Enterprise Ltd. 8 Dibang Dibang 3000 NHPC Multipurpose TOTAL OF DIBANG BASIN Lohit Hutong-II 1250 Moutain Fall India Pvt. Ltd. 2 Lohit Gimliang 31 Sai Krishnodaya Industries (P) Ltd. 3 Lohit Raigam 32 Sai Krishnodaya Industries (P) Ltd. WAPCOS Limited 1-6

11 S. No. Basin Name of Project Probable IC (MW) Allotted to 4 Lohit Tidding-I 31 Sai Krishnodaya Industries (P) Ltd. 5 Lohit Kalai-I 1450 Mountain Fall India Pvt. Ltd. 6 Lohit Demwe 3000 Athena Energy Venture Pvt. Ltd. 7 Lohit Kamlang Sai Krishnodaya Industries (P) Ltd. TOTAL OF LOHIT BASIN GRAND TOTAL The Nyamjang Chhu is an important perennial river flowing through Tawang district of Arunachal Pradesh. The river originates in Tibet and flows in a nearly north-south direction into India in the Zimithang region. Many tributaries add to the waters of Nyamjang Chhu, such as the Gomkang Rong Chhu, the Sumta Chhu, the Taksang Chhu to name a few. The Nyamjang Chhu merges with the Tawang Chhu near Lumla and the resultant river flows into Bhutan where it is known as Gamri Chhu. With a view to harness the available potential of the Nyamjang Chhu, this project was conceptualised and allotted for development to Bhilwara Energy Limited (BEL). No topographical survey, flow gauging or other investigation studies were available in this basin prior to the granting of license to BEL. The site investigations including collection of topographical, geotechnical and discharge data of the river were carried out between October 2006 and December The total potential of the basin was assessed to be around 900 MW. 1.4 PROJECT PROFILE The Nyamjang Chhu Hydroelectric project is a run-of-the-river scheme with peaking pondage to harness the hydropower potential of River Nyamjang Chhu. The project will utilize a gross head of about m for a generation of 780 MW in an underground powerhouse. WAPCOS Limited 1-7

12 The project is located in Tawang district of Arunachal Pradesh in north-western part of State. Tawang is bordered by Tibet in the North, Bhutan in the south-west and Sela ranges separate it from the West Kameng district in the East. Tawang district has an area of about 2085 sq. km and for administrative purposes; it is further sub-divided into the Lumla, Jang and Tawang sub-divisions. Elevations in the area range between 3,000 to 22,000 feet and inhabitants are found in lower altitudes, where there is cool temperate climate. In winter, Tawang frequently experiences heavy snowfall. Tawang Chhu is the main river in the district and flows mainly in the east-west direction. Nyamjang Chhu is a major right bank tributary of Tawang Chhu. It originates in Tibet and enters India near the village of Khinzemane and flows mostly in the north-south direction up to its confluence with Tawang Chhu. The elevation in the area ranges between 900 to 6600 m. Only the lower altitudes cool temperate climate are habitable. In winter, Tawang frequently experiences heavy snowfall. The location of Tawang district is shown in Figure Figure-1.2: Location of Tawang District Tawang Chhu is the main river in the district and flows mainly in the east-west direction. Nyamjang Chhu is a major right bank tributary of Tawang Chhu. The river originates in Tibet and enters India near the village of Khinzemane and flows mostly in the north-south direction up to its confluence with Tawang Chhu. WAPCOS Limited 1-8

13 The Nyamjang Chhu (NJCHEP) is located along the Nyamjang Chhu between Zimithang and Lumla. The diversion site is located near Zimithang having coordinates at latitude N, longitude E and the powerhouse is located near confluence of Nyamjang Chhu and Tawang Chhu at latitude N, longitude E. The project location map is enclosed as Figure-1.3. The project area is accessible by road and by helicopter. The powerhouse is located about 590 km from Guwahati and 575 km from Itanagar, the capital of Arunachal Pradesh. The nearest broad gauge rail head is at Naugaon in Assam about 521 km from powerhouse. The nearest narrow gauge rail head is at Bhalukpong about 380 km from the powerhouse. The nearest airports are at Tezpur and Guwahati. The state government is providing regular helicopter service from Itanagar and Guwahati to Tawang. The district headquarters of Tawang district is at Tawang city and is connected with Guwahati via National Highway NH 52 and 52 A. The barrage and powerhouse are accessible from Tawang via the State highway between Tawang- Lumla-Zimithang. From Lumla, a 22 km long gravel road is available to powerhouse site. Lumla is located about 40 km from Tawang and Zimithang is located about 48 km from Lumla and 93 km from Tawang. 1.5 PROJECT DEVELOPER - BHILWARA ENERGY LTD. Bhilwara Energy Ltd. (BEL) is the flagship company of LNJ Bhilwara Group to develop and operate power assets in India and overseas. The company has a portfolio of 2487 MW in hydro power currently in various stages of implementation. Bhilwara Energy Ltd. is the first hydropower developer with 100% merchant sale model. The LNJ Bhilwara Group was among the first private sector company to venture into power sector when the sector was opened for private participation in In 1993 the Group entered into a Memorandum of Understanding with the State of Himachal Pradesh for implementation of two hydroelectric projects in Kullu district namely, 86 MW Malana and 192 MW Allain Duhangan. The group commissioned its first hydro power plant - Tawa MW located in Madhya Pradesh in the year The Malana Hydroelectric project was completed in July 2001 in 30 months. The Allain Duhangan Hydro Electric Project in the State of Himachal Pradesh Project has been commissioned form Allain side and the Duhangan side will be commissioned by July WAPCOS Limited 1-9

14 The Company also owns Indo Canadian Consultancy Services Limited, an engineering consultancy company set up in collaboration with RSW International, Canada for providing consultancy to power projects. 1.6 POLICY, LEGAL AND ADMINISTRATIVE FRAMEWORK The principal Environmental Regulatory Agency in India is the Ministry of Environment and Forests (MOEF), Government of India. MOEF formulates environmental policies and accords environmental clearance for the projects. The State Pollution Control Board (SPCB) accords No Objection Certificate (NOC) Consent for Establishment and consent for Operation for the projects. As per the guidelines pertaining to Environmental clearance issued by Ministry of Environment and Forests (MoEF) dated September 14, 2006, the Terms of Reference (TOR) for the EIA study is to be approved by MoEF. In this connection, Form-I alongwith TOR in the prescribed format was submitted to MoEF. The same was received by the Environmental Appraisal Committee of River Valley Projects of MoEF. The TOR was approved by MoEF vide their letter no. J-12011/87/2007/IA.I, dated A copy of the TOR approved by MoEF is enclosed as Annexure-I. 1.7 SCOPE OF THE EIA STUDY The brief scope of EIA study includes: - Assessment of the existing status of physico-chemical, ecological and socio-economic aspects of environment - Identification of potential impacts on various environmental components due to activities envisaged during construction and operation phases of the proposed hydro-electric project. - Prediction of significant impacts on various aspects of environment. - Delineation of Environmental Management Plan (EMP) outlining measures to minimize adverse impacts during construction and operational phases of the proposed project. - Formulation of Resettlement and Rehabilitation (R&R) Plan. - Formulation of Catchment Area Treatment (CAT) Plan. - Formulation of environmental quality monitoring programmes for construction and operation phases. - Estimation of Cost for implementation of Environmental Management Plan, Resettlement and Rehabilitation Plan, Catchment Area Treatment Plan and Environmental Monitoring Programme. WAPCOS Limited 1-10

15 1.8 STAGES IN AN EIA STUDY The purpose of this section is to enumerate the steps involved in an Environmental Impact Assessment (EIA) study, which are described in the following paragraphs. Scoping : An exhaustive list of all likely impacts drawing information from as many sources as possible was prepared. The next step was to select a manageable number of attributes which were likely to be affected as a result of the proposed project. The various criteria applied for selection of the important impacts were follows: magnitude extent significance Description of Environment: Before the start of the project, it is essential to ascertain the baseline levels of appropriate environmental parameters which could be significantly affected by the implementation of the project. The baseline status assessed as a part of CEIA study involved both field work and review of data collected from secondary sources. Prediction of Impacts: is essentially a process to forecast the future environmental conditions of the project area that might be expected to occur as a result of the construction and operation of the proposed hydroelectric project. An attempt was generally made to forecast future environmental conditions quantitatively to the extent possible. But for certain parameters which cannot be quantified, general approach was to discuss such intangible impacts in quantitative terms so that planners and decision-makers are aware of their existence as well as their possible implications. Environmental Management Plan: the approach for formulation of an Environmental Management Plan (EMP) is to maximize the positive environmental impacts and minimize the negative ones. The steps suggested include modifications of plans, engineering designs, construction schedules and techniques, as well as operational and management practices. After selection of suitable environmental mitigation measures, cost required for implementation of various management measures was also estimated. Environmental Monitoring Programme: An Environmental Monitoring Programme for implementation during project construction and operation phases has been estimated to oversee the environmental safeguards, to ascertain the WAPCOS Limited 1-11

16 agreement between prediction and reality and to suggest remedial measures not foreseen during the planning stage but arising during operation and to generate data for further use. 1.9 OUTLINE OF THE REPORT The document for the Comprehensive EIA study for the proposed Nyamjangchhu hydroelectric project has been presented in two volumes. Volume-I presents the Environmental Impact Assessment (EIA) study and Volume-II delineates the Environmental Management Plan. The present document (Volume 1) outlines the findings of the EIA study for the proposed Nyamjangchhu hydroelectric project. The contents of the document are organized as follows: Chapter-1 The Chapter gives an overview of the need for the project. The policy, legal and administrative framework for environmental clearance has been summarized. The objectives and need for EIA study too have been covered. Chapter-2 gives a brief description of the proposed Nyamjangchhu hydroelectric project. Chapter-3 outlines the methodology adopted for conducting the Comprehensive EIA study for the proposed Nyamjangchhu hydroelectric project. Chapter-4 covers the hydrological aspects of the proposed Nyamjangchhu hydroelectric project. The data was mainly collected form the DPR prepared for the proposed Nyamjangchhu hydroelectric project. Chapter-5 covers the environmental baseline conditions covering physical aspects of environment. The baseline study involved both field work and review of existing documents, which is necessary for identification of data which may already have been collected for other purposes. Chapter-6 presents the biological aspects of environment. The study is based on collection of data from various secondary data sources. As a part of the Comprehensive EIA study, detailed ecological survey for was conducted for three seasons. The findings of the survey were analysed and ecological characteristics of the study area have been described in this Chapter. Chapter-7 covers pre-project environmental baseline conditions covering socioeconomic aspects of environment. The baseline study involved data collection using primary as well as secondary sources of data and public consultation. Chapter-8 describes the anticipated positive and negative impacts as a result of the construction and operation of the proposed Nyamjangchhu hydro-power project. It is essentially a process to forecast the future environmental conditions WAPCOS Limited 1-12

17 of the project area that might be expected to occur as a result of the construction and operation of the proposed project. An attempt was generally made to forecast future environmental conditions quantitatively to the extent possible. But for certain parameters, which cannot be quantified, general approach has been to discuss such intangible impacts in qualitative terms so that planners and decision-makers are aware of their existence as well as their possible implications. Chapter-9 gives a brief description of the methodology and schedule to adopted for construction of the proposed Nyamjangchhu hydroelectric project. WAPCOS Limited 1-13

18 CHAPTER - 2 PROJECT DESCRIPTION 2.1 INTRODUCTION The Nyamjang Chhu basin lies in the north-west area of Arunachal Pradesh with its catchment spreading across international border covering part of Tibet. Nyamjang Chhu originates from snow clad peaks in Tibet and flows in India from north to south direction up to its confluence with Tawang Chhu. The total catchment area of the Nyamjang Chhu up to the confluence with Tawang Chhu is about 3170 km 2. The catchment area up to diversion site near Zimithang is about 2650 km 2. The catchment area is mostly of tropical wet climate and supports dense mixed forest. The area is characterized by hills with steep gorges and deep rugged valleys with streams feeding Nyamjang Chhu River system of which Takhsang Chhu and Sumta Chhu are major contributors. Nyamjang Chhu (HEP) is a run-of-the-river scheme with reservoir having diurnal storage. The project is located in Tawang District of Arunachal Pradesh. The project area is connected to other parts of the state and Assam through road network and helicopter service. The scheme envisages utilization of the available river flow at Zimithang and gross head of about m between barrage and tailrace outfall near confluence of Nyamjang Chhu with Tawang Chhu near Kumba village to generate 780 MW in an underground power house. The Project is expected to generate an annual energy of GWh, in 90% dependable year. The diversion structure is proposed at Zimithang with FRL at El m. Maximum Tail water level at the TRT outfall is El and the nozzle level for Pelton turbines is proposed at El m providing a gross head for power generation of m. The diversion of discharges from Taksang Chhu to the water conductor system of Nyamjang Chhu HEP has been proposed at an elevation EL m. The total time schedule for the project construction is considered as 74- months including 12-months for establishment of access roads, infrastructural facilities and other pre-construction activities. 2.2 NYAMJANGCHHU RIVER BASIN The Nyamjang Chhu basin lies in the north-west area of Arunachal Pradesh with its catchment spreading across international border covering part of Tibet. Nyamjang Chhu originates from snow clad peaks in Tibet and flows in India WAPCOS Limited 2-1

19 from north to south direction up to its confluence with Tawang Chhu. The total catchment area of the Nyamjang Chhu up to the confluence with Tawang Chhu is about 3170 km 2. The catchment area intercepted up to diversion site near Zimithang is about 2650 km 2. The catchment area is mostly of tropical wet climate and supports dense mixed forest. The area is characterized by hills with steep gorges and deep rugged valleys with streams feeding Nyamjang Chhu River system of which Takhsang Chhu and Sumta Chhu are major contributors. 2.3 JUSTIFCIATION OF VARIOUS PROJECT ALTERNATIVES Various aspects considered while selecting the scheme of Naymajangchhu HEP are briefly described in the following paragraphs. Topographical Aspects Initial reconnaissance identified the suitable reach for project development between Zimithang and Kumba villages. River bed Elevations at Zimithang and at the confluence of Nyamjang Chhu with Tawang Chhu near Kumba village are around El m and El m respectively. Topographical details including physical features, villages, religious monuments and other structures falling within the reach from Zimithang to the confluence were identified to assess possible impacts of placing the project structures in development alternatives. Geomorphology of the area The area is characterized by undulating dissected structural hills, which have been denudated forming various features. The area near BTK Bridge is characterized by massive landslides and a fault is located just upstream of the Bridge. The area near Zimithang village is marked by flat river terraces and flood plains. The river is about 200m wide at this location with very low gradient making it suitable for the location of diversion structure. Lithology The general lithology observed in the area is as follows: Phyllitic schist Schist with quartzitic bands Quartzite Gneiss with quartzitic bands Gneiss WAPCOS Limited 2-2

20 This is a metamorphic terrain and rock types are generally competent enough for most project components. Major faults such as MCT, MBT are not traced in the project area. Social Aspects The BTK Bridge is an important bridge linking the habitations in Zimithang and other higher reaches of Lumla sub-division in Tawang district. Safety of this bridge is required from adverse impact due to development of the project. An important Buddhist religious site, the Gorsam Stupa (refer Exhibit-2.1), is located about 8 km upstream of the BTK Bridge. It is a very old stupa held in great esteem by the Buddhist Community. An annual festival attended by Buddhists and other people from all over the state and abroad is held in this Stupa. While formulating the project development scheme, it was ensured that there are no adverse impacts to the Gorsam Stupa. Environmental Aspects The environmental aspects considered were: Exhibit 2.1 : Gorsam Stupa Minimal submergence area Minimum tree cutting Minimum disturbance to wildlife during construction of project and other appurtenances including roads WAPCOS Limited 2-3

21 Alternatives Studied The barrage site at Zimithang has been selected near Zimithang for the following reasons: provides the possibility for harnessing the highest feasible head suitable for development in the Nyamjang Chhu. height of the diversion structure is low as river gradient in this reach is flat and the width of the river is sufficient to provide peaking storage. The effect of seismicity on the diversion structure will also be low. minimal disturbance to the local population. No impact on Gorsam stupa. No adverse geological feature is observed in the vicinity of this location. Sufficient space for construction of barrage & desanding works and for contractor s facilities. The study of geological features and field investigations suggest the depth of rock available in this location varies from 60 to 90 m, as a result, barrage type diversion structure is proposed. As a part of DPR, four alternatives were studied. In all four alternatives, barrage type diversion structure is proposed at Zimithang at river bed elevation of m and Power House on the left Bank near Namstering Village with tailrace discharging at EL m. Alternative I This alternative proposes the water conductor system and powerhouse on the right bank of river Nyamjang Chhu. A Head regulator, feeder channel & Surface Desilting Basin are planned on Right bank for diverting the design discharge through a km long Head Race Tunnel to a pressure shaft leading to the turbines for power generation in underground power station. The length of the TRT, MAT and Pressure Shaft are about 1800 m, 1090 m and 1335 m respectively. The proposed project components on the right bank are approachable only to the limited length of the river from the existing available road network. There are about 11 first order streams on the right bank draining into Nyamjang Chhu in the project reach under consideration. These further join to form second and third order streams. It is also observed that tributaries to the Nyamjang Chhu are more deeply incised on the right bank and therefore the right bank alternative requires longer water conductor system and associated WAPCOS Limited 2-4

22 works within the development reach of the river. The length of road network to be developed in the area for project development is about 75 km with construction of two major bridges across Nyamjang Chhu. Alternative II This alternative proposes the water conductor system and powerhouse on the left bank of Nyamjang Chhu having the diversion structure at Zimithang and power House near confluence of Nyamjang Chhu with Tawang Chhu. A Barrage is proposed. The head regulator, feeder channel, surface desilting chamber and HRT intake are proposed on left bank. Underground Power House is proposed near Kumba Village. TRT level at the outfall is El m. The length of the TRT, MAT and Pressure Shaft are about 1546 m, 1080 m and 2550 m respectively. The HRT is aligned on left bank with 6 Nos. of adits. Surge shaft is located at elevation El and is open to sky. The location of the surge shaft on the left bank is fixed for all the alternatives due to topographical limitations. All the main project components are approachable in this alternative. The length of the pressure shaft in this alternative is maximum and will involve huge steel cost. The length of HRT is km. Alternative III This alternative is on the left bank of river Nyamjang Chhu, The diversion structure is placed at Zimithang at the river bed elevation of El m and Power House on the Left Bank near Gispu Village just upstream of the Gomkarang Chhu nala. The proposed gross storage required at Zimithang is 0.95 Mcum with FRL at El m and MDDL at El m respectively. A gated barrage with overflow structure near Zimithang village with head regulator & Surface Desilting Basin on Left bank is planned for diverting the design discharge through a km long Head Race Tunnel to a pressure shaft leading to the turbines for power generation in underground power station located near Gispu Village. The length of the TRT, MAT and Pressure Shaft are about 5846 m, 1375 m and 1000 m respectively. WAPCOS Limited 2-5

23 The location of the HRT intake is near the desilting Chamber. The length of the feeder Channel is reduced in this arrangement leading to increased length of the silt flushing arrangement. The HRT is aligned on left bank with 5 No. adits. Surge shaft is located at elevation El and is underground. All the main project components are approachable in this alternative. The length of the HRT and pressure shaft is minimum in this alternative; however power house is to be located 100 m below the river bed for full utilisation of the available head for power generation. Alternative IV This alternative is on the left bank of river Nyamjang Chhu, The diversion structure is placed at Zimithang at the river bed elevation of m and Power House on the Left Bank near Kharteng Village just upstream of the confluence of Nyamjang Chhu with Tawang Chhu. The proposed gross storage required at Zimithang is 0.95 M cum with FRL at El m and MDDL at El m respectively. A gated barrage near Zimithang village with head regulator, Surface Desilting Basin on Left bank is planned for diverting the design discharge through a km long Head Race Tunnel to a pressure shaft leading to the turbines for power generation in underground power station located near Gispu Village. The length of the TRT, MAT and Pressure Shaft are about 1965 m, 1010 m and 2530 m respectively. The location of the HRT intake is near the desilting Chamber after 600 m long feeder Channel from head regulator. The HRT is aligned on left bank with 6 No. adits. Surge shaft is located at El and is open to sky. All the main project components are approachable in this alternative. The length of the pressure shaft and MAT is optimal in this alternative considering the overall scheduling of the project. Comparison of Alternatives The selection of optimal alternatives for Nyamjang Chhu H.E. Project is based on the comprehensive study of the four alternatives described above. The assessment of each alternative is based on detailed investigations and studies covering assessment of geology, topographical features, and possibility of utilisation of maximum head, storage characteristics, alignment of water conductor system and other relevant parameters. After considering the above factors, alternative IV is adopted. The main consideration for selection of Alternative IV included the following: WAPCOS Limited 2-6

24 Left bank is suitable for development of the project based on accessibility and geological considerations. Most of the project components are easily accessible in this alternative. Utilizes the total head available in the reach. Length of the main access tunnel (MAT), Pressure Shaft is suitable from construction point of view. Alternative I on the right bank requires large network of roads to be developed besides longer length of water conductor system due to presence of deeply incised streams. This alternative would have some adverse impact on the old Buddhist stupa on right bank which is held in great esteem by the local population. Alternative II has a very long length of the pressure shaft and also involves heavy cutting of the river bed for the silt flushing arrangement. Alternative - III has the high risk of seepage problem in utilising the full head as the power house is located about 100 m below the river bed. The length of the TRT is also on a higher side; thus leading to minor loss of head as well as construction problems. As the location of the diversion structure is almost same in all the alternatives, the considerations on the alignment of tunnel, approach to adits, length of the pressure shaft and location of the power house favours Alternative IV techno-economically. Considering complete utilisation of the drop available in the river and economics of cost of power generation, in the DPR, scheme under Alternative IV has been selected. During the project planning stage, it was earlier planned to commission the project with a capacity of 900 MW with a rated discharge of 99 cumec. The present proposal envisages project capacity as 780 MW, with rated discharge as 87 cumec. The reduction in rated discharge will lead to increased flow to the tune of 12 cumec in the river stretch between the barrage site and the tail race disposal site. This is an added advantage of the present proposal, as it will also increase the Environmental Flows. WAPCOS Limited 2-7

25 2.4 PROJECT DETAILS Major Project Components The project envisages construction of barrage across Nyamjang Chhu River, a head regulator, Feeder Channel, desilting chamber with collection pool & intake, a headrace tunnel, surge shaft, pressure shafts, underground powerhouse and tailrace tunnel. The project layout plan is enclosed as Figure The project components are described in the following paragraphs. Barrage Average bed level at barrage site is El m. FRL is fixed at EL m and MDDL at EL m keeping in view peaking storage and the inflow of water in Nyamjang Chhu during lean period. The top of the barrage has been proposed at EL m. The barrage has been provided with spillway for passing of Design flood with 11 bays each 10 m wide and 7.5 m high having crest at elevation of EL m. The under sluice has been provided with 3 bays each of 5 m width and 6.3 m high having crest at elevation of EL m. Intake and Desilting Arrangement The head regulator, desilting basin and power intake systems are proposed on the left bank of river Nyamjang Chhu. The Head regulator has 8 gates of 4 m x 6.5 m each. Feeder channel up to the desilting basin is 600 m long and 20 m wide and is divided into four compartments. The flow depth in the feeder channel is 3.55 m. Eight desilting basins are proposed each having a width of 10.5m and length of 150 m for removal of silt particle of size 0.2mm and above. The invert level of the tunnel intake structure has been kept at EL taking into consideration the water seal requirement to prevent vortex formation and air entrainment. The intake structure has been provided with trash racks to prevent entry of trash in the water conductor system. Head Race Tunnel A km long, 6.2 m dia circular concrete lined HRT has been designed to carry design discharge of 87 m 3 /sec of water. Six (6) intermediate adits are provided to facilitate the construction of headrace tunnel. Surge Shaft A 240 m high, 4/10/12 m dia open to sky restricted orifice type surge shaft has been designed to take care of the water hammer and mass oscillations due to load variations. WAPCOS Limited 2-8

26 Butterfly Valve Chamber Two (2) underground Butterfly valve chambers 12.5 m long, 12.5 m wide and12.5 m high chambers have been provided to accommodate two Butterfly valves of 3.3 m dia each. The chambers are inter-connected by a 5.0 m dia connecting gallery. Pressure Shaft Two underground pressure shafts each of 3.3 m dia & 2103 m long steel lined bifurcating into six shafts of 2.0 m diameter & 423 m long, are provided to convey water to the six turbines in the power house. Underground Power House Complex An underground cavern of m long x 20 m wide x 45 m high has been provided to house 6 units of 130 MW Pelton turbines and spherical type main inlet valves. Transformer cavern m long x 16.3 m wide x 24 m high has been provided to accommodate 20 nos. single phase 13.8/ 420 kv transformers including three spare transformers, each of 56 MVA capacity and 400 kv Gas Insulated Switchgear (GIS). Tail Race Tunnel (TRT) A 1965 m long 7.0 m dia Circular shaped tunnel has been provided to carry a total discharge from the turbines back to the river. Transmission System The power evacuation from the project would be carried out by the PGCIL as per the recent regulation issued by CERC. Project Benefits The annual energy from the project has been assessed as GWh in 90% dependable year. The project would also provide peaking benefits of 780 MW round the year. Project Cost The Project is estimated to cost Rs million at December 2010 Price Level. The details are given below: a) Total direct charges including Civil and E&M works :Rs.5, million b) Indirect Charges : Rs.71.1 million c) Escalation : Rs million d) IDC & Financial Charges : Rs million e) Total Complétion cost including IDC & Financing : Rs million Charges WAPCOS Limited 2-9

27 2.5 SALIENT FEATURES The salient features of the Project are given in Table-2.1. The project layout map is shown in Figure-2.1. TABLE-2.1 Salient features of Nyamjangchhu hydroelectric project 1. LOCATION State : Arunachal Pradesh District : Tawang River : Nyamjang chhu Vicinity : Tawang Longitude at diversion site : Latitude at diversion site : HYDROLOGY Catchment area at diversion : 2650 Sq. Km. Design Flood (50 year Return period) : 3400 Cumecs Design Discharge 87 Cumecs 3. BARRAGE Length of Barrage : m H.F.L : m F.R.L : m Average river bed level : m Max. height of Barrage above Avg. : m River Bed Level Bridge deck level : m Max. height of Varrage above river bed : 10.2 m levels Design Flood (SPF) : 3400 Cumecs 3(a). SPILLWAY Type : Gated No. of Bays : 11 Nos. Length of Bay : m Sill level : m Size of gates : 7.5m(H) x 10m(W) Type of gate : Vertical lift gates Energy Dissipation arrangement : Stilling Basin type 3(b). UNDERSLUICE Type : Gated No. of Bays : 3 Nos. Length. of Bay : 5.00 m. Sill Level : m Size of gates : 6.3m(H) x 5m(W) Type of gates : Vertical lift gates Energy Dissipation System : Stilling Basin. WAPCOS Limited 2-10

28 3(c). HEAD REGULATOR Length : 46 m HFL : m FRL : m MDDL : m Sill level : m Bridge deck level : m No. of bays : 8 Nos. Length of bay : 4.00 m Size of gates : 6.5 m(h) x 4.0 m(w) Type of gates : Vertical lift gates No. of silt excluder tunnels : 8 Nos. Size of silt excluder tunnels : 0.75m(H) x 1.5m(W) 4. FEEDER CHANNEL Length : 600 m Total width : m No. of channels : 4 Nos. Width : 4.25 m Height : 6.00 m Velocity of flow : 2 m/s 5. DESILTING ARRANGEMENT Type : Surface basins Hopper type No. & Size of desilting basin (LxBxH) : 8 Nos., 150m x 10.50m x 19m Particle size to be excluded : 0.20 mm and above Flow through velocity : 0.2 m/s Flushing velocity : 4.5 m/sec. Dia. of silt flushing Conduit : 2.0 m 6. HEAD RACE TUNNEL Type and Size : Concrete Lined Circular Shaped, 6.20 m Finished Dia. Velocity : 2.88 m/s Length : m Design discharge : 87 cumec. Slope : 1 in ADITS Type : D Shaped Adit No.-1 : 7.0mx5.0m, Length =362.0m Adit No.-2 : 7.0mx5.0m, Length =322.0m Adit No.-3 : 7.0mx5.0m, Length =460.0m Adit No.-4 : 7.0mx5.0m, Length WAPCOS Limited 2-11

29 =655.0m Adit No.-5 : 7.0mx5.0m, Length =439.0m Adit No.-6 : 7.0mx5.0m, Length =476.0m Adit No.-7 : 7.0mx7.0m, Length =436.0m Adit No.-8 : 7.0mx5.0m, Length =980.0m Adit No.-9 : 7.0mx5.0m, Length =1088.0m 8. SURGE SHAFT Type : Open to sky, Restricted orifice type. Size: : 4.0m, 10.0m & 12.0m Dia., m high. Maximum Upsurge Level : m Minimum Downsurge Level : m Bottom Level : m Top Level : m 9. PRESSURE SHAFT Type : Steel Lined Size Main : 2 No., 3.3m dia, each m long. Unit : 6 No, 2.0m dia, each Pressure Shaft m long Velocity : 5.07 m/s Type & thickness of steel liner : ASTM-A-537, CL-II & ASTM-A-517, Gr.-F, 20 mm to 65 mm thk. Valve gallery : 12.5m (H) x 12.5m (W) x 69.5m (L) 10. POWERHOUSE Type : Underground Installed Capacity : 780 MW (6 x 130 MW) Size : 166.2m x 20m x44.5m Maximum gross head : m Max Net head : m Min Net Head : m Rated Net head : m C/L of Turbine : m Erection bay floor level : m Crane beam level : m Maximum TWL : m Capacity of E.O.T crane : 2 x 140 M Tons 11. TRANSFORMER CAVERN Size : m x 16.3m x 24m WAPCOS Limited 2-12

30 12. TAILRACE TUNNEL Type : Circular shaped Size : 7.0m Dia., m Long 13. TURBINES No. & Type : 6 No., Vertical Shaft Pelton. Rated Power (at generator terminal) : MW Rated net Head : m Rated discharge : 87 cumec. Specific Speed : 500 rpm 14. MAIN INLET VALVE (MIV) Type : Spherical valve Diameter : 2.0 m 15. GENERATOR Type : Synchronous Type Number : 6 Nos. Rated Capacity : MVA Nominal Active Power : MW 16. MAIN GENERATOR STEP UP TRANSFORMER No. of Single Phase Transformer : 20 Nos. Rated Output : 56 MVA Rated Voltage : 13.8 KV/ 420 KV Frequency : 50Hz Type of cooling : OFWF 17. SWITCHYARD Area : 40.0m x 30.0m Type : Surface at EL m 18. ESTIMATED COST Completion Cost at May, 2010 price level : Rs Cr. 19. POWER BENEFITS Energy generation in 90% dependable : year MU 20. FINANCIAL ASPECTS IRR : 12.80% Average DSCR : TARIFF Levelised Tariff : Rs. 4.25/Kwh First Year : Rs. 5.20/Kwh 22. CONSTRUCTION PERIOD Construction Period (including 12 months for pre-construction activities) : 74 months WAPCOS Limited 2-13

31 2.6 LAND REQUIREMENT The total land required for the project is ha. The details are given in Tables-2.2 and 2.3. S. No TABLE-2.2 Land requirement for Nyamjang chhu hydroelectric project Component Village Private Total Community Land Land Land (ha) (ha) (ha ) Submergence Area ( Left Bank Soksen up to Barriage) Submergence Area ( Right Bank Lumpo up to Barriage) Submergence Area ( River area up to Barriage) Upstream Headworks Soksen and Lumpo (50-50) Soksen Soksen Kyaleyteng Shakti Gispu Head Race Tunnel 10 Sherbang Kherteng Phoomang Bagar Adits - 1 Kyaleyteng Adits - 2 Shakti Adits - 3 Shakti Adits - 4 Shakti Adits - 5 Sherbang Adits - 6 ( equally Kherteng/Pho 19 in three villages) omang/bagar Kherteng/Pho Adits omang/bagar Adits - 8 Kungba Adits - 9 Kherteng Tail Race Tunnel Kherteng WAPCOS Limited 2-14

32 S. No. Component Village Private Land (ha) Community Land (ha) Total Land (ha ) 24 G IB Kherteng MAT Kherteng Power House Kherteng Surge Shaft (equally in three villages) Kherteng, Phoomang, Bagar Pressure Shaft (equally in three villages) Kherteng, Phoomang, Bagar Switchyard Kherteng Muck disposal Muchat Sites M-1 31 M-2 Muchat M-3 Kyaleyteng M-4 Shakti M-5 Shakti (BTK) M-6 Shakti (BTK) M-7 BTK M-8 BTK M-9 Shakti (BTK) M-10 Sherbang M-11 Sherbang M-12 Sherbang M-13 Kherteng M-14 Kumba M-15 Kumba Colonies Sherbang Labour Camps ( equally in three Kyaleyteng, Kherteng, villages ) Sherbang 47 Workshop,Centerl ized store and Fabrication yard Kherteng Explosive Magazines ( 2 nos) (50-50) Crusher,Batching plant and aggregate Storage (2 nos )(50-50) Sherbang / Kyaleyteng Kerteng / Shakti WAPCOS Limited 2-15

33 S. No Component Contractor colonies (Temp )equally in three villages Adit Portals ( 1 to 9 ),TRT,Cables tunnel Portals (for cover ) Storage area at different works sites Access Roads to Query 500 mts each Access Roads to Inlet Portal ADIT 1 ( 15 mtrs RoW) Access Roads to Adits - 2, 3 Access Roads to Adits - 5 Access Roads to Adits - 6 Access Roads to Adits - 7 Access Roads to Adits - 8 Access Roads to Adits - 9 Access Roads to MuckDumpng 3 Access Roads to MuckDumpng 4 Access Roads to Surge Shaft Access Roads to M.A.T. Access Roads to Cables tunnel Access Roads to T.R.T Quarry (Q -2 to Q-7 ) Village Kherteng/She rbang/kyaleyt eng respective villages of Adits Socksen,resp ective villages of Adits, s.shaft, MAT, GIB &TRT Socksen, Muchat,Shakti, Sherbang, Lumla Private Land (ha) Community Land (ha) Total Land (ha ) Kyaleyteng Shakti Sherbang Kherteng/Pho omang/bagar Kherteng/Pho omang/bagar Kungba Kherteng Kyaleyteng Shakti Kherteng Kherteng Kherteng Kherteng Total WAPCOS Limited 2-16

34 TABLE-2.3 Ownership status of land to be acquired for Nyamjang chhu hydroelectric project S. No. Type of land Area (ha) 1 Private land Community land Total INFRASTRUCTURE FACILITIES The project area is located about 50 Km from district headquarter at Tawang. The area is sparsely populated and lacks adequate residential and telecommunication facilities. The project site is accessible from Guwahti via National Highway, state highway and district level road. For construction purpose access to various project components is required. Also, the existing roads and infrastructure facilities need to be improved. The total infrastructure works envisaged for permanent and temporary access include: Project Roads and Bridges. Construction power facilities Residential and non-residential buildings including electricity, water supply and sanitary facilities. Telecommunication and other facilities Access Roads And Bridges The entire project site is well approachable by road network available from Guwahati/Tezpur to Tawang/Lumla/Zimithang via Bhalukpong, Bomdila and Sela pass. Guwahati is connected to Tezpur by National Highway (NH-52). The distance between Guwahati and Tezpur is about 170 km. The distance of Tawang, Lumla and Zimthang from Guwahati is about is about 520 km, 575 km and 625 km respectively. From Tezpur approach to the Project site is through Bhalukpong which is a border town at Assam Arunachal border. Bhalukpong is connected to Tezpur by 60 km long road passing through Balipara Bhalukpong is connected to Lumla through Bomdila, Dirang, Sela Pass and Jung. From Lumla, diversion site at Zimithang is approachable by 40 km long road maintained by border roads. The entire road network from Bhalukpong to Tawang/Lumla/Zimithang is maintained by BRTF. Construction material, heavy equipment and machinery required for the project will be brought to project site through this existing road network. Heavy equipment, if imported from countries other than India, would have to be transported from Kolkata to project site via Siliguri. WAPCOS Limited 2-17

35 While going to project site along this road network Sela Pass is to be crossed, which is located at an elevation of ft and most of the time in a year is covered with snow. Existing road network passes through Bomdila town, which is very congested and has a very steep gradient. Considering the above constraints the project area is also proposed to be approached through Trashigaon Lumla road via Bhutan which is under construction and is likely to be completed by the time the project is expected to be taken up for construction. This road network is conncted to Guwahati via Rangiga (Assam) Samdrup Jongkhar (Bhutan) Trashigaon route. The total length of this route from Guwahati to Lumla is 575 km. It might therefore greatly benefit the project construction as the distance between Guwahati to Lumla along this oad would be further shortened. The nearest airport is at Tezpur and Guwahati which are about 400 km and 570 km from site. Helicopter service is also available from Guwahati up to Tawang on daily basis. Project Roads A network of new roads is required to facilitate completion of the project as per anticipated time schedule. Major components like Barrage, Power House, Surge Shaft and Permanent Colonies for the project near village Kharteng and Zimithang will require construction of new roads on the left bank. A bridge has to be constructed across river Nyamjang Chhu upstream of the existing BTK bridge to approach adits to HRT from the existing road on right bank. The total length of new roads to be constructed has been estimated as km as detailed in Table-2.4. TABLE-2.4 List of new roads to be constructed Connecting details Length (km) Length of road to reach various adits and other project 54.5 components Length of road from existing road to Power House 2.5 Length of internal road from existing road at Barrage on 3.0 Right bank and new Road on Left bank Total 60.0 Apart from the above major roads about 40 km of road network will be required for approach to the various muck dumping yards. About 120 km of existing roads in the project area from tawang to Zimithang may require strengthening and widening including bridges and cross drainage works. WAPCOS Limited 2-18

36 Transportation And Transport Limitation For transporting major equipment such as turbines, generators, main transformers, spherical valves, etc, road link is available up to project site from other locations of India through Assam State. The National Highway in India is designed for class 70R loading as per Indian Road Congress standard and is capable of carrying 70 ton load. The standard further specifies that up to 100 tons can be transported by trailors with multiple wheels. The existing road from Tezpur to Lumla/Zimithang is of state highway specifications. Beyond the present road upto Tawang is of the class 9N. The details are as follows: Classification - 9 N (as per BRO standards) Culverts designed for - 18/24 Minimum Radius m Carriage way m Formation width m This road also requires significant widening and strengthening along with construction of new bridges and culverts designed to carry the load of heavy machinery and equipment required for the project construction Construction Power The maximum power required for constructions activities is estimated considering capacity of electrically driven machines/equipment and requirement of lighting, varies during the construction schedule and also depends on construction methodology. It is assessed that about 10 MW of power would be required during peak construction period. However, construction power requirements during the initial two years would be about 5 MW. The power requirement would be met through installation and operation of dedicated DG sets Power Supply Facilities Presently power requirements in the project area are being met through 33/11KV lines from Tawang. The project area experiences frequent power cuts and break-downs. Power requirement for project construction is not suitable to meet the existing system of power supply in the region. A new single circuit 33/11KV transmission line is also proposed from Tawang to Lumla and is under planning stage. Even after up gradation the power supply system will not be WAPCOS Limited 2-19

37 suitable to meet the dedicated power demand from the project during construction stage Telecommunication Facilities The telecommunication facilities in the project area comprise of fixed line and WLL services from BSNL. Mobile network is not available in the area and nearest mobile network is available at Tawang and is served only by BSNL. For effective coordination among various work sites, workshop, colonies, stores, design office, head office, etc. and a reliable tele-communication network is necessary. An electronic automatic telephone exchange with a capacity of about 100 lines is proposed at project head quarters at Lumla. The internal telephone system would be maintained by the project. Telecommunication link outside the project area would be provided by upgrading the existing BSNL network. A wireless V-Sat system is also proposed for linking the project site with Zimithang, Namestring, Lumla, Tawang, Bhalukpong, Itanagar and Noida. After completion of construction activities, the telecommunication network is proposed to be continued so as to serve during operation and maintenance stage. A VHF wireless network is also proposed to be established to connect various project sites, Guwahati and Tezpur. This will be mainly utilized for the construction purpose and will be scaled down after commissioning. It is also proposed that the project area may be connected by the mobile network as available in other parts of the state Project Colonies/Buildings The Residential and non-residential facilities are required during construction and O&M phase of the project. The same will be met by constructing suitable colonies near Lumla, Kharteng,and Zimithang villages. Total area required for the permanent buildings has been estimated as m 2 and for temporary buildings as m 2. The temporary colonies would be utilized during construction of the project and permanent colonies would be utilized for both i.e, during construction and maintenance of the project. The water supply requirement shall be met with from the flow of near by streams by gravity flow. The flow requirement sufficient to meet the likely water demand is about 50lps. WAPCOS Limited 2-20

38 The entire building construction program would be suitably phased to match with the construction activities. Priority would be given to the construction of field hostel, stores and temporary residential and non-residential buildings. It is also planned to have liaison facilities at Guwahati, Tezpur, Itanagar, Bomdilla and at Bhalukpong. A suitable storage area would also be made in Bhalukpong to keep the buffer for the stock of construction materials for the monsoon period etc. Guest Houses are also planned at Bhalukpong & Dirang. Residential Non-residential Stores Recreation facilities Construction WAPCOS Limited 2-21

39 3.1 INTRODUCTION CHAPTER-3 METHODOLOGY ADOPTED FOR THE EIA STUDY Standard methodologies of Environment Impact Assessment have been followed for conducting the CEIA study for the proposed Nyamjangchhu hydroelectric project. A brief description of the methodology adopted for conducting the CEIA study for the proposed Nyamjangchhu hydroelectric project is outlined in the present chapter. The information presented in this Chapter has been presented through various primary as well as secondary sources. 3.2 STUDY AREA The study area considered for the CEIA study is given as below: Submergence area Area within 10 km of the periphery of the submergence area Area to be acquired for siting of various project appurtenances. Area within 10 km of various project appurtenances Catchment area intercepted at the barrage site The study area is shown in Figure SCOPING MATRIX Scoping is a tool which gives direction for selection of impacts due to the project activities on the environment. As a part of the study, scoping exercise was conducted selecting various types of impacts which can accrue due to hydroelectric project. Based on the project features, site conditions, various parameters to be covered as a part of the EIA study were selected. The results of Scoping analysis are presented in Table-3.1. TABLE-3.1 Scoping Matrix for EIA study for the proposed Nyamjangchhu Aspects of Environment Likely Impacts A. Land Environment Construction phase - Increase in soil erosion from various construction and quarry sites - Pollution by construction spoils - Acquisition of land for labour camps/ colonies - Solid waste generated from labour camps/colonies WAPCOS Limited 3-1

