Supporting Technical Assessments

v File: WAI-983-080-REP-GT-0013_Rev0.docx This report shall only be read in its entirety. CONTENTS Page No. 1.0 INTRODUCTION............................................................................................................. 1 1.1. Dam Breach Guidance .................................................................................................. 1 1.2. Limitations ..................................................................................................................... 2 2.0 WAIHI TAILINGS STORAGE FACILITIES............................................................... 2 3.0 OBJECTIVES AND SCOPE............................................................................................ 3 4.0 INFORMATION REQUIREMENTS ............................................................................. 3 5.0 POTENTIAL FAILURE MODES AND DAM FAILURE SCENARIOS ................... 3 6.0 POTENTIAL CASCADE FAILURE SCENARIOS...................................................... 4 7.0 TAILINGS CHARACTERISATION.............................................................................. 5 8.0 HYDROLOGIC ANALYSIS ........................................................................................... 5 9.0 TAILINGS DAM BREACH ASSESSMENT CASES ................................................... 6 10.0 BREACH ANALYSIS....................................................................................................... 6 10.1. Physical Processes for Tailings Dam Breaches ........................................................... 6 10.2. Type of Breach Outflows .............................................................................................. 6 10.3. Dam Breach Locations.................................................................................................. 6 10.4. Volume of Breach Outflow ........................................................................................... 7 10.5. Breach Modelling .......................................................................................................... 7 11.0 RUNOUT ANALYSIS ...................................................................................................... 8 11.1. Process I ......................................................................................................................... 8 11.2. Process II ...................................................................................................................... 10 12.0 TDBA RESULTS AND DISCUSSION ......................................................................... 11 12.1. Sunny Day Breach Scenario ....................................................................................... 11 12.2. Rainy Day Breach Scenario........................................................................................ 13 13.0 ASSESSMENT OF POTENTIAL IMPACT CLASSIFICATION............................. 17 14.0 EMERGENCY PLANNING .......................................................................................... 18 15.0 CONCLUSIONS.............................................................................................................. 18 REFERENCES ............................................................................................................................ 19 TABLES 1 TO 8 FIGURES 1 TO 5 APPENDIX A. NATURAL FLOW HYDROGRAPH AND 1 IN 1000 YEAR FLOOD APPENDIX B. INUNDATION RESULTS OF SUNNY DAY BREACH SCENARIO

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