GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 15 . Key assessment description Report Title and Reference TSF3 design and civil engineering-related effects: Technical report prepared for resource consent, including preliminary TSF3 design for the assessment of environmental effects (including the potential for ground settlement associated with construction dewatering). EGL, 2021b: Tailings storage and rock disposal – Volume 3. Proposed tailings storage facility – Storage 3 RL155 Technical Report (WAI-985-000-REP-LC-0004) WNP geochemistry analysis: Geochemical study of the ore, tailings, and overburden expected to be recovered from the proposed mine areas, and to assess the potential influence these materials may have on the environment. AECOM, 2021a: Waihi North Project Geochemical Assessment – Geochemistry of Tailings and Overburden, Treatment and Mitigation (WAI-985-000-REP-LC-0038_RevB.1). TSF3 geotechnical factual report: Extensive site investigations to characterise site conditions for TSF3. EGL, 2018: Waihi Mine Storage 3 – Geotechnical Factual Report (EGL ref. 8332, Draft Rev A) NRS geotechnical factual report: Extensive site investigations to characterise site conditions for NRS. EGL, 2019a: Waihi Mine Northern Rock stack – Geotechnical Factual Report (EGL ref. 8332, Draft) 1.3 Scope The key objectives of this hydrogeological study are to: 1. Understand dewatering requirements and effects: Dewatering is required for TSF3 construction and a minor section of NRS construction. Excavation of the GOP will also result in groundwater drawdown within the surrounding groundwater system. The assessment provides potential inflows for water management considerations, and an assessment of potential dewatering effects on groundwater levels and surface water. 2. Assess the life of mine and post-closure (long-term) influence on the environment: WNP introduces new mine components that have the potential to influence groundwater and surface water through changes in groundwater levels, groundwater flow and/or water quality. An assessment relating to these potential effects has been undertaken (where applicable) for each of the key project components being considered. WRS is only considered for operational scenario, as it is intended to be a temporary storage facility. 3. Inform monitoring and management requirements: Where potential effects to the environment are identified in the assessment, appropriate monitoring and management approaches are provided as recommendations, for the purpose of allowing validation of the assessment predictions and monitoring of the potential for adverse outcomes. The studies included a range of extensive site investigations to characterise existing environmental conditions. 1.4 Report structure The body of this report provides summaries of key aspects of the assessment, with more detailed information and technical assessment provided in appendices. This report is structured as follows: – Section 2 – Background and environmental setting: Broad overview of the site setting (geology, groundwater surface water) as it relates to the proposed activity. – Sections 3 to 6 – Assessment of each new mine component: Separate hydrogeological assessment of each key project component (GOP, NRS, TSF3, and WRS, respectively). Supporting technical information for this assessment is provided in the following appendices. Appendix A: Site investigation methodology Appendices B-F: Outputs of the site investigation works (e.g. bore logs, groundwater levels, permeability data, water quality, water flow. Appendix G: GOP and TSF detailed technical assessment. Appendix H: NRS detailed technical assessment.
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