KHC Lethang Hydro Project Private Limited Draft CEIA Report for 96 MW Lethang Hydro Electric Project , West Sikkim District, Sikkim Asian Consulting Engineers Pvt. Ltd., New Delhi June 2010 Draft CEIA Report for 96 MW Lethang Hydro Electric Project, West Sikkim District, Sikkim TABLE OF CONTENTS EXECUTIVE SUMMARY CHAPTER-1: INTRODUCTION 1.0 Hydropower Potential in Sikkim……………..…...................... ......................... 1-1 1.1 Lethang Hydro Power Project………………....................... .... …..…… …….... 1-2 1.2 Identification of the Project............................................... ........................................ 1-2 1.3 Project Proponent……….……… .....................… ……………………………… 1-2 1.4 DPR Consultants & EIA Consultants.......................................................................... 1-3 1.5 Purpose of EIA Study ………….. …………….….................................................... 1-3 1.6 Policy & Legal Framework…………………………..………………………………. 1-3 1.7 Scope of EIA Study………………………………………………………………… 1-4 1.8 Approach & Methodology of EIA Study……………………………………………. 1-6 1.8.1 Approach of the EIA Study ….. ……………………...………................... 1-6 1.8.2 Establishment of Baseline Environmental Status ….. .…...…..................... 1-6 1.8.3 Field study/Monitoring for Generation of primary Data.............................. 1-6 1.8.4 Environmental Impact Assessment...…………………………….......……. 1-7 1.8.5 Preparation of Environmental Management Plan…………….….......……. 1-7 1.9 Structure of the EIA Report…………………….…………… .................................. 1-8 CHAPTER-2: PROJECT DESCRIPTION 2.1 Project Overview ……………………………………….…..…..................... 2-1 2.2 Justification for location & execution of the project in relation to structural components………………………………………………………………… 2-2 2.3 Salient Features of Lethang Hydro Power Project……………………….. 2-3 2.4 Project Description……………………………………………… 2-7 2.5 Lethang HEP Project Cost…………………………………………………………. 2-9 2. 5.1 Civil Engineering Structures ………………. ………........................…… 2-9 2.5.2 Brief Description of Civil Engineering 2-9 Components..........……………….................. 2.5.2.1 Barrage…………..……………………………..................…… 2-9 2.5.2.2 Fish Ladder.....................……..................................................... 2-9 2.5.2.3 Intake Structure ……………………………………………… 2-10 2.5.2.4 Desilting Basins .................…………..……………..………… 2-10 2.5.2.5 Head Race Tunnel………………………………....…………. 2-10 2.5.2.6 Adits.............……………………………...………………….. 2-10 2.5.2.7 Surge Shaft……………….......………………………………. 2-10 2.5.2.8 Pressure Shaft & Valve Chamber….......…………………….. 2-10 2.5.2.9 Power House………………....………………………………. 2-10 2.5.2.10 Transformer Cavern……… ………………………………….. 2-11 2.5.2.11 Tail Race Structure…………………………………………... 2-11 2.5.2.12 Pot Head Yard………………………………………………... 2-11 2.6 Electro Mechanical Works & Transmission…....................……….......................… 2-11 2. 6.1 Hydraulic Turbine...……………………………………………….............… 2-11 2.6.2 Generator.......... ………..………………………………………….............… 2-11 ________________________________________________________________________ Asian Consulting Engineers Pvt. Ltd. i Draft CEIA Report for 96 MW Lethang Hydro Electric Project, West Sikkim District, Sikkim 2.6.3 Transmission Line…………………………………………………………… 2-11 2.6.4 Control and Protection. ……………………………………………............... 2-12 2.6.5 D.C. Equipments......................………………………………………............ 2-12 2.6.6 Mechanical Auxiliaries………....…...........…………………………………. 2-12 2.6.7 Station Grounding System.......……………………………… ……...........… 2-13 2.7 Infrastructure Facilities........................……................................................................ 2-13 2. 7.1 Access Roads.……………............................................................................ 2-13 2.7.2 Project Colonies……………………...........……………………………….. 2-16 2.7.3 Construction Facilities and Dumping Areas……………………………….. 2-18 2.7.4 Power Requirement…………………………………………………………. 2-18 2.7.5 Telephone Facilities……………………………………………………….. 2-18 2.8 Land Acquisition ……………………………….......................……………………. 2-18 2.9 Construction Material………………………………………………......................... 2-19 2.10 Muck Generation and Disposal…………………………………………………….. 2-20 2.11 Construction Methodology & Schedule……………………………………………. 2-21 2.11.1 Main Construction Methodology ………………………………….. 2-21 2.12 Summary of Total Project Costs………………………………………………….. 2-23 CHAPTER-3: THE EXISTING ENVIRONMENT 3.1 Introduction......................................................……………………………………... 3-1 3.1.1 Project Components and the Site…………………………………….. 3-1 3.1.2 Study are…………….……………………………………………............. 3-1 3.1.3 Sampling Location………………………………………………............... 3-1 3.2 Land Environment…………………………………………………………………. 