TRISHULI JAL VIDHYUT COMPANY LIMITED UPPER TRISHULI 3B HYDROELECTRIC PROJECT (42 MW) Powerhouse Site Volume II Detail Project Report Prepared by: Trishuli Jal Vidhyut Company Limited Sohrakhutte, Kathmandu Ph : 4363681, Fax No. 4363681, P.O Box 6464 Date: October 2013 Detail Project Report of UT3B HEP Content of Reports, Drawings and Appendix Volume 1: Executive Summary Volume 2: Detail Project Report Volume 3: Drawings ( Detail Project Report) Volume 4: Drawing of Structural Design Appendix A: Topographic Survey and Cadastral Mapping Appendix B: Hydrology Appendix C: Geological Study Appendix D: Hydraulic Design Appendix E: Rate Analysis Appendix F: Cost Estimate Appendix G: Structure Design Report Engineering Study and Design Team: S.N Name and Designation Signature 1 Er. Damodar Bhakta Shrestha (CEO) 2 Er. Bishow Kumar Shrestha (Structural Engineer) 3 Er. Sunil Basnet (Hydropower Engineer) 4 Er. Deepak Pandey (Contract Engineer) 5 Er. Rajesh Sharma (Civil Engineer) 6 Er. Kalyan Khanal (Civil Engineer) Trishuli Jal Vidhyut Company Limited Detail Project Report of UT3B HEP Table of Content Chapter 1 Introduction 1.1 Study Background ........................................................................................................................... 1-1 1.2 Previous Studies ............................................................................................................................... 1-2 1.3 Objectives and Scope of Work ...................................................................................................... 1-2 1.4 Field Investigation Works ............................................................................................................... 1-3 1.4.1 Topographical Survey and Mapping ...................................................................................... 1-3 1.4.2 Geological and Geotechnical Investigation ........................................................................... 1-3 1.4.3 Project supports facilities ......................................................................................................... 1-4 1.5 Design Work ..................................................................................................................................... 1-4 Chapter 2 Description of Project Area 2.1 Location ............................................................................................................................................ 2-1 2.2 Physical Features ............................................................................................................................. 2-2 2.3 Accessibility ...................................................................................................................................... 2-3 Chapter 3 Field Investigation and Data Collection 3.1 Topographic Survey and Mapping ............................................................................................... 3-1 3.1.1 Previous Study ........................................................................................................................... 3-1 3.1.2 Additional Topographic Mapping and Survey, Fiscal Year-2013 ....................................... 3-1 3.1.3 Scope of works ....................................................................................................................... 3-1 3.1.4 Monumentation of Ground Control Points and Benchmarks ........................................ 3-3 3.1.5 Detail Topographical Survey ................................................................................................ 3-4 3.1.6 Cross- Section Survey ............................................................................................................ 3-4 3.1.8 Location of Bore Holes, Test Pits and Resistivity Line ..................................................... 3-6 3.2 Hydrological Investigations ........................................................................................................... 3-7 3.2.1 Collection of Available Meteorological and Hydrological Data ...................................... 3-7 3.2.2 Establishment of Gauging Station ........................................................................................ 3-7 3.2.3 Water Level Recording and Flow Measurement ................................................................. 3-7 3.3 Geological and Geotechnical Investigations............................................................................... 3-7 3.3.1 Previous Study ........................................................................................................................... 3-8 i Trishuli Jal Vidhyut Company Limited Detail Project Report of UT3B HEP 3.3.5 Field Investigation .................................................................................................................... 3-9 3.3.5.1 Core Drilling .................................................................................................................. 3-9 3.3.5.2 Geological Mapping .................................................................................................. 3-10 3.3.5.3 Seismic Refraction Survey ........................................................................................ 3-10 3.3.5.4 Construction Material Survey .................................................................................. 3-12 3.3.2 Additional geological geotechnical investigation, Fiscal Year-2013 ............................... 3-13 Chapter 4 Hydrology and Sediment Study 4.1 Introduction ........................................................................................................................................ 4-1 4.2 Basin Characteristic ........................................................................................................................... 4-2 4.3 Review of Catchment Area ............................................................................................................... 4-3 4.4 Climate Study ...................................................................................................................................... 4-3 4.5 Available Hydrological Data ............................................................................................................. 4-4 4.5.1 Installation of Hydrometric Station ............................................................................................ 4-4 4.5.2 Hydrometric Stations .................................................................................................................... 4-5 4.5.3 Discharge Measurement by DHM and NEA ............................................................................ 4-5 4.6 Rating Curves ..................................................................................................................................... 4-7 4.7 Reference Hydrology ......................................................................................................................... 4-7 4.7.1 Mean Monthly Flow .................................................................................................................. 4-7 4.7.2 Long Term Trends in Flows .................................................................................................... 4-9 4.7.3 Correlation between Flows on Trishuli River at Upper Trisuli 3A dam site and Betrawati Gauge station 447 ...................................................................................................................... 4-9 4.7.4 Flow Duration Curve .............................................................................................................. 4-10 4.7.5 Downstream Release Flow ..................................................................................................... 4-10 4.8 Flood Estimates ............................................................................................................................... 4-10 4.8.1 Introduction ............................................................................................................................. 4-10 4.8.2 Flood Estimation by Regional Analysis ............................................................................... 4-11 4.8.3 Flood Frequency Analysis ...................................................................................................... 4-13 4.8.4 Flood levels ............................................................................................................................... 4-15 4.8.5 Construction Flood ................................................................................................................. 4-15 4.9 Glacier Lake Outburst Floods (GLOF) ....................................................................................... 4-15 4.9.1 General ...................................................................................................................................... 4-15 4.9.2 Historical Record of GLOF ................................................................................................... 4-16 4.9.3 GLOF Hazard .......................................................................................................................... 4-24 ii Trishuli Jal Vidhyut Company Limited Detail Project Report of UT3B HEP 4.9.4 Peak Flows from GLOFs ....................................................................................................... 4-24 4.9.5 Peak Flow Attenuation with Distance .................................................................................. 4-25 4.9.6