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Table 5. Weighted Average Concentration Calculation <br />Use Average Daily Estimated Waste Weighted Average <br />Flow Water Quality Product <br />Residence 100 gpd 35 mg/L-N 3,500 gpd-mg/L-N <br />Employees 41.8 gpd 85 mg/L-N 3,553 gpd-mg/L-N <br />Customers 178.6 85 mg/L-N 15,181 gpd-mg/L-N <br />Totals 320.4 gpd 22,234 gpd-mg/L-N <br />Weighted Average 22,234 gpd-mg/L-N / 320.4 gpd = 69.4 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 typical denitrification factor of 25 percent was selected for the Site because of the silty <br />sand sand soil type present at the percolation test location. <br />Nitrate Loadina 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 14. <br />LOGE 2142 Page 13 <br />