40 Aspects of Environment Likely Impacts Operation phase - Acquisition of land for various project appurtenances - Loss of agricultural and forest land due to acquisition of land for various project appurtenances B. Water resources & water quality Construction phase - Impact on water quality of receiving water body due to disposal of runoff from construction sites carrying high sediment level. - Degradation of water quality due to disposal of effluent from labour, camps/colonies Operation phase - Modification of hydrologic regime due to diversion of water for hydropower generation C. Aquatic Ecology Construction phase - Increased pressure on riverine fisheries as a result of indiscriminate fishing by the immigrant labour population. - Reduced productivity due to increase in turbidity levels as a result of disposed off waste water from construction sites and labour camps/colonies. Operation phase - Impacts on spawning & breeding grounds in the stretch downstream of dam site to fail race disposal site. - Degradation of riverine ecology - Impacts on migratory fish species - Impact on aquatic ecology due to reduction in flow downstream of the dam site upto tail race disposal site. D. Terrestrial Ecology Construction phase Operation phase - Increased pressure from labour to meet their fuel wood requirements during project construction phase - Adverse impacts on flora and fauna due to increased accessibility in the area and increased level of human interferences - Loss of forest due to siting of various project appurtenances - Impacts on wildlife movement due to the project - Impacts on wildlife habitats due to acquisition of forest and other categories of land for various project appurtenances. WAPCOS Limited 3-2

41 Aspects of Environment E. Socio-Economic Aspects Construction phase Operation phase F. Air Pollution Likely Impacts - Increased employment potential during project construction phase - Development of allied sectors leading to greater employment - Pressure on existing infrastructure facilities. - Cultural conflicts and law and order issues due to migration of labour population - Acquisition of private land, home- Stead and other private properties - Loss of community properties - Impacts on archaeological and cultural monuments, if any - Impacts on mineral reserves, if any Construction Phase - Impacts due to emission as a result of fuel combustion in various construction equipment - Impacts due to emission as a result of increased vehicular movement for transportation of men and material during project construction phase - Fugitive envisions from various sources - Impacts due to emissions from DG set G. Noise Pollution Construction Phase - Noise due to operation of various construction equipment - Noise due to increased vehicular movement - Impacts due to blasting - Increased noise levels due to operation of DG set H. Public Health Construction Phase - Increased incidence of water related diseases - Transmission of diseases by immigrant labour population Operation phase - Increased incidence of vectorborne diseases Based on the Scoping matrix, the environmental baseline data has been collected. The project details have been superimposed on environmental baseline conditions to understand the beneficial and deleterious impacts due to WAPCOS Limited 3-3

42 the construction and operation of the proposed Nyamjangchhu hydroelectric project. 3.4 DATA COLLECTION Physico-Chemical Aspects Primary surveys have been conducted for three seasons namely, monsoon, post-monsoon and pre-monsoon seasons. The data has been collected for flora, fauna, forest types and ecological parameters, geological and soil features. During these surveys data and information was collected on physico-chemical, biological and socio-economic aspects of the study area. In addition, detailed surveys and studies were also conducted for understanding bio-diversity in the study area. As a part of the EIA study, primary data has been collected by WAPCOS Ltd. for three seasons. However, as a part of TOR clearance, the project proponents were asked to get the field studies conducted by another agency. The project proponents selected RS Envirolink Technologies Private Limited as the other agency, who collected data for three seasons. TABLE-3.2 Details of field studies conducted as a part of CEIA studies Agency Season Months WAPCOS Ltd. Monsoon August-September 2007 Winter December 2007 January 2008 Summer April May 2008 RS Envirolink Summer April May 2008 Technologies Private Monsoon July August 2008 Limited Winter November December 2008 Geology The regional geology around the project area highlighting geology, stratigraphy, etc. have been covered in the EIA Report, as per the available information in the Detailed Project Report (DPR) of the project. Hydrology Hydrological data for river Nyamjangchhu as available in the Detailed Project Report was collected and has been suitably incorporated in the Comprehensive EIA study. WAPCOS Limited 3-4

43 Seismo-tectonics The regional seismo-tectonics around the project area highlighting seismicity have been covered in the EIA Report, as per the available information in the Detailed Project Report (DPR) of the project. Landuse pattern Landuse pattern of the study area as well as the catchment area was carried out by standard methods of analysis of remotely sensed data and followed by ground truth collection and interpretation of satellite data. For this purpose digital satellite data was procured from National Remote Sensing Agency, Hyderabad, IRS-P6 LISS-IV. The data was processed through ERDAS software package available with WAPCOS. Soil The soil quality was monitored at various locations in the catchment area. The monitoring was conducted for three seasons as detailed in Table-3.2. The parameters monitored were: ph Electrical Conductivity Organic Matter Sodium Phosphates Potassium Nitrates Cation Exchange Capacity Sulphates Chlorides Particle Size Distribution Texure content Bulk density Water holding capacity Water Quality The existing data on water quality has been collected to evaluate river water quality on upstream and downstream of the project site. The water quality was monitored for various seasons as listed in Table-3.2. The water samples were collected from the study area and analyzed for physico-chemical parameters which are listed in Table-3.3. WAPCOS Limited 3-5

44 TABLE-3.3 Water quality parameters analysed as a part of the field studies ph Zinc Electrical Conductivity Total Suspended Solids Total Dissolved Solids Cadmium Sulphates Magnesium Chlorides Lead Nitrates Manganese Phosphates Fluorides Sodium Hardness Potassium DO Calcium BOD Copper COD Iron Oil & grease Total Coliform Ambient air quality The ambient air quality was monitored at three locations in the study area. Monitoring was conducted for three seasons as listed in Table-3.2. The frequency of monitoring for each season was twice a week for four consecutive weeks. The parameters monitored were Suspended Particulate Matter (SPM), Respirable Particulate Matter (RPM), Sulphur-dioxide (SO 2 ) and Nitrogen Oxides (NOx). Ambient Noise level As a part of the EIA study noise level was monitored at various locations in the study area. Monitoring was conducted for various seasons as listed in Table-3.2. At each station, hourly noise level was monitored during day time. Further day time equivalent noise level was estimated Ecological Aspects Terrestrial Ecology Flora Data on forest type legal status and their extent in the catchment and study area has been collected from the forest department. The other relevant data on bio-diversity economically important species medicinal plant, rare and endangered species in the study area and its surroundings have been collected from secondary sources like research institute forest and wildlife department. In addition field studies were conducted to collect data on various aspects in the study area. The sampling sites were selected based on topography and floristic composition. The various aspects studied were floral density frequency and abundance of species of trees, shrubs, herbs and grasses. Plants of economical WAPCOS Limited 3-6

45 species and medicinal use and endangered species were also identified as a part of the study. The monitoring was conducted for various seasons listed in Table Fauna The faunal assessment has been done on the basis secondary data collected from different government offices like forest department, wildlife department, fisheries department etc. The presence of wildlife was also confirmed from the local inhabitants depending on the animal sightings and the frequency of their visits in the catchment area. In addition review of secondary data was another source of information for studying the fauna of the area. In addition, sightings of faunal population during ecological survey and then field studies were also recorded as a part of the data collection exercise. Aquatic Ecology and Fisheries Water samples from river Nyamjangchhu were also collected as a part of field studies. The density and diversity of periphyton and phytoplanktons, species diversity index and primary productivity etc. were also studied. The field studies were conducted for various seasons as listed in Table-3.2. The secondary data pertaining to fisheries in river Nyamjangchhu was collected from Fisheries Department and through literature review as well. Fishing was done at various sites in the project area and river stretches both upstream and downstream of the dam site of proposed hydroelectric project to ascertain the dispersal pattern of fish species. Identification and measurements of all the fish catch was done and an inventory of the fish species was also prepared. Various migratory species and the species to be affected due to conversion of lentic to lotic conditions as a result of commissioning of the proposed project were also identified Socio-economic Aspects Demography The demographic and socio-economic characteristics of the submergence area as well as the study area have been studied through primary as well secondary sources. Detailed socio-economic census survey was conducted in the project affected villages due to the proposed project. Collection of data was completed at two levels - at village/ block and individual household level. The socioeconomic survey at the village/ block level was aimed at finding out the status and extent of amenities and resources at the disposal of villages/ blocks. The WAPCOS Limited 3-7

46 household surveys were conducted with the main aim of evolving and preparing compensatory and rehabilitation packages for families who would be rendered houseless, landless and whose part of land would be acquired for various project activities. Based on the assessment of demographic profile of Project Affected Families (PAFs), Resettlement and Rehabilitation Plan using guidelines and norms as per National Policy on Resettlement and Rehabilitation (2007) was formulated. 3.5 SUMMARY OF DATA COLLECTION The summary of the data collected from various sources is outlined in Table-3.4. TABLE-3.4 Summary of data collected for the Comprehensive EIA study Aspect Mode of Parameters Frequency Source Data monitored collection Meteorology Secondary Temperature, humidity, rainfall - India Meteorological Department (IMD) Water Resources Secondary Flow, Design hydrograph and design flood hydrograph - Detailed Project Report (DPR) Water Quality Primary Physicochemical and biological parameters Ambient quality air Primary RPM, SPM, SO 2, NOx Noise Primary Hourly noise and equivalent noise level Three seasons Three seasons Three seasons Field studies for monsoon, winter and summer seasons by two agencies Field studies for monsoon, winter and summer seasons by two agencies Field studies for monsoon, winter and summer seasons by two agencies Landuse Primary and secondary Landuse pattern - NRSA and Ground truth Studies Geology Secondary Geological - Detailed Project WAPCOS Limited 3-8

47 Aspect Mode of Data collection Soils Terrestrial Ecology Aquatic Ecology Socioeconomic aspects Primary and secondary Primary and Secondary Primary and secondary Parameters monitored characteristic s of the study area Physicochemical parameters Floral faunal diversity and Presence and abundance of various species Demographic and socioeconomic, Public health cultural aspects Frequency Source Report (DPR ) Three Field studies for seasons monsoon, winter and summer seasons by two agencies Three Field studies for seasons monsoon, winter and summer seasons by two agencies Secondary data as available with the Forest and Wild life Department Three Field studies for seasons monsoon, winter and summer seasons by two agencies Secondary data as available with the Fisheries Department - Field studies for PAFs, secondary data collection from Revenue Department and literature review. 3.6 IMPACT PREDICTION Prediction is essentially a process to forecast the future environmental conditions of the project area that might be expected to occur because of implementation of the project. An attempt was generally made to forecast future environmental conditions quantitatively to the extent possible. But for certain parameters, which cannot be quantified, general approach has been to discuss such intangible impacts in qualitative terms so that planners and decision-makers are aware of their existence as well as their possible implications. Impact of project activities has been predicted using mathematical models and overlay technique (super-imposition of activity on environmental parameter). For intangible WAPCOS Limited 3-9

48 impacts qualitative assessment has been done. The environmental impacts predicted are listed as below: - Loss of land. - Displacement of population due to acquisition of private and community properties. - Impacts on hydrologic regime. - Impacts on water quality. - Increase in incidence of water-related diseases including water-borne and vector-borne diseases. - Effect on riverine fisheries including migratory fish species. - Increase in air pollution and noise level during project construction phase - Impacts due to sewage generation from labour camps - Impacts due to acquisition of forest land - Impacts due to increase in terrestrial and aquatic ecology due to increased human interferences during project construction and operation phases 3.7 ENVIRONMENTAL MANAGEMENT PLAN AND COST ESTIMATES Based on the environmental baseline conditions and project inputs, the adverse impacts were identified and a set of measures have been suggested as a part of Environmental Management Plan (EMP) for their amelioration. The management measures have been suggested for the following aspects: - Compensatory afforestation and bio-diversity conservation plan - Catchment Area Treatment - Fisheries Management Plan - Public health delivery system - Environmental management in labour camp - Muck Management Plan - Restoration of quarry sites and landscaping of construction sites - Management of Impact due to construction of road - Greenbelt development plan - Control of Air Pollution - Measure for noise control - Water pollution control The expenditure required for implementation of these management measures has also been estimated as a part of the EMP study. 3.8 RESETTLEMENT AND REHABILITATION PLAN As a part of the CEIA study, a socio-economic survey of project affected families was conducted. As a part of the survey, information on family profile, occupational profile, income, land holding, crop grown, assets owned, etc. was collected. Based on the findings of the survey and the norms of outlined in National Policy for Resettlement and Rehabilitation (NPRR) 2007, Resettlement and Rehabilitation Plan for the project affected families has been formulated. WAPCOS Limited 3-10

49 3.9 CATCHMENT AREA TREATMENT PLAN As a part of the CEIA study, a catchment area treatment plan for the catchment area intercepted at the project site has been formulated. Various subwatersheds have been categorized into different erosion categories, as per Silt Yield Index (SYI) method. For high and very high erosion categories, a catchment area treatment plan comprising of engineering and biological measures has been formulated TRIBAL DEVELOPMENT PLAN In view of the Ministry of Tribal Affairs Strategy for development: the TSP Approach and Plans/Programs of the ministry, various measures for Tribal Development Plan has been suggested. These measures are in addition to the measures outlined under Resettlement and Rehabilitation Plan and Area Development Activities ENVIRONMENTAL MONITORING PROGRAMME It is necessary to continue monitoring of certain parameters to verify the adequacy of various measures outlined in the Environmental Management Plan (EMP) and to assess the implementation of mitigative measures. An Environmental Monitoring Programme for critical parameters has been suggested for implementation during project construction and operation phases. The staff along with necessary equipment and agencies to be involved for implementation of the Environmental Monitoring Programme and costs have also been indicated. WAPCOS Limited 3-11

50 CHAPTER 4 HYDROLOGY 4.1 BASIN DESCRIPTION The river Nyamjang Chhu runs through north-western part of Arunachal Pradesh and flows mostly in a North - South direction. It is a major tributary of the westerly flowing Tawang Chhu within the State of Arunachal Pradesh. Nyamjang Chhu originates in China at an elevation of about ±6400 m and flows through Tibet before entering India at Khinzemane. It flows southwards crossing into Arunachal Pradesh and continues on a southerly course, parallel with the Indo-Bhutanese border, for a distance of about 40 km to its confluence with the Tawang Chhu near Lumla, Kumba villages. Tawang Chhu flows beyond Lumla village in a westerly direction into Bhutan as Gamri Chhu and ultimately becomes a tributary of the Manas and Brahmaputra rivers. Major tributaries of river Manas include Tawang Chhu, Nyamjang Chhu, Kuri Chhu, Khulong Chhu, Amri Chhu and Sheri Chhu. Nyamjang Chhu is a perennial river with its main source of water being the south west monsoon and snow melt contribution of Himalayan glaciers. The general pattern of river flow shows a large variation with high flows in the months of June to September and lower flows in the remaining months. The total length of Nyamjang Chhu from its origin in the Tibetan plateau at an elevation of about 6400 m, to its confluence with the Tawang Chhu at an elevation of about about 1036 m is about 125 km. The upper portion of the river, comprising about 85 km, is in Tibet and remaining 40 km is in India. In India, the Nyamjang Chhu flows through rugged mountainous terrain with an average gradient of 1 in 30. The river enters India at approx. EL 2220 m near village Khinzemane and covers a distance of about 10 km up to Zimithang. It meets Namka Chhu 2.41 km south of Khinzemane and Sumta Chhu joins Nyamjang Chhu near Zimithang. The river is flat in the Zimithang area for a stretch of almost 2.5 km. After this it again runs through steep slopes up to confluence with Tawang Chhu. Eight nallas including Taksang Chhu and Gomkarang Chhu join Nyamjang Chhu between Zimithang and its confluence with Tawang Chhu. These contribute to the discharges of the Nyamjang Chhu all along this stretch. The river bed elevation at Zimithang village is about EL m and that at the confluence is about EL about 1036 m. A gross head of about m can therefore be exploited for development of hydro power potential of the basin. The total catchment area of the Nyamjang Chhu up to the confluence with Tawang Chhu is about 3170 km 2. The catchment area upstream from Zimithang Village (barrage site) is about 2650 km 2. Out of this 2650 km 2, about 1945 km 2 of catchment area is above permanent snow line of EL 4500 m and 705 km 2 of catchment area receives precipitation in the form of rainfall. A Satellite image of the Nyamjang Chhu catchment is shown in Figure 4.1.The catchment area map showing drainage network is shown in Figure 4.2. The delineation of snow fed and rainfed areas in the catchment is shown in Figure-4.3. During its course from Zimithang to its confluence with Tawang Chhu, Nyamjang Chhu is joined by eight major nallas. Two nallas namely Sumta Chhu and Taksang Chhu carry significant perennial discharges and have catchment areas of 100 km 2 and 154 km 2 respectively. Sumta Chhu is a right bank tributary of Nyamjang Chhu while Taksang Chhu is located on the left bank. It is proposed to divert the perennial flow of Taksang Chhu into the headrace tunnel of Nyamjang Chhu HEP to utilise the flow for power generation. The catchment area of Taksang Chhu upto the proposed diversion site at EL m is 154 km 2. Accordingly the flow in Nyamjang Chhu is computed including the catchment area of Taksang Chhu upto the proposed diversion site. Thus, the total catchment area including Taksang Chhu is 2804 km 2. WAPCOS Limited 4-1

51 4.2 Water Availability Study Hydrological data of Nyamjang Chhu is available for a period of only 18 months from December Discharge data of Tawang river located east of Nyamjang Chhu and Kuri Chhu located west of Nyamjang Chhu is available for 7 years and 16 years respectively. In the absence of long term discharge data for Nyamjang Chhu, the hydrological data of Tawang Chhu and Kuri Chhu have been used in the DPR to estimate a long term flow series for Nyamjang Chhu. Barrage Location Confluence Point of Nyamjang Chhu & Tawang Chhu WAPCOS Limited 4-2

52 NJC Hydropower Limited Figure 4.1 Satellite Image of Catchment Area of Nyamjang Chu Barrage Location Confluence Point of Nyamjang Chu & Tawang Chu WAPCOS Limited 4-3

53 Figure -4.2 WAPCOS Limited 4-4

54 WAPCOS Limited 4-5

55 4.2.1 Rainfall Data The India Meteorological Department (IMD) has confirmed that no rainfall data is available for the Nyamjang Chhu river catchment. Out of the available IMD gauging sites in the region, the stations nearest to the project catchment are at Dirang, Bomdilla and Bhalukpong. The location of these stations is shown in the Figure 4.4. Figure 4.4: Locations of Dirang, Bomdilla and Bhalukpong Dirang Not to Scale The rainfall data of the rain gauge stations at Bhalukpong and Dirang is given in Tables- 4.1 and 4.2 respectively. WAPCOS Limited TABLE-4.1 Rainfall Data at Bhalukpong Monthly Total Rainfall (mm) Annual Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall Avg

56 TABLE-4.2 Rainfall Data at Dirang Monthly Total Rainfall (mm) Annual Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall Avg Gauge and Discharge Data No gauge and discharge measurements (G&D) had been carried out on Nyamjang Chhu prior to the agreement with BEL. In December 2006, after a reconnaissance survey of the Nyamjang Chhu valley, discharge measurement site was selected. The initial G&D site was established about 1.5 km upstream of the BTK Bridge. The daily discharge data at this site is being monitored continuously and is presented in Table-4.3. The 10 -daily mean flows (cumecs) for observed flow data for Nyamjang Chhu at BTK bridge G&D site is given in Table-4.4. WAPCOS Limited 4-7

57 TABLE-4.3 Observed Daily Flow for Nyamjang Chhu At BTK Bridge G&D Site Year Date Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May 1 * * * * * * * * 2 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 8.96 * * * * * 22 * * * ` * 8.68 * * * * * 9.09 * * * * * 9.07 * * * * * * * * * * * * WAPCOS Limited 4-8

58 Year Date Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May * * * * * * * * * * * * * * * * * * * * * * * * * Gaps indicate suspension of observation due to inclement weather condition WAPCOS Limited 4-9

59 EIA study for Nyamjangchu TABLE daily mean flows (cumecs) for observed flow data for Nyamjang Chhu at BTK bridge G&D site Discharge Year Month (cumec) I DEC II III I JAN II III I FEB II III I MAR II III I APR II III I MAY II III I JUN II III I JUL II III I AUG II III I SEP II III I OCT II III I NOV II III I DEC II 9.46 III 9.18 I 8.93 JAN II 8.88 III 2008 I FEB II 8.86 III 8.74 WAPCOS Limited 4-10

60 Year Month MAR APR MAY EIA study for Nyamjangchu Discharge (cumec) I 8.62 II III I II III I II III In the year 2007, discharge measurement at two more locations has been started by BEL. One site is located near Zimithang village (diversion site) and another site is located at Namstering Bridge (near powerhouse site).the details of discharge data available for the Nyamjang Chhu and the adjacent subbasins is indicated in Table-4.5. S. No Station BTK Bridge Muruga Bridge Yusum Village TABLE-4.5 Discharge Data Availability Catchme Name of Type of nt Area River (km 2 Data ) Nyamjang Chhu Tawang Chhu Tawang Chhu Kurizampa Kuri Chhu Kuri Chhu HEP (Existing Power plant) Kuri Chhu 9135 Observed Daily G&D Observed Daily G&D Observed Daily G&D Observed Daily G&D Estimated from Plant operation Period of Availability December 2006 onwards Nov 1998 to Nov 2005 Dec 2006 to May 2007 July 2003 to Feb 2006 May 1991 to Apr 2007 (2005 data missing) Jan 2003 to Nov 2007 WAPCOS Limited 4-11

61 EIA study for Nyamjangchu TBALE DAILY FLOW SERIES AT NYAMJANG CHU HEP BASED ON TAWANG FLOWS (FINAL SERIES CONSIDERED FOR FLOW DURATION STUDY) Average WAPCOS Limited 4-12

62 EIA study for Nyamjangchu Sedimentation Data Site specific observed sediment data is not available. However, sedimentation rate at Muruga Bridge and Yusum Site in the adjacent Tawang Chhu sub basin has been reported as and 0.01 ha-m/km 2 /year respectively in the Pre Feasibility Report for Tawang HEP prepared by National Hydro Power Corporation (NHPC). The above sedimentation rates are based on analysis of observed silt data for the period of May 2001 to May 2005 at Muruga Bridge and Aug 2002 to May 2005 at Yusum Site. The above silt rates are based on data of limited period and appear to be on the lower side when compared to other Himalayan projects. Therefore, these silt rates may not be considered to represent long term average annual silt rate. However, Central Water Commission recommends an average annual rate of siltation of ha-m/km 2 for the Himalayan Region (Indus, Ganges and Brahmaputra Basin). Ref Compendium of Silting of Reservoirs of India, Central Water Commission, New Delhi, January Methodology and Calculations for Long Term Series of Nyamjang Chhu The hydrological observation at the project catchment has been started in Dec IMD has reported that no rainfall data is available for the Nyamjang Chhu catchment. In such cases, standard practice is to attempt various alternative approaches utilising all available hydrometeorological information of the neighbouring sub-basins in order to assess design hydrological parameters of the project basin. Long term flow data is available on the Kuri Chhu in the west and on the Tawang Chhu in the east of the project basin. In order to generate a continuous long term flow series for Nyamjang Chhu basin, studies have been carried out based on catchment area proportion and runoff-runoff correlation among the available concurrent flow series of Rivers Kuri Chhu, Tawang Chhu and Nyamjang Chhu. The 10 daily flow series at Nyamjangchu HEP site based on Tawang discharge data is given in Table-4.6. WAPCOS Limited 4-13

63 EIA study for Nyamjangchu S. No. 4.3 Dependable flow analysis Dependable Flow The hydrological dependability of flow volumes of Nyamjang Chhu at Zimithang (Barrage Site) from for the recommended series including the flow from Taksang Chhu is presented in Table -4.7 below (the year 1991 is excluded due to missing flow values from January to May). Also the flow data of hydrological dependable years is shown in Table-4.8. Years TABLE-4.7 Dependable Flow Analysis for NJCHEP Series Unrestricted Annual Energy Inflow Rank Dependability (MU) (MCM) % % % % % % % % % % % % % % % % % Remarks 50% Dependable Year 75% Dependable Year 90% Dependable Year WAPCOS Limited 4-14

64 EIA study for Nyamjangchu Period/Year JUN JUL AUG SEP OCT NOV DEC JAN FEB MAR APR MAY Annual Inflow (MCM) TABLE-4.8 Hydrological Dependable Years 90% 75% 50% Dependable Dependable Dependable Year Year Year Average Flow I II III I II III I II III I II III I II III I II III I II III I II III I II III I II III I II III I II III WAPCOS Limited 4-15

65 EIA study for Nyamjangchu The Flow duration curve for the flow series at Zimithang site from is shown below in Figure-4.5 and Table-4.9 shows the main values from the duration curve. Figure-4.5: Flow Duration Curve for Nyamjang Chhu (for catchment area 2804 sq km: including Taksang Chhu) For Period: Jun 91 May 08 Exceedance Probability (%) TABLE-4.9 Characteristics of Flow Duration Curve Discharge (cumec) Exceedance Probability (%) Discharge (cumec) WAPCOS Limited 4-16

66 EIA study for Nyamjangchu 4.4 DESIGN FLOOD STUDIES Estimation of design flood is one of the most important components of planning, design and operation of various types of water resources projects. Inflow design flood is required to finalize different design parameters of any hydraulic structure like dam, barrage, etc. Inflow design flood is the flood for which, the performance of the dam etc. should be safe against overtopping and structural failure. For a diversion structure, design flood should be considered based on following methods. i) Hydrometeorological approach (unit hydrograph method) ii) Flood frequency analysis As per DPR, the design flood estimated using Hydrometeorological approach is given in Table TABLE-4.10 Design Flood Values by Hydrometeorological Approach Single Bell Storm Distribution Two Bell Storm Distribution Standard Project Flood (SPF) Design Flood (m 3 /s) The estimated design flood values by frequency analysis based on the annual peaks transposed from Kuri Chhu in catchment area proportion for various return periods for the diversion structure are given in the Table TABLE-4.11 Design Flood Values by Frequency Analysis Return Period Design Flood (m 3 /s) 50 year flood year flood year flood year flood 2173 WAPCOS Limited 4-17

67 EIA study for Nyamjangchu From the above studies, the 100 year return period design flood value from flood frequency analysis is 1764 cumec and by the hydrometeorological approach SPF is of 3400 cumec. As per the DPR, design flood value obtained by hydro-meteorological approach is recommended for preliminary design purposes as it is on conservative side as compared to flood frequency approach. The recommended design flood is given in Table TABLE-4.12 Recommended Design Flood Values Design Return Recommended Purpose Flood m 3 /s Period Design of barrage and determination of free 3,400 SPF board Recommendation of Diversion Flood Flood frequency analysis has been used for the estimation of diversion flood during the non-monsoon season. The 25 year return period peak value for non-monsoon period by Gumbel Distribution Method is 468 cumec say 500 cumec and by transposition of observed maximum daily non-monsoon discharge of Kuri Chhu recorded at Kurizampa station to Zimithang is cumec. The inflow design flood for river diversion works is the greater of the following: Flood with a return period of 25 years derived with non monsoon peak discharge values. Highest observed non monsoon discharge in the river. Thus, as per the above criteria, the 25 year non-monsoon return period flood value of 500 cumec being on the higher side as compared to highest observed non monsoon discharge of cumec, 500 cumec is recommended as design flood for the river diversion works. The percentage of risk involved based on the duration of the construction period of the diversion structure (coffer dam) is given in Table WAPCOS Limited 4-18

68 EIA study for Nyamjangchu Table-4.13 Percentage of risk involved based on the duration of the construction period of the diversion structure (coffer dam) is given in Construction Period (n) in years Return Period (T) in years % Risk Involved 1 20% 10% 5% 4% 2 36% 19% 10% 8% 3 49% 27% 14% 12% 4 59% 34% 19% 15% 5 67% 41% 23% 18% 4.5 DISCHARGE DATA MEASURED AT SITE The project proponents are monitoring discharge data at the following locations since December 2006: Zimithang BTK Namstring The monthly averages of the data observed at the above sites are given in Tables-4.14 to TABLE-4.14 Average measured discharge data at Zimithang Discharge (cumec) Month January February March April May June July August September October November December WAPCOS Limited 4-19

69 EIA study for Nyamjangchu TABLE-4.15 Average measured discharge data at BTK Discharge (cumec) Month January February March April May June July August September October November December TABLE-4.16 Average measured discharge data at Namstring Discharge (cumec) Month January February March April May June July August September October November December SEDIMENT DATA MEASURED AT SITE The project proponents are monitoring sediment level at Zimithang since January The monthly averages of the sediment data observed at Zimithang site is given in Table WAPCOS Limited 4-20

70 EIA study for Nyamjangchu TABLE-4.17 Average sediment data at Zimithang (Unit:ppm) Year Month Block Coarse Medium Fine Total January I II III February I II III March I II III April I II III May I II III June I II III July I II III August I II III September I II III October I II III November I II III December I II III January I II III February I II III March I II III April I WAPCOS Limited 4-21

71 EIA study for Nyamjangchu Year Month Block Coarse Medium Fine Total II III May I II III June I II III July I II III August I II III September I II III WAPCOS Limited 4-22

72 5.1 GENERAL CHAPTER-5 BASELINE SETTING FOR PHYSICO-CHEMICAL ASPECTS Before start of any Environmental Impact Assessment study, it is necessary to identify the baseline levels of relevant environmental parameters which are likely to be affected as a result of the construction and operation of the proposed project. A similar approach has been adopted for conducting the CEIA study for the proposed Nyamajangchhu hydroelectric Project. A Scoping Matrix as outlined in Chapter-3 was formulated to identify various issues likely to be affected as a result of the proposed project. Based on the specific inputs likely to accrue in the proposed project, aspects to be covered in the EIA study were identified. The other issues as outlined in the Scoping Matrix were then discarded. Thus, planning of baseline survey commenced with the shortlisting of impacts and identification of parameters for which the data needs to be collected. The baseline status has been divided into following three categories: Physico-chemical aspects Ecologcal aspects Socio-Economic aspects. The baseline setting for physico-chemical aspects have been covered in this Chapter. 5.2 METEOROLOGY The climate of the project area is characterised by cool and dry climate. Meteorologically, the year can be divided into three distinct seasons. Winter season sets in from the month of October and continues upto February, followed by summer season from March to June. The area receives rainfall under the influence of south-west monsoons over a period of three months from July to September. The climate of the region varies with altitude. The climate of Nyamjang Chu basin is humid in the lower elevation and cold in the higher elevations. From late October to early March winter prevails, whereas, pre-monsoon season is from March to April. The monsoon period extends from May to September. The minimum and maximum temperature at Tawang, the district headquarters varies between -2.9 o C to 32 o C. The rainfall varies considerably in the basin. The average annual rainfall reported at Muruga Bridge in the adjacent Tawang Chu sub basin is WAPCOS Limited 5-1

73 about 1710 mm. The rainfall data available at Bhalukpong and Dirang is given in Tables-5.1 and 5.2. The location of the stations at Bhalukpong and Dirang is given in Figure-5.1. The annual rainfall (mm) at Bhalukpong and Dirang is given in Figure-5.2. The monthly average rainfall (mm) at Bhalukpong and Dirang is given in Figure-5.3. Figure 5.1: Locations of Dirang, Bomdilla and Bhalukpong Dirang Not to Scale WAPCOS Limited 5-2

74 TABLE-5.1 Rainfall Data at Bhalukpong Monthly Total Rainfall (mm) Annual Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall Avg WAPCOS Limited 5-3

75 TABLE-5.2 Rainfall Data at Dirang Year Monthly Total Rainfall (mm) Annual Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Rainfall Avg WAPCOS Limited 5-4

76 Figure-5.2 : Annual Rainfall (mm) at Bhalukpong and Dirang Figure-5.3: Monthly Average Rainfall (mm) at Bhalukpong and Dirang WAPCOS Limited 5-5

77 5.3 GEOLOGY Regional Geology Arunachal Pradesh occupies the Northeastern part of the Himalayas and is a hilly state. In general, the southern limit of Arunachal Pradesh is marked by Brahmaputra plains. The state can be divided into four major physiographic units: The Brahmaputra Plains The Naga-Patkoi Ranges The Mishmi Hills The Himalayan Ranges The Brahmaputra Plains are at an average elevation of 100 m. The Himalayan Ranges attain an elevation of 7089m and are divided into different physio-tectonic divisions, separated by thrusts that, in general, run parallel to each other. From south to north, the following tectonic units have been identified: The sub-himalayan zone, known as the Siwalik Hills, rises abruptly from the Brahmaputra Plains from which it is separated by a fault the Foot Hill Fault. It is 10 to 20 km wide but narrows down to 1-2 km in the Dibang valley. The Lesser Himalayas, show elevations from 2500 m to 4000 m and are km wide. This zone abuts against the Mishmi Hills in the eastern Arunachal Pradesh. While its southern limit is marked by the Main Boundary Fault (MBT), its northern limit is defined by the Main Central Thrust. The Greater Himalayas, the zone of highest relief, with elevations greater than 6000 m, show steep slopes and deep gorges. Their southern limit is defined by Main Central Thrust (MCT). High grade metamorphic rocks, gneisses and granites generally form these high mountains. Trans-Himalayas is the northern most zone. It is about km wide and shows elevation lower than that of Greater Himalayas, from about 3000 m to 6000 m. The metamorphic belts of Arunachal Pradesh display evidence of multiple phases of deformation, metamorphism and granitic activity. Volcanic activity is of platform type and is associated with sedimentary rocks. The main metamorphic rock types are hornblende schist, garnetiferous biotite gneiss, kyanite-sillimanite- WAPCOS Limited 5-6

78 garnet-biotite gneiss, biotite gneiss, augen gneiss, quartzo-felspathic gneiss, dioritic gneiss, granodiorite, leuco-gneiss and amphibolites. A number of quartz, aplite and pegmatite veins of variable thickness are seen cutting across these rocks. Most of them are following the dominant foliation direction. Pegmatite mainly consists of quartz, feldspar and subordinate amount of muscovite. Some of these veins contain specks of pyrite. Foliation planes are recognized in Sherbang area in the form of colour banding, mainly in quartzite, besides colour banding layering in the ultramafic rocks in the form of primary layers. The region is tectonically very active. The rocks of the area have undergone repeated intense folding, faulting and thrusting in a highly complex fashion. The drainage pattern is typically structurally controlled, rivers following the zone of relative weakness, along faults or fractures. This pattern is generally aligned along E.N.E.-W.S.W. to N.E.-S.W. directions, but many transverse structural features have modified them. The rocks encountered from the Bhalukpong foot hills in the South to Tawang in the Northwest range in age from Tertiaries to Precambrian and are represented by the Siwalik Supergroup, Gondwana Group, Bichom Group, Lumla/ Dirang Formations, Bomdila Group and Sela Group (Plate-1, Volume-IV). The regional foliation trend of these rocks varies from NE-SW to NNE-SSW with a regional moderate northward dip. Major tectonic features viz., Main Frontal Thrust, Main Boundary Fault and Main Central Thrust are located away from the project area. While the Main Boundary Fault is disposed close to Bhalukpong, the gateway to Bomdila-Dirang-Sela-Tawang areas of the State, the Main Central Thrust passes through Rama Camp village, near Dirang. These main tectonic belts lie about 150 and 250 km from the project area, respectively. The rock formations in Tawang area belong to Sela Group (Palaeoproterozoic) and Lumla Formation (Mesoproterozoic) (Gopendra Kumar, 1997). Geology of the Project Area The rocks can be grouped into two main classes, viz gneiss and quartzite s with schist bands. While the gneisses occupy the upstream half of the site, the quartzite s occur in the downstream half. The gneisses are generally medium to coarse grained and consist of quartz, feldspar and biotite. Augen gneisses also occur occasionally. The biotite content varies and mica rich gneisses are common. WAPCOS Limited 5-7

79 Quartzite is fine to medium grained and invariably contains mica that makes it micaceous quartzite. Schist band of 1-5 m thickness are found associated with the quartzite. There are a few exposures of carbonaceous schist in the vicinity of the proposed area of surge shaft. The geology of different components of the project is given in following paragraphs. Barrage At the barrage site, the river is flat and very wide up to 200m, with high discharge and low velocity. River bed exposes black fine silty sand with high content of micaceous minerals. Boulders, composed mostly of quartzite and gneiss, and ranging in size from a few centimeters to a few meters, are seen in the river bed area. Gneissic rocks are best exposed on the right bank. General dip of Gneissic rock foliation is N 009 /46, i.e. in the upstream direction. The prominent joint set is developed along the foliation. On the left bank, gneisses are exposed only along the deeply incised nallahs near the Zimithang village. Desilting Basin and Intake The Desilting Basin is proposed to be placed over the river terrace on the left bank of the river. Four bore holes have been drilled on the left bank of barrage area that includes two each in desilting and intake areas at the base of the left bank slopes. In the desilting basin holes, the top layer comprises boulders of Biotite Gneiss of 4.5 to 7.0 m thickness, followed by 50 to 55 m thick blackish medium to fine silty sand with bedrock of Gneiss at the base. Although the rocks are fractured, the core recovery has been good. In the intake area holes, the bedrock of Biotite Gneiss is encountered at shallower depth. Head Race Tunnel The km long and 6.7 m dia Head Race Tunnel has been proposed on the left bank of the Nyamjang Chu. From its intake near Zimithang Village to the Surge Shaft, the HRT descends from El 2102m to 1940m at an average gradient of 1 in 148. The site is located in the rugged terrain of the Nyamjang Chu valley with ground elevations varying between El 1050m and 3800m. The site location on the left bank has been preferred mainly on considerations of adequate ground cover, exposed rock and development of infrastructure. The long section suggests that the vertical rock cover along the HRT varies from 100 m to about 990 m. The valley slopes on the left flank of the river tend to be much steeper than on the WAPCOS Limited 5-8

80 right side where the slopes are flatter and has number of streams cutting it deeply. The left bank in this stretch is covered with dense forest on the left bank. Large tracts along the HRT alignment are covered with thick overburden. These account for about 50% of the alignment. The HRT cuts across four major drainages, viz Taksang Chu at RD 5110m, BTK nala at RD 10810m, Shakti nala at RD 13700m and Gomkang Rong Chu at RD 20470m. For want of adequate ground cover, the HRT alignment has been pushed into the hill across the BTK and Gomkang Rong Chu, more prominently for the latter where the shift has been as much as 2.7 km leading to a rectangular kink in the HRT. Post realignment, the available ground cover over the HRT at drainage crossings is in excess of 150m. The area is characterized by the absence of springs. In general, entire project area is dry excepting ground moisture in Shakti-Gispu area that is attributed to well cultivated and irrigated landuse practices. The drilling at Surge Shaft site down to 125m depth has not encountered water table and has seen complete water loss during drilling. Surge Shaft The proposed 10/12m diameter Surge Shaft is located over quartzite with schist bands and occasional carbonaceous schist bands. The rocks have steep dips oriented in N178/35. The strata are highly jointed & occasionally sheared. Foliation joints are the most prominent ones. A slide debris also occurs at the site. Thin bands of carbonaceous schist dipping N 178/35 are found in the road cutting near the surge shaft area. Thickness of this band varies between 1 to 2 m. Pressure Shaft A two steps branched pressure shaft is proposed to take water from the surge shaft to the underground powerhouse. Three branches of the pressure shaft of dia. 2.9 m will carry water from the surge shaft and each of these branches will be subdivided into two branches of dia. 2.0 m to provide water to six machines in the powerhouse. Jointed quartzite with schistose bands is exposed in the area. Rock foliation dips N178/35. On surface, bedrock appears to be affected by closely spaced joints, foliation joints being prominent. As the geology of the area suggests that the zone consists of quartzite which are highly fractured requires steel liners and adequate support for stabilization of structure during the construction. WAPCOS Limited 5-9

81 Powerhouse An underground powerhouse complex is proposed in the downstream of Namtsering Bridge. The proposed size of the powerhouse cavity is about 20 m x 42 m x 166 m, with vertical cover of about 530 m and lateral cover of nearly 1200 m. Two parallel cavities, one for the powerhouse and one for the transformer hall are planned. The dimension of transformer hall is m X 16.3 m X 24m. 5.4 GEOMORPHOLOGY OF THE PROJECT AREA The project sites lie in a well dissected mountain terrain drained by the glacial fed Nyamjang Chu and the Tawang Chu. The ground elevations range between 1030m and 3800m. The slopes are mostly steep to very steep. The Nyamjang Chu flows at a general gradient of about 1 in 25. However, past river blockades have resulted into silted up lakes leading to sections of the river having very gentle gradients and wider river beds. Two such sections were found at Zimithang and BTK Bridge. The river section at the proposed barrage site near Zimithang is wide and characteristically flat in a stretch of about 2.5 km. It presents a classic case of silted up lake formed due to river blockade that, as per local reports, may not be very old. By implication, the lake deposits may not be much consolidated. The sudden drop in the river bed from a gradient of 1:280 at the barrage site to 1:10 immediately d/s of the lake deposit, suggests that its maximum thickness may be about 100m. At the barrage axis, it is found to be over 91m thick. A similar type of blockade with the presence of another lake deposit is found in BTK bridge area that is reported to have occurred as recently as July The drainage pattern is structurally controlled. Streams are typically seen to be taking sharp bends. Tributary streams are meeting the main river at about right angle. There are a number of first, second and third order streams joining the main river. The number of first order streams on the right bank is much more than that on the left bank. There are about 11 first order streams on the right bank of the river to which several second and third order streams are joining. On the left bank, there are only three major nallahs cutting across the area, important ones being Taksang Chu and Gomkang Rong Chu. Geomorphic Units Based on Satellite Imagery Interpretation Geomorphologically the study area is characterized by undulating dissected structural hills, which have been denudated and formed various features. The dissected hills have been denudated with Intermountain valley. Different WAPCOS Limited 5-10

82 geomorphic units were delineated based on their denudational, depositional, topographical and structural characteristics. The geomorphic units have followed a standard classification scheme. Homogeneous geomorphological terrain units were delineated and mapped as individual polygons. The main types of geomorphological units were distinguished as following: Highly dissected structural hill: With high density of drainage & lineaments. Moderate dissected structural hill: With moderate drainage density. Low dissected structural hill: With low drainage density. Hill terraces: In the study area hill terraces are developed on the gentle slopping area, especially nearby main river valley. These terraces are mainly under cultivation for agricultural crops. Flood plain: In the study area narrow floodplain is developed in upper reaches of Nyamjang Chu river. These flood plains are occupied with agricultural field. Sand bars: In the study area these landforms are developed near to river and are subjected to flooding in the monsoon period due to rise and fall of floodwater. Denudation hills: These are formed due to differential erosion and weathering. These are low hills with sparse vegetation cover and are subjected to high erosion rate. In the study area these landforms are found in the surge shaft area near Lumla village as well as in between Gispu and Shakti village. Intermountain valley: The intermountain valleys are developed in between the high sloping hills because of structural disturbances. In the study area these are the broad depressions between mountains normally filled with colluvial deposits. 5.5 SEISMICITY The north eastern part of the Himalayas is seismically very active. It is located at the junction of three tectonic plates: the Indian plate, the Eurasian plate and the Indo-Burmese plate. These are in constant collision and thus the region is under high tectonic stresses, which are released in the form of earthquakes. Neotectonic activity has rejuvenated the existing tectonic lineaments and developed new cross-faults. These cross-faults have controlled the sedimentation of Older (Mid to Lower Pleistocene) and Newer (Holocene) Alluvium. This has off-set the major thrusts (MCT, MBF, FHF). Epicenters of almost all the faults are located along the major cross-faults, whereas no activity is observed in the above said major thrusts. Major concentration of seismic events is restricted to north eastern part of the area with two main clusters around Po Chu fault zone. Besides these, some events scattered around Bame, Siang, Lohit and Tiding faults have also WAPCOS Limited 5-11

