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MCC estimates that a maximum of 18 MDWs might be in operation at a time in the <br />future, but to date, they have never utilized that amount. At the time of the <br />inspection, MCC was only operating six (6) pumps (three of which were pulling from <br />gob at the old mine face). In the collapsed gob sections behind the longwall, MDWs <br />remain active for a short period of time (may run for 6-10 weeks) before being sealed. <br />This mine did not begin to utilize MDWs until 2001, after high levels of methane were <br />encountered while mining the B seam. There is a large amount of gas trapped in the <br />strata between the B and E seams (E is located above the B seam), so during B <br />seam mining, there are much higher amounts of gas released as the above strata <br />collapses. Wells are monitored weekly by taking two gas velocity readings to <br />determine gas volume removed. Similarly, weekly bag samples are used to measure <br />methane concentration in released gas. <br />2. In historical sections of the mine with sealed panels, underground gob methane <br />drainage pipes (sometimes referred to as inseam mine drainage) keep background <br />methane from creeping into active areas. Surface blowers can pull a vacuum on <br />these sealed areas and release this concentrated gas stream uncontrolled. Gas from <br />historical sections is utilized during cold weather to fire large burners located on <br />intake air for the mine ventilation systems. <br />3. For methane which has crept into the mine ventilation air (was not removed prior to <br />the longwall or directly from the gob), four large ventilation shafts operate to provide <br />adequate air replacement (Point 019). The Sylvester Gulch fan is equipped with a <br />Joy 1,500 hp motor. Shaft #1 has a TILT Babcock fan which is rated at 2,500 hp. <br />Shaft #2 has two TLT Babcock fans, each rated at 2,500 hp, but is restricted to <br />operating only one (1) fan at any time. Shaft #3 operates a Joy fan rated at 1,500 hp. <br />The facility is restricted to operating with combined ventilation air throughput of <br />3,000,000 cfm, and typically operates around 1,350,000 cfm. Methane gas from <br />these points, although usually at concentrations below 0.5%, constitutes a large <br />percent of the methane emissions from the mine due to the high volume of air <br />movement. Emissions from this point also include particulate matter in the form of <br />coal dust and rock dust. Although several of the intake shafts were observed at the <br />time of the inspection, ventilation shaft exhaust points are located in the National <br />Forest in the hills above the mine, and were not observed during this inspection. <br />As will be discussed below in more detail, although most of the hydrocarbons released from the <br />coal bed gas are methane and ethane (exempt VOCs), a small percentage of the gas includes <br />non-exempt VOCs (i.e. Propane, Butane, Pentane, Hexanes, etc.). Because of the extremely <br />large amount of air/methane released from this facility, it is the Division's assertion that the <br />uncontrolled VOC emissions are also at a level above the permitting threshold. See 'VOC <br />Emissions Discussion' below for details. <br />It was also noted during the inspection that there are banks of burners positioned at the air <br />intakes of ventilation shafts. In total, there are twenty six (26) heaters at the facility, with the <br />following configuration: There are two banks of four burners (4 MMBtu/hr) located on each of the <br />fan intakes, which totals eight (8) burners on the Shaft #1 fan, and eight (8) on each of the Shaft <br />#2 fans (although only one Shaft #2 fan is used at any time). There is also a heater located at the <br />base of each of the two fan housings on Shaft #2. Therefore, although there are 26 total heaters, <br />the source can only operate a maximum of 17 burners at any given time (eight on Shaft #1 and <br />nine total on a single Shaft #2 intake). These burners combust mine gas from inseam gob <br />drainage pipes (three wells from sealed B seam panels) to heat intake air during periods when <br />ambient air is extremely cold. This not only provides heat to the mine, but also eliminates ice <br />buildup in the ventilation intakes. As reported in a records submission on January 11, 2013, the <br />source has operated a maximum of eleven (11) heaters at a given time. The combustion <br />emissions from this activity have not previously been reported to the Division, but appear to be <br />2012 Air Pollution Inspection <br />0510015-INSP-2012.docx Page 3 of 30 <br />