septic design for 3 br hse - not used

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� rn q �£ C� p i�$ , E-9 CONSTRUCTION EQUIPMENT � ) A rubber-tired tractor may be used for plowing or disking to prepare the soil surface but in no case shall a rubber-tired tractor be used after the surface preparation is completed. A crawler or track-type tractor shall be used for mound construction. SOIL SURFACE PREPARATION The discharge pipe from the pump to the mound area shall be installed prior to soil surface preparation. The trench excavated to install the discharge � • pipe shall be carefully backfilled and compacted to prevent seepage of effluent. � The total area selected for the mound, including that under the dikes, shall ; be roughened in order to thoroughly break up any existing sod layers and to � provide a suitable transition zone between the original soil and the sand layer of the mound. The area shall be roughened only when the moisture content of the soil 8 inches below the surface is drier than the plastic limit. Plastic limit is the soil moisture content below which the soil may be manipu- � lated for purposes of installing a soil treatment system, and above which mani- pulation will cause compaction and puddling. If a fragment of soil can easily be rolled into a wire 1/8 inch in diameter, the moisture content is above the plastic limit. If the soil is dry enough to be friable and falls apart when rolling it into a wire, the moisture content is below the limit, and soil may be manipulated. The standard method of determining'the plastic limit is speci- , � fied in American Association of State Highway Officials (AASHO) Designation: ' T 90-61. ,Surface preparation or roughening may be performed with a mold board plow, a , � disk plow, or a backhoe using only the teeth. Mold board plow furrows shall , be at least 8 inches deep, shall be thrown upslope and shall run perpendicular to the slope. There shall be no dead furrow under the mound. Disking may be used for surface preparation as a substitute for mold board � plowing in soils having percolation rates faster than 15 minutes per inch � (sandy loam) in the top 8-inch depth. ' Backhoe teeth may be used to roughen the soil surface and break up the sod � layer. Care must be taken so as not to compact or puddle deeper soil layers. In no case sha].1 any surface soil be excavated and removed from the area. i � Mound construction shall proceed immediately after surface preparation is com- pleted. Every effort should be taken to prevent rain from falling on the pre- pared soil surface. CONSTRUCTION *1ATERIALS AND PROCEDURES; DISTRIBUTION OF EFFLUENT A minimum of 12" of soil defined as sand shall be placed where the filter material is to be located. A crawler tractor with a blade or bucket shall be used to move the sand into place. At least 6 inches of sand shall be � � kept under the tracks to minimize compaction of the plowed layer. The sand -- layer upon which the filter material is placed shall be level.