31 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 Substance name Identified separation requirements Comments LPG Segregation from all Class 1, Class 2.1.2, Class 3, Class 4 and Class 5 substances The separation distances specified for 80,000 L of Class 2.1.1 flammable gas are as follows: 12 m to public places 20 m to protected places The new location of the LPG tanks will provide approximately 80 m separation to the Ohinemuri River running between the Processing Plant and the OGNZL landholding to the east. The move increases the separation to the nearest residences, located on OGNZL owned land on Boyd Rd approximately 700 m northwest of the new location. The relocated LPG tanks will be closer to the proposed Class 1 explosives store in the Development Site, however these activities are still separated by approximately 750 m. Compliance certification issued to OGNZL shows compliance for hazardous substances location10 along with inspection certificates validating that the tanks meet the requirements of the Health and Safety in Employment (Pressure Equipment, Cranes, and Passenger Ropeways) Regulations 1999 for pressure vessels11. Diesel Segregation from all Class 1, Class 2, Class 3.2, Class 4 and Class 5 substances Separation requirements for the tank sizes proposed (6,000 – 40,000) are 3 – 5 m from protected places or the boundary. Diesel will be stored in relocatable isotainers and small portable tanks. These will be located to comply with all identified segregation and separation requirements. Hydrogen peroxide 5.1.1B substances should be 3 – 5 m away from incompatible substances, specifically Class 1, 2, 3, 4, 5.2, 6.1A-C, or 8, zinc, magnesium, any metal in powdered form, and combustible materials. Separation distances: 15 m away from protected areas 8 m away from public areas 5 m from ignition source The hydrogen peroxide is stored in two tanks at the WTP, separated from buildings on site. The nearest boundary is approximately 180 m to the east. 4.10 Tertiary containment All hazardous liquid stores at the Processing Plant and WTP are provided with dedicated secondary containment. However, as a further failsafe measure in the event that primary and secondary containment fails or there is a spill in an unbunded area during product delivery, the plant areas drain to two engineered collection ponds on site to retain any overflow from bunded areas, shown 10 HazSubs services limited, issued 12 September 2021, Compliance certificate for hazardous substances location of 2.1.1A LPG substances (includes two 40,000L bulk tanks and 250 Kg forklift cylinders). 11 Inspec Ltd, issued 31 August 2020, Certificate of External Inspection for LPG storage pressure vessel x 2
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