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 6 Characterisation of the area to date has included: - 116 drill holes and 47,600 m of drilling undertaken to characterize the geological conditions - Nested vertical stand pipe piezometers - Vibrating Wire Piezometer tips x3 in inclines holes - Permeability testing – falling head and straddle packer - Groundwater sampling and analysis (chemical and dating) - Permanent gauging stations - High resolution flow gauging events - Surface water sampling and analysis (chemical and dating) Further work is planned during the consent processing period with the focus to better understand the transient behaviour of groundwater and surface water interaction. Additional piezometers and permeability testing will be undertaken and that information incorporated into a 3 dimensional numeric groundwater model (by FloSolutions) to better understand the effects of mine dewatering in the near surface. This further information will also be used to test mitigation options (Valenza Engineering) should the modelling indicate this is necessary to prevent near surface effects. 2.3 Hydrologic and Hydrogeologic Setting The overall hydrogeologic setting is best illustrated through conceptual models. The Otahu is has a catchment of approximately around 70 km2 and drains to the east. The WKP Wharekirauponga subcatchment area is approximately 14.5 km2. The area of potential effect from mine dewatering is constrained to where the Rhyolite host rocks are exposed at the surface, this is around 1.5 km2 or 2% of the catchment surface with this extent is shown on Figure 8. Figure 8 Extent of Rhyolite Surface Exposure within the Otahu Catchment
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