9 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 The Processing Plant run-off is diverted from the Processing Plant area to the associated collection pond. The run-off is then treated in the WTP prior to discharge into the Ohinemuri River. In principle, runoff from anywhere on OGNZL’s site that has been exposed to potentially acidic rock (PAF) is routed to the WTP. All discharges to the Ohinemuri River are subject to the conditions of the WTP’s discharge consent. As part of the proposed WNP and Project Martha operations, multiple tailing storage facilities will be in operation. It is also proposed that water arising from the mining at the WUG will be pumped back to the WTP in Waihi. The WTP capacity requirement is likely to increase by 100% to a maximum of 52,000 m3 per day. To accommodate the additional throughput, changes to the tank number and capacity are proposed, including addition of tanks for metal removal and cyanide destruction, and additional clarifier capacity. The proposed specific hazardous substance storage associated with water treatment includes: Two tanks of ferric chloride (20,000 L and 10,000 L); Two tanks of hydrogen peroxide (17,500 L each); Two tanks of compressed carbon dioxide (20,000 L each); and Hydrated lime solution in three tanks (102,000 L each). These are also indicated onFigure 3.1in the previous section. 3.4 Development Site 3.4.1 Relocated facilities The area east of the Processing Plant and Water Treatment Plant in OGNZLs landholding is referred to as the “Development Site”. It is principally comprised of the tailings storage facilities and rock stockpiles. As part of the WNP, the following changes to activities involving hazardous substances are proposed: The existing workshop which is operated with an inventory of up to 8,000 L of maintenance oils and greases and two 20,000 L diesel tanks will be relocated approximately 60 m to the southwest of its existing location. Two LPG tanks each containing 40,000 L, currently located north of the Processing Plant and proposed to be moved approximately 270 m to the east. These revised locations are illustrated inFigure 3.2 below.
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