June 2022 G-01483.84-017-R-Rev0 Because the 6 Several deeply incised gullies carry surface flows across the Willows Road farm property into Mataura Stream from the south. Mataura Stream has formed a series of alluvial terraces approximately 10 m above the main channel of the stream. Exposed alluvial deposits (incorporating some rounded boulders of volcanic origin) in terrace outcrops and hummocky deposits on the lower terraces suggest that flood or debris flows can affect Mataura Stream and tributaries. The proposed WUG SFA is located on a gently sloping terrace approximately 10 m above Mataura Stream. The proposed WRS is located approximately 400 m northwest of the SFA in a small tributary valley (Figure 2). 4.0 GENERAL GEOLOGY The Coromandel Peninsula, south as far as Te Aroha, and including the area around and north of Waihi, is dominated by volcanic rocks of the Coromandel Group comprising andesite, dacite and rhyolite of Miocene Age (Edbrooke 2001, Braithwaite, Christie 1996). The Willows Road farm property, is underlain by two volcanic rock units. The upper unit is the Whitiroa Andesite and is inferred to directly underlie surface mine infrastructure elements including the WRS. The Waipupu Formation, which comprises andesite and dacite, and is commonly hydrothermally altered, underlies the Whitiroa Andesite. The contact between the two units is inferred to daylight on the west side of the Willows Road farm and dip to the east (Figure 3). Basement rock in the area comprises Jurassic Age Manaia Hill Group sandstone, siltstone and conglomerate at more than 1000 m depth. The Coromandel Peninsula is located on the western side of the Taupo Volcanic Zone, which is an extensional tectonic domain dominated by northeast trending normal faults of low activity. 5.0 GEOTECHNICAL FIELD PROGRAM Key geomorphological features of the site were identified by WSP-Golder using analysis of available aerial imagery and topographic information. This assessment utilised high-quality LiDAR (light distance and ranging) survey data supplied by OGNZL, aerial imagery supplied by OGNZL and Google Earth. The identified geomorphological features are summarised in (Figure 4). Key observations include widespread shallow slope instability on the steep slopes and a number of lineaments that could be interpreted as faults in the underlying geology. Groundwater inflows were recognized in the small streams that flow in the tributary branches and regular flow measurements have been undertaken by OGNZL. The springs reach upstream under most of the WRS footprint, are confined to the stream channels and are observed to dry up during the summer. We infer that the seeps come from more permeable units within the underlying volcanic rocks. A series of 24 test pits were excavated around the Willows Road farm site to investigate and describe the near surface materials, carry out in situ strength testing and sample soils for laboratory characterisation of geomechanical properties. Test pit locations were selected by WSP-Golder and OGC to investigate the areas where important infrastructure elements are planned. The test pits were excavated using a tracked excavator and logged and photographed by a GHD engineering geologist. Following backfilling, all test pits were located by OGNZL surveyors (Figure 5). Logs of all test pits have been prepared by GHD.
RkJQdWJsaXNoZXIy MjE2NDg3