| Discharges to Air and Associated Mitigation Methods | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 20 It is possible to estimate the potential emissions of particulate matter from mining activities using emission factors developed primarily by the US Environmental Protection Agency (US EPA) and published in a number of publications including the US EPA AP 42 database.15 However for fugitive dust sources, such as those associated with the WNP, these emission factors have a large degree of uncertainty. For this assessment of potential effects, no attempt has been made to quantify the fugitive emissions from the mine as the scale and location of the dust sources will change constantly throughout the course of the project as new areas are mined and rehabilitated. Instead, the assessment method is based on comparing the existing and past effects of the mine with the potential effects of the new developments, taking into account any changes in the level of operation and the location of the developments in relation to the sensitive receptors. 3.2.3 Sources of particulates and proposed mitigation methods The activities that will take place that may generate dust are: ● Earthworks, including stripping of overburden and topsoil, mining of rock, construction and rehabilitation of roads, pits, noise bunds, tailings storage facilities and rock stacks ● Vehicle movements on unpaved surfaces ● Loading, conveying and unloading of materials ● Crushing and screening of rock and overburden ● Wind-generated dust from dry exposed surfaces such as roads and stockpiles ● Applying limestone to potentially acid forming overburden. These activities are addressed in the following subsections along with a summary of the proposed dust mitigation methods. Earthworks The stripping and spreading of soil and rock from surface areas , the construction of infrastructure such as roads, pit walls, noise bunds, TSF3, and the NRS, and the spreading of topsoil to rehabilitate disturbed areas have the potential to generate significant quantities of dust if appropriate mitigation is not carried out. To control dust from these activities, OGNZL proposes to continue to use the following methods which are described in the AQMP and are successfully utilised at the mine at present: ● Keep exposed surface areas to a minimum and re-vegetate exposed areas as soon as practical ● Use water sprays to keep surfaces damp where practicable and necessary ● Plan potentially dusty activities such as stripping and spreading of topsoil for days when weather conditions are predicted to be favourable. The National Pollution Inventory for Mining published by the Commonwealth of Australia16 (NPI Manual) estimates that the use of water to control dust on stripping, hauling and loading and unloading activities can reduce the emissions of dust by 50%. The NPI Manual also estimates that re-vegetation of overburden stockpiles reduces their dust generation capacity by 99%. Vehicles and roads Dust from heavy vehicles on haul roads, heavy vehicle traffic around the proposed TSF3 and NRS and general traffic around the proposed site works area all have the potential to be significant sources of dust if not adequately controlled. Dust from roads is controlled primarily by limiting the area of fine particles 15 United States Environmental Protection Agency (USEPA) AP42 Emission Factor Database Chapter 13. 16 Commonwealth of Australia “National Pollutant Inventory Emission Estimation Technique Manual for Mining Version 2.3” 2001.
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