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A stream channel profile, Figure 5i, was plotted for Foidel Creek as it meanders through the project site. The <br />stream enters the undermined area a[ the edge of panel 5 Right and then trusses panels 6 Right through 9 Right. <br />The longest section of this stream will be undermined by panel 7 Right. A total of 3.4 miles in length for Foidel <br />Creek was undermined. The average gradient for the undermined section of the stream is 0.005 ft/ft. Based on <br />subsidence calculations presented in Exhibit 7E (SubTerra, 1nc., 1993), the predicted post-mining slope of the <br />Foidel Creek stream channel would not change by more than 12.5x10-3 fUft. The survey work done on Foidel <br />Creek for the mining of panel 9 Right through 6 Right showed no significant changes in the gradient of this creek. <br />The creek profiles are present in TCC's semi-annual subsidence report. The average channel slope, based on the <br />profile presented in Figure Si, is about 0.0049 ft/ft upstream of the rib between Panels 7 Right and 8 Right and <br />0.0073 ft, downstream. Based on the assumption that the system is in approximate equilibrium, the subsided <br />channel will probably adjust itself to about 0.007 tl/ft. <br />As the creek crosses over panel 6 Right, after subsidence, there will be a head-cut as much as three feet deep <br />tapering off to zero feet about 1,000 to 2,000 feet upstream in about the same channel cross-section as exists <br />now. This will occur as alluvial silts and clays from the streambed are eroded and re-deposited in the subsided <br />area in the center of panel 6 Right and the natural streambed gradient is reestablished. No mitigation is <br />anticipated to be required. <br />2. The area of the rib between panels 6 Right and 7 Right, panel 7 Right, and the panel 7/8 rib will all subside <br />fairly uniformly with respect to the streambed profile. Minor cuts and fills of one to two feet maximum may <br />occur due to varying natural conditions in the channel bed and bank materials, subsidence irregularities, and <br />channel flows. The channel will assume the same symmetry, as determined by flow conditions, as it has now. <br />3. A subsidence trough of as much as 42 inches may occur in the center of panel 7 Right. However, the trough <br />will taper out in about 350 feet on each side of the deepest portion. It will fill will alluvial sediments from the <br />• adjacent stable upstream segment in a short period, depending on flow conditions. No significant effects on <br />the stream channel are anticipated and no mitigation is anticipated to be required. <br />4. The channel reach crossing panels 6 Right and 7 Right and the ribs is predicted to subside at a channel slope <br />very close to that of the natural channel, and no significant channel geometry changes are anticipated. <br />5. Panel 8 Right has a change in slope to a flatter slope crossing the rib between panels 8 Right and 9 Right, and <br />to a deeper subsidence trough in panel 9 Right. Channel profile equilibrium will occur as the high spot on the <br />rib erodes about 1 '/z to 2 feet to match pre-existing natural ground slopes. The profile will then erode slightly <br />to match the natural grade downstream of panel 9 Right. No mitigation measures are anticipated. <br />Actual Impacts -Foidel Creek TCC has subsided segments of Foidel Creek over longwall panels 9 Right through <br />6 Right. During the mining of Panel 9 Right, Flow in Foidel Creek was interrupted for an approximate 8 hour <br />period. The interruption in flow over the panels started on August 26, 1996, and resumed on August 27, 1996. <br />Flow over the panel equilibrated by October 24, 1996. The flow data is presented in Table 72. <br />Additionally, the underground and subsiding of Foidel Creek over panels 9 Rightthrough 7 Right has resulted in <br />creating ponded areas along the creek over the panels. The details of the ponding have been transmitted in prior <br />subsidence reports. All reports are from period of 1996 through first half of 1998. As of July 1,1998, the ponded <br />area over 9 Right was approximately 0.8 acres, over 8 Right approximately 0.3 acres, and over 7 Right, two areas <br />of 0.5 acres and 3.1 acres. The upstream and downstream flow measurements do not indicate any decrease in flaw <br />resulting from this ponding. <br /> <br />APPROl/ED FEE G II 2000 <br />TR 94-32 2.05-162 11!15199 <br />