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Mr.Carlos Murillo September 17,2002 Page 3 Ix. Design Calculations We understand the system should serve the needs of four(4) employees. Wastewater use is estimated to be 15 gallons per day (gpd) per person. The estimated average daily flow(ADF) for the site is 60 gallons per day. 4 employees x 15 gpd/person =60 gpd (ADF) Septic Tank: According to the San Joaquin County Public Health Services, Environmental Health Division's Sewage Standards (1996), the base tank capacity (BTC) for commercial systems is 1,200 gallons. The calculated tank capacity (CTC) is the sum of the BTC and the ADF. The calculated tank capacity is 1,260 gallons,therefore, the next available tank size would 1,600 gallons. See the following equation. 1,200 (BTC) +60 (ADF) = 1,260 (CTC) Utilizing the existing 1,200 gallon tank capacity for the new system was not acceptable to the San Joaquin County Environmental Health office. Leach Lines: According to the San Joaquin County Environmental Health Sewage Standards(1996), the required leach line length was determined by multiplying the CTC by the selected soil factor (SF) of 0.250 which reflects the clayey shallow soils of the area. The calculation results in 315 feet of total leach line(LL). The Sewage Standards allows for up to 60%of this length to be used for leach line with the reminding 40%to be used for seepage pit equivalent. Therefore, about 189 feet of leach line should be installed. According to the San Joaquin County Environmental Health Sewage Standards (1996), a 36-inch diameter by 25-foot deep seepage pit is equivalent to 70 feet of leach line. The septic system sizing calculations are summarized in the following table. 1,260 gal (CTC) x 0.250 (SF) =315 ft(LL) 60% x 315 ft= 189 feet LL, 60% of system in LL Round down, use 180 ft for leach tine Use two (2), 36-in dia. seepage pits Two (2), 36-in dia. pits x 70 ft per pit equivalent LL = 140 ft LL equivalent 140 ft LL equivalent in seepage pits + 180 ft LL=320 ft LL p't�A