GHD | Oceana Gold (New Zealand) Limited | 12537997 | Gladstone Pit TSF 27 Figure 16 Total liner area versus elevation for the GOP TSF 4.5 Storage capacity Figure 17 shows the tailings storage vs elevation curve for the GOP TSF. The total storage is 2.1 Mt up to RL 1103 m, assuming a density of 1.1 t/ m3 (conservative estimate due to relatively high rate of rise). The final tailings level of RL 1103 m is approximately 4 m below the crest of the pit (at the lowest point on the western side). This accounts for design flood storage and freeboard requirements. Given the relatively small capacity of the GOP TSF and the high degree of uncertainty in the construction schedule, the GOP TSF should be considered a supplementary storage to the other TSFs on site. Relying solely on the GOP TSF would present a significant risk to the continuity of operations. Directing a smaller fraction of the total tailings stream to GOP TSF assists in limiting the rate of rise and improving consolidation of the tailings. Reducing the rate of rise will improve with closure of the GOP TSF by improving trafficability of the final tailings surface and limiting excessive post-deposition settlement. The filling of GOP TSF is proposed to occur in two stages with Stage 1 being to RL 1080 m and Stage 2 to RL 1103 m. The advantages of staging filling (and construction) are: – Deferral of capital expenditure. – Increased scheduling flexibility – Enables filling of GOP TSF to commence earlier 1055 1060 1065 1070 1075 1080 1085 1090 1095 1100 1105 1110 0 20,000 40,000 60,000 80,000 100,000 120,000 140,000 Elevation, RL (m) Total liner area (m2)
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