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Mountain Coal Company-West EIk Mine Seismic Refradion Survey <br />Sylvester Gulch Road Geotechnical Investigation Summary of Operations <br />• 38+00 <br />Seismic refraction results reveal a second layer of higher velocity material approarimately 12 feet deep on <br />the southwest slope and 18 feet deep on the northeast slope (Figure 19). The velocity of the first layer is <br />typical of unconsolidated sediments. F~tergent rays and corresponding velocities for the second layer <br />indicate sound bedrock <br />• <br />raoo <br />rmo <br />T <br />~al0 <br />C ~~ <br />0 <br />~i 77Aa <br />0 <br />rno <br />. .. .. _... _ _... .._ -_ ._ ..... __.. - .~ XE .-. <br />Qr <br />~ ~ <br />.. __ _..._o'-_ _ ._ .. __...._.._ -._ __.-. -. ~. ___ - .. .. -. ... ._ <br />W ~ <br />pe <br />.. ...... .. .. ...~ ~.Y ~-~%... <br />VL ~ Vt7Vy IU.S <br />o to m ao a so w >o eo ao tao tto tat tso tm tso teo tro tao teo ~o zto <br />Detenx ryq <br />Figure 19. Seismic refrocdon profrle at 38+00. <br />• <br />39+00 <br />Seismic refracuion results reveal a second layer of higher velocity material which occurs nearly parallel to <br />the sur6ce at an average depth of IZ feet (Figure 20). The velocity of the first layer is typical of <br />unconsolidated sedime~s. Velocities for the second layer indicate highly consolidated sediments or <br />highly weathered bedrock <br /> Slyvester Gulch Seismic Line 39+00 <br />>3tu <br /> m <br />73m Pr ... .. _ _.. _- .. .. .. .. XE <br />~ <br /> ~ ~ <br /> <br />„ao °' V1 = 1325 ft/s__... . an. . <br /> m ~ <br /> <br />rno oe ~ <br />_ . _.. <br />C_ <br />m ~ <br />'+~ ___ _ <br /> a p <br />>~ rr o* <br /> <br />yam w ~ <br />- . _ _ . o°...... _ <br /> V2 -4600 ft/s <br />~. <br />,n, _ _ <br />77~ -+-Ground Surface .. ... . <br />.. <br /> ~-Boundary 7 <br />rno <br />-ai .to o ro zr 3o n w m ro eo w tao tto tai tso tw tw tao no tro tao <br />Hawn ltq <br />UMS, Inc. Page 14 05/17/03 <br />