| Air Discharges and Associated Mitigation Methods | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 31 The National Pollution Inventory for Mining (NPI Manual) published by the Commonwealth of Australia16 estimates that the use of water to control dust during stripping, hauling and unloading activities can reduce the emissions of dust by 50%. The Manual also estimates that re-vegetation of stockpiles reduces their dust generation capacity by 99%. 5.2.4 Vehicles and roads Heavy vehicles on unsealed access roads and general traffic around the project site works area have the potential to be significant sources of dust if not adequately managed. Dust from roads is primarily controlled by limiting the area of fine particles exposed to wind, keeping surfaces damp and controlling vehicle speeds. The following mitigation methods will be used by OGNZL to control dust from vehicles and haul roads: ● Limit vehicle speeds on unsealed haul roads and access roads within the project site ● The main entrance road to the site is to be sealed ● Minimise haul distances as far as practicable ● Regularly grade unsealed roads and keep laid with fresh gravel/rock ● Use approved surface binding agents for dust control where practicable and cost effective ● Require traffic to use wheel wash facilities located at main exits to prevent mud and debris being tracked offsite. Speed controls on vehicles have an approximately linear effect on dust emissions. OGNZL will impose speed limits on site that are appropriate to the nature of the traffic and the design of the road. The number of vehicles on site will be greatest during construction of the surface infrastructure facilities, which will be established prior to commencement of tunnelling. Once tunnelling commences, trucks will haul material from the tunnel to the rock stacks. Work vehicles will include two 45 tonne trucks, a grader and a water cart. 5.2.5 Loading and unloading topsoil and rock The loading of material onto and off trucks has the potential to generate dust. During construction, trucks will be loaded with topsoil before discharge to stockpiles. Once tunnelling is underway, trucks will unload tunnelled rock onto the WRS. The following methods will be used by OGNZL to control dust from loading and unloading trucks: ● Wet underground rock prior to loading and cartage to surface ● Require machinery operators to minimise drop heights when unloading materials on to stockpiles and rock stack ● Dampen topsoil before it is moved where practicable. 5.2.6 Exposed surfaces Exposed surfaces such as those on rock stockpiles, topsoil stockpiles, unvegetated noise bunds, ponds under construction and yard areas are potential sources of dust unless appropriately managed. The primary means of controlling dust on exposed surfaces is by revegetation wherever practical and keeping surfaces damp. The following methods will be used by OGNZL to control dust from exposed surfaces: ● Keep operational areas around stockpiles damp using a water cart as far as practicable ● Plant and maintain sustainable vegetation cover on topsoil stockpiles and the noise bund (grassed or hydroseeded) to prevent erosion and dust generation 16 Commonwealth of Australia (2001) National Pollutant Inventory Emission Estimation Technique Manual for Mining Version 2.3.
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