www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 22 5.3.6. EGV GROUNDWATER SYSTEM Packer tests holes distributed along the area of the EGV include WKP-102, WKP-04D, WKP-101, WKP103, and WKP-105. Shallow piezometers WKP-01 and WKP-02 are also located in the central part of the EG vein system. The distribution of packer test permeabilities in relation to the vein system and geology is shown in Figure 5-3. Figure 5-3: Schematic cross section of WKP-102 and WKP-04D (left) and WKP-101 and WKP-103 (right) (after FloSolutions) The following observations are made: • Hydraulic conductivity values range from 5.8E-8 to 9.1E-6 m/s. • Tests in the footwall of the EGV may have lower K values compared to the hanging wall dependent on the presence of relatively unaltered rhyolite and gouge-filled faults in the footwall. The contact between the rhyolite dome and the volcanoclastic formation may indicate a groundwater flow pathway. • The shallow sections west of the hanging wall EGV have low hydraulic conductivity values. • The eastern part of the EGV aquifer system appears well connected, with relatively moderate to high permeabilities and consistent water elevations across a wide range of test locations, depths, and lithologies confirming that the EG vein aquifer is hydraulically connected across the test zones. • The western portion of the shallow groundwater system is hydraulically disconnected from the EGV aquifer. • The western part of the EGV shows a step-like change in water level elevation suggesting a compartmentalised shallow groundwater system. Low permeability veins may form barriers to groundwater movement and unsaturated conditions may result. • Two tests in the stockwork zone experienced a big water intake during testing, and higher K values have been calculated in this zone (7.8E-6 and 6.9E-6 m/s). • Water levels are relatively consistent at all test locations and depths in the central EGV, ranging from 109 to 137 masl. • Drilling water losses appear concentrated at the contact between the rhyolite dome and the volcanoclastics.
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