B-6 – Area 6 – Assessment of Environmental Effects 31 3.2.4 Drains and Collection Ponds An uphill clean water diversion drain will be constructed upstream of the NRS for the collection of natural ground runoff and stream flows. Water collected in the uphill diversion drain will discharge directly to the Ohinemuri River (shown in blue on Figure 15). The uphill diversion drain will be sized for a minimum requirement of a 10 year ARI flow, equal to existing resource consent conditions for clean water diversions (RC971307, RC971309, Condition 4). The clean water diversion drain does not encroach into the T13UP166 SNA identified in the HDP. A perimeter drain will be installed around the NRS for the collection of surface runoff from the NRS and conveyance to a collection pond. The dirty water drain will be sized for a 100 year ARI flow. The perimeter drain will be separated from the uphill diversion drain by a 6 m wide perimeter road. A collection pond located to the west of the toe of the NRS will be sized to manage runoff from a 10 year return period, 72 hour rain event without discharge. Water in the collection pond will be pumped to the WTP for treatment (when water quality requirements dictate) before discharging to the Ohinemuri River. All features described above are shown on Figure 15. 3.2.5 Erosion and Sediment Control Southern Skies (2022) describe the erosion and sediment control measures that will be implemented for these works. A copy of Southern Skies (2022) is provided in Part H of these application documents. Southern Skies (2022) includes: An Erosion and Sediment Control Assessment Report (“ESCAR”) which provides: o The overarching erosion and sediment control (“ESC”) principles and procedures for the earthwork activities associated with the Waihi North Project; o An assessment of the effectiveness of those ESC principles and procedures in minimising potential sediment discharges to an acceptable level; and o Concepts that inform the development of the draft Site-Specific Erosion and Sediment Control Plans (“SSESCPs”); A Chemical Treatment Management Plan (“CTMP”); An Erosion and Sediment Control Monitoring Plan; and
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