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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 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. <br /> The following table presents a summary of the assumptions for the nitrate loading <br /> calculation for the homesite parcel of the Site, as presented in Plate 17. <br /> Table 3. Assumptions for Nitrate Loading Calculation, No Development <br /> Variable Value Units Description <br /> Q 450 gpd Effluent flow rate <br /> Nw 35 mg/L-N Effluent stream concentration <br /> A 2.11 acres Site area, homesite parcel <br /> Nb 0.27 mg/L-N Concentration of rain <br /> d 0.35 constant Denitrification factor <br /> R 5.54 inches per year Recharge rate of rainfall <br /> W 2.9 inches per year Uniform waste water loading (calculated) <br /> The details of the nitrate loading calculations are included in Plate 17. The results of the <br /> calculation are presented in the following table. <br /> LOGE 20-12 Page 13 <br />