32 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 inFigure 4.1. These ponds are pumped to either the tailings storage facility or to the WTP, as appropriate. Figure 4.1: Location and capacity of tertiary containment ponds (Source: Aerial images from LINZ Basemaps) 4.11 Substance specific operational procedures The standard operating procedures for tasks involving hazardous substances are documented to ensure that these tasks are executed correctly and in a way that minimises the risk of an incident (such as including steps for tank capacity reconciliation to prevent overfilling). These procedures reduce the chance of operator error and include controls to minimise worker contact with the hazardous substances. Procedural steps to prevent spills or losses will also minimise the risk of a failure that could impact off site receptors. 4.11.1 Sodium Cyanide delivery, storage and use The solid sodium cyanide (cyanide) is stored in a bunded shed. The cyanide is mixed into an adjacent tank to form a cyanide solution (liquid cyanide) for leaching gold from the ore. The following specific controls apply: The liquid cyanide is stored in a bunded tank certified under the HSW-HS by an external compliance certifier, within a bunded shed to prevent spill or uncontrolled release to the workplace or environment. The shed is located in a secure fenced area with unauthorised access prohibited. As required under the HSW-HS, the cyanide facility is stored away from acids and other hazardous substances, including the pipework within the Processing Plant. Furthermore, the cyanide piping is completely isolated from the water network at the plant. In line with international pipework standards, all tanks/piping containing cyanide levels above 5% are painted purple for ease of identification. WTP collection pond Capacity = 1,287,000 L Processing plant collection pond Capacity = 4,015,000 L
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