14 | P a g e Class 1 Storage Location Assessment_Oceana Gold NZ Ltd Wharekirauponga Underground Mine NOTE – While Annex M indicated a specific QD factor for ‘Process Building Distance’ (PBD), an alternate QD factor was applied in order to align with ‘ HSW (Hazardous Substances) Regulations 2017’ , where controlled zone calculations reference 24 kPa as opposed to 21 kPa criteria indicated within Annex M of IATG 2.20. Controlled zone definition – 13 kPa r 9.27(2)(a)(i) - public traffic routes of low density and places where people may occasionally be present in numbers up to 200 persons on average in any 24-hour period are not subject to any of the following: i. a blast overpressure more than 13 kPa. This would be considered equivalent to ‘PTRD’ (Public Traffic Route Distance) within ‘ANNEX M’ . However, ‘ for minor routes, 2/3 of IBD may be used in all cases’ (77 x 0.66 = 51) Formula for minimum offset distance in accordance with the above criteria - D = 51 x HD x LD 1/3 Proposed class 1 site - Compliance summary for 13 kPa controlled zone. • This applies to any person in a public or private place within this zone irrespective of number or density. • Where ventilation shaft surface connections are located on public land (HDC paper road boundary), members of the public must remain outside this controlled zone. • Fencing will be constructed around each ventilation shaft surface connection. The fenced area will have dimensions of 10 m in diameter, concentric with the vent shaft (and will restrict public access. • Compliance with the 13 kPa controlled zone requirements at sites P2, P3 and P4 can be managed through design consideration of ventilation shaft diameters and or maximum allowable stored capacity for each magazine chamber. • The 13 kPa controlled zone remains within the HDC paper road boundary (and does not encroach DOC Reserve) • In the event of an emergency situation, all OGNZL personnel within this zone shall evacuate to 5 kPa controlled zone (minimum). • The zone will be managed by way of OGNZL ERP and an appropriate evacuation plan. Controlled zone definition – 9 kPa. r 9.27(2)(b)(i) - public traffic routes of medium density, places where people may occasionally be present in numbers up to 900 persons on average in any 24- hour period, and the interior of any proximate building within the boundary of the place where people not directly handling explosive substances are present are not subject to any of the following: i. a blast overpressure more than 9 kPa. Formula for minimum offset distance in accordance with the above criteria – D = 64 x HD x LD 1/3 Proposed class 1 site - Compliance summary for 9 kPa controlled zone. • This applies to public traffic routes of medium density, which are not present at any of the surface locations. • Applies to the interior of any proximate building on site not related to handling of explosives (e.g., office, lunch room etc.). • There is no exposure to any ‘un-related’ occupied building within the controlled zones on OGNZL land. • There is no impact where the controlled zones cross into public areas (either DOC Reserve or HDC paper road)
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