GHD | Oceana Gold (New Zealand) Limited | 12537997 | Gladstone Pit TSF 23 4. Development of GOP TSF 4.1 General This section provides a summary of the GOP tailings storage facility design, including the geometrical arrangements, material zoning and proposed construction methodology. The design drawing set is provided in Appendix A. This includes general arrangements, typical sections and details. 4.2 Facility geometry This section provides explanation for the geometric arrangement of the pit backfill and lining. A summary of the facility geometry is provided in Table 4, including justification for the selected values where required. Table 4 GOP TSF geometric arrangement Parameter Value Justification Backfill bench width 10 m Minimum width for safe working during liner installation and hauling/spreading backfill. Backfill bench height 10 m Maximum height for limiting strain and elongation of liner. To be confirmed during detailed design. Backfill batter slope 1.5H:1V (33.7) Upper limit slope for installation of a geomembrane liner. Upper limit selected to reduce backfill quantity and increase tailings capacity. Minimum pit crest (RL) 1107 m As designed by OGNZL Maximum tailings level (RL) 1103 m Allows for storage of the operating pond plus the PMP plus freeboard for wave-runup. Tailings storage floor (RL) 1060 m Geometric constraint to still allow a reasonable area in the floor once backfill is placed. Maximum depth of tailings (m) 43 m Based on pit geometry and maximum tailings level 4.3 Materials and zoning Figure 12 shows a typical section through the GOP TSF and Figure 13 shows an isometric view of the facility. The GOP TSF has been designed as a fully lined facility. The TSF features a backfill component to facilitate lining of the pit. The backfill consists predominantly of run of mine (ROM) waste rock with a 2 m wide external facing of processed, sub-20 mm material to provide a cushioning layer to support the liner and act as a drainage layer beneath the liner.
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