33 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Storage and use of hazardous substances at Willows Road site and the Wharekirauponga Underground Mine Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Table 5.3: Summary of calculated offset requirements for the proposed explosives storage site (GSS, 2021) Control zone offset distance (m) required for: Overpressure Site2 Vulnerable Facilities Inhabited building distance / Public traffic route Interior of buildings Public Places / Low density traffic routes Process building1 2 kPa 5 kPa 9 kPa 13 kPa 24 kPa Site 2 – Willows Portal < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 Site 3 – Willows Rd Farm Fresh Air Intake < 1.0 < 1.0 < 1.0 < 1.0 < 1.0 Site 4 – WUG Rise #1 3.8 3.5 2.9 2.3 < 1.0 Site 5 – WUG Rise #2 4.7 4.4 3.7 2.9 < 1.0 Site 6 – WUG Rise #3 3.8 3.5 2.9 2.3 < 1.0 1 Location of Class 1 explosives manufacture. 2 Site names have been aligned with those identified in more recent reporting for consistency The excluded activities are considered at each site with regards to the largest calculated overpressure radius inTable 5.4 below. Each surface connection will be installed such that the 13 kPa radius will fall within the 10 x 10 m perimeter fencing, either by limiting the diameter of the vent or by reducing the maximum quantity within the underground chambers. There are no activities that are required to be excluded under the HSW-HS for protection of people and structures (such as public traffic routes, vulnerable facilities etc.) anticipated within the controlled zone radii. Table 5.4: HSW-HS exclusion requirements of r9.27 Ref Exclusion from zone Blast overpressure Max. offset distance Comment 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 13 kPa 2.9 m Surface connections Site 1 and Site 2 are within OGNZL owned land with no nearby public access. The three sites (Site 4, Site 5 and Site 6) that are located in the Coromandel Forest Park could in theory be accessed by a member of the public. However, each 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 9 kPa 3.7 m
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