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CONSTRUCTION MATERIALS AND PROCEDURES <br /> A minimum of 12" of soil defined as sand shall be placed <br /> where the filter material is to be located. A crawler tractor <br /> with a blade or bucket shall be used to move the sand into <br /> place. At least 6 inches of sand shall be kept under the <br /> tracks to minimize compacting of the plowed layer. The sand <br /> layer upon which the filter material is placed shall be <br /> level. <br /> Sand is defined as a soil texture composed by weight of <br /> at least 25 percent of very coarse and medium sand varying in <br /> size from 2 . 0 to 0.25mm, less than 50 percent of fine or very <br /> fine sand ranging in size between 0.25 and 0. 05 mm and no <br /> more than 10 percent of particles smaller than 0 . 05mm. <br /> A minimum depth of 9 inches of filter material (rock) <br /> shall be placed on the sand layer under the distribution <br /> pipe. <br /> Filter material is defined as clean rock, crushed <br /> igneous rock or similar insoluble, durable and decay <br /> resistant material free from dust, san: , silt, or clay. The <br /> size shall range from 3/4 inch diameteJ to 2 1/2 inch <br /> diameter. <br /> PRESSURE DISTRIBUTION <br /> Effluent shall be distributed over the filter material <br /> by three 1 .5 inch diameter perforated pipes under pressure <br /> 53 ' long. Perforation holes shall be 1/4 inch diameter <br /> drilled in a straight line along the length of the pipe . Hole <br /> spacing shall be 36 inches with 19 perforation per lateral . <br /> Holes shall be drilled straight into the pipe and not at an <br /> angle. A sharp drill shall be used and any burrs inside the <br /> pipe shall be removed. The perforated pipe laterals shall be <br /> installed with the perforations downward. <br /> The perforated pipe laterals shall have their ends <br /> capped and shall then be connected in the center to a 2 inch <br /> diameter manifold. The laterals shall 3e spaced 40 inches on <br /> center and at 20 inches from the edge of the filter material . <br /> The manifold pipe shall be connected to the supply pipe <br /> from the pump. The manifold pipe shall be sloped downward to <br /> drain or buried deep to prevent freezing. <br /> Geo-Textile material shall be placed over the filter <br /> material . Sandy loam soil shall be placed on the filter <br /> material to a depth of 12 inches in the center of the mound. <br /> and to a depth of 6 inches at the sides . <br /> Six inches of topsoil shall be placed on the fill <br /> material over the entire area of the mound. A grass cover <br /> shall be established over the entire area of the mound. No <br /> shrubs shall be planted on top of the mound. Shrubs may he <br />