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LUCCA WINERY SOIL SUITABILITY & NITRATE LOADING STUDY MAY 2013 IV. WASTEWATER DISPOSAL SYSTEM OPERATIONAL PARAMETERS A. Septic Tank Sizing The influent from the proposed restroom will flow by gravity flow into a minimum 1,200 gallon septic tank (per EHD design standard 6.1.14) that is installed at grade. The effluent can then gravity flow from the tank into the disposal area structure. The EHD will require that two-to-three inches of soil is placed over the tank to mitigate odors. The tank may have to be pumped on a prescribed interval basis depending on direct observations of paper and scum accumulation; e.g., every six months to every three years, depending on sludge/scum accumulation to be determined by a septic system contractor. Peaking factors for septic tanks vary with usage during the hour of the day, and day of the week, with peak hourly rates associated with normal working hours. The ratio of the peak day to the average day can vary from 1 .5 to >5, depending upon the usage. A peaking factor of 2.5 (average between 0 and 5) will be used in the calculation below: i. Septic Tank Hydraulic Detention Time Currently, it is estimated that the proposed septic system will handle both the Phase I and Phase II facilities septic demands. The following is the determination of the suitability of the proposed septic tank. Detention Time = 1,200 gal (min) septic tank capacity x 0.70 (30% volume lost to sludge/scum accumulation)/(2.5 (Peaking Factor) x 126 gals/day ADF) Detention Time = 2.7 days. The minimum acceptable detention time is 1 .0 days. Therefore, a 1,200 gallon septic tank is adequate for the restroom facility. ii. Primary and 100% Replacement Leach Line for the New Restroom The Lineal Feet of Leachline (LFLL) is calculated in the procedure described in Section 8.7 of the San Joaquin County Sewage Standards and EHD Document 42-01-004 Calculation Requirements for Commercial Septic Systems: Base Tank Capacity (BTC) = 1 ,200gals Lineal Feet of Leachline (LFLL) = (1 ,200 BTC + 126 ADF) x 0.200 Soil Factor based on the perc test results indicating a sandy loam soil at 36 inches below grade where the soil-effluent interface will occur = 265 LFLL or 3 - 90 ft leachlines can be installed. The leachfield disposal area has sufficient area for both the primary disposal areas and the 100% replacement areas. Page 113