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Table 3. Average Daily Flow Calculation <br /> Use Units Rate Subtotal Reduction Average Daily <br /> Flow <br /> Employees 30 13 gal/employee 390 gpd 5/7 278.6 gpd <br /> Customers 3 3 gal/customer 9 gal 5/7 6.4 gal <br /> Total 285 gpd <br /> Reduction factors convert calculated flow into average daily flow over a year: 5/7 converts for days of operation per <br /> week. <br /> The nitrate as nitrogen (N) concentration of the employee and customer use is <br /> estimated to be 85 mg/L (US EPA, 1980). <br /> Denitrification Reductions <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 35 percent was selected for the Site because of the clayey soil <br /> present at the percolation test location. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to determine the impact from the proposed <br /> project to ground water. The scenario utilizes the variables discussed previously, which <br /> represent the estimated conditions and uses associated with this project. The following <br /> table presents a summary of the assumptions for the nitrate loading calculation for the <br /> Site, as presented in Plate 16. <br /> LOGE 20-24 Page 13 <br />