45 Tonkin & Taylor Ltd Hazardous Substances Technical Assessment – Waihi North Project - Waihi Processing Plant, Water Treatment Plant and Development Site Oceana Gold (New Zealand) Limited June 2022 Job No: 1015212.1000 vRev0 Figure 7.1: Multi-Level Risk Assessment flow diagram Source: NSW-DoPl The risk assessment provides a screening level assessment, where all hazards in terms of their risk to people beyond the site boundary are assessed to identify any significant risks to off-site environments. Where these are limited to specific individual hazards, partial quantification is applied for potentially high consequence events with a low frequency of occurrence beyond the site boundary. A detonation in the explosives store is identified in the HSW-HS as a potentially high consequence event that requires assessment using empirical calculations. This is expanded upon for the Development Site in Section 7.3.2. 7.3 Risk assessment 7.3.1 Hazard analysis The hazards associated with hazardous substances are generally classified by effect as follows: Fire/Explosion Effects: concerned with damage to property, the built environment and safety of people; Human Health Effects: concerned with the well-being, health and safety of people; and Environmental Effects: concerned with damage to ecosystems and natural resources. These hazards are based on the intrinsic characteristics of the substance, for example the flashpoint of a flammable substance. Table 7.1 sets out the hazard analysis for the site, identifying and rating potential hazards. The hazard ratings, based on the failure pathway and affected environment, have been assessed as high for storage of cyanides, acids, mercury, LPG, oxidisers, diesel and explosives and low for spills of gasser and hydrated lime, quick lime and ferric chloride. Substances that, in the absence of controls, could have off site effects are evaluated in the qualitative risk analysis in Section 7.3.4 Where the residual risk of an event to an off site location could be significant, a partial quantitative review of the consequence is undertaken in Section 7.3.2 (in this case this has been considered for the Class 1 explosives).
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