GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 10 A.3 2017 Drilling programme Well installation A total of 46 groundwater monitoring wells were installed between 10 May 2017 and 27 October 2017 in the vicinity of the new mine components: – 31 wells installed by GHD. – 15 wells installed by EGL. Core was recovered using HQ coring method, and 32 mm PVC piezometers (with machine slotted screens) were installed in the 96 mm diameter boreholes. The detailed lithology and well construction detailed are provided in the Appendix B bore logs. The wells were generally installed as paired units, where deep wells are denoted by an “a” in the well ID label. In some locations where existing OGNZL wells were present, an adjacent well was installed to act as the paired (or third) well (e.g as shown in Figure A.1). Where used, the existing wells are included in the groundwater monitoring data (Appendix C). Figure A.1 Three wells showing older OGNZL well pair (shallow DH05 and deeper well DH05A) and GHD intermediate well (WRS06) Well survey Each well was surveyed by OGNZL to the Old Cadastral Mt Eden Coordinates and Martha Mine elevation datum, which is presented in metres reduced level (mRL). The full list of these wells including level survey results are summarised in (Appendix B). The locations of all wells used in the assessment are provided in figures within the report. Well development Following installation, and prior to monitoring and/or testing, the installed wells (and any OGNZL wells used in the programme) were developed using the most suitable purging methodology per well (i.e. total depth, water level,
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