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2010-06-04_PERMIT FILE - C1982056A (10)
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2010-06-04_PERMIT FILE - C1982056A (10)
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Last modified
8/24/2016 4:12:47 PM
Creation date
10/14/2010 10:11:32 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1982056A
IBM Index Class Name
Permit File
Doc Date
6/4/2010
Doc Name
Pages 2.05-123 to 2.05-197.3
Section_Exhibit Name
2.05.5 Postmining Land Uses
Media Type
D
Archive
Yes
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Actual Impacts — Foidel Creek TCC has subsided segments of Foidel Creek over longwall Panels 9 -Right <br />through 6- Right. During the mining of Panel 9- Right, flow in Foidel Creek was interrupted for an approximate <br />• 8 -hour period. The interruption in flow over the panels started on August 26, 1996, and resumed on August 27, <br />1996. Flow over the panel equilibrated by October 24, 1996. The flow data is presented in Table 72. <br />Additionally, the underground mining and subsiding of Foidel Creek over Panels 9 -Right through 7 -Right has <br />resulted in ponded areas along the creek over the panels. The details of the ponding have been transmitted in <br />prior subsidence reports. All reports are from period of 1996 through first half of 1998. As of July 1, 1998, the <br />ponded area over 9 -Right was approximately 0.8 acres, over 8 -Right approximately 0.3 acres, and over 7- Right, <br />two areas of 0.5 acres and 3.1 acres. The upstream and downstream flow measurements do not indicate any <br />measurable decrease in flow resulting from ponding. <br />Predicted Impacts — Middle Creek Middle Creek is a perennial stream with headwaters south of the permit area. <br />This perennial stream flows northeast for approximately 15.6 miles to its confluence with Trout Creek. The <br />potential changes in the Middle Creek gradient due to surface subsidence caused by the longwall mining in <br />panels 2 -Right through 8 -Right were calculated. This calculation is based on the characteristics of Middle <br />Creek and results of the ground surface subsidence study presented in Exhibit 7E of this application. According <br />to SubTerra, Inc. (1996), the maximum calculated slope change would not exceed 19x10 -3 ft/ft. <br />A stream channel profile, Figure 5j, was plotted for Middle Creek as it meanders through the project site. This <br />stream crosses six of the eight longwall panels in a direction almost perpendicular to the panels. The length of <br />the undermined section of this stream is less than 2.0 miles and the average gradient within this section is 0.014 <br />ft/ft. The hydraulic gradient of the Middle Creek stream is steeper at the crossing of panel 7 Right. Within this <br />section, the head - cutting could be more pronounced. The gradient of Middle Creek, in the area near the <br />confluence with Foidel Creek (considered an Alluvial Valley Floor), is much flatter and no substantial head <br />cutting or deposition is anticipated. Therefore, no impacts to the water usage and to the essential hydrologic <br />. function of the AVF are expected. <br />Slopes of the Middle Creek Channel crossing over the Foidel Creek Mine range from 0.0067 ft/ft in the <br />upstream reach to 0.02 ft/ft in the central area, and 0.013 ft/ft in the lower reach. A short reach in the central <br />area falls at 0.046 ft/ft under natural conditions. Figure 5j shows the Middle Creek Profile. <br />1. Middle Creek enters the mining area at Panel 2- Right. The Middle Creek profile at the center of Panel <br />2 -Right may subside up to 46 inches. The low slope will cause the subsidence channel bed -slope to <br />erode upstream as much as two feet deep, tapering off to zero feet at about 300 feet upstream. It is not <br />anticipated that any mitigation will be required. <br />2. A low spot of about 78 inches below the adjacent profile in the subsided area of Panel 4 -Right will be <br />filled by sediments eroded from the unsubsided area between Panels 2 -Right and 4- Right. The net <br />results in this reach will be to erode about two feet in the upstream reach and fill about four feet at the <br />center of Panel 4- Right. The stream gradient will adjust according to flow conditions. It is not <br />anticipated that any mitigation will be required. <br />The subsided stream channel profile between Panel 4 -Right and Panel 7 -Right is estimated to be <br />approximately congruent to the natural profile. The center of Panel 5 -Right may subside as much as 79 <br />inches, however, the low spot will fill about two feet to maintain a congruent profile. Minor erosion and <br />deposition of one to two feet in other areas may occur as the stream adjusts. <br />4. There will be a low spot in the center of Panel 8 -Right of about 74 inches. The stream bed will adjust <br />itself with minor erosion upstream and downstream to achieve a profile similar to natural conditions. <br />If headcutting is greater than three feet, or if incising of two feet or greater occurs more than 400 feet from the <br />point of origin of the headcut, then channel morphology should be evaluated. Channel mitigation measures <br />should be initiated, if warranted, after the evaluation. A visual examination, possibly combined with analytical <br />results, should be considered as an appropriate method for determining "damage." The character of the stream, <br />PR09 -08 2.05 -162 04/29/09 <br />
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