SECTION 3 Groundwater Effects Assessment – WUG Access Tunnel 7 3. Groundwater Effects Assessment – WUG Access Tunnel 3.1 Tunnel Description The WUG access tunnel will be a single tunnel driven from a newly constructed portal at the water treatment plant (WTP) near the existing Favona portal in Waihi. The portal will start at an elevation of approximately 1125 mRL and will decline vertically by some 180 m over a 1,500 m distance. The remainder of the tunnel out to the Willows Farm connection is a gentle incline of around 50 m over 4,000 m. It is anticipated that the tunnel will be advanced at a rate of around 8-10 m/d and will be driven from both ends to meet in the middle to avoid the need for ventilation shafts. The tunnel alignment is shown on Figure 4. Figure 4 WUG Access Tunnel Alignment 3.2 Characterisation of Tunnel Alignment 3.2.1 Physiography Along the first 2,500 m of the tunnel from the portal to SH25 the topography is generally flat lying at an elevation of approximately 1120 mRL. North of SH25, the topography steepens into the Coromandel Ranges to a maximum of around 1250 mRL beneath the Willows Farm site. For the first part of the alignment through the Waihi township the tunnel is approximately 90 m below ground level. Beneath the Willows Farm site, it reaches a maximum of 275 m below ground level below the crest of a hill.
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