50 Oct 2021 OceanaGold WNP Project, Waihi - Archaeological / Heritage Assessment TAILINGS STORAGE FACILITY 3 (TSF3) The Proposal The proposed TSF3 will provide the tailings storage for the WNP in addition to that provided by the proposed GOP TSF. TSF3 is a downstream earth and rockfill embankment structure, like TSF1A and 2, and forms an impoundment to store the discharged slurry tailings pumped from the Processing Plant. The proposed crest height for the embankment is RL155, forming a 46m high embankment above the existing ground at the downstream toe (RL109). The layout of TSF3 to RL155 is shown in Figure 47. This shows the TSF3 downstream embankment constructed between the existing TSF1A embankment and the rising hills to the east which wrap around to the north and behind TSF1A to form the impoundment. The impoundment partially covers the existing East Stockpile area. The total footprint of TSF3, including the extent of the stockpile and uphill diversion drain, is approximately 115ha. Of this area 20ha is already part of the existing footprint of TSF1A and East Stockpile. The new footprint is therefore 95ha. This area includes the stockpile areas, the new embankment and impoundment areas, collection ponds, the uphill diversion drain and area between the impoundment and the uphill diversion drain. A haul route will be established down the East Stockpile. This will extend the existing haul route behind TSF1A and 2, linking those areas to the existing stockpiles and conveyor loadout. Topsoil stripping will be required over an area of approximately 80ha. This includes approximately 5ha on the existing TSF1A embankment. Stripping of topsoil will be undertaken in stages as required. Clean run-on water from the hills above the TSF will be diverted around the facility to the Ruahorehore Stream. This diversion will be an extension to the existing Southern Uphill Diversion Drain which currently starts behind TSF1A and runs behind the East Stockpile. The length of the new section of Southern Uphill Diversion Drain is approximately 2950m.
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