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Table 4. Average Daily Flow Calculation <br />Use Units Rate Subtotal Reduction Average Daily <br />Flow <br />Employees, <br />winter and <br />summer <br />9 13 gal/employee 117 gpd 5/7, 183/365 41.9 gpd <br />Customers, <br />winter and <br />summer <br />1 5 gal/customer 5 gpd 5/7, 183/365 1.8 gpd <br />Employees, <br />spring 15 13 gal/employee 195 gpd 16/8, 6/7, <br />91/365 83.3 gpd <br />Customers, <br />spring 5 5 gal/customer 25 gpd 6/7, 91/365 5.3 gpd <br />Employees, <br />fall 20 13 gal/employee 260 gpd 12/8, 6/7, <br />91/365 83.3 gpd <br />Customers, <br />fall 10 5 gal/customer 50 gpd 6/7, 91/365 10.7 gpd <br />Cherry season <br />employees <br />35 13 gal/employee 455 gpd 40/365 49.9 gpd <br />Total 276.2 gpd <br />Reduction factors convert calculated flow into average daily <br />usual work shifts; 5/7 and 6/7 convert for days of operation <br />days per year. <br />The nitrate as nitrogen (N) concentration <br />estimated to be 85 mg/L (US EPA, 1980). <br />Den itrification Reductions <br />flow over a year: 16/8 and 12/8 <br />per week; and 183/365, 91/365, <br />of the employee and <br />convert for longer than <br />and 40/365 convert for <br />customer use is <br /> <br />Denitrification is a process that occurs in the septic system drain field whereby certain <br />bacteria oxidize the nitrate (NO3) in the wastewater and release nitrogen gas (N2) to the <br />atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain <br />field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay <br />content, moist soil conditions, high pH, and organic material denitrify by about 35 <br />percent, and soils with high sand content tend to denitrify at a lower rate of about 10 <br />percent. <br />A denitrification factor of 25 percent was selected for the Site because of the mixed silt <br />and sand present at the percolation test location. <br />LOGE 20-33 Page 13