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OxBow Coal Mine Seismic Refraction Survey <br />Geotechnical Investigation Summary of Operations <br />Survey 1, Spread 2-5 <br />Average apparent depth to bedrock along the spread is 26'. From 160' to 240' along the spread apparent <br />depth to bedrock becomes shallow (0.4' - 4.0'). Along the north end of [he spread apparent depth [o <br />bedrock extends to 75'. There are two distinct velocity horizons within the overburden. The firs[ layer <br />extends across the entire length of the spread. Average velocity of the first layer in the overburden is 1475 <br />ft/s. A second layer of overburden with an average velocity of 2925 ft/s is present from 480'to 960'. <br />Average velocity of the bedrock is 7350 ft/s (Figure 8). <br />OxBow Seismic Survey 1, Spread 2-5 <br />631x1 I <br />S N <br />'t Loose Colluvium: Avg. Vel. - 1475 ft/s sae,es <br />6200 - ' ~ Tight Colluvium: Avg. Vel. -2925 tVs' <br />',~ Bedrock: Avg. Vel.-7350 Ws -_i I <br />sw..a. <br />°- 6100 I . <br />~ sp..,a ~ <br />_a I <br />ul sp...a z <br />r" <br />6000 <br />5900 - <br />0 100 200 300 400 500 600 700 800 900 1000 <br />Distance (ft) (no vertical exaggeration) <br />` Fig. 8. Interpreted profile along Survey 1, Spread 2-5. <br />Velocity of the bedrock is indicative of sandstone or shale. Horizons between sandstone and shale are not <br />interpreted because velocities of sandstone and shale are essentially the same. Velocities for the <br />overburden layers are typical for unconsolidated sediments, which can be associated with [he Colluvium <br />in the area. Slightly higher velocities in the second layer of overburden, which appears to pinch out near <br />400', does not provide enough information to accurately characterize a geologic difference between the <br />two overburden layers. <br /> <br />UMS, Inc. Page 5 p7/f)y/03 <br />