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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 (Hantzsche and Finnemore, 1992) was selected for <br />the Site because of the clay content of the soil 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. The following <br />table presents a summary of the assumptions for the nitrate loading calculation for the <br />Site, as presented in Plate 16. <br />Table 3. Assumptions for Nitrate Loading Calculation <br />Variable Value Units Description <br />840 gpd Effluent flow rate <br />Nw 35 mg/L-N Effluent stream concentration <br />A 2.66 acres Site area <br />Nb 0.3 mg/L-N Concentration of rain . <br />0.35 constant Denitrification factor <br />12.60 inches per year Recharge rate of rainfall <br />4.2 inches per year Uniform waste water loading (calculated) <br />The details of the nitrate loading calculation are included in Plate 16. The results of the <br />calculation are presented in the following table: <br />LOGE 1850 Page 12