GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project 37 Table 11 WBM Assumed Water Quality Inputs Area Dewatering Groundwater Quality1 Wharekirauponga Tunnel Dewatering Groundwater Quality2 Collection Ponds - Embankment / RS Runoff1/4 Contingency Ponds - Process Runoff1 Data Source Martha dewatering data GHD 2022 WSP / NSPSP / NCP1 / S3 / S4 / S5 data WTPCP/CSP01/CSP2S/FSPCP data Parameter Min Med 95th %ile Max n (last 3 years) Min Med 95th %ile Max n (last 3 years) Min Med 95th %ile Max n (last 3 years) Min Med 95th %ile Max n (last 3 years) pH 6.6 7.3 7.7 7.8 41 7.7 6.5 7.2 7.9 8.4 21 4 6.7 7.38 7.5 13 TSS 83 1200 7500 10400 41 7500 3 18 52 55 21 3 9 33.4 40 13 Ni 0.0085 0.0196 0.0794 0.106 15 0.0794 0.1 0.1 0.194 0.2 7 0.0021 0.0086 0.083 0.096 11 Cd 0.0001 0.00052 0.001928 0.0026 15 0.0019 0.0000 5 0.00005 0.000144 0.00017 14 0.00005 0.0001 0.00093 0.0015 11 Se 0.002 0.0094 0.0094 0.0094 41 0.0094 0.0002 0.001 0.001 0.001 14 0.001 0.001 0.004 0.007 11 Cu 0.001 0.001 0.0109 0.027 15 0.0109 0.0005 0.0008 0.0014 0.0019 14 0.0005 0.0023 0.013 0.017 11 As 0.004 0.01 0.0358 0.04 15 0.036 0.001 0.001 0.001 0.001 14 0.001 0.001 0.0017 0.002 11 Pb 0.0002 0.0002 0.00458 0.005 15 0.0046 0.0001 0.0001 0.0001 0.0001 14 0.0001 0.00015 0.0047 0.0076 11 Sb 0.0035 0.0067 0.01068 0.0139 15 0.0107 0.001 0.001 0.001 0.001 14 0.0002 0.0002 0.0034 0.0062 11 Al 0.008 0.022 0.0455 0.056 15 0.046 0.018 0.103 0.1858 0.193 5 0.013 0.098 2.188 2.9 9 Hg 0.00008 0.00008 0.00008 0.00008 15 0.00008 0.0000 8 0.00008 0.00008 0.00008 14 0.00008 0.00008 0.00073 0.00086 11 CN_Tot 0.001 0.02 0.073 0.08 15 - 0.001 0.002 0.02 0.02 21 0.001 0.001 0.062 0.08 7 Zn 0.055 0.32 1.211 1.61 15 1.21 0.001 0.006 0.021 0.025 14 0.014 0.114 2.14 2.8 11 SO4 660 1550 1780 2200 41 1780 20 93 492 570 14 18 99 922 1680 11 Fe 6.2 27 62.1 109 15 62 0.02 0.02 0.07 0.08 14 0.02 0.12 0.57 0.58 11 Mn 4.4 8.5 10.18 11.3 15 10.2 0.0148 0.35 1.7 2 14 0.105 0.58 2.7 3.3 11 Na 41 59 66 75 41 66 4.2 7 33 41 7 1.44 5.6 50 79 9 Mg 35 73 108.1 120 40 108 2.2 16.25 30 31 14 1.43 3.2 21 34 11 K 7.3 9 12.12 13.9 39 12 2.1 3.7 7.8 8.8 7 1.01 1.65 9.2 13.2 9 Co 0.0028 0.0118 0.0574 0.079 13 0.057 0.0004 0.003 0.011 0.0118 7 0.0014 0.0048 0.032 0.042 9 Ca 291 510 594 615 37 594 8.1 88 171 186 14 15 30 260 470 11 NH3-N6 0.093 0.87 8 11.6 13 8 0.01 0.025 0.074 0.121 21 0.01 0.021 0.88 2 13 Notes: 0.00615 Greyed out cells signify data is utilised within WBM 95th %ile Conservative estimates for Wharekirauponga Component of WBM 1 2 Based on site monitoring data Conservative estimate based on Waihi dewatering data 3 Median numbers modelled reflective of the NRS, maximum numbers are conservatively assumed for RS1 and RS2 at Willows Farm 4 Median numbers modelled reflective of the NRS, Waihi TSF embankments, 95%ile numbers are conservatively assumed for RS1 and RS2 at Willows Farm 5 Median numbers modelled reflective of the Waihi TSF embankments, 95%ile numbers are conservatively assumed for RS1 and RS2 at Willows Farm 6 Ammoniacal N numbers not provided in the AECOM assessment. Numbers used based on monitoring data from TSF1A
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