2022-02-22_PERMIT FILE - C1980007 (5)

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West Elk Mine 2.04-49 Rev. 11/04- PR10, 04/06- PR10, 09/07- PR12, 10/08- PR14; 01/22- MR459 and are also likely in some areas of the E Seam mine, but are less common in the B Seam mine due to the more competent and consistent nature of shales in the B Seam roof. Methane Methane gas as encountered at West Elk Mine is derived from the coals and carbonaceous strata of the local stratigraphic sequence. Analyses by Schlumberger Reservoir Technologies (2001, 2002, and 2003) suggests that methane gas is contained in the B Seam. More importantly, it was also determined that substantial methane gas is contained in the coal seams and strata above the B Seam. The Rollins Sandstone, an aquitard, does not contain much, if any, gas. Methane gas is liberated from cleats, faults and fractures during development mining and from the overlying strata that is broken during longwall retreat mining. Geologic structures such as the tectonic fault systems and, to a lesser degree, the compactional faults and clastic dikes, serve as conduits for both water and gas liberation. Exploration drilling throughout the past several decades in and around MCC’s coal leases has detected minor amounts of gas during drilling. Methane desorbtion testing conducted in 1996 on drill core determined that, on the average, the B Seam contains 150 scft (standard cubic feet per ton) of methane and the E Seam contains 125 scft or less, depending on the depth of cover. One measure of gas available to the mine environment is total Gas In Place (GIP). The GIP roughly coincides with overburden depth as measured in standard cubic feet of gas per acre (SCF/A). For example, the B Seam GIP under West Flatiron at 2,200 feet of cover was 15,000 to 17,000 SCF while the E Seam under 1,000 feet of cover was projected at 5,000 to 7,000 SCF/A. The GIP for the western district of the B Seam mining at West Elk Mine ranged from 0 to 12,000 SCF/A at the B South Mains increasing to the east. Existing mine ventilation systems were able to safely dilute the gas and allowed for normal mining practices. Below and on the flanks of West Flatiron Mesa, the GIP increased with the depth of cover. The volume of methane liberated from the overlying strata during longwall mining overwhelmed the mine ventilation system, forcing MCC to drill large diameter Mine Ventilation Boreholes (MVBs) (formerly called Methane Drainage Wells (MDW)) in advance of mining. The MVBs functioned as discreet ventilation conduits to drain-off the liberated methane after the longwall had passed the MVB and the B Seam roof strata had caved and fractured within the area of influence for each MVB. The MVBs have provided additional methane ventilation capacity that have and will allow for near normal mining practices in the B Seam. The GIP for the E Seam, with shallower cover and closer proximity to outcrop, is more characteristic of the western B Seam mining districts. A maximum of 8,000 SCF/A was projected for the eastern fringes of E Seam mining. MVBs have been used and are planned for the E Seam in case methane levels or other operating criteria warrant their use. A typical plan for methane ventilation includes a spacing of approximately 750 feet on center.