EGL Ref: 9215 23 June 2022 Page 45 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. H), removal and re-siting of the perimeter road and drain, Collection Ponds S3, S4 and S5 and silt ponds, the seepage/leachate collection system. A small downstream construction raise by steepening of the downstream shoulder above existing higher level benches is an option but still requires removal of Zones G and H. A small centreline raise constructed above existing higher level intermediate benches is also an option. • Storage 1A can be raised by downstream or centreline construction. • Dry stacked filtered tailings could be placed above the existing tailings without any raise of the Storage 1A embankment. However, this option is not suited to the climate at Waihi. Capital and operating costs are very high. • Mine open pit overburden material could be placed above the existing tailings to create a dry cap. This would compromise future raising to provide additional tailings storage and a dry cap is not considered the best closure option. 8.3. North of Storage 2 The potential exists to construct a new TSF or rock stack to the north of Storage 2. Geotechnical investigations, conceptual designs and feasibility studies have been undertaken. Ground conditions are suitable but any TSF in this area has poor storage efficiency (i.e., a large volume of embankment fill is required to provide a relatively small volume of tailings storage). In addition, any option that provides significant storage would impact on a Significant Natural Area (SNA) located on the east boundary and would be located close to Golden Valley Road. Dry stacked filtered tailings could be located north of Storage 2. However, this option is not suited to the climate at Waihi and capital and operating costs are very high. 8.4. Northeast of Storage 2 A new TSF or rock stack could be developed on land located about 1.2 km to the northeast of Storage 2. The northern boundary of the site is Trig Road North. The land is not owned by OGNZL. Limited geotechnical investigations have been undertaken and a prefeasibility level study completed. No major geotechnical constraints were identified. However, a TSF at this location is very inefficient (i.e., a large volume of embankment fill is required to achieve a relatively small volume of tailings storage). A major constraint is it would not meet the project scheduling requirements because it would require a large amount of fill to provide tailings storage. Other constraints include that the land is not owned by OGNZL, it would impact on a new area and there would be additional affected stakeholders. Dry stacked filtered tailings could be located northeast of Storage 2. However, this option is not suited to the climate at Waihi. Capital and operating costs are very high. 8.5. Northeast valley Opportunities to store either tailings or mine open pit overburden are available immediately to the northeast of Storage 2. OGNZL does not own all this land. The storage capacities for either tailing and mine open pit overburden are limited compared to other options, but they are closer to the Processing Plant and the conveyor/loadout than some other options.
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