83 been observed indicating recent movements along these. About 87 seismic events have been witnessed in a period of 64 years, between 1929 and As per the Seismic Zoning map of India, the whole North East India falls in zone V. The list of major earthquakes in the Northeastern Himalaya, Arakan-Yoma and Shillong Plateau regionsis given in Table-5.3. TABLE-5.3 Major Earthquakes in the Northeastern Himalaya, Arakan-Yoma and Shillong Plateau regions Epicentral Region Date and Magnitude Major Damage to Time Environment Cachar March 21, Numerous earth fissures and sand craters Shillong plateau June 12, About 1542 people died Indo-China border, Feb 17, 1905 Mw=7.1 Landslides Xizang China 30º N and 95º E Indo-China border, May 12, 1906 Mw=6.5 Landslides North of Itanagar 28º N, 92º E Indo-Myanmar Aug 31, 1906 Ms=7.0 Landslides border, Near Chaukan Pass 27º N 97º E Sibsagar August 31, 7.0 Property damage 1906 Myanmar, Northern December 12, Ms=7.6 Property damage Sagaing Division, 1908; 26.5 N, 97º E 12:54:54 UTC Srimangal July 8, km 2 area suffered damage SW Assam September 9, 7.1 Property damage 1923 Dhubri July 2, Railway lines, culverts and bridges cracked Assam January 27, 7.6 Destruction of property 1931 Nagaland Destruction of property Indo-Bhutan Border region, 27º N, 92º E Jan 27, 1941; 12:41:48 UTC Ms=6.7 Landslips and damage to property N-E Assam October 23, 7.2 Destruction of property 1943 Arunachal July 7, Destruction of property Indo-China Border July 29, 1947; Mw=7.3, Landslips and destruction north of Itanagar, 13:29:25 UTC Ms=7.5 of property 28.5º N, 94º E Upper Assam July 29, Severe damage WAPCOS Limited 5-12

84 Epicentral Region Date and Time Upper Assam, Indo- August 15, China Border, 28.7º 1950; N 90.6º E 19:39:28.5 IST Patkoi Hills, Tirap District 25º N 95.8º E North of Sadiya, Dihang valley, 28.6º N 94.2º E NW Sadiya, Dihang Valley District (Arunachal-Assam border), 27.8º N 95.3º E Indo-China Border north of Itanagar, 28.7º N 94.2º E Manipur-Burma border August 15, 1950; 21:42:16 UTC Aug 16, 1950; 06:41:59.5 UTC Sept 13, 1950; 11:07:34.1 UTC Nov 18, 1951; 14:52:20 UTC Magnitude Major Damage to Environment Mw=8.6 About 1520 people died. It is the 6 th largest earthquake of the 20 th Century. 8.0 Property Damage 7.0 Bank collapse 7.0 Landslides and Bank failure 6.7 Landslides Property damage Darjeeling Property damage Myanmar, SE of Feb 20, 1962, Ms=6.7 Landslides Patkoi Hills, 26.13º 22:02:35 UTC N 96.94º E Indo-Myanmar border August 6, No casualty reported Note: Mw=Moment Magnitude, Ms=Surface Wave magnitude Mb=Body Wave Magnitude, UTC: Coordinated universal time Source: Tiwari (2002) and Amateur Seismic Centre at As IS1893:2002,, delineated as Figure-5.4, there are four zones, viz. Zone -II, III, IV and V in the country, on the Seismic Zoning map of India. Each area is defined by a specific zone factor listed in Table-5.4. On this seismic zoning map the northeast India including the project region lies on Very High damage zone (Zone V) (see Figure-5.4.) with zone factor TABLE-5.4 Seismic zones of India and zone factors Seismic Zones of India Hazard Intensity Zone Factor (Z) II Low Damage Risk Zone 0.10 III Moderate Damage Risk Zone 0.16 IV High Damage Risk Zone 0.24 V Very High Damage Risk Zone 0.36 WAPCOS Limited 5-13

85 A site specific study for design earthquake parameters for Nyamjang chhu HE Project has been conducted by IIT Roorkee and is enclosed as Annexure-II. The key findings of this report are given in the following paragraphs. The project lies in seismic Zone V as per the seismic zoning map of India incorporated in Indian Standard Criteria for Earthquake Resistant Design of Structures (IS : 1893 (Part 1): 2002). The recommendations for the site specific earthquake design parameters for the site are based on the studies carried out related to the tectonics, regional geology, local geology around the site, earthquake occurrences in the region around the site and the seismotectonic setup of the area. The site specific design earthquake parameter for MCE condition is estimated to Ms=8.0 magnitude earthquake occurring at MCT. The PGA values for MCE and DBE conditions and estimated to 0.36g and 0.18g respectively. Data for time history of earthquake ground motion for the dynamic analysis of the barrage was normalised to peak ground accelerations of 1.0 g. For MCE and DBE time history analysis ground motion will have to be multiplied by 0.36g and 0.18g respectively. Vertical spectral acceleration values may be taken as two third of the corresponding horizontal values. Similarly acceleration ordinates for the time history of vertical ground motion may be assumed as two third of the corresponding horizontal value. The site specific design acceleration spectra shall be used in place of the design response spectra, given in IS: 1893 (Part 1). The horizontal design seismic coefficient for preliminary design of Dam (primary structure) is evaluated as α h = (Z/6)* (S a /g) where, Z is taken as the estimated PGA coefficient for MCE (0.36 in this case) S a /g is obtained from normalized horizontal acceleration spectra) corresponding to the fundamental time period of the dam T. For other (secondary structures), appropriate Reduction Factor R, as specified in IS: 1893 may be used along with Importance factor I=1. For calculating the horizontal seismic design coefficient as: A h =(Z/2)* (S a /g)*(i/r) WAPCOS Limited 5-14

86 5.6 LAND USE PATTERN Landuse describes how a patch of land is used (e.g. for agriculture, settlement, forest), whereas land cover describes the materials (such as vegetation, rocks or buildings) that are present on the surface. Accurate land use and land cover identification is the key to most of the planning processes. The land use pattern of the study area has been studied through digital satellite imagery data. Digital IRS-P6, LISS-III satellite imagery (Path: 095, Row: 048) dated 9 th May,2007 was procured from National Remote Sensing Agency (NRSA), Hyderabad. The data was processed through ERDAS software package available with WAPCOS. Multi-variate statistics have been used for the analysis of multi-spectral data. As a first step, clustering algorithms was established to a set of multi-variate class statistics against which each pixel measurement vector in the scene was compared. Then a classification decision rule, such as the probability of maximum likelihood that the pixel belongs to a particular class amongst the statistics set was calculated and the pixel was assigned to the particular class. The information classes most often considered include both cover type or community type descriptors as well as limited structural categories, such as crown cover and size class: of the trees. Although two different approaches to the development of the multi-variate statistics are used, unsupervised and supervised, their combination gives better results. In the unsupervised classification, the radiance values of the image data set were submitted to clustering algorithms that generate statistics until the stopping rule i.e. minimum number of points per cluster, was reached and the minimum distance between clusters and separability measure was established. Another approach is to 'seed' spectral space with starting points to establish candidate mean value for clusters, and then iterate the clustering procedure until minimization criteria is achieved. In the supervised method, training sites with known properties were used to extract spectral statistics from the image data by interactively identifying the sites in the imagery. Ground truthing was done for site identification. In the unsupervised method, identification of the cluster was done after completing the classification by comparing the spatial distribution of the mapped classes with ground reference data. The wide geographic distribution and the range of sites and climates occupied by forests complicates the understanding of the interaction of forests with solar WAPCOS Limited 5-15

87 radiation. Many forests grow in uneven mountainous terrain. The terrain relief produces large variations in how solar radiation reaches the forests and produces land form shadows. Terrain relief also generates large micro-climate variations in temperature, precipitation, and soil properties that produces large differences in forest composition and activity over elatively small geographic areas. Vegetation indices are an aid for obtaining accurate results. The DN values of different bands can be combined mathematically to create output images that can be used extensively in forest analysis to bring out small differences between vegetation classes. These mathematical combinations are called indices and if chosen judiciously, they highlight and enhance differences, which cannot be observed in the display of original color bands. Indices also help in minimizing shadow effects in satellite multi-spectral images. Ground truth studies were conducted in the area to validate various signals in the satellite images and correlate them with different land use domains. The image obtained after the vegetation index, enhancement becomes a single band data Le. The grey set. The grey set was merged with the colored False Color Composite (FCC). This image was then classified using the prominent signatures extracted based on the past experience. However, this is only a preliminary classification which will be refined further. The FCC and the classified image of the project and its surroundings is given as Figures-5.5 and 5.6 respectively. The landuse pattern of the study area are given in Table-5.5. TABLE-5.5 Land use pattern of the study area Landuse Cover Area (ha) Percentage of Study Area (%) Dense vegetation Open vegetation Scrubs Agriculture land Water body Settlement Total It is evident from Table-5.5, that major land use category in the study area is forest, which accounts for almost 88.27% of the study area. The other major category is scrubs accounting for about 6.25% of the study area. The agriculture land accounts for about 4.04% of the study area. The area under water body WAPCOS Limited 5-16

88 account for about 1.42% of the study area. The area under settlement is about 0.03% of the study area. 5.7 SOILS Soil is the product of geological, chemical and biological interactions. The soils in the region vary according to altitude and climate. The soil in the project area and study area are young like any other region of Himalayas. The vegetal cover is one of the most important influencing factors characterizing the soil types in a region. Soil on the slope above 30 o, due to erosion and mass wasting processing, are generally shallow and usually have very thin surface horizons. Such soils have medium to coarse texture. Residual soils are well developed on level summits of lesser Himalayas, Sub-soil are deep and heavily textured. The soil quality was monitored at various locations in the catchment area. The monitoring was conducted by WAPCOS for three seasons namely Monsoon (August 2007), Post-Monsoon (December 2007) and Pre-Monsoon (March 2008). As a part of field studies, soil samples have been collected at various locations in the catchment area. The sampling stations are shown in Figure The results of Monsoon (August 2007), Post-Monsoon (December 2007) and Pre-Monsoon (March 2008). seasons are given in Tables 5.6 to 5.8 respectively. The ph of soil at various sites lies within neutral range. The levels of NPK indicate moderate to high soil productivity. The sodium levels do not indicate any potential for soil salinization or adverse impacts on soil productivity. In a hydroelectric project, no significant impact on soil quality is expected barring, soil pollution at local level due to disposal of construction waste. For amelioration of such impacts appropriate management measures are recommended. R. S. Envirolink Technologies Pvt. Ltd. monitored soil quality at various locations for three seasons namely, Pre-monsoon (March 2008), Monsoon (August 2008) and Post-monsoon (December 2008).The results are given in Tables-5.9 to WAPCOS Limited 5-17

89 TABLE-5.6 Results of soil sampling analysis of study area (Monsoon season) Parameter Unit S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 ph Electrical µmhos/ Conductivity cm Available kg/ha Nitrogen Available kg/ha Potassium Available kg/ha Phosphorus Cation meq/ Exchange Capacity 100 gm Sulphates mg/kg <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 (as SO 4 ) Chlorides mg/kg (as cl) Sand %w/w Clay %w/w Silt %w/w Texture Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-18

90 TABLE-5.7 Results of soil sampling analysis of study area (Post-monsoon season) Parameter Unit S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 ph Electrical µmhos/ Conductivity cm Available kg/ha Nitrogen Available kg/ha Potassium Available kg/ha Phosphorus Cation meq/ Exchange Capacity 100 gm Sulphates mg/kg <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 (as SO 4 ) Chlorides mg/kg (as cl) Sand %w/w Clay %w/w Silt %w/w Texture Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-19

91 TABLE-5.8 Results of soil sampling analysis of study area (Pre-monsoon season) Parameter Unit S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 ph Electrical µmhos/ Conductivity cm Available kg/ha Nitrogen Available kg/ha Potassium Available kg/ha Phosphorus Cation meq/ Exchange Capacity 100 gm Sulphates mg/kg <1 <1 <1 <1 <1 <1 <1 <1 <1 <1 (as SO 4 ) Chlorides mg/kg (as cl) Sand %w/w Clay %w/w Silt %w/w Texture Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Sandy Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-20

92 For physico-chemical status of the soil, the samples were collected from the different locations viz. Submergence area (S1), Downstream of Barrage site (S2), Downstream of Power House site (S3) and Catchment area (S4). The soil samples were taken with the help of a soil sampler from a depth of about cm, and various physical and chemical parameters were analyzed. The Physico-chemical characteristics of soil samples collected are analyzed for premonsoon, monsoon and post-monsoon seasons are given in Tables 5.9 to 5.11 respectively. TABLE-5.9 Physico-chemical characteristics of soils collected from different locations in project area (Pre-monsoon) S. No. Soil Characteristics S1 S2 S3 S4 A. Physical Characteristics 1 Sand, %w/w Clay,%w/w Silt, %w/w Soil texture 5 Electrical Conductivity (µs/cm) 6 ph Organic matter, % Available Nitrogen, kg/ha Available Phosphorous, kg/ha Available Potassium, kg/ha Source: Field Studies, RSET TABLE-5.10 Physico-chemical characteristics of soils collected from different locations in project area (Monsoon) S. No. Soil Characteristics S1 S2 S3 S4 A. Physical Characteristics 1 Sand, %w/w Clay,%w/w Silt, %w/w Soil texture 5 Electrical Conductivity (µs/cm) 6 ph Organic matter, % Available Nitrogen, kg/ha Available Phosphorous, kg/ha Available Potassium, kg/ha Source: Field Studies, RSET WAPCOS Limited 5-21

93 TABLE-5.11 Physico-chemical characteristics of soils collected from different locations in project area (Post-monsoon) S. No. Soil Characteristics S1 S2 S3 S4 A. Physical Characteristics 1 Sand, %w/w Clay,%w/w Silt, %w/w Soil texture 5 Electrical Conductivity (µs/cm) 6 ph Organic matter, % Available Nitrogen, kg/ha Available Phosphorous, kg/ha Available Potassium, kg/ha Source: Field Studies, RSET Soil texture/particle size distribution act as guide to many soil characteristics directly or indirectly related to plant growth. The textural class guides to understand soil water retention, availability, infiltration and drainage conditions. The soils of the study area show loamy to sandy loam structure. The soil in submergence area is almost neutral in nature, while soil samples downstream of barrage site and powerhouse site are slightly acidic in nature. The Electrical Conductivity ranged from 130 µs/cm at downstream of powerhouse to 290 µs/cm at downstream of barrage site. The organic matter was observed least in catchment area soil samples. The organic matter and level of various nutrients indicate moderate to high productivity of soils. 5.8 WATER QUALITY There are no major sources of organic pollution loading in the basin. The river basin has low population density with low cropping intensity. The low cropping intensity coupled with low agro-chemical dosing also means that the pollution load due to agro-chemicals is quite low. The absence of industries implies that there is no pollution load from this source as well. As a part of the field studies, water samples from various locations were collected. The sampling locations are shown in Figure-5.7. WAPCOS Limited 5-22

94 WAPCOS Limited had conducted sampling for the following three seasons: Monsoon : August 2007 Winter : December 2007 Summer : April 2008 The results are for the above referred three seasons are given in Table The drinking water quality standards are enclosed as Annexure-III. RS Envirolink Technologies Private Limited had conducted sampling for the following three seasons: Summer : April 2008 Monsoon : July 2008 Winter : December 2008 The results of water quality monitoring conducted by RSET Technologies are given in Table TABLE-5.12 Water quality analysis in the study area Parameter Unit W1 W2 W3 W4 W5 Monsoon season (August 2007) ph Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) Total Dissolved Solids mg/l (TDS) Total Suspended solids mg/l <0.1 <0.1 <0.1 <0.1 <0.1 Alkalinity mg/l Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 < <0.01 < < Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ Absent Absent Absent Absent Absent WAPCOS Limited 5-23

95 Parameter Unit W1 W2 W3 W4 W5 100 ml Winter season (December 2007) PH Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) Total Dissolved Solids mg/l (TDS) Total Suspended solids mg/l <0.1 <0.1 <0.1 <0.1 <0.1 Alkalinity mg/l Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 < <0.01 < < Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ 100 ml Absent Absent Absent Absent Absent Summer season (April 2008) ph Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) Total Dissolved Solids mg/l (TDS) Total Suspended solids mg/l <0.1 <0.1 <0.1 <0.1 <0.1 Alkalinity mg/l Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 <0.00 <0.01 <0.00 <0.00 WAPCOS Limited 5-24

96 Parameter Unit W1 W2 W3 W4 W Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ 100 ml Absent Absent Absent Absent Absent Source: Field Studies, WAPCOS Limited TABLE-5.13 Water quality analysis in the study area Parameter Unit W1 W2 W3 W4 W5 Summer season (April 2008) ph Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) Total Dissolved Solids mg/l (TDS) Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 < <0.01 < < Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ 100 ml Absent Absent Absent Absent Absent Monsoon season (July 2008) ph Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) WAPCOS Limited 5-25

97 Parameter Unit W1 W2 W3 W4 W5 Total Dissolved Solids mg/l (TDS) Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 < <0.01 < < Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ 100 ml Absent Absent Absent Absent Absent Winter season (December 2008) ph Temperature o C Dissolved Oxygen (DO) mg/l Electrical Conductivity µs/cm (EC) Total Dissolved Solids mg/l (TDS) Hardness mg/l Calcium mg/l Magnesium mg/l Fluorides mg/l BOD mg/l COD mg/l Nitrates mg/l Mercury mg/l <0.001 < <0.01 < < Cadmium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Total Chromium mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Lead mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Zinc mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Cyanides mg/l <0.01 <0.01 <0.01 <0.01 <0.01 Phenolic compounds mg/l Nil Nil Nil Nil Nil Faecal Coliform MPN/ Absent Absent Absent Absent Absent 100 ml Total Coliform MPN/ 100 ml Absent Absent Absent Absent Absent Source: Field Studies, RSET Limited WAPCOS Limited 5-26

98 The total hardness in various water samples ranged from mg/l, mg/l and mg/l in post-monsoon, winter and summer seasons respectively. The low calcium and magnesium levels are responsible for soft nature of water. The carbonate hardness (for water with alkalinity level as observed in the study area) is equal to the alkalinity level. The non-carbonate hardness accounts for the balance hardness. Normally non-carbonate hardness can be removed by boiling. However, hardness level in the area do not warrant any treatment. The low EC and TDS values indicate the lower concentration of cations and anions. This is also reflected by the fact that the concentration of most of the cations and anions are well within the permissible limit. The fluorides level was lower than the permissible limit (1 mg/l) for drinking purposes. The BOD and COD values are well within the permissible limits, which indicates the absence of organic pollution loading. This is mainly due to the low population density and absence of industries in the area. The marginal quantity of pollution load which enters river Nyamhjangchhu gets diluted. In fact, even for the minimum flow, there is more than adequate water available for dilution. The Total Coliform and Fecal coliform are also low. Thus, It can be concluded that, water quality was observed to be quite good. The concentration of various heavy metals was below the permissible limit specified for domestic use. It can be concluded that water quality was observed to be quite good, as various parameters are well below the permissible limit specified for meeting domestic requirements. 5.9 AMBIENT AIR QUALITY The ambient air quality with respect to the study area around the proposed site forms the baseline information. The study area represents rural environment. The sources of air pollution in the region are vehicular traffic, dust arising from unpaved village roads and domestic fuel burning. The prime objective of the baseline air quality study was to establish the existing ambient air quality of the area. This section describes the identification of sampling locations, methodology adopted for monitoring, frequency of sampling. WAPCOS Limited 5-27

99 Selection of Sampling Locations The baseline status of the ambient air quality has been established through a scientifically designed ambient air quality monitoring network and is based on the following considerations: - Meteorological conditions on synoptic scale; - Representatives of regional background air quality for obtaining baseline status - Representation of likely affected area. Three Ambient Air Quality Monitoring (AAQM) locations were selected taking care of above-mentioned points. The location of Ambient Air Quality Monitoring station is shown in Figure-5.7. Frequency and Parameters for Sampling Ambient air quality monitoring has been carried out with a frequency of two samples per week at three locations for three seasons. The monitoring was conducted by WAPCOS for the following seasons: Post-Monsoon : October 2007 Winter : December 2007 January 2008 Summer : April May 2008 RS Envirolink Technologies Private Limited had conducted sampling for the following three seasons: Summer : April May 2008 Monsoon : July August 2008 Winter : November December 2008 The baseline data of ambient air environment has been generated for the mentioned parameters as given below: Respirable Particulate Matter (RSPM) Sulphur dioxide (SO 2 ) Oxides of Nitrogen (NO 2 ). Result of Ambient Air Quality Monitoring The result of ambient air quality monitoring conducted by WAPCOS Limited for various seasons are given in Tables-5.14 to The ambient air quality standards are given in Annexure-IV. WAPCOS Limited 5-28

100 TABLE-5.14 Results of ambient air quality monitoring in the study area (Post- Monsoon season) (Unit: µg/m 3 ) Station RPM SO 2 NO x 31 BDL BDL BDL 6.3 Zemithang 25 BDL BDL BDL BDL BDL BDL BDL BDL 16.7 Ghorsham 26 BDL BDL BDL BDL BDL BDL BDL BDL 9.0 Lumla 29 BDL BDL BDL BDL BDL BDL BDL BDL 7.8 Namstring 21 BDL BDL BDL BDL BDL 7.2 BDL: Below Detectable Limit(6µg/m 3 ) Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-29

101 TABLE-5.15 Results of ambient air quality monitoring in the study area (Winter season)(unit: µg/m 3 ) Station RPM SO 2 NO x 25 BDL BDL BDL 11.4 Zemithang 33 BDL BDL BDL BDL BDL BDL BDL BDL 8.9 Ghorsham 28 BDL BDL BDL BDL BDL BDL BDL BDL 11.7 Lumla 34 BDL BDL BDL BDL BDL BDL BDL BDL 6.8 Namstring 25 BDL BDL BDL BDL BDL 7.1 BDL: Below Detectable Limit(6µg/m 3 ) Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-30

102 TABLE-5.16 Results of ambient air quality monitoring in the study area (Summer season)(unit: µg/m 3 ) Station RPM SO 2 NO x 24 BDL BDL BDL 6.3 Zemithang 28 BDL BDL BDL BDL BDL BDL BDL BDL 16.7 Ghorsham 25 BDL BDL BDL BDL BDL BDL BDL BDL 7.5 Lumla 30 BDL BDL BDL BDL BDL BDL BDL BDL 6.6 Namstring 26 BDL BDL BDL BDL BDL 9.8 BDL: Below Detectable Limit(6µg/m 3 ) Source: Field Studies, WAPCOS Limited Summary of ambient air quality monitoring The summary of results of ambient air quality monitoring by WAPCOS Limited is given in Table The summary of results of ambient air quality monitoring by RS Envirolink Technologies Private Limited is given in Table WAPCOS Limited 5-31

103 TABLE-5.17 Summary of ambient air quality monitoring in the study area Unit: µg/m 3 Average Station Maximum Minimum Post-monsoon season RPM Zemithang Ghorsham Lumla Namstring SO 2 Zemithang BDL BDL BDL Ghorsham BDL BDL BDL Lumla BDL BDL BDL Namstring BDL BDL BDL NO 2 Zemithang Ghorsham Lumla Namstring Winter season RPM Zemithang Ghorsham Lumla Namstring SO 2 Zemithang BDL BDL BDL Ghorsham BDL BDL BDL Lumla BDL BDL BDL Namstring BDL BDL BDL NO 2 Zemithang Ghorsham Lumla Namstring Summer season RPM Zemithang Ghorsham Lumla Namstring SO 2 Zemithang BDL BDL BDL Ghorsham BDL BDL BDL Lumla BDL BDL BDL Namstring BDL BDL BDL WAPCOS Limited 5-32

104 Average Station Maximum Minimum NO 2 Zemithang Ghorsham Lumla Namstring Source: Primary survey TABLE-5.18 Ambient Air Quality Data RPM (µg/m 3 ) SO 2 (µg/m 3 ) NO 2 (µg/m 3 ) Villages Seasons Max Min Avg. Max Min Avg. Max Min Avg. Premonsoon Zemithang Monsoon Winter Premonsoon Ghorsham Monsoon Winter Premonsoon Lumla Monsoon Winter Premonsoon Namstring Monsoon Winter Source: Field Studies, RSET Limited Observations on ambient RPM levels The average RPM levels as observed at various stations in the study area ranged from 44.1 to 49.8 µg/m 3, 45.8 to 50.6 µg/m 3 and 45.8 to 50.5 µg/m 3 for postmonsoon, winter and summer seasons respectively. The highest RPM value was recorded as 59 µg/m 3 in summer season. The RPM values monitored during the field survey were well below the permissible limit of 60 µg/m 3 for industrial, residential and rural areas (Refer Annexure-IV). Observation on ambient SO 2 levels The SO 2 level was Below Detectable Limit BDL) of 6 µg/m 3 at all the stations covered in ambient air quality monitoring programme. WAPCOS Limited 5-33

105 Observations on NO 2 levels The highest average NOx values of 12.2 µg/m 3 were observed in the summer and post-monsoon seasons respectively. The highest value observed was 16.7 µg/m 3. The NO 2 level observed at various sampling stations was much lower than the permissible limit of 40 µg/m 3 for industrial, residential and rural areas are given in Annexure-IV. Conclusions Based on the findings of the ambient air quality survey, conducted for the summer, post-monsoon and winter seasons, it can be concluded that the ambient air quality is quite good in the area. The values of these parameters were well below the permissible limits specified for residential, rural and other areas. The absence of industries, low vehicular traffic and low population density can be attributed for good ambient air quality in the project area NOISE ENVIRONMENT Baseline noise data has been measured using a weighted sound pressure level meter. The survey was carried out in calm surrounding. Sound Pressure Level (SPL) measurement in the outside environment was made using sound pressure level meter. Hourly noise meter readings were taken at different sites. The monitoring was conducted by WAPCOS for the following seasons: Post-Monsoon : October 2007 Winter : December 2007 January 2008 Summer : April May 2008 The hourly ambient noise levels monitored for summer, post-monsoon and winter seasons are given in Tables-5.19 to 5.21 respectively. The day time equivalent noise levels estimated are given in Table RS Envirolink Technologies Private Limited had conducted sampling for the following three seasons:. Summer : April May 2008 Monsoon : July August 2008 Winter : November December 2008 The location of various noise monitoring stations is shown in Figure-5.6. The noise levels were monitored continuously from 6 AM to 9 PM at each location and hourly equivalent noise level was measured. Sound Pressure Level (SPL) WAPCOS Limited 5-34

106 measurement in the ambient environment was made using sound pressure level meter. The noise standards for various categories is given in Annexure-V. TABLE-5.19 Hourly equivalent noise levels in the study area in Post-monsoon season (Unit: db(a)) Time Barrage Zimithang Ghorsam Lumla Namstring site 6-7 AM AM AM AM AM AM Noon 12 Noon PM 1 2 PM PM PM PM PM PM PM PM Source: Field Studies, WAPCOS Limited TABLE-5.20 Hourly equivalent noise levels in the study area (Winter season ) (Unit: db(a)) Time Barrage Zimithang Ghorsam Lumla Namstring site 6-7 AM AM AM AM AM AM Noon 12 Noon PM 1 2 PM PM PM PM PM PM PM PM Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-35

107 TABLE-5.21 Hourly equivalent noise levels in the study area (summer season ) (Unit: db(a)) Time Barrage Zimithang Ghorsam Lumla Namstring site 6-7 AM AM AM AM AM AM Noon 12 Noon PM 1 2 PM PM PM PM PM PM PM PM Source: Field Studies, WAPCOS Limited TABLE-5.22 Day time equivalent noise level at various sampling locations S. No. Location Zone L day (db(a)) Post-monsoon 1. Barrage site Residential Zemithang Residential Ghorsham Residential Lumla Residential Namstring Residential 39 Winter 1. Barrage site Residential Zemithang Residential Ghorsham Residential Lumla Residential Namstring Residential 38 Summer 1. Barrage site Residential Zemithang Residential Ghorsham Residential Lumla Residential Namstring Residential 38 Source: Field Studies, WAPCOS Limited WAPCOS Limited 5-36

108 The day time equivalent noise level in post-monsoon, winter and summer seasons at various sampling stations ranged from 39 to 40 db(a), 38 to 40 db(a). Likewise, day time equivalent noise level in winter season ranged from 38 to 39 at various sampling stations which were well within the permissible limit specified for residential area (Refer Annexure-V). The day time equivalent noise level as monitored by RSET are shown in Table TABLE-5.23 Day time Equivalent noise level monitoring at various sampling locations in the study area Day time equivalent noise level S. No. Site name [db(a)] Summer Monsoon Winter 1 Zimithang Market Zimithang, (Barrage site) Ghorsham village Ghorsham, along the river bank Sirdi village Sirdi, Along the river bank Downstream of BTK bridge Power house Site Namtsering bridge WAPCOS Limited 5-37

109 6.1 GENERAL CHAPTER-6 BASELINE SETTING FOR ECOLOGICAL ASPECTS The baseline status has been divided into following three categories: Physico-chemical aspects Ecological aspects Socio-Economic aspects. The baseline setting for ecological aspects are outlined in the present Chapter. The study area represents diverse biological assemblages unique in structure, composition, and spatial pattern. These have been under a long influence of local communities. The following section highlights floral and faunal diversity, based on a review of available information and followed by primary data collection. 6.2 TERRESTRIAL ECOLOGY Forest type The forest type observed in the Study Area are breifly described in the following paragraphs. Champion and Seth (1968); Rao and Panigrahi (1961); Sahni (1981); Rao and Hajra (1986), etc are the prominent workers who studied forest and vegetation of the region. The forest types observed in the study area are as follows which is based on altitudinal and climatic factors. Sub- Tropical Forest These forests occur between 1200m and 1800m. The dominant species are Pinus wallichiana, Alnus nepalensis, Betula alnoides, etc. These type of forest mainly found near the Brokan Thang village on the left bank of the river in the catchment area. Temperate Forest These forests occur in the form continuous belt between 1800m and 3500 m altitudes. The forest is comparatively open and is further divided into temperate broad leaved and temperate conifer forests. Temperate Broad Leaved Forest Temperate broad leaved forest occur between 1800m and 2800 m altitudes. Tresses like Alnus nepalensis, Rhododendron arboreum, Lyonia ovalifolia, Mallotus philippensis, etc. are dominant. Climbers are rare where as various epiphytic species of Agapetes sp., Rhododendron sp., Vaccinium sp. are common with several lichens and ferns. WAPCOS Limited 6-1

110 Temperate Conifer Forest These forests are confined to m altitude and experience regular snowfall during winter. The top canopy is dominated by mixed coniferous type that includes Abies pindrow, Pinus wallichiana, etc with some broad leaved species of Rhododendron arboreum, Lyonia ovalifolia, Engelhardtia spicata, Juglans regia, etc. This type of forest is observed on the right bank of the river near Ghorsham village and in the catchment area. Subalpine and Alpine Forest These forests occur at high altitudes i.e. 3500m m and generally lack tree species and mostly observed in the catchment area and on the top of the hills. Subalpine forest is characterized by tree species like Abies pindrow, Rhododendron sp. The common shrubs are Berberis angulosa, Gaultheria nummularis, Rubus sp., Primula macrophylla, etc and with some herbaceous species Arenaria sp., Inula cuspidata, Sedum sp., Trigonella corniculata, etc. The alpine zone is above the altitude of 4000 m and remains mostly covered with snow for the major part of the year. The vegetation is very scarce and comprise of shruby Rhododendron sp., and herbs like Aconitum sp., Arenaria sp., Ranunculus sp., Primula sikkimensis, Polygonum capitatum, Rumex nepalensis, etc are common. Secondary Forests The secondary forests are found along the banks of the rivers where primary forests have been cleared in the past for timber and nearby the villages. The secondary forests are dominated by trees belonging to species Macaranga denticulata, Alnus nepalensis, Lyonia ovalifolia, Morus alba, Ficus semicordata and Schima khasiana. At many places vegetation is very sparse and shows rock outcrops that are devoid of any plant species. Grasslands The grasslands are common near the Nyamstring area on both the banks of the river. Lemon grass (Cymbopogon flexuosus) is dominant in this area with some trees like Ficus semicordata, Toona ciliata, Salix karelinii, etc. Emblica officinalis and Woodfordia fruticosa are frequent on both the banks of river. WAPCOS Limited 6-2

111 Cropping pattern and Horticultural species Elusine, Pumpkin, Job-tears, Chilly and Beans are usually cultivated as agricultural crops. Banana, Peach and at very few places newly developed apple orchards were observed. These horticultural crops were often seen planted as isolated trees in the homegardens Floristic composition As per survey conducted by WAPCOS Ltd., a total of 121 plant species were recorded during floristic survey in the sample sites. A complete list of plant species found in the study area representing Dicots, Monocots, Gymnosperms, Pteridophytes, Bryophytes, Algae and Fungi is given in Annexure-VI. The names of the family and the local names (wherever possible) are also given. The number of plant species belonging to different groups is summarized in Table 6.1. TABLE-6.1 No. of plant species belonging to different groups listed during the vegetation survey in the study area Plant Group Winter Summer Monsoon Angiosperms Dicots Monocots Trees Shrubs Herbs Climbers Gymnosperms Pteridophytes Bryophytes 4 Algae 7 Fungi Economically important species As per survey conducted by WAPCOS Ltd., about 35 economically important plant species were recorded from the study area. The names of economically important and wild crop relative plants found during the survey have been listed in Table WAPCOS Limited 6-3

112 TABLE-6.2 Economically important and wild crop relative plant species found in the study area S.No. Species Uses 2 Alnus nepalensis Fuel wood, timber 3 Artemisia nilagirica Medicine 1 Betula alnoides Timber 4 Bidens pilosa Edible 6 Cannabis sativa Medicinal 5 Centella asiatica Medicinal 7 Cryptomeria japonica Timber 8 Cupressus torulosa Ethnobotanical importance, Timber 11 Elaeagnus sp. Medicinal 10 Engelhardtia spicata Fuel wood 9 Erythrina arborescens Fencing 13 Fagopyrum dibotrys Vegetables, fodder 14 Ficus roxburghii Fodder 15 Fragaria indica Fruit edible 16 Gerardinia heterophylla Edible 17 Houttuynia cordata Medicinal 18 Juglans regia Timber 19 Lycopodium clavatum Medicinal 20 Lyonia ovalifolia Medicinal and fuel wood 21 Macaranga denticulate Fuel 22 Morus serrata Fodder 26 Pinus wallichiana Timber, fuel and for light 27 Plantago major Medicinal 12 Populus gamblei Avenue tree 28 Quercus griffithii Timber 23 Rhododendron campanulatum Fuel wood, ornamental 24 Rhododendron maddeni Fuel wood, ornamental 25 Rhododendron nerifolium Fuel wood, ornamental 29 Rubia cordifolia Dye 30 Rubus ellipticus Fruit edible 31 Rumex nepalensis Medicinal 32 Schima khasiana Timber 33 Solanum viarum Medicinal 34 Urtica dioca Edible 35 Zanthoxylum armatum Medicinal WAPCOS Limited 6-4

113 6.2.4 FIELD STUDIES ON VEGETATION AND FLORAL DIVERSITY BY WAPCOS LTD. The present ecological study by WAPCOS Ltd. was undertaken with the following objectives to: prepare a checklist of flora in the submergence area; list RET, economically important and medicinal plant species; determine frequency, abundance and density of different vegetation components; estimate density and volume of the tree component with height above 8 m; identify and list RET faunal species in the project area. The field survey for all the above aspects of the ecological study pertaining to monsoon was conducted in monsoon (August 2007), winter (December 2007) and summer (April 2008) Sampling Sites The sites selected for sampling of vegetation is given in Table-6.3. The location of sampling sites is given in Figure-6.1. TABLE-6.3 Details of sampling sites for terrestrial ecological survey Sampling Site Location Site-1 Catchment Area Site-2 Submergence area Site-3 Dam site, near village Zimithang Site-4 Near village Shakthi Site-5 1 kmdownstream of BTK Bridge Site-6 Near village Gispu Site-7 Near Power House Site Methodology The sampling was carried out within 1 km of the riverbed. Considering the difficult terrain, quadrat method was used for vegetation sampling. The phytosociological data for trees and shrubs were collected from random quadrats of 10 x 10 m size laid at the project site. Random quadrats of 1 x 1 m size were laid for the study of herb component at each site. The number of quadrats used for the study of different vegetation components at each sampling site is given in Table 6.4. WAPCOS Limited 6-5

114 TABLE 6.4 Number of quadrats used for vegetation study at different sampling sites for different vegetation components S.No Sampling Sites Tree Shrub Herb 1. Catchment Area Submergence area Dam site, near village Zimithang 4. Near village Shakthi kmdownstream of BTK Bridge 6 Near village Gispu Near Power House Site During the survey, number of plants of different species in each quadrat was identified and counted. The height of individual trees was estimated using an Abney level/ Binocular and the DBH of all trees having height more than 8 m was measured. Based on the quadrat data, frequency, density and cover (basal area) of each species were calculated. The IVI values for different tree species were determined by summing up the Relative Frequency, Relative Density and Relative Cover values. The Relative Frequency and Relative Density values were used to calculate the IVI of shrubs and herbs. The volume of wood for trees was estimated using the data on DBH (measured at 1.5 m above the ground level) and height. The volume was estimated using the formula: πr 2 h, where r is the radius and h is the estimated height of the bole of the tree. The data on density and volume were presented in per ha basis. Two species diversity indices viz., Shannon index of general diversity (H) and Evenness index (e) were computed using the following formula: Shannon index of general diversity (H): - ΣP i log P i Where, n i = importance value for each species N = total importance values Pi = importance probability for each species = n i /N Evenness index (e): H/ log S Where, H = Shannon index of general diversity And, S = number of species IVI values were used for computation of both the diversity indices. WAPCOS Limited 6-6

115 During the vegetation survey, herbaria were prepared for the plants those had flowers. Rare and endangered species were identified referring to the Red Data Book of India, Flora of Meghalaya and other available literature, flora and herbarium pertaining to the rare/ endangered species of Arunchal Pradesh Results The community characteristics and species diversity indices at various sampling sites is given in Tables-5.5 and 5.6 respectively. Site-1: Catchment Area There were 10 tree species recorded from this site. The tree density was 455 individuals/ha (Table-5.5). Pinus wallichiana (160 individuals/ha) and Alnus nepalensis (125 individuals /ha) were the dominant and co-dominant tree species in this forests. This two species together accounted for about 55% of the total density. Ten shrubs were recorded from the site. Rhus javanica and Eleagnus sp. were the dominant shrub species. Eighteen, Twenty three and thirty nine herbaceous species were recorded during monsoon, winter and summer respectively. Polygonum capitatum, Oxalis corniculata and Hydrocotyl javanica were the dominant species. Shannon s diversity index ranged from 1.95 to 3.55 for tree, shrub and herb component. The evenness index was high having values more than 0.85 (Table 5.6). The project site was not found to have any rare and endangered plants of the region. Plants of other economic importance such as timber, medicinal and edible fruits were common. Site-2 : Submergence Area Twelve tree species were recorded from this site. The tree density was 270 individuals/ha (Refer Table-6.5). Alnus nepalensis with 70 individuals/ha was the dominant species and alone contributed to about 26% of the total density followed by Erythrina arboresence (45 individuals ha -1 ) and Macaranga denticulata (35 individuals ha -1 ). Ten shrubs were recorded from the site. Eleagnus sp. and Rubus ellipticus were the dominant shrub species. Twenty four species of herbs were recorded during winter and monsoon and thirty nine species during summer season. Polygonum capitatum, Anaphilis triplinervis and Oxalis corniculata were the dominant herbaceous species. WAPCOS Limited 6-7

116 Shannon s diversity index ranged between 2.18 and 3.55 for all for all three components i.e., tree, shrub and herb. The evenness index was also high having values more than 0.9 (Table 6.6). The project site was not found to have many rare and endangered plants. Plants of other economic importance such as timber, medicinal and edible fruits were common. Site-3 : Dam Site Eight tree species were recorded from the dam site. The tree density was low (250 individuals ha -1 ) (Table-6.5). Alnus nepalensis was the dominant species with 137 individuals ha -1 and alone accounted for about 48% of the total density followed by Rhododendron medini. However, the Alnus nepalensis individuals were found as cut stumps. Seven species of shrub were recorded from the site. Rubus ellipticus and Elaegnus sp. were the dominant shrubs. Twenty one herbaceous species were recorded during winter and monsoon season and twenty seven species during summer season. Galinsoga parviflora and Polygonum capitatum were dominant during winter and Pteridium aquilinum and Galinsoga parviflora during summer season. In general, species diversity and the Shannon s Index were low for the trees (1.71) and shrubs (1.68). However, it was higher in case of herbaceous components ( ) in the forests. The evenness index was also high having values more than 0.8 for all the three components (Table 6.6). Rare and endangered categories of plant species was not recorded in the dam site. However, plants of economic importance such as timber, medicinal and edible fruits were common. Site-4 : Near village Shakti There were eleven tree species recorded from this site. The tree density was 475 individuals/ha (Table-6.5). Alnus nepalensis with 160 individuals/ha was the dominant tree species followed by Schima wallichii (80 individuals /ha) were the dominant and co-dominant tree species in this forests. This two species together accounted for about 41% of the total density. Fourteen shrubs were recorded from the site; Ribes glaciale and Maesa indica were dominant. Twenty eight herbs species were recorded during winter and monsoon and thirty two herbs species were recorded during summer. Drymaria cordata and Nicandra WAPCOS Limited 6-8

117 physaloides were the dominant herb species during winter and Rumex nepalensis and Gnaphalium sp. dominated during summer season. Shannon s diversity index was high and ranged from 1 to 2.15 for tree, shrub and herb component. The evenness index was also high having values more than 0.8 (Table-6.6). Site-5 : 1 km downstream of BTK Brridge Nine tree species were recorded from the dam site. The tree density was low (410 individuals /ha) (Table -6.5). Macaranga denticulata was the dominant species with 210 individuals/ha followed by Albizzia lucida (40 individuals/ha) constituting 61% of the total density. Thirteen shrubs were recorded from the site and Artemesia nilagirica and Rubus ellipticus were dominant. Twenty six herbs species were recorded during winter and monsoon season and twenty five species during summer season. Galinsoga parviflora and Fagopurum dibotrys were dominant during winter and Polygonum hydropiper and Galinsoga parviflora during summer season. In general, species diversity and the Shannon s Index were low for the tree component (1.78) as compared to shrub (2.33) and herb (1.28 and 1.33) components in the forests. The evenness index was also high having values more than 0.8 for all the three components (Table 6.6). Rare and endangered categories of plant species was not recorded in the at this site. However, plants of economic importance such as timber, medicinal and edible fruits were common. Site-6 : Near village Gispu Seven tree species were recorded from this site. The tree density was 345 individuals/ha (Table-6.5). Alnus nepalensis with 180 individuals/ha was the dominant species and alone contributed to about 52% of the total density followed by Schima khasiana (60 individuals /ha). Twelve shrub species were recorded from the site. Elaegnus sp., Artemesia nilagirica, Mesea indica were the dominant shrub species. Nineteen species of herbs were recorded during winter and monsoon and twenty four recorded during summer season. Pouzolzia hirta and Bidens pilosa were dominant during winter while Fagopyrum dibotrys and Anaphalis triplinervis were the dominant herb species. WAPCOS Limited 6-9

