Oceana Gold Waihi North Project Waihi North Project Geochemical Assessment – Geochemistry of Tailings and Overburden, Treatment and Mitigation Revision 9 – 17-Jun-2022 Prepared for – Oceana Gold (New Zealand) Limited – Co No.: 2274246 A-2 AECOM comparison was the identification of potential contaminants of interest which may require rock management practices that differ from those currently undertaken by OGNZL. Additional testing, beyond the initial multi-element screening, was undertaken where appropriate to further assess the identified contaminants of interest. The geochemical composition of ore has been used to determine the likely composition of the mine tailings that would be produced from ore processing. To achieve this, mine tailings produced from Martha mine ore were used as the basis for assessment, with compositional differences between Martha, Gladstone and WUG ore assumed to result in proportional differences in tailings composition. A similar approach is used to predict likely effects to decant and seepage quality from the storage facilities as a result of the deposition of mine tailings from the planned operations in the current and future storage facilities. The initial elements screened, their recommended detection limits, and additional static tests carried out are provided in Table 28. Table 28 Initial Static Analysis Suite Multi Analysis Testing Favona & Martha Trace Elements Screened Previously Water Quality Compliance Limits Recommended detection limit (mg / kg) Total Sulphur (%) Y Total Carbon (%) Y ANC (kg CaCO3/tonne) Y Aluminium Y 500 Iron Y Y 500 Calcium Y 500 Magnesium Y 500 Sodium Y 500 Potassium Y 500 Antimony Y Y 0.1 Arsenic Y Y 0.1 Barium Y 1 Cadmium Y Y 0.01 Cobalt Y 1 Chromium Y Y 5 Copper Y Y 1 Lead Y Y 1 Mercury Y Y 0.01 Manganese Y Y 5 Molybdenum Y 0.1 Nickel Y Y 1 Selenium Y Y 0.05 Vanadium 1 Zinc Y Y 5 Titanium Y 100 Boron 1
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