SECTION 2 Wharekirauponga Underground Mine C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WUG Effects Summary\June 2022\WNP Groundwater Effects Summary_Final_Rev_0.docx 8 convection. These deep fluids are mixed with shallow groundwater that reduces the temperature of the water to around 20 degrees. Figure 11 Wharekirauponga Conceptual Groundwater Model Where post mineralisation andesite is present at the surface, a shallow groundwater system exists perched over the rhyolite rockmass as shown on Figure 8. Beneath this, the groundwater level in the rhyolite rockmass and Tewaotemutu Stream veins is interpreted to be near stream level, being partially to fully dewatered due it its relatively high permeability. The EG vein is not dewatered and the interaction between that part of the vein system and surface waters is still the subject of further ongoing studies. 2.4 Summary of Effects This summary of effects represents the level of knowledge and assessment at the time of preparation. Further work is ongoing in relation to these matters to provide greater certainty of the effects that might develop. Groundwater Inflows From work undertaken to date, mine inflow volumes are expected to be in the order of some 5,200 m3/d initially, reducing to 2,400 m3/d over time. This groundwater would be pumped back to Waihi via the tunnel system for treatment and discharge via the Ohinemuri River. The water take exports groundwater from the Otahu catchment to the Wairoa Catchment. Drawdown Extent The potential envelope of drawdown effects has been determined through groundwater modelling and is shown in Figure 12. In summary, the drawdown effects associated with the proposed mine dewatering are limited to developing around the EG vein system.
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