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Mountain Coat Company -West EIk Mine <br />SyMester Gulch Road Geotechnical Irnestigation <br />Seismic Refraction Survey <br />Summary of Operations <br />17+00 <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 2). 'ihe velocity of the first layer is typical of <br />unconsolidated sediments. '111e velocity of the second layer is characteristic of highly weathered bedrock. <br />S ester Gulch Seismic Line 17+00 <br />7120 <br />7110 ~ --.. ........ _. .. .._.__.. ..____..... ..... .-. _ _. ........ ~~ .. <br /> Gt7 <br />7100 .. ...--- ....... ..... .. ... .---.. _.. _ ___. _.Qa _..__- <br />27090 ~. ~ ~. a- m ~ .. - --- --_ .... _~... .. . <br />e <br />9 7080 m os <br />..__ . ... ..... .. . ..~.~_ ._ - -- ... ... .. ~ ere. .. __..-.... __._ .. <br />v 7070 <br />_. p6 .. _.. _'__ - <br />_ .. _ p0 oa _... <br /> 0>2 00 ~ ~ <br />7060 `Ornud Surface .. - ... ... .. _ ..... <br />.. <br /> - <br />W = 112$ R/a <br />~lioundaryl <br />7050 _. .... _ - -... _ _-. .._ .- - _. Y2-5&SOttls .. <br />7040 <br /> <br />o +o zo 3o w so so 70 90 90 f00 110 120 +3D t40 150 +80 170 180 190 Z00 210 220 230 240 250 Z60 270 280 290 <br />oKwK. tn) <br />Frgure Z. Seismic refraction profile at 17+00. <br />• <br />Correlating borehole data to the seismic refraction survey, higher velocities of the second layer can be <br />imerpreted as probably highly weathered sandstone lransitioning with elevation i~o a shale or claystone <br />bedrock (Figure 3). T71is is supported by the scatter observed in the emergent seismic rays, which likely <br />indicates some refracted energy was caused at lateral interfaces between the shaleJclaystoneernd <br />sandstone bedrock horizons. Simply stated, the combined data indicates the right and left sloping flanks <br />are probably sandstone bedrock, while the center of the pro51e is probably a claystone or shale bedrock. <br />Figure 3. Correta6on between seismic refraction profile and borehole logging at Station ]7+00. Green line <br />indicates surface. Red line indicates the acoustic impedance boundary. <br />17+00 <br />O <br />_` ~- <br />CLAY (CL) <br />8rown, same sOrttlslone medium sized ara.:el, <br />plastic. stiff, moist. - <br />c!'_iY CLAY (CL) <br />Brown, some sandstone fragments, very stiff, plastic, <br />refusal of 11 feet due to sanEstone cobbles. <br />- SANDSTONE COBELES Possibly t~ATHERED SANDSTONE <br />Light brown, fine grained, weathered, cobble sized. <br />moist, Hoot. , <br />• <br />grown, <br />UMS, inc. <br />_a <br />iERED CLAYSTONE <br />re fragments and subanqular <br />stlc, most. <br />Page 3 <br />05/17/03 <br />