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Backhue teeth may oe used to roughen the soil surface and break up the <br />sod layer. Care m..st be taken so as not to compact or puddle deeper soil <br />layers. In no case snc'I any surface soil be excavated and removed from <br />the area. Backhoe teeth shall roughen the surface perpendicular to the <br />slope. <br />D. Mound construction shall proceed immediately after surface preparation is <br />completed. Every effort shall be taken to prevent rain from falling on the <br />prepared soil surface. <br />4. SILL (see Figure for layout and details) <br />A. The bottom area of the filter material (rock) was sized on the basis of <br />0.83 square feet per gallon of waste per day, yielding 500 square feet. <br />B. In no case shall the width of the filter material (rock) in a single bed <br />exceed 10 feet. <br />5. CONSTRUCTION MATERIALS AND PROCEDURES <br />A. A minimum of 12 inches of soil defined as sand shall be placed where the <br />filter material is to be located. A crawler tractor with a blade or bucket <br />shall be used to move the sand 'rte place. At least six inches of sand <br />shall be kept under the tracks to minimize compaction of the plowed layer. <br />The sand layer upon which the filter mateiral is placed shall be level. <br />B. Sand is defined as a soil texture composed by weight of at least 25 percent <br />of very coarse, coarse, and medium sand varying in size from 2.0 to <br />0.25 mm, less than 50 percent of fine or very fine sand ranging in size <br />between 0.25 and 0.05 mm, and no more than 10 percent of particles smaller <br />than 0.05 mm. <br />C. A depth of at least 9 inches of filter material (rock) shall be placed <br />on the sand layer prior to installing the distribution <br />D. Filter material is defined as clean rock, crushed igneous rock, or similar <br />insolubTe, durable, and decay -resistant material free from dust, sand, silt, <br />or clay. The size shall range from 3./4 -inch diameter to 2 1/2 -inch <br />diameter. <br />E. Effluent shall be distributed over the filter material by 1 -inch to <br />1 1/2 -inch diameter perforated pipe under pressure. Perforation holes shall <br />be 3/16 -inch to 1/4 -inch in diameter drilled in a straight line along the <br />length of the pipe. Hole pacing shall be 30 inches to 36 inches. Holes <br />shall be drilled straight into the pipe and not at an angle. A sharp drill <br />shall be used and any burrs in the inside of the pipe shall be removed. <br />The perforated pipe laterals sha.l be installed level with the perforations <br />downward. <br />F. The perforated pipe laterals shall be connected to a 2 -inch diameter <br />manifold pipe and shall have their ends capped. The laterals shall be <br />spaced no further than 40 'inches on center and no further than 20 inches <br />from the edge of the filter material. Laterals shall be no longer than <br />�O feet. <br />G. The manifold pipe shall be connected t0 the supply pipe from the pump. The <br />manifold pipe shall be sloped toward the supply pipe from the pump. <br />-8- <br />