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<br /> <br />40 <br />must include the width under the drain field rock layer <br />plus a portion of the width of the down slope bank. <br /> <br /> f. Mounds may be located on natural slopes exceeding <br />12 percent if the absorption area is designed to be at <br />least 25 percent larger than the required in Table VI. <br /> <br /> g. The bottom area of the drain field rock layer must be <br />sized on the basis of 0.823 square ft/gallon of waste <br />per day. <br /> <br /> h. The width of the drain filed rock layer in a single bed <br />must not exceed 10 feet. <br /> <br /> i. A rubber-tired tractor may be used for plowing or <br />disking, but must not be driven on the absorption area <br />after the surface preparation is completed. A crawler <br />or track-type tractor must be used for mound <br />construction. where the soil percolation rate is slower <br />than 15 minutes per inch. <br /> <br /> j. The discharge pipe from the pump to the mound area <br />must be installed before soil surface preparation. The <br />trench must be carefully backfilled and compacted to <br />prevent seepage of effluent. <br /> <br /> k. All vegetation in excess of 4 inches in length and dead <br />organic debris must be removed from the surface of <br />the total area selected for the mound, including the <br />area under the banks. The total area must be <br />roughened by plowing to a depth of at least 8 inches or <br />the sod layer broken and roughened by backhoe teeth. <br />Furrows must be thrown uphill and there must be no <br />dead furrow under the mound. <br /> <br />The soil must be plowed or roughened when the <br />moisture content of a fragment 8 inches below the <br />surface is below the plastic limit. The soil under a <br />mound including the area under the banks must not be <br />roughened by rototilling or pulverizing. In soils having