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Fall 2007 Subsidence and Geologic Field Observations <br />Box Canyon, Apache Rocks, and South of Divide Mining Areas <br />addition, a baseline survey was completed to establish the current topographic profile of the Dry <br />Fork of Minnesota Creek (Dry Fork) thalweg (see Section 3.2). <br />3.1 E1 Panel Subsidence Monitoring Grid <br />The West Elk Mine has historically extracted coal mainly from the B-seam of the Mesaverde <br />Formation. Future mining will also include the E-seam (approximately 300 feet above the B- <br />seam), primarily in the SOD mining area. As part of the ongoing data collection and monitoring <br />programs required under its permit, a new E-seam subsidence monitoring grid was proposed, <br />developed and recently constructed. This grid is located over E-seam longwall panel 1 (E1) and <br />is comprised of 119 points in one longitudinal and two transverse monument lines relative to the <br />panel orientation. This is the first panel to be mined in the E-seam. The two transverse traverses <br />extend beyond the gate road of longwall panel E1 both to the north and south. The southern end <br />of these traverses extends to approximately the middle of longwall panel E2 (at least 700 feet <br />outside the edge of the panel). Appendix B provides the point number, northing coordinate, <br />Basting coordinate, and elevation at each of the 119 observation points and conforms to <br />previously established criteria (see Map B-1 in Appendix B). <br />This grid is planned to be resurveyed at least three months, but no more than nine months, after <br />the longwall face has moved past the end of the longitudinal survey line of the El panel to <br />determine the amount of subsidence that has occurred and the subsidence angle of draw. Data <br />obtained from the monitoring of this subsidence grid will be used to calibrate the subsidence <br />prediction model so that a more refined analysis can be made. <br />In addition, monitoring stations are presently being established on Monument Dam and at <br />strategic locations around Minnesota Reservoir. Specific details of these locations will be <br />provided in subsequent reports. <br />3.2 Stream Channel Baseline Data for Dry Fork <br />Subsidence depressions, tilt, and strain are projected to occur in the Dry Fork drainage and its <br />tributaries when longwall panels E2 through E6 are mined in the SOD mining area. Maximum <br />• <br />831-032.780 Wright Water Engineers, Inc. Page 10 <br />November 2007 <br />