SECTION 6 Gladstone Open Pit and TSF 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 22 Figure 23 Gladstone Hill Conceptual Groundwater Model (From GHD 2022) Much like elsewhere in Waihi the groundwater system near Gladstone Hill consists of a shallow groundwater system in young volcanic and alluvium deposits and a deeper system within the andesite rockmass. The systems are separated locally through the presence of low permeability weathered layers. The andesite rockmass host to the Gladstone vein system is already dewatered for the most part due to the Favona underground mine. The vein system in the southwest is partly dewatered. 6.4 Summary of Effects Groundwater Inflows Groundwater inflows during dewatering are expected to be negligible (<10 m3/d) as the rockmass is mostly dewatered already due to mining at Favona. This value may increase nominally if horizontal drainage is required to stabilise the pit. Drawdown Extent As Gladstone Hill is largely dewatered already the extent of drawdown associated with development of the pit will be limited beyond that which presently exists. Where some change in groundwater levels or pressures is expected is on the south western side of the pit where the vein system is not presently dewatered as shown in Figure 24. At that location the vein is projected to run beneath the Ohinemuri River at depth where is is overlain by young volcanics and alluvium as shown on Figure 25.
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