2008-03-21_PERMIT FILE - C1980007A (5)

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West Elk Mine • 8.4 to 11.2 feet, are projected in this area. Maximum changes in slope (tilt), ranging from 1.3 to 6.4 percent, are also projected for this area. The maximum horizontal tensile and compressive strain is projected to range from 0.7 to 4.2 percent. Subsidence depressions and slope changes will be less above the gate road pillars than above solid coal barriers, because they are projected to yield during mining by as much as 4 feet (Table 2 of Exhibit 60B and 60E). No subsidence depressions or changes in stream gradient were observed in Deep Creek, located about 1,050 feet above mined longwall panel 17 during the annual traverse in July 2004. There was no observable change in stream gradient or in stream flow. The depression and change in gradient were apparently sufficiently gradual, so as to not be perceived by the author during the traverse along the trail by the stream. The stream area near the confluence of Dry Fork and Deer Creek, within the area of influence of the west edge of longwall panels E2 and E3, will be monitored prior to, during, and after mining. This is the area where the overburden thickness is at a minimum for the South of Divide mining area (375 to 400 feet) and subsidence effects (subsidence, tilt, and strain) are expected to be at a maximum. Survey monuments will be installed-roughly parallel to the long axes of longwall panels E2 and E3-along Dry Fork, near the Dry Fork road, where measurements can be efficiently made every two weeks when the longwall face is within the angle of draw. In order to obtain detailed data on subsidence parameters in this stream valley environment, the monuments will be placed on 40- to 50-foot centers-roughly equal to one-tenth of the overburden thickness. The twice per month measurements will document subsidence amount, • tilt, and horizontal strain, which will then be compared with predicted values in Table 2 of Exhibit 60B and 60E. The monitoring will begin approximately 1 month prior to the angle of draw of the advancing long,,vall face intercepting the stream chamlel. Surveying of each monument will continue for at least t%vo months after the longwall has passed beneath the monument. The monuments will then be surveyed on a quarterly basis when accessible. The monitoring of the monuments will cease after two consecutive quarterly measurements show no significant movement. The flow in Dry Fork will be monitored twice per month upstream, downstream, and within this area of maximum mining effects in panels E2 and E3, in order to document any flow changes and also compare the results of field measurements with Mr. Dunrud's projections. These measurements will be obtained using non-permanent, non-destructive devices such as flow meters or portable flumes or weirs. One flow monitoring location will be established upstream of the angle of draw of the panel being mined (E2 or E3), one or two within the area of the panel, and another downstream of the panel outside the angle of draw. The twice per month flow monitoring will begin one month before the longwall advances to a point where the stream channel would be within the angle of draw of subsidence and continue for one month after the panel has advanced beyond the area where the stream is within the angle of draw, assuming road and climatic conditions allow such monitoring. After the month is complete, monitoring will occur once every quarter for one year after mining of the longwall panel (E2 or E3) is complete. The thalweg of the Dry Fork will be surveyed over panels E2 and E3 beginning at a point downstrea u:®,f the angle of draw of panel E2 and continue upstream to a point above the angle of • draw of panel E3. This survey will completed before subsidence mining commences in the SOD and then remeasured upon completion of mining panel E2 and then again at the completion of 2.05-153 Revised June 2005 PRIO, Rev. Alarch 2006: May 2006 PRIO, Nov. 2006TR107,Apri12007TR108; Sep. 2007 PR12; Feb. 2008 PR-12