30 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 4.3: Separation requirements under the HSW-HS for hazardous substances Substance name Identified separation requirements Comments Caustic soda Segregated from all Class 1 substances, Class 4, Class 5, Class 6.1A, Class 6.1B and Class 6.1C toxic cyanides, and Class 8.2A and 8.2B corrosive alkalis/acids. Separation of Caustic soda as a Class 8 substance: 5 m to protected places or the boundary. Separation distances for hydrochloric acid as a Class 6.1B substance are: 8 m to protected places 4 m to public places Separation between the two tanks must be at least 1 m. These corrosive substances are stored on the western side of the electrowinning store approximately 50 m from the cyanides (Class 6.1 toxic substances). Distances to the boundary for all substances meet the requirements for separation from protected and public places. Hydrochloric acid (>25% solution) Cyanide (30% solution) Segregated from all Class 1 substances, Class 4, Class 5, and Class 8.2A and 8.2B corrosive alkalis/acids. Separation distances for Class 6.1B substances to protected places are 6 – 10 m for volumes 10,000 – 100,000 L and 3 – 5 m to public places for the same volumes. The cyanides are segregated from other hazardous substances in the reagent area. They are located 140 m from the nearest OGNZL boundary to the south, complying with the separation requirements. Cyanide (solid) Oxygen gas Oxidising gases should be 3 – 5 m away from incompatible substances. The separation distances specified for 30,000 L of Class 5.1.2A oxidising gas are as follows: 15 m away from protected areas 8 m away from public areas 5 m from ignition source. The oxygen tank is located in the centre of the Processing Plant and meets the separation requirements to incompatible substances. It is 140 m from the closest OGNZL boundary to the south, complying with separation requirements.
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