Supporting Technical Assessments

23 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 Control measure Facility and substances Purpose of control Stationary Container System Compliance certification required Processing Plant  Diesel, oxygen, cyanide solution, hydrochloric acid, caustic soda WTP  Hydrogen peroxide, ferric chloride, hydrated lime Development Site  LPG, diesel Independently certifies that the tank or process container and associated equipment is safe and complies with the standards for tank design, such as providing secondary containment, pressure relief and overfill protections. Separation from land use activities according to potential overpressure levels (controlled zones) Processing Plant  Not applicable WTP  Not applicable Development Site  Class 1 explosives Minimum separation distances for blast overpressure levels are specified to ensure that people and structures are located at a suitable distance from the explosive hazard for protection from adverse effects. Hazardous areas (ignition source restrictions) Processing Plant  Diesel WTP  Not applicable Development Site  LPG, diesel Prohibits ignition sources from areas where flammable substances are stored to minimise the risk of a fire. Earthing and bonding of equipment Processing Plant  Not applicable WTP  Not applicable Development Site  Class 1 explosives, LPG Minimises risk of an ignition source from build-up of static charge starting a fire at a flammable or explosives store. 4.3 Signage Signage is required on the hazardous substances identified in Table 4.1, triggered by the substance’s classification and quantity stored on-site under the HSW-HS. Signage enables emergency responders to identify the hazards at each location. The HSMP provides further requirements for the site which states signage must be displayed at the entrances to alert persons entering the site that the hazards are present and further appropriate precautions should be taken. The HSMP requires signage at storage areas and entrances to site and/or buildings for the appropriate class of substance being stored or used in the area. 4.4 Certified handlers A certified handler is required for person(s) handling very hazardous substances. In order to obtain a certified handler compliance certificate, the person(s) must demonstrate the knowledge, experience and competency to safely handle the hazardous substances. A certified handler compliance certificate is required for acutely toxic substances (6.1A and 6.1B) substances, substances that require controlled substance licence (Class 1 substances) which includes most explosives, fumigants and vertebrate toxic agents. This requirement applies to the solid cyanide and cyanide solution used as part of the processing of gold ore, and to the ANFO, packaged explosive, boosters and initiating devices proposed to be stored at the Development Site. This requirement reduces the likelihood of

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