GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North vi 6.3 WRS assessment 138 6.4 WRS analysis results 141 6.5 WRS effects summary and discussion 141 7. Conclusions and recommendations 145 7.1 Gladstone Open Pit and Tailings Storage Facility 145 7.2 Northern Rock Stack 146 7.3 Tailings Storage Facility 3 147 7.4 Willows Rock Stack 148 8. References 149 Table index Table 1.1 Key reference documents 14 Table 2.1 WRC surface water catchment information 19 Table 2.2 Regional geology presented units in Figure 2.4 21 Table 2.3 Existing consent compliance receiving water quality criteria (WRC, 1999) 25 Table 3.1 Stratigraphy of the Gladstone area 32 Table 3.2 Hydraulic Conductivity of geological units in shallow groundwater system 36 Table 3.3 Deep groundwater system well properties 38 Table 3.4 Groundwater takes and registered bores in the vicinity of the proposed Gladstone Pit 44 Table 3.5 Predicted change in groundwater table compared to current conditions and ZOI for GOP excavation 48 Table 3.6 Predicted change in Ohinemuri River flow compared to current conditions in Gladstone vein dewatering scenario 48 Table 3.7 Deep groundwater drawdown from current conditions and ZOI for Gladstone vein dewatering 48 Table 3.8 Estimated inflows to GOP from shallow groundwater system during GOP excavation 53 Table 3.9 Recorded Favona groundwater discharge and predicted GOP groundwater discharge 54 Table 3.10 Predicted groundwater discharge to surface water during GOP excavation 55 Table 3.11 Predicted change in surface water catchment areas during GOP excavation 55 Table 3.12 Predicted change in groundwater table compared to current conditions and drawdown ZOI after development of the TSF 56 Table 3.13 Estimated groundwater discharge to surface water bodies during operational TSF scenario 57 Table 3.14 Estimated groundwater discharge to surface water bodies during TSF closure scenario 57 Table 3.15 Estimated groundwater discharge to surface water bodies during long-term TSF scenario 57 Table 3.16 Estimated discharges from the pit area to surface water in the current conditions scenario, and from the TSF in the operational, TSF closure and long-term TSF scenarios 61 Table 3.17 Predicted change in surface water catchment area after TSF development 62 Table 3.18 Predicted flow to the deep groundwater system and TSF drainage system in the operational TSF and TSF closure scenarios 62 Table 3.19 Predicted receiving water quality in the Long-term TSF scenario (values in mg/L) 63 Table 4.1 Permeability of NRS geological units 76
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