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Denitrification Reductions Denitrification is a process that occurs in the septic system drain field whereby certain bacteria metabolize the oxygen in nitrate (NO3) in the waste water and release nitrogen gas(N2)to the atmosphere. Due to the biologic processes in the shallow soils, nitrogen in the drain field may undergo a reduction between 10 percent to 35 percent. Soils with higher clay content, moist soil conditions, high pH, and organic material denitrify by about 35 percent, and soils with high sand content and fast percolation rates tend t9,de itrify at a lower rate of about 10 percent. For purposes of this study, a denitrification factor f 10 pert nt was used, as soils in the area have significant sand content. Nitrate Loading Estimate A nitrate loading analysis was performed to determine the impact of on-site sewage disposal from the project on local ground water. The analysis uses assumptions as discussed. Table 1 provides a summary of assumptions used for the nitrate loading calculations. Amore detailed review of assumptions and calculations is provided in Figure 3. Table 1-Assumptions for Nitrate Loading Calculation Variable Value Units Description Q 4,900 gpd Sewage effluent flow rate Nw 70 mg/L-N Effluent nitrogen concentration A 46.42 acres Site area Nb 1.0 mg/L-N Concentration of rain d 10% unitless Denitrification factor // R 8.25 75r � // h�cs 7 i orches per year ' Deep percolation of rain water W 2 9.85 x 10-3 inches per year Uniform waste water loading for calculation The results of the nitrate loading, or long term average concentration of percolating effluent, Nc, as calculated using the Hantzsche and Finnemore equation,are presented in Table 2. Table 2. Result of Nitrate Loading Calculation Variable Value Units Description Nc 1.62 mg/L-N Long-term average concentration of percolating LBA Nitrate Loading Study/Jan 2017 pg. 5