B-1 - Area 1, Coromandel Forest Park – Assessment of Environmental Effects 40 3.2.2.2 Tunnel Construction Methodology Construction of the Dual Tunnel will also commence at the boundary between the Willows Road Farm and the CFP. The Dual Tunnel will be developed at a gradient to ensure optimised water management with links between the tunnels at intervals as the tunnels advance. Once the Dual Tunnel reaches the Wharekirauponga orebody, Vent Shafts 2 – 5 will be constructed sequentially. 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 blasted material away from the face and underground trucks will be used to transport rock to surface stockpiles. Construction of the Tunnel System will initially proceed via the Willows Portal. Tunnels and shafts may be progressively sealed with grout or shotcrete during development as required to manage water ingress that has the potential to affect surface waters. Ventilation will be provided above-ground (from a fan located in an acoustically insulated shipping container at the Willows Portal) until Vent Shaft 1 is completed. All ventilation equipment will then be located underground. 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 entire cycle is approximately 12 hours. Firing will take place generally as soon as possible after the face (or faces) have been charged. Development of the tunnels at Willows Road Farm and leading into the CFP will involve up to 20 firings per calendar week. Rock will be loaded into trucks and hauled to the C. Any development ore intercepted during tunnelling will be stockpiled in the Willows Rock Stack (“WRS”) for later transport to the Processing Plant.4 3.2.2.3 Forward Drilling Program As construction of the tunnels advances diamond drilling will occur ahead of the development face. Retrieved drill cores will be oriented, boxed, and subjected to geological, geotechnical, and hydrogeological analysis. The forward drilling will provide geotechnical and hydrogeological information for ground ahead of tunnelling to inform geotechnical and water management requirements for the corresponding length of tunnel. 4 Following completion of the Wharekirauponga Access Tunnel (Area 3).
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