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Mr. Jame:: Alt <br />May 19, 1988 <br />Page 2 <br />The measured percolation rates are consistent with the texture of <br />the soil materials in which the percolation tests were run. <br />Septic system drainfields require at least three (3.0) feet eleva- <br />tion difference between the bottom of the filter rock and ground <br />water or indication of periodic soil satura':ion such as soil mott- <br />ling to perform properly. To meet this requirement, a mound septic <br />system is recommended for soil conditions on this lot. <br />The mound is designed to serve a four bedroom house with a whirl- <br />pool bath. Design sewage flow is 600 gallons per day for the <br />house. A sewage flow of 75 gallons per day is added for the <br />whirlpool bath. Total design -ewage flow is 675 square feet. With <br />a design infiltration rate of 1.2 gallons effluent per square foot <br />per day, the required rock bed area of the mound is 562.5 square <br />feet. <br />675 gal/day - 1.2 gal/ft 2/day - 562.5 ft <br />A rock bed 10.0 feet wide by 56.0 feet long provides the needed <br />area. A minimum of one (1.01) foot of medium sand should be con- <br />structed below the rock bed of the mound. <br />The pressure distribution system of the mound consists of Schedule <br />40 PVC plastic pipe. The supply pipe should slope back towards the <br />Pumping chamber so that it drains after the mourd is dosed. The <br />laterals are 1.5 inch inside diameter pipes. The laterals should <br />have 1/4 inch diameter holes drilled at a spacing of 7.0 feet. The <br />laterals should be assembled to the manifold so that the holes <br />point downwards into the rock bed. The C stal ends of the laterals <br />should be drilled horizontally in the end cap near the crown of the <br />pipe to facilitate air venting. <br />A submersible effluent pump capable of delivering at least 42 <br />gallons per minute against a total dynamic head of at least 22.7 <br />feet should be selected. Headlosses are calculated as follows: <br />1. Vertical headloss of 12.2 feet between pump di.:harge (approx. <br />elev. 87.0) and manifold (approx. elev. 99.2) <br />2. Friction loss of 4.1 feet in 14C feet of supply pipe (2.9 feet <br />per 100 feet 2.0 inch inch I.D. plastic pipe at 42 gpm flow), <br />3. Friction loss of 1.0 feet in piee fittings equal to 25 percent <br />of friction loss in supply pipe. <br />4. Five feet (5.01) to account for losses in distribution network. <br />L <br />J <br />