8 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 The Class 1 explosive substances will be stored in six H.E magazines (for the ANFO, boosters and packaged explosives) and one I.E magazine (for the detonator devices) at the surface site on Willows Road. Once the underground mine is established, an additional storage facility for Class 1 explosives will be set-up underground near the resource, at a depth of 380 m below the surface. This will also comprise of six separate H.E. chambers and one I.E. magazine. The key hazard associated with these substances is the mass explosion hazard producing a blast overpressure impact around the surface magazine, and at the surface vents for the underground store. The oxidising substance, ANE, will be stored in a secure bunded compound at the SFA east of the portal entrance, and once the underground mine is established, at two underground stores near the WUG orebody. These stores will be separated from the underground explosives store location by approximately 130 m and 405 m respectively. The key hazard associated with ANE is the acceleration of fire, which requires management through separation from combustible materials. A suitably segregated gasser store will also be established at the SFA and later below ground. Gasser is a liquid with subsidiary low human health hazards by direct exposure. The ANFO, packaged explosive, boosters and ANE also present human health and environmental hazards. However, the inherent properties of the materials limit their mobility. The ANFO is provided as a granular solid. The boosters and packaged explosive are a granular solid packaged in cardboard tubes and a liquid emulsion in small plastic tubes respectively, and the ANE is a highly viscous emulsion that is considered a solid for the purpose of transport and storage1. In the event of a spill, these substances are easily contained and cleaned up with a low risk of contamination of waterways. Oxygen and acetylene gases will be stored and used at the workshops on the western side of the SFA for welding and cutting tasks. Acetylene is a highly flammable gas and oxygen will accelerate a fire; these gases are incompatible and will be stored separately in well ventilated, secure locations at the workshop. Diesel, gasser and some of the maintenance oils are liquids with chronic human health hazards. Diesel and some of the oils are also hazardous to aquatic ecosystems. These substances will be stored and used in bunded areas and in areas that drain to stormwater treatment. The distance between the proposed storage locations and OGNZL’s boundary limits the potential for off-site persons to come into contact with any released material in the case of a spill. Similarly, lime has a human health hazard when in direct contact with eye tissue. Lime is a solid powder that is able to be easily managed in the event of a spill. It is stored and used central to the site suitably separated from the site boundary, minimising the chance of contact with the public. 1 ANE safety data sheet, Orica New Zealand Limited, 27 November 2019
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