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2022-09-29_PERMIT FILE - C1980007 (2)
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2022-09-29_PERMIT FILE - C1980007 (2)
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Last modified
10/6/2022 2:39:13 PM
Creation date
10/6/2022 2:29:35 PM
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Template:
DRMS Permit Index
Permit No
C1980007
IBM Index Class Name
Permit File
Doc Date
9/29/2022
Doc Name
pg 2.05-200 to 2.05-300
Section_Exhibit Name
2.05.6 Mitigation of Surface Coal Mining Operation Impacts Part 2
Media Type
D
Archive
No
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West Elk Mine <br />• Monitoring of mine inflows throughout more than 20 yeazs of mining operations has shown that <br />little mine inflow and consequently little groundwater drawdown within the overburden has <br />occurred in areas of greater than 500 feet of overburden cover and at distances more than 1,000 <br />feet from the subcrop. Mine inflows other than those resulting from the damaged fault systems, <br />aze generally observed to dry up or generally diminish to wet seeping areas within one to two <br />weeks. Similarly, the mine inflows associated with the BEM and 14HG fault systems have <br />diminished over time, to relatively constant dischazge rates which aze apparently equivalent to <br />their rechazge rates. With the exception of these fault inflows, the more prominent inflows to the <br />mine generally occur in areas of low overburden cover and/or in newly opened mine workings. <br />Permeability in and neaz the E and B Seams under 500 feet or more of overburden cover is low <br />(on the order of 5x10.6 cm/sec or less) based on estimates from slug test data (see Exhibit 17). <br />Because of these low permeabilities, inflows into the mine (excluding fault inflows) in the <br />current permit and South of Divide permit revision azeas aze expected to remain neaz historic <br />levels. <br />Prior to encountering the fault system inflows, WWE concluded that the annual mine inflows <br />were predominantly a function of the amount of newly opened mine workings and the magnitude <br />and distribution of precipitation. Future mine water inflows resulting from primary porosity aze <br />expected to be similaz to historic inflows and substantially below the estimates provided by <br />previous analytical models. This conclusion is further supported by Booth (1986) who reported <br />relatively constant inflow rates over a 12-year period to the Lancashire No. 20 underground coal <br />mine in Pennsylvania. Inflows to the longwall mining operation correlate well with the annual <br />area mined and appear independent of the total area mined. Inflow rates associated with fault <br />systems similar to those encountered in the eastern portion of the B Seam mine workings will be <br />dependent on storage and rechazge capacities. These factors aze a function of the fault system <br />geometry and interconnectivity with its recharge source. <br />Having identified as many as seven possible fault systems in the eastern portion of the <br />permit area and having experienced inflows associated with at least three of them, it is now <br />possible to estimate the potential inflows that may be associated with these fault systems. <br />While initial inflows may be several thousand gallons a minute, long-term inflow rates have <br />generally been less than 200 gpm from each of the major fault systems and migrated as new <br />encounters with these fault systems have been mined through in a down-dip direction. <br />In association with the Jumbo Mountain permit application in 1994, MCC conservatively <br />estimated that the B Seam and F Seam mines, including the Jumbo Mountain lease tract, could <br />flood and fill in 139.6 years. This estimate assumed no seepage or outflow and the "worst case" <br />maximum steady inflow assumed for the F Seam mine of 184 gpm (from Table 62) and the <br />median of the 5-yeaz and life-of--mine "worst case" maximum steady inflows (assumed 30 and <br />105 gpm, respectively) from the B Seam mine. Prior to encountering the fault inflows in 1996, <br />WWE reviewed these calculations and determined that they were too conservative citing a more <br />realistic sustained inflow rate of 7 gpm to both the F and B Seams. Review of data presented in <br />Figure 23 shows the average groundwater inflow during the period 1983 to 1995 is about 8 <br />AF/yr or approximately 5 gpm continuously. Using the average 7 gpm groundwater inflow <br />?.OS-257 Revised Jarse 1005 PRIG; Rev. March 1006; Rev. May 2006 PRIO <br />
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