Oceana Gold New Zeland Limited Hydrogeology Support for WKP Underground Updated Conceptual Model The following observations inform our conceptualization: In the WKP04D / WKP-102 section in the north where quartz stockworks and transverse veins are not well developed, K values are between 1E-5 m/s and 1E-6 m/s but are lower in the footwall (less than 1E-6 m/s). Consistent water levels in tests indicate a connected EG vein aquifer system in this section. In the WKP-101 / 103 section in the south-central part of the deposit, K values are moderately high (> 1E-6) from the hanging wall EG-West veins all the way through to footwall veins, and are generally in the range of 1E-5 m/s to 1E-6 m/s. Consistent water levels in all tests indicate a connected EG vein aquifer system in this section. In the south- central part of the EG vein near WKP-101 / 103, there is separation between the shallow aquifer and the deeper vein aquifer. HW-EG-West veins appear to serve as a flow barrier, compartmentalizing groundwater and hydraulically isolating shallow groundwater west of the veins from the EG vein aquifer east of the veins. Numerous water losses have been reported in the shallow portion of the holes in all sections, with few water losses below the elevation of the vein aquifer water level. This suggests that an unsaturated zone may be present between the surface aquifer and the deeper vein aquifer in some areas (needs further evaluation). Some shallow tests outside of vein systems record water levels at or above ground level, suggesting locally confined conditions in the shallow aquifer. Rhyolite outside the vein domain presents lower K when compared to the rock mass along the vein system (~ one order of magnitude lower). Water losses have been reported in the contact between the Rhyolite Volcaniclastics and Rhyolite Flow Dome, indicating a possible flow pathway. There are some important implications to these observations. First, the permeability of the EG vein and surrounding rocks and calculated water levels indicate a well-connected aquifer system. Similar water levels (relative to topography) in the WKP04D/WKP-102 section and WKP-101 / WKP-103 sections indicate that the aquifer is fully connected along strike in the area investigated. Drawdown during mining will probably propagate longitudinally along strike. There is potential to impact on any streams or shallow groundwater north or south of the currently-defined strike limits of the EG vein if it continues in these directions. Second, the HW-EG-West vein system is conceptualized as a flow barrier. Presence of HW-EG-West veins will likely limit any mining-induced drawdown in the EG vein aquifer from propagating to the west, essentially protecting shallow groundwater and streams in these areas from mining impacts. It is in therefore in OGNZL further define the full longitudinal extent of the HW-EG-West vein system to the north and south. Shallow groundwater conditions directly overlying the EG vein system are currently unknown. This is considered a key data gap in the site conceptualization.
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