June 2022 G-01483.84-017-R-Rev0 Because the 26 ▪ Further detailed design stage investigations will need to be undertaken to confirm the thickness of the surficial soils under the WRS to refine the model and the volume of material to be removed from the base of the WRS. However, existing site investigation data indicates that less than 1 m thickness of weathered volcanic ash and 0.3 m top soils (20,000 m3-30,000 m3 in total weak soils) will need to be removed throughout the WRS footprint. ▪ Weekly monitoring is recommended to check for any deformation of the WRS during construction and when completed. This monitoring would comprise visual inspections to check for movement in the natural ground at the toe, and any movement evident in the WRS. Additional monitoring should include survey points at key locations on the WRS. The survey points would be measured daily to form a baseline, then less frequently based on the observed performance. 6.10 WRS Design Assessment Table 11 presents the criteria applied for the proposed WRS, haul road and portal access designs developed from the geotechnical analysis results. The WRS designed total capacity is 876,000 loose cubic metres (LCM) to account for the planned tunnel spoil and additional material estimated generated during development. The haul road design criteria are based on truck specifications for a TORO TH663i, the planned haulage unit for spoil material during tunnelling. Cut batter slopes for access and the width of the haulroads are to be confirmed at detail design stage. Table 11: PFS WRS and haul road design criteria. Parameter Unit Value Comment WRS batter face angle Deg. 1v:1.4H 35 degrees WRS bench height M 10 WRS berm width M 6.0 graded at min 1:75 for surface water control WRS inter-ramp angle Deg. 1V:2H 26 degrees Single lane WRS ramp width M 10 Truck – TORO TH663i with 1 drain + 1 bund Dual lane WRS ramp width M 16 Truck – TORO TH663i with 1 drain + 1 bund Gradient haul road (maximum) 1V:7H Haul road bund height M 1.0 Minimum half the height of TORO TH663i tire (35/65 R33) Haul road bund width (top) M 0.5 Flat Haul road bund slope angle 1:1 To be constructed on outside edge of benches and roads, rock fill Material swell factor 1.3 Estimated based on existing Waihi mine site data Topsoil stockpile height M 3.0 Maximum measured from toe to crest Access road cut slope angle 2V:1 Assuming rock, for cuts greater than 5 m, assess stability in detail design phase
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