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Mr. Gary McEnemey <br /> August 12,2002 <br /> Page 3 <br /> shown. This is the basic equation for determining the required absorption area based on estimated flow. <br /> The equation includes the sewage application factor. The sewage loading.equation and assumptions are <br /> presented next: <br /> Sewage Loading Equation: <br /> Q=51(7)0.5 <br /> Where Q=loading rate(gal/day/ft'). <br /> T=Percolation Rate(min/in). <br /> Assumptions: <br /> 1) Shallow percolation rate is less than or equal to 250 minutes per inch. <br /> (250 minutes per inch is an estimate of the percolation rate for the septic field). <br /> 2) Three(3)feet of absorption area per linear foot of leach field trench. <br /> (6-inches each side and 2 feet along the bottom width). <br /> 3) An average daily flow of 375 gallons per day(5 people per day utilizing 75 gallons <br /> per day per person). <br /> The leach field size was calculated to handle all the flow with no contribution from the seepage <br /> pits. The SJC PHS-EHD Sewage Standards requires at least 60%of the septic system to be leach lines. <br /> The system calculations are presented on Sheet No. 1. Essentially,the proposed leach line sizes <br /> are based on approximately 375 gpd flow, a percolation rate of 125 min/in, and 3 feet of absorption area <br /> per foot of shallow trench, and will require a minimum of 280 feet of leach line. Three(3) leach lines of <br /> 95 feet each could be utilized. Please see the attached sheets for field data, basic equations,variables, <br /> calculations,and assumptions. <br /> Seepage Pits: <br /> Seepage pits should be attached to the end of each of the three(3) leach lines. We recommend <br /> that each seepage pit should be a minimum of 42-inches in diameter and 25 feet deep. Washed gravel <br /> should be placed inside the pits. Each 42-inch diameter by 25-foot deep seepage pit is estimated to store <br /> 594 gallons(assuming a porosity of 33%). We believe the absorption capacity of the seepage pits will be <br /> limited in this area. The seepage pits are an important part of the system because not only do they <br /> provide limited absorption capacity,they also provide system storativity during high peak usage. <br /> yFR dpi <br /> 4 <br /> e'�n <br />