57 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 Taking into account the controls and storage management in place, secondary containment and the tertiary containment provided by the collection ponds, the effect on the environment from a spill has been assessed as less than minor. 8.2.3 Cumulative effects The OGNZL activities are the only large-scale industrial activity within the immediate area. A small industrial zone is located 2.1 km to the south-west and the Martha Open Pit mine is located approximately 1.4 km to the west of the Processing Plant. The nearest petrol stations (BP and Gull) are located 1.9 km away in the centre of Waihi along Route 2. The Martha Open Pit has associated diesel and explosive magazine storage which could have cumulative effects with the Processing Plant in the event of a simultaneous spill of ecotoxic substances or fire on site. The significant separation between these two locations prevents the spread of fire. Additionally, the controls and management measures implemented by OGNZL across both sites mean it is unlikely that two spill or fire events on separate sites would occur. The likelihood of another facility or OGNZL site having a spill or fire resulting in cumulative effects is considered negligible. Small spills on site will be contained and managed as described in the previous section, so there will be no cumulative long-term effects on the environment as a result of this type of incident. OGNZL has implemented controls, as outlined in the above section, to contain larger spills which could have an adverse impact on people and the environment. In the case of cyanide, additional structural controls are in place to prevent the substance leaving site in the event of an accidental spill. The likelihood of a failure of controls during simultaneous spills resulting in cumulative off site effects are negligible. The risk of cumulative effects of fire between flammable or oxidising substance storage on site is managed through separation between storage areas, so that a fire cannot spread from one area to another on site. In addition, firefighting controls, such as water pumps and firefighting equipment, are available on-site to prevent a fire spreading beyond the boundary. These controls will also minimise the risk of a fire spreading to adjacent properties. The site is predominantly surrounded by rural farming land with an approximate 400 m buffer zone between the plant and a residential property. Cumulative effects from the storage of hazardous substances at the Processing Plant and WTP are considered less than minor and can be managed. With regards to explosives, the greatest risk posed by the proposed storage the Development Site is an accidental detonation. Storage of explosives at the previously established storage site, approximately 1.2 km west of the proposed Development Site, is the nearest comparable activity. Other explosives storage includes surface storage at the Martha Open Pit located 2.9 km from the proposed store, and an underground facility also proposed to be established 2.2 km northwest in the residential zone over 300 m beneath the surface. All of the existing and proposed explosives storage activities are well beyond the 2 kPa blast overpressure radius for the proposed storage at the Development Site. The risk from each can be individually assessed, as there is no increased risk of explosion propagation between the stores. Each site will be managed in accordance with the relevant controls described in Section 4.12, including strict site security, exclusion of ignition sources and incompatible materials, and provision of fire suppression systems. The risk of cumulative effects from explosives storage is negligible.
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