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45.0' maximum stripping depth <br /> 33.5' average overburden <br /> 5.0' Lower Dakota <br /> At the average stripping depth <br /> 33.5' overburden <br /> + 5.0' coal <br /> 38.5' material excavated <br /> at 15% Swell <br /> 1.15 x (33.5) = 38.5 material replaced <br /> 38.51/38.5' = 1.00 of the initial thickness <br /> Therefore, the 0.8 requirement for thin overburden and the 1.2 requirement for thick <br /> overburden are not met. <br /> At the maximum stripping depth <br /> 45.0' overburden <br /> +5.0' coal <br /> 50.0' material excavated <br /> at 15 % Swell <br /> 1.15 x (45.01) = 51.8' material replaced <br /> 51.8/50.0 = 1.04 of the initial thickness <br /> Therefore, the 0.8 requirement for thin overburden and the 1.2 requirement for thick <br /> overburden are not met. <br /> Disposal of Excess Spoil <br /> All excavated non-coal material from the mining areas will be used for backfilling the <br /> mined pits and blending mined areas into the existing topography to achieve the <br /> approximate original landform. Therefore, no excess spoil material will exist. <br /> 20-4 Revised 08/19/88 <br />