3-4 3.2.1 Physiography…………………………………………………………….. 3-4 3.2.2 Geology ………………………………………………………………….. 3-8 3.2.2.1 Project Area Geology …………………………………………… 3-8 3.2.3 Seismic ity……………………………………………………………….. 3-12 3.2.3.1 Possible Seismic Source and Peak Ground Acceleration... 3-14 3.2.4 Landslide Zonation…………………………………………………. 3-18 3.2.5 Soil Characterization (Physico-Chemical)………………………………. 3-21 3.2.6 Land Use…………………………………………………………… 3-23 3.2.6.1 Landuse/Land cover Study……………………………….. 3-24 3.2.6.2 Land Requirement for the Project ………………………. 3-28 3.3 Climate and Meteorology ………………………………………………………… 3-28 3.3.1 Climate…………………………………………………………………… 3-28 3.3.2 Meteorology………………………………………………………………. 3-29 3.3.3 Cloud Cover ………………………………………………………………. 3-30 3.3.4 Snow Cover………………………………………………………………... 3-30 3.3.5 Cloud Burst ……………………………………………………………… 3-30 3.4 Air Environment……………………………………………………………………. 3-32 3.4.1 Ambient Air Quality ………………………………………………………. 3-32 3.4.1.1 Ambient Air Monitoring ………………………………………... 3-32 3.4.1.2 Air Monitoring Results …………………………………………. 3-32 3.4.2 Traffic Density …………………………………………………………….. 3-33 3.5 Noise Environment………………………………………………………………….. 3-35 3.6 Water Environment ……………………………………………………………… 3-36 ________________________________________________________________________ Asian Consulting Engineers Pvt. Ltd. ii Draft CEIA Report for 96 MW Lethang Hydro Electric Project, West Sikkim District, Sikkim 3.6.1 Hydrology ………………………………………………………………… 3-36 3.6.2 Precipitation Characteristics……………………………………………… 3-37 3.6.3 Inflow at Diversion Site……………………………………………………. 3-37 3.6.3.1 Hydro Meteorology Approach………………………………….. 3-42 3.6.4 Flood Hydrograph…………………………………………………………. 3-43 3.6.4.1 Flood Recurrence Interval………………………………………. 3-44 3.6.4.2 Frequency Analysis……………………………………………… 3-44 3.6.4.3 Frequency Analysis Comparison of Frequency Analysis and 3-44 Hydro–Meteorology Approach………………………………… 3.6.4.4 Design Flood for River Diversion Work………………………. 3-45 3.6.4.5 Sedimentation…………………………………………………… 3-45 3.7 Water Environment…………………………………………………………………. 3-46 3.7.1 Surface Water bodies……………………………………………………… 3-46 3.7.2 Water Quality Monitoring………………………………………………… 3-46 3.7.2.1 Surface Water Quality………………………………………….. 3-47 3.7.2.2 Drinking Water Quality………………………………………… 3-49 3.8 Biotic Environment ………………………………………………………………... 3-51 3.8.1 Terrestrial Ecology………………………………………………………… 3-51 3.8.1.1 Flora ……………………………………………………………… 3-51 3.8.1.2 Fauna ……………………………………………………………. 3-67 3.8.1.3 Eco Sensitive Areas …………………………………………….. 3-70 3.8.2 Aquatic Ecology ………………………………………………………….. 3-72 3.8.2.1 Fish Fauna ………………………………………………………. 3-72 3.8.2.2 Benthos and Planktons ………………………………………….. 3-77 3.9 Socio-Economic Environment................................................................................ 3-81 3.9.1 Land Holding Details and Project Affected Families……………………… 3-81 3.9.2 Survey Area and Population Covered…………………………………… 3-81 3.10 Socio - Economic Profile of Villages………………………………………………... 3-84 3.11 Religion …………………………………………………………………………… 3-85 3.12 Social Stratification…………………………………………………………………. 3-85 3.13 Family Type and Size……………………………………………………………….. 3-86 3.14 Literacy Level ……………………………………………………………………… 3-86 3.14.1 Economic Status …………………………………………………… 3-87 3.14.2 Occupation Details………………………………………………………… 3-88 3.14.3 Annual Income ……………………………………………………………. 3-89 3.14.4 Schemes for Livelihood Promotion………………………………………… 3-90 3.15 Archaeological Monuments, Religious Structure and Sacred Lakes………… 3-90 CHAPTER-4: ASSESSMENT OF IMPACTS 4.1 Assessment of Impacts on the Environment …………………………………….…. 4-1 4.2 Identification of Interactions ……………………………………………………...... 4-2 4.3 The Major Activities that may have Impact on Environment ……………………… 4-3 4.4 Impacts on Ecology………………………………………………………………… 4-8 4.4.1 Terrestrial Flora …………………………………………………………… 4-8 4.4.1.1 Loss of Green Cover.......................................................................... 4-8 4.4.1.2 Increased Human Interference……………………………………… 4-9 4.4.2 Terrestrial Fauna ............................................................................................. 4-9 ________________________________________________________________________ Asian Consulting Engineers Pvt. Ltd. iii Draft CEIA Report for 96 MW Lethang Hydro Electric Project, West Sikkim District, Sikkim 4.4.2.1 Disturbance to Wildlife……………………………………………… 4-9 4.5 Noise and Vibration………………………………………………………………….. 4-11 4.6 Air Environment.............................................................................................. 4-11 4.7 Water Environment.......................................................................................... 4-12 4.8 Socio-Economic Environment........................................................................... 4-13 CHAPTER-5: ENVIRONMENTAL