EGL Ref: 9049 23 June 2022 Page 9 File: WAI-985-000-REP-LC-0050-Rev0.docx This report shall only be read in its entirety. highly weathered from approximately 16m to 24m deep and then abruptly changes to moderately to slightly weathered andesite, with quartz veining present. It is assumed that this weathered surface of the andesite will be of sufficiently low permeability to minimise drawdown of the ignimbrites above, as is found elsewhere around Waihi. 3.4. Wharekirauponga Access Tunnel geology A high-level interpretation of the geology for the Wharekirauponga Access Tunnel by Golder (Ref. 27) is shown in long section in Figure 20. Sections from the OGNZL geology model (Ref. 26) in Figure 9, Figure 13, Figure 16, and Figure 17 also show the inferred geology. Behind the east end of the Waihi township the tunnel is indicated to pass through Waipupu Formation andesite (aw) which consists of andesitic flows, breccias, and tuffs, some of which are hydrothermally altered (Ref. 36). The tunnel will then pass through the younger andesite (inferred to be Whitiroa andesite by Golder Ref. 27), before returning back into Waipupu Formation andesite (Ref. 27). The younger andesite present in the mid-section of the alignment is inferred to be on a down thrown block (graben) that is bounded by northeast regional scale faulting (Ref. 27). It is expected that there will be fracture zones associated with these faults and that ground conditions will be weaker than the general andesite rockmass (Ref. 36). The WUG Portal entrance for the Wharekirauponga Access Tunnel is likely to be in andesites. However, the top of the cuts for the portal may intersect ignimbrites blanketing the hill. The Wharekirauponga Access Tunnel decline alignment is slightly to the west of the current Favona Underground, however, will be notably shallower and may intersect both overlying ignimbrites and hydrothermal vent breccia before reaching the andesite again before passing behind Waihi East. PSM (Ref. 40) has produced an indicative section along the decline alignment which is included in Figure 21. The existing Favona Underground vent shafts are approximately on the alignment of the decline (Figure 3). There is approximately 15m deep ignimbrites, with approximately 15m thickness of hydrothermal tuff (volcaniclastics) over hydrothermal vent breccia (Ref. 39) at this location. The hydrothermal vent breccia is 50m thick and overlies the upper andesites. The Favona Underground is within the upper andesites. Close interaction of the tunnel decline and the vent shafts present a potential risk of groundwater drawdown in the younger volcanics. 3.5. Willows Road site geology The geology of the Willows Road site is summarised on Figure 22 and Figure 30, produced by GHD (Ref. 28). The site is noted to consist of a depth of primary weathered rock and/or pyroclastic deposits that are weathered to form clay and silt soils (Ref. 36). These soil materials are a few metres thick on the steeper slopes and in the gullies are around 7 to 15 m thick. Beneath these soils either lies relatively fresh andesite rock in the northern part of the site (Waipupu Andesite) or completely weathered tuff (Whiritoa Andesite) (Ref. 36) towards the portal and site infrastructure location. Golder (Ref. 38) infers the contact between the two units to daylight on the west side of Willows Road Farm and dip to the east. In the low-lying areas adjacent
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