SECTION 4 Assessment of Effects C:\D Data\GWS C Drive\GWS\Client Files\1344 OGL - WKP\4 Deliverables\WKP Final Draft Report\June Report\WAI-985-000-REP-LC-0030. Final_Rev_0.docx 32 vein is dewatered, the surrounding Rhyolite flow rock dewaters where it is exposed at the surface, however, the overlying Andesite rock does not dewater. Figure 28 EG Vein Groundwater Model Result Output (Blue Line is the Water Table) The extent of the Rhyolite dewatering is largely a function of the amount of fracturing and the degree of silicification (i.e. permeability). In summary, the extent of dewatering in the rockmass is controlled by the assumed permeability and this is undergoing further testing and sensitivity analysis as part of the 3D numerical modelling work. An initial determination of the worst-case drawdown effects has been undertaken by Flosolutions (5th April 2022) using an analytical model AnAqSim. This model simulates variable rockmass and vein system permeability at different elevations. This modelling indicates up to 22 m of drawdown could develop assuming an unmitigated scenario where dewatering effects develop as a result of mine drainage. The magnitude of the drawdown effects is controlled by the aquifer properties, but also the assumed stream bed conductance. The drawdown profile presented in Figure 29 has been used to assess ground settlement effects calculated in the EGL Ground Settlement report (WAI-985000-REP-LC-0050).
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