EGL Ref: 9018 22 June 2022 Page 10 WAI-985-000-REP-LC-0006_Rev0.docx This report shall only be read in its entirety. found on the eastern side of the NRS site appears to be the western edge of the local Ruahorehore Dome. The extent of rhyolite is shown in Figure 13. Rhyolite rock is found in Borehole WRS3a (at 19.6 m depth) and WRS8 (at 9 m depth). DH8 drilled to 25.9 m extends through 8 m of rhyolite lava rock and into a dacitic breccia above the dacite flow. The rock exposed in some test pits is also thought to be rhyolite. TPW4 reaches rhyolite near to the surface and is brecciated in the photos. The brecciated pattern is similar to a pyroclastic mixture of rhyolitic ash and boulder sized rhyolite found on the northern slopes of the Storage 3 site. The strength of rhyolite is highly dependent on the degree of weathering and decomposition of rock, varying from very weak to strong (Unconfined Compression Strength UCS = 1 to 100 MPa) on the eastern edge of the NRS site. In borehole DH8 the rhyolite is very weak (1 to 5 MPa) at the surface increasing to moderately strong (20 to 50 MPa) after a couple of meters. The rhyolite in TPW4 and TPN55 was too hard to excavate with a 14-tonne excavator. 4.10. Dacite flow (Uretata Formation) Dacite lava (flows) are found across the NRS site near to the surface or overlain by ignimbrite, old alluvium or rhyolite. The extent of dacite near the surface is shown in Figure 13. The dacite, to the north of NRS site varies in weathering from residual soil to slightly weathered. The completely weathered dacite has soil strengths. The slightly weathered dacite rock can be moderately strong through to strong. In boreholes WRS7, DH7, DH8 and DH9, materials consisting of angular clasts of dacite within the lava flow or tuff matrix have been interpreted as dacite breccia. Borehole logs for groundwater monitoring holes indicate that dacite is near to the surface along the Ohinemuri River immediately west of the existing Northern Stockpile. Dacite is also near the surface just beyond the northern toe of the existing Northern Stockpile. A weathered profile of dacite was encountered at depths from 4m to 8m (in DH6, DH7, WRS1a and WRS2a). Further to the north, borehole WRS5a also indicated dacite rock near to the surface. Borehole WR8 indicates the dacite is approximately 85 m thick. Beneath the dacite, clay altered volcanic materials are logged, possibly associated with a non-active fault zone. Investigations on the west side of the Ohinemuri River indicate varying thicknesses of volcaniclastics, hydrothermal vent breccia and andesite rock. 5.0 HYDROGEOLOGY 5.1. Overview GHD has developed a conceptual ground water model for the NRS site and the following is taken from their report (Ref. 6). The geology at the NRS is notably different to that at the GOP and Storage 3 TSF, with no clear separation of shallow and deeper groundwater systems. This is due to the presence of multiple alluvial paleochannels within and overlying variable volcanics (ignimbrite, dacite and
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