Supporting Technical Assessments

12 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 Table 3.2: Hazardous substance volumes and classifications Substance State Hazard Classification Proposed maximum volume Storage location and description Pre-2021 Post-2021 High calcium hydrated lime Liquid 8.2C 8.3A 9.1D Skin corrosion Category 1C Serious eye damage Category 1 Hazardous to the aquatic environment chronic Category 4 306,000 L Three tanks (102,000 L each) at the north of the WTP High calcium quicklime Solid 8.2C 8.3A 9.1D Skin corrosion Category 1C, Serious eye damage Category 1 Hazardous to the aquatic environment chronic Category 4 70,000 kg Silo west of the Processing Plant Caustic soda (Sodium hydroxide 50%) Liquid 6.1D 6.1E 8.1A 8.2B 8.3A 9.1D. Acute oral, dermal toxicity Category 4 Aspiration hazard Category 1 Corrosive to metals Category 1 Skin corrosion Category 1B Serious eye damage Category 1 Hazardous to the aquatic environment chronic Category 4 24,000 L Tanks on the western side of the electrowinning area. Hydrochloric Acid (>25%) Liquid 6.1B 8.1A 8.2B 8.3A 9.1D 9.3C Acute oral toxicity Category 2 Corrosive to metals Category 1 Skin corrosion Category 1B Serious eye damage Category 1 Hazardous to the aquatic environment chronic Category 4 Hazardous to terrestrial vertebrates. 24,000 L Tanks on the western side of the electrowinning area. Oxygen gas Gas 5.1.2A Oxidising gas Category 1 30,000 L Cryogenic pressure vessel, east of the Processing Plant. Carbon Dioxide Gas Not classified as hazardous Compressed non-hazardous gas 40,000 kg/L Two cryogenic pressure vessels in the WTP

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