WUG Access Tunnel – Waihi to Willow Farm The WUG access tunnel will be driven from the near the WTP in Waihi and will connect with the dual tunnel at Willow Farm at the vent shaft location. Table B2 provides the metrics for this tunnel section. Table B2 WUG Access Tunnel Metrics 4,700 m Single tunnel from the Waihi WTP to the dual tunnel 270 m Portal link bypass drive 640 m Stockpiles and Sumps 5,610 m Total B.3 Model Inputs The following inputs were adopted for the calculations. Tunnel radius (r): is assumed to be 6.0 m diameter, radial diameter is assumed to be 3.0 m radius Hydraulic Conductivity (K): The Hydraulic Conductivity values have been derived from a number of sources including: back analysis of the Kaimai Rail Tunnel (Davoren, 1983), in-situ testing at the WKP ore body and at Willow Farm, analysis of fracture spacing from exploration drilling and experience from testing of similar geologic units at Waihi and other deposits in the Coromandel. The values assigned to the various geologic units are presented in Table B1. For the transient analysis, a Hydraulic Conductivity value was assigned to each geologic unit based on the geological model provided by GHD (Aug, 2020 - Appendix A1). Specific Storage Coefficient (Ss): The Specific Storage inputs have been assigned based on experience from testing of similar geologic units at Waihi Gold and from other locations. The values assigned to the various geologic units are presented in Table B1. Table B1 Assumed Range of Aquifer Parameters Geologic Unit Hydraulic Conductivity (m/s) Specific Storage Andesites 1.0 x 10-8 to 5.0 x 10-9 0.001 to 0.000001 Clay Altered Andesite 5.0 x 10-9 0.0001 Silicified Andesite 5.0 x 10-9 0.0001 Rhyolite 5.0 x 10-9 to 5.0 x 10-9 0.0001 to 0.00001 Fault Zones 1.0 x 10-5 to 1.0 x 10-7 0.1 to 0.001 Groundwater Head (So) The groundwater heads have been determined based on the relationships to depth observed at the Willow Farm and WKP sites from the drilling investigations and interpolated based on the topographic elevation along the tunnel alignment. Tunnel advance rate (v) The analytical model uses variable advancement rates that have been calculated based on the tunnelling schedule. These are; 10 m/d up to 1,350 m chainage, 8 m/d up to 4,000 m and 6 m/d for the remainder access tunnel development. The access tunnel is assumed to advance at 10 m/d up to 1,400 m chainage reducing to 8 m/d until the dual tunnel is reached.
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