118 Shannon s diversity index ranged between 1.04 and 2.03 for all for all three components i.e., tree, shrub and herb. The evenness index was also high having values more than 0.7 (Table 6.6). The project site was not found to have many rare and endangered plants. Plants of other economic importance such as timber, medicinal and edible fruits were common (Table-6.2). Site 7 : Powerhouse site Six tree species were recorded from this site. The tree density was low (355 individuals /ha) (Table-6.5). Alnus nepalensis was the dominant species with 215 individuals/ha and alone accounted for about 60 % of the total density followed by Macaranga denticulata. Eleven shrubs species were recorded from the site. Artemesia nilagirica and Eleagnus sp. was the dominant shrub. Sixteen species of herbs were recorded during winter and monsoon and seventeen species recorded during summer season. Fagopyrum dibotrys and Houttuynia cordata were dominant during winter season while Rumex nepalensis and Rubia cordifolia were dominant during summer season. In general, species diversity and the Shannon s Index were low for the tree component (1.35) as compared to shrub (1.00) and herb (1.17 and 1.19) components in the forests. The evenness index was also high having values more than 0.7 for all the three components (Table 6.6). Rare and endangered categories of plant species was not recorded in the dam site. However, plants of economic importance such as timber, medicinal and edible fruits were common (Table-6.2). TABLE 6.5 Community characteristics of the vegetation at various sampling locations at various sampling locations Site-1 : Catchment area Freque ncy % Density (No./h a) Basal area (m 2 /ha) IVI Species Trees Alnus nepalensis Engelhardtia spicata Erythrina arborescens Ficus scandens Hippophae salicifolia WAPCOS Limited 6-10

119 Density (No./h a) Basal area (m 2 /ha) IVI Freque Species ncy % Pinus wallichiana Quercus griffithii Salix sp Schima khasiana Zanthoxylum armatum Shrubs Artemisia nilagirica Cotoneaster sp Drynaria propinqua Elaeagnus sp Philadelphus tomentosus Plectranthus coetsa Rhus javanica Ribes glaciale Rubus ellipticus Viburnum erubescens Winter Summer Monsoon Herbs Density IVI Density IVI Density IVI Anemone vitifolia Aconogonum sp Anaphalis triplinervis Bistorta sp Blechnum sp Cannabis sativa Capsella bursa-pastoris Cirsium sp Corydalis rutifolia Cynoglossum furcatum Bidens pilosa Fagopyrum dibotrys Fragaria indica Gallium asperifolium Galinsoga parviflora Geranium nepalense Gerardinia heterophylla Gnaphalium sp Heracleum sp Hydrocotyl javanica Inula cappa Lepisorus nudus Leucas ciliate Lycopodium clavatum Mazus surculosus Nicandra physaloides Oenanthe sp Oxalis corniculata Parthenocisus himalayana Paspalum sp WAPCOS Limited 6-11

120 Density (No./h a) Basal area (m 2 /ha) IVI Freque Species ncy % Periploca sp Pilea lineolatum Piptanthus nepalensis Plantago major Poa annua Polygonum capitatum Potentilla fulgens Pouzolzia hirtra Pteridium aquilinum Ranumculus scleratus Rosa sericea Rumex nepalensis Rubia cordifolia Smythea sp Solanum viarum Stellaria sp Urtica dioca Viola sp Vittaria sp Site-2 :Sumbergence area Frequency % Density (No./ha) Basal area (m 2 /ha) IVI Species Trees Alnus nepalensis Betula alnoides Cupressus sp Erythirina arborescens Juglans regia Lyonia ovalifolia Macaranga denticulata Populus gamblei Quercus griffithii Rhododendron campanulatum Rhododendron nerifolium Salix sp Shrubs Artemisia nilagirica Drynaria propinqua Eleagnus sp Gaultheria fragrantissima Prinsepia utilis Rhus javanica Rubus ellipticus Rubus hypergyrus WAPCOS Limited 6-12

121 Rubus rugosus Spiraea canescens Herbs Winter Summer Monsoon Density IVI Density IVI Density IVI Anemone vitifolia Aconogonum sp Anaphalis triplinervis Bistorta sp Blechnum sp Cannabis sativa Capsella bursa-pastoris Cirsium sp Corydalis rutifolia Cynoglossum furcatum Fagopyrum dibotrys Fragaria indica Gallium asperifolium Geranium nepalense Gerardinia heterophylla Gnaphalium sp Heracleum sp Houttuynia cordata Hydrocotyl javanica Lepisorus nudus Mazus surculosus Oenanthe sp Oxalis corniculata Parthenocisus - - himalayana Periploca sp Pilea lineolatum Piptanthus nepalensis Plantago major Poa annua Polygonum capitatum Potentilla fulgens Pouzolzia sp Pteridium aquilinum Rosa sericea Rumex nepalensis Solanum viarum Stellaria sp Viola sp Vittaria sp Site -3 Dam site Species Frequency % Density (No./ha) Basal area (m 2 /ha) Trees Alnus nepalensis IVI WAPCOS Limited 6-13

122 Species Frequency % Density (No./ha) Basal area (m 2 /ha) 9 Cryptomeria japonica Cupressus sp Ilex sp Lyonia ovalifolia Morus sp Rhododendron campanulatum Rhododendron maddeni Shrubs Artemisia nilagirica Elaeagnus sp Gaultheria fragrantissima Prinsepia utilis Rubus ellipticus Plectranthus coetsa Spiraea canescens Herbs Winter Summer Monsoon Density IVI Density IVI Density IVI Anaphalis triplinervis Axonopus compressus Bidens pilosa Cannabis sativa Centella asiatica Cirsium sp Cynoglossum furcatum Fagopyrum dibotrys Fragaria indica Galinsoga parviflora Gallium asperifolium Gerardinia heterophylla Gnaphalium sp Houttuynia cordata Hydrocotyl javanica Inula cappa Leucas ciliata Lycopodium clavatum Mazus surculosus Nicandra physaloides Oxalis corniculata Parochetus communis Paspalum sp Pouzolzia hirta Pilea lineolatum Plantago major Polygonum capitatum Pteridium aquilinum Ranunculus scleratus Rubia cordifolia Rumex nepalensis Sedum multicaule IVI WAPCOS Limited 6-14

123 Species Frequency % Density (No./ha) Basal area (m 2 /ha) Selaginella sp Solanum viarum Stellaria sp Smythea sp Urtica dioca Viola sp Site4 : Near village Shakti Species Frequency % Density (No./ha) Basal area (m 2 /ha) Trees Alnus nepalensis Cryptomeria japonica Cupressus torulosa Eucalyptus sp Ficus roxburghii Macaranga denticulata Morus serrata Pinus wallichiana Quercus griffithii Schima khasiana Wendlandia puberula Shrubs Artemisia nilagirica Buddleja asiatica Cotoneaster sp Debregesia longifolia Desmodium sp Elaeagnus sp Indigofera dosua Maesa indica Philadelphus tomentosus Plectranthus coetsa Ribes glaciale Rubus ellipticus Saccharum spontaneum Viburnum erubescens Herbs Winter Summer Monsoon Density IVI Density IVI Density IVI Anaphalis triplinervis Anemone vitifolia Bidens pilosa Bistorta sp Centella asiatica Cynoglossum furcatum Drymaria cordata Fagopyrum dibotrys Fragaria indica IVI IVI WAPCOS Limited 6-15

124 Species Frequency % Density (No./ha) Basal area (m 2 /ha) Galinsoga parviflora Gallium asperifolium Gerardinia heterophylla Gnaphalium sp Houttuynia cordata Hydrocotyl javanica Inula cappa Lepisorus nudus Leucas ciliata Lycopodium clavatum Mazus surculosus Nicandra physaloides Oxalis corniculata Paspalum sp Pilea lineolatum Piptanthus nepalensis Plantago major Poa annua Polygonum capitatum Pouzolzia hirta Pteridium aquilinum Ranunculus adoxifolius Rubia cordifolia Rumex nepalensis Smythea sp Urtica dioca Site-5 : 1 km downstream of BTK Bridge site Species Frequency Density Basal IVI % (No./ha) area (m2/ha) Albizia lucida Alnus nepalensis Engelhardtia spicata Ficus roxburghii Lyonia ovalifolia Macaranga denticulata Myrica esculenta Quercus griffithii Rhus javanica Shrubs Artemisia nilagirica Buddleja asiatica Debregesia longifolia Desmodium sp Elaeagnus sp Maesa indica Mussaenda roxburghii Neillia thyrsiflora Oxospora paniculata IVI WAPCOS Limited 6-16

125 Species Frequency % Density (No./ha) Basal area (m2/ha) Plectranthus coetsa Rubus ellipticus Spirea canescens Viburnum erubescens Herbs Winter Summer Monsoon Density IVI Density IVI Density IVI Anaphalis triplinervis Arisaema tortuosum Bidens pilosa Centella asiatica Cirsium sp Cynoglossum furcatum Dicrocephala integrifolia Equisetum sp Fagopyrum dibotrys Fragaria indica Galinsoga parvifolia Gallium asperifolium Gerardinia heterophylla Gnaphalium sp Houttuynia cordata Hydrocotyle javanica Inula cappa Leucas ciliata Lycopodium clavatum Mazus surculosus Nicandra physaloides Osbeckia nutans Oxalis corniculata Plantago major Polygonum capitatum Polygonum hydropiper Polygonum runcinatum Pouzolzia hirta Ranunculus adoxifolius Rubia cordifolia Rumex nepalensis Smythea sp Solanum viarum Stellaria sp Urena lobata Urtica dioca Viola sp Site-6 : Near village Gispu Species Frequency % Density (No./ha) Basal area (m 2 /ha) Trees Albizia lucida Alnus nepalensis IVI IVI WAPCOS Limited 6-17

126 Species Frequency % Density (No./ha) Basal area (m 2 /ha) Engelhardtia spicata Ficus roxburghii Macaranga denticulata Quercus griffithii Schima khasiana Shrubs Artemesia nilagirica Buddleja asiatica Cotoneaster sp Debregaesia longifolia Mesea indica Neillia thyrsiflora Eleagnus sp Mussaenda roxburghii Rubus ellipticus Saccharum spontaneum Spirea canescens Viburnum erubescens Herbs Winter Summer Monsooon Density IVI Density IVI Density IVI Aconogonum sp Anaphalis triplinervis Bidens pilosa Centella asiatica Equisetum sp. Osmunda cinnamomea Corydalis rutifolia Cynoglossum furcatum Fagopyrum dibotrys Fragaria indica Gallium asperifolium Galinsoga parvifolia Geranium nepalense Gerardinia heterophylla Gnaphalium sp Hydrocotyle javanica Lepisorus nudus Lycopodium clavatum Mazus surculosus Oxalis corniculata Periploca sp Poa annua Polygonum capitatum Pouzolzia hirta Pteridium aquilinum Rubia cordifolia Rumex nepalensis Urtica dioca Vittaria elongata IVI WAPCOS Limited 6-18

127 Site-7 : Near Powerhouse site Species Frequency % Density (No./ha) Basal area (m2/ha) Albizia lucida Alnus nepalensis Erythirina arborescens Macaranga denticulata Quercus griffithii Schima khasiana Shrubs Artemesia nilagirica Cotoneaster sp Debregaesia longifolia Eleagnus sp Mesea indica Mussaenda roxburghii Neillia thyrsiflora Rubus ellipticus Saccharum spontaneum Spirea canescens Viburnum erubescens Herbs Winter Summer Monsoon Density IVI Density IVI Density IVI Anaphalis triplinervis Bidens pilosa Centella asiatica Cynoglossum furcatum Equisetum sp Fagopyrum dibotrys Fragaria indica Galinsoga parvifolia Houttuynia cordata Hydrocotyle javanica Lycopodium clavatum Mazus surculosus Oxalis corniculata Polygonum capitatum Pouzolzia hirta Rubia cordifolia Rumex nepalensis TABLE-6.6 Species Diversity Indices for different vegetation components at different sampling sites Vegetation component Shanon s Diversity Index (H) Pielou s Evenness Index (e) Winter Monsoon Summer Winter Monsoon Summer Site-1:Catchment site Trees Shrubs Herbs IVI WAPCOS Limited 6-19

128 Vegetation component Shanon s Diversity Index (H) Pielou s Evenness Index (e) Winter Monsoon Summer Winter Monsoon Summer Site-2:Submergence site Trees Shrubs Herbs Site-3:Dam site Trees Shrubs Herbs Site-4 : Near village Sakthi Trees Shrubs Herbs Site-5 1 km downstream of BTK Bridge Trees Shrubs Herbs Site-6 :Near village Gispu Trees Shrubs Herbs Site-7 : Near Power house site Trees Shrubs Herbs On perusal of data collected from field work at various sampling sites, the estimated volume of wood present in forests at village Shakti was maximum ( m 3 /ha) followed by forest in catchment area ( m 3 /ha). The details are given in Tables-6.7 and 6.8. The density in dam site and submergence area was m 3 /ha and m 3 /ha. TABLE-6.7 Estimated volume of wood (m 3 /ha) at different sampling sites Species Catchment site Submergence site Dam site Alnus nepalensis Betula alnoides 0.96 Cryptomeria japonica 2.67 Cupressus torulosa Engelhardtia spicata Erythirina arborescens 4.51 Ficus sp WAPCOS Limited 6-20

129 Hippophae salicifolia 2.68 Ilex sp Juglans regia 4.92 Lyonia ovalifolia Macaranga denticulata 4.77 Pinus wallichiana Populus gamblei 2.88 Quercus griffithii Rhododendron campanulatum Rhododendron medini 7.46 Rhododendron nerifolium 1.35 Salix sp Schima khasiana Zanthoxylum sp Total Species Near village Shakti 1km downstream of BTK bridge site Albizzia lucida Alnus nepalensis Churaksia tabularis - - Cupressus torulosa 9.40 Engelhardtia spicata 5.19 Eucalyptus sp Ficus roxburghii Glochidion acuminatum - Lyonia ovalifolia 3.50 Macaranga denticulata Morus serrata Myrica esculenta 3.22 Persea odoratissima - - Pinus wallichiana Quercus griffithii Rhus javanica 7.68 Schima khasiana Toona ciliata - - Total Species Near village Gispu Power house site Albizia lucida Alnus nepalensis Cupressus torulosa Pinus wallichiana Engelhardtia spicata Erythirina arborescens 3.5 Macaranga denticulata Cryptomeria japonica Quercus griffithii WAPCOS Limited 6-21

130 Ficus roxburghii 5.52 Eucalyptus sp. Schima khasiana Toona ciliate Total TABLE-6.8 Summary of Estimated volume of wood (m 3 /ha) at different sampling sites S. No. Sampling site Wood Volume (m 3 /ha) 1 Catchment site Submergence site Dam site Near village Shakti km downstream of BTK bridge site 6 Near village Gispu Power house site Flora under Threatened category No threatened category of plant species was encountered during the survey. The area showed no rare / endangered / vulnerable plant species as per IUCN categorization FIELD STUDIES ON VEGETATION AND FLORAL DIVERSITY BY RS ENVIROLINK TECHNOLOGIES PVT. LTD. A systematic enumeration of plant species (trees, Shrubs/under shrubs, Climbers, Herbs, Sedges and Grasses) based on primary field survey for project influence and non-influence zones have been prepared and is presented below in Tables 6.9 to 6.12 respectively. TABLE-6.9 S. No. List of Plant Species (Trees) Recorded in Project Area Botanical Name Family Influence zone Non- Influence zone 1 Abies pindrow Pinaceae P 2 Aesculus indica Hippocastanaceae P 3 Albizia procera Mimosaceae P P 4 Alnus nepalensis Ulmaceae P P 5 Rhododendron Ericaceae P arboreum 6 Cedrus deodara Pinaceae P 7 Celtis eriocarpa Ulmaceae P P 8 Cupressus torulosa Cuperassaceae P WAPCOS Limited 6-22

131 S. No. Botanical Name Family Influence zone Non- Influence zone 9 Juglans regia Juglandaceae P 10 Lyonia ovalifolia Ericaceae P P 11 Pinus wallichiana Pinaceae P 12 Populus ciliata Salicaceae P P 13 Pyrus pashia Rosaceae P P 14 Quercus semiserata Fagaceae P 15 Salix karelinii Salicaceae P 16 Toona serrata Meliaceae P 17 Engelhardtia spicata Juglandaceae P P 18 Pinus roxburghi Pinaceae P P 19 Ficus semicordata Moraceae P P 20 Larix sp. Pinaceae P 21 Myrica esculenta Myricaceae P 22 Syzygium cumini Myrtaceae P P 23 Bombax ceiba Bombacaceae P P 24 Phyllanthus emblica Euphorbiaceae P P 25 Quercus sp. Fagaceae P 26 Prunus cerasoides Rosaceae P P 27 Quercus Fagaceae P leucotrichophora 28 Morus alba Moraceae P 29 Malotus philippensis Euphorbiaceae P P 30 Erythrina variegata Fabaceae P 31 Castanea sativa Fagaceae P 32 Mahonia nepalensis Berberidaceae P P 33 Toona hexandra Meliaceae P 34 Sapium insigne Euphorbiaceae P P 35 Albizia julibrisin Mimosaceae P P 36 Betula alnoides Betulaceae P P 37 Ficus oligodon Moraceae P 38 Ilex fragilus Aquifoliaceae P 39 Erythrina arborscens Fabaceae P P 40 Grewia optiva Tiliaceae P P 41 Brassiopsis mitis Araliaceae P P S. No. TABLE-6.10 List of Plant Species (Shrubs) Recorded in Project Area Botanical Name Family Influence Nonzone Influence zone 1 Abelia triflora Caprifoliaceae P 2 Artemisia sp. Asteraceae P P 3 Asragalus Fabaceae P chlorostachys 4 Berberis angulosa Berberidaceae P WAPCOS Limited 6-23

132 S. No. Botanical Name Family Influence zone Non- Influence zone 5 Barlaria cristata Acanthaceae P P 6 Buddleja asiatica Scrophulariaceae P P 7 Cotoneaster Rosaceae P P accuminatus 8 Coriaria nepalensis Corariaceae P P 9 Cotoneaster Rosaceae P microphyllus 10 Desmodium Fabaceae P macrophyllum 11 Daphne papyracea Thymelaeaceae P 12 Desmodium elegans Fabaceae P 13 Deutzia compacta Rosaceae P 14 Elaeagnus parvifolia Elaeagnaceae P P 15 Girardinia diversifolia Urticaceae P P 16 Hypericum Hypericaceae P oblongifolium 17 Indigofera heterantha Fabaceae P 18 Jasminum humile Oleaceae P 19 Leptodermis lanceolata Rubiaceae P 20 Lonicera sp. Caprifoliaceae P 21 Philadelphus Hydrangeaceae P tomentosus 22 Princepia utilis Rosaceae P 23 Rubus ellipticus Rosaceae P P 24 R. prostrata Rosaceae P 25 Rabdosia rugosa Lamiaceae P P 26 Rhamnus virgatus Rhamnaceae P 27 Rosa brunonii Rosaceae P P 28 Rubus foliolosus Rosaceae P P 29 Sarcococca saligna Buxaceae P 30 Sorbaria tomentosa Rosaceae P P 31 Spiraea canascens Rosaceae P 32 Urtica dioica Urticaeae P P 33 Wikstroemia canascens Thymelaeaceae P 34 Woodfordia fruticosa Lythraceae P P 35 Zanthoxylum Rutaceae P P nepalensis 36 Hippophae salicifolia Elaeagnaceae P P 37 Rhododendron sp. Ericaeae P P 38 Spiraea sp. Rosaceae P 39 Spermadictylon Rubiaceae P sauveolens 40 Euonymus sp. Celastraceae P 41 Xanthium indicum Asteraceae P P 42 Eupatorium adenophorum Asteraceae P P WAPCOS Limited 6-24

133 S. No. Botanical Name Family Influence zone Non- Influence zone 43 Flemingia alata Fabaceae P 44 Inula cuspidata Asteraceae P P 45 Punica granatum Punicaceae P P 46 Asparagus adscendens Liliaceae P P 47 Anisomeles indica Lamiaceae P P 48 Euphorbia royleana Euphorbiaceae P 49 Boehmeria platyphyla Urticaceae P 50 Buddleja paniculata Scrophulariaceae P 51 Debregeasia longifolia Urticaceae P P 52 Debregeasia sp. Urticaceae P 53 Elscholtzia sp. Lamiaceae P 54 Strobilanthes sp. Acanthaceae P 55 Arundinaria nepalensis Poaceae P 56 Baoninghausenia Rutaceae P albiflora 57 Gaultheria nummularis Ericaceae P P 58 Gaultheria sp. Ericaceae P 59 Rhus javanica Anacardiaceae P P 60 Ribes sp. Grossulariaceae P 61 Rhus parviflora Anacardiaceae P 62 Vitex negundo Verbenaceae P 63 Rhododendron sp Ericaceae P 64 Lantana camara Verbenaceae P P 65 Randia tetrasperma Rubiaceae P 66 Caryopteris odorata Verbenaceae P 67 Murraya koenigii Rutaceae P P 68 Inula cappa Asteraceae P S. No. TABLE-6.11 List of Plant Species (Climbers) Recorded in Project Area Botanical Name Family Influenc e zone Non- Influence zone 1 Clematis sp Ranunculaceae P P 2 Cuscuta reflexa Cuscutaceae P P 3 Cissampelos pareira Menispermaceae P P 4 Ficus hederacea Moraceae P P 5 Hedera nepalensis Araliaceae P P 6 Rubia cordifolia Rubiaceae P 7 Smilax aspra Smilacaceae P 8 Jasminum officinale Oleaceae P 9 Vitis sp. Vitaceae P 10 Periploca calophylla Asclepediaceae P 11 Stephania glabra Menispermaceae P 12 S. biternata Menispermaceae P P WAPCOS Limited 6-25

134 S. No. TABLE-6.12 List of Herbs, Sedges and Grasses Recorded in Project Area Botanical Name Family Influence zone Non- Influence zone 1 Aconogonum molle Polygonaceae P P 2 Agrimonia pilosa Rosaceae P 3 Alpuda mutica Poaceae P P 4 Anaphalis contorta Asteraceae P P 5 Andropogon controtus Poaceae P P 6 Androsace sp. Primulaceae P 7 Anemone sp. Ranunculaceae P 8 Aquilegia pubiflora Aquifoliaceae P 9 Arabis sp. Brassicaceae P P 10 Arctium lappa Asteraceae P 11 Arenaria sp. Caryophyllaceae P P 12 Arisaema sp. Araceae P P 13 Bergenia ciliata Saxifragaceae P 14 Campanula sp. Campanulaceae P P 15 Cerastium sp. Caryophyllaceae P P 16 Cirsium verutum Asteraceae P P 17 Cynoglosum lanciolatum Boraginaceae P P 18 Epilobium sp. Onagraceae P P 19 Euphorbia hirta Euphorbiaceae P P 20 Fragaria vestita Rosaceae P P 21 F. nubicola Rosaceae P 22 Galium sp. Rubiaceae P P 23 Geranium sp. Geraniaceae P P 24 Hypericum sp. Hypericaceae P 25 Impatiens sp. Balsaminaceae P P 26 Kylinga sp. Cyperaceae P P 27 Lespedeza sp. Fabaceae P 28 Lotus corniculatus Fabaceae P 29 Mentha longifolia Lamiaceae P P 30 Micromeria biflora Lamiaceae P P 31 Nepeta sp. Lamiaceae P 32 Origanum vulgare Lamiaceae P P 33 Oxalis acetocella Oxalidaceae P P 34 Phytolacca acinosa Phytolaccaceae P 35 Pimpinella sp. Apiaceae P 36 Plantago himalaica Plantaginaceae P P 37 Potentilla sp. Rosaceae P 38 Rumex hastatus Polygonaceae P P 39 Ranunculus sp. Ranunculaceae P 40 Rosularea sp. Crassulceae P 41 Rumex nepalensis Polygonaceae P P WAPCOS Limited 6-26

135 S. No. Botanical Name Family Influence zone Non- Influence zone 42 Salvia sp. Lamiaceae P 43 Stellaria media Caryophyllaceae P P 44 Thalictrum sp. Ranunculaceae P 45 Thymus linearis Lamiaceae P 46 Trigonella corniculata Polygonaceae P P 47 Viola betonicifolia Violaceae P 48 Verbascum thapsus Scrophulariaceae P P 49 Viola pilosa Violaceae P P 50 Bidens pilosa Asteraceae P P 51 Majus sp. Scrophulariaceae P P 52 Cynodon dactylon Poaceae P P 53 Cyperus sp. Cyperaceae P P 54 Aeschynanthus Gesneriaceae P nepalensis 55 Sedum sp. Crassulaceae P 56 Drosera sp. Droseraceae P 57 Lecanthes sp. Urticaceae P 58 Pilea umbrosa Urticaceae P P 59 Hedychium spicatum Zingiberaceae P 60 Campylotropis speciosa Fabaceae P 61 Ainsliea aptera Asteraceae P 62 Aconogonum sp. Polygonaceae P 63 Parochetus communis Fabaceae P 64 Prunella vulgaris Lamiaceae P 65 Acorus calamus Araceae P P 66 Primula macrophyla Primulaceae P 67 P. sikkimensis Primulaceae P 68 Boerhavia diffusa Nictaginaceae P P 69 Senecio sp. Asteraceae P 70 Cicerbita sp. Asteraceae P 71 Scutellaria sp. Scrophulariaceae P 72 Polygonum sp. Polygonaceae P 73 Roscoea purpurea Zingiberaceae P 74 Leucas lanata Lamiaceae P P 75 Solanum nigrum Solanaceae P P 76 Gynura hispida Asteraceae P P 77 Cassia occidentalis Caesalpinaceae P P 78 Sida sp. Malvaceae P 79 Hypoxis aurea Liliaceae P P 80 Cynotis vaga Commelinaceae P P 81 Geranium occelatum Geraniaceae P P 82 Anemone vitifolia Ranunculaceae P 83 Lespedeja juncea Fabaceae P 84 Conyza japonica Asteraceae P P 85 Gynura nepalensis Asteraceae P P WAPCOS Limited 6-27

136 S. No. Botanical Name Family Influence zone Non- Influence zone 86 Chenopodium album Chenopodiaceae P P 87 Sida rhomboidea Malvaceae P P 88 Cymbopogon sp. Poaceae P P VEGETATION COMMUNITY STRUCTURE Methodology To study community structure for terrestrial ecology quadrat sampling mode was followed. Sampling consisted of ten randomly placed quadrats of 10m x 10m size for trees, twenty quadrats of 5m x 5m size for saplings and shrubs and twenty quadrats of 1m x 1m for herbs were laid. The size and number of quadrats needed were determined using the species- area curve (Misra, 1968). The individuals falling within the range of cm cbh were designated as shrubs. The individuals having cbh more than 31.5 cm were recorded as trees. The data on vegetation has been analysed quantitatively for density, dominance, frequency (Curtis & McIntosh, 1950). The Important Value Index (IVI) is sum of relative density, relative dominance and relative frequency. The diversity index is calculated by using Shannon-Wiener Diversity Index (Shannon Wiener, 1963). Shannon-Wiener Diversity Index (H) = - p i ln ( p i ) Here, pi is the proportion of total number of species made up of the ith species. Sampling Sites The study area was divided in to following sampling sites: 1. Dam site (Right bank) - Submergence Area 2. Dam site (Left bank) - Submergence Area 3. Near Confluence of Nyamjang Chhu and Taksang Chhu 4. Near Namstring Bridge area 5. Powerhouse site The sampling locations are shown in Figure-6.1. Dam site (Right bank) - Submergence Area The proposed dam site is near the village Zimithang on the river Nyamjang Chhu. Right bank of river is composed of mixed evergreen forests with Pine forest at higher elevation on hills. The most dominant trees are Alnus nepalensis, Lyonia ovalifolia, Quercus spp, Prunus cerasoides, Albizia procera etc. at lower elevation and near river banks. At higher elevation Pinus wallichiana, Engelhardtia spicata and Juglans regia are dominant. The tree density is about 620 trees per hectare and diversity index is The shrub WAPCOS Limited 6-28

137 layer is composed of Elaeagnus parviflora the most dominanting nearby the river basin. Other common shrub species are Artemisia nilagirica, Indigofera heterantha, Rhus javanica, Rubus ellipticus, Zanthoxylum nepalensis, Rhododendron sp. Hippophae salicifolia, Gaultheria fragrantissima, Rubus sp. The most common shrubs on hill are Rhododendron sp., Gultheria fragrantissima, Deberegeasia longifolia, Arundinaria nepalensis, etc. On the right bank among herbs Impatiens sp,. Gallium sp., Chenopodium album and Polygonum sp. show high dominance. Arenaia sp., Bidens pilosa, Euphorbia hirta, Verbascum thapsus, etc are found with moderate dominance. Dam site (Left bank) - Submergence Area The left bank of river is scrub land on the hills and degraded vegetation is found near by the river basin. Elaeagnus parviflora also dominantes the left bank of the river followed by shrubs like Artemisia nilagirica, Indigofera heterantha, Rhus javanica, Rubus ellipticus, Zanthoxylum nepalensis and Rhododendron sp. Hippophae salicifolia, Gaultheria fragrantissima, Rubus sp. etc. The herbs layer is prominent on the left bank of the river. Acorus calamus is most dominant with Agrimonia pilosa, Arenaria sp, Fragaria vestita, Gallium sp, Parocheus communis, Rumex nepalensis, Viola betonicifolia, etc. Near Confluence of Nyamjang Chhu and Taksang Chhu The area is with mixed moist deciduous forests on both the sides of the River bank. The study was carried out on the left bank of the Nyamjang Chhu river. In tree composition Lyonia ovalifolia, and Alnus nepalensis are most frequent with Engelhardtia spicata, Albizia procera, Juglans regia, Mahonia alba and Toona serrata are found with moderate dominance. In shrub layer Aconogonum sp. is present with maximum dominance and frequently found on the right bank of the Nyamjang Chhu River, in association with Artemisia nilagirica which is frequent on road side, agricultural boundary and near human habitat. Debregeasia longifolia, Gaultheria fragrantissima, Rubus sp., Spiraea sp., and Xanthium indicum are moderately present. Near Namstring Bridge Area The hills are with grasses and sparse shrubs and trees near by the ridges. The shrub layer is only prominent near the river banks. The dominant shrubs are Artemisia nilagirica, Lantana camara on river bank because of human habitation. The other common shrubs are Woodfordia fructicosa, Murraya koenigii, Zanthoxylum nepalensis, Punica granatum and Rubus ellipticus. The most dominant Sedges on the hills are Lemon grass (Cymbopogon flexuosus) with small trees of aonla (Phyllanthus emblica). WAPCOS Limited 6-29

138 Power House Site At the power house site the tree canopy is spars which is composed of Ficus oligodon, Albizia procera, Mallotus philippensis, Grewia optiva, etc. The middle layer is composed of shrubs like Artemisia nilagirica, Canabis sativa, Debregeasia longifolia, Desmodium sp., Indigofera heterantha, Lantana camara, Woodfordia fruticosa. Phyllanthus emblica is dominant over the hills near the power house site with ground vegetation covered by Cymbopogon flexuosus. The quantitatively analyzed data on vegetation for density, dominance, frequency, IVI etc at different studied sites s given in Table-6.12 to TABLE-6.13 Community characteristics of tree and shrub layers at SITE-I S. No. Species Densi ty IVI Frequency (%) (No./ ha) Basal area (m 2 /ha) Trees Albizia lucida Alnus nepalensis Erythirina arborescens Macaranga denticulate Quercus griffithii Schima khasiana Total 355 Shrubs Artemisia nilagarica Drynaria propinqua Elaeagnus sp Gaultheria fragrantissima Prinsepia utilis Rhus javanica Rubus ellipticus Rubus rugosus Plectranthus coetsa Spiraea canescens Total 2065 WAPCOS Limited 6-30

139 WAPCOS Limited 6-31

140 S. No. TABLE-6.14 Community characteristics of herbaceous layer at SITE-I Season Pre Monsoon Monsoon Winter Density Frequency IVI Density Frequency IVI Density Frequency (per (%) (per ha) (%) (per ha) (%) Species Name ha) 1 Ageratum conizoides Amaranthus hybridus Anaphalis contorta Anaphalis triplinervis Arenaria sp Arisaema vitifolia Bidens pilosa Cannabis sativa Chenopodium album Crassocephalum 10 crepidioides Cynoglossum furcatum Cynotis vaga Euphorbia hirta Fagopyrum dibotrys Fragaria nubicola Fragaria vestita Galinsoga parviflora Gallium sp Gnephlium sp Gynura nepalensis Houttuynia cordata Hydrocotile javanica Hypericum sp Impatiens sp IVI WAPCOS Limited 6-32

141 S. No. Season Pre Monsoon Monsoon Winter Density (per Frequency (%) IVI Density (per ha) Frequency (%) IVI Density (per ha) Frequency (%) Species Name ha) 25 Inula cappa Kylinga sp Oxalis acetocella Oxalis corniculat Persicaria pubescens Piper sylvaticum Plantago major Polygonum capitatum Pteridium aquilinum Ranunculus scleratus Rubia cordifolia Scutellaria sp Smythea sp Solanum nigrum Thalictrum sp Urtica dioica Verbascum thapsus Viola betonicifolia IVI WAPCOS Limited 6-33

142 TABLE-6.15 Community characteristics of tree and shrub layers :SITE-II S. No. Species Basal IVI Frequency (%) Density (No./ha) area (m 2 /ha) Trees Alnus nepalensis Betula alnoides Cupressus sp Erythrina arborescens Juglans regia Lyonia ovalifolia Macaranga denticulata Populus gamblei Quercus griffithii Rhododendron campanulatum Rhododendron nerifolium Salix sp Total 270 Shrubs Artemisia nilagarica Drynaria propinqua Indigofera dosua Elaeagnus sp Gaultheria fragrantissima Plectranthus coetsa Prinsepia utilis Rhus javanica Rubus ellipticus Rubus rugosus Spiraea canescens Total 3009 WAPCOS Limited 6-34

143 TABLE-6.16 Community characteristics of herbaceous layer at SITE-II S. No. Season Pre Monsoon Monsoon Winter Species Name Density (per ha) Frequency (%) IVI 1 Acorus calamus Density Frequency (per ha) (%) IVI Density Frequency (per ha) (%) 2 Ageratum conizoides Agrimonia pilosa Ainsliea aptera Amaranthus hybridus Anaphalis contorta Anaphalis triplinervis Arenaria sp Arisaema vitifolia Arundinaria sp Bidens pilosa Bistorta sp Cannabis sativa Crassocephalum crepidioides Cynoglossum furcatum Cynotis vaga Cyperus sp Fagopyrum dibotrys Fragaria nubicola Fragaria vestita Gallium sp Geranium occelatum IVI WAPCOS Limited 6-35

144 S. No. Season Pre Monsoon Monsoon Winter Species Name Density (per ha) Frequency (%) IVI Density Frequency (per ha) (%) 23 Gnaphalium sp IVI Density Frequency (per ha) (%) 24 Houttuynia cordata Hydrocotyle javanica Impatiens sp Inula cappa Lecanthes sp Lepisorus sp Mazus serculosus Origanum vulgare Oxalis acetocella Oxalis corniculat Parochetus communis Persicaria pubescens Pilea umbrosa Plantago himalaica Polygonum capitatum Potentilla sp Pteridium aquilinum Rubia cordifolia Rumex nepalensis Scutellaria sp Sedum multicaule Solanum nigrum Stellaria media IVI WAPCOS Limited 6-36

145 S. No. Season Pre Monsoon Monsoon Winter Species Name Density (per ha) Frequency (%) IVI 47 Verbascum thapsus Viola betonicifolia Density Frequency (per ha) (%) IVI Density Frequency (per ha) (%) IVI WAPCOS Limited 6-37

146 TABLE-6.17 Community characteristics of tree and shrub layers: Site-III Species Frequency Density Basal area IVI (%) (No./ha) (m 2 /ha) Trees Albizia lucida Alnus nepalensis Engelhardtia spicata Ficus roxburghii Lyonia ovalifolia Macaranga denticulata Myrica esculenta Quercus griffithii Rhus javanica Shrubs Artemisia nilagirica Buddleja asiatica Debregesia longifolia Desmodium sp Elaeagnus sp Indigofera dosua Measa indica Neillia thyrsiflora Plectranthus coetsa Rubus ellipticus Saccharum spontaneum Schefflera venulosa Spiraea canescens Thysanolaena maxima Viburnum erubescens WAPCOS Limited 6-38

147 Species Name TABLE-6.18 Community characteristics of herbaceous layer : SITE-III S. No. Season Pre Monsoon Monsoon Winter Density Frequency IVI Frequency IVI Frequency (per ha) (%) (%) (%) Density (per ha) Density (per ha) 1 Anaphalis contorta Anaphalis triplinervis Bidens pilosa Bistorta sp Cannabis sativa Centella asiatica Chenopodium album Cymbopogan 8 flexuosus Cynodon dactylon Cynoglossum 10 furcatum Cyperus sp Drymaria cordata Euphorbia hirta Fagopyrum dibotrys Fragaria vestita Galinsoga parviflora Galium sp Gnaphalium sp Houttuyia cordata Impatiens sp IVI WAPCOS Limited 6-39

148 S. No. Season Pre Monsoon Monsoon Winter Density (per ha) Frequency (%) IVI Density (per Frequency (%) IVI Density (per Frequency (%) IVI Species Name ha) ha) 21 Inula cappa Lecanthes 22 penduncularis Lepisorus sp Lycopodium clavatum Lycopodium sp Mazus surculosus Nicandra physaloides Oxalis acetocella Oxalis corniculata Plantago major Polygonum capitatum Potentilla sp Pouzolzia hirta Pteridium aquilinum Ranunculus scleratus Smythea sp Solanum viarum Stellaria media Urtica dioca Viola betonicifolia WAPCOS Limited 6-40

149 Species TABLE-6.19 Community characteristics of tree and shrub layers: Site-IV Frequency (%) Density (No./ha) Basal area (m 2 /ha) Trees Albizia lucida Brassiopsis glomerulata Churaksia tabularis Cryptomeria japonica Cupressus torulosa Ficus roxburghii Glochidion acuminatum Hovenia dulcis Macaranga denticulata Persea odoratissima Pinus wallichiana Quercus griffithii Rhus javanica Schima khasiana Toona ciliata Wendlandia puberula Shrubs Artemisia nilagarica Buddleja asiatica Debregesia longifolia Desmodium sp Elaeagnus sp Indigofera dosua Measa indica Neillia thyrsiflora Plectranthus coetsa Rubus ellipticus Saccharum spontaneum Schefflera venulosa Spiraea canescens Thysanolaena maxima Viburnum erubescens IVI WAPCOS Limited 6-41

150 TABLE-6.20 Community characteristics of herbaceous layer : SITE-IV S. No. Season Pre Monsoon Monsoon Winter Species Name Density (per ha) Frequency (%) IVI Density (per ha) Frequency (%) 1 Aconogonum sp Anaphalis contorta IVI Density Frequency (per ha) (%) 3 Anaphalis triplinervis Bidens pilosa Cannabis sativa Centella asiatica Cerastrium sp Chenopodium album Corydalis rutifolia Cynoglossum furcatum Cyperus sp Fagopyrum dibotrys Fragaria indica Fragaria vestita Galinsoga parvifolia Gallium asperifolium Gentiana ornata Geranium nepalense Girardinia heterophylla Gnaphalium sp Heracleum sp IVI WAPCOS Limited 6-42

151 S. No. Season Pre Monsoon Monsoon Winter Species Name Density (per ha) Frequency (%) IVI Density (per ha) Frequency (%) IVI Density Frequency (per ha) (%) 22 Hydrocotyle javanica Inula cappa Lepisorus nudus Lycopodium clavatum Mazus surculosus Oenanthe sp Osmunda cinnamomea Oxalis acetocella Oxalis corniculata Periploca sp Poa annua Polygonum capitatum Polygonum hydropiper Potentilla sp Pouzolzia hirta Pteridium aquilinum Rubia cordifolia Rumex nepalensis Scutellaria sp Stellaria media Urtica dioica Viola betonicifolia Vittaria elongata IVI WAPCOS Limited 6-43

152 TABLE-6.21 Community characteristics of tree and shrub layers: Site-V Species Frequency Density Basal area IVI (%) (No./ha) (m 2 /ha) Trees Albizia lucida Alnus nepalensis Engelhardtia spicata Ficus roxburghii Macaranga denticulata Quercus griffithii Schima khasiana Shrubs Artemesia nilagarica Buddleja asiatica Cotoneaster sp Debregaesia longifolia Mesea indica Neillia thyrsiflora Elaeagnus sp Rubus ellipticus Saccharum spontaneum Spiraea canescens Viburnum erubescens WAPCOS Limited 6-44

153 S. No. TABLE-6.22 Community characteristics of herbaceous layer : SITE-V Season Pre Monsoon Monsoon Winter Density Density Density Frequency Frequency Frequency (per IVI (per IVI (per (%) (%) (%) Species Name ha) ha) ha) 1 Aconoginium sp Ageratum conizoides Anaphais triplinervis Anaphalis contorta Arundinaria sp Begonia nepalensis Bidens pilosa Cannabis sativa Centella asiatica Cerastrium sp Chenopodium album Crassocephalum 12 crepidioides Cymbopogan flexuosus Cynodon dactylon Cynoglossum furcatum Cynotis vaga Drymaria cordata Eqisetum sp Euphorbia hirta Fragaria nubicola Fragaria vestita IVI WAPCOS Limited 6-45

154 S. No. Season Pre Monsoon Monsoon Winter Density Density Density Frequency Frequency Frequency (per IVI (per IVI (per (%) (%) (%) Species Name ha) ha) ha) 22 Galisansoga parvifolia Gynura nepalensis Impatiens sp Mazus surculosus Oxalis acetocella Oxalis corniculata Partheniumsp Pilea sp Poa annua Polygonum capitatum Pteridium aquilinum Ranunculus adoxifolius Ranunculus scleratus Scutellaria sp Solanum nigrum Solanum viarum Stellaria media Thalictrum sp Urtica dioica Verbascum thapsus Viola betonicifolia IVI WAPCOS Limited 6-46

155 TABLE-6.23 Community characteristics of tree and shrub layers: Site-VI S. No. Species Frequency (%) Trees Shrubs Total Density (No./ha) Basal area (m 2 /ha) IVI Albizia procera Ficus oligodon Cryptomeria japonica Sapium insigne Engelhardtia spicata Grewia optiva Malotus philippensis Toona ciliata Albizia procera Ficus oligodon Cryptomeria japonica Total Artemesia nilagirica Buddleja asiatica Cotoneaster sp Debregaesia longifolia Elaeagnus sp Indigofera dosua Mesea indica Mussaenda roxburghii Rubus ellipticus Saccharum spontaneum Spiraea canescens Viburnum erubescens WAPCOS Limited 6-47

156 S. No. TABLE-6.24 Community characteristics of herbaceous layer : SITE-VI Season Pre Monsoon Monsoon Winter Density (per Frequency (%) IVI Density (per Frequency (%) IVI Density (per Frequency (%) Species Name ha) ha) ha) 1 Ageratum conizoides Agrimonia pilosa Anaphalis triplinervis Bidens pilosa Bistorta sp Cannabis sativa Centella asiatica Cerastrium sp Chenopodium album Chirata pumila Crassocephalum 11 crepidioides Cynoglossum furcatum Drymaria cordata Elatostema sp Euphorbia hirta Fagopyrum dibotrys Fragaria indica Fragaria vestita Galinsoga parviflora Gallium asperifolium Girardinia heterophylla IVI WAPCOS Limited 6-48

