Supporting Technical Assessments

GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 11 diameter). The methods used included: waterra footvalve combined with additional lift from a Honda WX10 Water Pump; Monsoon Pump; or airlift pump. A.4 Water level monitoring Groundwater level monitoring A series of groundwater level monitoring events were carried out, including: – Manual groundwater level measurements: These were collected either during dedicated groundwater level monitoring events, or as part of the earlier well development work, between June 2016 and 2020. The water levels are provided in metres below ground level (m bgl) and/or metres below top of casing (m btoc) and are converted to the Martha Mine datum (mRL). Refer to the tables provided in Appendix C for a summary of all manual measurement data. – Automated groundwater level measurements: Continuous water levels were recorded across the site using Solinst pressure transducers and a barologger to allow for atmospheric compensation. Selected locations were monitored across variable timeframes in mid-late 2017, depending on the following factors: equipment availability; site accessibility; comparison between locations; and assessment of rainfall event response. Manual measurements were used to calibrate the recorded water levels, which are presented in Appendix C. Surface water To support the assessment of the hydraulic connection between groundwater and the Ohinemuri River, surface water level monitoring stations were installed: – In the Ohinemuri River (Figure A.2) between the Favona and NRS sites and at TB1a. – Gladstone at one site (TB4). – TSF3 at several sites (RU6, RU7, RU13, RU15;). The locations and results are shown in Appendix F. Monitoring of each surface water level site was carried out using a solinst pressure transducer, and the river level was surveyed by OGNZL to Martha Mine datum. The survey level was used to calibrate the recorded river levels, which are presented in Appendix F. Figure A.2 Surface water level monitoring site installed in Ohinemuri River

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