GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 37 . result in groundwater discharge to the intermittent watercourses upgradient of the Gladstone Wetland. More typical downward hydraulic gradients indicate that some minor recharge of the deep groundwater system is occurring. Under-drainage of the shallow aquifer is most evident in the GLD01 series of monitoring wells, where the deepest well (GLD01b), screened within breccia/weathered andesite (separating the shallow and deep groundwater system), is typically found to be dry. Piezometric maps for the Gladstone site are provided in Appendix C, presenting groundwater levels in the shallow water table bores installed in the ash/regolith and dacite units, and piezometric contours within the RT and deeper section of the dacite unit. Vertical hydraulic gradient directions and flow/discharge locations in relation to the Ohinemuri River and its tributaries are included in both figures. All groundwater monitoring wells in the shallow groundwater system are installed within 33 m of the ground surface, typically within weathered, fractured volcanic flows and/or volcaniclastic sediments. Figure 3.7 Groundwater levels in the shallow system on southern flank of Gladstone Hill* * The pressure transducer in GLD02a was not installed below the water table during the full monitoring period. 3.3.3 Deep groundwater system Groundwater flow within the andesite rock underlying the shallow groundwater system is predominantly through secondary porosity features, with the vein system providing sub-vertical conduits for groundwater movement (URS, 2003). Away from fault zones and vein systems, the deep rock mass has very low permeability resulting in limited hydraulic connectivity between fault zones.
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