GHD | Oceana Gold (New Zealand) Ltd | 12552081 | Waihi North 89 The added material properties and boundary conditions for these scenarios are in Table I.8 and Table I.9. The constant head boundaries, recharge and material properties remain as per the base model unless provided below. Table I.6 Summary of steady state model scenarios for Cross-section 1 (all stages of TSF3 construction) Scenario Stage of work Description 1 (Parent for Scenario 2) Ruahorehore Stream Diversion The calibrated base model was updated to relocate the Ruahorehore Stream approximately 40 m to the south and the surface alluvium replaced with Zone A material. This formed the base model for the following scenarios. 2 (Parent for Scenario 3) Construction dewatering Construction dewatering as a parent model for the proposed starter embankment. Included fully dewatered excavation of the sensitive tuff to 15 m depth without backfill. 3 (Parent for Scenario 4) Starter Embankment (1,135 mRL) Scenario 3 considers completed foundations works with tailings placed to the full height of the starter rock embankment (1,135 mRL). The HDPE liner is emplaced to 1,135 mRL and all drains are assumed to be operational. The tailings at this stage of construction have the least amount of consolidation and therefore the greatest applied KV of all scenarios. 4 (Parent for Scenario 5) Operational to closure (1,155 m RL) Embankment height and tailings increased to 1,155 m RL. A lower tailings KV was applied to represent the modelled tailings consolidation by EGL (see Table I.9). 5 Long-term / Post closure (1,155 m RL) As per Scenario 4, with further decreased tailings KV to represent 90% tailings consolidation. In this scenario, drains are removed from the analysis to simulate potential drain failure, except for the downstream toe drain which remained operational within the scenario. Figure I.4 TSF3 Cross-section 1 SEEP/W model set-up with close up of drains beneath the embankment
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