EGL Ref: 8983 23 June 2022 Page ii WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. CONTENTS Page No. 1.0 INTRODUCTION 5 2.0 BACKGROUND AND CURRENT SITE FACILITIES 5 2.1. Location and existing TSFs 5 2.2. Construction and operation 6 2.3. Monitoring and Surveillance 6 2.4. Dam Safety Reviews 7 2.4.1. Intermediate Dam Safety Review 7 2.4.2. Comprehensive Dam Safety Reviews 7 3.0 PERFORMANCE TO DATE 7 4.0 WAIHI NORTH PROJECT AND STORAGE 3 TSF 8 4.1. Waihi North Project (WNP) 8 4.2. Storage 3 - TSF 8 5.0 GEOTECHNICAL INVESTIGATIONS AND SITE GEOLOGY 11 5.1. Geology Overview 11 5.2. Topsoil 11 5.3. Volcanic Ash 11 5.4. Colluvium 12 5.5. Alluvium 12 5.6. Rhyolite – Tuff and Lava Flows 12 5.7. Dacite – Tuff Breccia 13 5.8. Andesite – Tuff and Lava Flow 13 6.0 SEISMIC HAZARD 13 7.0 FLOOD HAZARD 13 8.0 POTENTIAL IMPACT CLASSIFICATION (PIC) 14 9.0 TAILINGS CHARACTERISTICS 14 10.0 DESIGN BASIS 15 10.1. Dam Design Criteria 15 10.2. Uphill diversion drain sizing 16 10.3. Perimeter drain sizing 16 10.4. Embankment permanent surface water collection systems 17 10.5. Collection pond design 17 10.6. NAF Stockpile 17 11.0 DEVELOPMENT OF STORAGE 3 TSF 18
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