| Discharges to Air and Associated Mitigation Methods | Waihi North Project Air Discharge Assessment - Waihi Surface Facilities | 4396626-1331619777-99 | 16/06/2022 | 18 3 Discharges to Air and Associated Mitigation Methods 3.1 Overview The nature of the emissions from WNP will be the same as the nature of the emissions from the existing Martha and underground mines and associated infrastructure and Processing Plant. The location and scale of some of the individual sources will change as a result of some of the new mine features. OGNZL has an Air Quality Management Plan (AQMP) for the current mining operations, which includes the mitigation methods used to control the effects on the environment, including dust. A revised AQMP will be prepared, which will detail the mitigation methods currently used by OGNZL, as well as any additional methods that are proposed to mitigate any requirements specific to the WNP (refer to Section 8). The potential discharges to air from the southern portion of the WNP will be generated from the following sources: ● Dust from surface mining activities such as earthworks, excavation, topsoil stripping, vehicle movements, unconsolidated surfaces and materials handling ● Relocation and construction of site roads ● Products of combustion from vehicles ● Contaminants produced from blasting ● Rehabilitation of completed mine areas ● Contaminants from the Processing Plant and Water Treatment Plant expansions Each of these sources and their associated mitigation methods are discussed in the following sections of the report. 3.2 Dust from Surface Sources 3.2.1 Nature of dust The predominant discharge from the proposed activities will be particulate matter. The particulate matter or dust will comprise a wide variety of size fractions. The larger settleable material is generally greater than 50 µm in diameter and has the potential to create a nuisance due to soiling of surfaces and by causing irritation to the eyes and nose. Because it is relatively large in size, deposited particulate usually falls out of the air within a short distance (approximately 100 – 200 m) from the source. The finer fraction of dust is defined as suspended particulate and is commonly referred to as Total Suspended Particulate (TSP). TSP can include particulate matter up to 50 - 100 µm in diameter but the majority would be generally less than 30 µm in diameter. However, it is the smaller particles with diameters less than approximately 20 µm in diameter which can travel large distances downwind. The portions of TSP that pose the greatest potential risk to health are particulates less than 10 µm in diameter (known as PM10) and particulates less than 2.5 µm in diameter (known as PM2.5). The major source of the finer particulate in the atmosphere is combustion processes. The particulate generated from the surface mining activities is likely to be predominantly made up of the larger size fractions (greater than 10 µm), but a portion will fall into the smaller size ranges.
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