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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. Care must <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 /> CONS FRUCTION 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 composed by weight of a least <br /> 25 percent of very coarse, and medium sand varying in size from 2.0 to 0.25 mm, less than 50 <br /> percent of fine or very fine sand ranging in size between 0.25 and 0.05 mm, and no more that <br /> 10 percent of particles smaller that 0.05 mm. <br /> A minimum depth of 9 inches of 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. The size shall range from 3/4 inch <br /> diameter to 2 1/2 inch diameter. <br /> PAGE 3 <br />