B-2 – Area 2 - Assessment of Environmental Effects 35 The Willows Access Tunnel will be used to transport development rock from underground to the WRS, and for general operational access between the mine and the Willows SFA. The Willows Access Tunnel will also be used to transport rock from the WRS to the WUG for backfilling of stopes. 3.3.2 Tunnel Design The Willows Access Tunnel will be required to facilitate truck access and will be developed with nominal dimensions of 5.8 m (W) x 6.0 m (H). Any lateral development not required to facilitate truck access will be developed with nominal dimensions of between 4.5 – 5.0 m (W) x 4.5 – 7.5 m (H). The tunnel will incorporate communications, electricity, water supply and drainage. In addition to the above generic services and infrastructure, the tunnel will include selfcontained, independently serviced refuge chambers at regular intervals. As described in the geotechnical reporting (WSP (2022b)) provided in Part H of these application documents, the tunnel is located and designed to prevent surface-level subsidence from occurring. 3.3.3 Tunnel Construction Methodology The method of tunnel development will be drilling and blasting using drilling jumbos for face drilling and ground support installation as has been used for other OGNZL underground mines. Load haul dump units (“boggers”) will be used to move fired material away from the face and underground trucks will be used to transport rock to the WRS. The tunnel development cycle consists of scaling and rock bolting, rebogging (clean-up), face drilling, charging, firing and finally bogging in preparation for the start of the next cycle. These activities are performed with standard underground mining equipment. The development cycle timeframe for the Willows Access Tunnel will be approximately 12 hours. During initial stages of tunnel construction, a ventilation fan will be located just outside the tunnel portal mounted within an acoustically treated container or similar (until such time as the Vent Shaft 1 is constructed). Any development ore intercepted during tunnelling will be stockpiled in the Willows Rock Stack for later transport to the Processing Plant.4 4 Following completion of the Wharekirauponga Access Tunnel (Area 3).
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