8 | P a g e Class 1 Storage Location Assessment_Oceana Gold NZ Ltd Wharekirauponga Underground Mine ‘Annex M’ does not provide a category for the 9 kPa threshold criteria. The Quantity Distance (QD) factors are therefore derived from scaling other known criteria such as the ‘Inhabited Building Distance (IBD) at 5 kPa and the Public Traffic Route Distance (PTRD) of low traffic density at 13 kPa. In order to quantify the actual potential effects of ‘unintended detonation’ related to over pressure and associated controlled zones, there are a number of elements which need to be established. These are summarised below. • Location at surface of exit/ entry portals and ventilation shafts. • Quantity of explosives being stored (NEQ) and likely singular detonation mass. • Size of magazine chamber. • Total likely underground mine development/ tunnel volume associated with overpressure flow pathway. • Hydraulic diameter at tunnel entrance or ventilation shaft surface connection. Figure 5 shows the proposed design volume used to calculate controlled zones. This method is highly conservative and omits a significant quantity of alternate travel avenues for an overpressure event. For the purpose of establishing a minimum base scenario at the proposed magazine facility location, the total volume in consideration for each surface portal/ ventilation shaft connection has been calculated as the lowest of all likely travel paths at ~90,229 m3 (refer to green coloured tunnels and shafts shown in Figure 4) This allows for highly conservative assumptions that likely overstate the effects at surface. ‘Figure 4 – Proposed mine workings used to calculate total volumes for controlled zone consideration’. 5.1. Location of Surface Portals and Vent Shafts There are a number of proposed ventilation shafts and a surface portal that are to be considered for over pressure venting and associated controlled zone calculations. Figure 5 indicates the proposed locations of these surface connections. The final positioning and parameters of the surface connections will be established during the later stages of site design prior to construction. This will influence the final calculation of controlled zones and the required offsets restricting public access. Proposed Underground Magazine Facility Area in green denotes tunnel path for volume calculations Included in VT P2 - WUG FAR #1 P3 - WUG RAR #2 P4 - WUG Fresh Air Intake To Willows Road (P0 – Portal and P1 - Fresh Air Intake)
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