157 S. No. Season Pre Monsoon Monsoon Winter Density (per Frequency (%) IVI Density (per Frequency (%) IVI Density (per Frequency (%) Species Name ha) ha) ha) 22 Gnaphalium sp Houttuynia cordata Hydrocotile javanica Inula cappa Lepisorus nudus Lycopodium clavatum Mazus surculosus Origanum vulgare Oxalis corniculata Plantago himalaica Plantago major Poa annua Polygonum capitatum Pouzolzia hirta Pteridium aquilinum Ranunculus adoxifolius Rubus cordifolia Rumex sp Smythea sp Solanum nigrum Stellaria media Thalictrum sp Urtica dioica IVI WAPCOS Limited 6-49

158 The diversity indicies of trees and shrubs at different sampling locations is given in Table The diversity indicies of herbs at different sampling locations is given in Table TABLE Diversity indicies of trees and shrubs at different sampling locations Sampling Site Shannon- Weiner Diversity Index H Evenness Index E Shannon- Weiner Diversity Index H Evenness Index E Trees Shrubs Site I Site II Site III Site IV Site V Site VI Site Site I Site II Site III Site IV Site V Site VI TABLE-6.26 Diversity indicies of herbs at different sampling locations Season Shannon- Weiner Evenness Index Diversity Index E H Pre Monsoon Monsoon Winter Pre Monsoon Monsoon Winter Pre Monsoon Monsoon Winter Pre Monsoon Monsoon Winter Pre Monsoon Monsoon Winter Pre Monsoon Monsoon Winter WAPCOS Limited 6-50

159 6.3 Fauna The wildlife in the project area has been listed based on the observation during the field visit and information collected from the local people. The list of faunal speies observed in the study aera as prepared by WAPCOS Ltd. is given in Table The list of mammals and birds as reported by RS Envirolink Technologies Pvt. Ltd. is given in Tables-6.28 and 6.29 respectively. TABLE 6.27 List of wildlife reported in the study area Sl.No. Common name Zoological name A. MAMMALS 1 Leopard Panthera pardus 2 Wild Dog Cuon alpinus 3 Jungle Cat Felis chaus 4 Himalayan Black Bear Selenarctos thibetanus 5 Assamese Monkey Macaca assamensis 6 Wild pig Sus scrofa 7 Chinese Porcupine Hystrix brachyura 8 Bay bamboo rat Cannomys badius 9 Small Indian civet Viverricula indica 10 Indian grey mongoose Herpestes edwardsii 11 Crab eating mongoose Herpestes urva B. BIRDS 1 Green Backed tit Parus monticolus 2 Brown crested tit P. dichrous 3 Wall creeper Tichodroma muraria 4 Mrs. Gould s Sunbird Aothopyga gouldiae 5 Purple Sunbird Nectarina asiatica 6 Great Hill Barbet Megalaina virens 7 Common Maina Acridotheres tristis 8 Wiretailed Swallow Hirundo sinthii 9 Scarlet Minivet Pericorocotus flammeus 10 Brown Dipper Cinchus pallasii 11 Red turtle Dove Streptopelia tranquebarica 12 Moorhen Gallinula chloropus 13 Red vented Bulbul Pycnonotus cafer 14 Striated Green Bulbul P. stericatus 15 Olive Bulbul Hypsipetus viride 16 Black Bulbul H. madagascariensis 17 Maroon Oriole Oriolus trialli 18 Common Hawk Cuckoo Cuculus varius 19 Pied crested Cuckoo Clamator jacobinus WAPCOS Limited 6-51

160 Sl.No. Common name Zoological name 20 Black-headed Rufous Lanius schach Backed Shrike 21 Blue Whistling Thrush Myiophonus caerula 22 Little forktail Enicurrus acouleri 23 Black Breasted Thrush Turdus dissimilis 24 Grey winged Black Bird Turdus boulboul 25 Paradise Flycatcher Terpsiphon paradise C. REPTILES 1 Brown-spotted pitviper Protobothrops mucrosquamatus 2 Jerdon s pitviper Protobothrops jerdoni 3 Mountain pitviper Ovophis monticola 4 Yellow bellied worm-snake Trachischium tenuiceps 5 Lizard Monitor Varanus bengalensis 6 Sikkim Sunskink Scinella sikimmensis 7 Stremside forest skink Sphenomorphus maculates 8 Three Striped Roofed turtle Kachuga dhangoka D. AMPHIBIANS 1 Bufo melanostictus 2 Bufo himalayanas 3 Megophrys parva 4 Amolops afghanus 5 Rana danielli 6 Rana gerbillus 7 Rana taipehensis 8 Rana erythraena 9 Philautus annandalii 10 Rhacophorus bipunctatus Source : WAPCOS Ltd. WAPCOS Limited 6-52

161 TABLE 6.28 List of mammals reported in the study area Sl. No. Common Name Zoological Name 1 Barking Deer Muntiacus muntjac 2 Arunachal macaque Macaca munzala 3 Hoary-bellied Squirrel Callosciurus pygerythrus 4 Hog Deer Axis porcinus 5 Leopard Cat Felis bengalis 6 Common Palm Civet Paradoxurus hermaphroditus 7 Porcupine Hystrix indica 8 Wild Pig Sus scrofa 9 Himalayan Black Bear Selenarcods thibetanus 10 Hairy Footed Flying Squirrel Belomys pearsoni 11 Himalayan or Masked Palm civet Paguma larvata 12 Himalayan Goral Nemorhaedus goral 13 Musk Deer Moschus moschiferus 14 Red Panda Ailurus fulgens 15 Snow Leopard Panthera uncial 16 Takin Budorcas taxicolor 17 Sambar Cervus unicolor Source: RS Envirolink Technologies Pvt. Ltd. TABLE 6.29 List of birds reported in the study area Sl. No. Common Name Zoological Name Family 1 Crested Serpent Eagle Spilornis cheela Accipitridae 2 Eurasian Griffon Gyps fulvus Accipitridae 3 Golden Eagle Aquila chrysaetos Accipitridae 4 Himalayan Griffon Gyps himalayensis Accipitridae 5 Black-lored Tit Parus xanthogenys Aegithalidae 6 Black-throated Tit Aegithalos concinnus Aegithalidae 7 Great Tit Parus major Aegithalidae 8 Green-backed Tit Parus monticolus Aegithalidae 9 Grey-crested Tit Parus dichrous Aegithalidae 10 House Swift Apus affinis Apodidae 11 Winter Wren Troglodytes troglodytes Certhiidae 12 Rusty-flanked Treecreeper Certhia nipalensis Certhiidae 13 Black-faced Warbler Abroscopus schisticeps Cisticolidae 14 Blyth's Leaf Warbler Phylloscopus reguloides Cisticolidae 15 Broad-billed Warbler Tickellia hodgsoni Cisticolidae WAPCOS Limited 6-53

162 Sl. No. Common Name Zoological Name Family 16 Buff-barred Warbler Phylloscopus pulcher Cisticolidae Chestnut-crowned Bush 17 Warbler Cettia major Cisticolidae 18 Golden-spectacled Warbler Seicercus burkii Cisticolidae 19 Grey-hooded Warbler Seicercus xanthoschistos Cisticolidae 20 Tickell's Leaf Warbler Phyloscopus affinis Cisticolidae 21 White-spectacled Warbler Seicurcus affinis Cisticolidae 22 Yellow-browed Warbler Phylloscopus inornatus Cisticolidae 23 Emarald dove Chalcophaps indica Columbidae 24 Hill Pigeon Columba rupestris Columbidae 25 Mountain Imperial Pigeon Ducula badia Columbidae 26 Oriental Turtle Dove Streptopelia orientalis Columbidae 27 Speckled Wood Pigeon Columba hodgsonii Columbidae 28 Spotted Dove Streptopelia chinensis Columbidae 29 Wedge-tailed Green Pigeon Treron sphenura Columbidae 30 Yellow -billed Blue Magpie Urocissa flavirostris Columbidae Bar-winged Flycatcher 31 Shrike Hemipus picatus Corvidae 32 Black Drongo Dicrurus macrocerus Corvidae 33 Common Iora Aegithina tipia Corvidae Tephrodornis 34 Common Wodshrike pondicerianus Corvidae 35 Eurasian Jay Garrulus glandarius Corvidae 36 Ferruginous flycatcher Muscicapa ferruginea Corvidae 37 Large-billed Crow Corvus macrorhynchos Corvidae 38 Scarlet Minivet Pericrocotus flammeus Corvidae 39 Spotted Nutcracker Nucifraga caryocatactes Corvidae 40 Ultramarine Flycatcher Ficedula superciliaris Corvidae 41 Yellow-bellied Fantail Rhipidura albicollis Corvidae 42 Red-headed Bullfinch Pyrrhula erythrocephala Fringiillidae Mycerobas 43 Spot-winged Grosbeak melanozanthos Fringiillidae 44 White-browed Rosefinch Carpodacus thura Fringiillidae 45 Dark-breasted Rosefinch Carpodacus nipalensis Fringillidae 46 Dark-rumped Rosefinch Carpodacus edwardsii Fringillidae 47 Rock Bunting Emberiza cia Fringillidae 48 Grey-backed Shrike Lanius tephronotus Lanidae 49 Long-tailed Shrike Lanius schach Lanidae WAPCOS Limited 6-54

163 Sl. No. Common Name Zoological Name Family 50 Golden-throated Barbet Megalaima franklinii Megalaimidae 51 Great Barbet Megalaima virens Megalaimidae 52 Black Redstart Phoenicurus ochrurus Muscicapidae 53 Blue fronted Redstart Phoenicurus frontalis Muscicapidae 54 Blue Whistling Thrush Myophonus caeruleus Muscicapidae Chestnut-bellied Rock 55 Thrush Monticola rufiventris Muscicapidae 56 Golden Bush Robin Tarsiger chrysaeus Muscicapidae 57 Grey Bushchat Saxicolaferrea Muscicapidae Grey-headed Canary 58 Flycatcher Culicicapa ceylonensis Muscicapidae 59 Long-tailed Thrush Zoothera dixoni Muscicapidae 60 Mistle Thrush Turdus viscivorus Muscicapidae 61 Plumbeous Water Redstart Rhyacornis fuliginosus Muscicapidae White-capped Water Chaimarrornis 62 Redstart leucocephalus Muscicapidae Phoenicurus 63 Whitewinged Redstart erythrogaster Muscicapidae 64 Fire-tailed Sunbird Aethopyga ignicauda Nectarinidae Yellow-bellied Dicaeum 65 Flowerpecker melanoxanthum Nectarinidae 66 Eurasian Tree Sparrow Passer montanus Passeridae 67 Gold-naped Finch Pyrrhoplectes epauleta Passeridae 68 Grey Wagtail Motacila cinerea Passeridae 69 Grey-headed Bullfinch Pyrrhula erythaca Passeridae 70 White Wagtail Motacila alba Passeridae 71 Yellow Wagtail Motacilla flava Passeridae 72 Blood Pheasant Ithaginis cruentus Phasianidae Crimsonbreasted Dendrocopos 73 Woodpecker cathpharius Picidae Dendrocopos 74 Darjeeling Woodpecker darjellensis Picidae 75 Black Bulbul Hypsepetes leucocephalus Pycnonotidae 76 Red-vented Bulbul Pycnonotus cafer Pycnonotidae 77 Goldcrest Regulus regulus Regulidae 78 Wood Sandpiper Tringa glareola Scolocapidae 79 Black-chinned Yuhina Yuhina Nigrimenta Silvidae Black-faced Laughing 80 Thrush Garrulax affinis Silvidae WAPCOS Limited 6-55

164 Sl. No. Common Name Zoological Name Family 81 Chestnut-tailed Minla Minla strigula Silvidae 82 Cutia Cutia nipalensis Silvidae 83 Green Shrike Babbler Pteruthethius xanthochlorus Silvidae Lesser Necklaced Laughing 84 Thrush Garrulax monileger Silvidae 85 Red-tailed Minla Minla ignotincta Silvidae 86 Rufous Sibia Heterophasia capistrata Silvidae Rufous-necked Laughing 87 Thrush Garrulax ruficollis Silvidae 88 Rufous-vented Yuhina Yuhina occipitalis Silvidae 89 Spotted Laughing Thrush Garrulax ocellatus Silvidae Streak-breasted Scimitar 90 Babbler Pomatorhinus ruficollis Silvidae 91 Streaked Laughing Thrush Garrulax lineatus Silvidae 92 Streaked Wren Babbler Napotherabrevicaudata Silvidae 93 Striated Laughing Thrush Garrulax striatus Silvidae 94 Stripe-throated Yuhina Yuhina gularis Silvidae 95 Whiskered Yuhina Yuhina flavicollis Silvidae 96 White-naped Yuhina Yuhina bakeri Silvidae 97 Chestnut-bellied Nuthatch Sitta castanea Sittidae 98 White-tailed Nuthatch Sitta himalayensis Sittidae 99 Brown Hawk Owl Ninox scutulata Strigidae 100 Red-billed Leiothrix Leiothrix lutea Timaliidae 101 Common Hoopoe Upupa epops Upupidae 102 Eurasian Blackbird Turdus merula 103 Grey-winged Blackbird Turdus boulboul 104 Hill Prinia Prinia atrogularis 105 Oriental Hobby Falco severus 106 Rufous-winged Fulvetta Alcippe castaneceps 107 Silver-eared Mesia Leiothrix argentauris 108 White-collared Blackbird Turdus albocinctus 109 Yellow-breasted Greenfinch Carduelis spinoides Source: RS Envirolink Technologies Pvt. Ltd. Threatened fauna Out of 65 faunal species, 6 species fall under different Schedules of the Wild Life Protection Act The list is given in Table WAPCOS Limited 6-56

165 TABLE Details of Threatened categories of species found in the project area Species Threatened category Reference Cuon alpinus Schedule II Wildlife Protection Act, 1972 Herpestes edwardsii Schedule II[16 Wildlife Protection Act, 1972 Herpestes urva Schedule II[16 Wildlife Protection Act, 1972 Macaca assamensis Schedule II Part I [1A Wildlife Protection Act, 1972 Trachischium tenuiceps Schedule IV Wildlife Protection Act, 1972 Varanus bengalensis Schedule II Wildlife Protection Act, 1972 Source : WAPCOS Ltd. Protected Areas and Corridors for wild animals There is no Wildlife sanctuary, National park or Biosphere Reserve present within the study area. The project area does not come under any wildlife corridor. 6.4 AQUATIC ECOLOGY Methodology For enumeration of phytoplankton population, 100 l composite water samples were collected from the river surface up to 60 cm depth and were filtered through a 20 µm net to make 1 l of bulk sample. The bulk samples so collected were preserved in 2% formalin solution and were brought to the laboratory for analysis. Ten replicate water samples each of 15 ml were made out of the preserved 1 l bulk sample and were centrifuged at 1500 rpm for 10 minutes. After centrifuging, the volume of aliquot concentrate was measured. 0.1 ml of aliquot concentrate was used for enumeration of phytoplankton population in each replicate. A plankton chamber of 0.1 ml capacity was used for counting of plankton under a light microscope. The total number of planktons present in a litre of water sample was calculated using the following formula: N = (n x v x 100)/ V WAPCOS Limited 6-57

166 Where, N= Number of plankton per litre n = average number of plankton cells in 0.1 ml of aliquot concentrate v = volume of plankton concentrate (aliquot) V= volume of water from bulk sample centrifuged Phyto and zooplankton species diversity index was calculated using Shannon s species diversity index (H) formula taking the density values of each phytoplankton and zooplankton species into consideration. Shannon index of general diversity (H): - ΣP i log P i Where n i = density value for each species N = total density values Pi = density probability for each species = n i /N DENSITY AND DIVERSITY OF PLANKTONS Field Studies by WAPCOS Ltd. The density and diversity of phytoplankton in the river water was studied by collecting the water samples from two sites i.e. from Dam site and Submergence site. Samples were collected from river Nyamjangchhu for assessing the density and diversity of phytoplanktons and zooplanktons. The list of sampling sites covered by WAPCOS Ltd. is given in Table The sampling locations are shown in Figure-6.2. TABLE-6.31 Details of sampling sites for aquatic ecological survey Sampling Site Location Site-1 River Nyamjangchhu near Dam site Site-2 Submergence area Site-3 Taksangchhu Site-4 River Nyamjangchhu, 1 kmdownstream of BTK Bridge Site-5 River Nyamjangchhu near village Gispu Site-6 River Nyamjangchhu near Power House Site WAPCOS Limited 6-58

167 Phytoplanktons The results of phytoplankton density at various sampling sites for monsoon, winter, and summer season is given in Tables-6.32 to 6.34 respectively. The species diversity index of phytoplanktons at various sampling sites is given in Table A total of 7 phytoplankton species were recorded from the project site and their population was high during monsoon season (Refer Table 6.32). The phytoplankton communities were dominated by algae. Total population was quite low as compared to the rivers in the plains. TABLE-6.32 Density (No. per liter) of Phytoplankton in the study area (Monsoon season) Species Class Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Epithemia sp. Bacillariophyta Actinastrum sp. Chlorophyta Triploceros sp. Chlorophyta Anabaena sp. Cyanophyta Microcystis sp. Cyanophyta Spirulina sp. Cyanophyta Synechocystis sp. Cyanophyta Total Source : Field Studies by WAPCOS Ltd. TABLE-6.33 Density (No. per liter) of Phytoplankton in the study area (Winter season) Species Class Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Epithemia sp. Bacillariophyta Actinastrum sp. Chlorophyta Triploceros sp. Chlorophyta Anabaena sp. Cyanophyta Microcystis sp. Cyanophyta Spirulina sp. Cyanophyta Synechocystis sp. Cyanophyta Total Source : Field Studies by WAPCOS Ltd. WAPCOS Limited 6-59

168 TABLE-6.34 Density (No. per liter) of Phytoplankton in the study area (Summer season) Species Class Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Epithemia sp. Bacillariophyta Actinastrum sp. Chlorophyta Triploceros sp. Chlorophyta Anabaena sp. Cyanophyta Microcystis sp. Cyanophyta Spirulina sp. Cyanophyta Synechocystis sp. Cyanophyta Total Source : Field Studies by WAPCOS Ltd. TABLE-6.35 Species diversity index of Phytoplankton at different sampling sites Sampling site Phytoplankton diversity index (H) Winter Summer Monsoon Dam site Submergence area Taksangchhu River Nyamjangchhu, 1 kmdownstream of BTK Bridge River Nyamjangchhu near village Gispu River Nyamjangchhu near Power House Site Source : Field Studies by WAPCOS Ltd. Zooplanktons A total of 6 zooplankton species were recorded from the project site and their population was high during monsoon, winter and summer seasons (Refer Tables-6.36 to 6.38). Total population was quite low as compared to the rivers in the plains. The zooplankton population was higher in summer season as compared to winter season. The species diversity index of zooplanktons at various sampling sites is given in Table WAPCOS Limited 6-60

169 TABLE-6.36 Density (No. per liter) of Zooplankton (Monsoon season) Family Order Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Baetidae Ephemeroptera Ecdyonuridae Ephemeroptera Ephemeridae Ephemeroptera Caenidae Ephemeroptera Perlidae Plecoptera Psephinidae Coleoptera Total Source : Field Studies by WAPCOS Ltd. TABLE-6.37 Density (No. per liter) of Zooplankton (winter season) Family Order Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Baetidae Ephemeroptera Ecdyonuridae Ephemeroptera Ephemeridae Ephemeroptera Caenidae Ephemeroptera Perlidae Plecoptera Psephinidae Coleoptera Total Source : Field Studies by WAPCOS Ltd. TABLE-6.38 Density (No. per liter) of Zooplankton (summer season) Family Order Site-1 Site-2 Site-3 Site-4 Site-5 Site-6 Baetidae Ephemeroptera Ecdyonuridae Ephemeroptera Ephemeridae Ephemeroptera Caenidae Ephemeroptera Perlidae Plecoptera Psephinidae Coleoptera Total Source : Field Studies by WAPCOS Ltd. WAPCOS Limited 6-61

170 TABLE-6.39 Species diversity index of Zooplanktons at different sampling sites Sampling site Zooplankton diversity index (H) Winter Summer Monsoon Dam site Submergence area Taksangchhu River Nyamjangchhu, 1 km downstream of BTK Bridge River Nyamjangchhu near village Gispu River Nyamjangchhu near Power House Site Source : Field Studies by WAPCOS Ltd PRIMARY PRODUCTIVITY Methods The phytoplankton primary productivity was determined by light and dark bottle method (Wetzel and Likens 1991). The water samples were collected in light and dark BOD bottles. Three replicates were maintained for each sample. The experimental bottles were kept for 6 hours in the river from where the water samples were collected. Winkler s method was used for determination of oxygen in the light and dark bottles. Following formula was used for calculation of phytoplankton primary productivity. Gross Primary Productivity (GPP) (mgc/m 3 /hr) = (O 2 content of light bottle O 2 content of dark bottle) x 0.375x x Incubation hour. Net Primary Productivity (NPP) (mgc/m 3 /hr) = ( O 2 content of light bottle O 2 content of control bottle) x 0.375x x Incubation hour. WAPCOS Limited 6-62

171 The Primary productivity during monsoon, winter and summer seasons of study at various sampling sites is given in Table The primary productivity is low in the river due to low phytoplankton population and high velocity. TABLE 6.40 Primary Productivity at different sampling sites in river Nyamjangchhu Sites Gross Primary Productivity (gc/m 3 /day) Net Primary Productivity (gc/m 3 /day) Winter Summer Monsoon Winter Summer Monsoon Dam site Submergence area Taksangchhu River Nyamjangchhu, 1 kmdownstream of BTK Bridge River Nyamjangchhu near village Gispu River Nyamjangchhu near Power House Site Source : Field Studies by WAPCOS Ltd. FIELD STUDIES BY RS ENVIROLINK TECHNOLOGIES PVT. LTD. To study various parameters for aquatic ecology, survey was conducted and sampling was carried out at 6 different sites of the proposed hydro-electric project on Nyamjang Chhu in April 2008 and July 2008 for summer and monsoon seasons respectively. The samples were taken in the replicates at each site of the river. The average value was calculated for the result. Physico-chemical and biological parameters were analysed. The sites at which sampling was done are as follows: N1 N2 N3 N4 N5 N6 Submergence Area (Left bank) Down Stream of Dam Site (Right bank) Down Stream of Takshang Chhu (Right bank) Down Stream of BTK Bridge (Left bank) Down Stream of Namtsring Bridge (Left bank) Down Stream of Power House Site (Left bank) The sampling sites are shown in Figure-6.2. WAPCOS Limited 6-63

172 Biological Characteristics Rock surfaces, plant surfaces, leaf debris, logs, silt and sandy sediments and all other spaces in the stream provide habitats for different organisms. According to these habitats organisms are divided into plankton, benthos, nektons and neuston. River water was rich in all biotic richness. 24 species of phytobenthos were identified at different sampling sites of the proposed hydroelectric project (Table -6.41). The density of phytobenthos ranged from 6144 individual/m 2 to individual/m 2 at various sites. Macro invertebrate fauna comprised of families Heptageniidae, Baetidae, Epeorus, Hydropsychidae, Chironomidae and Perlidae (Table-6.42). Diversity and Evenness Index (Shannon & Weiner 1964) for phytobenthos have been worked out and are presented in Table Sr. No. TABLE-6.41 Phytobenthos identified at various sampling sites (summer season) Taxa N1 N2 N3 N4 N5 N6 Achnanthedium biasoletiana v. biasoletiana A. biasoletiana v. subatomus A. minutissima v. minutissima A. subhudsonis Adlafia muscora 6 Amphora pediculus Cocconeis placentula 8 Cymbella excisa 9 C. leavis C. tumida Diatoma mesodon D. tenue Encyonema minutum 14Gomphonema WAPCOS Limited 6-64

173 Sr. No. Taxa N1 N2 N3 N4 N5 N6 parvulum 15 Hippodonta spp Nitzschia fonticola N. linearis N. capitelata N. frustulum N. palea Navicula spp N. notha Reimeria sinuata Synedra 24 ulna Source: Field studies by RS Envirolink Technologies Pvt. Ltd. TABLE-6.42 Taxonomic composition of major Orders/Class constituting benthic macroinvertebrate assemblages at various sampling sites (summer season) Family/Class/Order N1 N2 N3 N4 N5 N6 Ephemeroptera Heptageniidae Baetidae Epeorus Trichoptera Hydropsychidae Diptera Chironomidae Plecoptera Perlidae Total could not be recorded Source: Field studies by RS Envirolink Technologies Pvt. Ltd. WAPCOS Limited 6-65

174 TABLE-6.43 Diversity and Evenness Index- summer season Sampling site H (Diversity) E (Evenness) N N N N N N Source: Field studies by RS Envirolink Technologies Pvt. Ltd. 6.5 FISHERIES There is no fish landing centre in project area. It was also observed during field visit that no large scale fishing activities are being practiced by the population in and around the project area. During interaction with the locals and fishery department it was confirmed that there are no permanent and fishermen in the project area. However, few locals are involved in fishing activities to augment their income. No family is fully dependent on fishery for earning his living. The fisheries is done mostly for subsistence. The fishery survey was conducted during monsoon (August 2007), winter (December 2007) and summer (April 2008) using cast net. 50 castings each in the upstream and downstream of the dam site were done in different sections of the river. The major fish species observed during fisheries survey conducted by WAPCOS Limited is given in Table The major fish species observed during fisheries survey conducted by RS Envirolink Technologies Pvt. Ltd. is given in Table TABLE-6.44 List of fish species in project area along with their common names S. No. Species Family 1 Barilius barna Cyprinidae 2 Botia Dario Balitoridae 3 Chanda nama Ambassidae 4 Channa orientalis Channidae 5 Danio aequipinnatus Cyprinidae 6 Garra gotyla gotyla Cyprinidae 7 Garra lissorhynchus Cyprinidae 8 Glyptothorax sp. Amblycipitidae 9 Hara hara Amblycipitidae WAPCOS Limited 6-66

175 S. No. Species Family 10 Labeo dero Cyprinidae 11 Labeo pangusia Cyprinidae 12 Puntius sarana sarana Cyprinidae 13 Salmostoma bacaila Cyprinidae 14 Schizothorax richardsonii Cyprinidae 15 Tor putitora Cyprinidae 16 Tor tor Cyprinidae Source: Field studies by WAPCOS Limited TABLE-6.45 List of Fish Species Occurring in Nyamjhang Chhu Sl. No. Species Family 1 Euchiloglanis hodgarti Sisoridae 2 Euchiloglanis kamengensis Sisoridae 3 Exostoma labiatum Sisoridae 4 Glyptothorax coheni Amblycipitidae 5 Glyptothorax conirostris Amblycipitidae 6 Glyptothorax pectinopterus Amblycipitidae 7 Labeo dero Cyprinidae 8 Labeo dysocheilus Cyprinidae 9 Nilossocheilus hexagonolepis Siluridae 10 Noemacheilus rupecola repecola Cyprinidae 11 Noemacheilus sikimaiensis Cyprinidae 12 Pseudocheneis sulcatus Labridae 13 Schizopyge stolizckae Cyprinidae 14 Schizothoraichthys esocinus Cyprinidae 15 Schizothoraichthys progastus Cyprinidae 16 Schizothorax richardsonii Cyprinidae Source: Field studies by RS Envirolink Technologies Pvt. Ltd Snow trout, a migratory fish species represented by Schizothorax sp. are endemic to Himalayas. In winter months, when the water in upper reaches of these rivers touches almost 0 o C, snow trouts migrate downstream for a considerable distance and constitute the major fisheries, particularly in the middle and lower stretches. Mahaseer in the area is represented by Tor species, which is one of the finest group of game fish of lower Himalayas. During months of May and June, they migrate upward and ascend to the smaller tributaries for breeding. WAPCOS Limited 6-67

176 The proposed barrage may obstruct the migration route of the Mahaseer and Snow trout which can be termed as one of the adverse impacts. The Mahaseer species undertake upstream migration in river Nyamjangchhu during summer and monsoon months for feeding and breeding. As the winter sets in the upper reaches, the species takes a downstream journey. WAPCOS Limited 6-68

177 CHAPTER 7 BASELINE SETTING FOR SOCIO-ECONOMIC ASPECTS 7.1 GENERAL Most often, development projects are planned based on the availability of exploitable natural resources. Upon commissioning these act on growth foci. This attracts flow of finances, investments, jobs and other livelihood opportunities, which brings in people from different cultural and social background. Such planned activities not only provide impetus to the local economy but also bring about a multi-dimensional economic, social and cultural change. Most often it has been observed that such development projects are commissioned in economically and socially backward areas, which are inhabited by some of the indigenous populations. Commissioning of development project invariably brings about a number of desired and undesired impacts along with it. The baseline status has been divided into following three categories: Physico-chemical aspects Ecological aspects Socio-Economic aspects. As part of the comprehensive EIA study, a comprehensive assessment of socioeconomic aspects was undertaken. The objective of this study was to ascertain the overall socio-economic conditions prevailing in the study area, as well as among the project affected families. Further, impacts, both positive as well as negative, that are likely to occur during the construction and operation phase of the proposed project on the socio-economic aspects of the environment have also been assessed, which has been described in Chapter 8 of this report. A Resettlement and Rehabilitation (R&R) plan has been devised for the Project Affected Families (PAFs) who are likely to lose land, homestead or both due to land acquisition for various project appurtenances as a part of the present studies. The same has been outlined in Chapter 13 of the Environmental Management Plan (EMP) report, which is a separate volume of this report. The baseline setting for socio-economic aspects are outlined in the present Chapter. 7.2 DEMOGRAPHIC PROFILE OF ARUNACHAL PRADESH The demographic profile of Arunachal Pradesh is summarized in Table-7.1. WAPCOS Limited 7-1

178 TABLE-7.1 Demographic profile of Arunachal Pradesh Parameter Value Population Male 573, 951 Female 517, 166 Total 1, 091, 117 No. of females/1000 males 901 Density of population (Nos./km2) 13 Scheduled Caste (SC) population Total 6000 Percentage of SC population to total population 0.55 Scheduled Tribe (ST) population Total Percentage of ST population to total population 65 Literacy Literate Persons 487, 796 Total Literacy rate (%) Female Literacy rate (%) 43.5 The total population and area of state Arunachal Pradesh are 1,091,117 and 83,743 km 2 respectively. The population density of the district is 13 people per sq. km. The number of females/1000 males in the study area is 901. The Scheduled Caste (SC) population is only 0.55%, while the Scheduled Tribe (ST) population is 65%. The number of total literate person is 487, 796.The overall literacy rate is average (54.74%) while the female literacy rate is 43.5%. 7.3 DEMOGRAPHIC PROFILE OF TAWANG DISTRICT The demographic profile of Tawang District is summarized in Table-7.2. TABLE-7.2 Demographic profile of Tawang District Parameter Value Population Male Female Total No. of females/1000 males 782 Density of population (Nos./km2) 18 Literacy Total Literacy rate (%) 47.3 Male Female 4177 WAPCOS Limited 7-2

179 The total population of district Tawang is Total male and female population is and respectively. The population density of the district is 18 people per sq. km. The number of females/1000 males in the study area is 782. The overall literacy rate is average (54.74%). Male literacy rate is 51.08% while the female literacy rate is quite low (24.45%). 7.4 DEMOGRAPHIC PROFILE OF THE STUDY AREA There are 60 villages belonging to five circles falling within the study area of proposed Nyamjang Chhu H.E. Project. The total human population of these villages is 11,445 of which 10,515 belong to Schedule Tribes which constitutes 91.8 % of the total population. There are 2,693 household in study area with Lumla circle having the highest number (1,216) followed by Zemithang (647), Dudunghar (519), Mukto (195) and Tawang (116). The demographic profile of villages in study area is given in the Table-7.3. TABLE-7.3 Demographic Profile of Study Area Villages Circle Village Name Households Population Sex ratio Male Female Total Socktsen Lumpo Muchut (Kharakpu) Ghorsham ZEMITHANG Zemithang H.Q Kharman Khelengteng Dung Khobleteng Thiksi Sirdi Shakti Gyangong Ani Gompa TAWANG Tawang Gompa Gompa Village(Basti) Lumla H.Q Lumla Village (Soleng) WAPCOS Limited 7-3

180 Circle Village Name Households Population Sex ratio Khozo (Melenghar) (Tabrang) (Mayur) Mangnam Thrillam Buikung Hoongla Pharmey LUMLA Khumithang Dugumba Suhung(Jung) Sazo Kungba Kharteng Phomang Baghar Sherbang Yabab Gispu MUKTO Bongleng Kharung Buri Shorkimeng Bletting Lumsang Dongmareng Marmey User Guntse Zemining Dormeleng Loudung DUDUNGHAR Chelengdung Ramyang Dudunghar H.Q WAPCOS Limited 7-4

181 Circle Village Name Households Population Sex ratio Pamdung Maling Sanghar Namtsering Narmaleng Dungser Phomghar Khokem Surbin Muktur Educational Profile There are 25 primary schools, 7 middle schools and 2 secondary schools in the study area. There is no senior secondary school or college in the entire study area. Moreover, there is not even a single college in the entire district. Poor educational infrastructure is reflected in the literacy status in the area. Average literacy rate in the study area is 22.8%; village wise rate varies from 0 to 100% and there are two villages (Shorkimeng and Narmaleng) in dudunghar Circle, one village (Thiksi) in Zemithang Circle with entire illiterate population. Gyangong Ani in Tawang circle has highest literacy rate of 100%. Male literacy rate is fairly high as compared to that of female literacy rate. The details of educational profile is given in the Table-7.4. TABLE-7.4 Number of Educational institutions in the study area Circle Primary School Middle School Senior School ZEMITHANG TAWANG LUMLA MUKTO DUDUNGHAR TOTAL Health Care Facilities Health infrastructure is also very few in numbers in the study area. Local people are forced to travel long distances for their basic medical needs. A large number WAPCOS Limited 7-5

182 of people have been reported to be suffering from Cold, Malaria, Diarrhoea etc. Out of the 60 villages in the study area only three villages viz. Lumla H.Q,Lumla Villages and Bongleng have Primary Health Centers (PHC) and 12 Child Welfare Centers (CWC) in the study area (Refer Table-7.5) The existing PHCs were observed to be in bad shape and require urgent attention. Name TABLE-7.5 Number of hospitals and health care centers in the study area Allopathic Ayurvedic Homeopathic PHC PHSC CWC hospitals hospitals hospitals ZEMITHANG CIRCLE Socktsen Lumpo Muchut(Kharakpu) Ghorsham Zemithang H.Q Kharman Khelengteng Dung Khobleteng Thiksi Sirdi Shakti TAWANG CIRCLE Gyangong Ani Gompa Tawang Gompa Gompa Village (Basti) LUMLA CIRCLE Lumla H.Q Lumla Village (Soleng) Khozo (Melenghar) (Tabrang) (Mayur) Mangnam Thrillam Buikung Hoongla Pharmey Khumithang Dugumba Suhung(Jung) Sazo WAPCOS Limited 7-6

183 Name Allopathic hospitals Ayurvedic hospitals Homeopathic hospitals PHC PHSC CWC Kungba Kharteng Phomang Baghar Sherbang Yabab Gispu MUKTO CIRCLE Bongleng Kharung DUDUNGHAR CIRCLE Buri Shorkimeng Bletting Lumsang Dongmareng Marmey User Guntse Zemining Dormeleng Loudung Chelengdung Ramyang Dudunghar H.Q Pamdung Maling Sanghar Namtsering Narmaleng Dungser Phomghar Khokem Surbin Muktur TOTAL Note: PHC= Primary Health Centre, PHSC=Primary Health Sub Centre CWC=Child Welfare Centre Occupational Profile Distribution of the working population among the five circles in the study area show that Lumla has the highest percentage of working population, whereas Seppa and Pipu has the lowest percentage of working population. WAPCOS Limited 7-7

184 Occupational status of the main, marginal and non workers of the vicinity villages in the project area show that there is nearly an equal distribution of the males and females workers in the marginal worker population. However, 56% of the male population and 44% of the female population constitutes the total population of main workers. 53%t of the female population and 47 percent of the male population constitutes the total non workers population Other Amenities The current status of transport in the villages is highly unsatisfactory. Among the total 60 villages, only 12 have bus service, only 2 villages have the postal and banking facility. 7.5 SOCIO-ECONOMIC SURVEY FOR PROJECT AFFECTED FAMILIES The socio-economic assessment has also been carried-out in those villages where land is proposed to be acquired for the proposed Nyanjangchhu hydroelectric project. Most of the information required to assess the socio-economic profile and property enumeration for preparation of Resettlement and Rehabilitation Master Plan was collected with the help of a detailed quantitative 100% survey of the PAFs in the affected villages. The information on the following socio-economic parameters was collected: Transhumance Demographic profile Educational levels Occupational Profile Land holding pattern Cropping pattern Assets owned Livestock and other socio-economic parameters etc. Based on our preliminary field investigations, and through literature review, a household level survey schedule was devised, to capture the overall socioeconomic status of the PAFs. The survey schedule was formulated as a series of prompts, rather than a structured questionnaire, to allow the investigators to phrase queries according to the circumstance during interpersonal interviews with PAFs. This survey schedule was pre-tested in the field, prior to start of the socio-economic survey. For the process of primary data collection, a survey team comprising of local investigators was put together. Members of the survey team (investigators/ WAPCOS Limited 7-8

185 surveyors) were local educated youths. Training was imparted to the members of the survey team, wherein they are appraised about the purpose of the survey and on the method of interaction with the PAFs and to elicit required information and how to filled-in the survey schedules. The survey team traversed the entire project area, including submergence area, barrage alignment and sites of other project appurtenances in each of the project affected villages. The survey team visited 3 villages in which private land is proposed to be acquired, namely, Khaleteng, Kharteng and Soksen. As per our assessment, based on ROR, about 47 project affected persons are expected to lose land (agricultural/nonagricultural/homestead) in varying proportion. This list was verified during the survey work, and by the end of the work, the survey team had covered all the 47 project affected families. The survey team coordinator scrutinized the filled-in survey schedules for internal discrepancies and missing information; which were eliminated in the field, in some cases by either going back to the concerned families, before it was coded for computerization. The filled-in survey schedules were scrutinized at WAPCOS headquarters (Delhi) as well, before they were coded and computerized using database computer software. The raw data was then compiled and systematized before it was analyzed for various socio-economic parameters. Data analysis was undertaken using Statistical Package for Social Sciences (SPSS) computer software. The analyzed outputs have been used in reporting the findings of the socio-economic survey. The state of Arunachal Pradesh has its own state-level resettlement and rehabilitation policy/guidelines. As per Notification No LM 20/2005 dated 20 th Sep has adopted the State Rehabilitation and Resettlement Policy, 2008 for Project Affected Families in the state of Arunachal Pradesh. The National Policy on Resettlement and Rehabilitation for Project Affected Families 2007 (NRRP 2007) has also been used to prepare the resettlement and rehabilitation plan for the PAFs of Nyamjangchhu hydro-electric project. 7.6 SOCIO-ECONOMIC PROFILE OF THE PROJECT AFFECTED FAMILIES Commissioning of development projects invariably brings about a number of desired and undesired impacts along with it. Most often, development projects are planned based on the availability of exploitable natural resources. Upon WAPCOS Limited 7-9

186 commissioning, these areas act as growth foci. This attracts flow of finances, investments, job and other livelihood opportunities, which brings in people from different cultural and social backgrounds. Such planned activities not only provide impetus to the local economy but also bring about a multi-dimensional social and cultural change in the once dormant area. Most often it has been observed, such development projects are commissioned in economically and socially backward areas, which are inhabited by some of the most indigenous populations. The Nyamjangchhu hydro-electric project is located in one of the backward regions of Arunachal Pradesh, which thrives on the tourism industry. A detailed socio-economic study was undertaken in mid-june The study was taken up to understand the overall social and economic status of the project affected families (PAFs) of this project, their life-style and to assess the likely impacts of the project in terms of loss of personal and community property of the PAFs. This Chapter outlines the overall socio-economic status of the PAFs residing in the project area. A total of 5 hamlets/villages are likely to get affected as a result of land acquisition due to the proposed project. All these villages are located in district Tawang. The list of project affected villages, affected due to the process of land acquisition is outlined in Table 7.6. TABLE 7.6 Project affected hamlets/villages due to the process of land acquisition S. Name of Project No. Affected hamlets/ villages 1 Khaleteng 2 Kharteng 3 Soksen Demographic Profile of Affected Population The detailed description of the socio-economic profile is highlighted in the following sub-sections, which gives an overall summary of the socio-economic conditions of the affected population residing in the project study area. Census survey covering 100% of the PAFs were conducted in the 3 project affected villages/hamlets that reckoned about 47 families. Amongst these 47 families, a total population of 209 persons was covered. WAPCOS Limited 7-10

187 (A) Religious Affiliation The religious affiliation amongst the project affected families is Buddhism. During survey, it was observed that the entire population within the project area is primarily Buddhist. (B) Caste distribution of PAFs The caste-wise distribution of population is outlined in Table 7.7. Out of the total 47 project-affected families, 100% belong to the Schedule Tribe category, belonging Morpa and Mompa Sub-Castes, among this Morpa is the dominant sub-caste category which constitute about 60% of ST among the project affected families. There is No Scheduled Castes (SC), General Caste (GC) and Other Backward Caste (OBC) population are observed among the PAFs. TABLE 7.7 Village-wise Distribution of PAFs on the basis of Caste and Religion Caste Khaleteng Kharteng Soksen Total General OBC SC ST Sub-caste Morpa Mompa Other Religion Christian Hindu Muslim Buddhist Source: Primary Survey, June 2009 Legend: GC = General Caste OBC = Other Backward Caste SC = Schedule Caste ST = Schedule Tribe (C) Population Characteristics The demographic profile of the affected villages is given in Table-7.8. As per WAPCOS survey, the total affected population is of the order of 209 persons. Out of this population, males and females constitute about 52% and 48% of the total affected population. The population below the age of 18 years (or Child WAPCOS Limited 7-11

188 population) accounted for about 38.2% of the total population. The average family size is about 4 persons per family. The average sex ratio, i.e. the number of females per 1000 males amongst the project affected population is about S. No. Village Name TABLE 7.8 Village-wise distribution of PAPs Total Male Female Population Population Population Population < 18 yrs WAPCOS Limited 7-12 Sex Ratio Average Family Size 1. Khaleteng Kharteng Soksen Total Source: Primary Survey, June Educational profile The educational profile among the surveyed population as collected through the primary survey is given in Table-7.9. As per the socio-economic survey, about 70.8% of the project-affected population is illiterate/not going to school. The remaining population (29.2%) is either literate or is presently continuing with their education. Amongst the surveyed population, persons educated upto or pursuing the primary school level is about 13.9% of the total surveyed population. The percentage of population educated or undergoing their education in middle school and high school is of the order of 5.7% and 6.2% respectively. About 0.95% each of the total population is educated or pursuing education in the senior secondary level and graduation level respectively. TABLE -7.9 Educational Profile of the PAPs Particulars Khaleteng Kharteng Soksen Total Illiterate Primary Middle Secondary Senior Secondary Graduation Post-graduate Others Total Source: Primary Survey, June 2009

