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Mountain Coal Company-West Elk Mine <br />Sylvester Gulch Road Geotechnical Investigation <br />Seismic Refraction Survey <br />Summary of Operations <br />49+25 <br />Seismic refraction results reveal a second layer of higher velocity material which occurs Heady parallel to <br />the surface at as average depth of 20 fi~ (Figure 30). The velocity of the first layer is typical of <br />unconsolidated sediments. Velocities for the second layer indicate consolidated sedime~s or highly <br />weathered bedrock <br />• <br />• <br />w = tats tus <br />ram ~-oa,•asat•a. _- - ..... _. __-- ~----- ~-- -.... - - ~t=~ootus~ <br />~epY1EdY t <br />ram, , <br />-m -to o to m ao eo w w m m so too tto tm too teo tso too rro tm tso zoo zto am zoo zeo <br />~~ (R> <br />Figwe 30. Seismic refraction profile at 49+15. <br />Data from the borehole at 49+25 indicate sandstone bedrock at a depth of 26 ft (Figure 31). Velocities <br />from the seismic refraction are too slow for sandstone bedrock. Amore likely interpretation for the <br />profile would be a second layer represe~s the bedrock horizon as it varies between weathered sandstone <br />and sandy shale. <br />Figure 3I. Correlation between seismic refraction profile and borehole logging. Green line indicates surface. Red <br />line indicates the acoustic impedance boundary. <br />49+25 <br /> <br /> ~ 9r^X the .aea ene aa~eetane medq n.e~nt <br />z <br /> gte~ree~m, ~netst eood fmm 0 to 65 foci, Ci~t1Y plmtiL e'QY <br /> e <br /> e <br /> <br /> Dak eery oox matrt fo wet (P~hed ealc Gam a6emm). <br /> t« `T~Ymwattsmnr. a <br />y <br /> t <br />1 <br /> ID <br /> Irey mm• the aana the mMatma fry pvstlc, e'trY <br /> txr, n,ert <br /> a <br /> <br /> <br /> Y <br /> ~-Pt^~'~ °PB~Y M ~.'~•, same tloy antl Tna b nedWm 9roeel sv <br />~at <br />mtlsi. <br /> W ~(~ g <br />pp~~ <br />nlt Ereenno0,~neoNL a <br /> to 2afued d 30 feet <br /> ae <br /> <br />7 5 100 <br />UMS, Inc. Page 20 05/17/03 <br />