EGL Ref: 9018 22 June 2022 Page 23 WAI-985-000-REP-LC-0006_Rev0.docx This report shall only be read in its entirety. 10.4. Surface water collection system As per Section 8.3 surface water drainage systems on the NRS are to be design to manage a 100 year ARI flow. The surface runoff pipes or surface drains are likely to be at approximately 200 m centres and pipes are likely to be 225 to 300 mm in diameter. The design concepts will be a combination of benches that divert runoff to sumps and buried pipes that discharge runoff down the slope into the perimeter drain. In very large rainfall events runoff overflows the benches and flows as sheet flow down the NRS slopes. A similar piped surface water system on Storage 1A and 2 has operated without incident throughout the operation of the embankments. Maintenance of the castle sumps is required. The same consistent performance is expected for the NRS. 10.5. Northern Rock Stack Collection Pond As outlined in Section 8.4 the NRS Collection Pond will likely be considered a large dam and be designed to the NZDSG. As per Section 9.8 the pond will be lined and incorporate its own subsurface drainage system. Design concepts and geometry will be similar to the existing collection ponds. The fill and cut slopes associated with the collection ponds will be designed to meet conventional factors of safety and performance for different load conditions. This will be confirmed at later detailed design stages with a separate design report and drawings. 11.0 DRAWINGS The following drawings listed in Table 7 have been prepared for resource consent for NRS to RL173. TABLE 7: NRS RESOURCE CONSENT DRAWING LIST Drawing No. Drawing Title WAI-983-080-DWG-CI-0700 Locality Plan and Index - Northern Rock Stack - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0715 Layout Plan - Northern Rock Stack - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0716 Sections - Northern Rock Stack - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0717 Sections - Northern Rock Stack - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0730 Perimeter and Diversion Drains Sections Sheet 1 of 4 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0731 Perimeter and Diversion Drains Sections Sheet 2 of 4 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0732 Perimeter and Diversion Drains Sections Sheet 3 of 4 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0733 Perimeter and Diversion Drains Sections Sheet 4 of 4 - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0761 Sections – Collection Pond - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0770 Layout Plan - Leachate Drain - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0772 Layout Plan - Subsoil Drains - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0780 Layout Plan - Closure Rehabilitation - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0781 Sections - Closure Rehabilitation - Tails / Waste Rock 080 WAI-983-080-DWG-CI-0782 Sections - Closure Rehabilitation - Tails / Waste Rock 080
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