Supporting Technical Assessments

GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 60 Operational TSF, TSF Closure and Long-term TSF Groundwater discharges to each of the surface water bodies from the Gladstone Pit under current conditions and from the TSF during each TSF scenario are presented in Table G.14. The results have been estimated using the groundwater modelling methodology (G.1.1.1). The predicted changes in groundwater levels and the predicted groundwater zone of influence after development of the TSF are presented in Table G.15. The predicted shallow groundwater table during all assessment scenarios, are presented in Figure G.9. Table G.14 Predicted groundwater discharge from the pit area to surface water receiving environments under current conditions and after development of the TSF (SEEP/W) Pit section Estimated groundwater discharge to surface water from proposed pit area (current conditions) and from the TSF (TSF scenarios) (m3/day) Current scenario Operational TSF TSF closure Long-term TSF North (TB5) 0 0 0 0 East (OH3) 0 0 0 0 South (TB4) 0 0 0 0 West (OH6) 3.8 0 0 64.8 total (4.5 - Tailings porewater) Total 3.8 0 0 64.8 Table G.15 Predicted change in shallow groundwater level at the edge of the pit compared to current conditions, and zone of influence, after development of the TSF (SEEP/W). Orientation from Pit Operational TSF TSF closure Long-term TSF Groundwater drawdown at edge of pit (m) Zone of influence (m)* Groundwater drawdown at edge of pit (m) Zone of influence (m)* Groundwater drawdown at edge of pit (m) Zone of influence (m)* North 2.9 56 2.9 36 2.4 28 East 6.1 155 5.9 120 5.3 99 South 7.9 288 7.9 88 7.2 69 West 5.9 212 5.1 124 -2.1 - * Where drawdown > 0.5 m The predicted groundwater discharges to each of the surface water bodies after development to a tailings storage facility are presented in Table G.16, Table G.17 and Table G.18.

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