47 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 restrictions. The largest overpressure area around any of the vent locations is the 2 kPa zone, within which vulnerable facilities are restricted from being present under the HSW-HS. This zone extends in the maximum case to 4.7 metres from Site 4, a return air riseimmediately above the WUG. No structures will be permitted at this proximity to the surface vents, and beyond the 2 kPa radius (which extends to 2.5 m beyond the perimeter fence in the maximum case), the overpressure level decreases to a negligible level. The New South Wales Department of Planning HIPAP-4 provides the expected effect of various levels of explosion overpressure as reproduced inFigure 7.2 in Section 7.3.2.1. The injury probability at the 5 kPa boundary is expected to be lower than 10% and the probability of injury will decrease with distance from the boundary. Minor and repairable damage to glass or partitions could be expected on a building near the OGNZL boundary. The off-site risk to people or property from an accidental detonation associated with the storage of explosives has been assessed as low to people and structures within the 2 – 5 kPa radius. An AQA provided as Appendix I has evaluated the potential impact on human health from discharges of CO, NOX (as NO2) and NH3 at the surface connections in the event of a complete detonation of a Class 1 explosives storage chamber underground. In this scenario, the predicted ground level concentrations within 2 km of the vents comply with the assessment criteria for each contaminant. The maximum contribution to concentrations at the surface is predicted for NOX, which cumulative with the background concentration for rural areas is less than half the 1-hour average National Environmental Standard for Air Quality for NO2. The maximum cumulative concentration for CO is 2.7% and for NH3 is 5.4% of the relevant criteria for the protection of human health. The location of this maximum prediction is in the forested area approximately 130 m from the surface connection and over 800 m from the nearest public walkway. Given the high degree of conservatism in the assessment, the effects to people from air discharges from the WUG in the event of an unplanned detonation are less than minor. The off-site risk to people or property from an accidental detonation associated with the storage of explosives has been assessed as low. The controls in place to mitigate the risk include the appropriate design, testing, certification, operation and maintenance of the explosives magazines or underground chambers in accordance with the HSW-HS requirements (including for security, lightning strike protection), segregated storage areas and loading zones away from other flammable or explosive substances and away from buildings, and an Emergency Management Plan. Workers on site will be trained in emergency response as per the Emergency Management Plan. Likewise, the risk of a fire at the ANE store or diesel storage locations both above and below ground or at the SFA workshop (storage of oxygen and acetylene gases) are appropriately managed through restriction of ignition sources, incompatible materials and access by personnel other than trained workers. The SFA where the oxidisers, acetylene and diesel are stored at the Willows Road site is greater than 180 m from any off-site dwellings. Taking into consideration the proposed controls to manage the hazards, the isolation of the activity and the separation distance to the closest dwelling, the risk of effects on people or property from an accidental detonation at an explosives store or fire at the oxygen gas, acetylene, ANE or diesel storage locations have been assessed as low. Provided the controls and mitigations are in place as outlined above, the effects on the people and property are expected to be less than minor. 8.2.2 Effects on the environment The risk to the environment from a spill to the environment associated with the use and storage of ANFO, packaged explosives/boosters/detonators and ANE has been assessed as low due to the physical properties of the substances, which are respectively: a granular solid, small packaged articles and a highly viscous emulsion. The mechanical oils and greases are typically not classed as hazardous and will be stored and used in bunded, sealed areas at the workshop near the portal
RkJQdWJsaXNoZXIy MjE2NDg3