1978-09-14 Septic System Design Report

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1 �r • 40 D. There shall be a layer of 12 inches of filter material in the bottom of the trenches and beds placed as shown in Figure 3. E. Distribution pipe used in trenches or beds for gravity flow distribution shall be at least four inches in diameter and constructed of sound and durable material not subject to corrosion or decay or to loss of strength under continuously wet conditions. The ends of each lateral shall be capped. (1) Agricultural drain tile shall be in 12-inch lengths and laid with I./4-inch open joints on grade boards. Ali open joints shall be protected on top by strips of asphalt -treated building paper at least ten inch.:s long and three to six inches wide or by other acceptable means. (2) Perforated plastic pipe shall be laid with one row of - r- forations on the bottom. Perforations shall be at least 1/2-inch in diameter and spaced no farther than 12 inches aF:Art. (3) Other devices may be used to distribute sewage tank effluent over the soil ,'eatme.t area upon approval of the local ad- ministrator of the sanitary ordinance. (4) The distribution pipes shall be laid 19vel or on a uniform slope away from the sewage tank of no more than four inches pe. 100 feet. F. The filter material shall be coverfld with untreated building paper or a two-inch layer of hay or straw or similar, ap- proved permeable materials. G. The trenches or beds shall be backfilled with the excavated material and slightly crowned above finished grade to allow for settling. The backfill shall not be compacted to a density greater than that of the original soil. H. The minimum depth of cover over the distribution pipes shall be at least eight inches. I. The maximum depth of cover over the distribution pipes shall be no more than 36 inches and preferably 24 inches. J. A grass cover shall be catablished over th_- soil treatment area. K. See Figure 3 for further detail. - 10 -