Supporting Technical Assessments

GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North viii Figure 3.9 Groundwater levels in the shallow (P79s & P79i) and deep (P79d) systems southwest of Gladstone Hill and surveyed Ohinemuri River level at OH6 40 Figure 3.10 Deep groundwater levels (m above mean sea level) and flow direction recorded in 1983 (GCNZ; year unknown - modified to show approximate Gladstone location) 41 Figure 3.11 Gladstone and NRS surface water and groundwater takes 45 Figure 3.12 GOP excavation results 50 Figure 3.13 Gladstone vein dewatering assessment perpendicular to vein strike – groundwater levels for current conditions and Gladstone vein dewatering scenarios 51 Figure 3.14 Gladstone dewatering zone of unsaturated andesite 52 Figure 3.15 Favona pumping discharge plotted alongside mine depth and estimated groundwater inflow (GWS, 2018a) 54 Figure 3.16 Operational TSF results 58 Figure 3.17 TSF Closure results 59 Figure 3.18 Long-term TSF results 60 Figure 4.1 NRS site setting and monitoring locations 71 Figure 4.2 NRS proposed location and greatest extent during operation (Mitchell Daysh, 2022) 72 Figure 4.3 NRS geological cross-section (B-B’ of Figure 2.4) (OGNZL, 2017) 73 Figure 4.4 NRS geological long-section B-B (2508) from EGL (2019a) 74 Figure 4.5 NRS 2017 groundwater and Ohinemuri River (OH3) levels and rainfall (CLIFLO Athenree 2 station 18638). Monitoring locations presented in Figure 4.1. 77 Figure 4.6 NRS 2020 groundwater and TB1a stream levels and rainfall (CLIFLO Athenree 2 station 18638). Monitoring locations presented in Figure 4.1. 78 Figure 4.7 TSF2 and existing northern stockpile underdrains and sampling locations (OGNZL, 2016) 80 Figure 4.8 NRS leachate balance 84 Figure 4.9 NRS groundwater and leachate captured in sub-soil drains 84 Figure 4.10 NRS operation scenario predicted leachate and groundwater flow paths for 30% and 50% rainfall recharge 85 Figure 4.11 NRS Closure scenario predicted leachate and groundwater flow paths 86 Table 4.8 Predicted mass flux to the Ohinemuri River during operation of the NRS (50% rainfall recharge) 88 Figure 5.1 TSF3 site layout plan showing the Ruahorehore Steam Catchment (red) upstream of the embankment toe 93 Figure 5.2 TSF3 site setting and monitoring locations 94 Figure 5.3 TSF3 layout plan to 1,155 mRL (EGL, 2021b) 95 Figure 5.4 TSF3 embankment construction showing material zones 96 Figure 5.5 TSF3 geological section (C-C’ of Figure 2.4) (from OGNZL, 2017) 97 Figure 5.6 East-west cross section of paleo-gully beneath the TSF3 site (EGL 1996 Longsection A-A’; refer to Figure 5.5) 99 Figure 5.7 Northeast-southwest cross section of paleo-gully beneath the TSF3 site (scale is approximately only) 100 Figure 5.8 Conceptual hydrogeological cross-section through the TSF3 paleo-gully 102 Figure 5.9 Summary of baseflow conditions at TSF3 104 Figure 5.10 TSF3 original topography showing western rhyolite ridge 106 Figure 5.11 Locations of Water users within 3 km of TSF3 108 Figure 5.12 TSF3 cross-section locations 110 Figure 5.13 Predicted groundwater level drawdown the undercut excavation (SEEP/W Cross-Section 1) 112

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