Supporting Technical Assessments

GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project 39 Area Predicted Decant TSF1a Predicted Decant TSF2 Predicted Decant TSF3 Predicted Decant GOP Predicted Seepage TSF1a Predicted Seepage TSF2 Predicted Seepage TSF3 Predicted Seepage GOP Data Source AECOM 2022 AECOM 2022 AECOM 2022 AECOM 2022 AECOM 2022 AECOM 2022 AECOM 2022 AECOM 2022 Parameter Mean 95th %ile Mean 95th %ile Mean 95th %ile Mean 95th %ile Mean 95th %ile Mean 95th %ile Mean 95th %ile Mean 95th %ile pH 8.09 7.52 7.66 7.20 8.09 7.60 8.09 7.60 6.69 11.4 6.15 7.27 6.69 7.60 6.69 7.60 TSS - - - - - - - - - - - - - - - - Ni 0.08 0.358 0.002 0.005 0.022 0.1 0.013 0.058 0.013 0.018 0.004 0.01 0.004 0.005 0.002 0.003 Cd 0.0003 0.001 0.0002 0.0002 0.0003 0.001 0.0001 0.0002 0.0003 0.0003 0.0002 0.0002 0.0003 0.0003 0.0001 0.0001 Se 0.05 0.05 0.001 0.001 0.06 0.12 0.07 0.13 0.004 0.006 0.001 0.001 0.005 0.007 0.005 0.008 Cu 1.77 6.98 0.001 0.003 0.450 1.780 0.470 1.858 0.002 0.01 0.002 0.008 0.001 0.002 0.001 0.003 As 0.0001 0.044 0.00002 0.00003 0.002 0.023 0.003 0.03 0.006 0.008 0.004 0.012 0.033 0.088 0.033 0.087 Pb 0.021 0.012 0.003 0.003 0.003 0.01 0.002 0.008 0.002 0.008 0.003 0.003 0.003 0.007 0.002 0.005 Sb 0.047 0.073 0.0003 0.0004 0.038 0.059 0.038 0.059 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 0.0002 Al 0.015 0.032 0.027 0.051 0.019 0.040 0.019 0.04 0.007 0.008 0.012 0.01 0.009 0.01 0.009 0.01 Hg 0.0002 0.0004 0.0001 0.0001 0.0002 0.001 0.0002 0.0004 0.0001 0.0001 0.0002 0.001 0.0002 0.0002 0.0001 0.0001 CN_Tot 0.74 2.70 0.74 2.70 0.74 2.70 0.74 2.70 0.020 0.126 0.020 0.126 0.020 0.126 0.020 0.126 Zn 0.268 0.887 0.002 0.006 0.01 0.033 0.009 0.030 0.026 0.064 0.004 0.01 0.001 0.002 0.001 0.002 SO4 1,275 2,350 116 179 1,070 1,970 1,060 1,940 541 592 120 342 450 490 450 490 Fe 0.050 0.101 0.021 0.020 0.031 0.064 0.029 0.059 20.4 23.2 5.06 10.51 12.9 14.7 11.9 13.5 Mn 1.09 4.34 0.064 0.271 0.265 1.057 0.172 0.688 8.19 9.46 3.48 8.22 1.99 2.3 1.3 1.5 Na 207 227 91.1 248 244 268 252 277 207 227 91.1 248 240 270 250 280 Mg 15.4 43.8 7.29 10.4 3.51 9.97 2.07 5.88 25.8 28.6 8.51 15.3 5.87 6.50 3.46 3.83 K 50.7 77.4 2.74 3.63 41.9 63.9 43.5 66.5 15.5 17.5 7.588 10 12.8 14.5 13.3 15.1 Co 0.077 0.215 0.0004 0.001 0.023 0.064 0.013 0.038 0.153 0.187 0.095 0.253 0.046 0.056 0.027 0.033 Ca 269 480 35.0 47.6 121 216 121 215 48.9 52.9 19.8 51.3 22.0 23.8 21.9 23.7 NH3-N6 11 38 11 38 11 38 11 38 1.8 2.2 1.8 2.2 1.8 2.2 1.8 2.2 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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