EGL Ref: 9018 22 June 2022 Page 7 WAI-985-000-REP-LC-0006_Rev0.docx This report shall only be read in its entirety. capping for closure. There is 6.8 Mm3 of high mercury NAF or PAF material that will be placed directly to Storage 3 or managed and conditioned in stockpile for later placement to Storage 3 or reserved for GOP TSF backfill. GOP TSF requires approximately 2.5 Mm3 of backfill. The maximum stockpiling capacity provided for in the proposed NRS layout is 7.0 Mm3. This will be sufficient to manage the movement of materials at the Development Site for the WNP. It is estimated that the stockpile will operate at between 3 to 6 Mm3 during operation and at closure it will be depleted to approximately 2 to 2.5 Mm3. Up to 4 Mm3 has been allowed for in the closure profile. 3.2. Proposed Northern Rock Stack The NRS is proposed as the new stockpile and permanent rock storage facility at the Development Site. The stockpile will be required to store both NAF and PAF materials. It will abut the Storage 2 embankment at its south extent and extend to the north over the existing Northern Stockpile and existing farmland owned by OGNZL. Along its west boundary is the Ohinemuri River and to the east is a series of hills covered in vegetation and farmland. The proposed location is shown in Figure 5 and on Drawing 0715 in Appendix A. 4.0 GEOTECHNICAL INVESTIGATIONS AND SITE GEOLOGY Geotechnical investigations have been undertaken in the footprint of the proposed NRS in 1994, 1995, 1996, 1997, 2001, 2007, 2009, 2010, 2017, and 2018. The investigations are documented in the Geotechnical Factual Report (GFR) for the NRS site (Ref. 5). Figure 6 to Figure 9 show the locations of machine drillholes, hand auger boreholes, test pits and Cone Penetrometer Tests (CPTs) undertaken at the NRS site. 4.1. Overview The NRS is located within a broad gully (Figure 5) overlying rhyolite, dacite and ignimbrite. A thin blanket of volcanic ash blankets the alluvium except in low lying areas where it has been eroded. Over most of the low-lying areas, the alluvium is of variable thickness. A geological map showing the deposits beneath the alluvium and ash is in Figure 13. Beneath the dacite are varying thicknesses of volcaniclastics, hydrothermal vent breccia, and then andesite rock. Regional andesite rock underlies the site at depth. Andesite outcrops at the hills (Black, Winner, Gladstone, Union, and Favona) to the south-west and west of the NRS. The surface of the andesite and dacite dips down towards the east beneath the rhyolite. The interpretation of these geological units is described in the following sections from the youngest and shallowest to oldest and deepest. Five geological cross sections through the NRS site are shown in Figure 14 to Figure 18. The plan locations of the sections are shown in Figure 13. The geological sections show the geology interpreted from the investigations and include the machine drillholes and CPTs used in the
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