189 7.6.3 Occupational profile The occupational profile of the affected population is shown in Table As per our survey, it is observed that out of the total of 209 persons, about 61.24% are gainfully engaged in an economic activity. This group consists of persons engaged in Agriculture, Labour, agricultural labour, service and business, which constitute about 26.5%, 25.7%, 42.9%, and 4.68% respectively of the total surveyed population. TABLE-7.10 Occupational profile of PAPs Occupation Khaleteng Kharteng Soksen Total Agriculture Labour Agri. Labour Service Business Total Source: Primary Survey, June Livestock holding pattern During the survey, it was observed that almost all the affected families reared domesticated animals for milk, meat, eggs and labor. The details of livestock holding pattern are shown in Table Amongst the livestock, cows are the most commonly observed; 81% of total livestock heads are cows. Cows are mainly reared for their milk. It was observed that bulls are used extensively for ploughing the agricultural fields, which is also evident from the statistics as well. It is also clear that few families own buffaloes as well. Goats and sheep are also reared by some of the project affected families. TABLE Livestock Holding Pattern of the PAFs Livestock Mithuns cows Bulls Calves Goats Poultry Pigs Khaleteng Kharteng Soksen Total Source: Primary Survey, June 2009 WAPCOS Limited 7-13

190 7.6.5 Housing Information regarding Housing details was also collected from the affected families during the socio-economic survey. It was found that no family was houseless. Mixed layout of housing was observed in the project affected villages. The settlement layout as observed during the survey ranged from dispersed to compact settlements. Also linear settlement (on either sides of a village lane) was also observed in some of the project affected villages. The residential unit served the purpose of housing one or many families (off-spring), including their cattle, fuel wood, and other material possessions of these families. It was observed during socio-economic survey that 93.6% of the PAFs houses were own house and rest were rented house. It was also observed that out of 47 houses 41 were electrified. It was observed that most of the houses were single storey, and some houses had more than one floor. Further, it was observed that the houses on an average had about 1 to 2 rooms. Wood and Stone were used to build the walls of the houses, while the roof was mostly made of bamboo and tin. It was observed that most of the houses had a defined space for housing cattle, with about one room for housing cattle on an average. A small percentage of the houses had provision for separate bathroom and toilet facilities. Otherwise, it was observed that most of the residents either made use of the rivulets and streams for washing and cleaning purposes. For sanitation purposes, drains and other means of water outlets were absent in most of the villages. The details of housing pattern of PAFs are described in Table TABLE-7.12 Details of Housing Pattern of the PAFs Housing Details Khaleteng Kharteng Soksen Total Owned Rented Floors( No. of families) Ist nd rd Av. No of rooms No of Houses have electric connection No. of houses have cattel shed WAPCOS Limited 7-14

191 No. of house have the store room No. of house have the lavatory Other(No of shops) Wall Material used(no. of families) Wood & Stone Stone Semi Kuchcha & wood Kuchcha Stone & Bamboo Mud Material Used for Roof(No. of families) Tin Bamboo Wood Tin & Wood Source: Primary Survey, June Sources of Water Information on sources of water for different uses by the villagers was also collected. It was observed that river/streams are used primarily to meet the water requirement for meeting drinking, washing and cleaning requirements. It was observed that PAFs made use of pipe and tap which is connected to a system of pipe network connected to taps which were either locally assembled or provided by the government. It includes a storage tanks near a source and connected through a network of pipelines, which is subsequently connected to tap dispensers Material Assets Holding Pattern Information on various material assets owned by the surveyed population was also collected. The details of material assets and other assets are given in Table It is clear that many PAFs, if not all, own some material assets. These assets include television sets, tape recorders, transistor radio, LPG cylinder, refrigerators, bicycle, motor cycles, four wheelers, etc. WAPCOS Limited 7-15

192 TABLE-7.13 Possession of material assets owned by PAFs Material Assets Khaleteng Kharteng Soksen Total TV sets Tape-recorders Transistor Radios Modern Furniture Refrigerators Cycles wheelers wheelers LPG Cylinders Source: Primary Survey June Land profile, Agriculture and crops As a part of the survey, information regarding agricultural land has been collected. It was observed that most of the affected families have their own agricultural land and the type of cultivation observed is Sedentary. Natural sources are the main source of irrigation in the surveyed population. They use Organic manure for the purpose of fertilizer, which is easily available and a good fertilizer also. Wheat, millet, Maize and kodo are the main crops grown in the area. As a part of the survey, information regarding number of fruit bearing and commercial trees owned by the project affected families was also collected. The village-wise details of agricultural land, irrigation facility, crops and trees owned by all the affected families are given in Table TABLE-7.14 Village-wise details of ownership of land, crops, trees Particular Khaleteng Kharteng Soksen Total Agriculture Own land Method of cultivation Sedentary Jhumming Both Operation 0 Self Share basis Own land Other's land Irrigation Facility 0 WAPCOS Limited 7-16

193 Particular Khaleteng Kharteng Soksen Total Natural Sources Rivers/Streams Rain Natural Sources, River stream &Rain Natural & Rain Fertilizer use 0 Chemical Fertilizer Organic manure Both Crops Taken( No. of family) Millet Maize Wheat Kodo Paddy Phapoar Maduwa Furva Chilli Potato Name of the trees(nos.) 0 Mango Apricot Orange Guava Pine Bamboo Palm Apple Source: Primary Survey, June Awareness about Project As a part of the field studies, the information on awareness among the PAFs about the proposed project was also collected. It was observed that more than 75% of the PAFs were aware about the proposed Nyamjangchhu hydro-electric power project and only 11% of the PAFs were aware about the displacement of the project. About 80% of the PAFs are interested in cash compensation and about 75% of people are interested in jobs as compensation. WAPCOS Limited 7-17

194 8.1 GENERAL CHAPTER-8 PREDICTION OF IMPACTS Based on the project details and the baseline environmental status, potential impacts as a result of the construction and operation of the proposed Nyamjangchhu hydroelectric project have been identified. This Chapter addresses the basic concepts and methodological approach for conducting a scientifically based analysis of the potential impacts likely to accrue as a result of the proposed project. The Environmental Impact Assessment (EIA) for quite a few disciplines is subjective in nature and cannot be quantified. Wherever possible, the impacts have been quantified and otherwise, qualitative assessment has been undertaken. This Chapter deals with the anticipated positive as well as negative impacts due to construction and operation of the proposed project. The construction and operation phase comprises of various activities each of which is likely to have an impact on environment. Thus, it is important to understand and analyze each activity so as to assess its impact on environment. The key activities have been categorized for construction and operation phases. Construction Phase Activities Site preparation Earthwork and excavation including controlled blasting and drilling Construction of a diversion barrage Undersluice, head regulator, feeder channel, desilting arrangement HRT of km length with an underground surge shaft Underground power house to generate (6x130) 780 MW of power Tail Race Tunnel of 7.0 m diameter and 1965 m length to discharge flow into river Nyamjangchhu Construction of new roads and upgradation of existing roads Construction of a temporary bridge over river Nyamjangchhu Project headquarter, offices and colonies Disposal of muck and construction wastes Transportation of construction material Operation and maintenance of construction equipment Civil and mechanical fabrication works for construction of various project components. Operation of DG sets Disposal of pollutants from workshops, etc. Disposal of effluents and solid waste from labour camps and colonies WAPCOS Limited 8-1

195 Operation Phase Activities Diversion of water from river Nyamjangchhu for hydropower generation Equipment maintenance and equipment restoration Sewage and solid waste generation from project colonies The various project activities and associated potential environmental impacts on various environmental parameters have been identified and summarized in a matrix and the same is outlined in Table-8.1. WAPCOS Limited 8-2

196 S. No. TABLE-8.1 Matrix for various project activities and associated potential Environmental Impact on various Environmental Parameters Project Activities Soil Geol Hydrol Air Nois Employm & ogy ogy quali e ent Land ty Wate r quali ty Flora / Faun a A. Construction Phase 1. Sire preparation including tree cutting 2. Earthwork and excavation including blasting and drilling 3. Construction of Diversion barrage across river Nyamjangchhu 4. Construction of head race tunnel 5. Construction of underground surge shaft 6. Construction of underground power house 7. Widening of approach roads 8. Disposal of muck and construction wastes 9. Transportation of construction materials 10. Operation and maintenance of construction equipment 11. Disposal of sewage and solid waste from labour camps 12. Acquisition of private land Socio - cultu re WAPCOS Limited 8-3

197 S. No. Project Activities Soil & Land Geol ogy Hydrol ogy Wate r quali ty Air quali ty Nois e Flora / Faun a Employm ent 13. Acquisition of forest land 14. Acquisition of labour population B. Operation Phase Activities 1. Diversion of water for hydropower generation 2. Equipment maintenance 3. Disposal of sewage and solid waste from project colony 4. Mushrooming of allied activities Socio - cultu re WAPCOS Limited 8-4

198 The impacts which have been covered in the present Chapter are categorized as below: - Impacts on Water Environment - Impacts on Air Environment - Impacts on Noise Environment - Impacts on Land Environment - Impacts on Biological Environment - Impacts on Socio-Economic Environment 8.2 IMPACTS ON WATER ENVIRONMENT The various aspects covered under water environment are: - Water quality - Sediments - Water resources and downstream users Water quality a) Construction phase The major sources of surface water pollution during project construction phase are as follows: Sewage from labour camps/colonies Effluent from crushers Pollution due to muck disposal Effluents from other sources i) Sewage from labour camps The project construction is likely to last for a period of 6 years (74 months). The peak labour strength likely to be employed during project construction phase is about 3000 workers and 500 technical staff. The employment opportunities in the area are limited. Thus, during the project construction phase, some of the locals may get employment. It has been observed during construction phase of many of the projects; the major works are contracted out, who bring their own skilled labour. However, it is only in the unskilled category, that locals get employment. The construction phase, also leads to mushrooming of various allied activities to meet the demands of the immigrant labour population in the project area. WAPCOS Limited 8-5

199 The following assumptions have been made for assessing the emigrating population in the area: 80% of workers and technical staff emigrating into the area are married. In 80% of the family of workers both the husband and wife will work. In 100% of the family of technical staff, only husband will work. 2% of total migrating population has been assumed as service providers. 50% of service providers will have families. Family size has been assumed as 5. Based on experience of similar projects and above referred assumptions, the increase in the population as a result of migration of labour population during construction phase is expected to be of the order of The domestic water requirement has been estimated as 70 lpcd. Thus, total water requirements work out to 0.78 mld. It is assumed that about 80% of the water supplied will be generated as sewage. Thus, total quantum of sewage generated is expected to be of the order of 0.63 mld. The BOD load contributed by domestic sources will be about 504 kg/day. It is assumed that the sewage is discharged without any treatment for which, the minimum flow required for dilution of sewage is about 2.2 cumec. Detailed DO modelling was done using Streeter Phelp s model. The D.O. level was estimated using the following equation: K 1 L A [10 -K1t 10 -K2t ] D t = D A 10 -K2t K 2 K 1 D t = D.O. deficit downstream at time t. K 1 = Deoxygenation rate K 2 = Reaeration rate L A = Ultimate upstream BOD D A = D.O. deficit upstream t = Time of stream flow upstream to point at which D.O. level is to be estimated The D.O. level in the river Nyamjangchhu was taken as 8.0 mg/l. The minimum flow in the river Nyamjangchhu was taken as 12.3 cumec (minimum flow estimated for 90% dependable year in the month of January-from Table-4.8). The results of D.O. model are summarized in Table-8.2. WAPCOS Limited 8-6

200 TABLE-8.2 Results of D.O. Modelling due to disposal of sewage from labour camps in river Nyamjangchhu Distance from outfall (km) D.O. (mg/l) It can be observed from Table-8.2, that no impact is anticipated on river water quality, as a result of disposal of sewage from labour camps. Even though no impact is envisaged on water quality of river Nyamjangchhu, as a result of disposal of untreated sewage, it is recommended to commission units for treatment of sewage generated from labour camps. In the proposed project, sewage is proposed to be treated, prior to disposal. ii) Effluent from crushers During construction phase, at least one crusher will be commissioned at the quarry site by the contractor involved in construction activities. It is proposed only crushed material would be brought at construction site. The total capacities of the two crushers are likely to be of the order of tph. Water is required to wash the boulders and to lower the temperature of the crushing edge. About 0.1 m 3 of water is required per ton of material crushed. The effluent from the crusher would contain high-suspended solids. About m 3 /hr of wastewater is expected to be generated from each crusher. The effluent, if disposed without treatment can lead to marginal increase in the turbidity levels in the receiving water bodies. The natural slope in the area is such that, the effluent from the crushers will ultimately find its way in river Nyamjangchhu. This amounts to a discharge of to cumec. Even the lowest 10 day minimum flow in river Nyamjangchhu is 12.3 cumec. The effluent from crusher will have suspended solids level of mg/l. On the other hand, suspended solids as observed at various sampling locations, during water quality monitoring studies was observed to be <0.1 mg/l. The composite value of suspended solids would increase by 0.05 mg/l, which is insignificant. Thus, no adverse impacts are anticipated due to small quantity of effluent and large WAPCOS Limited 8-7

201 volume of water available in river Nyamjangchhu for dilution. Even then, it is proposed to treat the effluent from crushers in settling tank before disposal so as to ameliorate even the marginal impacts likely to accrue on this account. iii) Pollution due to muck disposal The major impact on the water quality arises when the muck is disposed along the river bank. The project authorities have identified suitable muck disposal sites which are located near the river channel. The muck will essentially come from the road-building activity, tunneling and other excavation works. The unsorted waste going into the river channel will greatly contribute to the turbidity of water continuously for long time periods. The high turbidity is known to reduce the photosynthetic efficiency of primary producers in the river and as a result, the biological productivity will be greatly reduced. Therefore, the prolonged turbid conditions would have negative impact on the aquatic life. Therefore, muck disposal has to be done in line with the Muck Disposal Plan given in EMP to avoid any negative impact. iv) Effluent from other sources Substantial quantities of water would be used in the construction activities. With regard to water quality, waste water from construction activities and runoff from construction site would mostly contain suspended impurities. Adequate care should be taken so that excess suspended solids in the wastewater are removed before discharge into water body. The effluent is proposed to be treated by collecting the waste water and runoff from construction sites and treating the same in settling tanks. b) Operation phase The major sources of water pollution during project operation phase include: Effluent from project colony. Impacts on reservoir water quality. Eutrophication risks Sediments i) Effluent from project colony During project operation phase, due to absence of any large-scale construction activity, the cause and source of water pollution will be much different. Since, WAPCOS Limited 8-8

202 only a small number of O&M staff will reside in the area in a well-designed colony with sewage treatment plant and other infrastructure facilities, the problems of water pollution due to disposal of sewage are not anticipated. In the operation phase, about 100 families (total population of 500) will be residing in the project colony proposed to be developed at Lumla, Khartang and Zimithang. About 0.23 to 0.27 mld of sewage will be generated. The total BOD loading will be order of 68 to 81 kg/day. It is proposed to provide biological treatment facilities including secondary treatment units for sewage so generated from the BOD load after treatment will reduce to 10 to 12 kg/day. It shall be ensured that sewage from the project colony be treated in a sewage treatment plant so as to meet the disposal standards for effluent. Thus, with commissioning of facilities for sewage treatment, no impact on receiving water body is anticipated. Thus, no impacts are anticipated as a result of disposal of effluents from the project colony. ii) Impacts on reservoir water quality The flooding of previously forest and agricultural land in the submergence area will increase the availability of nutrients resulting from decomposition of vegetative matter. Phytoplankton productivity can supersaturate the euphotic zone with oxygen before contributing to the accommodation of organic matter in the sediments. Enrichment of impounded water with organic and inorganic nutrients will be the main water quality problem immediately on commencement of the operation. However, this phenomenon is likely to last for a short duration of few years from the filling up of the reservoir. In the proposed project, most of the land coming under reservoir submergence is barren, with few patches of trees. These trees too are likely to be cleared before filling up of the reservoir. The proposed project is envisaged as a runoff the river scheme, with significant diurnal variations in reservoir water level. In such a scenario, significant reaeration from natural atmosphere takes place, which maintains Dissolved Oxygen in the water body. Thus, in the proposed project, no significant reduction in D.O. level in reservoir water is anticipated. iii) Eutrophication risks Another significant impact observed in the reservoir is the problem of eutrophication, which occurs mainly due to the disposal of nutrient rich effluents WAPCOS Limited 8-9

203 from the agricultural fields. However, in the present case, fertilizer use in the project area is negligible, hence, the runoff at present does not contain significant amount of nutrients. Even in the post-project phase, use of fertilizers in the project catchment area is not expected to rise significantly. Another factor to be considered that the proposed project is envisaged as a run off the river scheme, with significant diurnal variations in reservoir water level. Thus, residence time would be of the order of few days, which is too small to cause any eutrophication. Thus, in project operation phase, problems of eutrophication, which is primarily caused by enrichment of nutrients in water, are not anticipated Sediments When a river flows along a steep gradient, it could carry a significant amount of sediment load, depending on the degradation status of the catchment. When a hydraulic structure is built across the river, it creates a reservoir, which tends to accumulate the sediment, as the suspended load settles down due to decrease in flow velocity. The proposed project is envisaged as a runoff the river scheme, with a barrage. At regular intervals, the gates of the barrage shall be opened to flush out the sediments. Thus, in the proposed project, sedimentation problems are not anticipated Water resources and downstream users The Nyamjangchhu Hydro Electric Project is a run of river scheme project on river Nyamjangchhu. The diversion of water for hydropower generation will lead to drying or reduction of flow river stretch of about 32 km. The effect will be more pronounced in the lean season. There are no major users of water in the intervening stretches, as river flows through a gorge and requires pumping for use at point of consumption. As a result, there are no major users of water of river Nymjangchhu in the intervening stretch. Thus, no major adverse impacts are anticipated on downstream water users. However, there will be significant adverse impacts on riverine ecology, which needs to be ameliorated through the release of minimum flow. WAPCOS Limited 8-10

204 8.2.4 Impacts on river bed stability During the construction phase a large quantity of construction material like stones, pebbles, gravel and sand would be needed. Significant amount of material is available in the river bed. It is proposed to extract construction material from borrow areas in the river bed. The extraction of construction material will lead to formation of pits. Normally, deposition of material takes place at sites where velocity reduces on account of flattening of slopes, increase in cross-sectional area. Such sites are used for extraction of construction material. The pits at sites after extraction of construction material will be under constant action on account of erosion in high flows and deposition under low flows. These pits with passage of time will be stabilized due to settlement of silt and sediments in the pits created on the river bed. Thus, no major impacts are anticipated o this account. 8.3 IMPACTS ON AIR ENVIRONMENT In a water resources project, air pollution occurs mainly during project construction phase. The major sources of air pollution during construction phase are: Pollution due to fuel combustion in various equipment Emission from various crushers Fugitive emissions from various sources. Blasting Operations Pollution due to increased vehicular movement Dust emission from muck disposal Pollution due to fuel combustion in various equipment The operation of various construction equipment requires combustion of fuel. Normally, diesel is used in such equipment. The major pollutant which gets emitted as a result of combustion of diesel is SO 2. The SPM emissions are minimal due to low ash content in diesel. The short-term increase in SO 2, even assuming that all the equipment are operating at a common point, is quite low, i.e. of the order of less than 1µg/m 3. Hence, no major impact is anticipated on this account on ambient air quality. Emissions from crushers The operation of the crusher during the construction phase is likely to generate fugitive emissions, which can move even up to 1 km in predominant wind direction. During construction phase, one crusher each is likely to be commissioned WAPCOS Limited 8-11

205 near proposed dam and proposed power house sites. During crushing operations, fugitive emissions comprising mainly the suspended particulate will be generated. Since, there are no major settlements close to the dam and power house, hence, no major adverse impacts on this account are anticipated. However, during the layout design, care should be taken to ensure that the labour camps, colonies, etc. are located on the leeward side and outside the impact zone (say about 2 km on the wind direction) of the crushers. Fugitive Emissions from various sources During construction phase, there will be increased vehicular movement. Lot of construction material like sand, fine aggregate are stored at various sites, during the project construction phase. Normally, due to blowing of winds, especially when the environment is dry, some of the stored material can get entrained in the atmosphere. However, such impacts are visible only in and around the storage sites. The impacts on this account are generally, insignificant in nature. Blasting Operations Blasting will result in vibration, which shall propagate through the rocks to various degrees and may cause loosening of rocks/boulders. The overall impact due to blasting operations will be restricted well below the surface and no major impacts are envisaged at the ground level. During tunneling operations, dust will be generated during blasting. ID blowers will be provided with dust handling system to capture and generated dust. The dust will settle on vegetation, in the predominant down wind direction. Appropriate control measures have been recommended to minimize the adverse impacts on this account. Pollution due to increased vehicular movement During construction phase, there will be increased vehicular movement for transportation of various construction materials to the project site. Similarly, these will be increased traffic movement on account of disposal of muck or construction waste at the dumping site. The maximum increase in vehicle is expected to 50 vehicles per hour. Large quantity of dust is likely to be entrained due to the movement of trucks and other heavy vehicles. Similarly, marginal increase in Hydrocarbons, SO 2 and NOx levels are anticipated for a short WAPCOS Limited 8-12

206 duration. Modelling studies for hydrocarbon emissions were conducted and the results are given in Table-8.3. TABLE-8.3 Increase in hydrocarbon concentration due to vehicular movement Distance (m) Increase in HC concentration (µg/m 3 ) The increase in vehicular density is not expected to significant. In addition, these ground level emissions do not travel for long distances. Thus, no major adverse impacts are anticipated on this account. Dust emission from muck disposal The loading and unloading of muck is one of the source of dust generation. Since, muck will be mainly in form of small rock pieces, stone, etc., with very little dust particles. Significant amount of dust is not expected to be generated on this account. Thus, adverse impacts due to dust generation during muck disposal are not expected. 8.4 IMPACTS ON NOISE ENVIRONMENT a) Construction phase In a water resource projects, the impacts on ambient noise levels are expected only during the project construction phase, due to earth moving machinery, etc. Likewise, noise due to quarrying, blasting, vehicular movement will have some adverse impacts on the ambient noise levels in the area. i) Impacts due to operation of construction equipment The noise level due to operation of various construction equipment is given in Table-8.4. WAPCOS Limited 8-13

207 TABLE-8.4 Noise level due to operation of various construction equipment Equipment Noise level db(a) Earth moving Compactors Loaders and Excavator Dumper Tractors Scrappers, graders Pavers Truck Material handling Concrete mixers Movable cranes Stationary Pumps Generators Compressors Others Vibrators Saws Under the worst-case scenario, considered for prediction of noise levels during construction phase, it has been assumed that all these equipment generate noise from a common point. The increase in noise levels due to operation of various construction equipment is given in Table-8.5. Distance (m) TABLE-8.5 Increase in noise levels due to operation of various construction equipment Ambient noise levels db(a) Increase in noise level due to construction activities db(a) Increased noise level due to construction activities db(a) Increase in ambient noise level due to construction activities db(a) WAPCOS Limited 8-14

208 It would be worthwhile to mention here that in absence of the data on actual location of various construction equipment, all the equipment have been assumed to operate at a common point. This assumption leads to over-estimation of the increase in noise levels. Also, it is a known fact that there is a reduction in noise level as the sound wave passes through a barrier. The transmission loss values for common construction materials are given in Table-8.6. TABLE-8.6 Transmission loss for common construction materials Material Thickness of construction Decrease in noise material (inches) level db(a) Light concrete Dense concrete 4 40 Concrete block Brick 4 33 Granite 4 40 Thus, the walls of various houses will attenuate at least 30 db(a) of noise. In addition there are attenuation due to the following factors. Air absorption Rain Atmospheric inhomogeneties. Vegetal cover Thus, no increase in noise levels is anticipated as a result of various activities, during the project construction phase. The noise generated due to blasting is not likely to have any effect on habitations. However, blasting can have adverse impact on wildlife, especially along the alignment of the tunnel portion. It would be worthwhile to mention that no major wildlife is observed in and around the project site. Hence, no significant impact is expected on this account. Impacts due to increased vehicular movement During construction phase, there will be significant increase in vehicular movement for transportation of construction material. At present, there is no vehicular movement near the barrage site. During construction phase, the increase in vehicular movement is expected to increase upto a maximum of 5 to 6 trucks/hour. WAPCOS Limited 8-15

209 As a part of EIA study, impact on noise level due to increased vehicular movement was studied using Federal Highway Administration model. The results of modelling are outlined in Table-8.7. Distance (m) TABLE-8.7 Increase in noise levels due to increased vehicular movement Ambient Increase in Noise levels Increase in noise level noise level due to ambient db(a) due to increased noise level increased vehicular due to vehicular movement movement db(a) db(a) increased vehicular movement db(a) As mentioned earlier, there will be significant attenuation due to various factors, e.g. absorption by construction material, air absorption, atmospheric inhomogeneties, and vegetal cover. Thus, no significant impact on this account is anticipated. appropriate measures have been suggested as a part of Environmental Management Plan (EMP) report to minimize impacts on wildlife. Impacts on labour The effect of high noise levels on the operating personnel, has to be considered as this may be particularly harmful. It is known that continuous exposures to high noise levels above 90 db(a) affects the hearing acuity of the workers/operators and hence, should be avoided. To prevent these effects, it has been recommended by Occupational Safety and Health Administration (OSHA) that the exposure period of affected persons be limited as per the maximum exposure period specified in Table-8.8. WAPCOS Limited 8-16

210 Maximum equivalent continuous Noise level db(a) TABLE-8.8 Maximum Exposure Periods specified by OSHA Unprotected exposure period per day for 8 hrs/day and 5 days/week ½ 115 ¼ 120 No exposure permitted at or above this level Noise generated due to drilling The noise levels monitored at a 10 m distance from the source and operator s cabin is given in Table-8.9. TABLE-8.9 Noise generated due to drilling Equipment Noise level at source db(a) Standing idle (inside cabin) Standing idle (10 m radius) On load (inside cabin) On load (10 m radius) The noise levels during various construction activities have been compared to various standards prescribed by Occupational Safety and Health Administration (OSHA), which are being implemented in our country through rules framed under Factories Act. It can be observed (Refer Table-8.8) that for an 8 hour duration, equivalent noise level exposure should be less than 90 db(a). The Director General of Mines Safety in its circular no. DG(Tech)/18 of 1975, has prescribed the noise level in mining operations for workers in 8 hour shift period with unprotected ear as 90 db(a) or less. Similar norms can be considered for construction phase of the proposed project as well. The workers who are expected to be exposed to noise levels greater than 90 db(a), should not work in these areas beyond 6 to 8 hours. In addition, they also need to be provided with ear plugs. Thus, increased noise levels due to drilling are not expected to adversely affect the workers operating the drill or involved in other mining activities closely. WAPCOS Limited 8-17

211 Noise generated due to blasting Noise generated by blasting is instantaneous, site specific and depends on type, quantity of explosives, dimension of drill hole, degree of compaction of explosives in the hole and rock. Noise levels generated due to blasting have been monitored at various sites and the results have been summarized in Table No. of holes TABLE-8.10 Noise generation due to blasting Maximum charge/delay (kg) Total charge (kg) Distance (m) Noise level db(a) It can be observed from Table-8.10, that noise level due to blasting operations are expected to be of the order of db(a). Since, the nearest settlement are about 0.8 to 1.0 km away, the incremental noise due to blasting is expected to be db(a). As the blasting is likely to last for 4 to 5 seconds depending on the charge, noise levels over this time would be instantaneous and short in duration. Considering attenuation due to various sources, even the instantaneous increase in noise level is not expected to 60 db(a). Hence, noise level due to blasting is not expected to cause any significant adverse impact. 8.5 IMPACTS ON LAND ENVIRONMENT a) Construction phase The major impacts anticipated on land environment during construction are as follows: Quarrying operations Operation of construction equipment Soil erosion Muck disposal Acquisition of land WAPCOS Limited 8-18

212 Quarrying operations The total quantities required for the construction of civil components of the Nyamjang Chhu HEP are as follows: Concrete and Shotcrete Volume : 8,75,000 m 3 Fine Aggregate : 2,75,000 m 3 Coarse Aggregate : 5,25,000 m 3 The above construction material shall be arranged from the identified quarry site near Gorsam and major portion from the excavated muck of the HRT between Zimithang and BTK. The quantities from the HRT excavated muck and quarry site is estimated to contribute about 10,00,000 m 3 and 5,00,000 m 3 (30% swelling factor) respectively for the requirement of coarse aggregate. Fine aggregate requirement shall be met locally from the river bed and crushed sand. The quantity of aggregate in the Gneissic terrain would be more than the required quantities and the test report also suggests the suitability of the same. River Bed Material for Aggregates For the construction purpose river bed materials shall be utilized and for that two locations are identified on the downstream of the barrage. One location is near to the Zimithang village where there is a natural blockade of river due to previous floods. There big sized boulders of gneiss of about 30-40m length are observed. These boulders can be used for the construction material. Another location is near to the BTK nala and it is also a natural blockade which is formed in past few years. The boulders are larger in the river bed and can be utilized for construction material. The rocks from the quarries were found to be suitable for the use as coarse aggregate and crushed sand in concrete for non-wearing and wearing surfaces. Sand quarries In the project area there are few locations from where sand of coarse and fine segments can be extracted. Tests have been done to assess the suitability of sand in the Zimithang area, BTK area & Namtsering area. All the locations are in the river banks and nearby. The quantity of the river borne sand is not sufficient for the construction of the project and thus to be collected or transported from other locations. WAPCOS Limited 8-19

213 Opening of the quarries will cause visual impacts because they remove a significant part of the hills. Other impacts will be the noise generated during aggregate acquisition through explosive and crushing, which could affect wildlife in the area, dust produced during the crushing operation to get the aggregates to the appropriate size and transport of the aggregates, and transport of materials. The quarrying operations are semi-mechanized in nature. Normally, in a hilly terrain like Arunachal Pradesh, quarrying is normally done by cutting a face of the hill. A permanent scar is likely to be left, once quarrying activities are over. With the passage of time, the rock from the exposed face of the quarry under the action of wind and other erosion forces, get slowly weathered and after some time, they become a potential source of landslide. Thus it is necessary to implement appropriate slope stabilization measures to prevent the possibility of soil erosion and landslides in the quarry sites. ii) Operation of construction equipment During construction phase, various types of equipment will be brought to the site. These include crushers, batching plant, drillers, earthmovers, rock bolters, etc. The siting of this construction equipment would require significant amount of space. Similarly, space will be required for storing of various other construction equipment. In addition, land will also be temporarily acquired, i.e. for the duration of project construction for storage of quarried material before crushing, crushed material, cement, rubble, etc. Efforts must be made for proper siting of these facilities. Various criteria for selection of these sites would be: Proximity to the site of use Sensitivity of forests in the nearby areas Proximity from habitations Proximity to drinking water source Efforts must be made to site the contractor s working space in such a way that the adverse impacts on environment are minimal, i.e. to locate the construction equipment, so that impacts on human and faunal population is minimal. WAPCOS Limited 8-20

214 iii) Soil erosion The runoff from the construction sites will have a natural tendency to flow towards river Nyamjangchhu or its tributaries. For some distance downstream of major construction sites, such as barrage, power house, etc. there is a possibility of increased sediment levels which will lead to reduction in light penetration, which in turn could reduces the photosynthetic activity to some extent of the aquatic plants as it depends directly on sunlight. This change is likely to have an adverse impact on the primary biological productivity of the affected stretch of river Nyamjangchhu. Since, river Nyamjangchhu has significant flow, hence, impacts on this account are not expected to be significant. However, runoff from construction sites, entering small streams would have significant adverse impact on their water quality. The runoff would increase the turbidity levels with corresponding adverse impacts on photosynthetic action and biological productivity. The impacts on these streams and rivulets thus, would be significant. Adequate measures need to be implemented as a part of EMP to ameliorate this adverse impact to the extent possible. iv) Muck disposal The total quantity of muck expected to be generated has been estimated to be of the order of Mm 3. The component wise detail of muck to be generated are given in Table Based on the geological nature of the rocks and engineering properties of the soil, a part of the muck can be used as construction material. However, the balance requires being suitably disposed. Normally, muck is disposed in low-lying areas or depressions. In the proposed project 0.4 Mm 3 muck is proposed to be disposed at different sites. S. No. TABLE-8.11 Component wise details of muck to be generated Name of Component Qty. 1 River Diversions works WAPCOS Limited 8-21 Of Muck (excavated) (m³) Open Excavation Underground Excavation Total 25,000 25,000 2 Diversion Barrage 407, ,350 Intake,Sedimentation 3 chambers & flushing conduits 650, ,900

215 S. No. Name of Component Qty. 4 HRT & Construction Adits Of Muck (excavated) (m³) Open Excavation Underground Excavation Total 116,433 1,470,101 1,586,534 5 Surge Shaft 2,000 40,635 42,635 Pressure Shaft & Valve 6 Chamber 106, ,267 7 Power House Complex 8 TRT & outfall works 37, , ,806 9, , ,422 9 Road 546, , ,450 Total 1,794,836 2,245,528 4,040,364 As per the existing proposal for the construction of Nyamjangchhu hydroelectric project about 4.04 Mm 3 of muck is to be generated. The total quantity of muck to be generated considering 40% swelling factor is 5.66 Mm 3. It is proposed that Mm 3 of muck shall be utilized for backfilling. The quantity of material to be used in construction or protection works 1.05 Mm³. Hence the balance quantity of muck to be disposed off shall be about 3.91Mm 3. The muck shall be disposed at designated sites. The details are given in Table S. No. 1 TABLE-8.12 Details of muck utilization and disposal Qty. Of Qty. to be muck debris Qty. to used in generated be used Name of construction considering as Component or 40% as backfill protection swelling (m³) works (m³) factor (m³) River Diversions Qty. of Muck for disposal (m³) works 35,000 35, , , ,840 2 Diversion Barrage 3 Intake, Sedimentatio n chambers & flushing conduits 911,260 57, ,060 WAPCOS Limited 8-22

216 S. No. 4 Name of Component Qty. Of muck debris generated considering 40% as swelling factor (m³) Qty. to be used as backfill (m³) Qty. to be used in construction or protection works (m³) Qty. of Muck for disposal (m³) HRT & Construction Adits 2,221, , ,960 1,475,188 5 Surge Shaft 59,689-17,907 41,782 6 Pressure Shaft & Valve Chamber 148,732-44, ,113 7 Power House Complex 443, , ,470 8 TRT & outfall works 174,191-52, ,934 9 Road Total 1,093, , ,135 5,656, ,650 1,051,717 3,903,521 Normally, muck is disposed in low-lying areas or depressions. Trees, if any, are cut before muck disposal, however, shrubs, grass or other types of undergrowth in the muck disposal at sites perish. The total area earmarked for muck disposal is ha. The details are given in Table Component TABLE-8.13 Details of muck disposal site Village Land Classification Private Land (ha) Community Land (ha) Total Land (ha ) Muck disposal Site M-1 Muchat Muck disposal Site M-2 Kyaleyteng Muck disposal Site M-3 Shakti Muck disposal Site M-4 Shakti 0 (BTK) Muck disposal Site M-5 Shakti 0 (BTK) Muck disposal Site M-6 BTK WAPCOS Limited 8-23

217 Component Village Land Classification Private Land (ha) Community Land (ha) Total Land (ha ) Muck disposal Site M-7 BTK Shakti Muck disposal Site M-8 0 (BTK) Muck disposal Site M-9 Sherbang Muck disposal Site M-10 Sherbang Muck disposal Site M-1 Sherbang Muck disposal Site M-12 Kherteng Muck disposal Site M-13 Kumba Muck disposal Site M-14 Kumba Muck disposal Site M-15 Muchat Total Muck, if not securely transported and dumped at pre-designated sites, can have serious environmental impacts, such as: Muck, if not disposed properly, can be washed away into the main river which can cause negative impacts on the aquatic ecosystem of the river. Muck disposal can lead to impacts on various aspects of environment. Normally, the land is cleared before muck disposal. During clearing operations, trees are cut, and undergrowth perishes as a result of muck disposal. In many of the sites, muck is stacked without adequate stabilisation measures. In such a scenario, the muck moves along with runoff and creates landslide like situations. Many a times, boulders/large stone pieces enter the river/water body, affecting the benthic fauna, fisheries and other components of aquatic biota. Normally muck disposal is done at low lying areas, which get filled up due to stacking of muck. This can sometimes affect the natural drainage pattern of the area leading to accumulation of water or partial WAPCOS Limited 8-24

218 flooding of some area which can provide ideal breeding habitat for mosquitoes. The muck disposal sites will be suitably stabilized on completion of the muck disposal. The details of stabilization of muck disposal sites are outlined in Environmental Management Plan covered in Volume-II of this Report. v) Acquisition of land The total land required for the project is ha. A part of this land is required for labour camps, quarry sites, muck disposal storage of construction material, siting of construction equipment, which will be required temporarily and returned once the construction phase is over. Permanent acquisition of land is required for barrage axis, submergence area, project colony, etc. The details of land required for various project appurtenances is given in Table The ownership-wise status is given in Table S. No TABLE-8.14 Land requirement for Nyamjang chhu hydroelectric project Component Village Private Total Community Land Land Land (ha) (ha) (ha ) Submergence Area ( Left Bank Soksen up to Barriage) Submergence Area ( Right Bank Lumpo up to Barriage) Submergence Area ( River area up to Barriage) Upstream Headworks Soksen and Lumpo (50-50) Soksen WAPCOS Limited Soksen Kyaleyteng Shakti Gispu Head Race Tunnel 10 Sherbang Kherteng Phoomang Bagar

219 S. No. Component Village WAPCOS Limited 8-26 Private Land (ha) Community Land (ha) Total Land (ha ) 14 Adits - 1 Kyaleyteng Adits - 2 Shakti Adits - 3 Shakti Adits - 4 Shakti Adits - 5 Sherbang Adits - 6 ( equally Kherteng/Pho 19 in three villages) omang/bagar Kherteng/Pho Adits omang/bagar Adits - 8 Kungba Adits - 9 Kherteng Tail Race Tunnel Kherteng G IB Kherteng MAT Kherteng Power House Kherteng Surge Shaft (equally in three villages) Kherteng, Phoomang, Bagar Pressure Shaft (equally in three villages) Kherteng, Phoomang, Bagar Switchyard Kherteng Muck disposal Muchat Sites M-1 31 M-2 Muchat M-3 Kyaleyteng M-4 Shakti M-5 Shakti (BTK) M-6 Shakti (BTK) M-7 BTK M-8 BTK M-9 Shakti (BTK) M-10 Sherbang M-11 Sherbang

220 S. No. Component Village WAPCOS Limited 8-27 Private Land (ha) Community Land (ha) Total Land (ha ) 41 M-12 Sherbang M-13 Kherteng M-14 Kumba M-15 Kumba Colonies Sherbang Labour Camps ( equally in three Kyaleyteng, Kherteng, villages ) Sherbang 47 Workshop,Centerl ized store and Fabrication yard Kherteng Explosive Magazines ( 2 nos) (50-50) Crusher,Batching plant and aggregate Storage (2 nos )(50-50) Contractor colonies (Temp )equally in three villages Adit Portals ( 1 to 9 ),TRT,Cables tunnel Portals (for cover ) Storage area at different works sites Access Roads to Query 500 mts each Access Roads to Inlet Portal ADIT 1 ( 15 mtrs RoW) Access Roads to Adits - 2, 3 Access Roads to Adits - 5 Sherbang / Kyaleyteng Kerteng / Shakti Kherteng/She rbang/kyaleyt eng respective villages of Adits Socksen,resp ective villages of Adits, s.shaft, MAT, GIB &TRT Socksen, Muchat,Shakti, Sherbang, Lumla Kyaleyteng Shakti Sherbang

221 S. No Component Access Roads to Adits - 6 Access Roads to Adits - 7 Access Roads to Adits - 8 Access Roads to Adits - 9 Access Roads to MuckDumpng 3 Access Roads to MuckDumpng 4 Access Roads to Surge Shaft Access Roads to M.A.T. Access Roads to Cables tunnel Access Roads to T.R.T Quarry (Q -2 to Q-7 ) Village Kherteng/Pho omang/bagar Kherteng/Pho omang/bagar Private Land (ha) Community Land (ha) Total Land (ha ) Kungba Kherteng Kyaleyteng Shakti Kherteng Kherteng Kherteng Kherteng Total TABLE-8.15 Ownership status of land to be acquired for Nyamjang chhu hydroelectric project S. No. Type of land Area (ha) 1 Private land Community land Total It can be observed from Table-8.15, that about ha of community land and ha of private land is to be acquired. The community land has been considered as the forest land for the purpose of preparation of Environmental Management Plan. Appropriate plan for compensation of forest and private land to be acquired for the project has been formulated and is covered as a part of Environmental Management Plan outlined in Volume-II of this Report. WAPCOS Limited 8-28

222 vi) Impacts due to roads A network of new roads is required to facilitate completion of the project as per anticipated time schedule. Major components like Barrage, Power House, Surge Shaft and Permanent Colonies for the project near village Kharteng and Zimithang will require construction of new roads on the left bank. A bridge has to be constructed across river Nyamjang Chhu upstream of the existing BTK bridge to approach adits to HRT from the existing road on right bank. The total length of new roads to be constructed has been estimated as km as detailed in Table TABLE-8.16 List of new roads to be constructed Connecting details Length (km) Length of road to reach various adits 54.5 and other project components Length of road from existing road to 2.5 Power House Length of internal road from existing 3.0 road at Barrage on Right bank and new Road on Left bank. Total 60.0 Apart from the above major roads about 40 km of road network will be required for approach to the various muck dumping yards. About 120 km of existing roads in the project area from Tawang to Zimithang may require strengthening and widening including bridges and cross drainage works. The construction of roads can lead to the following impacts: The topography of the project area has steep to precipitatuous slope, which descends rapidly into narrow valleys. The conditions can give rise to erosion hazards due to net downhill movement of soil aggregates. Removal of trees on slopes and re-working of the slopes in the immediate vicinity of roads can encourage landslides, erosion gullies, etc. With the removal of vegetal cover, erosive action of water gets pronounced and accelerates the process of soil erosion and formation of deep gullies. Consequently, the hill faces are bared of soil vegetative cover and enormous quantities of soil and rock can move down the rivers, and in some cases, the road itself may get washed out. WAPCOS Limited 8-29

223 Construction of new roads increases the accessibility of a hitherto undisturbed areas resulting in greater human interferences and subsequent adverse impacts on the ecosystem. Increased air pollution during construction phase. 8.6 IMPACTS ON BIOLOGICAL ENVIRONMENT a) Construction phase Impacts on Terrestrial flora i) Increased human interferences The direct impact of construction activity of any water resource project in a Himalayan terrain is generally limited in the vicinity of the construction sites only. As mentioned earlier, a large population (11,200) including technical staff, workers and other group of people are likely to congregate in the area during the project construction phase. It can be assumed that the technical staff will be of higher economic status and will live in a more urbanized habitat, and will not use wood as fuel, if adequate alternate sources of fuel are provided. However, workers and other population groups residing in the area may use fuel wood, if no alternate fuel is provided for whom alternate fuel could be provided. There will be an increase in population by about of which about 9000 are likely to use fuel wood. On an average, the fuel wood requirements will be of the order of (1.0 x 365 x 9000 x 10-3 ) 3785 m 3. The wood generated by cutting tree is about 2 to 3 m 3. Thus every year fuel wood equivalent to bout trees will be cut, which means every year on an average about 2-3 ha of forest area will be cleared for meeting fuel wood requirements, if no alternate sources of fuel are provided. Hence to minimize impacts, community kitchens have been recommended. These community kitchens shall use LPG or diesel as fuel. The details are covered in Environmental Management Plan covered in Volume-II of this Report. The other major impact on the flora in and around the project area would be due to increased level of human interferences. The workers may also cut trees to meet their requirements for construction of houses and other needs. Thus, if proper measures are not undertaken, adverse impacts on terrestrial flora is WAPCOS Limited 8-30

