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R <br />The total area selected for the mound, including that under the dikes, shall be roughened in order <br />to thoroughly break up any existing sod layers and to provide a suitable transition zone between <br />the original soil and sand layer of the mound. The area shall be roughened only when the <br />moisture content of the soil 8 inches below the surface is drier than the plastic limit. <br />Surface preparation or roughening may be performed with a mold board plow, a disk plow, or <br />a back hoe using only the teeth. Mold board plow furrows shall be at least 8 inches deep, shall <br />be thrown up slope and shall run perpendicular to the slope. There shall be no dead furrow <br />under the mound. <br />Disking may be used for surface preparation as a substitute for mold board plowing in soils <br />having percolation rates faster than 15 minutes per inch (sandy loam) in the top 8—inch depth. <br />Back hoe teeth may be used to roughen the soil surface and break up the sod layer. Cai,. .,,ust <br />be taken so as not to compact or puddle deeper soil layers. In no case shall any surface soil be <br />excavated and removed from the area. <br />Mound Construction shall proceed immediately after surface preparation is completed. Every <br />effort should be taken to prevent rain from falling on the prepared soil surface. <br />CONSTRUCTION MATERIALS AND PROCEDURES; DISTRIBUTION OF EFFLUENT: <br />A minimum of 12" of soil defined as sand shall be placed where the filter material is to be <br />located. A crawler tractor with a blade or bucket shall be used to move the sand into place. At <br />least 6 inches of sand shall be kept under the tracks to minimize compacting of the plowed layer. <br />The sand layer upon which the filter material is placed shall be level. <br />Sand is defined as a soil texture -omposed by weight of a least <br />25 percent of very coarse, and nr Jium sand varying in size from 2.0 to 0.25 mm, less than 50 <br />percent of fine or very fine sand ran-;ng in size between 0.25 and 0.05 mm, and no more that <br />10 percent of particles smaller that f..j5 mm. <br />A minimum depth of 9 inche if filter material (rock) shall be placed on the sand layer prior to <br />installing the distribution pipe. <br />Filter material is defined as clean rock, crushed igneous rock or similar insoluble, durable and <br />decay —resistant material free from dust, sand, silt or clay. Tbc size shall range from 3/4 inch <br />diameter to 2 1/2 inch diameter. <br />PAGE 3 <br />