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

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West Elk Mine 2.04-47 Rev. 11/04- PR10, 04/06- PR10, 09/07- PR12, 10/08- PR14; 01/22- MR459 initially produced more than 2,000 gpm in the spring of 1996. The flow rate steadily diminished to a rate of approximately 85 gpm, and then ceased when the same fault system was encountered to the northeast in the 14 Tailgate in early July 1997. Flow at this intercept was initially about 200 gpm, which diminished to less than 100 gpm. The BEM fault zone was again encountered down-dip in 22HG with an initial flow rate of 3,500 gpm, declining to 200 gpm within two weeks. Encountered down-dip once more in 22TG, the initial flow was 3,000 gpm, declining to 370 gpm within one week and 200 gpm within two weeks. This fault water flow continues as a mine floor spring of approximately 120 gpm. A more thorough discussion of this unprecedented B East Mains fault inflow can be found in Section 2.05.6(3). The second fault (known as the 14 Headgate fault) had an initial estimated inflow rate of approximately 8,000 gpm when encountered on January 20, 1997. Subsequent intercepts in 14TG and 22HG on the down-dip extension of the fault zone yielded water inflows up to 200 gpm. The differences in initial flow rates can be attributed to the diminishing fault offset to the north in 22HG (reduced storability) and increasing offset to the south (increased storability) from the initial intercept in 14HG. At 14HG the total displacement on the zone was 11 feet. Going northeast, the 14HG fault zone displacement decreased to 8 feet in 14TG, 1 foot in 22HG, and mere inches in 22TG. Southeast along the same system, displacement increased from 8 feet in 14HG to 15 feet in 15HG, 18 feet in 16HG, 22 feet in B South Mains, and 15 feet again in 13AHG. The overall relationship between fault offset and damage zone water storage and inflow rates became obvious. Given these previous mine inflows, MCC believes that similar conditions may exist in future mining areas and has developed water handling systems within the mine to manage potential future large-volume inflows (See 2.05 Operations Plan, Hydrologic Protection During Operations, and Exhibit 69). E Seam mining encountered many of the same fault systems and inferred zones not intercepted in the B Seam. Mayo (2004) projected the previously intercepted fault zones would have insignificant nuisance waters associated with the fault zones and anticipated inflows from either Rollins or Bowie sandstones will be small or non-existent. The exception may be where tectonic faults have crossed sandstone roof channels, allowing the channel and fracture damage zones to store water. Inflows from the sandstone channels may reach 500 gpm in that instance. Inflows into the E Seam mine workings could be up to 2,000 gpm from un-intercepted tectonic faults. This value reflects possible damage zone widths, distance to outcrop, and vertical elevation. Sandstone Channel Deposits Zones of abrupt lithologic changes, such as those created by sandstone channels, historically coincide with areas of unstable roof. Numerous slickensided fractures in weak shales, claystones, and coal near sandstone channels can result in localized mine roof control problems. Based on MCCs prior mining experience, the two primary conditions of concern are: 1) Rapid changes in lithology from the resistant sandstones and siltstones of channel deposits to claystones, and 2) Shales and sandstones subject to differential compaction and stresses, producing slickensides. The presence of perched ground water in the sandstone channels aggravates these conditions by weakening the associated shales. The 40-foot zone above the F Seam appears to contain channel deposit trends or systems. About 30 percent of the lease block may be affected in the E Seam. The channel systems have a