GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project 36 dissolved trace elements and sulphate. Some elevated trace element concentrations are potentially the result of exposed mineralisation within the catchment. 4.1.3 Ohinemuri River Baseline water quality data from the Ohinemuri River has been collated for the key monitoring data stations OH3 (upstream of the WTP discharge), OH5, OH6 (downstream of the WTP discharge locations) and from RU1 located on the Ruahorehore tributary (Figure 6). Data for 2019 and 2020 has been collated as representative of current conditions and is provided in Appendix D. Average values are utilised within the cumulative assessment (Section 6.3.6). 4.2 Current and Predicted Source Water Quality Summary Table 11 provides a summary of “typical” water quality characteristics of the various water sources associated with the TSFs, processing areas, and dewatering water.. The presented data is considered a conservative estimate for the application of modelling future site treatment requirements and to assess the potential impact on the receiving environment. The data is sourced from operational water quality monitoring results and geochemical assessments, as outlined in AECOM, 2022 and GHD, 2022. AECOM (2022) has completed a study on the geochemistry of the materials that will be encountered within GOP and concluded that rock material from the GOP is elevated in mercury, antimony, and arsenic relative to the historic dataset. AECOM outline a rock management strategy that provides appropriate control measures and management practices to limit the effect of placement of this material to the receiving environment. Furthermore, the geochemical assessment concluded that geochemical controls and processes will likely result in WTP inflow water quality that is similar in nature to the current mine operation. GHD (2022) has completed a study on the geochemistry of the materials that will be encountered within the WUG tunnelling and mining activities. The assessment outlines predicted leachate and tunnel inflow water quality based on whole rock geochemistry and column leachate data. These predicted water qualities are utilised within the WBM as outlined in Section 6.
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