06-12-1989 Council Packet - Laserfiche WebLink

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Ron Lauer August 2, 1988 Page Two The measured percolation rates are consistent with the texture of the soil materials in which the percolation tests were run. The City of Orono requires at least three feet elevation difference between the bottom of the filter rock of a septic system and ground water or indication of periodic soil saturation such as soil mottling. To meet this requirement, a mound septic system recommended at this site. The mound is designed to serve a four bedroom house. Design -ge flow is 600 gallons per day. With a design infiltration rate of 1.2 gallons effluent per square foot per day for the medium sand fill material of the mound, the required rock bed area of the mound is 500 square feet. 600 gal/day t 1.2 gal/ft^/day * 500 ft^ A rock bed 10.0 feet wide by 50.0 feet long provides the needed area. A minimum of one foot (1.0') of medium sand should be constructed below the rock bed. The pressure distribution syst f the mound consists of Schedule 40 PVC plastic pipe. The suppxj ipe should slope back towards the pumping chamber so that it drains after the mound is dosed. The laterals are 1.5 inch inside diameter pipes. The laterals should have 1/4 inch diameter holes drilled at a spacing of J.O feet. The laterals should be assembled to the manifold so that the holes point downwards into the rock bed. The distal ends of the laterals should be drilled horizontally in the end cap near the crown of the pipe to facilitate air venting. A submersible effluent pump capable of delivering at least 37.5 gallons per minute against a tctal dynamic head of at least 14.1 feet should be selected. Headlosses are calculated as follows: 1. Vertical headless of 8.0 ^eet between pump discharge (approx, elev. 98.0) and manifold (approx, elev. 103.8) 2. Friction loss of 0.9 feet in 40 feet of supply pipe (2.3 feet per 100 feet 2.0 inch inch I.D. plastic pipe at 37.5 gpm flow), 3. Friction loss of 0.2 feet in pipe fittings equal to 25 percent of friction loss in supply pipe, 4. Five feet (5.0') to account for losses in distribution network.