| Air Discharges and Associated Mitigation Methods | WNP Wharekirauponga Underground Mine - Assessment of Effects of Discharges to Air | 4397169-66885702-23 | | 29 5 Air Discharges and Associated Mitigation Methods 5.1 Overview The air discharges from the Willows Road project area will be of a similar nature as those from the existing Martha Pit and underground mines but on a smaller scale and across a shorter timeframe. A draft Air Quality Management Plan (AQMP)13 has been prepared for the project site based on the mitigation methods used by OGNZL to control any adverse effects of dust on the environment from the Waihi mining operations. The potential discharges to air from the Willows Road site will be generated from the following sources: ● Dust from surface sources (earthworks, topsoil stripping, vehicle movements, unconsolidated surfaces, stockpiles and materials handling) ● Products of combustion from surface vehicles ● Products of combustion from underground vehicles, dust from excavations discharged via portal and ventilation raises and contaminants from underground blasting ● Rehabilitation of surface areas after development of the tunnel. Once construction of the surface infrastructure is complete, the most significant sources of discharges to air within the site will be the placement of rock on the 20m high WRS and removal and recontouring of the progressively reclaimed stack. 5.2 Dust from Surface Sources 5.2.1 Nature of dust The predominant contaminant discharge from the surface activities will be particulate matter (or dust) consisting of a wide range of size fractions. The larger settleable material is generally greater than 50 µm in diameter and has the potential to create a nuisance by soiling surfaces and causing irritation to eyes and the nose. However, because it is relatively large in size, this settleable material is usually deposited onto the ground within a short distance (approximately 100 - 200 m) from the source. The finer fractions of dust (commonly referred to as total suspended particulate or TSP) are generally less than 20 µm in diameter and can be transported longer distances downwind. The portions of TSP that pose the greatest risk to health are those 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 finer particulate in the atmosphere is from the products of combustion. While most of the particulate generated from the project’s surface activities will be larger fractions (i.e greater than 10 µm), a portion will fall into the smaller size ranges. The material to be excavated at the project site may contain crystalline silica. Consequently, the dust created during any mechanical processes will also contain a proportion of crystalline silica. Fine particles of crystalline silica (less than 10 µm) that are able to be inhaled deep into the lungs, known as respirable silica, can cause significant adverse human health effects (silicosis) if people are exposed to concentrations above recommended guideline levels over extended periods of time. Mechanical crushing is not proposed at the project site but some minor amounts of finer dust, that may contain crystalline silica, may still be generated at the rock stacks and during materials handling and from vehicle movements on unpaved WRS haul roads. 13 Copy attached to AEE report prepared by Mitchell Daysh (2022)
RkJQdWJsaXNoZXIy MjE2NDg3