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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 standard denitrification factor of 25 percent was selected for the Site because of the <br /> silty nature of the soil in the proposed septic system location. <br /> Nitrate Loading Estimate <br /> A nitrate loading scenario was employed to estimate the impact from the existing and <br /> proposed facilities to the 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 11. <br /> Table 5. Assumptions for Nitrate Loading Calculation <br /> • Variable Value Units Description <br /> Q 355.1 gpd Effluent flow rate <br /> Nw 45.6 mg/L-N Effluent stream concentration <br /> A 50 acres Site area <br /> Nb 1.00 mg/L-N Concentration of rain <br /> d 0.25 constant Denitrification factor <br /> R 12.9 inches per year Deep percolation of rain water <br /> W 0.10 inches per year Uniform waste water loading for calculation <br /> • LOGE 1841 Page 12 <br />