GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 12 A.5. Aquifer testing Testing at selected well locations was carried out using falling and rising head methodologies??, to obtain the hydraulic conductivity of the screened well sections. The methodology involved the lowering and raising of solid PVC slugs below the groundwater level to displace the water. Lowering of the slug/s provided a falling head test; and raising the slug/s out of the water provided a rising head test. The groundwater level response for each test was recorded using a pressure transducer. The resulting displacement curve for each tests was analysed using Aqtesolv (version 4.5) and AquiferWin32 aquifer test software to provide an estimate of the hydraulic conductivity (K). The test results are provided in Appendix D. A.6 Water quality sampling Sample methodology Groundwater quality sampling was carried out over December 2017 and January 2018 in selected wells across the site. Locations within each area were selected in relation to proximity of the proposed activities (upgradient, downgradient) and intended for monitoring before (baseline), during, and after completion of the proposed activities. Numerous wells and surface water locations were selected for sampling/monitoring and are listed in the tables in Appendix E. Sampling was carried out using standard low flow purging methodology (EPA 1996a and EPA 1996b), where the formation recharge and groundwater depths allowed. Where recharge was too slow and/or the groundwater level was too deep, more suitable alternative methods were used, which included purging the well until dry and using low flow methodology to collect recharge water, or the use of HydrasleevesTM. Sample analyses The parameters that each sample was analysed for are listed in Table A.1 below. All sites (where possible) were analysed at least once for the comprehensive suite before changing to a reduced suite. Interpretation of water quality is provided in Appendix E. Table A.1 Analytical suites Comprehensive Suite pH Electrical Conductivity (EC) Total Suspended Solids Total Alkalinity Major Cations and Anions Dissolved metals (As, Cd, Cr, Cu, Fe, Pb, Mn, Ni, Sb, Se, Ag, Zn) Dissolved Mercury WAD Cyanide Distillation Weak Acid Dissociable (WAD) Cyanide Nutrient Suite (TN, TKN, NO2-N + NO3-N, Amm-N) A.7 Stream flow gauging Opus carried out stream flow gauging on behalf of OGNZL between January 2019 and January 2020 at GHD’s request. Stream flow gauging was carried out once every two weeks from late January until end of March to capture baseflow conditions, with subsequent monitoring carried out quarterly. The gauging reports and results summary are provided in Appendix F.
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