EGL Ref: 9215 23 June 2022 Page 54 This report shall only be read in its entirety. File: WAI-985-000-REP-LC-0002_Rev0.docx. that it is feasible to steepen the existing downstream shoulder and still meet NZDSG recommended design criteria. 9.1.6.2. Raising of Storage 2 Storage 2 could be raised by downstream or centreline construction. The downstream toe would have to be moved out as steeper slopes over the existing embankment are not possible. This would require the perimeter road and drain and other infrastructure (e.g., West Silt Pond, seepage/leachate collection sumps, pipes and pumps) to be relocated. 9.1.6.3. New downstream embankment dam north of Storage 2 A new downstream embankment could be constructed north of Storage 2. The site is not particularly efficient as there is no natural valley to build the embankment across and the hills to abut into are not as high as those behind Storage 1A and 2. 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. 9.1.6.4. New downstream embankment dam northeast of Storage 2 A new downstream embankment could be constructed northeast of Storage 2. The site borders Golden Valley and Trig Roads. The site would be similar to Storage 1A and 2 abutting the hills with a Ushaped embankment. New infrastructure would be required to the site. Limited geotechnical investigations have been undertaken and a prefeasibility level study completed. No major geotechnical constraints were identified. 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. 9.1.6.5. New downstream embankment in northeast valley A new downstream embankment could be constructed in a small valley on land immediately northeast of Storage 2. OGNZL does not own all this land. Geotechnical investigations and a prefeasibility study have been undertaken for a potential TSF. It has limited capacity (approximately 2 Mm3). No major geotechnical constraints were identified. Constraints include the land is not owned by OGNZL and it encroaches into a SNA. 9.1.6.6. New downstream embankment dam east of Storage 1A The site east of Storage 1A has always been considered as a potential TSF location and extensive geotechnical investigations and a feasibility study have been completed. This site is called the
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