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Ms. Christine Belka <br />Page 3 <br />June 11, 2018 <br />West Elk Mine surface crews are organized such that at least two certified opacity <br />observers are on shift at all times. Opacity observers monitor dust constantly during their <br />shift, but do not normally complete a written record of their observations. There is an <br />exception for a scheduled event such as a screen change or belt start-up when a Visible <br />Emission Observation Form is completed for the specific event. Additionally, opacity <br />observations of emissions from the scalping station and coal preparation plant are <br />performed on 12 month intervals assuming that the plant is running. <br />• Dust on roads and refuse piles is controlled by utilizing both water and magnesium <br />chloride. Two water trucks are employed on the site throughout the summer. <br />Magnesium chloride, in the form of the commercial product DustGard, is typically <br />applied site -wide in May each year, with a second treatment in August where necessary. <br />Controlling dust on coal stockpiles is complicated by the potential for spontaneous <br />combustion of coal within the pile, which is increased by excessive moisture. Moisture <br />content is a key parameter of the produced coal, which MCC monitors at a point on the <br />transfer conveyor before the coal reaches the stockpile. Maintaining the moisture content <br />at >7% is considered a Best Management Practice. MCC provided detailed mine records <br />which show that moisture content is generally in the range of 11-12%, with the average <br />for the month of May at 11.3%. <br />• When a stockpile is expected to remain dormant for an extended period of time, the <br />commercial product Soil Sement is applied to the surface for dust control. Due to <br />spontaneous combustion issues, water is applied to a coal stockpile only as a last resort. <br />During the I&E inspection, an MCC certified opacity observer demonstrated his observation <br />practice in the field. In accordance with Method 9, observations were made with the sun at the <br />observers back, with line of site over the top of the subject Run of Mine coal stockpile. An <br />estimate of the opacity of the air (the air's capacity to prevent the transmission of visible light) <br />was recorded at 15 second intervals over a 30 minute period. The observations were made in the <br />early afternoon when the wind strengthened and blew generally up the river valley, as is typical <br />for the time of the year. The estimated wind speed and direction was 5-10 mph from the NW, <br />with occasional stronger gusts occurring during the observation. Throughout the period of <br />observation a bulldozer was working the coal in the stockpile. At no time during the observation <br />period was an opacity greater than 5% observed. The geometry of the pile was such that when <br />dust was picked up from the surface it was on the upslope of the pile, on the pile's western flank. <br />As the wind gust died, the dust fell back towards the downslope side, within the stockpile <br />