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Mountain Coal Company-West Elk Mine <br />Sylvester Gulch Road Geotechnical Investigation <br />19+00 <br />Seismic refraction results reveal a second layer of higher velocity material which occurs Heady parallel to <br />the surface at an average depth of 10 feet (Figure 4). 'Ihe velocity of the fast layer is typical of <br />unconsolidated sediments. A reasonable assumption about the geologic character of the second layer is <br />that of a moderately consolidated sandstone cobble layer or highly weathered bedrock. <br /> S ester Gulch Seismic line 18+00 <br />rr3o <br />7120 _ _.. ... __. .. ._ __..... __.. __...__._.. .... __ ~_,._. __..._ ~~.. <br /> <br />7770 - .. ~ .. ....... .... .._..... _. .. _.. __. ... .. ... ._.... _. ..__ V1=975 s <br />C_ <br />7100 ~ <br />_ ....._ ._ __. _.. _.... _ _. <br />7D90 g8 <br />~ 8r <br /> <br />ev <br />V2 = 4500 815 <br />~c~ <br /> oo <br />. <br />.. _~_ys .... _ <br />- _ <br /> ~ <br />~ <br />-e-Gmund S~uFace <br />7070 ~Boundaryt .___. __.._ .... .__.. _.__ .:. ...... <br />7060 <br /> 0 10 20 30 40 50 BO 70 a] 90 100110 120 730 740 750 160 170 76D 790 200 270 220 230 240 260 260 270 28 0 <br /> Iislanea (Iry <br />Frgare 4. Seismic refraction profrle at 19+00. <br />By correlating borehole data with the results of the seismic refraction survey, higher velocities of the <br />second layer can be irnerpreted as a consolidated sandstone cobble layer or highly weathered sandstone <br />. bedrock (Figure 5). <br />Figure 5. Correlation between seismic refraction p%file and borehole logging at Stotion 19+00. Green line <br />indicates surface. Red line indicates the acoustic impedance boundary. <br />19+00 <br /> <br /> ~ _ - <br />srtx Mx <br />:W <br />~ <br />Bro.... !.l.l~. ~~:~ ~!~ - <br />ca~..t sn~>r we. Hen ~ ~w o t.wt. <br /> <br /> <br />fi . <br /> <br />r: ere.n wwm! sa,ate.a o-o !.t .nx ,...est. <br />., <br />B~nOSTWE COBBLES <br />wwarm, r . yre.d ~l.tme. <br />' <br />1 ~+ ~~ n <br /> <br />$1TY 4.x (Cl) P CLAxSxOBE m <br />grown Rmw <aa.a .un, gcae, mast. a <br />n!t!: cax a.ms. m eak w!r ~e rs.w lrer !r zv3 r»r :. <br />an tt.Y (Cu Peawblr wEwtHEBE'D f1EYH~1E m <br />BW! 9rawn. Vlcw fn! sent, pIaMY. ~Y stirs, malt. <br /> H <br />a <br /> <br />9tME R <br />c~ey...mn...a ..aa m m>: >. <br />w <br />u <br />Seismic Refraction Survey <br />Summary of Operations <br />UMS, Inc. <br />Page 4 <br />05/17/03 <br />