224 anticipated. Since, labour camps are proposed to be constructed by the contractor along with necessary facilities, such impacts are not envisaged. During construction of various components of the project, e.g., road, colony, dam axis, muck disposal, etc. trees will have to be cleared. The tree felling or clearing shall be done by the Forest Department. Impacts due to Vehicular movement and blasting Dust is expected to be generated during blasting, vehicle movement for transportation of construction material or construction waste. The dust particles shall settle on the foliage of trees and plants, thereby reduction in amount of sunlight falling on tree foliage. This will reduce the photosynthetic activity. Based on experience in similar settings, the impact is expected to be localized upto a maximum of 50 to 100 m from the source. In addition, the area experiences rainfall for almost 8 to 9 months in a year. Thus, minimal deposition of dust is expected on flora. Thus, no significant impact is expected on this account. Acquisition of forest land During project construction phase, land will be required for location of construction equipment, storage of construction material, muck disposal, widening of existing roads and construction of new project roads. The total land requirement for the project is ha of which ha is the community land. A part of the community land also includes forest land as well. For EMP purposes, the entire community land has been considered as the forest land. The forest in the area has already been degraded due to a large-scale human interference. Though the project area is located in an ecologically sensitive area, the forests in and around the project area are quite degraded. The tree density in the dam site and submergence area is about 250 and 270 trees/ha respectively. Normally in a dense forest, tree density is of the order of trees/ha. Thus, in land to be acquired for the project, the tree density is low to moderate. Likewise, no rare and endangered species are observed in the forest to be acquired for the project. Thus, no adverse impacts are anticipated on this account. WAPCOS Limited 8-31

225 8.6.2 Impacts on Terrestrial fauna a) Construction phase Disturbance to wildlife The total land required for the project is ha of which ha comes under submergence, (including river bed). The details of submergence area are given in Table S. No. Component Submergence Area (Left Bank up to Barriage) Submergence Area (Right Bank up to Barriage) Submergence Area (River area up to Barriage) TABLE-8.17 Details of submergence area Village Land Classification Private Land (ha) Community Land (ha) Total Land (ha ) Soksen Lumpo Soksen and Lumpo Total The balance ( ha) land is required for other project appurtenances. Based on the field survey and interaction with locals, it was confirmed that no major wildlife is reported in the proposed submergence area. It would be worthwhile to mention here that most of the submergence lies within the gorge portion. Thus, creation of a reservoir due to the proposed project is not expected to cause any significant adverse impact on wildlife movement. The project area and its surroundings are not reported to serve as habitat for wildlife nor do they lie on any known migratory route. Thus, no impacts are anticipated on this account. During the construction period, large number of machinery and construction workers shall be mobilized, which may create disturbance to wildlife population in the vicinity of project area. The operation of various equipments will generate significant noise, especially during blasting which will have adverse impact on WAPCOS Limited 8-32

226 fauna of the area. The noise may scare the fauna and force them to migrate to other areas. Likewise siting of construction plants, workshops, stores, labour camps etc. could also lead to adverse impact on fauna of the area. During the construction phase, accessibility to area will lead to influx of workers and the people associated with the allied activities from outside will also increase. Increase in human interference could have an impact on terrestrial ecosystem. The other major impact could be the blasting to be carried out during construction phase. This impact needs to be mitigated by adopting controlled blasting and strict surveillance regime and the same is proposed to be used in the project. This will reduce the noise level and vibrations due to blasting to a great extent. Likewise, siting of construction equipment, godowns, stores, labour camps, etc. may generally disturb the fauna in the area. However, no large-scale fauna is observed in the area. Thus, impacts on this account are not expected to be significant. However, few stray animals sometimes venture in and around the project site. Thus, to minimize any harm due to poaching activities from immigrant labour population, strict anti-poaching surveillance measures need to be implemented, especially during project construction phase. The same have been suggested as a part of the Environmental Management Plan (EMP). Impacts on migratory routes The faunal species observed in the project area are not migratory in nature. The proposed submergence area is not the migratory route of wild animals. The construction of the proposed Nyamjangchhu H.E. project will form a reservoir of about ha, which is also not reported to be on the migratory route of any major faunal species. Impacts on avi-fauna The project area and its surroundings are quite rich in avi-fauna. However, water birds are not very common in the area. The main reason for this phenomenon is that water birds generally require quiescent or slow moving water environment. However, in the proposed project area and its surroundings due to terrain conditions, water flow is swift, which does not provide suitable habitat for the growth of water birds. With the damming of the river, a reservoir of an area of WAPCOS Limited 8-33

227 about ha will be created, with quiescent/tranquil conditions. The reservoir banks will have wet environment throughout the year which can lead to proliferation of vegetation e.g. grass, etc. along the reservoir banks. Such conditions are generally ideal for various kinds of birds, especially, water birds. This is expected to increase the avi-faunal population of the area. b) Operation phase i) Increased accessibility During the project operation phase, the accessibility to the area will improve due to construction of roads, which in turn may increase human interferences leading to marginal adverse impacts on the terrestrial ecosystem. The increased accessibility to the area can lead to increased human interferences in the form of illegal logging, lopping of trees, collection of non-timber forest produce, etc. Since significant wildlife population is not found in the region, adverse impacts of such interferences are likely to be marginal. The details of measures to improve the terrestrial ecology of the area are covered in separate volume of this Report Aquatic Flora a) Construction phase During construction phase wastewater mostly from domestic source will be discharged mostly from various camps of workers actively engaged in the project area. Around 0.78 mld of water is required for the workers during the peak construction phase out of which 80% (i.e. about 0.63 mld) will be discharged back to the river as wastes, more or less as a point sources from various congregation sites where workers will reside. The average minimum flow during lean season is about 12.3 cumec. However, sufficient water for dilution will be available in Nyamjangchhu to keep the DO of the river to significantly high levels. b) Operation phase The completion of Nyamjangchhu hydroelectric Project would bring about significant changes in the riverine ecology, as the river transforms from a fastflowing water system to a quiescent lacustrine environment. Such an alteration of the habitat would bring changes in physical, chemical and biotic life. Among the biotic communities, certain species can survive the transitional phase and WAPCOS Limited 8-34

228 can adapt to the changed riverine habitat. There are other species amongst the biotic communities, which, however, for varied reasons related to feeding and reproductive characteristics cannot acclimatize to the changed environment, and may disappear in the early years of impoundment of water. The micro-biotic organisms especially diatoms, blue-green and green algae before the operation of project, have their habitats beneath boulders, stones, fallen logs along the river, where depth is such that light penetration can take place. But with the damming of river, these organisms may perish as a result of increase in depth Impacts on Aquatic Fauna Construction phase Impacts due to excavation of construction material from river bed During the construction phase a large quantity of construction material like stones, pebbles, gravel and sand would be needed. Significant amount of material is available in the river bed. It is proposed to extract construction material from borrow areas in the river bed. The extraction of construction material may affects the river water quality due to increase in the turbidity levels. This is mainly because the dredged material gets released during one or all the operations mentioned below: excavation of material from the river bed. loss of material during transport to the surface. overflow from the dredger while loading loss of material from the dredger during transportation. The cumulative impact of all the above operations is increase in turbidity levels. Good dredging practices can however, minimize turbidity. It has also been observed that slope collapse is the major factor responsible for increase in the turbidity levels. If the depth of cut is too high, there is possibility of slope collapse, which releases a sediment cloud. This will further move outside the suction radius of dredged head. In order to avoid this typical situation, the depth of cut be restricted to: γ H/C < 5.5 where, γ - unit weight of the soil H - depth of soil C - Cohesive strength of soil WAPCOS Limited 8-35

229 The dredging and deposition of dredged material may affect the survival and propagation of benthic organisms. The macro-benthic life which remains attached to the stones, boulders etc. gets dislodged and is carried away downstream by turbulent flow. The areas from where construction material is excavated, benthic fauna gets destroyed. In due course of time, however, the area gets recolonized, with fresh benthic fauna. The density and diversity of benthic fauna, will however, be less as compared with the pre-dredging levels. The second important impact is on the spawning areas of fishes. Almost all the cold water fish breed in the flowing waters. The spawning areas of these fish species are found amongst pebbles, gravel, sand etc. The eggs are sticky in nature and remain embedded in the gravel and subsequently hatch. Any disturbance of stream bottom will result in adverse impacts on fish eggs. Even increase in fine solids beyond 25 ppm will result in deposition of silt over the eggs, which would result in asphyxiation of developing embryo and also choking of gills of young newly emerged fry. Thus, if adequate precautions during dredging operations are not undertaken, then significant adverse impacts on aquatic ecology are anticipated. Impacts due to discharge of sewage from labour camp/colony The proposed hydro-power project envisages construction of a project colony at village Sherbang. The labour camp and colonies are proposed at Kyaleyteng, Kherteng, Sherbang. This would result in emergence of domestic waste water which is usually discharged into the river. However, it is proposed to commission appropriate units for treatment of domestic sewage before its disposal in to the river. Due to perennial nature of river Nyamjangchhu, it maintains sufficient flow throughout the year which is sufficient to dilute the treated sewage from residential colonies. Therefore, as mentioned earlier, no adverse impacts on water quality are anticipated due to discharge of sewage from labour camp/colony. Impacts due to human activities Accumulation of labour force in the project area might result in enhancement in indiscriminate fishing including use of explosives. The use of explosive material WAPCOS Limited 8-36

230 to kill fishes in the river in the project area would result in complete loss of fishes and other aquatic life making a river stretch completely barren. Indiscriminate fishing will reduce fish stock availability for commercial and sport fishermen. These aspects have been adequately covered in the Environmental Management Plan (EMP) outlined Separate Volume of this Report. (b) Operation Phase Impacts due to damming of river The damming of river Nyamjanghhu due to the proposed hydroelectric project in creation of ha of submergence area. The dam will change the fast flowing river to a quiscent lacustrine environment. The creation of a pond will bring about a number of alterations in physical, abiotic and biotic parameters both in upstream and downstream directions of the proposed barrage site. The micro and macro benthic biota is likely to be most severely affected as a result of the proposed project. The positive impact of the project will be the formation of a water body which can be used for fish stocks on commercial basis to meet the protein requirement of region. The commercial fishing in the proposed reservoir would be successful, provided all tree stumps and other undesirable objects are removed before submergence. The existence of tree stumps and other objects will hinder the operation of deep water nets. The nets will get entangled in the tree stumps and may be damaged. The reduction in flow rate of river Nyamjanghhu especially during lean period is likely to increase turbidity levels downstream of the dam. Further reduction in rate of flow may even create condition of semi-dessication in certain stretches of the river. This would result in loss of fish life by poaching. Hence, it is essential to maintain minimum flow required for well being of fish life till the disposal point of the tail race discharge. Impacts on migratory fish species The obstruction created by the dam would hinder migration of species especially the Mahseers (from downstream to upper reaches) and Schizothorax sp. (from upper reaches to the lower reaches). These fishes undertake annual migration for feeding and breeding. Therefore, fish migration path may be obstructed due to WAPCOS Limited 8-37

231 high dam and fishes are expected to congregate below the dam wall. Under this situation poaching activities may increase in the area. Most of the species will shift to the section of the river where they find favourable environment for breeding since the dam is 11.5 m high construction of fish ladders is a feasible option. However, it is also proposed that the artificial seed production in hatchery may be adopted which can be stocked in the river stretches downstream and upstream of the proposed barrage. 8.7 IMPACTS ON SOCIO-ECONOMIC ENVIRONMENT A project of this magnitude is likely to entail both positive as well as negative impacts on the socio-cultural fabric of the area. During construction and operation phases, a lot of allied activities will mushroom in the project area Impacts due to influx of labour force During the construction phase a large labour force, including skilled, semi-skilled and un-skilled labour force of the order of about 3500 persons, is expected to immigrate into the project area. It is felt that most of the labour force would come from other parts of the country. However, some of the locals would also be employed to work in the project. The labour force would stay near to the project construction sites. The project will also lead to certain negative impacts. The most important negative impact would be during the construction phase. The labour force that would work in the construction site would settle around the site. They would temporarily reside there. This may lead to filth, in terms of domestic wastewater, human waste, etc. Besides, other deleterious impacts are likely to emerge due to inter-mixing of the local communities with the labour force. Differences in social, cultural and economic conditions among the locals and labour force could also lead to friction between the migrant labour population and the total population Economic impacts of the project Apart from direct employment, the opportunities for indirect employment will also be generated which would provide great impetus to the economy of the local area. Various types of business like shops, food-stall, tea stalls, etc. besides a variety of suppliers, traders, transporters will concentrate here and benefit immensely as demand will increase significantly for almost all types of WAPCOS Limited 8-38

232 goods and services. The business community as a whole will be benefited. The locals will avail these opportunities arising from the project and increase their income levels. With the increase in the income levels, there will be an improvement in the infrastructure facilities in the area Impacts due to land acquisition Another most important deleterious impact during construction phase will be that, pertaining to land acquisition. About ha of land proposed to be acquired for the proposed Nyamjangchhu hydro-electric project. Of this about ha is private land. The details of land acquisition, project appurtenances-wise and ownership-wise, are depicted in Tables 8.14 and 8.15 of this Chapter. It is observed that about ha of private land is proposed to be acquired from -5 hamlets/villages. It is observed that about 47 PAFs are likely to lose land in varying proportions. No family is likely to lose homestead on accouont of land acquisition for the project. The list of Project affected hamlets/villages is depicted in Table TABLE 8.18 Project affected hamlets/villages due to the process of land acquisition S. No. Name of Project Affected hamlets/ villages 1 Khaleteng 2 Kharteng 3 Kungba 4 Lumla 5 Soksen Impacts on cultural/religious/historical monuments Apart from village temple in the study area, monuments of cultural, religious, historical or archaeological importance are not reported in the project as well as the study area. Thus, no impact on such structures is envisaged. 8.8 INCREASED INCIDENCE OF WATER-RELATED DISEASES Increased incidence of water-related diseases The construction of a barrage would convert riverine ecosystem into a lacustrine ecosystem. The vectors of various diseases may breed in shallow parts of the WAPCOS Limited 8-39

233 impounded water. The magnitude of breeding sites for mosquitoes and other vectors in the impounded water is in direct proportion to the length of the shoreline. Since, this is a run-of river project in a mountainous region, increase in water spread area will be marginal and it would remain mostly confined in the gorge of the river, the increase in the incidence of water borne disease is not expected. Further, mosquitoes are normally observed upto a maximum elevation of about 2000 m above sea level. The proposed project is located just above this elevation., Hence, increase in incidence of mosquitoes is not expected at the barrage site. The power house is located at an elevation of about 1000 m above men sea level. Thus at this site and at the location of other project appurtenances, which are at a lower elevation could face increased incidence of malaria as a result of various factors like aggregation of labour, formation of stagnant pools near labour camps, colonies, etc. may lead to the increased incidence of such diseases around the project area. Labour camps located at lower elevations, especially close to the power house site could be vulnerable to increased incidence of water-borne diseases, if adequate measures are not undertaken Aggregation of labour About 3500 labourers and technical staff will congregate in the project area during peak construction phase. The total increase in population is expected to be of the order of Most of the labour would come from various parts of the country. The labourer would live in dormitories provided by the Contractor. Proper sanitary facilities are generally provided. Hence, a proper surveillance and immunization schedule needs to be developed for the labour population migrating into the project area Excavations The excavation of earth from borrow pits etc. is one of the major factor for the increase in prevalence of malaria. After excavation of construction material, the depressions are generally left without treatment where water gets collected. These pools of water, then serves as breeding grounds for mosquitoes. However, in the present case, the borrow areas are within the river bed, which in any case remain under water. Thus, no additional habitat for mosquito breeding is created due to excavation. The flight of mosquito is generally limited up to 1 to 2 km from the WAPCOS Limited 8-40

234 breeding sites. Since, no residential areas are located within 1 km from the reservoir, periphery, increased incidences of malaria are not anticipated. However, labour camps, etc. could be vulnerable to increased incidence of malaria, if proper control measures are not undertaken Inadequate facilities in labour camps Improperly planned labour camps generally tend to become slums, with inadequate facilities for potable water supply and sewage treatment and disposal. This could lead to outbreak of epidemics of water-borne diseases. Adequate measures for supply of potable water and sewage treatment have been recommended as a part of Environmental Management Plan outlined in separate Volume of this Report. 8.9 IMPACTS ON GEOLOGICAL ENVIRONMENT The project area lies mainly within Central Crystallines represented by Sela Group of rocks (Palaeoproterozoic) that are dominated by coarse grained quartz biotite gneiss. The Main Central Thrust (MCT), separating Sela Group from the Lesser Himalayan formations is disposed 60 km to the south, but, the Lumla Window (Yin et al. 2006) comprising the interbedded biotite schist and quartzites of Lumla Formation (Mesoproterozoic) lies 15 km south of the barrage site. In general the strata have gentle dips that are northwesterly in upstream area (N330/30), northeasterly in central area (N /30) and southerly dips in the downstream area (N170/30). A maximum of four joint sets have been identified separately for upstream, central and downstream areas of the project. The site for the proposed barrage across the River Nyamjang Chhu is located over a major lacustrine deposit formed within the gneissic terrain of Central Crystallines. The general foliation dip of the rocks, that also represents the main joint set, is towards right bank, viz N / The set of sub-vertical transverse joints, striking across the river, constitutes the other important and conspicuous feature at the site. The Zimithang Fault Scarp, a conspicuous +25m high feature, also strikes sub-parallel to the transverse set of joints. The lacustrine deposit is dominated by fine and medium sand and is characterized by complete absence of pebbly horizons m thick coarser river borne material comprising sand, gravel and pebbles overlies the lacustrine deposit. The investigations by drilling have confirmed the interpreted thickness of the lacustrine WAPCOS Limited 8-41

235 deposit that is as much as 91.5m. The overall grain size distribution pattern in the barrage area reveals dominance of fine sand that ranges between 44% and 91%. This is followed by medium sand that is in proportions of 4% to 41% and silt in the proportions of 7% to 38%. The coarse sand is limited to stray pockets in low proportions. Clay fraction is not found. The depth of SPT N value of 20 or less is found varying between depths 10.5m and 22.5m, and is nil in one hole. The average depth works out to be 13.25m. Along the barrage axis, the SPT N value of 20 or less is restricted to a maximum depth of 15m, and an average depth of 9m. In general, the permeability of the material ranges between 1.01x10-3 and 4.5x10-3 cm/sec with lower values ranging between 1.7x10-4 and 9.13x10-4 cm/sec. The material, therefore, is generally having medium permeability, and low permeability zones are limited to insignificant pockets, like in BH-5 and BH-5A. The barrage is accordingly to be founded on material with medium permeability. Atterberg s Limit indicates the material to be non-plastic. The seismic velocities of the deposit vary from 380 to 4000 m/s and have been related to unconsolidated and consolidated material. Seismo-tectonic evaluation of the site has revealed that the area falls in the most seismically susceptible regions of the Himalaya, viz Zone-V of the Seismic Zoning Map of India (Anon. 2002). It also falls within the Isoseismal-IX of the Assam Earthquake of 12 June 1897 (Anon. 2000). The site specific design earthquake parameter studies have been conducted by the University of Roorkee and, for MCE condition, is estimated to be Ms=8.0 magnitude earthquake occurring at MCT (Anon. 2009). The PGA values for MCE and DBE conditions are estimated to be 0.36g and 0.18g, respectively. The investigation results, in particular SPT and permeability, present the risk of liquefaction (Seed and Idriss 1971). In the foundation area of the proposed barrage, the average depth of material susceptible to liquefaction is about 9m. However, detailed palaeo-seismic studies at the site reveal that the lacustrine deposit and the recent river terraces are intact and completely devoid of any feature like sand dyke, neo-tectonic activity, etc. This feature may be considered as indicative of reduced risk of liquefaction at the project site. For design purpose, it is proposed to excavate potentially liquefiable material down to the maximum depth of about 14m from the ground level, i.e. El 2100m, all WAPCOS Limited 8-42

236 along the structures at the diversion site. The area under the barrage would be covered with geo- membrane to restrict the upward movement of underneath soil particles to the treated surface and at the same time it could also be ensured that pore pressure shall be released out by allowing seepage of water through membrane and thus safeguard the barrage structure from uplift pressure. The excavated zone is proposed to be back-filled with well graded and compacted material. The particle size of the back-fill shall be within the range of 0.1 mm to 150 mm for ensuring that the GSD curve shall lie out of the region which is more susceptible to liquefaction (Tsuchida 1970). It has been proposed that prior to placing the back-fill, dynamic compaction and vibro-floatation techniques shall be used to treat the foundation strata. The graded back-fill shall be compacted using vibratory roller to achieve a relative density of more than 80%. The degree of compaction shall be based on minimum SPT resistance requirements which could be related to relative density in the manner suggested by Gibbs & Holtz (1957). The foundation excavation area is expected to be saturated. For controlling seepage in the excavation area, a plastic concrete cut-off wall is proposed in the upstream of the barrage. The m long Head Race Tunnel is to be excavated for a length of 11316m through quartz-biotite gneiss in the upstream side and remaining length of 12134m through inter-bedded quartzite and schist in the downstream side. The contact between these two formations is represented by Lumla Thrust that is found to be tight in the project area. The entire powerhouse complex including surge shaft, pressure shafts, underground powerhouse cavern, transformer cavern, etc. are located within the inter-bedded sequence of quartzite and schist. The portals of the tunnels and the adits are mostly located in rock. WAPCOS Limited 8-43

237 9.1 GENERAL CHAPTER - 9 CONSTRUCTION METHODOLOGY The project envisages construction of barrage, a head regulator, Feeder Channel, desilting chamber, collection pool & intake, Head race tunnel, surge shaft, pressure shaft, underground power house, tail race tunnel and all infrastructure works. The construction methodology and equipment planning for various works is based on the site conditions prevailing in the project area. Construction activities are planned in such a way that the project will be completed in the shortest possible time period. The following assumptions have been made for construction methodology and equipment planning of the project. All the pre-construction activities like land acquisition, infrastructure works and government approvals are completed before the start of construction works on main components of the project. All civil, hydro-mechanical and electro-mechanical works are executed in following main packages : CIVIL WORKS Package I : Barrage and Desilting works Package II : Head Race Tunnel from RD-0.00m to RD-8,400.00m Package III : Head Race Tunnel from RD-8,400.00m to RD-16,875.00m Package IV : Head Race Tunnel from RD- 16,875.00m to RD-23, m Package V : Civil works for Surge Shaft and Pressure Shaft Package VI : Civil works for Power House, Transformer Cavern, Tail Race Tunnel and Switch Yard. HYDRO-MECHANICAL WORKS Package VII : Hydro Mechanical works comprising of gates, hoists and Pressure Shafts steel liner Electro-Mechanical Works Package VIII : Generating Units (Turbine & Generator), Cooling Water System, Drainage/ Dewatering System, Unit Control & Automation, Bus duct. Package IX : Valves-MIV& BFV Package X : EOT Crane, Package XI : Air Conditioning, Ventilation etc. Package XII : Fire Fighting, Package XIII : Transformers(Generator Transformer), WAPCOS Limited 9-1

238 Package XIV : 415 V Switchgear & 11 kv Switchgear Package XV : Illumination Package XVI : DG sets (construction power) Package XVII : Cable &Cable Trays Package XVIII : Switchyard & Protection metering Package XIX : Transformer (Dry Type UAT SST), Package XX : DC System (Battery & Battery Charger), UPS Package XXI : Miscellaneous and finishing works 9.2 BASIC ASESSMENT OF CONSTRUCTION METHODOLGY The project involves execution of large quantities of excavation and concreting for surface and underground structures. Considering the magnitude and nature of construction activity, mechanized construction has been considered for all type of construction job so as to achieve consistent quality at a faster rate for timely completion of the project. Special attention has been paid to the equipment planning for underground works as the restricted work space and constraints of geology make this exercise very critical. The construction of the project will involve simultaneous works on all the packages for civil, hydro-mechanical and electro-mechanical works for various project components. Tunneling in Head race Tunnel & underground excavation for power house and transformer cum GIS-Cavern is one of the most critical activities for the project and accordingly, the work is assumed to continue uninterrupted till its completion. 9.3 PRE CONSTRUCTION ACTIVITIES The activities proposed to be undertaken during Pre-construction work include the following: Detailed Topographical Survey and marking the Layout at site, Pre- construction geotechnical investigation Clearance from Government agencies like Pollution control board, Public health, Irrigation and Forest Clearance Acquisition of Land Financial closure Detailed design and preparation of tender documents for Civil, Electro-mechanical, Hydro mechanical works Award of Contracts Setting up of Site office Arranging of construction power Construction of approach roads/ paths Route survey of Transmission line Mining Licence for construction materials Formation of project team WAPCOS Limited 9-2

239 9.4 APPROACH ROADS AND BRIDGE Transportation of heavy machines and equipments will be required for construction purpose. Construction of new access roads and bridges, widening of existing roads and improvement in grade of existing roads shall be undertaken before starting construction of main project components. These roads would be connected through an extensive network of project roads to various colonies, workshop, quarries etc. 9.5 BASIC CONSIDERATIONS Construction methodology and equipment planning has been carried out separately for execution of all project components. The types and sizes of equipment to be used have also been indicated while describing the construction methodology for each of the components under relevant subhead. The number of Machines/Equipment required for construction of each component has been worked out and their size and capacity has been arrived at after drawing the deployment schedule matching with the construction schedule. Most of the construction work shall be executed through contractors. The requirement of equipment as marked out herein has been utilized for analysis of rates and Cost Estimates. The prices of construction equipment are based on the prevalent market prices in India as on May, The project area is situated in a region where extensive rainfall occurs during monsoon. The working season is, therefore, limited to 9 months, beginning from October to June for open works. The underground works being critical are proposed to be carried out in two shifts of 20 hours/day. 9.6 DETAILED DESIGN AND CONSTRUCTION DRAWINGS The detailed design will be done in parallel with the Pre-construction works. It is envisaged that the design will be started soon after the preliminary works are completed. During Tender engineering, detailed design work will be started and construction drawings will be available by the time contracts are awarded. 9.7 BASIC ASSUMPTIONS FOR EQUIPMENT PLANNING Guidelines for preparation of Detailed Project Reports of Irrigation and multipurpose Projects issued by Central water Commission have been used WAPCOS Limited 9-3

240 for the planning of equipments. Basic assumptions made for the planning of equipment for various construction activities are enumerated below: Working hours of equipment All works are proposed to be done in two shifts and the scheduled working hours have been taken as 20 hours per day. 26 days/month have been considered on an average in a month Densities of Materials The calculations have been based on capacity of hauling units without considering the densities of different types of materials for excavation and the fill material Earth Volume conversion factor Suitable standard norms have been adopted for conversion of volumes in natural, loose and compacted state Operating Efficiency The operating efficiency of different types of equipment has been taken as 50 min per hour Muck Dumping Lead A lead of 15 km has been considered for dumping of muck that would be generated from Head Race Tunnel and a lead of 5 km is assumed for the dumping of muck that would be generated from Power House, TRT, Transformer Cavern, Barrage, Feeder Channel, Desilting Chamber and Collection Pool works. A lead of 10 km is assumed for the muck dumping of the material generated from Surge Shaft and Pressure Shaft works Concreting Lead A lead of 10 km is considered for the concrete works in Head Race Tunnel and 5 km is assumed for the concrete works in Power House, TRT, Transformer Cavern, Barrage, Feeder Channel, Desilting Chamber, Collection Pool, Surge Shaft and Pressure Shaft works. WAPCOS Limited 9-4

241 9.8 METHODOLOGY OF CONSTRUCTION FOR VARIOUS ACTIVITIES River diversion during construction River diversion works has been planned for construction of Barrage and Head Regulator. The construction of Barrage has to be taken up during non monsoon months of relatively low flow. The river will be diverted along one side of the river by construction of temporary cofferdams for the construction of the upstream works. The cofferdam will be made of river bed material properly compacted to the required level to prevent overtopping. An impervious layer of geo-membrane will be provided to prevent seepage through the body of the dam. To avoid puncturing, fine materials are placed below and over the impermeable layer. Rip rap protections will be provided on the river side to prevent scouring of the dam. It is expected that the cofferdam will be damaged during the monsoon season which will be repaired for the dry season. The construction of Barrage structures will be done in two stages and cofferdam will be provided accordingly. In the first stage, the river will be diverted towards the right bank. During the period, construction work on the left bank will be done. The work includes construction of Spillway (5 bays), Undersluice, Head Regulator, Feeder Channel, Desilting Chamber, Reservoir, intake structures and flood walls, upstream and downstream aprons and stilling basins. Likewise, the remaining bays of spillway and Earthen Dam that are on the right bank will be constructed during the second phase. During the period, the river will be diverted through the Undersluice and gated Spillway. The cofferdam will create the dry space in the right bank during this period Civil works Upstream works The deposits on the river bank shall be removed to have enough space for construction activities. The deposit will be used for the river diversion work and for rip rap protection works. The construction of cofferdam will be taken up parallel with the removal of deposits. The construction of Coffer dam would be taken up with 2 Nos of Dozers (200 HP), 2 Nos of Hydraulic Excavators of 1.5 cum bucket capacity, 2 Nos of Vibratory Rollers and sufficient number of 20/25 T Dumpers. The Coffer Dam is planned to be completed in three months. WAPCOS Limited 9-5

242 Phase-I Construction of 5 bays of Spillway, Undersluice and Head Regulator will be taken up in the first phase of Barrage works. Total of 3.0 lacs cum of earthwork is involved in these structures and by providing 3 Nos of Hydraulic Excavators of 1.5 m3 capacity working round the clock (with stand bye equipment) and fleet of dumpers, daily progress of 3,000 m3 is expected. Therefore, the excavation gets completed in 4 months. Adequate dewatering arrangements would be made during the excavation in foundation at Barrage complex. Dynamic compaction will commence immediately after the necessary excavation at Barrage site. The excavation for cut-off wall will commence immediately after dynamic compaction/compacted backfill at Barrage site. The deep excavation for cut-off wall will be done with Hydraulic Excavator BC- 30. Bentonite solution will be used during excavation of cut-off wall so as to avoid the side wall collapses. The excavation of cut-off wall up to the required level will be done and plastic concrete will be poured in the excavated trench by using a tremmie. The concrete work for Barrage base slab and other superstructure works will commence immediately after the completion of plastic concrete in cut-off walls. Concreting in the river bed, pertaining to under sluice, 5 bays of spillway and head regulator and adjacent structures will be taken up on priority in full swing by 2 nos. 30 m3 Batching plant and 2 Stationery 1 m3 Capacity Mixers, placement of concrete is planned by Transit mixers and Cranes with suitable Concrete Buckets. The concreting of under sluice, 5 bays of spillway and head regulator up to sill level will be completed in 2 months before onset of monsoon. The superstructure works of these structures will commence immediately after the concreting of the base slab. The Hydro-Mechanical works for these structures will be executed in parallel to the civil works of these components. All civil and hydro mechanical works for these components will get completed in 27 months after the start of work at Barrage site. WAPCOS Limited 9-6

243 During planning it is assumed that all the structures on the left bank that will be affected by the river flow will be completed in two seasons. Structures like floodwalls and the intake will be completed within the first eight months. The upstream and downstream apron, stilling basin and the rip rap protections will be completed within 27 months. After completing the First Phase works on the left bank, the river will be diverted through under sluice and the construction for Phase-II Barrage works will be taken up. Phase-II Construction of Earthen Dam and 6 bays Spillway will be taken up in this phase of Barrage works. 1.2 lacs cum of earthwork is involved in these structures and by providing 2 Nos. of Hydraulic Excavators of 1.5 cum capacity working round the clock (with stand bye equipment) and fleet of dumpers, daily progress of 2,000 m3 is expected. Therefore, the excavation gets completed in 3 months. Adequate dewatering arrangements would be made during the excavation in foundation at Barrage complex. Dynamic compaction will commence immediately after the necessary excavation at this phase of Barrage construction. The excavation for cut-off wall will commence immediately after dynamic compaction/compacted backfilling at this front. The deep excavation for cut-off wall will be done with a Hydraulic Excavator BC-30 and Bentonite solution will be used during excavation of cut-off wall so as to avoid the side wall collapses. The excavation of cut-off wall up to the required level will be done and plastic concrete will be poured in the excavated trench by using a tremmie. The concrete / earth filling work for this phase will commence immediately after the completion of plastic concrete in cut-off walls. Concreting in the river bed, pertaining to remaining bays of spillway will be taken up after necessary excavation / dynamic compaction. The concreting of remaining bays of spillway up to sill level will be completed in 2 months. The superstructure work of this structure will commence immediately after the concreting of the base slab. All civil works for these components will get completed in 18 months. WAPCOS Limited 9-7

244 The structures like Desilting Basin and Feeder channel can be constructed throughout the year. The excavation of the Desilting Basin will commence after the completion of flood wall beside the Desilting Basin. Work at Reservoir just downstream of Desilting Basin would be taken up simultaneously with the Desilting Basin. Excavation and backfilling at Desilting Basin, Reservoir and Feeder Channel would be taken up with 4 Nos. of Hydraulic excavators of 5.0 lacs cum bucket capacity and sufficient nos of 20/25 T Dumpers. Therefore, total earthwork of 5 lacs cum involved in these structures is planned to be completed in 6 months. Adequate dewatering arrangements would be made during the excavation at these fronts. The concrete work will commence immediately after the completion of excavation/backfilling work at these fronts. Concreting of the structures will be taken up on priority in full swing by 2 nos. 30 m3 Batching plant and 2 Stationery 1 m3 Capacity Mixers, placement of concrete is planned by Transit mixers and Cranes with suitable Concrete Buckets. The superstructure civil works for these structures will be carried in parallel to hydro mechanical works. All civil and hydro mechanical works for these components will get completed in 30 months after the start of work at these fronts. Equipments required for the construction of Coffer Dam, Earthen Dam, Spillway, Under Sluice, Head Regulator, Feeder Channel, Desilting Chambers and Collection Pool are shown in Annexure Headrace tunnel 6.2 m dia. Circular shaped, km long Head Race Tunnel has been proposed at the end of Collection pool for carrying water to the pressure shafts. 300 mm thick concrete lining has been proposed all along the length of the tunnel. The headrace tunnel will be started from the thirteen faces as shown in Fig All the adits shall be completed before the start of excavation of headrace tunnel. Construction of HRT Face-1 and Face-2 will be taken up from Adit-1 to HRT. Similarly Face-3/Face-4, Face-5/Face-6, Face-7/Face-8, Face-9/Face-10, Face-11/Face-12, and Face-13 will be taken up from Adit-2, Adit-3, Adit-4, Adit-5, Adit-6, and Adit-7 respectively. The critical reach of HRT is about 5000m between Face-8 and Face-9, so special attention in terms of resources is required at this front for completion of work in time schedule. WAPCOS Limited 9-8

245 Figure-9.1 The tunnel will be excavated by conventional drill and blast method using mechanised equipment. At each Adit, 3-Boom Drill Jumbo will be used for drilling holes and robotic shotcrete machine will be used for temporary rock support. After blasting, fresh air will be supplied at excavated face to remove gas and dust produced during blasting by a duct. The excavated muck will be loaded through one 1.5 cum bucket capacity hydraulic excavator and transported by dump trucks of 20/25 T capacity to muck dumping area. After excavation scaling will be done followed by the rock bolting and shotcreting. Pre-splitting or smooth blasting technique shall also be adopted to avoid over break. The proposed cycle time for the excavation and rock support of HRT along with equipment planning is enclosed as Annexure Overt Lining For overt lining it is proposed to take up more than half of upper portion of the tunnel. The concrete will be placed in the overt by using 6m long shutter form. Transit mixer of 6 cum capacity will be used for transportation of concrete from batching plant to concreting site. Pouring of concrete in the overt will be done through with 38 cum capacity truck mounted concrete pumps fitted with hydraulically operated placing boom. With this arrangement and suitable manipulation of boom, the concrete will be delivered from the pump. Invert Lining Invert lining will be taken up after the completion of overt lining of HRT in various reaches. A progress of 300 m/month on average is assumed for this activity. WAPCOS Limited 9-9

246 Surge shaft Construction of approach road to Adit to Surge Shaft bottom is planned to be completed during pre-construction works. The construction of Adit to Surge Shaft bottom would be taken up immediately after the start of Civil works. This Adit is planned to be completed in 4 months. Thereafter, a pilot shaft (235m deep & 4m dia.) would be constructed from bottom of Surge Shaft using Alimack Raise Climber with sufficient nos. of jack hammers, one Dozer of 200 HP, one Hydraulic Excavator of 1.5 cum capacity and sufficient nos. of 20/25 T Dumpers. This activity is planned to be completed in 5 months time while excavation of horizontal Pressure Shaft at EL-1940m would be in progress simultaneously. Once pilot shaft is made through, slashing of Surge Shaft can be done from the top to bottom. Pressure Shaft Two number 3.3 m dia circular steel lined pressure shafts each bifurcating into unit penstock of 2.0 m dia circular steel lined pressure shaft have been provided for taking the water to six pelton machines in underground power house. Each pressure shaft consists of horizontal and inclined portions. Adits to Horizontal Pressure Shafts at EL m, EL m and EL m would be completed before the start of excavation work in Pressure Shafts. The construction of horizontal pressure shafts at elevation of m shall be taken up by full face drilling and blasting method. The adit used for reaching the bottom of Surge Shaft will be used for construction of this portion of pressure shaft. The excavation shall be taken up with one 3Boom Drill Jumbo, one hydraulic excavator, one dozer (200HP) and sufficient nos of 10T/20T dumpers. Similarly the horizontal pressure shafts at El m and EL m shall be taken up individually with separate set of equipments as deployed at upper horizontal pressure shafts. Construction of horizontal pressure shaft at elevation of El m will be undertaken from branch tunnel from Main Access Tunnel to Power House. WAPCOS Limited 9-10

247 After the excavation in these horizontal Pressure Shafts, the excavation of inclined portion for a length of about 450 m will be taken up bottom upward by 2 Nos. of double motor diesel Raise climber. The excavation of inclined Pressure Shafts to required excavated diameter will be excavated in single phase. Firstly the 2 Nos of Raise Climbers will be mobilized at inclined Pressure Shafts between EL m to EL m. The excavation of these shafts will be completed in 9 months. Similarly the excavation of inclined Pressure Shafts at EL m to EL m (6 Nos) and at EL m to EL m (2 Nos) will be taken after the completion of inclined Pressure Shafts between EL m to EL m. The time taken to complete the excavation of the inclined Pressure Shaft at EL m to EL m (6 Nos) and at EL m to EL m (2 Nos) will be 12 months and 8 months respectively. The excavation and mucking will be taken by sufficient nos of Jack hammers, one Dozer (200 HP), one hydraulic excavator of 1.5 cum capacity and sufficient no of 10T/20T dumpers. Steel lining of pressure shafts will be undertaken after excavation is complete. Ferrules of 2.5m length shall be fabricated in the workshop outside and shall be transported on trailers to the pressure shafts for lowering. Inside the tunnels, ferrules shall be transported on trolleys travelling on rails and pulled by winch. For upper horizontal and inclined portion, steel lining shall proceed from bottom to top first and there after horizontal portion shall be taken. The concrete backfilling of these ferrules will immediately follow after the erection and welding of ferrules inside the shaft. The concrete shall be poured after welding 5 pieces of 2.5m ferrules. A progress of 40m/month (erection and backfilling) per shaft is planned for these inclined Pressure Shafts. The time taken to complete the ferrule erection/backfilling of the inclined Pressure Shaft at EL m to EL m (6 Nos), EL m to EL m (2 Nos) and at EL m to EL m (2 Nos) will be 15 months, 11 months and 12 months respectively. The ferrule erection/backfilling in horizontal pressure shafts at various benches will be followed only after the ferrule erection/backfilling in respective inclined pressure shafts. Equipment required for the construction of Pressure Shaft is shown in Annexure WAPCOS Limited 9-11

248 Powerhouse An underground Power House has been proposed on the left bank of Nyamjang Chhu River with the installed capacity of 780 MW comprising 6 units of 130 MW each. An underground excavation of 1.2 lacs cum is assessed in Power House and is expected to be completed in 25 months with two shifts operating. The construction of powerhouse involves co-ordination of civil works and electromechanical works. The main civil works in the powerhouse consists of excavation, rock support and concreting works. The excavation of Power House would be taken up after the excavation of the Adit to Power House Crown branching off from Main Access Tunnel to Service Bay in the Power House. This Adit would be extended through the length of the Power House and expanded sideways to the size of 20m x 7m. Power House excavation would be carried out by constructing suitable ramps for benching down. Movement of equipment would be carried through ramps. For excavation from EL m to EL m mucking would be done through adit to the crown of Power House including ramp removal. For excavation from EL m to EL m mucking would be carried out through Main Access Tunnel to Power House including Bus Duct Tunnels. Mucking of Power House below Service Bay level would be carried out through Main Access Tunnel as well as construction adit to Pressure Shaft and Tail Race Tunnel. Benching down of Power House from EL m to EL m would be carried out in two stages by making suitable ramps in each stage. For excavation from EL m to EL m mucking would be carried out through pressure shaft Tunnels. The bottom of the Power House will be excavated through Tail Race Tunnels. The equipment required for underground excavation of power house are 3 boom drill jumbo, 1.5 cum hydraulic excavator, 20/25T dumpers, wagon drills/crawler drills, jack hammers, shotcrete machine, grout pump, concrete pump, vibrator, transit mixers etc. Batching and mixing plant (90 cum/hr), 180 TPH aggregate processing plant would meet the concreting requirement of Power House. The installation of electromechanical equipment will be done in close coordination with the civil contractor. Almost all of the civil structures including the installation of overhead crane will be completed before the installation of electromechanical equipment. WAPCOS Limited 9-12

249 Transformer Cavern The excavation Work for Transformer Cavern of size 173mx16.3mx23m located on downstream of Power House Cavern will generate about 70,000 cum of excavated muck. The crown of this cavern would be accessed through 100 m long Adit branching off from adit to crown of Power House cavern. The construction adit to Transformer Cavern crown would be extended to full length of the Transformer Cavern. Thereafter, it would be enlarged sideways to the full width of the Transformer Cavern. Transformer Cavern excavation would be carried out by constructing suitable ramps for benching down. Movement of equipment would be carried through ramps. For excavation from EL m to EL m mucking would be carried out through adit to crown of Transformer Cavern including ramp removal. Mucking of Transformer Cavern at EL m to EL m would be carried out through the access tunnel branching off from Main Access Tunnel. The equipment required for this purpose are 3 boom drill jumbo.1.5 cum hydraulic excavator, 20/25T multi axle rear dumpers, wagon drills/crawler drills, jack hammers, shotcrete machine, grout pump, concrete pump, vibrator, transit mixers etc. Batching and mixing plant (90 cum/hr), 180 TPH aggregate processing plant would meet the concreting requirement of Transformer Cavern. Tailrace 7m dia. Circular shape, km long Tail Race Tunnel has been proposed from power house to discharge the water back to river. TRT will be concrete lined. The construction of Tail Race tunnel will be done from outlet face of TRT and from junction of the Main Access Tunnel with TRT. The tunnel will be excavated by drill and blast method using mechanised equipment. 3-Boom Drill Jumbo will be used for drill holes and robotic shotcrete machine will be used for temporary lining. An advance of 95 m/month from each face is proposed for the excavation of TRT. Concrete Lining of TRT will commence immediately after the completion of excavation work at respective faces. The lining of the tunnel is proposed to be done in two stages i.e. overt concrete will be done firstly followed by invert concrete lining. Two gantry shutters of 6m length are proposed to be used in TRT so as to achieve a progress of 6m/day and 150m/month in this reach. WAPCOS Limited 9-13

250 Bus Duct Tunnel and Switchyard The XLPE cables from Transformer cavern to surface Switch Yard will be taken through a 7m dia and 23m deep shaft and then through a Bus Bar Tunnel of 7.6m (H), 5.1m (W) and 769m length. The Bus Bar tunnel will be excavated from the Portal 100m/month. Work at Switch Yard will be taken up after completing Power House excavation and filling the muck at Switch Yard area. Concrete/Building works will immediately commence after the completion of necessary excavation/muck filling and foundation treatment works. The completion however, should be finished before the completion of installation of electromechanical equipment in the powerhouse. Equipment required for the construction of GIB Tunnel and Switch Yard is shown in Annexure Hydro Mechanical Equipment The fabrication of Barrage gates shall be done partly in manufacturer s workshop and partly at site. The civil contractors will co-ordinate with the agencies supplying such equipment and provide them all necessary support at site. Block outs and first stage anchor plates shall be provided in various structures during first stage concreting. The second stage embedded parts comprising of sill beams, tracks, seal seats & guides etc. shall be erected in these block outs before undertaking second stage concreting. The supply and installation of all Hydro mechanical equipment required at different locations shall be ensured to be completed in time so that the works related to components can be completed in scheduled time. 9.9 EQUIPMENT PLANNIING The list of equipment to be used is given in Table-9.1. S. No. 1 2 Equipment Raise Climber (Double motor) 3 Boom Drill Jumbo Package -I (Barrag e and Desilting works) TABLE-9.1 List of Equipments Package -II (HRT RD 0 TO m ) Package- III (HRT RD m TO m) Package- IV (HRT RD m to m) Package-V (Pressure Shaft and Surge Shaft) Packag e-vi (Power House and allied works) Total Tippers (20/25T)) Tippers (5.0m³) Excavators (1.5m³) J CB WAPCOS Limited 9-14

251 S. No. 7 Equipment Compressors (500cfm/600cfm) Package -I (Barrag e and Desilting works) Package -II (HRT RD 0 TO m ) Package- III (HRT RD m TO m) Package- IV (HRT RD m to m) Package-V (Pressure Shaft and Surge Shaft) Packag e-vi (Power House and allied works) Total DG Set (250KVA) DG Set (500KVA) Welding Set Ventilation Blower (80 HP) Dewatering Pumps Shotcrete Machine (30m 3 /hr) As per Req As per Req As per Req As per Req As per Req Concrete Placer Concrete Pump (38m 3 /hr) Grouting Pump Transit Mixer (6.0m³) Batching Plant (90m 3 /hr) Batching Plant (30m 3 /hr) D-8 Dozer (200HP) Vibrators As per As per As per As per Req As per Req As per Req Req Req Req 22 Jack Hammers As per As per As per As per Req As per Req As per Req Req Req Req 23 Mobile Crane (10T) Crushing Plant (180TPH) Water Tanker (11000ltrs) Crawler Drill Concrete Mixers (14/10) Rock Bolter Truck Mounted Scissor Platform Vibratory Compactor Road Roller Electric Winch (5T) EOT Crane (25T) Shutter (CIFA) 7m dia (6m Long) Shutter (CIFA) 6.7m dia (6m Long) 4 sets 8 Sets 10 Sets 8 set 26 sets 36 Crane 100T Excavator BC Explosive Van Ambulance Bus/Mini Bus Workshop LS LS LS LS LS LS 0 WAPCOS Limited 9-15

252 S. No Equipment Equipment Ventilation Ducting Diesel Tanker 7000ltrs Petrol Tanker 7000ltrs Water Sprinkler 10000ltrs Package -I (Barrag e and Desilting works) Package -II (HRT RD 0 TO m ) Package- III (HRT RD m TO m) Package- IV (HRT RD m to m) Package-V (Pressure Shaft and Surge Shaft) Packag e-vi (Power House and allied works) LS LS LS LS LS LS 0 Total WAPCOS Limited 9-16

253 EARTHQUAKE ENGINEERING STUDIES EQ : SITE SPECIFIC DESIGN EARTHQUAKE PARAMETERS FOR NYAMJANG CHHU H. E. PROJECT SITE, ARUNACHAL PRADESH DEPARTMENT OF EARTHQUAKE ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY ROORKEE ROORKEE INDIA

254 SITE SPECIFIC DESIGN EARTHQUAKE PARAMETERS FOR NYAMJANG CHHU H. E. PROJECT SITE, ARUNACHAL PRADESH Project No.EQD- 3017/ Oct 2009 FOR OFFICIAL USE ONLY DEPARTMENT OF EARTHQUAKE ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY ROORKEE ROORKEE INDIA.

