EGL Ref: 8983 23 June 2022 Page 43 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. 18.0 RESOURCE CONSENT - POTENTIAL RISKS AND MITIGATION MEASURES 1. Potential risks associated with the proposed dam will be minimised by designing, constructing and operating in accordance with the New Zealand Dam Safety Guidelines (NZDSG - Ref. 4). 2. The risks associated with inadequate design will be mitigated by using a dam Designer with appropriate experience. Dr Trevor Matuschka will be the Designer who has over 35 years of experience in the design and construction of dams, including High PIC dams and the existing TSF dams at Waihi. The NZDSG requires the design of High PIC dams to be subject to peer review. A peer reviewer with High PIC dam experience will be engaged to review the design for building consent. 3. The risks associated with 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 the Designer having representation onsite as recommended by the NZDSG. The Designer will undertake inspections during construction to confirm design assumptions, advise on any design amendments, inspect critical details to ensure they are in accordance with the design and confirm that construction standards meet specified requirements. 4. The risks associated with poor construction will be mitigated using a Contractor with experience in the construction of similar Medium or High PIC dams. On-site construction will be managed by a representative of the Contractor with experience in the construction of similar Medium or High PIC dams. 5. The main design risks are stability of the downstream slope during construction, internal erosion from seepage and stability when subjected to design earthquake ground motions. These risks can be mitigated through proper detailing of liners and embankment zones and full-time monitoring of the liner and drain installation for the Initial embankment. This will be controlled with an Earthworks Specification produced at detailed design. 6. Potential geotechnical risks have been investigated by undertaking comprehensive geotechnical investigations (Ref. 17). These risks are reviewed with site data and inspections during construction as outlined in Point 3 above. 7. The materials for construction of the dam consist of gravelly clayey silt or silty, clayey gravelly soils. These materials have good strength and good performance when subject to earthquake ground motions. 8. Erosion and sediment control plans are being prepared for the works (Ref. 20). The layout of the site allows for effective erosion and sediment control measures to be prepared. 9. Water for construction is available from the existing Collection Ponds and existing Storage 1A and 2 ponds as suitable, and other works onsite. 10. Dust will be controlled by spraying dry surfaces with water. Water will also be required to condition the earthfill and this will assist in reducing the potential for dust. 11. Potential dam safety risks will be mitigated by adopting a dam safety management system (see Section 16). This is to ensure the dam is maintained in a safe condition to
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