WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. 1.0 INTRODUCTION Engineering Geology Ltd (EGL) has been appointed by OceanaGold (New Zealand) Limited (OGNZL) to undertake a technical report for the proposed Storage 3 Tailing Storage Facility (TSF) for resource consent for the Waihi North Project (WNP). The proposed embankment dam with a crest level to RL155 (RL, Reduced Level in Mine Datum less 1000m) will be achieved using downstream construction methods. A locality plan for WNP is provided in Figure 1. This technical report has been prepared for resource consent and details a preliminary design for the assessment of environmental effects as required under the Resource Management Act 1991. This report is Volume 3 of a 4-part series of reports prepared on the tailings and rock disposal for Waihi North Project (WNP). Volume 1 is an overview of the tailings and rock disposal strategy (Ref. 1), Volume 2 is a technical report on Gladstone Open Pit (GOP) TSF (Ref. 2) and Volume 4 is a technical report on the Northern Rock Stack (Ref. 3). Elsewhere in the project documentation the proposed Storage 3 TSF is referred to in short as ‘TSF3’. The new Storage 3 TSF is proposed to provide the tailings storage for the WNP in conjunction with the proposed GOP TSF. Storage 3 has been selected and compared against a range of options summarised in the Tailings Storage and Rock Disposal - Natural Hazard and Option Report (Volume 1 – Ref. 1). Design for the construction of Storage 3 will be undertaken in accordance with the recommendations and guidelines of the New Zealand Society on Large Dams (NZSOLD) ‘New Zealand Dam Safety Guidelines’ (NZDSG - Ref. 4). Storage 3 is to be designed as a High Potential Impact Classification (PIC) dam. 2.0 BACKGROUND AND CURRENT SITE FACILITIES 2.1. Location and existing TSFs There are two existing TSFs at the Waihi Operation, Storage 1A and Storage 2. They are shown in Figure 2 along with other site features. Storage 1A crest is at RL174.8 as of April 2021 and has resource and building consent to be raised to RL182 (Ref. 5). Storage 3 site was previously investigated as a potential TSF location at the time the Development Site was first investigated, however, preference was given to Storage 2 and 1A locations which are closer to the Process and Water Treatment Plant. The location and the layout of the Waihi operation are shown in Figures 1 and 2. Trevor 23 June 2022 OCEANA GOLD (NEW ZEALAND) LTD TAILINGS STORAGE AND ROCK DISPOSAL VOLUME 3 PROPOSED TAILINGS STORAGE FACILITY STORAGE 3 RL155 TECHNICAL REPORT EGL Ref: 8983
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