16 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Control measure Facility and substances Purpose of control overpressure levels (controlled zones) Diesel, ANE and Class 1 explosives Hazardous areas (ignition source restrictions) SFA Diesel, acetylene WUG Diesel Prohibits ignition sources from areas where flammable substances are stored to minimise the risk of a fire. Earthing and bonding of equipment SFA Diesel and class 1 explosives WUG Diesel and class 1 explosives Minimises risk of an ignition source from build-up of static charge starting a fire at a flammable or explosives store. 4.2.1 Magazine certification The HSW-HS regulations require any storage of Class 1.1D explosives in excess of 2.5 kg to be secured in a magazine designed and certified to meet requirements for the material of construction, the design of the locking arrangement and arrangements for prevention of removal. The magazine is also required to have an earthing system between the atmosphere above the hazardous substance location and earth to dissipate any build-up of electrostatic charge. The magazines must also have a lightning interceptor designed in accordance with section 4 in AS/NZS 1768: 2007—Lightning protection. These features are required to minimise the risk of an inadvertent ignition of the explosives. The magazines used by OGNZL at the surface will be designed to standard AS 2187.1 1998 for relocatable magazines and design compliance certificates will demonstrate that the requirements set in the HSW-HS regulations are met by the proposed magazines. While the underground chambers are not strictly magazines as would be used on the surface, equivalent standards for security, design and construction will be adhered to, and the facility will be certified by an independent compliance certifier. 4.2.2 Magazine separation 4.2.2.1 Surface magazine At the surface magazine, the H.E. will be stored in six separate magazines, three containing a maximum of 1,150 kg Net Explosive Quantity (NEQ) and three containing a maximum of 1,300 kg NEQ. Each magazine must be separated by a minimum distance of 27 m, with mounding undertaken in accordance with industry standard ‘AS 2187.1, Appendix B’, to ensure the distances can be maintained in order to mitigate risk of inter-magazine propagation. The 10 kg NEQ I.E. magazine may be located within 27 m of another magazine, however, in accordance with AS 2187.1, a minimum offset of 3.5 m (mounded) or 10 m (un-mounded) shall be maintained. The proposed layout of the surface magazine compound is indicated inFigure 4.1 .
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