EGL Ref: 8983 23 June 2022 Page 40 WAI-985-000-REP-LC-0004_Rev0.docx This report shall only be read in its entirety. will require a Dam Safety Assurance Program (DSAP) that will require certification by a Recognised Engineer. Annual certificates will need to be submitted by a Recognised Engineer that certify compliance with the DSAP. The TSFs at Waihi will comply with the proposed Dam Safety Regulations. 16.2. Operation and Water Management The operation of Storage 1A and 2 is managed by OGNZL. Water on the surface of the TSFs is pumped back to the Process Plant for re-use or to the Water Treatment Plant via pumps, until closure when the water returns to a sufficiently high quality to be direct discharged without treatment. A similar operation will be used for Storage 3. During operation of Storage 3 a beach will be maintained around the upstream embankment by discharging from spigots. This minimises depth of water that may impound in flood events against the embankment, and during drier periods has the benefit of air drying the tailings surface which results in higher densities and strength in the beach area. This provides for more efficient storage of tailings and also reduces the potential for seepage of pond water through the embankment. The proximity of the decant pond to the embankment will be controlled by selective discharge of tailings from the spigots around the embankment to maintain a consistent beach and pumping of water back to either the Process Plant or Water Treatment Plant to control the water level. A final tailings closure plan is shown in Drawing 690. It will be necessary during the later stages of tailings discharge to regularly survey the tailings surface to check that the profile is in accordance with closure design requirements including that there is sufficient storage for the design rainfall event and to meet design freeboard requirements. 16.3. Maintenance Maintenance activities include: • Weed control and fertilising of pasture and vegetation on the embankment • Maintenance and testing of the pumps and inspection of the tailings and return water pipelines • Undertaking repairs due to erosion following heavy rainfall • Maintenance of vehicle access to and over the embankment crest • Maintenance of the subsurface drain outlets, flowmeters, seepage collection sumps and pumps and return water pipelines • Maintenance of surface drainage systems (removal of sediment, localised slips) • Removal of sediment from the collection ponds and maintenance and repair of the decant pumps 16.4. Surveillance and monitoring Surveillance (visual inspections) and monitoring is to be undertaken to monitor the performance of Storage 3. The purpose is to allow the performance of Storage 3 to be assessed and reported against design expectations; enable the detection and mitigation
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