Supporting Technical Assessments

GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North vii Table 4.2 Water takes in the vicinity of the proposed NRS 81 Table 4.3 NRS groundwater inflow rates and distance of influence of dewatering for uphill diversion drain construction 82 Table 4.4 Predicted leachate capture and leachate seepage through zone A liner 83 Table 4.5 Predicted groundwater and leachate captured in sub-soil drains 83 Table 4.6 Predicted groundwater and leachate captured in sub-soil drains 83 Table 4.7 Predicted receiving water quality in the NRS closure scenario (values in mg/L) 87 Table 5.1 Description of TSF3 construction materials 96 Table 5.2 Stratigraphy of the TSF3 area 98 Table 5.3 Summary of hydraulic conductivity Values for TSF3 103 Table 5.4 Nearest TSF3 groundwater users 107 Table 5.5 Nearest surface water users 107 Table 5.6 Summary of dewatering results 111 Table 5.7 TSF3 tailings porewater discharge 114 Table 5.8 TSF3 rock embankment infiltration* 116 Table 5.9 Predicted drain capture volumes and sources 117 Table 5.10 TSF3 seepage as a proportion of groundwater flow 121 Table 5.11 Ruahorehore Stream flow rates 122 Table 5.12 Actual and predicted groundwater quality concentrations (mg/L) 123 Table 5.13 Ohinemuri River water quality (values in mg/L) 124 Table 5.14 Mean predicted mass flux (kg/day) from TSF3 to the Ohinemuri River 124 Table 5.15 Ruahorehore Stream water quality (values in mg/L) 125 Table 6.1 Flow gauging measurements (WSP 2021a and 2021b) 131 Table 6.2 Vertical hydraulic gradients 132 Table 6.3 Hydraulic conductivity values 133 Table 6.4 Mataura Stream water quality (values in mg/L) 143 Table 6.5 Predicted mass flux (kg/d) to the Mataura Stream 143 Figure index Figure 1.1 Waihi North Project general project area (OGNZL, 2021a) 12 Figure 1.2 Plan of Willows Road Farm infrastructure (Mitchell Daysh, 2022) 13 Figure 1.3 Proposed expanded Waihi Operations 13 Figure 2.1 Key geographic features of the southern WNP site 17 Figure 2.2 Wharekirauponga Portal Location 18 Figure 2.3 Regional geology and structural domains (from GWS, 2018a) 20 Figure 2.4 Geology of the WNP area (OGNZL, 2017; GNS, 1996)* 20 Figure 2.5 WRP Aquifer Map 7 (Waihi Basin) 22 Figure 2.6 OGNZL surface water monitoring network 24 Figure 3.1 Gladstone site setting and monitoring locations 28 Figure 3.2 GOP footprint and site layout (Mitchell Daysh, 2022) 30 Figure 3.3 Gladstone geological section (A-A’ of Figure 2.4) (URS, 2003)) 31 Figure 3.4 Gladstone cross-section locations (N-S and W-E) 33 Figure 3.5 North-south model cross section 34 Figure 3.6 West-east model cross section 35 Figure 3.7 Groundwater levels in the shallow system on southern flank of Gladstone Hill* 37 Figure 3.8 Gladstone registered bores, groundwater takes and mineralised vein system 39

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