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Table 4. Weighted Average Concentration Calculation <br /> Use Average Daily Estimated Waste Weighted Average <br /> Flow Water Quality Product <br /> Residences 350 gpd 35 mg/L-N 12,250 gpd-mg/L-N <br /> Employees 4.3 gpd 85 mg/L-N 365.5 gpd-mg/L-N <br /> Totals 354.3 gpd 12,615.5 gpd-mg/L-N <br /> Weighted Average 12,615.5 gpd-mg/L-N / 354.3 gpd = 35.6 mg/L-N <br /> Concentration: <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 and indicated in the drilling log for the domestic <br /> well. <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 15. <br /> LOGE 20-63 Page 13 <br />