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Mountain Coal Company-West Elk Mine Seismic Refraction Survey <br />Sylvester Gulch Road Geotechnical Investigation Summary of Operations <br />Seismic refraction results reveal a second layer of higher velocity material which occurs nearly parallel to <br />the surface at an average depth of 18 feet (Figure 21). The velocity of the Srst layer is typical of <br />unconsolidated sediments. Fanergent rays and corresponding velocities for the second layer indicate <br />sound bedrock <br /> 6yrezEer 09d~hbeBmk ills 4000 <br />7300 <br />~ NE <br /> ~ <br />7297 - blY .~ _. _... . ...__ __ ..__-_...___ _... __. .... .... _ ...... <br />~ <br />~ <br />r1~ ~ <br />_..._ __._ __ _____. ____. ... _. <br /> °' <br />c 7zro _.. _._...__.... .~..~ _. .. ._ . _. 00.. <br />. V1.=f425tt/s ....__ . <br /> a <br />~ .. ~ _ ... _. .._ <br />~..__ '-~ _._ _.___...... _.. ...__..... .__ <br /> <br />a)rlso ~ Y <br />_ ~. __ .. .... __ _~_... ..~ ... .. .. .._.__ . <br /> 00 YO VI = 6~ ftl8 <br />- <br />n4o _...... <br />.. .. .. .. __ __. __. - - ------ ... _._._. ..__.._ <br />rpp ~--oowa sMace ... _ .. <br />-tu <br />m <br />t <br />>~ m <br />y <br /> <br />-fio -40 -so -20 -to o m m 9o a so eo 7o m w tau no ten tso too t6o teo tro tfio t9o zoo <br />Oisaia (iq <br />Fig7ve 20. Sefsmic refrociion profile at 39+D0. <br />Figure 21. Seismic refraction proJSle at 40+Op, <br />41+25 <br />Seismic refraction results reveal a second layer of higher velocity material approavmately 15 fee[ deep on <br />• the southwest slope and 35 feet deep on the northeast slope (Figure 22). The velocity of the Erst layer is <br />typical of unconsolidated sediments. Velocities for the second layer indicate consolidated sediments or <br />highly weathered bedrock <br />Syylvester Gulch Seisnc Line 41+25 <br />7330 <br /> ., <br />73zo __ . __ - . <br /> ox <br />7310 _a@. .. .. .. _.. - _. _ ... _. ~pz~NE. _... <br /> <br />7300 Y~ Y~ <br />_. Y5 .. ._..... Y2t .. _ <br /> ~ Om <br />7290 <br />. o' <br />u>a <br /> p7 <br />X 09 <br />7260 py_ _ <br />O p14 <br />7270 <br />_ ... ... <br />" °s <br /> 04 OM <br /> N <br />7269 - .... _.... yn. .. <br /> 04 a Vt =1700 ft/s <br />72$0 _ _ .. .... <br />7240 ...., <br /> VZ = 4900 Ttls <br /> --Ground Surface <br />7230 <br /> °Boundary 1 <br />7zzo <br />-z o -10 0 10 20 30 4o w w 7o eo 90 10o tto t2o 13o too 1so t6o no tfio tm zoo zt o <br /> tm <br />. Figure 22. Seismic refraction profile at 41 +25. <br />UMS, Inc. <br />Page IS <br />05/17/03 <br />