6 | P a g e Class 1 Location Assessment Development Site – Surface Magazine, Waihi North Project 4.1. Operational and Product Storage Capacity Requirements Project consumption forecasts estimate that stored capacities of approximately 6,412 kg will be required. It is forecast that restocking of class 1 substances will be required on a weekly basis. During peak usage periods, a more frequent replenishment program may be required. The proposed storage would typically consist of up to approximately 12,000 detonators (I.E – 12 kg NEQ), and an aggregate quantity of up to 6,400 kg NEQ of High Explosives (H.E). The stored H.E component would comprise of varying commercial explosive products to meet operational needs. 4.2. Controlled Zone Considerations Part 9. r 9.27 of the ‘HSW (Hazardous Substances) Regulations 2017’ explains that the ‘PCBU is to control adverse effects of unintended initiation’. One method of achieving compliance with this section of the regulations is by way of managing the ‘controlled zones’. There are varying ‘overpressure’ (kPa)’ threshold criteria (Section ‘ r 9.27’ ) applied to class 1 locations that relate to the different controlled zones. The overpressure thresholds are proportional to the stored NEQ. The potential effects on nearby infrastructure/ buildings/ personnel in the event of an unintended detonation are considered when determining stored NEQ. In addition to managing controlled zones, evacuation zones may be an appropriate means of achieving compliance with regulatory requirements by limiting risk exposure to people (by way of ‘hazardous fragments/ m2’). The determination of evacuation zones and a Trigger Action Response Plan (TARP) form part of the Emergency Response Plan (ERP). Threshold overpressure management is effected in one of two ways. That is, either by total NEQ stored, or by altering the distance of the storage location in relation to infrastructure, buildings or personnel. Controlled zone offset requirements have been derived from calculations considering ‘ TNT Equivalence’ as the donor explosive, referencing ‘International Ammunition Technical Guideline (IATG 1.80) - Formulae for Ammunition Management’, Part 6.2.1, Table 9a, Kingery and Bulmash - Polynomial for Incident Pressure (Hemi-Spherical Surface). and ‘ Part 5 Table 1: Hopkinson-Cranz Scaling Law’. Refer to ‘ TNT Equivalence’ in ‘Terms and Definitions’. Controlled zone offset requirements have been based on the greatest offset distance in relation to the stored NEQ specific to each individual magazine within the class 1 storage facility. In addition, a total controlled zone contour has been developed. This is an aggregate of all of the controlled zones associated with each individual magazine unit. Where I.E magazines are positioned within minimum IMD for ‘other explosives storage’ as per ‘ Table 3.2.3.2 of AS 2187.1 ’, the aggregate NEQ for relevant H.E and I.E magazines is used to calculate the controlled zone area. Whilst the I.E magazine positioning may be altered to suit operational needs, the offset distance between I.E and H.E magazines is to be maintained in accordance with ‘ Table 3.2.3.1 ’ of ‘ AS 2187.1’ . 4.3. Controlled Zone Considerations Relating to Regulatory Thresholds The paragraphs below outline the regulatory definitions for each of the controlled zones and how the proposed class 1 storage location will achieve the necessary compliance. Controlled zone definition – 24 kPa r 9.27(4)(a) – A PCBU with management or control of a hazardous substance location that is used solely for securing and holding a class 1 substance must limit the quantities of any class 1 substance at the location to ensure that, in the event of an unintended initiation, -
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