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Exh~b~t 60C <br />Subsidence Evaluation and 2004 Geoiog~c Hazard Field Observations <br />West Ftatrton Lease Area <br />• <br />Ffgure 5. Westward vievr of (he clilfs and ledges of the Ohio Creek Member of the Mesaverde Formation <br />showing a rockfall and landslide area located m the soulhweslern pan of the West Flatiron Lease area <br />• Fiom LocaLOn 3. A small landslide is located in the lower center of the image. <br />' The natural rockfall process involves Failure along joints near the edge of the cliffs, which <br />tend to open up in response to the lateral compimem of gravity-induced stress. The rocks <br />then topple. Fall, and roll down slope. <br />:1 rockfall and landslide arcs is located on the eastern side of West Flatiron above the <br />southeastern part of tin-mined longwall panel 21 (Figure 5). The fall and slide area is located <br />within a few hundred feet west of the west boundary of the Nest Flatiron Lease area (in the <br />Box Canyon nuning area), but is ..-ithin the area of mining influence of the Icase. <br />In summary, the natural rockfall potential to date has been observed to increase only very <br />sliahth or not tit ;dl in :n~eus where the natural rockfall potential is high, however the ax;kfall <br />putrnlial was acccler;tted noticeably above longwall panel ?2 where the estimated natural <br />rc>Lk6t11 potential is very htgh. <br />• <br />631=J32.G50 Wnght Water Engineers, Inc Page 22 <br />Novamber2004 <br />