47 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 Hazardous Substance and quantity stored Identification of potential hazard properties (Hazard level1) Failure Modes Exposure pathways/ Affected part of environment Indicative hazard rating Potential for off-site effects Hydrochloric Acid (>25%) (24,000 L) Human toxicity (high/moderate) Ecotoxicity (low) Valve leak, pipe failure, accidental release during use and unloading Low fire risk if stored or used near incompatible substances People, ecosystems High hazard to human health via ingestion, moderate hazard by skin contact. Low hazard to ecosystems in a spill. Yes Human health effects and effects on ecosystems to be considered further. Cyanide (Liquid 30%) (112,000 L) Human toxicity (high) Ecotoxicity (high) Valve leak, pipe failure, accidental release during use and unloading People, ecosystems High hazard to human health via ingestion or inhalation. High hazard to ecosystems in a spill. Yes Human health effects and effects on ecosystems to be considered further. Cyanide (solid) (77,000 kg) Human toxicity (high) Ecotoxicity (high) Accidental spill during unloading and use. People, ecosystems High hazard to human health High hazard to ecosystems in the event of a spill. Yes (if interacts with fluids) Human health effects and effects on ecosystems to be considered further. Oxygen gas (30,000 L) Fire/Explosion effects (high) Failure of the cryogenic storage tank system Tanker completing silo refill People, property High fire hazard, noting this would require presence of combustible material and a source of ignition. Yes (if failure of the system) Effects due to fire to be considered further. LPG (80,000 L) Fire/Explosion effects (high) Valve leak, pipe failure, accidental release during refuelling Fire in storage area People, property High fire hazard. Yes Effects due to fire to be considered further.
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