114 Table 34: Consented receiving environment water quality and modelled water quality at sample location OH6 of the Ohinemuri River (from GHD 2022). OH6 (Modelled Data) Consented Receiving Water Quality Chemical Parameter Maximum Daily Mean Max Hardness 20 g/m3 CaCO3 Hardness 100 g/m3 CaCO3 pH Not Modelled 6.5 – 9.5 Temperature 22.6 26.8 <3°C Rise Cyanide, WAD (g/m3) 0.004 0.018 0.093 0.093 Iron (g/m3) 0.30 0.46 1.0 1.0 Manganese (g/m3) 0.036 0.059 2.0 2.0 Copper (g/m3) 0.0011 0.0031 0.003 0.011 Nickel (g/m3) 0.0033 0.0033 0.04 0.160 Zinc (g/m3) 0.0040 0.0062 0.027 0.100 Silver (g/m3) < 0.0001 < 0.0001 0.00025 0.00284 Antimony (g/m3) 0.0027 0.0058 0.030 0.030 Arsenic (g/m3) 0.0028 0.0050 0.190 0.190 Selenium (g/m3) 0.0011 0.0023 0.020 0.020 Mercury (g/m3) < 0.00008 < 0.00008 0.000012 0.000012 Cadmium (g/m3) 0.0003 0.0005 0.0003 0.001 Chromium VI (g/m3) < 0.01 < 0.01 0.01 0.01 Lead (g/m3) 0.0001 0.0002 0.0004 0.0025 TSS (g/m3) Not Modelled +10 g/m3 compared to upstream where upstream < 100 g/m3 or <10% increase Ammonia (g/m3) 0.89 1.93 0.189 – 3.01 Major cations / Anions Ca2+ 167 333 N/A Mg2+ 36 44 N/A Na+ 35 44 N/A K+ 7 12 N/A SO4 2+ 660 1033 N/A *Trace element concentrations are dissolved *Where all samples of the monitoring period were below the mdl, the concentration is given as <mdl. Otherwise the mdl is used as the concentration for the specific sample. 1. Dependent on temperature and pH (Table 2 of RC 971323). 20.3 Effects of Water Quality Criteria on Ecological Values We have outlined the water quality and ecological values of the Ohinemuri River in section 13 above. We have demonstrated that over the period of the operations at Oceana Gold Waihi the ecological values of the Ohinemuri River have remained stable and persistent. OGNZL continues to demonstrate compliance with the consent conditions by carrying out monitoring and any repeat sampling and investigations required by the treated water discharge permit. Our review of this monitoring data shows that mining operations at Waihi continue to meet the required receiving water quality standards31 with no detriment or adverse effect to the ecological values of the Ohinemuri River. 31 As set out in WRC resource consent conditions 971285, 971311, 971312, 971303-971306 and 971323
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