8 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 While some of these facilities (like the liquid oxygen storage) are not proposed to change as part of the upgrades, they have been included in this assessment to enable review of any cumulative impact. The current Processing Plant footprint is shown below inFigure 3.1. Figure 3.1: Aerial view of the existing Processing Plant and Water Treatment Plant showing storage locations of hazardous substances (source: Google Earth, 2021 imagery) 3.3 Water Treatment Plant The Water Treatment Plant (WTP) is located to the north of the Processing Plant as shown inFigure 3.1. The WTP has a discharge permit which currently expires in 2034. Water requiring treatment from the mining activities and runoff collected in the Processing Plant area is treated in the WTP. In particular, cyanide is used in the Processing Plant for metal extraction as it easily dissolves metals from the ore. The cyanide wastewater from this process ends in the tailings waste which is pumped to the tailings storage facility. The wastewater and runoff collection process is summarised below: The tailings are pumped to the tailing storage facility (TSF). The decanted water and seepage from the tailings are collected and either recycled for use in the Processing Plant or treated in the WTP prior to discharge in the Ohinemuri River. Water is also collected from dewatering of the existing mines. This minewater is treated through the WTP prior to discharge into the Ohinemuri River.
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