www.valenza-engineering.com 381_R_04_Rev 0 OGNZL_WUG_Phase1_Conceptual_Mitigation 21 • Shallow groundwater system behaviour and dynamics, and connections between deep and shallow systems. o Required for NM development. o Connection of EGV aquifer with HW-EG-West veins. o Barriers to flow from deep to shallow aquifer provided by HW-EG-West veins. o Confirmation of downward hydraulic gradients from shallow to deep. o Recharge mechanism and shallow groundwater rainfall response. • Deep groundwater system hydraulic properties. o Required for NM development. o Characterising EGV and T-Stream vein systems. o Indicated EGV K-values lower than hanging wall. o Characterising lithological controls on permeability (currently limited to a few types). o Host formation permeabilities are little understood. o EGV storage properties for inflow determination. • Water balance and recharge. o Characterising highly variable recharge over the project area (geology, soils, topography, vegetation). o Rainfall intensity and duration analyses. • Shallow groundwater monitoring. o Monitoring of near-field effects such as depressurisation of shallow groundwater adjacent to streams. o Monitoring of effects within the mining zone to allow additional mitigation measures to be implemented. 5.3.5. SHALLOW GROUNDWATER SYSTEM Data input is restricted to the two piezometer pairs, WKP-01 (S/D) and WKP-02 (S/D). • WKP-01 S/D pair. Water levels in the shallow bore appear to be unconnected to the deeper bore, which is mostly dry and suggests an unsaturated zone between the shallow aquifer and deeper groundwater. • WKP-02 S/D pair. Downward vertical gradients are interpreted as indicating continuous saturation. o WKP-02D responds more strongly to rainfall than other shallow bores and fluctuates over a 10 m range. o This may be due to its position at that contact of the rhyolite flow dome, where water losses have been observed during drilling, suggesting that the rhyolite flow dome contact may be capturing shallow interflow that would normally discharge downslope to streams.
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