GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 96 The collected drainage will be pumped from the leachate collection system and sent to the WTP. – Stages operational through to closure: Crest lifts in stages, including to 1,145 mRL (EGL TSF3 Figure 19 and DWG 512). Lift to the final facility height of 1,155 mRL (EGL TSF3 Figure 20 and DWGs 513-520). Capping of the embankment to minimise oxygen ingress (closure) (EGL TSF3 DWG 690). At 1,155 mRL (Figure 5.3, above), TSF3 will: – Have a new footprint of 95 ha. Of the total footprint (approximately 115 ha), 20 ha is already part of the existing footprint of TSF1A and East Stockpile. – Have an embankment crest 20 m-wide and a total length of 1,000 m. – Have three lined (HDPE) collection ponds (S4, S6 and S7) downgradient of the facility. – Be 46 m in height above the toe at 1,109 mRL. – Contain up to 6 Mm3 of tailings material. To achieve the design objectives of TSF3 (outlined in the EGL 2021 technical report) the rock embankment will be designed as a zoned structure as shown in Figure 5.4. The primary functions of the different zones are summarised in Table 5.1. Figure 5.4 TSF3 embankment construction showing material zones Table 5.1 Description of TSF3 construction materials Material name Description Zone A* Low permeability zone (earth liner) underneath the full facility that restricts seepage from mine overburden material into underlying ground Zone B Low permeability upstream zone that restricts seepage from the tailings Zones C1 and C2 Structural fill zones that provide support to Zone B and provide a transition between the finer grained material in Zone B and the coarser material in Zones D2 and D3 Zones D2 and D3 Bulk fill zones with less restrictive requirements than other zones. Zone D2 has a higher strength specification than Zone D3. Zone E Specified zones for the weakest material (not shown in Figure 5.4)** Zone F Structural fill zone on outside shoulder that also provides a transition between the coarser material in Zone D and finer material in Zone G. Also provides a drainage path for leachate. Zone G* Outer sealing layer of the embankment that restricts entry of oxygen and water Zone H* Plant growth layer Zone I* Structural fill forming downstream section of the perimeter road where it is in fill (not shown in Figure 5.4)** *PAF mine overburden material is not permitted for use in Zones A, G, H and I. ** Refer to EGL (2021b) Technical Report Appendix A drawings for further detail of these zones.
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