255 PREFACE Bhilwara Energy Ltd., (BEL) has been entrusted with execution of Nyamjang Chhu H.E. Project in Arunachal Pradesh. The project is located (Latitude N and Longitude E) in Tawang district of Arunachal Pradesh on Nyamjang Chhu. BEL referred the study for Site-Specific Design Earthquake Parameters to the Department of Earthquake Engineering, Indian Institute of Technology Roorkee. Accordingly the studies related to Site Specific Design Earthquake Parameters were taken up. This is the final report containing recommendations for the site dependent spectra and time history of ground motion for seismic analysis of structures. Useful discussions held with BEL officials regarding the site specific studies are gratefully acknowledged. This study has been carried out by Prof. Ashwani Kumar, Prof. M. L. Sharma, Dr. H. R Wason, Dr. S. Mukerjee, Dr. M. Shrikhande, Dr. B. K. Maheshwari, Dr. J. Das and Dr. R. N Dubey. Roorkee Oct 2009 (Ashwani Kumar) Prof. and Head i

256 CONTENTS Preface... i Contents... ii List of Tables, Figures & Appendices... iii Executive Summary... iv 1.0 Introduction Regional geology and tectonics of the region Site Geology Earthquake occurrences Parameters for earthquake resistant design Definitions Maximum Considered Earthquake (MCE) Design Basis Earthquake (DBE) Seismogenic Sources around the Site Estimation of Maximum Considered Earthquake Earthquake Parameters Ground Motion Characteristics Acceleration Response Spectra Vertical Acceleration Safety Criteria Estimation of Design Basis Earthquake Earthquake Parameters Ground Motion Characteristics Acceleration Response Spectra Vertical Acceleration Safety Criteria Recommendations References ii

257 List of Tables, Figures and Appendices Caption Page No. Table I Peak ground horizontal acceleration from various sources around Nyamjang Chhu HE Project site, Arunachal Pradesh. 16 Table II Values of various parameter for response spectra for various values of percentage of damping for Nyamjang Chhu HE Project site, Arunachal Pradesh. 21 Fig. 1. Seismotectonic setup around the Nyamjang Chhu HE Project site, Arunachal Pradesh (Modified after Seismotectonic Atlas of India, Geological Survey of India, 2000) 11 Fig. 2. Seismicity map of the region around Nyamjang Chhu HE Project site showing the line AB considered to plot the depth section as given in Fig Fig. 3. Depth section across the seismogenic features around the Nyamjang Chhu HE project site for line AB as given in Fig Fig. 4. Time history of horizontal ground motion for Nyamjang Chhu HE Project site, Arunachal Pradesh (Normalised to 1g). 24 Fig. 5. Normalised horizontal acceleration spectra for various conditions Nyamjang Chhu HE site, Arunachal Pradesh. 24 Annexure I Occurrence of Earthquakes around the Nyamjang Chhu HE Project site, Arunachal Pradesh. 29 Annexure II Ground motion acceleration time history for Nyamjang Chhu HE Project site, Arunachal Pradesh (normalised to 1g) at 0.01 sec interval. 46 iii

258 EXECUTIVE SUMMARY Bhilwara Energy Ltd., (BEL) has been entrusted with execution of Nyamjang Chhu H.E. Project in Tawang district of Arunachal Pradesh. The project is located (Latitude N and Longitude E) on the river Nyamjang Chhu. BEL referred the study for sitespecific earthquake parameters to the Department of Earthquake Engineering, Indian Institute of Technology Roorkee. The Nyamjang Chhu HE Project site lies in seismic Zone V as per the seismic zoning map of India incorporated in Indian Standard Criteria for Earthquake Resistant Design of Structures (IS : 1893 (Part 1): 2002). The recommendations for the site specific earthquake design parameters for the site are based on the studies carried out related to the tectonics, regional geology, local geology around the site, earthquake occurrences (Annexure I) in the region around the site and the seismotectonic setup of the area (Fig. 1). The site specific design earthquake parameter for MCE condition is estimated to M s =8.0 magnitude earthquake occurring at MCT. The PGA values for MCE and DBE conditions and estimated to 0.36g and 0.18g respectively. Data for time history of earthquake ground motion for the dynamic analysis of the barrage are given in Annexure-II normalised to peak ground accelerations of 1.0 g. For MCE and DBE time history analysis ground motion data as given in Annexure-II will have to be multiplied by 0.36g and 0.18g respectively. The corresponding response spectra are given in Fig. 5 and Table II. Vertical spectral acceleration values may be taken as two third of the corresponding horizontal values. Similarly acceleration ordinates for the time history of vertical ground motion may be assumed as two third of the corresponding horizontal value. The site specific design acceleration spectra shall be used in place of the design response spectra, given in IS: 1893 (Part 1). The horizontal design seismic coefficient for preliminary 1 Z Sa design of Dam (primary structure) is evaluated as α h =.. where, Z is taken as the 3 2 g Sa estimated PGA coefficient for MCE (0.36 in this case) and value is obtained from Fig. 5 g (normalized horizontal acceleration spectra) corresponding to the fundamental time period of the dam T. For other (secondary structures), appropriate Reduction Factor R, as specified in IS: 1893 may be used along with Importance factor I=1. for calculating the horizontal seismic Z Sa I design coefficient as: Ah =.. 2 g R iv

259 SITE SPECIFIC DESIGN EARTHQUAKE PARAMETERS FOR NYAMJANG CHHU H.E PROJECT, ARUNACHAL PRADESH 1.0 INTRODUCTION 1.1 Bhilwara Energy Ltd., (BEL) has been entrusted with execution of Nyamjang Chhu H.E. Project in Arunachal Pradesh. The project is located (Latitude N and Longitude E) in Tawang district of Arunachal Pradesh on river Nyamjang Chhu. BEL referred the study for site-specific earthquake parameters to the Department of Earthquake Engineering, Indian Institute of Technology Roorkee. Accordingly the studies related to site specific design earthquake parameters was taken up. 1.2 The proposed dam site lies in seismic zone V as per the seismic zoning map of India as incorporated in Indian Standard Criteria for Earthquake Resistant Design of Structures IS:1893-(Part I) 2002 : General Provisions and Buildings. It is usually presumed that in design of normal structures adequate safety would be attained if structures were designed as per Codal recommendations. The probable intensity of earthquake in seismic zone V corresponds to Intensity IX on comprehensive intensity scale (MSK64). The structures designed as per recommended design parameters for this zone would generally prevent loss of human life and only repairable damage could occur. However, the recommended design parameters in IS: 1893 are for preliminary design of important structures and it is desirable to carry out dynamic analysis for final design of important hydraulic structures in order to estimate stresses and deformations in probable future earthquakes. IS code, therefore, recommends that for such structures detailed site specific investigations be carried out for estimating the design earthquake parameters. 1.3 The site specific studies related to the local and regional geological conditions, earthquake occurrences and seismotectonic set up of the region were carried out. The earthquake catalogue containing the location, time of occurrence and the size of earthquakes (provided by India Meteorological Department to the BEL project authorities) was made available to DEQ by the BEL and the same has been used for this study. Maximum Considered Earthquake (MCE) has been evaluated on the basis of above studies 1

260 using deterministic approach and the same is recommended for consideration in the design of structures. 1.4 Recommendations have been given in the form of smoothed design acceleration response spectra for different values of damping. A time history of strong ground motion and the acceleration spectra along with recommendations for consideration of vertical component of earthquake motion/spectra are also included. 2.0 REGIONAL GEOLOGY AND TECTONIC SETUP 2.1 The Nyamjang Chhu H.E. Project site on the Nyamjang Chhu river is located in the Lesser Himalayan region of Arunachal Pradesh and located 50 km north from the surface trace of MCT. Geologically, the project area is represented mainly by the quartzite-biotite gneiss rocks. Numerous tectonic features are present around the site and a 6 X 6 degree area bounded by latitudes N and N and longitudes E and E around the site (Fig. 1) has been considered for the study of regional geotectonic set up of the region. 2.2 The northern part of the study area is occupied by the Himalayas followed southward by the narrow Brahmaputra River basin/ Assam basin, covered by alluvial fill, and then by the Shield area i.e. Shillong Plateau. Whereas, the southeastern part of the area is occupied by the part of Indo-Burman fold belt. Small part of the Mishmi geotectonic unit occurs in the northeastern side of the study area. The Shillong Plateau is mainly represented by oldest Archean landmass with Precambrian deposits. The Extra Peninsular belt is mainly occupied by low grade complexes of the Lesser Himalaya tectonically reworked during the Himalayan Orogeny. The foothills Himalaya, south of the MBT exposes cover sequence of the frontal belt (Siwalik) affected by the terminal phase of Himalayan Orogeny. 2.3 The Himalayan mobile belt forms the main and prominent geotectonic block of the study area. The regional structural trend of the Eastern Himalayas is mostly E-W to ENE- WSW from Bhutan to the northeastern Arunachal Pradesh, which changes gradually to 2

261 NE-SW near the Siang valley and terminates against the Siang fracture (Nandy, 1976). This block is bordered by the Central Burmese Plate towards east. The prominent tectonic feature Indus-Tsangpo Suture Zone (ITSZ) separating the mobile belt from the Indus- Shyok Belt of the Tibetan Plateau defines its northern limit. Along ITSZ, the river Tsangpo (Brahmaputra) flows remarkably in an E-W rectilinear valley. The ITSZ marks the collision boundary of the Indian and Tibetan Plates. The Main Central Thrust (MCT) separates the rock units south of ITSZ, the highest-grade metamorphites and gneisses of the axial belt, from Precambrian sedimentary sequence and its equivalents. The Main Boundary Thrust (MBT) separates the Siwalik rocks from the pre-tertiary rocks. Beyond MBT, different stratigraphic units are disposed in intricate thrust slices. Since the rocks of this segment range in age from Proterozoic to Cenozoic, it has undergone different stages of crustal evolution and has been subjected to orogenic movements of varying intensity from time to time, the imprints of which are identifiable in different deformational structures, major unconformities or discontinuities (Kumar, 1997). 2.4 The northernmost tectonic feature of the study area is Indus Suture Zone (ISZ) trending E-W and marks the boundary between the Indian and Tibetan plates and south of this, litho-units of the main Himalayan belt are exposed. This zone is represented by the obducted materials of the Neotethyan oceanic crust together with deep marine Triassic to Eocene sediments. Main Central Thrust (MCT) is a regional tectonic feature that traverses the whole length of Himalayas has developed in response to intensive and extensive operative compressional tectonics. This feature is a north dipping thrust fault with initial steepness and marks the tectonic boundary between the high-grade metamorphites of the Se La Group and low to medium-grade metasediments of the Dirang Formation in the Diggin Valley, in upper reaches of the Kamla river and near Taliha in the Subansiri river section (Kumar,1997). Further in east, the Dirang Formation apears to get eliminated and it marks the tectonic boundary with the Bomdila Group. The MCT has been traced to Arunachal Pradesh through Nepal, Darjeeling-Sikkim and Bhutan (Ravi Shanker et al., 1989), which abuts against the Tidding Suture in the Siang Valley. 2.5 Main Boundary Thrust (MBT) is another regional tectonic feature of the Himalayas, which demarcates the tectonic boundary between the Main Himalayan Belt 3

262 and the Frontal Folded Belt forming the Sub-Himalayas. It is also a north dipping thrust fault with ENE-WSW trend from the border with Bhutan in the west to Roing in the Dibang valley and does not continue southeast to join the Mishmi Thrust as visualized by Ranga Rao (1983). According to Sinha Roy (1976) the MBT flattens at depth, as indicated by the absence of Gondwana rocks in southern Bhutan and in the west-central Arunachal Pradesh. This is possibly due to the fact that the MBT merges at depth with some dislocation zones in the inner belt. 2.6 In the region of foothills of the Arunachal Himalayas, south of MBT, a thick pile of molassic sub-greywacke representing the Siwaliks are exposed. This belt is continuous all along the Himalayan foothills from Kashmir to Arunachal Pradesh. The Siwalik sequence was deposited during the Mio-Pliocene in an unstable sinking basin, developed on the downward bending plate north of the Shillong Plateau and south of rising Himalayas. The Siwaliks, are folded and thrust over by the older rocks from the north along the MBT. The lithological assemblages of the Siwaliks were also controlled by the vigour of tectonism in the source area of the rising Himalaya. The Main Frontal Thrust (MFT) marks the southern fringe of the Siwalik belt, bordering the Brahmaputra basin. 2.7 Towards northeastern part of the study area the geotectonic block is represented by the Mishmi Hills which does not belong to the Indian plate and considered to be part of the Central Burmese Plate. This block comprises of metasediments, which had undergone four phases of deformation and had been intruded by granites/granodiorites and abuts against the Indian Plate along the Tidding Suture. The Mishmi Hills massif is comprised of diorite-granodiorite crystalline complex (Nandy, 1976) and the southwestern boundary of this is marked by high angle NW-SE trending Mishmi Thrust (MT) along which this block is thrust on the adjoining rocks. In this region, the NW-SE trending metamorphic belt is in direct contact with the Brahmaputra alluvium. This massif acts as a linkage between the Himalayan and Indo-Burman structural and stratigraphical trends in north and east respectively. 2.8 The region south and southwest of the above geotectonic blocks is occupied by the Brahmaputra River basin that has formed over the basement revealing some structural 4

263 features through geophysical surveys. The basement rocks are exposed to the west of the basin and the basement has northeastward slope which reaches up to a depth of 7 km near Mishmi foothills (GSI, 2000) as indicated by basement configuration. Whereas, near Guwahati the alluvial cover is only of the order of 0.34 km (Barooah and Bhattacharya, 1981) where the gneissic rocks of Shillong massif are exposed on surface as hills and ridges in the river channel and on both banks of the river. Similar hills and ridges are also exposed at the western most side of the Assam basin. In this part of the Assam basin the basement lays at shallower depth due to undersurface extension of the Shillong massif rocks. Here, the basement has been affected by various faults, highs and lows, upwarps and downwarps as revealed by seismic survey in the upper Assam (Barooah and Bhattacharya, 1981). Most of these basement faults trend NE-SW but some are having E- W trends. The most striking fault of the Brahmaputra river basin is the NW-SE trending Dhansiri-Kopili fault which runs between the Shillong and Mikir Hills Massifs in the Kopili Gap and extends across the Brahmaputra River. In this region the morphology of the basement is represented by bowl shaped basin with thickest sediments in the area north of Nowgang (Nandy, 2001). 2.9 This Brahmaputra Basin is bordered by the Archean landmass, the Shillong Plateau towards south. It is interesting to note that the Shillong Plateau has witnessed prolonged crustal deformation since Archean time. The E-W trending Dauki Fault (DF) forming steep scarps is a very prominent linear feature marking the southern edge of the Shillong Massif. The basement rocks of the Shillong Plateau had faulted downward along the DF for around 13 km. In Bangladesh, the basement rock is overlain by thick sediments. This neighbouring part of Bangladesh also has suffered intense earth movements The Shillong Plateau is comprised of the Shillong Massif (SM) and Mikir Hills Massif (MHM). The MHM is separated from the SM by an alluvial tract, which is located in the central part of Northeast India. A large part of the shield area of Northeast India exposes Archean folds. These zones show schistose tracts grading into vast stretches of granitic gneisses incorporating metasedimentary and metavolcanic rocks within the gneissic complex. A major part of this complex has apparently been formed by 5

264 metasomatism of these sediments and volcanics. Intrusive augen gneisses occur within the Archean and these could possibly mark late-tectonic magmatic episodes of older orogenies (Mazumdar, 1978) The Archean rocks of the Shillong plateau have been subjected to polycyclic folding and metamorphism. The Shillong Group was deposited in central parts of the plateau, as this area developed into a trough. The post-precambrian landmass experienced peneplanation till Jurassic, resulting into the formation of a flat-leveled surface, which is preserved over the plateau till today (G.S.I., 1974). The MHM, with an average elevation of 1,000 m, represents a peneplaned surface of predominantly gneissic rocks. The sedimentary rocks are exposed along the southern and eastern flanks By the end of Jurassic, the southern margin of the Shillong Plateau experienced eruption of Sylhet Traps through E-W trending fissures (Murthy, 1970; G.S.I., 1974). Around 150 Ma, carbonatite complex was emplaced along an N-S trending fault in the eastern part of the Shillong massif (Sarkar et al., 1992). The Cretaceous sediments got deposited along the subsiding southern block. Towards the Paleocene-Eocene, the plateau attained a stable shelf condition due to lower subsidence rate. The eastern and western parts of the Shillong massif remained landmass till mid-eocene and experienced progressive down-sinking which initiated the deposition of coal-bearing sandstone (G.S.I., 1974) Shillong Plateau represents a unique structural unit in the area, as it is blockuplifted to its present height (Murthy, 1970; G.S.I., 1974). The southern margin of Shillong Plateau is marked by the remarkably linear E-W trending Dauki Fault. Evans (1964) gave detailed geological and tectonic set up along the Dauki Fault Zone and suggested that this zone is essentially a tear-fault with a lateral movement of over 200 km. Even though presence of slickensides on a fault surface shows horizontal E-W movement, extent of movement was not possible to be estimated. Similarly, due to lack of evidences on the extension of this zone below the alluvial gap between Shillong Plateau and 6

265 Rajmahal Hills, its westward continuation can not be ascertained. Later, Murthy (1970), Desikachar (1974) and G.S.I. (1974) have suggested vertical movements along the Dauki Fault, as it is evidenced by the extrusion of lava through the deep-seated vertical fracture system. Also, Murthy (1970) has reported evidences to indicate activity along a number of E-W, N-S and NW-SE basement faults throughout the Tertiary period. It seems that the fault zone is characterized by uplift and down-sinking of adjacent basement blocks along the fractures In the western part of the Shillong Massif, NW-SE trending high-angle Dapsi Reverse Fault upthrust the Tura range southward. This fault forms the boundary between the Precambrians in the north and Tertiary rocks in the south. The depositional sequence was affected by this reverse fault, which probably demarcated the northern boundary of the sedimentary basin from Mid-Eocene through Miocene (Murthy, 1970). The Shillong Plateau shows a criss-cross fracture pattern and marked by sharp and prominent Dudhnoi and Kulsi faults affecting the ancient basement. Further the basement is also affected by NE-SW trending Barapani Shear zone. Towards west, the Shillong Plateau is bordered by the N-S trending Jamuna/ Dhubri Fault, which is indicated by the difference in basement levels and linear north-south Brahmaputra River course for about 150 km to 200 km. The eastern part of the Shillong Massif is marked by the NW-SE trending Dhansiri-Kopili Fault. This fault separates the SM from MHM, which may be connected with each other at depth. A graben-type of structure is responsible for the down-sinking of this region Whereas, in the southeastern part of the study area part of the Indo-Burman tectonic belt occurs which has a regional N-S trending arc of mountain ridges extending from Mishmi Hills through the Patkai, Naga, Chin and Arakan-Yoma Hills and is genetically linked with the Andaman-Nicobar ridge and Sunda belt. Very prominent eastward dipping Eastern Boundary Thrust delimits this mobile belt from the Central Myanmar basin (Nandy, 2001). The Indo-Burman tectonic belt has formed due to subduction of the Indian Plate beneath the Burmese Plate in geological past Geologically, the hill ranges of this tectonic belt are mainly formed of thick 7

266 turbiditic Cretaceous to upper Eocene shales and sandstones (Brunnschweiler, 1966). This belt has been folded more intricately in Nagaland and the NE-SW trending Naga Thrust traverses the whole of Nagaland and then verges with the Dauki Fault after taking a swing towards southwest to west near Haflong. The anticlines, close to the Naga Thrust, show reversal in topography with anticlines forming sites of valleys and synclinal hills (Nandy, 2001). These anticlines appear like upwarps on the edge of the moving Naga slice with gently eastern limbs and steep, much sheared western limbs. Remarkably, most of the thrusts in the region of Belt of Schuppen diverge from northwest and then unite with the Naga Thrust. Thrust shows successive increase in magnitude of overriding movement towards north. This zone has undergone large dislocation, as is indicated by enormous variation in lithotectonic associations and attributes on either side of the Naga Thrust The belt of Schuppen in the Naga hills is a narrow linear belt of imbricate thrust slices adjacent to the Assam valley and runs for 350 km (Mathur and Evans, 1964). This belt comprises eight or possibly more overthrusts along which Paleogene rocks of Indo- Myanmar mobile belt have moved northwestward. These thrusts define various lithotectonic blocks and the thrusts have monoclinal dip towards southeast. As a result of large scale thrusting in the schuppen belt the total horizontal movement that occurred is estimated to be over 200 km (Nandy, 2001) Towards south in the state of Mizoram and Tripura, the folded belt is represented by high anticlinal ridges and synclinal valleys of Surmas and Tipams (Miocene) having major N-S trending strike faults. The Oligocene rocks (Barail) consist of a series of N-S trending marginal to basin faults. The intensity of fold movements and amplitudes of folded layers are higher in the eastern part than in the western part of the basin. In the Tripura and adjacent Bangladesh area, the folds are characterized by compressed anticlines alternating with broad, very gently depressed synclines which, becomes more compressed towards east. The Plio-Pleistocene beds in Bangladesh plains just west of Tripura folded belt are also affected due to folding. Both anticlines and synclines are traversed by sub-parallel and sub-vertical regional strike faults adjacent to the crestal region of the folds. One of the significant tectonic features of this region however, is the region of Barak-Surma valley which is bounded by hills on three sides with opening to the 8

267 plains of Bangladesh through Sylhet. The valley appears to have affected by tearing and the valley trend coincides with the well known Sylhet fault. The prominent Sylhet Fault has long been recognized in this region which trends NE and truncates the N-S trending fold belt of Bangaldesh and Tripura region. These fold ridges exhibit eastward dragging affect along this fault, as these folds take eastward swing. This fault extends for about 140 km and the Kusiyara River flows along this lineament for 35 km. Study of a 1968 earthquake indicated thrust faulting along this feature (Tandon and Srivastava, 1975). However, Dasgupta and Nandy (1982) suggested deep-seated high angle reverse fault, having a dip of about 700 towards southeast along this lineament To the south of the Dauki Fault of the Shillong Plateau, the plains of Bangladesh are covered by enormously thick alluvium. The Bengal Basin is bordered on its west by the Precambrian basement complex of crystalline metamorphics of the Indian Shield and to the east by the frontal folds of Tripura. The basement below the basin is marked by the Hinge zone, a high and a trough. Differential thickening and subsidence of the overlying Oligo-Miocene sections between the shelf on the northwest and deeper basin to the southeast has occurred in the region of EHZ. The Bengal basin basement steeply plunges from 4 to 10 km or even further across the EHZ (Mukhopadhyay and Dasgupta, 1988). This extends for at least 500 km from the Dauki fault on the north and Kolkata on the south with probable extension into the Bay of Bengal having varying width from 25 km in the north to 110 km in the central part and 35 km in the south. 3.0 SITE GEOLOGY 3.1 The geology of the project site is represented by quartz-biotite gneiss (QBG) belonging to Precambrian Sela Group towards upstream and an interbedded sequence of quartzite (IQS) and schist of Precambrian Lumla/Rupa Group towards downstream. The QBG is a fairly uniform, medium to coarse grained, well foliated rock. It shows gneissose texture with alternate bands of mainly quartz feldspar and micas aong with accessories. The IQS are 10m to over 40m thick and are associated with thin interbands of grey quartzite. Occasionally, thin bands of carbonaceous schist and calcitic marble also occur. 9

268 A limited occurrence of granitic gneiss is also found. 3.2 At the barrage site, the river is flat and very wide up to 200m. River bed exposes black fine silty sand with high content of micaceous minerals. Boulders composed mostly of quartzite and gneiss and ranging in size from a few centimeter to a few meters are seen in the river bed area. Gneissic rocks are best exposed on the right bank. On the left bank, gneisses are exposed only along the deeply incised nallas. River bed bore hole (98m deep) information indicate presence of overburden consisting of boulders of biotite, gneisses with quartz content and blackish medium to fine silty sand up to a depth of 7.5m and followed by only sand without boulder up to a depth of 91.5m. Rocks consisting of biotite gneisses with quartz content have been encountered after the depth of 91.5m. Whereas, in the other bore hole in river bed rock were encountered at a depth of 49m overlain by blackish medium to fine silty sand and then boulders. 10

269 Fig.1 Seismotectonic around the Nyamjang Chhu HE project site. ISZ-Indus Suture Zone, MCT- Main Central Thrust, MT-Mishmi Thrust, LT-Lohit Thrust, BFT-Bame Tuting Fault, MBT-Main Boundary Thrust, MFT-Main Frontal Thrust, AF-Atherkheit Fault, DF-Dhubri Fault, DKF-Dhansiri Kopili Fault, KS-Kalyani Shear, BS-Barapani Shear, NT-Naga Thrust, DT-Disang Thrust, EBT-Eastern Boundary Fault, DFZ-Dauki Fault. 11

270 4.0 EARTHQUAKE OCCURRENCES 4.1 The Nyamjang Chhu H.E. Project site situated in Tawang district of Arunachal Pradesh and lies in seismic zone V as per the seismic zoning map of India as incorporated in Indian Standard Criteria for Earthquake Resistant Design of Structures IS:1893-(Part I) 2002: General Provisions and Buildings. Many earthquakes, having large to great size, have occurred in this region as per historical and instrumental earthquake data ( ) provided India Meteorological Department (IMD) and given in Appendix-I. There are 733 earthquakes that have occurred around the site in 6 x 6 area out of which there are 55 earthquakes with unassigned magnitude. However, there are 16, 121, 378, 139, 6 and one earthquakes reported in the magnitude ranges , , , , , and M > 8.0, respectively. 4.2 Figure 1 shows the epicentral map along with the tectonic features in the area. The analysis of epicentral map shows that the occurred earthquakes around the site are mostly associated with the tectonic features such as the Main Central Thrust, Main Boundary Thrust, Mishmi Thrust and the Shillong plateau region. Shillong plateau earthquake of June 12, 1897 (M=8.7), Dhubri earthquake of July 3, 1930 (M=7.1) and Arunachal Pradesh - China Border earthquake of August 15, 1950 (M=8.5) are the prominent earthquakes experienced by this region. 4.3 The Shillong plateau earthquake of June 12, 1897 had its epicentral tract in and around Shillong where there was considerable damage to lives and property, in addition to other effects of very strong ground shaking. The maximum seismic intensity experienced in the region due to the Shillong plateau earthquake of 1897 was estimated to be X on MMI. According to an estimate it took a toll of 1542 human lives and almost complete destruction of all brick and stone buildings in all the principal towns of northeast Indian region including Shillong, Sylhet, Goalpara, Guwahati, Dhubri and Tura. The destruction spread over an area of 3,71,200 sq km and the shock was felt over an area of 4.48 million sq km. The intensity of the shaking within the epicentral tract was so large that visible waves were seen at a number of places viz. Shillong, Nalban, Magaldai. On the slopes of the Khasi hills a number of embedded rounded small blocks of granite were 12

271 thrown out of their places, showing that at these places the vertical acceleration exceeded that of gravity, at least momentarily. Landslides occurred on enormous scale in the hills and soft ground was filled with fissures throughout the epicentral tract. The earthquake caused visible movements along faults besides fracturing long stretches of rock. In a number of places the streambeds were tilted resulting in changing their course. Even the bed of the Brahamputra river was affected, resulting in unprecedented floods in the second half of the year The earthquake was followed by a very large number of aftershocks whose epicenters were apparently scattered over a large area. 4.4 The Arunachal Pradesh China Border earthquake of August 15, 1950 was the largest earthquake to have occurred in the past five decades in India. The epicenter lay close to the junction of the borders of India, Burma and Tibet. The level of river Lohit and all the other streams had risen. Landslides on all the mountains enclosing the basin, has been on a very extensive scale and wide belts had been ripped off their vegetation, which fell into the valleys. Although the epicenter of the earthquake was located in the unpopulated part, just outside the north east boundary of India, it caused great destruction to property in north- eastern Assam particularly in the sub-division of North Lakhimpur, Dibrugarh, Jorhat, Sibsagar and Arunachal Pradesh. Road and rail communications in the affected areas got completely disrupted, due to ground subsidence and enormous fissures. The bed of the Brahmaputra rose giving rise to floods in the valley. An area of nearly sq km in Assam suffered extensive heavy damage, The shock was felt up to Lucknow, Allahabad, Rangoon and the total felt area therefore must have exceeded 2.9 million sq km. Numerous aftershocks followed the main earthquake, their epicenters scattered over a large area. The largest magnitude of the aftershock was An earthquake of moderate intensity (M=6.6) occurred on August 6, 1988 in Manipur-Burma border region. This earthquake was widely felt in all the Northeastern states including Arunachal Pradesh, Bangladesh, parts of North Western Burma and Kathmandu (Nepal). Due to this earthquake, three people were killed, 12 injured and considerable damage and landslides were noticed in the Guwahati - Sibsagar - Imphal area. Subsidence of about 20 centimeters occurred in the Guwahati area. About 30 people injured and some damage in Bangladesh was reported. Some damage in adjoining area of 13

272 Burma was also reported. The earthquake was followed by a number of aftershocks. 5.0 PARAMETERS FOR EARTHQUAKE RESISTANT DESIGN 5.1 Definitions Maximum Considered Earthquake (MCE) The Maximum Considered Earthquake is defined as the earthquake that can cause the most severe ground motion capable of being produced at the site under the currently known seismotectonic framework. It is a rational and believable event, which can be supported by all known geological and seismological data. It is determined by judgment based on maximum earthquake that a tectonic region can produce considering the geological evidence on past movement and the recorded seismic history of the area Design Basis Earthquake (DBE) The Design Basis Earthquake is defined as that earthquake which can reasonably be expected to occur during the economic life of the structure (say 100 years) and in the event of exposure to earthquake hazards it will not cause loss of life and the structure will undergo permissible deformations and repairable damage such that the structure, equipment facilities and services will remain functional after the earthquake. As design criteria the resulting ground accelerations at the site under DBE may be taken as a fraction of MCE based on engineering judgment for adopted design methodology. 5.2 Seismogenic Sources around the Site This project site falls in the easternmost part of the Himalayan orogenic belt close to the regional tectonic feature MCT. In order to evaluate earthquake hazard for the Nyamjang Chhu H.E. project site, various important earthquake sources around the site have been considered. To explain the cause of occurrence of earthquakes and to understand the seismotectonics of the Himalayan collision zone, various models have been proposed for the evolution of the Himalaya. Of these, two models namely, Steady State Model and the Evolutionary model have gained considerable importance. 14

273 5.2.2 Steady state model (Seeber et al., 1981) postulates that the active low angle contemporary thrusts i.e. MCT and MBT converge with the plane of detachment, which marks the interface between the subducting Indian slab and overlying sedimentary wedge. Whereas, the basement thrust in this model represents that part of shallow dipping detachment surface where the MCT merges and hence spatially the basement thrust is located just north of MCT. According to this model the great Himalayan earthquakes are related to the detachment surface. The evolutionary model (Ni and Barazangi 1984) postulates that zone of plate convergence has progressively shifted south by formation of intra crustal thrusts and hypothesizes that the MBT is the most active tectonic surface and that the seismicity is concentrated in a 50 km wide zone between the map trace of MBT and MCT. This model suggests that the rupture of Great Himalayan earthquakes may have started in the interplate thrust zone, which propagated south along the detachment to the MBT and further south to the subsidiary blind thrusts making MBT the most active thrust rooted in the detachment. Both these models suggest that the contemporary deformation styles in the Himalayas are guided by the under thrusting of the Indian thrust along the detachment surface Nearest seismogenic sources to the site are Main Central Thrust and Main Boundary Thrust. The project area is seismically active as several earthquakes are reported from this region The NE-SW trending Main Central Thrust (MCT) in this part of the Himalayas is a north dipping thrust with initial steepness and marks the tectonic boundary between the high-grade metamorphites of the Se La Group and low to medium-grade metasediments of the Dirang Formation in the Diggin Valley, in upper reaches of the Kamla river and near Taliha in the Subansiri river section. Further in east, the Dirang Formation appears to get eliminated and it marks the tectonic boundary with the Bomdila Group. The MCT has been traced to Arunachal Pradesh through Nepal, Darjeeling-Sikkim and Bhutan (Ravi Shanker et al., 1989), which abuts against the Tidding Suture in the Siang Valley. A magnitude 8.0 has been assigned to this regional feature for the assessment of seismic hazard using deterministic approach. 15

274 5.2.5 The Main Boundary Thrust (MBT) and other north trending thrusts dip towards the project site and hence the thrust plane lies beneath the project site. MBT demarcates the tectonic boundary between the Main Himalayan Belt and the Frontal Folded Belt forming the Sub-Himalayas. The Lesser Himalayan meta-sedimentaries have been brought over the Sub Himalayan successions through large-scale movement that took place along the MBT. The MBT is not a single tectonic plane instead is represented by several thrust slices. It is also a north dipping thrust fault with ENE-WSW trend from the border with Bhutan in the west to Roing in the Dibang valley and does not continue southeast to join the Mishmi Thrust as visualized by Ranga Rao (1983). According to Sinha Roy (1976) the MBT flattens at depth, as indicated by the absence of Gondwana rocks in southern Bhutan and in the west-central Arunachal Pradesh. This is possibly due to the fact that the MBT merges at depth with some dislocation zones in the inner belt. To the seismogenic source earthquake of magnitude 7.5 has been assigned. Table I - Peak ground horizontal acceleration from various sources around Hutong- II H.E Project Site Sl. No. Sources Magnitude Distance to zone of energy release(km) Max. Accl. (g) 1. Main Central Thrust Main Boundary Thrust Lineament L Indus Suture Zone Atherkheit Fault Dhansiri Kopili Fault Barapani Shear Dhubri Fault Dauki Fault Zone Naga / Disang Thrust Shillong Plateau Earthquake Source

275 5.3 Estimation of Maximum Considered Earthquake (MCE) Earthquake Parameters Based on the regional geology along with the seismotectonics as described in sections 2.0 to 4.0 the parameters for maximum probable earthquakes which can be generated from the potential seismogenic sources around the site are given in Table I, wherein eleven such sources have been considered for deterministic analysis. The peak ground horizontal acceleration estimates are made using empirical formulae worked out by some of the research workers for various tectonic environment. Attenuation relationships are derived by regression analysis using different distance measures and magnitude measures. Thus different relationships provide different estimates of probable ground acceleration and a judicious decision to estimate ground acceleration is therefore required for adoption in any particular situation ICOLD Bulletin 72 (1989) recommends use of some empirical relationships like that of Campbell (1981) and Joyner and Boore (1981). Subsequently, Abrahamson and Litehiser (1989) using formulation similar to the above have made comprehensive recommendations based on analysis of 585 records from 76 world wide earthquakes. For the present study attenuation relationship proposed by Abrahamson and Litehiser (1989) has been used. The regression used a two-step procedure that is hybrid of the Joyner and Boore (1981) and Campbell (1981) regression methods. The horizontal acceleration attenuation relation is as follows: 0.284M log( a) = M log( r + e ) F Er -(1) where, a is peak horizontal acceleration, r is the closest distance (in km) from site to the zone of energy release, M is the magnitude ( M L < 6.0 and Ms > 6.0) following Campbell (1981) where Ms is used if it is greater than or equal to 6., F is dummy variable that is 1 for reverse or reverse oblique fault otherwise 0, and E is a dummy variable that is 1 for inter-plate and 0 for intra-plate events. The rupture width is estimated using Wells and Coppersmith, (1994) relationship log( RW ) = M -(2) 17

276 where RW is the rupture width. In case the rupture width is less than the general focal depths of the region ( FD ) then the depth to the zone of energy release is estimated as Dz RW = NSD + ( FD sin α ) -(3) 2 where NSD is non seismogenic depth and α is the dip angle. When the rupture width is more than FD the depth to the zone of energy release is estimated as RW Dz = NSD + sinα -(4) 2 The distance to the zone of energy release De is estimated using the depth to the zone of energy release Dz and the epicentral distance Ep as 2 2 De = Ep + Dz -(5) If the site is on hanging wall of the thrust type of seismogenic feature, the epicentral distance is considered as zero and the distance to the zone of energy release is taken as depth to the zone of energy release i.e., Dz. The angle α is taken as 15 for the thrust type of seismogenic features which are necessarily the low angle reverse faults. In case of normal/strike slip the angle α is taken as 90. The estimation of the general depth of focus in this region is made using the cross section of the line AB across the main seismogenic features such as the trends of MCT and MBT. The line on which the earthquakes are projected is given in Fig. 2. The depth section is shown in Fig. 3. The depth section reveals the general depth around 15 km. The trend of the data could not be interpreted in terms of the detachment surface present in the region due to lesser number of data available and the errors in the depths of the located events as given in section 5.2 of the report. Conservatively, the models as proposed for the orogeny of these seismogenic features (as reported in section 5.2) have been considered and a depth of 15 km is assigned for general focal depth in the area as per the models. The relationship given by Wells and Coppersmith (1994) uses the moment magnitude which is approximately equal to surface wave magnitude in the range of (Kanamori, 1983). Therefore, the same magnitudes are used to compute the rupture width. 18

277 The magnitudes are assigned to the seismic sources based on the past seismicity associated with the individual seismogenic features. The maximum value estimated for horizontal peak ground acceleration (PGA) is 0.42g (Table I). The surface wave magnitude Ms is used for the estimation of PGA values Ground Motion Characteristics Time history of ground motion is worked out from the shape of target acceleration response spectra, which in turn depends on the parameters of the earthquake, the predominant period of the ground motion, and the amplification of spectral acceleration at various periods. Shape of design response spectrum is based on subjective judgment of local geology and bed rock conditions. For the present situation the maximum amplification is taken as corresponding to 5% damping. This amplification corresponds to the mean level. The history of ground motion (accelerogram) has been generated for these parameters. Figure 4 shows the accelerogram with normalised peak ground acceleration of 1.0 g. Appendix-II gives listing of acceleration ordinates at intervals of 0.01 sec. corresponding to ground acceleration time history (normalised to 1.0 g) in horizontal direction. The ordinates of Fig. 4 and acceleration ordinates in Appendix- II will have to be multiplied by 0.42 g to obtain MCE time history. 19

278 Fig. 2 Seismicity map of the region around Nyamjang Chhu HE project showing the line AB considered to plot the depth section as given in Fig. 3. Fig.3 Depth section across the seismogenic features around Nyamjang Chhu HE project site for line AB as given in Fig