EGL Ref: 9018 22 June 2022 Page 27 WAI-985-000-REP-LC-0006_Rev0.docx This report shall only be read in its entirety. • Surface water drainage on the NRS rehabilitated surface The permanent surface water drainage criteria is recommended to convey a 1 in 100 year flow without erosion of the NRS. This allows for a range of options including overland sheet flow, open channel flow, and piped drainage systems to be considered or combined. Detailed design is required for the NRS as drains and stability considerations require assessment, and drawings and specifications are required for construction. So, while building consent is not required under the Building Act, a peer review of the detailed design is recommended, to be provided by an appropriately qualified independent party. The requirement for detailed design peer review of the stockpile could be a resource consent condition. 15.2. Northern Rock Stack Collection Pond The NRS Collection Pond is likely to be classified as a large dam as mentioned in previous Sections 8.4, 9.8 and 10.5. It is recommended that a detailed design report, drawings, and specification is prepared for the NRS Collection Pond. The Collection Pond requires both resource consent and building consent. 15.3. Workshop relocation The relocated Development Site Workshop will require a resource consent and building consent. 15.4. Magazine platform The magazine platform forms part of this scope of works for resource consent. Any other consenting requirements for hazardous/explosive substances should be considered by OGNZL. 16.0 SUMMARY OF POTENTIAL RISKS AND MITIGATION MEASURES 1. Potential risks associated with the proposed NRS will be minimised by designing, constructing and operating in accordance with practices that have already been employed successfully at the Development Site. 2. The risks associated with inadequate design will be mitigated by using a Designer with appropriate experience. Trevor Matuschka will be the lead Designer and he has over 35 years of experience in the design and construction of dams and stockpiles on mining sites generally and specifically at Waihi. 3. The risks associated with the NRS construction not being in accordance with the design and not responding to actual site conditions, which may be different to those assumed, will be mitigated by full time supervision by OGNZL who employ people with expertise in the construction of such facilities and the Design Engineer undertaking regular inspection of the sites. The Design Engineer will undertake inspections during
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