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be carefully backfilled and compacted to prevent seepage of <br />effluent. <br />11. Soil surface preparation. <br />a. The total area selected for the mound, including the <br />dikes, shall be plowed to a depth of at least eight (8) <br />inches. Furrows shall run perpendicular to the <br />direction of slopes. All furrows shall be thrown uphill <br />and there shall be no deadfurrow under the mound. The <br />soil shall be plowed only when the moisture content of a <br />fragment eight (8) inches below the surface is below the <br />plastic limit. <br />b. In soils having percolation rates faster than <br />fifteen (15) minutes per inch (sandy loams) in the top <br />preparation as a substitute for plowing. <br />eight (8) inch depth, disking may be used for surface <br />1 <br />c. Mound construction shall proceed immediately after <br />L .:I <br />surface preparation is completed. <br />12. A minimum of twelve (12) inches of soil defined as sand ' <br />shall be placed where the filter material is to be located. A <br />crawler tractor with a blade shall be used to move the sand into ' <br />place. At least six (6) inches of sand shall be kept under the <br />tracks to minimize compaction of the plowed layer. The sand LE <br />layer upon which the filter material is placed shall be level. <br />13. A depth of at least nine (9) inches of filter material <br />shall be placed over the bed area below the distribution pipe. <br />71 <br />be either by four (4) inch distribution pipes with gravity flow <br />diameter perforated pipe under pressure from a manifold. <br />from a distribution box or by one and one-fourth (1-1/4) inch L E :11: <br />14. Distribution of effluent over the filter material shall <br />EI <br />i <br />7 <br />-.c II <br />15. Gravity distribution. <br />a. The four (4) inch distribution pipes shall be rigid <br />plastic with holes at least one -half (1/2) inch diameter <br />spaced no further than thirty -six (36) inches. One (1) <br />row of holes shall be laid at the bottom of the pipe. <br />b. The distribution pipe shall slope downward two (2) <br />inches per one hundred (100) feet away from the <br />distribution box. <br />c. The far ends of the distribution pipe shall be <br />connected. <br />d. The distribution pipes shall be spaced no further <br />than five (5) feet apart and no further than thirty (30) <br />inches from the edge of the filter material. <br />L <br />