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(from a linear regression estimate) show a range of from 25 to 64 percent clay in <br />the five samples. <br />In CR220 the overburden layer (64'-109') is estimated to contain 64Y, clay but is <br />expected to buried since two coal seams lie below it. The overburden layer in <br />CR220 (161'-172') contains an estimated 44% clay and an ESP of 15.6. It is above <br />the lowest coal seam but also adjacent to a layer of sandstone plus sil[stone <br />(133'-161') which contains an estimated 10% clay and an ESP of 5.5. These two <br />layers will likely become mixed during m ining and the mixed layer should produce <br />an acceptable ESP. <br />In CR222 the overburden layer (150'-184') lies between the two lower coal seams. <br />This layer contains an estimated 35% clay and an ESP of 5.3. However, if some <br />mixing occurs with an adjacent layer (124'-145'), with only an estimated 4% clay <br />and an ESP of 3.3 the mixed layer should allow normal plant growth. Assuming a <br />linear arithmetic effect on ESP if the lowermost ~ /feet of overburden is mixed, <br />• [he resulting expected ESP can be calculated as ~'llows: <br />E X1Y1 + X2Y2 <br />~X <br />where: E =expected ESP value of [he mixed materials <br />X =depth of any individual strata to be mixed <br />Y =ESP of any individual strata to be mixed <br />therefore: E _ (16 ft)(3.3 ESP) + (34 ft)(15.3 ESP <br />50 ft. <br />E = 11.5 ESP <br />In CR223 [he overburden layer (96'-111') contains an estimated 40% clay and an <br />ESP of 17.0. The overburden layer (114'-145' except for coal seams) [ha[ lies <br />adjacent contains an estimated 55% clay and an ESP of 17.9. The nearest overbur- <br />den layer with a low ESP (47'-80') is no[ close enough for convenient mixing. <br />2-389 <br />