B-3 – Area 3 - Assessment of Environmental Effects 16 2.11 HYDROGEOLOGY The hydrogeology of the Area is described in GWS (2022a), a copy of which is provided in Part H of these application documents. The conceptual hydrogeologic model for the tunnel alignment generated by GWS (2022a) is provided in Figure 9. Figure 9: Conceptual hydrogeologic model for Area 3. The shallow groundwater system consists of surficial alluvium and younger volcanic material deposits with shallow groundwater flowing southeast from the Coromandel Ranges. GWS (2022a) consider that the Wharekirauponga Access Tunnel will not intersect the shallow groundwater system because the decline will be driven through an area that has already been dewatered to around 70 m below ground level by the existing Martha and Favona underground mines near the proposed tunnel portal. The deep groundwater system at Area 3 is within andesite, albeit the dewatering of existing underground mines near the Waihi SFA has also affected the deep groundwater system near the southern end of the tunnel corridor/portal. As such, fully saturated conditions will not be encountered until some point along the tunnel decline, beneath the shallow groundwater system. In the southern half of Area 3, groundwater flows toward the west (i.e., the tunnel corridor is perpendicular to the flows). A downward gradient is expected through much of the tunnel corridor, excepting an upward gradient near the Ohinemuri River. The Wharekirauponga Access Tunnel corridor is in the area identified by the WRP as the Waihi Basin aquifer management area. The groundwater consists of a shallow system at 0.5 m to 30 m deep, and a deeper system at more than 30 m below ground level.
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