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2018-09-04_PERMIT FILE - C1980007A (40)
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2018-09-04_PERMIT FILE - C1980007A (40)
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Last modified
2/23/2021 11:13:42 AM
Creation date
12/14/2018 9:26:17 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1980007A
IBM Index Class Name
Permit File
Doc Date
9/4/2018
Doc Name
pg 2.05-101 to 2.05-199
Section_Exhibit Name
2.05.5 & 2.05.6 Post-Mining Land Uses and Mitigation of Surface Coal Mining Operation Impacts
Media Type
D
Archive
Yes
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West Elk Mine <br />The maximum subsidence amount, slope change (tilt), and strain are projected to occur above <br />solid coal barriers and mined longwall panel boundaries, such as above the west ends of longwall <br />panels E2 and E3 where the shallowest overburden occurs. Depressions, ranging in depth from <br />8.4 to 11.2 feet, are projected in this area. Maximum changes in slope (tilt), ranging from 1.3 to <br />6.4 percent, are also projected for this area. The maximum horizontal tensile and compressive <br />strain is projected to range from 0.7 to 4.2 percent. Subsidence depressions and slope changes <br />will be less above the gate road pillars than above solid coal barriers, because they are projected <br />to yield during mining by as much as 4 feet (Table 2 of Exhibit 60B and 60E). <br />No subsidence depressions or changes in stream gradient were observed in Deep Creek, located <br />about 1,050 feet above mined longwall panel 17 during the annual traverse in July 2004. There <br />was no observable change in stream gradient or in stream flow. The depression and change in <br />gradient were apparently sufficiently gradual, so as to not be perceived by the author during the <br />traverse along the trail by the stream. <br />The stream area near the confluence of Dry Fork and Deer Creek, within the area of influence of the <br />west edge of longwall panels E2 and E3, will be monitored prior to, during, and after mining. This <br />is the area where the overburden thickness is at a minimum for the South of Divide mining area <br />(375 to 400 feet) and subsidence effects (subsidence, tilt, and strain) are expected to be at a <br />maximum. Survey monuments will be installed—roughly parallel to the long axes of longwall <br />panels E2 and E3—along Dry Fork, near the Dry Fork road, where measurements can be efficiently <br />made about every two weeks when the longwall face is within the angle of draw. <br />In order to obtain detailed data on subsidence parameters in this stream valley environment, the <br />monuments will be placed equal to one-fifth (20%) of the overburden thickness per accepted <br />engineering practice. The survey measurements will document subsidence amount, tilt, and <br />horizontal strain, which will then be compared with predicted values in Table 2 of Exhibit 60B <br />and 60E. Monitoring will begin approximately one (1) month prior to the angle of draw of the <br />advancing longwall face intercepting the stream channel, assuming climatic and ground <br />conditions allow reasonable and safe access for such monitoring. Should it appear that <br />monitoring sites cannot be reasonably or safely accessed one month prior, then the survey will be <br />conducted at least one time prior to the angle of draw intercepting the stream channel and <br />monitoring will resume when climatic and ground conditions allow safe and reasonable access. <br />Surveying of each monument will continue for at least two months after the longwall has passed <br />beneath the monument. The monuments will then be surveyed on a quarterly basis when <br />accessible. The monitoring of the monuments will cease after two consecutive quarterly <br />measurements show no significant movement. <br />The flow in Dry Fork will be monitored twice per month upstream, downstream, and within the area of <br />maximum mining effects in panels E2 and E3, in order to document any flow changes and also compare <br />the results of field measurements with Mr. Dunrud's projections. These measurements will be obtained <br />using non -permanent, non-destructive devices such as flow meters or portable flumes or weirs. One flow <br />monitoring location will be established upstream of the angle of draw of the panel being mined (E2 or <br />E3), one or two within the area of the panel, and another downstream of the panel outside the angle of <br />draw. The twice per month flow monitoring will begin one month before the longwall advances to a <br />point where the stream channel would be within the angle of draw of subsidence and continue for one <br />month after the panel has advanced beyond the area where the stream is within the angle of draw, <br />assuming climatic and ground conditions allow reasonable and safe access for such monitoring. After the <br />2.05-153 Rev. 06/05- PRIO, 03/06- PRIO, 05/06- PRIO, II/060- TRI07, 04/07- TRI08, 09/07- PR12, 02/08- PR12; 10/10- MR372 <br />
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