7 | P a g e Class 1 Storage Location Assessment_Oceana Gold NZ Ltd Wharekirauponga Underground Mine 4.3 Other Considerations - Major Damage Prevention to Interior of Facility When establishing appropriate storage capacities and segregation distances between magazine chambers, appropriate CID should be considered in order to mitigate risk of substantial damage to the interior of facility (in the event of an unintended detonation). This can be referenced in ‘ IATG 2.20 - ANNEX M’ , Where Loading Density < 50 kg/m3 (see above) For the maximum stored quantity of H.E per chamber, (where Q = 1,000 kg) Required CID = 1.0Q1/3 = 10.0 m The minimum required CID for ‘major damage prevention to interior of facility’ has been calculated at distance of 10.0 m. The current proposed design of 10.0 m separation distances between chambers is therefore adequate. 5. Controlled Zones at Surface Connections (Portals and Ventilation Shafts) There are varying overpressure criteria stipulated under ‘HSW (Hazardous Substances) Regulations 2017, r 9.27’ that must be considered in the event of an unintended detonation. Overpressure relates to a significant increase in ambient pressure at a known location (measured in kPa). In the event of an unintended detonation, excessive overpressure would occur in close proximity to the site. Exposure to personnel and infrastructure to such overpressures must be managed. The managed areas surrounding such locations are known as ‘controlled zones’. In the event of an unintended detonation, consideration is given to the potential effects on personnel, infrastructure and buildings. The extent of such surface controlled zones is primarily reliant on the mass of the class 1 substance involved in the unintended detonation event and the distance to the exposure site at the surface location. Surface magazine facilities use a ‘hemispherical burst’ calculation methodology. In contrast, an unintended detonation within an underground storage facility is a different scenario, in which the vast majority of hazardous over pressure and hazardous fragments would likely be entirely contained within the underground mine workings and nearer to the storage facility itself. Estimates undertaken for likely overpressure scenarios at surface connections have been based upon a conservative model of the linear distance from the magazine storage location to the surface, which then allows calculation of underground mine volume. The volume of the shortest path to the surface connection plus the volume associated with the equivalent length along the other tunnel routes has been used in the calculations to estimate overpressures at surface. Additional underground areas (i.e., volume) within the proposed mine development, where overpressure would likely dissipate further, are not considered. It is expected that actual surface effects (overpressure in kPa) would be notably less than outputs calculated. In consideration of ‘ International Ammunition Technical Guideline (IATG 2.20), ‘Quantity and Separation Distances (United Nations - Safer Guard) (2nd Edition 01.02.2015) – ANNEX M’ , expected safety distances (controlled zones) at surface exits/ ventilation shafts can be calculated against specific criteria. These safety distances have then been scaled in order to provide alignment with New Zealand Regulatory requirements, and the associated kPa thresholds.
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