GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 54 . Figure 3.15 Favona pumping discharge plotted alongside mine depth and estimated groundwater inflow (GWS, 2018a) Table 3.9 Recorded Favona groundwater discharge and predicted GOP groundwater discharge GOP phase of excavation Average daily groundwater discharge (m3/day) Recorded during Favona dewatering (m3)(1) Predicted during GOP excavation Initial excavation to maximum depth 2,200(2) 1,100 Long-term groundwater inflow 650(3) 325 Notes: 1. Favona discharge based on results presented in Figure 3.15. 2. Average of 2006 and 2007 daily discharge, as mine depth of 1,005 mRL was reached at the end of 2006. 3. Groundwater inflow estimated by GWS (2018a) when mine depth reached 1,005 mRL. The results from the groundwater model developed for the Gladstone vein dewatering assessment indicate that approximately 11 m3/day of long-term groundwater inflow will occur from each 1 m section where maximum groundwater drawdown to 1,005 mRL occurs within the Gladstone vein. Assuming a linear relationship of drawdown with distance, and using the predicted groundwater inflow derived from the Favona data, this indicates that unsaturated andesite along the strike of the vein will extend approximately 60 m. This is a smaller extent than predicted in Figure 3.14 and demonstrates the conservatism of the groundwater modelling assessment. The actual inflow rates likely to be experienced are notably lower than 11 m3/day per 1 m section along the strike of the vein. The extent of unsaturated andesite perpendicular to the vein strike modelled during the vein dewatering assessment (Table 3.7 and Figure 3.14) is therefore also considered to represent an upper bound.
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