GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 88 Parameter Existing shallow groundwater quality (DH05a median) Predicted values after equilibration of NRS leachate with shallow groundwater (AECOM, 2021c) Existing Ohinemuri River quality (OH3 median) Predicted values after mixing with Ohinemuri River Receiving water quality criteria Cr <0.0005 <0.0005 <0.0005 <0.00050 0.01 Cu <0.0005 0.000060 <0.0005 <0.00050 0.003 Fe 6.8 21.0 0.10 0.19 1 Hg <0.00008* <0.00008* <0.00008* <0.00008* 0.000012 K 2.3 3.0 2.0 2.0 Mg 1.2 28.0 1.9 2.0 Mn 1.5 4.0 0.010 0.027 2 Na 9.9 11.0 9.2 9.2 Ni 0.0051 <0.003 <0.0005 <0.00051 0.04 Pb 0.00016 <0.0001 <0.0001 <0.0001 0.0004 SO4 5.0 338.0 5.0 6.4 Sb <0.0002 0.00030 <0.0002 <0.00020 0.03 Se <0.001 <0.001 <0.0002 <0.00020 0.02 Zn 0.016 <0.003 0.0019 0.0019 0.027 Notes: Receiving water quality criteria values for hardness 20 g/m3 CaCO3 Values in bold indicate an exceedance of the receiving water quality criteria * The mercury (Hg) criterion is lower than available laboratory detection limits Denotes a predicted increase from existing groundwater / surface water quality Table 4.8 Predicted mass flux to the Ohinemuri River during operation of the NRS (50% rainfall recharge) Parameter Mass flux (kg/day) to Ohinemuri River Al 1.2 As 0.00054 Ba 0.026 Ca 46.7 Cd 0.00068 Co 0.19 Cr 0.00012 Cu 0.0026 Fe 29.3 Hg 0.000013 K 1.4 Mg 11.2 Mn 1.6 Na 10.2 Ni 0.076
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