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• 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 and fast percolation rates tend to denitrify at a <br /> lower rate of about 10 percent. <br /> A denitrification factor of 20 percent was selected for the Site because the soils <br /> examined were a combination of silt and sand. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to determine the impact from the existing and <br /> proposed facilities to ground water. The scenario utilizes the variables discussed <br /> previously, which represent the estimated conditions and uses associated with this <br /> project. The following table presents a summary of the assumptions for the nitrate <br /> loading calculation for the Site, as presented in Plate 16. <br /> Table 7. Assumptions for Nitrate Loading Calculation <br /> • Variable Value Units Description <br /> Q 9,651.8 gpd Effluent flow rate <br /> Nw 63.2 mg/L-N Effluent stream concentration <br /> A 272.55 acres Site area <br /> Nb 1.00 mg/L-N Concentration of rain <br /> d 0.20 constant Denitrification factor <br /> R 8.26 inches per year Deep percolation of rain water <br /> W 0.48 inches per year Uniform waste water loading for calculation <br /> • LOGE 1714 Page 18 <br />