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May 23, 2018 C-1980-007/West Elk Mine LDS <br /> <br /> <br />Number of Partial Inspection this Fiscal Year: 8 <br />Number of Complete Inspections this Fiscal Year: 4 <br /> <br /> Page 3 of 13 <br /> <br />Collectively MCC staff described and explained their practice as it relates to the control of dust. Key points of the <br />discussion are summarized below: <br /> Fugitive dust is measured according to a process detailed in Method 9 - Visual determination of the <br />opacity of emissions from stationary sources (https://www.epa.gov/emc/method-9-visual-opacity) <br /> Method 9 requires observers to be certified to ensure that their observations of opacity are calibrated <br />against a standard. Certification of opacity observers at the mine is carried out twice annually by Opacitek <br />Environmental Solutions (http://opacitek.com/). As of March 16, 2018, MCC had 24 certified opacity <br />observers on staff. <br /> The surface crews are organized such that at least two certified observers are on shift at all times . <br />Observers monitor dust constantly during their shift, but do not normally complete a written record of <br />their observations; the exception is for a scheduled event such as a screen change or belt start-up, when a <br />Visible Emission Observation Form is completed for the specific equipment concerned. Additionally, <br />opacity observations of emissions from the scalping station and coal preparation plant are performed on 12 <br />month intervals assuming the plant is running. <br /> Dust on roads and refuse piles is controlled using both water and magnesium chloride. Two water trucks <br />are employed on the site throughout the summer, (their presence during inspections is so ubiquitous that it <br />is not generally noteworthy). Magnesium chloride, in the form of the commercial product DustGard <br />(http://www.gmcocorp.com/dust-control), is typically applied site-wide in May each year, with a second <br />treatment in August where necessary. <br /> Controlling dust on coal stockpiles is complicated by the potential for spontaneous combustion of coal <br />within the pile, which is increased by excessive moisture. Indeed, moisture content is a key parameter of <br />the produced coal, which MCC monitors at a point on the transfer conveyor before the coal reaches the <br />stockpile. Maintaining the moisture content at >7% is considered a Best Management Practice; detailed <br />mine records show that moisture content is generally in the range 11-12%, with the average for the month <br />of May at 11.3%. <br /> When a stockpile is expected to remain dormant for some time, the commercial product Soil Sement <br />(http://midwestind.com/soil-sement/) is applied to the surface for dust control. Due to spontaneous <br />combustion issues, water is applied to a coal stockpile only as a last resort. <br /> <br />Ty Hiatt is a certified opacity observer, and demonstrated his observation practice in the field for the <br />Division’s inspectors. In accordance with Method 9, observations were made with the sun at his back, looking <br />over the top of the Run of Mine coal stockpile. An estimate of the opacity of the air (that is, the air’s capacity to <br />prevent the transmission of visible light) was recorded at 15 second intervals over a 30 minute period. The <br />observations were made in the early afternoon when the wind, as is typical for the time of year, strengthened and <br />blew generally up the river valley. The estimated wind speed and direction was 5-10 mph from the NW, with <br />occasional stronger gusts. Throughout the period of observation a dozer was working the coal in the stockpile. At <br />no time during the observation period was an opacity greater than 5% observed. The geometry of the pile was such <br />that when dust was picked up from the surface it was on the upslope of the pile, on its western flank; as the wind <br />gust died the dust fell back on the downslope side, within the stockpile footprint. It’s likely that a stronger wind <br />with more sustained gusts would transport dust further. Vegetation immediately adjacent to the stockpile area