27 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 integral (double skinned) or a bund with capacity for 110% of the tank volume8,, the bunds are chemically resistant to the substance stored, equipment is adequately protected, and incompatible substances are segregated and do not come into contact within the bunded areas. Stored hazardous substances are adequately segregated based on quantity of materials stored, physical state, degree of compatibility, manufacturer's instructions and known material behaviour. The secondary containment minimum requirements for each substance are provided in Table 4.2 below. The PHMP provides a hazardous substances tank map and plant layout. This plan will be revised to include the increased volume wherever relevant once the upgrades are commissioned. An overview of the separation and segregation requirements for the proposed volumes is set out inTable 4.3 below. Table 4.2: Secondary containment minimum provisions for substances at the Processing Plant, WTP and Development Site Substance State Hazard Class Proposed maximum storage volume Storage location description Secondary containment minimum requirement (HSW-HS regulation ref) High calcium hydrated lime Liquid 8.2C, 8.3A 9.1D 306,000 L Three tanks (102,000 L each) at the north of the WTP Containment for at least 110% capacity of the largest container (r17.100) or integral containment1: 112,200 L High calcium quicklime Solid 8.2C, 8.3A 9.1D 70,000 kg Silo west of the Processing Plant Secondary containment not required for solid substances. Caustic soda (Sodium hydroxide 50%) Liquid 6.1D, 6.1E 8.1A, 8.2B 8.3A, 9.1D. 24,000 L Tank on the western side of the electrowinning area. Containment for at least 110% capacity of the largest container (r17.100) or integral containment1: 26,400 L Hydrochloric Acid (>25%) Liquid 6.1B, 8.1A, 8.2B, 8.3A, 9.1D, 9.3C 24,000 L Tank on the western side of the electrowinning area. Containment for at least 110% capacity of the largest container (r17.100) or integral containment1: 26,400 L Oxygen gas Gas 5.1.2A 30,000 L Cryogenic pressure vessel, east of the Processing Plant. Secondary containment not required for gases Carbon Dioxide Gas Not classified as hazardous 40,000 L Two cryogenic pressure vessels in the WTP Secondary containment not required for gases 8 The majority of liquid hazardous substances used by OGNZL are stored in designated tanks, which are required to have integral bunding or 110% containment under the HSW-HS. The only packaged liquids proposed are the maintenance oils, which are required to be provided with containment for at least 100% of the total pooling potential where they are stored.
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