- Waihi North Project, Gladstone Pit – Geotechnical Assessment; 19 May 2022, prepared by PSM Consult Pty Limited (PSM). - Gladstone Pit TSF, Design Report; 30 May 2022, prepared by GHD Pty Limited (GHD). The Gladstone Open Pit works comprise the following earthworks components: - Removal of topsoil from the pit footprint and storage at the Southern Stockpile. - Establishing a portal to the Wharekirauponga Underground Mine (WUG). - Establishing a new MUG portal within the Gladstone Pit (the Gladstone Portal) or adjacent to the new WUG Portal, and in-pit crusher. - Excavation of ore and/or non-ore bearing rock. This SSESCP has been prepared in accordance with Waikato Regional Council Technical Report No. 2009/02 Erosion and Sediment Control Guidelines for Soil Disturbing Activities, January 2009 (TR2009/02) and addresses the following earthwork activities: • Establishment of the erosion and sediment controls; • General earthworks involved in the establishment of the pit; • Stockpiling; and • Conversion to an in-pit TSF upon completion of mining. The ESC measures proposed as part of this SSESCP will be used during the ‘enabling earthworks’ phase which does not include mining. Once mining activities occur the operational requirements commence, and contact water will report to the Water Treatment Plant. 2. DESCRIPTION OF WORKS Gladstone Open Pit will include earthworks over an anticipated area of 18.7ha and will be about 95m deep comprising 2.6Mt of ore and 18.7Mt of non-ore-bearing rock. The open pit mining operation will commence in Year 1 and will be completed in Year 6; at an average mining rate of 3.5Mt per year. Topsoil stripped from the pit footprint will be stored at the Southern Stockpile area which has a capacity of 52,500m3. Approximately 5Mt of rock will be used to partially backfill the pit in preparation for its use as a tailings storage facility. The GOP is proposed by be mined over six years (2024 – 2029). The tailings storage development is scheduled to begin in Q4 of 2029, with tailings Stage 1 and Stage 2 completed by Q4 2031. Gladstone Pit will then function as an operating TSF until the end of the year 2036. The construction sequence and methodology are described by OceanaGold which briefly includes the following stages: • Clearing of vegetation on Gladstone and Winner Hills; • Establishing clean water diversions and ponds required for sediment controls; • Stripping of topsoil at Gladstone and Winner Hills and storage at Southern Stockpile; • In parallel, relocation of site infrastructure i.e., the overhead powerline, new MUG portal cutback.
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