1987-01-12 Site Evaluation Report

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Mr. David Nitz Pag s 2 January 12, 1987 Measured percolation rates are consistent to somewhat rapid for 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 is recommended for the primary and secondary septic systems at this site. The mound is designed to serve a four bedroom house with a whirlpool bath. Design sewage flow for the house is 600 gallons per day. A sewage flow of 100 gallons per day is added for the whirlpool bath. Total design sewage flow is 700 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 700 square feet. 700 gal/day 1.2 gal/ft2/day = 583 ft2 A rock bed 10.0 feet wide by 60.0 feet long provides the needed area. A minimum of one foot (1.01) of medium sand should be constructed below the rock bed. The pressure distribution system of the mound consists of Schec _e 40 PVC plastic pipe. The supply pipe should slope back towards the pumping chamber so that it drains after the mound is dosed. The la::ezals are 1.5 inch inside diamete- r-pes. The laterals should have 1/4 inch diameter holes drilled at a spacing of 3.0 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 norizontally in the end cap near the crown of the pipe to facilitate air venting. A submersible effluent pump capable c•f deliver.Lng at least 45 gallons per minute against a total dynamic head of at least 10.2 feet should be selected. Headlosse- are calculated as follows: 1. Verti.:al headloss of 4.5 feet between pump disc,arge (approx. elev. 95.0) and manifold (approx. elev. 99.5), i�tion �oss of 0.7 feet in 20 feet of supply pipe (3.3 feet per 100 feet 2.0 inch I.D. plastic pipe at 45 gpm flow), 3. Five feet (5.01) to account for losses in distribution network.