59 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 9 Conclusion The key risks related to the proposed storage and use of hazardous substances associated with the proposed upgrades to OGNZL’s facilities in Waihi include: Fire risk in the LPG, diesel, oxygen or hydrogen peroxide storage tank areas at the Processing Plant, WTP and Development Site. Risk of ecotoxic or human health effects from a spill of corrosives, oxidizers, diesel, oils, mercury or cyanide at the Processing Plant, WTP or Development Site during delivery, storage or use. Risk of an unplanned detonation at the proposed Class 1 explosives storage facility at the Development Site. The risk to people and property from a fire at the flammable or oxidising substance locations at the Processing Plant or Development Site has been assessed as low, as hydrocarbons and oxidising substances on-site are managed through controls (security monitoring, training and handler certifications, emergency response plans, mine rescue response team) and equipment design (e.g. separation distances to the site boundary, separation from ignition sources, certification of storage areas to comply with safety regulations, provision of firefighting infrastructure at tank compounds). The storage locations are isolated from public access and are within the site’s security boundary. The proposed transformers contain a low hazard mineral oil and are each bunded to contain the oil in the event of a leak. Installation of a new substation north of the Processing Plant has been assessed as a negligible hazard to people, property or ecosystems. The environment is considered sensitive to the effects of a spill of the ecotoxic liquid hazardous substances stored and used at the Processing Plant, WTP and Development Site which includes diesel, maintenance oils, corrosive substances (hydrochloric acid, caustic soda, hydrated lime), oxidisers (hydrogen peroxide), cyanide or mercury. The risk to the environment will be managed through site design (secondary containment, automation including interlock systems, segregation of incompatible substances, certification of storage systems tanks), and operational procedures (e.g. emergency response plan including dedicated plans for high risk substances, spill response plans, dedicated mine rescue response team, standard operating and delivery procedures for key hazardous substances). In particular, cyanide poses a high hazard to the environment due to its high toxicity to both humans and ecological receptors. OGNZL has provided additional structural controls within the Processing Plant to retain hazardous liquid spills in engineered ponds in the event of an accidental release. Taking into account these controls, the effects on people, property and the environment from the use and storage of hazardous substances have been assessed as less than minor. The neighbouring rural properties near the Development Site are considered sensitive to the effects of an unintended detonation at the proposed Class 1 explosives store. However, the potential effects are appropriately managed by the controls which apply to the activity under the HSW-HS regulations. These include securing the facility from unauthorised access, segregation of incompatible materials, provision of fire-fighting facilities and emergency management procedures, and separation from sensitive locations. In order to establish and operate the Class 1 explosives storage facility, OGNZL must notify WorkSafe and obtain certification from an accredited independent compliance certifier for both the facility itself and its Class 1 substance handlers. Overall, the effects on people and property from establishment of the new Class 1 storage facility are less than minor and no additional controls are considered necessary as part of the resource consent. The Martha Open Pit mine and the explosives at the existing surface sites are the nearest comparable industrial activities anticipated to store hazardous substances. The significant separation
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