GHD | Oceana Gold NZ Ltd | 12552081 | Geochemical Assessment Wharekirauponga Underground Mine (WAI985-000-REP-LC-0013) iii Contents 1. Introduction 1 1.1 Project Description and Background 1 1.2 Scope of Works 3 1.3 Scope and limitations 3 1.4 Assumptions 4 2. Geology and Mineralogy 5 2.1 Local Geology 5 3. Geochemical Assessment 6 3.1 Acid and Metalliferous Drainage 6 4. Spoil Geochemistry 8 4.1 Data Sources 8 4.1.1 Willows Access Tunnel 8 4.1.2 WUG Mine (Wharekirauponga Orebodies) 10 4.2 Spoil Composition 11 4.2.1 Willows Access Tunnel – Multi Element Analysis 11 4.2.2 WUG Mine – Multi Element Analysis 14 4.2.3 Statistical Analysis of Spoil Geochemistry 17 4.2.4 Distribution of Trace and Major Elements 18 4.3 Spoil Acid Generating Potential 20 4.3.1 Static Testing 20 4.3.2 Column Testing 22 6. Spoil Management 24 6.1 General Management Philosophy 25 7. Water Quality 26 8. Conclusions 31 9. References 32 Table index Table 1 Geochemistry of Spoil Material – Willows Access Tunnel 12 Table 2 Geochemistry of Spoil Material – WUG Mine 15 Table 3 Predicted sulphate and arsenic concentrations based on column sulphate generation rate 28 Table 4 Assumed Water Quality Dataset from Waihi 30
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