B-1 - Area 1, Coromandel Forest Park – Assessment of Environmental Effects 47 3.2.6 Mining of the Orebody 3.2.6.1 Mine Development Access to stoping blocks is obtained by mining spiral declines. Initially, access drives will be mined to develop drilling and loading levels, intersecting the orebodies. Ore drives will be developed in both directions along strike from the access drives. Stockpiles will be mined off the decline and in levels for truck loading. Development design profiles have been assumed to be the same dimensions as currently used at Waihi and all development has been designed at a maximum 1 (V): 7(H) gradient. Declines requiring truck access will likely be developed at a 5.0 m (W) x 5.5 m (H). Further lateral development is required for infrastructure including sumps, pump/dewatering cuddies, crib rooms, electrical infrastructure, refuge chambers, underground workshop and underground magazine. Level accesses beyond truck access areas and ore drive development have been designed at 4.5 m (W) x 4.5 m (H). Vertical development includes 2m to 5m raises and drill holes for the purposes of providing ventilation, secondary egress, and services throughout the mine. While Alimak is the preferred method for shaft construction with surface breakthrough, flexibility is sought for the shaft construction methodology for internal vertical development underground. Finger passes and longhole winzes are generally short in length (i.e. up to 30 m) and can be drilled and blasted with a longhole production rig. Electrical holes, service holes and drain holes up to 30 m in length can also be drilled with a longhole production rig. For longer internal shafts, raise boring could be used. 3.2.6.2 Mining Method Mining of the Wharekirauponga orebody will generally be carried out using the Modified Avoca mining method (refer Figure 28). The Modified Avoca method is a semi-selective and productive underground mining method, and well suited for moderately dipping deposits of varying thickness. Modified Avoca has been used successfully at the underground mines at Waihi for several years and is a flexible mining method for minimising dilution in narrow vein orebodies.
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