Supporting Technical Assessments

iii This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. CONTENTS Page No. 1.0 INTRODUCTION 1 2.0 WAIHI OPERATION LOCATION AND SITE DESCRIPTION 2 2.1. Location 2 2.2. Waihi Mine site description 3 3.0 SITE CONDITIONS 5 3.1. Climate 5 3.1.1. Climate change 5 3.2. Geological setting 5 3.2.1. Tectonic setting 5 3.2.2. Regional Geology 8 3.2.3. Geology Around the Development Site 9 3.3. Waihi operation site specific seismic hazard 11 3.4. Hydrology 13 3.5. Hydrogeology 15 4.0 WAIHI OPERATION – EXISTING TAILINGS STORAGE AND ROCK DISPOSAL 15 4.1. Nature of the ore and overburden at Waihi 15 4.2. Nature of tailings at Waihi 16 4.2.1. General 16 4.2.2. Ore-bearing rock 17 4.2.3. Process and water treatment plant setup 17 4.2.4. Tailings delivery and discharge 18 4.2.5. Tailings impoundment lining and subsurface drains 19 4.2.6. Tailings profile within the impoundments 20 4.3. Existing zoned embankment design 22 4.4. Storage 2 design and construction 24 4.5. Storage 1A design and construction 27 4.6. Operation 30 4.7. Monitoring and Surveillance 30 4.8. Peer review 31 4.9. Performance 32 4.9.1. Seepage 32 4.9.2. Porewater Pressures 34

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