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 Executive summary Oceana Gold (New Zealand) Limited (OGNZL) is seeking resource consent from the Hauraki District Council (HDC) and Waikato Regional Council (WRC) for the Waihi North Project (WNP) for activities proposed to extend the life of mining in Waihi. As part of the WNP, OGNZL is seeking resource consent from the Hauraki District Council (HDC) for proposed upgrades to the existing Ore Processing Plant and expansion of the Water Treatment Plant in Waihi, as well as to establish a new Class 1 explosives storage facility to service the ongoing mining operations. This hazardous substances technical assessment has been prepared to evaluate the effect of the hazardous substance storage and use associated with upgrades to the Processing Plant, Water Treatment Plant and the proposed new explosives storage facility in Waihi. These activities will include storage and use of explosives, oxidising, corrosive and toxic substances, fuels, maintenance oils and greases in the Martha Mineral Zone. The storage and use of hazardous substances in New Zealand is governed primarily by the Health and Safety at Work (Hazardous Substance) regulations 2017 which sets out control measures triggered by the volumes and types of hazardous substances proposed. Hazardous substance storage and use is further controlled by Resource Management Act 1991, exercised through Chapter 7.7. of the Hauraki District Plan (HDP). The proposed activity requires resource consent in accordance with the HDP Rule 7.7.10 as a non-complying activity for use of hazardous substances in the Martha Mineral Zone. This assessment has evaluated the hazards and risks in accordance with the Ministry for the Environment’s Assessment Guide for Hazardous Facilities, with supplementary guidance from the New South Wales Department of Planning’s Hazardous Industry Planning Advisory Paper series. The key risks identified for the proposed activities include: Fire risk in the diesel, oxygen or hydrogen peroxide storage tank areas at the Processing Plant and WTP or at the LPG tanks in the Development Site. Risk of ecotoxic or human health effects from a spill of corrosives, oxidizers, diesel, mercury or cyanide at the Processing Plant or WTP during delivery, storage or use. Risk of an unplanned detonation at the proposed Class 1 explosives storage facility at the Development Site. Management measures to reduce the likelihood and severity of the risk events include appropriate site and equipment design (e.g. separation distances to sensitive offsite locations and incompatible materials, provision of fire protection systems and secondary containment, independent certification of storage systems, drainage design to capture and treat any potentially contaminated runoff) and management controls (personnel access restrictions, security monitoring, staff training and handler certification, maintenance, inspections, and emergency response plans). The risk to people and property from a fire at the Processing Plant or at the LPG tanks in the Development Site has been assessed as low, as hydrocarbons and oxidising substances on-site are managed through operational controls (security monitoring, training and handler certifications, emergency response plans, maintenance, 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 environment is considered sensitive to the effects of a spill of the ecotoxic liquid hazardous substances stored and used at the Processing Plant and WTP, which includes diesel, corrosive substances (hydrochloric acid, caustic soda, hydrated lime), oxidisers (hydrogen peroxide), cyanide
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