Supporting Technical Assessments

14 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Waihi Processing Plant, Water Treatment Plant and Development Site Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Substance State Hazard Classification Proposed maximum volume Storage location and description Pre-2021 Post-2021 Ferric chloride Liquid 6.1D 8.1A 8.2C 8.3A 9.3C Acute oral/dermal/inhalation toxicity Category 4 Corrosive to metals Category 1 Skin corrosion Category 1C Serious eye damage Category 1 Hazardous to terrestrial vertebrates 30,000 L Two tanks (20,000 L and 10,000 L) in the WTP Hydrogen peroxide Liquid 5.1.1B 6.1D 8.2B 8.3A 6.9B 9.1D 9.3C Oxidising liquids Category 2 Acute oral toxicity Category 4 Skin corrosion Category 1B Serious eye damage Category 1 Specific target organ toxicity – single or repeated exposure Category 2 Hazardous to the aquatic environment chronic Category 4 Hazardous to terrestrial vertebrates 35,000 L Two tanks (17,500 L each) in the WTP Mercury Liquid 6.1B 6.5B 6.8A 6.9A 8.1A 9.1A Acute oral, inhalation toxicity Category 2 Skin sensitisation Category 1 Reproductive toxicity Category 1 Specific target organ toxicity – repeated exposure Category 1 Corrosive to metals Category 1 Hazardous to the aquatic environment acute and chronic Category 1 10 kg Recovered at the condenser in the Gold Room (Electrowinning Building) through the retort processes Diesel Liquid 3.1D, 6.1E 6.3B 6.7B 9.1B Flammable liquids Category 4, Aspiration hazard Category 1, See Note 1. Carcinogenicity Category 2, Hazardous to the aquatic environment chronic Category 2 200,000 L Various units: Self-bunded isotainers (40,000 L) or portable tanks (<6,000 L)

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