Laserfiche WebLink
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 the spread apparent depth to <br />bedrock extends to 75'. There are two distinct velocity horizons within the overburden. The first layer <br />extends across the entire length of the spread. Average velocity of the first layer in the overburden is 1475 <br />fUs. A second layer of overburden with an average velocity of 2925 ft/s is present from 480'[0 960'. <br />Average velocity of the bedrock is 7350 fVs (Figure 8). <br />OxBow Seismic Survey 1, Spread 2-5 <br />6300 I <br />'!Loose Colluvium: Avg. Vel. - 1475 ft/s <br />SyeaES <br />6200 ~ ~ Tight Colluvium: Avg. Vel. - 2925 fVs <br />~ Bedrock: Avg. Vel. - 7350 tVs t <br />sp~aE I <br />~ 6100 se,.+n n I.• <br />m <br />= I <br />W sp,..a z _ -.. <br />r_. <br />6000 <br />5900 <br />100 200 300 400 500 600 700 800 900 1000 <br />Distance (/1) (no vertical exaggeration) <br />• Frg. 8. /rlterpreted proftle along Survey 1, Spread 2-S. <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 the Colluvium <br />in [he 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 07/(>y/03 <br />