GHD | Oceana Gold New Zealand Ltd. | 12552081 | Waihi North Project E-9 Table 2 TSF Capacity Facility From mRL To mRL Capacity (m3) TSF 1A 172.25 173.60 891,335 TSF 1A 173.60 174.80 439,000 TSF 1A 174.80 176.30 550,000 TSF 1A 176.30 179.30 1,130,000 TSF 1A 179.30 182.00 1,060,000 TSF 2 156.00 160.7 1,230,000 TSF 2 154.50 156.00 420,000 TSF 3 Ground 135.00 700,000 TSF 3 135.00 145.00 2,020,000 TSF 3 145.00 150.00 1,380,000 TSF 3 150.00 155.00 1,570,000 TSF GOP 060.00 080.00 319,011 TSF GOP 080.00 103.00 1,680,047 Tailings volumes calculated in the WBM are allocated according to the tailings deposition schedule beginning with TSF1A, followed byTSF2 and then TSF3. Dual deposition of GOP TSF and TSF3 occurs when mining in GOP is finished. Filling of the TSF’s is modelled based on pre-determined stage volume relationships (Appendix F). The surface level of the tailings is determined from this stage volume relationship and water level is calculated by adding the volume of free water within the TSF on top of the tailings. The water level is monitored to identify freeboard encroachment or overflow potential. There is no provision to increase abstraction rates through manual intervention when large volumes of water accumulate through a model run as would be done in practice. Therefore, overflow potential predicted by the model provides a conservative indication of risk. Once a TSF pond has been classified as clean it can fill and overflow from the freeboard level. Catchment Areas and Runoff Table 1 provides a summary of the maximum catchment areas considered in the WBM for each area. Each of these catchment areas drain to a collection pond or sump with a defined volume and pumping rate. In the model there is some variation applied to account for catchment development over time. The catchment areas given for the TSFs include the pond surface area and the surrounding embankments that drain into the pond. It is assumed that all of the runoff ends up in the pond so the runoff factor is taken as 1. Rainfall runoff to collection ponds from the process areas use an area weighted runoff factor of 0.78 to account for all potentially cyanide affected water and recognising that the surface of the process area is well compacted or sealed and has low permeability. Runoff from the remaining areas is accounted for by a runoff factor of 0.5 to 0.7. Seepage Rates Seepage rates from TSF1A and TSF2 are modelled as 364 m3/d combined and these are determined from mine operation data for 2015 and 2016. For TSF3, NRS and the WRS, the modelled captured seepage applied to the modelling is 360 m3/d, 1,353 m3/d and 55 m3/d respectively. These flows contain
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