Supporting Technical Assessments

21 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 4.1: Summary and purpose of HSW-HS requirements Control measure Facility and substances Purpose of control Signage Processing Plant  Flammable, oxidising, corrosive, toxic and ecotoxic substances WTP  Oxidising, corrosive, toxic and ecotoxic substances Development Site  Flammable liquid, flammable gas, Class 1 explosive substances Ensures off site persons and emergency response personnel are able to identify the hazards at the site and take appropriate precautions. Secondary containment Processing Plant  Hydrochloric acid, caustic soda, cyanide solution, diesel and maintenance oils WTP  High calcium hydrated lime, ferric chloride, hydrogen peroxide. Development Site  Maintenance oils and diesel Prevents release of a hazardous liquid to the environment in the event of a failure of primary containment (tank or package) and enables recovery of the substance for safe disposal. Fire extinguishers Processing Plant  Diesel, oxygen WTP  Hydrogen peroxide Development Site  Class 1 explosives, LPG and diesel Enables swift emergency response to small fires in areas near hazardous substances to prevent ignition of flammable, explosive or oxidising substances. Segregation of incompatible substances Processing Plant  Flammable, oxidising, corrosive, toxic and ecotoxic substances WTP  Oxidising, corrosive, toxic and ecotoxic substances Development Site  Flammable and Class 1 explosive substances Minimises additional adverse consequences from a spill or fire by preventing reactive substances from mixing in the storage area. Substance secured from unauthorised access Processing Plant  Caustic soda, hydrochloric acid, cyanide (solid), cyanide solution, mercury, oxygen WTP  Ferric chloride, hydrogen peroxide. Development Site  Class 1 explosive substances Limits access to trained personnel and minimises the potential for operator error or tampering. Emergency response planning Processing Plant  Diesel, quicklime, caustic soda, hydrochloric acid, cyanide (solid), cyanide solution, mercury, oxygen WTP Describes the emergency procedures for a site and takes into account any foreseeable emergency such as a fire, spill or injury. Emergency Response Plans must be regularly tested by the site.

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