55 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 Overpressure zones have been conservatively estimated by Global Seismic Solutions (Appendix A) for the Class 1 explosives storage proposed for the Development Site, for the purpose of selecting a magazine location that complies with the offset distances required in the HSW-HS regulations for the protection of the public. These overpressure zones enable consequence analysis for the impact of an unintended initiation. The boundary of the neighbouring rural property is 330 m northeast of the proposed Class 1 explosives storage facility at the closest point, and while no buildings are currently established on the section of land within the overpressure zone, future use of the land cannot be guaranteed. Therefore, the storage of explosives has been identified to have potential risks to offsite persons or public. As discussed in the partial quantitative analysis in Section 7.3.2, there are areas of neighbouring rural land that fall within the 2 kPa – 5 kPa blast overpressure radius. While there are currently no dwellings in the area of overlap, there are no restrictions on dwellings being established in future on the rural property. Under the HSW-HS regulations, restriction are placed on overlap with areas that may experience adverse effects at the identified overpressure levels. There are no restrictions on buildings with fewer than 4 storeys being located in the 2 kPa – 5 kPa radius area unless they are being used for hospitals, early childcare centres or vulnerable facilities of similar scale. 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. The injury probability at the 5 kPa boundary is expected to be lower than 10% and the probability of injury further decreases with distance from the OGNZL 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. The controls in place to mitigate the risk include the design, testing, regular certification auditing and maintenance of the explosives magazine location in accordance with the HSW-HS requirements (including for security, lightning strike protection), access restricted to trained Certified Handlers, segregated storage areas and loading zones away from other flammable or explosive substances storage and away from buildings, and an Emergency Management Plan. Workers on site are trained in emergency response per the Emergency Management Plan. Taking into consideration the proposed controls to manage the hazards, the isolation of the activity and the separation distance to the closest dwelling, the effect on people or property from an accidental detonation at the explosives storage facility have been assessed as less than minor. Spill risk to people and property The risk to people and property from a spill of acid, caustic soda, hydrated lime, hydrogen peroxide, mercury or cyanide has been assessed as low. The hazardous substances mentioned are stored in secondary containment within the Processing Plant or WTP, segregated from incompatible substances, and where handling substances that have potential for serious injury to humans e.g. corrosive to dermal or ocular tissue, these handling systems are automated to reduce human interaction and prevent overfilling. Emergency response plans for spill events have been prepared for the site and are regularly drilled by trained staff. Mercury storage poses a risk to both people and environment in the event of an accidental release. However, as mercury is stored in small amounts (maximum 10 kg) within secure containment in the gold room, it is considered a low risk of impacts off site. Mercury is anticipated to be produced as a by-product of the processing of ore from Gladstone Pit, and small amounts will be collected. Standard operating procedures and controls will be in place during smelting, handling and disposal of mercury, and these controls include establishing a secure retort oven and extraction system for mercury collection, tracking of mercury quantities, designation of trained and certified handlers, and
RkJQdWJsaXNoZXIy MjE2NDg3